5th Annual Report of the Stanford Environmental Molecular Science Institute: A Focus on Chemical and Microbial Processes at

Environmental InterfacesAugust 16, 2009

Gordon E. Brown, Jr.1,2,3, Anders Nilsson2, Alfred M. Spormann3, Karim Benzerara4, Hendrik Bluhm5, Bryan A. Brown6, Georges Calas4, Anne M. Chaka7, Brent R. Constantz8, Francois Farges9, Scott E. Fendorf 1, Andrea L. Foster10, Farid Juillot4, Guillaume Morin4, Satish C.B. Myneni11, Georges Ona-Nguema4, Lars G.M. Pettersson12, Kevin M. Rosso13,

James J. Rytuba10, Miquel Salmeron14, Jennifer Saltzman15, Mark P. Taylor16, Thomas P. Trainor17, and Jennifer Wilcox18

1Dept. of Geological & Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA2Dept. of Photon Science and Stanford Synchrotron Radiation Lightsource, 2575 Sand Hill Road, SLAC

National Accelerator Laboratory, MS 69, Menlo Park, CA 94025, USA3Dept. of Chemical Engineering, Stanford University, Stanford, CA 94305, USA

4Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC) - UMR 7590 - CNRS – Université Paris 6 & 7 - IPGP, 140, rue de Lourmel, 75015 Paris, France

5Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA6School of Education, Stanford University, Stanford, CA 94305, USA

7Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA8Calera Corporation, 100A Albright Way, Los Gatos, CA 95032, USA

9Muséum National d'Histoire Naturelle, USM 201 and CNRS UMR 7160, Paris, France

10Geologic Division, U.S. Geological Survey, 345 Middlefield Road, MS 91, Menlo Park, CA 94025, USA

11Dept. of Geosciences, Princeton University, Princeton, NJ 08540, USA12FYSIKUM, Stockholm University, Albanova University Center, S-10691 Stockholm, Sweden

13W.R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA

14Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA15School of Earth Sciences, Stanford University, Stanford, CA 94305, USA

16Science & Technology Division, Corning Incorporated, Sullivan Park DV-01-9, Corning, NY 14831, USA

17Dept. of Chemistry and Biochemistry, University of Alaska, Fairbanks, AK 99775-6160, USA18Dept. of Energy Resources Engineering, Stanford University, Stanford, CA 94305, USA

I. GOALS, ORGANIZATIONAL STRUCTURE, ACTIVITIES, AND RESEARCH HIGHLIGHTS

The Stanford Environmental Molecular Science Institute (EMSI) is completing its fifth year of operation and continues to pursue fundamental and applied studies of chemical and microbial processes at complex environmental interfaces. The Stanford EMSI was founded in September 2004 as a multidisciplinary, multi-institutional, multi-investigator research, graduate training, and education/outreach program funded by the NSF Chemistry Division, with additional funding from the NSF Earth Sciences Division and the DOE Biological & Environmental Research Division through their Environmental Remediation Science Program.

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Goals – The overall goals of the Stanford EMSI are to (1) develop a quantitative molecular-level understanding of chemical and biological processes occurring at environmental interfaces and how they affect contaminant and pollutant speciation, toxicity, mobility, and potential bioavailability; (2) explore how such interactions studied in the laboratory relate to the complexity found in natural environments; (3) provide platforms for new approaches to address environmental challenges involving contaminants; (4) recruit a diverse group of qualified graduate, undergraduate, and post-doctoral students; (5) create a stimulating multidisciplinary research/learning environment in which students and post-Ph.D. participants can tackle complex systems and questions relevant to problems in environmental chemistry, ranging from molecular to field scales; and (6) effectively disseminate our research results and approach to the broader public and to future generations of scientists, engineers, and policy makers and to engage K-12 science teachers in current topics in environmental chemistry. As the remainder of this report will show, we are addressing each of these goals.

Organizational Structure – The Stanford EMSI team includes 24 senior investigators from three countries (USA, France, and Sweden,), six universities (Stanford University, University of Alaska-Fairbanks, Princeton University, University of Paris VI, University of Paris VII, and Stockholm University, Sweden), three U.S. national laboratories (SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory, and Pacific Northwest National Laboratory), two U.S. government agencies (National Institute of Standards & Technology and U.S. Geological Survey), the French National Natural History Museum, and two U.S. technology companies (Corning, Inc. and Calera Corporation). Our team also includes about 40 graduate students, postdoctoral scholars, and undergraduate and high school interns. A listing of these participants for the 2008-2009 period can be found in Appendix C. The activities of the Stanford EMSI can be broken down into nine research areas, many of which have strong cross-links. They are [with SEMSI senior investigators listed after each area in which they are involved] (A) Structural Studies of Bulk Water [Anders Nilsson (SSRL) and Lars G. M. Pettersson (Stockholm University)]; (B) Interaction of Water with Environmental Substrates [Hendrik Bluhm (LBNL), Gordon Brown (Stanford University and SSRL), Anne Chaka (NIST), Nilsson, Pettersson, Kevin Rosso (PNNL), and Miquel Salmeron (LBNL)]; (C) Structure of Metal Complexes in Aqueous Solutions [Myneni, Chaka, and Nilsson]; (D) Structure and Reactivity of Hydrated Metal Oxide Surfaces [Tom Trainor (University of Alaska, Fairbanks), Bluhm, Brown, Chaka, Rosso, Salmeron, and Michael Toney (SSRL)]; (E) Sorption Processes at Solid-Aqueous, Microprobe-Aqueous, and Solid-Biofilm Interfaces and Biomineralization [Brown, Brent Constantz (Calera Corporation); Francois Farges (Muséum National d'Histoire Naturelle, France), Scott Fendorf (Stanford University), Andrea Foster (U.S. Geological Survey), Satish Myneni (Princeton University), Alfred Spormann (Stanford University), Mark Taylor (Corning, Inc.), Trainor]; (F) Theoretical Modeling of Solid-Aqueous Solution Interfaces and Interfacial Reactions [Chaka, Nilsson, Pettersson, Rosso, Trainor, Brown, and Jennifer Wilcox (Stanford University)]; (G) Dynamics in Biofilms at Solid-Aqueous Solution Interfaces, and Molecular Genomics and Biofilm Physiology [Spormann, Brown, Fendorf, and Rosso]; (H) Environmental Applications [Fendorf, Brown, Georges Calas (University of Paris VI), Foster, Farid Juillot (University of Paris VII), Guillaume Morin (University of Paris VI), Myneni, James J. Rytuba (US Geological Survey), Spormann, and Trainor]; (I) New Experimental Developments in Synchrotron Radiation-Based Spectroscopies and Micro-Imaging [Nilsson, Bluhm, and Salmeron].

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In addition to the research areas listed above, the Stanford EMSI has strong education and outreach components led by Dr. Jennifer Saltzman, Educational Outreach Coordinator for the Stanford School of Earth Sciences and the Stanford EMSI, and Prof. Bryan Brown, Assistant Professor, Stanford School of Education and Stanford EMSI Educational Outreach Supervisor. We have organized and run four four-day summer workshops for high school science teachers with a focus on the environmental chemistry of mercury, including a workshop on July 22-25, 2009, which is discussed in section III.A.2. The Stanford EMSI has also run three science journalist workshops over the past three years with a focus on the environmental chemistry of arsenic and mercury, including a workshop on October 24, 2008. We also co-organized and sponsored the 6th annual Stanford-Berkeley Summer School on Applications of Synchrotron Radiation in the Physical Sciences on August 18-22, 2008 at Stanford University. In addition, we have summer intern programs for high school students and college undergraduates at Stanford and our partner institutions (University of Alaska, Fairbanks and Princeton University).

The 4th annual meeting of the Stanford EMSI was held at Stanford University on August 25-26, 2008 and was attended by 42 SEMSI members, four members of the SEMSI External Advisory Committee (Prof. George R. Helz, Chair (Dept. of Chemistry, University of Maryland), Dr. Brent Constantz (Calera Corporation, Los Gatos, CA), Dr. Yuri Gorby (J. Craig Venter Institute, San Diego, CA), and Dr. David Shuh (Chemical Sciences Division, Lawrence Berkeley National Laboratory)), and three guests (Dr. John Bargar (SSRL), Prof. Rossitza Pentcheva and Ms. Katrin Otte (University of Munich)). The meeting consisted of 19 oral and 17 poster presentations as well as a general session in which members of the research areas listed above discussed research needs and opportunities. A copy of the 4 th Annual Stanford EMSI Meeting Program with Abstracts can be found in Appendix D. In place of the annual meeting this year, we will hold a special workshop at Stanford University for selected senior investigators in early September 2009 at which we will prepare a review article for submission to Chemical Reviews that will focus on progress made in the area of chemical and biological interactions at environmental interfaces over the past decade. This review article is intended to update a 1999 Chemical Reviews article entitled “Metal oxide surfaces and their interactions with aqueous solutions and microbial organisms” (Brown et al., Chem. Rev. 1999, 99, 77-174), which has been cited 325 times since its publication.

Research Highlights – Selected highlights of Stanford EMSI-funded research include the following: (1) x-ray spectroscopic and x-ray scattering studies of water under ambient conditions have led to the proposal of a new structure of water involving a fluctuating equilibrium between low density and high density regions in the water structure with different types of H-bonding and a new understanding of the “structure-making” and “structure-breaking” role of cations of different valence in water; (2) the first ambient pressure x-ray photoelectron spectroscopy studies of the interaction of water with metal oxide surfaces under in situ, near-ambient conditions have led to new understanding of hydroxylation of these surfaces involving cooperative effects among adjacent water molecules; (3) the first ambient pressure XPS studies of the structuring of water on Cu surfaces explains the very different wetting properties of Cu(110) and Cu(111) surfaces; (4) theoretical studies of the dissociation of water in the presence of Cr3+ and Fe3+ ions show the importance of dynamical effects involving Zundel and Eigen proton complex formation; (5) theoretical studies of the structure of hydrated Fe-oxide surfaces and their interaction with water and aqueous Pb(II) ions explain why aqueous Pb(II) forms stronger chemical bonds to the a-Fe2O3 (0001) surface rather than the a-Al2O3 (0001) surface; (6) crystal truncation rod diffraction

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studies of hydrated iron oxide surfaces have provided the first details about the surface structures of these important environmental substrates and show how Fe(II) adsorbs on the (0001) and (1-102) hematite surfaces where it behaves as Fe(III) but still acts as a powerful reductant; (7) total x-ray scattering, thermogravimetric analyses, and magnetic susceptibility studies of ferrihydrite aged at 175°C in the presence of citrate have resulted in the discovery of a new ordered ferrihydrite phase intermediate between disordered ferrihydrite and hematite, confirmation of the controversial structure of disordered ferrihydrite proposed by Michel et al. in 2007, new understanding of the defect structure of ferrihydrite, a new chemical formula for the disordered and ordered ferrihydrite phases, and an explanation of the ferromagnetic properties of ordered ferrihydrite; (8) spectroscopic, quantum chemical, and surface complexation studies of the interaction of environmentally common carboxylic acids (oxalic, maleaic, malonic, and lactic) and humic acid with Al-(oxyhydr)oxide nanoparticles that have helped elucidate reasons for differences in solid dissolution caused by different acids; (9) x-ray spectroscopic studies of the interactions of aqueous arsenite and arsenate with iron (oxyhydr)oxide surfaces have resulted in new molecular-level models for the sequestration of As(III) and As(V) on these common environmental substrates; (10) x-ray and FTIR spectroscopic studies of the interaction of aqueous Zn(II) and oxalate with hematite nanoparticle and microparticle surfaces showed major differences in sorbate structure and shed new light on reasons for differences in reactivity of hematite particles of different size; (11) long-period x-ray standing wave studies of the partitioning of aqueous Pb(II), Zn(II), and As(V) on oriented single crystal surfaces of a-Fe2O3

and a-Al2O3 coated by organic polymers and Shewanella oneidensis biofilms show that there are significant differences in the binding of different ions on the metal oxide surfaces and in the microbial biofilms; (12) a major advance was made in quantifying x-ray fluorescence intensities from long-period XSW measurements with respect to element partitioning between phases; (13) studies of the speciation, transformation, and cycling of arsenic in various contaminated field settings, including France, Bangladesh, and Cambodia, show that the long-held model of As(V) release from iron oxide particles is not as simple as previously believed; (14) studies of the speciation, transformations, and cycling of mercury in mercury mining environments in the California Coast Range led to new models that help explain the atmospheric evasion of Hg(0) from these deposits and the release of Hg(II) from microbially enhanced dissolution of HgS solids; (15) development and application of a new scanning transmission x-ray microscopy (STXM) beamline at the Advanced Light Source led to new understanding of microbial weathering and calcification as well as the behavior of arsenic in acid mine drainage environments; and (16) development of a new ambient pressure XPS spectrometer at SSRL that will extend the water pressure range that can be explored in equilibrium with oxide surfaces.

The research efforts of the Stanford EMSI over the past five years have resulted in 180 papers published or in press in peer-reviewed scientific journals, conference proceedings, or research monographs. A list of these publications can be found in Appendix A. A breakdown of publications in terms of type of journal is given below.• chemistry (ACS and IUPAC) journals and conference proceedings – 75 (42%)• geochemistry/mineralogy journals and conference proceedings – 41 (23%) • physics journals and conference proceedings – 22 (12%)• high impact journals (Science, Nature, Phys. Rev. Lett., PNAS) – 9 (5%)• microbiology/geobiology journals – 8 (5%)• surface science journals – 8 (5%) • surface chemistry and agronomy monographs – 8 (5%)

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Figure 1. O 1s XAS spectra of NaCl solutions with increasing concentration measured in the transmission mode, compared with the spectrum of pure water. The difference spectra are shown at the top of the figure.

• materials science/glass science journals – 4 (2%) • environmental science journals (other than ES&T) and conference proceedings – 2 (1%)• medical journals – 1 (0.5%)

In addition, 23 manuscripts have been submitted to peer-reviewed journals during the past year. A listing of these manuscripts can also be found in Appendix A (section b). Members of the Stanford EMSI have presented over 250 keynote addresses, invited talks, contributed talks, and posters at international and national meetings during the period Sept. 2004-June 2009. A listing of these presentations can be found in Appendix B.

II. SUMMARY OF SELECTED RESEARCH RESULTS (July 2008 – July 2009)(Names of senior EMSI investigators are in bold-face type, names of students and post-docs are underlined)

A. Structural Studies of Bulk Water

1. Density fluctuations and local structures in aqueous solutions from x-ray spectroscopy and x-ray scattering measurements (Ira Waluyo, Congcong Huang, Dennis Nordlund, Uwe Bergmann, Lars G. M. Pettersson, and Anders Nilsson)

Ions in aqueous solutions are traditionally categorized into structure breakers and structure makers based on the strength of their interaction with water [1]. However, this classification is ambiguous and based on macroscopic properties, offering no structural details of the water-ion interaction. X-ray absorption spectroscopy (XAS) is a powerful tool for studying the nature of the interaction between water molecules and ions due to its elemental specificity and sensitivity to the orbitals involved in hydrogen-bonding [2]. In addition, small angle x-ray scattering (SAXS) can be used as a probe for density variations or fluctuations in a liquid [3]. Here we present our recent data on the structure of water in aqueous solutions with increasing cation valency, i.e. NaCl, MgCl2, and AlCl3, within the framework of the model of water as a mixture of low density liquid (LDL) and high density liquid (HDL) [3] (see Appendix F).

XAS measurements of NaCl solutions at 1, 2, 4, and 6 molal concentrations in transmission mode were performed at SSRL on BL 10-1, where a ~300 nm thick liquid sample was contained between two Si3N4 windows. MgCl2 solutions (1 and 4 molal) were measured at SSRL on BL 6-2 using x-ray Raman scattering (XRS), a hard x-ray equivalent of soft x-ray XAS measurements in which a high energy x-ray photon (~7 keV) is inelastically scattered and a small fraction of the energy is used to excite a core-electron to an unoccupied orbital in an x-ray absorption process. SAXS measurements of all solutions were performed at SSRL on BL 4-2.

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Figure 3. SAXS data for 0.5 m NaCl, MgCl2, and AlCl3 compared with pure water, all measured at 25°C.

Figure 2. O 1s XA spectra of 1m and 4m MgCl2 solutions measured by XRS, comp ared with the spectrum of pure water. The difference spectra are shown at the top of the figure.

Figure 1 shows O1s XAS spectra of the NaCl solutions compared with that of pure water. Increasing the salt concentration has an effect similar to that of increasing temperature [2,3] or pressure, i.e. increased pre- and main-edge and decreased post-edge, indicating the presence of more HDL structure compared to pure water. By contrast the O1s XRS spectra of MgCl2 solutions show no such spectral changes (Figure 2). At high concentration (4 molal), where all water molecules are in the ion hydration shell, a shift to higher energy is observed, associated with shorter (stronger) H-bonds [4]. At a lower concentration (1 molal), no change is observed from pure water, indicating that the free water molecules (i.e. water not in hydration shells) must contain more HDL species. Therefore, the opposite effects from free water and water in hydration shell cancel each other, giving rise to a spectrum similar to that of pure water. Similar but more dramatic spectral changes have been observed for AlCl3 solutions [5].

We used SAXS to understand the role of ions and hydration shells in the density fluctuations of water. Figure 3 compares the SAXS data for NaCl, MgCl2 and AlCl3 solutions at 0.5 molal with that of pure water. The scattering curve for NaCl resembles that of pure water, indicating that there are no additional structures besides those of HDL and LDL in bulk water. Therefore, although the Na+ ion is often considered as a local structure maker with tightly bound water in its hydration shell [6], we observe no such stable structure of ion and hydration shell. It is likely that the water molecules bound to the ions are easily exchanged with free water molecules.

In

contrast, the scattering curves for MgCl2 and AlCl3 solutions show enhancements that likely arise from stable hydration shells around ions. The absence of such enhancement in the 0.5m NaCl solution led us to conclude that the Mg2+

and Al3+ cations are mainly responsible for the enhancements. The significantly more dramatic increase in intensity at lower Q for the 0.5 m AlCl3 solution indicates that Al3+ has a more extended hydration shell compared to Mg2+. The presence of these intensity enhancements even at low concentrations shows that the water molecules in the hydration shells of Mg2+ and Al3+

are tightly bonded, have different properties than free water, and are not involved in the density fluctuation that occurs in bulk water.

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Based on our data, we categorize Na+ as a structure-breaker, where more HDL structure is observed and the water molecules in the hydration shell are easily exchanged with free water. On the other hand, Mg2+ and Al3+ are classified as local structure makers, where, although more HDL structure is formed, the water molecules in the hydration shell are so tightly bound that they are not involved in the density fluctuations of the free water.

References[1] Marcus, Y. Chem. Rev. 2009, 109, 1346-1370.[2] Wernet, P.; Nordlund, D.; Bergmann, U.; Cavalleri, M.; Odelius, M.; Ogasawara, H.;

Naslund, L. A.; Hirsch, T. K.; Ojamae, L.; Glatzel, P.; Pettersson, L. G. M.; Nilsson, A. Science 2004, 304, 995-999.

[3] Huang, C., K. T. Wikfeldt, T. Tokushima, D. Nordland, Y. Harada, U. Bergmann, M. Niebuhr, T. M. Weiss, Y. Horikawa, M. Leetmaa, M. P., Ljungberg, O. Takahashi, A. Lenz, L. Ojamäe, A. P. Lyubartsev, S. Shin, L. G. M. Pettersson, and A. Nilsson, Proc. Nat. Acad. Sci. USA 2009, 106. (See http://home.slac.stanford.edu/pressreleases/2009/20090811.htm)

[4] Odelius, M.; Cavalleri, M.; Nilsson, A.; Pettersson, L. G. M. Phys. Rev. B 2006, 73, 024205.[5] Naslund, L. A.; Edwards, D. C.; Wernet, P.; Bergmann, U.; Ogasawara, H.; Pettersson, L. G.

M.; Myneni, S.; Nilsson, A. J. Phys. Chem. A 2005, 109, 5995-6002.[6] Mancinelli, R.; Botti, A.; Bruni, F.; Ricci, M. A.; Soper, A. K. J. Phys. Chem. B 2007, 111,

13570-13577.

2. The interaction of acetonitrile and water (Ningdong Huang, Congcong Huang, Dennis Nordlund, Uwe Bergmann, and Anders Nilsson)

Acetonitrile aqueous solutions are widely used in many fileds such as liquid chromatography, solvent extraction, organic synthesis, and electrochemistry and the environmental and health impacts of this solvent cannot be neglected [1]. The interaction between acetonitrile and water is of fundamental importance in this respect, particularly the change of the hydrogen bond network of water by addition of acetonitrile solutes. The O1s XAS of water molecules were measured and reveal dramatic changes as the concentration of acetonitrile (ACN) increases. At low concentration of 10 percent ACN by mole ratio, absorption intensity is redistributed from post edge to main edge and pre edge, accompanied by a shift of the latter as shown in Figure 4. This trend extends to the medium concentration of 50%, which shows structure-breaking effects due to the interaction between ACN and water molecules. The nitrogen 1s was also measured for pure and 10 % ACN as in (Fig. 4). The observation that the ratio of π* to σ* drops for ACN upon solvation may indicate hydrogen bonding between nitrogen in ACN and water molecules. At low water concentration, the XAS spectra indicate lack of hydrogen bonding, and mostly water monomers and dimers are observed. This change indicates that the water is fully solved in acetonitrile through a molecular interaction that is currently being studied with theoretical methods.

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Reference[1] Toshiyuki Takamuku, Masaaki Tabata, Atsushi Yamaguchi and Jun Nishimoto, J. Phys.

Chem. B 1998, 102, 8880-8888.

B. Interaction of Water with Environmental Substrates

1. Structure of water adsorbed on a BaF2 (111) surface in the supercooled regime (Sarp Kaya, Susumu Yamamoto, Tom Kendelewicz, Hendrik Bluhm, Gordon Brown, and Anders Nilsson)

Extensive research on the nature of water adsorbed on solid surfaces, from ultra-high vacuum conditions on clean and well-ordered crystal surfaces to ambient situations at room temperature, have highlighted the important role of the adsorbed layer in water-solid interactions,

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the properties of which are not relevant to bulk solid/liquid properties [1]. Deviations from bulk properties are usually linked to structural modifications.

Structural similarities with the basal plane of hexagonal ice (Ih) make the BaF2 (111) surface a promising candidate for epitaxial ice growth even though their interaction energy is relatively low. Amorphous and crystalline forms of ice can be prepared by condensing water vapor on cold substrates, which is a common UHV-based technique to study ice-substrate interactions [2]. However, less is known about the structure of water at ambient conditions where 2-3 monolayers of water accumulate in a relative humidity range between 50 to 100 %.

We have investigated the structure of water on BaF2 (111) surfaces at ambient conditions (P(max) = 1.5 torr, T=260-360 K) and in ultra high vacuum at cryogenic temperatures by utilizing X-ray absorption spectroscopy (XAS) at the oxygen K-edge. Local structural differences in the hydrogen-bonding network of water can be identified by XAS since the modifications in hydrogen bonding between water molecules result in characteristic spectral changes (Fig. 5). Ambient pressure XAS measurements were performed at the Advance Light Source on BL 11.0.2. Complementary UHV-based studies were performed at Stanford Synchrotron Radiation Lightsource on BL 13.2.

X-ray absorption spectra of crystalline ice have a

distinct post-edge feature (~540 eV) reflecting the fully coordinated hydrogen network of ice [3]. Ice formed by condensing water vapor at surface temperatures of 140 K and above is known to be cubic (Ic) and shows structural similarities to the Ih form of ice, which is the form of ice below the freezing point in the ambient pressure regime. A pronounced post-edge feature in XAS spectra of 4 ML of Ic ice at 150 K indicates that on the BaF2 (111) surface, four-fold hydrogen bonding requirements of crystalline ice are fulfilled. Below 140 K, amorphous solid water (ASW) can be formed thanks to the lower mobility of water molecules. Despite its amorphous nature, the XAS spectrum of ASW has a post-edge feature implying that water molecules are not fully uncoordinated (Fig. 5). However, it is clear that pre-edge (535 eV) and post-edge features shows fractional changes. These findings rule out the possibility that the structure of water on BaF2 (111) surfaces in the supercooled regime is like crystalline or amorphous ice forms since the pre-edge and post-edge regions of XAS spectra of water at 264 K (90 % RH) lack relevant spectral features. Based on

recent observations on liquid water [4], water on BaF2 (111) surfaces at ambient conditions can be considered as a high-density liquid, i.e. one of the structural phases present in the bimodal distribution picture of local water structures [4].

References[1] M.A. Henderson, Surf. Sci. Rep. 2002, 46, 5.

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Figure 5. O K-edge XAS spectra of adsorbed water. Ambient conditions (red), at 100 K (blue), and at 150 K (green).

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2 ML in 1.5 torr H 2O at 264 K 2 ML in UHV at 100 K (ASW) ~4 ML in UHV at 150 K (Ic)

[2] J. Vogt, J. Chem. Phys. 2007, 26, 244710.[3] Ph. Wernet et al., Science 2004, 304, 995.[4] C. Huang et al., Proc. Nat. Acad. Sci. USA 2009, 106 (Early Edition).

2. Photoemission study of the reaction of Fe3O4(100) with water at near-ambient conditions (Tom Kendelewicz, Sarp Kaya, John T. Newberg, Hendrik Bluhm, Anders Nilsson, Rossitza Pentcheva (University of Munch), Wolfgang Moritz (University of Munich), and Gordon E. Brown, Jr.)

Polar surfaces of magnetite are difficult to study at the atomic level due to major reconstructions, involving vacancy formation, charge redistribution and localization, and/or adsorption of ions. Understanding surface structure and stoichiometry is prerequisite for studies of adsorbate reactions including H2O. A great deal of attention has been paid to the (√2X√2)R45º surface, which exists on magnetite (100) under a range of preparation conditions. Only two terminations exist along [100]: one, referred to as A, contains a monolayer of tetrahedral Fe, FeT

3+, and the other, referred to as B, contains octahedral Fe, FeO2+ and FeO

3+, and all O-2 ions. Although initial studies related the (√2X√2)R45 surface to the A termination, with half of the FeT

3+ removed, newer data and theory support the B-like termination. We studied water reactions on the (√2X√2)R45º magnetite (100) surface using high-P core-level photoemission spectroscopy. Adsorption isotherms at 273 and 300 K using p(H2O) from 10-8 to 2 Torr and back to UHV showed a continuous increase in OH coverage with the largest change at 10-4 to 10-2 Torr (Fig. 6) Above 10-2 Torr, additional physisorbed molecular H2O was observed (Fig. 6). Upon evacuation, molecular H2O is reversibly removed from the surface, with only a marginal decrease of OH (Fig. 7). Based on a uniform layer model, we estimate maximum OH and H 2O coverages of 1 ML (Fig. 7), in agreement with DFT calculations, which indicates formation of a full layer of OH on an unreconstructed B-like termination.

Major conclusions of this study are: (1) Water reversibly adsorbs and desorbs from the magnetite (100) (√2x√2)R45 surface at ambient temperature with increasing and decreasing p(H2O), respectively. (2) Hydroxyl coverage increases strongly at a RH of 0.01% and saturates at around 1 monolayer coverage. (3) Most of the hydroxyl stays on the surface during evacuation. (4) Above ~10-2 Torr on hydroxylated surface a layer of weakly bound water develops. This layer is desorbed when vapor pressures is reduced. The chemical shift for water varies from 3.5 to 3.0 eV and coverage exceeds ~1 ML at RH ~ 40%. (5) These results demonstrate importance of the cooperative effects in water interaction with the magnetite surface.

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Figure 6. (left) O 1s XPS of water on the magnetite (Fe3O4) (100) surface at 23°C and various relative humidi-ties. The peak at 155 eV kinetic energy is the lattice oxygen peak, and the shoulder on the low-energy side of this peak is due to OH. The feature at 151.5 eV is physisorbed H2O, and the feature at 149.5 eV is H2O in the gas phase. (right) Monolayer (ML) coverage of Fe3O4

(100) by OH (red) and H2O (blue) as a function of RH.

Figure 7. Changes in OH (squares) and H2O (diamonds) coverages (in monolayers) on the magnetite (100) surface as a function of relative humidity (RH) at 23°C, showing isotherms with increasing RH (“up”: left panel) and decreasing RH (“down”: right panel).

3. Interaction of water with MgO(100) under near-ambient conditions (John T. Newberg, Sarp Kaya, Tom Kendelewicz, Miquel Salmeron, Anders Nilsson, Gordon E. Brown, Jr., and Hendrik Bluhm)

Under ambient conditions most surfaces are covered by a thin water layer, which determines such important properties as adhesion, friction, surface conductivity, and reactivity. The interaction of water with metal oxides is of particular interest due to their abundance in the environment and their use in industrial applications. Even though these systems have been extensively studied using vacuum-based surface science techniques, the nature of the water/oxide and water/metal interface under ambient conditions is still poorly understood. The latest generation ambient pressure X-ray photoelectron spectroscopy (AP XPS) instrument allows us to study surfaces at water vapor pressures of up to 5 Torr, i.e. at a relative humidity of up to 100% for a sample temperature of 1 ºC. We have used AP XPS to investigate fundamental questions of water adsorption on surfaces under near-ambient conditions, in particular the formation of hydroxyl groups at the surface and their role in the adsorption of molecular water on thin MgO(100)/Ag(100) films.

Results from a typical ambient pressure XPS isobar experiment are shown in Figure 8 for a 4 monolayer thick MgO(100)/Ag(100) film, taken initially under vacuum (dry) conditions, followed by exposure to 0.15 Torr water vapor under decreasing sample temperature conditions. Peaks due to oxide (Ox), hydroxide (OH), adsorbed water, and water vapor oxygens are well resolved in the O 1s spectra. As seen from the Ag 3d spectra, the silver substrate was unaffected by the water chemistry. Although much less resolved than the O 1s, the Mg 2p spectra also show evidence of surface OH formation under wet conditions.

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-0.2

0

0.2

0.4

0.6

0.8

1

1.2

10-7 10-5 0.001 0.1 10-0.2

0

0.2

0.4

0.6

0.8

1

1.2

10-7 10-5 0.001 0.1 10

RH(%)

“up” isotherms “down” isotherm

coverage (M

L)

RH(%)

Figure 7. Changes in OH (squares) and H2O (diamonds) coverages (in monolayers) on the magnetite (100) surface as a function of relative humidity (RH) at 23°C, showing isotherms with increasing RH (“up”: left panel) and decreasing RH (“down”: right panel).

Figure 8. Ambient pressure XPS O 1s, Ag 3d and Mg 2p spectra of a 4 ML thick MgO(100)/Ag(100) film exposed to a 0.15 Torr isobar under decreasing sample temperature conditions.

A multilayer model was developed for the quantification of OH and water coverages, and an example of the results is shown in Figure 9, where each data point is from an O 1s spectrum captured at a given relative humidity (RH). At low RH values, hydroxylation is only observed at defect sites, whereas above ~0.01% RH, rapid uptake occurs whereby the surface passivates with a monolayer of OH. Upon hydroxylation, there is a concomitant rise in the adsorbed molecular water. We have found that surface hydroxylation of water with MgO is very sensitive to both surface carbon contamination and increased X-ray exposures. In particular, carbonatious material adsorbed to the surface physically takes up surface sites such that hydroxylation does not occur at those sites. Increased X-ray exposure induces surface hydroxylation at RH << 0.01%, and the rise is more gradual than that seen in Figure 9. Great care was taken to reduce both of these factors in order to obtain a full understanding of the surface chemistry of water with MgO(100) and to produce results similar to those seen in Figure 9.

Figure 9. OH and H2O uptake for a 4 ML MgO(100) film during a 0.15 Torr isobar experiment under decreasing sample temperature conditions (300 to –10 C).

C. Sructure of Metal Complexes in Aqueous Solutions

See section II.A.1 – The X-ray Raman spectroscopy and small angle x-ray scattering study of bulk water under ambient conditions containing Na+, Mg2+, and Al3+ ions showed that Na+ ions act as “structure breakers” and that Mg2+ and Al3+ ions act as “structure makers” in aqueous solutions.

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D. Structure and Reactivity of Hydrated Metal Oxide Surfaces

1. Surface x-ray scattering studies of iron oxides (Thomas P. Trainor, Christopher C. Iceman, Sara C. Petitto, Kunaljeet S. Tanwar, Sanjeet K. Ghose, and Peter J. Eng)

A major component of the University of Alaska Fairbanks group’s SEMSI research is devoted to developing structural models of hydrated metal-oxide mineral surfaces and their interface with aqueous solutions. Our work is focused in particular on determining the structure of low-index faces of common iron-(hydr)oxide phases (hematite, goethite, and magnetite) utilizing synchrotron-based surface x-ray diffraction. Iron-oxides are of particular interest due to their widespread occurrence, typically high specific surface area, and high surface reactivity, making them important scavengers of aqueous trace metals, and substrates that support the heterogeneous transformation of aqueous contaminants. Our current efforts are focused on understanding how these geochemical interface systems are modified by variations in common geochemical variables, including: (i) the influence of water on surface structure, (ii) the surface structure modification associated with the changes in redox potential of aqueous solutions, and (iii) the resulting changes in surface reactivity with respect to aqueous metal ion adsorption. The experimental models developed from surface x-ray scattering methods are used in direct comparison with the results of periodic density functional theory and ab initio thermodynamic calculations to provide a detailed interpretation of the energetics of the systems under investigation. Over the past year, our interface studies have mainly focused on two systems: (i) modification of the hematite (0001) surface during reaction with aqueous Fe(II) under anoxic conditions and (ii) the structure of the magnetite (111) surface under variable redox conditions.

The surface structure of a-Fe2O3(0001) was studied using crystal truncation rod (CTR) X-ray diffraction before and after reaction with aqueous Fe(II) at pH 5 [1]. The CTR results show the unreacted a-Fe2O3(0001) surface consists of two chemically distinct structural domains: an O-layer terminated domain and a hydroxylated Fe-layer terminated domain. These domains have distinct coordination chemistry and, therefore, likely have distinct differences in overall reactivity. After exposing the a-Fe2O3(0001) surface to aqueous Fe(II), the surface structure of both co-existing structural domains was modified due to adsorption of Fe at crystallographic lattice sites of the substrate. In both domains the adsorbed iron was found to be in six-fold coordination with surface (hydr)oxo groups. The average Fe-O bond lengths of the adsorbed Fe are consistent with typical Fe(III)-O bond lengths (in octahedral coordination), providing evidence for the oxidation of Fe(II) to Fe(III) upon adsorption. These results highlight the important role of substrate surface structure in controlling Fe(II) adsorption. Furthermore, the molecular-scale structural characterization of adsorbed Fe provides insight into the process of Fe(II)-induced structural modification of hematite surfaces, which in turn aids in assessing the effective reactivity of hematite surfaces in Fe(II)-rich environments.

X-ray crystal truncation rod (CTR) diffraction under hydrated conditions at circum-neutral pH was also used to determine the surface structure of Fe3O4(111) [2]. The sample was initially prepared following a wet chemical-mechanical polishing (CMP) method. The structural refinement leads to the identification of two oxygen- terminated domains that are chemically inequivalent and symmetrically distinct. These two domains can be identified as an oxygen octahedral-iron termination (aO2.61-aO1.0-oh1Fe2.55-bO1.0-bO3.0-td1Fe1.0-oh2Fe1.0-td2Fe1.0-R) and an oxygen mixed-iron termination (bO1.0-bO3.0-td1Fe0-oh2Fe1.0-td2Fe1.0-aO3.0-aO1.0-oh1Fe3.0-R) in the ratio of 75:25

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respectively. A bond-valence analysis suggests that the terminal oxygens in both domains are protonated. We have further observed that the tetrahedral iron sites within the mixed-iron domain (tdFe) have a reduced occupancy, nearly zero for the upper td1Fe site. Over time during exposure to aqueous solution, these site occupancies continue to decrease, resulting in a domain that is dominated by all octahedral iron. Therefore, our results suggest that octahedral iron is predominant at the surface of magnetite under environmental conditions.

References[1] Tanwar, K. S., S. C. Petitto, S. K. Ghose, P. J. Eng, and T. P. Trainor, Fe(II) adsorption on

hematite (0001). Geochim. Cosmochim, Acta 2009, 73, 4346-4365.[2] Petitto, S. C., K. S. Tanwar, S. K. Ghose, P. J. Eng, and T. P. Trainor, Surface structure of

magnetite (111) by crystal truncation rod diffraction. Surf. Sci. (submitted).

2. Evaluating the structure of poorly crystalline iron hydroxides (F. Marc Michel, Cristina Cismasu, and Gordon E. Brown, Jr.)

Poorly crystalline iron hydroxide phases commonly form in contaminated aqueous geochemical systems such as acid mine drainage environments and aerobic soils. In particular, the ferric iron oxyhydroxide known as ferrihydrite is an important component in these systems due to its tendency to scavenge potential environmental contaminants. With individual particle sizes typically less than 5 nm, ferrihydrite has a large amount of reactive surface area and is known to associate with metal and metalloids via coprecipitation and adsorption processes. The reactivity of this phase is therefore important in controlling the fate and transport of contaminants in the environment. The increased reactivity of ferrihyrite and other nano-sized phases is inextricably related to atomic structure. Conventional methods of structure determination are generally inadequate for quantitatively evaluating the 3-dimensional arrangement of atoms in nano-sized solids. However, the recent application of high-energy x-ray total scattering for pair distribution function analysis has led to considerable advancements in our understanding of the structures of both synthetic and natural samples of ferrihydrite [1]. In naturally occurring samples, this phase often precipitates under complex conditions and in aqueous systems containing a variety of species including organics, metals, and metalloids. The effects of these species on the resulting poorly crystalline precipitates are only partly understood. New results on samples collected from acid mine drainage sites build on recent work conducted on synthetic ferrihydrite and provide new insight into the structure of this important phase.

During the past year, we have continued our studies natural ferrihydrites containing significant amounts of impurity ions such as Al3+ and Si4+[2]. In addition, we have carried out a new study of the aging of synthetic ferrihydrite at 175°C, which results in its relatively rapid (one hour) transformation to hematite (a-Fe2O3) [3]. However, in the presence of citrate the transformation is slowed significantly, taking 14 hr to complete, and an intermediated phase was formed, which we found to be an ordered form of ferrihydrite with significantly larger particle size (10-12 nm) than its disordered precursor (2-4 nm). Another difference is that magnetic susceptibility measurements as a function of temperature show that the new phase is relatively styrongly ferromagnetic at ambient conditions, in contrast to the antiferromagnetic behavior of the disordered ferrihydrite precursor under the same conditions. Figure 10 shows total x-ray scattering data for a series of synthetic ferrihydrites aged for different lengths of time at 175°C in the presence of citrate (at a molar ratio with respect to Fe of 3 %). The structure of synthetic

14

disordered ferrihydrite proposed by Michel et al. [1] is consistent with the G(r) functions derived from the total x-ray scattering data from the ordered intermediate ferrihydrite and spin ordering of Fe3+ filling the two types of cation sites in the ordered form explains its measured magnetic moment (Fig. 11).

The high defect concentrations in the form of cation vacancies in fh result in substantial deviations between measured and predicted compositions and densities. By combining detailed structural information with measured total Fe and hydration losses from TGA, we are now able to propose a composition for disordered fh of Fe8.2O8.5(OH)7.4•3H2O, which differs significantly from previously suggested compositions, as well as that of ordered ferrifh (Fe10O14(OH)2•~1H2O). The compositional changes result in a large density increase of ferrifh (4.85-4.9 g cm-3) relative to its disordered precursor (4.0-4.3 g cm-3) that is consistent with the filling of cation vacancies in the basic structural model of ferrihydrite.

This study shows that there is no major difference in the overall structural topology between the disordered and ordered forms of ferrihydrite, and thus we are now able to confirm that the structure proposed for ferrihydrite [1] is verified in that it can reproduce both the real-space PDF and reciprocal space diffraction data. The nature of disorder in 2-line ferrihydrite can be understood as consisting, in part, of a random distribution of iron vacancies in two specific cation sites. With regard to the physiochemical characteristics and magnetic behavior of disordered ferrihydrite, deviations from ideal or predicted values can now be rationalized by our understanding of the effects of cation disorder and lattice strain.

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Figure 10. X-ray scattering and corresponding magnetic enhancement. a. X-ray total scattering plotted as scattering angle vs. intensity collected as a function of aging time (h) at 175°C. Initial formation of hematite indicated by appearance of features (e.g., *) at 8 h with transformation complete by t = 14 h. Angular regions with significant diffuse scattering develop into a set of peaks in the intermediate samples that are unrelated to hematite (e.g., arrows). b. Formation of a strongly magnetic phase indicated by increases in room temperature magnetic susceptibility () and saturation magnetization (Ms) at low temperature (5 K), with both reaching maxima at ~11 h.

References[1] Michel, F. M. et al., The structure of ferrihydrite, a nanocrystalline material. Science 2007,

316, 1726-1729.[2] Cismasu, C., F. M. Michel, J. F. Stebbins, A. P. Tcaciuc, and G. E. Brown, Jr., Molecular-

and nm-scale Investigation of the Structure and Compositional Heterogeneity of Naturally Occurring Ferrihydrite,” Abstracts with Program, American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

[3] F. M. Michel, V. Barrón, J. Torrent, M. P. Morales, C. J. Serna, J-F. Boily, Q. Liu, A. Ambrosini, C. A. Cismasu, and G. E. Brown, Jr., Ordered ferrimagnetic form of ferrihydrite reveals links between structure and magnetism. Proc. Nat. Acad. Sci. (2010, acccepted).

[4] Cornell, R. M. and Schwertmann, U. The Iron Oxides: Structure, Properties, Reactions, Occurrences and Uses (Wiley-VCH, 2003).

E. Sorption Processes a Solid-Aqueous, Microbe-Aqueous, and Solid-Biofilm Interfaces and Biomineralization

1. Redox chemistry between arsenic and magnetite surface at ambient conditions (Sarp Kaya, Tom Kendelewicz, John T. Newberg, Hendrik Bluhm, Gordon Brown, and Anders Nilsson)

Groundwater with high arsenic concentrations from natural sources is the primary source of drinking water in Bangladesh, Cambodia, and Vietnam and threatens the health of millions of people. The natural occurrence of arsenic in the aquatic environment is usually associated with its interaction with iron oxides in soils. The predominant forms of As in groundwater are the inorganic species arsenate [As(V)] and arsenite [As(III)], and both are known to be highly toxic. The chemistry of arsenic in aquatic systems is complex, and consists of oxidation-reduction, ligand exchange, precipitation, and adsorption. Despite the tremendous experimental effort on the interaction of arsenic wqith iron oxide surfaces, the exact mechanism by which arsenic is transferred into the water is not yet fully understood.

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Figure 11. Possible spin orientations and magnetic moment in ferrihydrite. (a) Based on the Michel et al., 2007 structure of ferrihydrite the A (tetrahedral) and B (octahedral) sites aligned antiparallel to one another results in a magnetic moment of 30 B. (b) A magnetic moment of 10 B, which is consistent with the measured value, can be obtained as a consequence of having 6 ions with spins in one direction and 4 ions opposing.

As part of our ongoing studies of the interaction of arsenic with iron oxide surfaces, we have used the Ambient Pressure Photoemission Spectroscopy endstation at the Advanced Light Source to study surface reactions of As with iron oxides at elevated pressures. Such in situ XPS studies are allowed for the first time using this end station and are crucial for gaining molecular-level information about equilibrium vs. kinetic effects in many surface chemical reactions. So far, we have studied the As-Fe3O4(111) system in various water atmospheres, at 0-30 % relative humidity (RH). Arsenic adsorption performed by pulse injection of As-containing solutions provided us with contaminant-free samples. One fourth of the Fe3O4 (111) surface is terminated by Fe+2 sites on which water molecules dissociate. Full OH termination is achieved at very low RH values; however, the amount of condensed water keeps increasing with RH. At 30 % RH, more than 2 ML water is present on the surface of Fe3O4(111).

Figure 12 illustrates systematic As 3d and Fe 2p3/2 XPS spectral changes with increasing RH. From the full-width-half-maximum of the As 3d peak at the lowest RH studied, we conclude that As(III) and As(V) coexist. Increasing RH from 10-5 % to 1 % gives rise to a clear oxidation state change, ultimately reaching As(V) at 20 % RH. A complementary redox mechanism is also seen. Two different types of cation sites exist in crystalline Fe3O4: tetrahedrally coordinated Fe sites (typically with a charge state of 3+), and octahedrally coordinated sites (typically with charges states of 2+ and 3+ in equal proportions). Attenuation of the Fe3+ component with systematic appearance of the Fe2+ component shows that during As(III) oxidation to As(V), some Fe3+ in the Fe3O4 (111) surface experiences a reduction to Fe2+. Further investigations are underway to explore whether there is a buried layer between As and Fe3O4(111). Also mechanisms of possible As(III) reduction on Fe2O3 surfaces will be studied using a similar approach.

48 47 46 45 44 43 42 41Binding energy (eV)

RH 2.8E-8 % 3.7E-5 % 0.93 % 20 %

As 3dhν = 250 eV

As(V ) As(III)

716 712 708Binding energy (eV)

Fe 2p3/2

hν = 920 eV

Fe3+

Fe 2+

Figure 12. As 3d and Fe 2p3/2 XPS spectra recorded at various relative humidities.

2. Arsenic(III) polymerization upon sorption on iron(II,III)-(hydr)oxide surfaces – Implication for arsenic mobility under reducing conditions (Guillaume Morin, Georges Ona-Nguema, Yuheng Wang, Farid Juillot, Nicolas Menguy, Georges Calas, and Gordon E. Brown, Jr.)

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Arsenic is a toxic metalloid involved in important health issues due to its presence as a water pollutant in many parts of the world. A major control of the aqueous concentration, mobility, and cycling of arsenic is its sorption to and desorption from iron oxides surfaces. The modes of arsenic sorption to the surface of Fe(III) (oxyhydr)oxides have been extensively documented by XAFS and RAXR and include both inner- and outer-sphere monomeric surface complexes.

In contrast, recent investigations of arsenic-iron systems under anoxic conditions [1,2]

have revealed that As(III), the more toxic reduced form of arsenic, tend to form polymeric surface complexes, and surface precipitates at the surfaces of Fe(II,III)-(hydr)oxides. EXAFS and HRTEM studies of the bioreduction products of As-doped iron-(oxyhydr)oxides have revealed that As(III) sorbs as oligomeric species at the surface of Fe(OH)2 (Fig. 13) and green-rusts [1,2] (Fig. 14). These new types of As(III) surface complexes are consistent with the bonding geometry of As(III) in ferrous arsenite minerals. We have also recently shown that As(III) forms surface precipitates at high surface coverage on magnetite nano-particles, although tightly bound monomeric surface complexes form at low surface coverage [3].

Adsorption of As(III)-oligomers to Fe(II,III)-(oxyhydr)oxide surfaces may help limit As(III) mobility in reducing Fe(II)-rich groundwaters. However, the relatively high solubility of As(III)-surface precipitates forming at high surface coverage on nanomagnetite particles should be taken into account in designing magnetite-based water-treatment processes.

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Figure 14. Fourier transforms (left panel) and proposed structural model of As(III) sorption complexes (right panel) on green rust at pH 7 (from

0 2 4 6 8

R + ΔR (Å)

2.70 μmol/m2

0.27 μmol/m2

As(III) / green rust As-O1.79 Å

3.3 Å3.5 Å

4.7 Å

Figure 13. Fourier transforms (left panel) and proposed structural model of As(III) sorption complexes (right panel) on Fe(OH)2 at pH 7 (from [1]).

References[1] Ona-Nguema G., G. Morin, Y. Wang, N. Menguy, F. Juillot, L. Olivi, G. Aquilanti, M.

Abdelmoula, C. Ruby, F. Guyot, G. Calas, and G.E. Brown, Jr., Geochim. Cosmochim. Acta 2009, 73, 1359-1381.

[2] Wang, Y., G. Morin, G. Ona-Nguema, N. Menguy, F. Juillot, E. Aubry, F. Guyot, G. Calas, and G.E. Brown, Jr., Geochim. Cosmochim. Acta 2008, 72, 2573-2586.

[3] Morin, G., Y. Wang, G. Ona-Nguema, F. Juillot, G. Calas, E. Aubry, J.R. Bargar, and G.E. Brown, Jr., Langmuir (2009, in press).

3. Interaction of Zn(II) and oxalate with nano- and micro-particles of hematite (Juyoung Ha, Thomas P. Trainor, Francois Farges, and Gordon E. Brown, Jr.)

Sorption of Zn(II) to hematite nanoparticles (HN) (avg. diam. = 10.5 nm) and microparticles (HM) (avg. diam. = 550 nm) was studied in the presence of oxalate anions (Ox2-

(aq)) in aqueous solutions as a function of total Zn(II)(aq) to total Ox2-(aq) concentration ratio (R =

[Zn(II)(aq)]tot/[Ox2-(aq)]tot) at pH 5.5. Zn(II) uptake is similar in extent for both the Zn(II)/Ox/HN

and Zn(II)/Ox/HM ternary systems and the Zn(II)/HN binary system at [Zn(II)(aq)]tot < 4 mM, whereas it is 50 to 100% higher for the Zn(II)/Ox/HN system than for the Zn(II)/Ox/HM ternary and the Zn(II)/HN and Zn(II)/HM binary systems at [Zn(II)(aq)]tot > 4 mM. In contrast, Zn(II) uptake for the Zn(II)/HM binary system is a factor of two greater than for the Zn(II)/Ox/HM and Zn(II)/Ox/HN ternary systems and the Zn(II)/HN binary system at [Zn(II)(aq)]tot < 4 mM. In the Zn(II)/Ox/HM ternary system at both R values examined (0.16 and 0.68), ATR-FTIR results are consistent with the presence of inner-sphere oxalate complexes and outer-sphere ZnOx(aq)

complexes, and/or type A ternary complexes (Fig. 15-left). In addition, EXAFS spectroscopic

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Figure 15. (left panel) ATR-FTIR spectra of binary oxalate/hematite nanoparticles (Ox/HN), oxalate/hematite microparticles (Ox/HM), ternary Zn(II)/oxalate/hematite nanoparticles (Zn(II)/Ox/HN), and Zn(II)/oxalate/hematite microparticles (Zn(II)/Ox/HM). Subscripts of R refer to the [Zn(II) (aq)]total/[Ox(aq)]total ratio in each system. Dashed vertical lines (- - -) indicate major peaks in the spectra of the binary systems, and dotted vertical lines (····) indicate ternary sample peaks matching the ZnOx(s)

reference spectrum. The aqueous oxalate spectrum is for a sample with [Ox(aq)]total = 10mM, pH 5.5, and 0.01M NaCl, and the aqueous ZnOx(aq) spectrum is for a sample with [Ox(aq)]total = 10mM, [Zn(II)(aq)]total = 10mM, pH 5.5, and 0.01M NaCl. (right panel) Zn K-edge EXAFS spectra and Fourier transforms of binary (Zn(II)/hematite) and ternary Zn(II)/Ox/hematite systems. Zn(II)/HN refers to hematite nanoparticles with a Zn surface loading (Zn(II)) = 2.3 mol/m2 hematite, and Zn(II)/HM refers to hematite microparticles with Zn(II) = 4.17 mol/m2. HN-R and HM-R refer to ternary samples with varying [Zn(II)(aq)]total/[Ox2-

(aq)]total ratios. In the ternary samples [Ox2-

(aq)]total was 8 mM with varying [Zn(II)(aq)]total at pH 5.5 and 0. oxalate-hematite ternary system. 01M NaCl. Dashed lines represent fits of the spectra to structural models described in the text (from [1]).

results suggest that type A ternary surface complexes (i.e. >O2-Zn-Ox) are present (Fig. 15-right). In the Zn(II)/Ox/HN ternary system at R = 0.15, ATR-FTIR results indicate the presence of inner-sphere oxalate and outer-sphere ZnOx(aq) complexes (Fig. 15-left); the EXAFS results provide no evidence for inner-sphere Zn(II) or type A ternary complexes (Fig. 15-right).

In contrast, ATR-FTIR results for the Zn/Ox/HN sample with R = 0.68 are consistent with a ZnOx(s)-like surface precipitate and possibly type B ternary surface complexes (i.e. >O2-Ox-Zn) (Fig. 16). EXAFS results are also consistent with the presence of ZnOx(s)-like precipitates. We ascribe the observed increase of Zn(II)(aq) uptake in the Zn(II)/Ox/HN ternary system at [Zn(II)(aq)]tot ≥ 4 mM relative to the Zn(II)/Ox/HM ternary system to formation of a ZnOx(s)-like precipitate at the hematite nanoparticle/water interface (Fig. 16).

Reference[1] Ha, J., T.P. Trainor, F. Farges, and G.E. Brown, Jr., Interaction of Zn(II) with hematite

nanoparticles and microparticles: Part 2. ATR-FTIR and EXAFS spectroscopy study of the Zn(II)-oxalate-hematite ternary system. Langmuir 2009, 25(10), 5586-5593.

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Figure 16. Possible Zn(II) and oxalate surface species in the two ternary systems: (A) independently adsorbed inner-sphere oxalate and outer-sphere Zn(II) surface complexes in Zn(II)/Ox/HN with R = 0.15; (B) surface precipitates involving >Fe-Ox-Zn-Ox, type B surface complex involving >Fe-Ox-Zn, and inner-sphere complexes of Zn(II) in Zn(II)/Ox/HN with R = 0.68; (C,I) type A surface complex involving >O-Zn-Ox in the Zn(II)/Ox/HM ternary system with R = 0.16 and 0.68; (C,II) independently adsorbed inner-sphere Zn(II) and outer-sphere ZnOx(aq) surface complexes in the Zn(II)/Ox/HM system with R = 0.16 and 0.68. Dotted lines indicate the electrostatic and/or hydrogen bonds associated with outer-sphere complexes at the hematite/water interface.

4. Reductive adsorption of aqueous U(VI) on magnetite surfaces (Kevin Rosso, Frances Skomurski, Eugene Ilton (PNNL), and Sebastian Kerisit (PNNL))

In 2009, with the help of post-doc Dr. Frances Skomurski, we studied the reductive adsorption of U6+ in solution by Fe2+ in magnetite (FeIIFeIII

2O4) [1]. This reaction has the potential to retard radionuclide transport in some sub-surface environments and to help minimize radionuclide release from waste-packaging materials surrounding spent nuclear fuel. However, complete reduction to U4+ from Fe2+-bearing iron oxide phases is not always observed. The purpose of this research is to determine if there is a rate-limiting step in the reduction of U 6+ to U4+ by Fe2+ in magnetite. Using combined experimental and atomic-scale modeling approaches, we addressed the following questions:

Experimental:1) Is Fe2+ present on cleaved magnetite (100) surfaces for interaction with adsorbates? 2) What is the oxidation state of U following adsorption onto magnetite single crystals?

(i.e. starting as uranyl (UO2)2+ in solution)

Computational:1) How do rates of electron transfer between octahedral-iron sites (Feoct) in magnetite

compare for bulk versus surface environments? 2) How do rates of electron transfer between Fe2+ and U6+ (or U5+) compare with bulk and

surface rates of electron transfer in magnetite?

Natural single crystals of magnetite were cleaved parallel to the cubic (100) surface, and Fe2+:Fe3+ ratios were measured using X-ray photoelectron spectroscopy (XPS). Uranium-adsorption experiments (~90 hours; pH 4.4) were performed in a N2-filled glove box on the mating halves of the aforementioned surfaces. Following the reaction, XPS was used to determine the ratio of U6+, U5+ and U4+ peaks on the magnetite surfaces, as well as changes in the ratio of Fe2+ to Fe3+. Surfaces were further characterized using scanning electron microscopy to determine the nature of any precipitates.

Quantum-mechanical calculations were used to determine the lowest-energy charge distribution of Fe2+ and Fe3+ in bulk magnetite, and in magnetite slabs representing hydrated and vacuum-terminated (100) surfaces. Since room temperature electron conduction occurs along chains of Feoct in magnetite, Fe2+-Fe3+ dimers were extracted from each optimized model and hydrated to stabilize dangling bonds. Rates of electron polaron hopping were calculated for each cluster to determine the effects of local charge distribution, as well as bulk versus surface environments, on electron conductivity. Additional models were created where a uranyl molecule is docked on an iron dimer (described above) in an inner-sphere bidentate fashion, via bridging hydroxyl groups. Rates of interfacial electron transfer from Fe2+ in the surface models to adsorbed U6+ were calculated as a function of Fe2+ concentration, U charge, and changes in uranyl ligation (e.g., H2O vs. OH) and coordination (e.g., 7-fold versus 8-fold coordination) achieved by moving protons and adding an additional water molecule.

XPS analyses of cleaved magnetite (100) surfaces indicate that Fe2+ is present in (near-) surface environments, with Fe2+:Fe3+ ratios being stoichiometric (~1:2) or slightly sub-

21

stoichiometric, depending on the sample. Following exposure to uranyl-nitrate solution ([U]=10 -

4 mol/L), uranium is detected on the magnetite surfaces. For the stoichiometric sample, a mix of U6+ and U5+ peaks are observed when fitting the XPS data; for the sub-stoichiometric case, only U6+ is observed. No U4+ is detected in either case. Changes in Fe2+:Fe3+ ratios in the U-exposed samples may be due to a combination of reductive adsorption and preferential release of Fe2+ into solution. Time-resolved XPS data suggest that beam-induced reduction of U6+ to U5+ or U4+

becomes a factor after short amounts of exposure time to the beam (e.g., less than 10 minutes for some samples); data here are free of this artifact as they were analyzed as close t = 0 as possible. SEM analyses of the stoichiometric sample reveal the presence of U-bearing surface precipitates on the stoichiometric magnetite sample.

Consistent with experimental data, charge distribution calculations for hydrated and vacuum-terminated magnetite (100) surfaces suggest that Fe2+ is available in (near-) surface environments. Intrasurface electron hopping rates were successfully calculated for bulk, near-surface, and surface environments for magnetite, and range in value from 1010-1011 hops/s (bulk), 1011-1012 hops/s (near-surface), and 109-1012 hops/s (surface). These values are in good agreement with experimentally determined rates of 1012 hops/s for magnetite. The different ranges of values reflect increasing amounts of structural relaxation when moving from bulk to surface environments, and suggest that bulk rates may not always apply directly to surface environments. The presence of water at the (100) surface does not alter rates significantly.

A postulated rate-limiting step was examined using the quantum-mechanical calculations involving the U-Fe-Fe clusters. Total energy comparisons of clusters with different Fe/U charge distributions suggest that an increase in coordination number must occur for U6+ adsorbed in a uranyl-type structure to be stabilized as U4+ on the magnetite surface. With respect to Fe2+

availability, if U6+ is docked to two Fe2+ ions (“stoichiometric”), it is energetically favorable for U5+ and one Fe3+ to form in the process. Rates of ET are similar to those between Fe2+ and Fe3+

in magnetite (~1011 hops/s). However, if U6+ docks with an Fe2+ and an Fe3+ ion (“sub-stoichiometric”), the conversion to U5+ is energetically up-hill with an ET rate of ~104 hops/s. In terms of observed oxidation states, these results are consistent with those obtained experimentally, and suggest that the availability of excess Fe2+ in near-surface environments, combined with an energy-lowering change in the coordination environment of U is necessary to overcome the energy barrier to complete reduction to U4+.

Two publications are in preparation on this work. The remainder of 2009 will entail completing final calculations for the magnetite-uranium system, and finalizing manuscripts for submission.

Reference[1] Skomurski, F.N., S. Kerisit, E.S. Ilton, and K.M. Rosso, U6+ interactions with Fe2+ in magnetite. Abstracts with Program, 237th National Meeting of the American Chemical Society, Salt Lake City, UT, March, 2009 (abstract).

22

5. Factors controlling the partitioning of Pb(II) and Zn(II) at the metal oxide/microbial biofilm/water interfaces (Yingge Wang, F. Marc Michel, Alexandre Gélabert, Johannes Gescher, Carmen D. Cordova, Yong Choi, Peter J. Eng, John R. Bargar, Joe Rogers, Sanjit K. Ghose, Georges Ona-Nguema, Alfred M. Spormann, and Gordon E. Brown, Jr.)

Microbial biofilms are often present as coatings on mineral surfaces and may induce significant changes in speciation and partitioning of metal(loid) ions in soils and aqueous environments. To study their potential impact on metal cycling, we have used long-period X-ray standing wave-florescence yield (XSW-FY) spectroscopy to measure the in-situ partitioning of Zn(II) and Pb(II) between the gram-negative bacterium S. oneidensis MR-1 biofilm and highly polished single crystal surfaces of a-alumina (0001), (1-102) and hematite (0001) as a function of metal concentration and pH. Since last year’s EMSI report, we have made significant progress in improving the LP-XSW experimental protocols and in quantifying the fluorescence-yield measurements, and we report new results from experimens at the APS on BL ID-13-C. Biofilm growth dynamics on these surfaces were monitored using confocal laser scanning microscopy (CLSM) for 20 days, demonstrating that 10-day growth of biofilms exhibit a homogeneous surface coverage, and thus were used in subsequent spectroscopic measurements. In-situ XSW-FY measurements at pH 6.00 ± 0.05 demonstrated that Pb(II) is preferentially sorbed on the mineral surface at low concentrations (10-7 M) and is increasingly partitioned into the biofilm at higher concentrations (10-6 to 10-4 M) (Fig. 17-right) [1]. These results indicate that S. oneidensis biofilms do not block the reactive sites of mineral surfaces which, in addition to previous XSW studies on Pb(II) partitioning using B. Cepacia cells [2], confirms the existence of a general chemical trend occurring at the biofilm/mineral/water interfaces. Furthermore, hematite (0001) was found to be the most reactive surface for metal sorption at these complex interfaces followed by a-alumina (1-102) and a-alumina (0001) (Fig. 18-left) [3]. In addition, Pb L3-edge grazing incidence X-ray adsorption fine structure (GI-XAFS) measurements were performed at different X-ray incidence angles, and show that carboxyl groups are responsible for Pb complexation in the biofilm at pH 6. No evidence of biomineralization in the form of pyromorphite was found.

In the Zn/metal oxide/S. oneidensis/water system, Zn(II) tends to be sorbed on the

hematite (0001) surface at low concentrations (10-6M), and increasingly partitions into the biofilm at higher concentrations [1]. These results confirm that the biofilms do not block the reactive sites of mineral surfaces, which is consistent with the conclusion of the first part of this study for Pb distributions at S. oneidensis MR-1 biofilm/mineral/water interfaces. However, for two other mineral surfaces, a-alumina (0001) and (1-102) (Fig. 18-right), Zn(II) is partitioned mainly into the biofilm for the range of metal concentrations used in this study, reflecting the higher reactivity of the hematite mineral compared to the two other surfaces (Fig. 18-right) [3]. Zn K-edge grazing incidence X-ray adsorption fine structure (GI-XAFS) measurements were also performed at different X-ray incidence angles, probing Zn speciation the biofilm or the mineral surface, respectively. The speciation of zinc in the biofilm is mainly in the form of carboxyl complexes as is also true in the case of lead complexation. The results obtained demonstrate a different behavior for metal sorption at the complex interface water/microbial biofilm/mineral between Zn(II) and Pb(II) that can not be explained by the different speciation in the biofilm. This study demonstrates that instead of shielding the reactive sites of the mineral substrate, biofilms provide additional sorption sites for metal complexation at the complex microbial-mineral interface.

23

Figure 17. (left) Long-period x-ray standing wave fluorescent yield (LP-XSW-FY) and x-ray reflectivity data for Pb(II) interactions with an Shewanella oneidensis MR-1-coated hematite (0001) surface at different Pb concentrations. (right) LP-XSW-FY and x-ray reflectivity data for Zn(II) interactions with an S. oneidensis MR-1-coated hematite (0001) surface at different Zn concentrations. Tables at the bottom show results of quantitative fitting of the FY data.

24

Incident Angle ()

Pb=10-5 M

Pb=10-6 M

Pb=10-7 M

5446-7% at surface% in biofilmlog [Pb](aq)

0.499.6-52674-6

Zn=10-7 M

Zn=10-6 M

Zn=10-5 M

7426-7% at surface% in biofilmlog [Zn](aq)

0.199.9-55644-6

Pb=10-7 M Zn=10-6 M

25

Pb=10-6 M

Pb=10-5 M

0.499.6-7% at surface% in biofilmlog [Pb](aq)

0.0599.95-50.0699.94-6

0.0199.99-6% at surface% in biofilmlog [Zn](aq)

0.0199.99-40.0199.99-5

Zn=10-5 M

Zn=10-4 M

Figure 18. (left) Long-period x-ray standing wave fluorescent yield (LP-XSW-FY) and x-ray reflectivity data for Pb(II) interactions with an Shewanella oneidensis MR-1-coated a-Al2O3 (0001) surface at different Pb concentrations. (right) LP-XSW-FY and x-ray reflectivity data for Zn(II) interactions with an S. oneidensis MR-1-coated a-Al2O3 (0001) surface at different Zn concentrations. Tables at the bottom show results of quantitative fitting of the FY data.

References[1] Wang, Y., A. Gélabert, Y. Choi, J. Ha, J. Gescher, C. Cordova, J. R. Bargar, J. Rogers, P.J.

Eng, F. Farges, A. M. Spormann, and G. E. Brown, Jr., The impact of S. oneidensis MR-1 biofilm coatings on the reactivity of hematite, Abstracts with Program, American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

[2] Templeton, A. S., T. P. Trainor, S. J. Traina, A. M. Spormann, and G.E. Brown, Jr., Pb(II) distribution at biofilm-metal oxide interfaces. Proc. Nat. Acad. Sci. U.S.A. 2001, 98, 11897-11902.

[3] Wang, Y., A. Gélabert, J. Ha, G. Ona-Nguema, J. Gescher, C. Cordova, J. R. Bargar, J. Rogers, P. J. Eng, S. K. Ghose, A. M. Spormann, and G. E. Brown, Jr., Impact of S. oneidensis MR-1 biofilm coatings on trace element partitioning at metal-oxide/water interfaces: A long-period XSW-FY study, 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

6. Role of sulfhydryl sites on bacterial cell walls in the sorption and bioavailability of mercury (Satish Myneni et al.)

Bacteria are common in all terrestrial and marine systems and play an important role in the solubility and transformation of nutrients and contaminants in the environment. The functional group composition of bacterial cell walls and their interactions with metals and minerals in the environment dictate the transformations and the cycling of nutrients and contaminants. However, the interfacial chemistry of bacteria and the reactions occurring therein are poorly understood. While recent studies indicated that carboxylate and phosphoryl groups are active in binding metals such as U, Cd, and Hg, a majority of these studies focused at high aqueous phase metal concentrations, greater than those normally encountered even in highly contaminated settings. Together with some initial funding from the ERSP program in DOE, we examined how bacterial cell walls interact with Hg(II) at low metal concentrations and modify its redox state, solubility, and transport in the environment. Our specific research goals are (1) examine the functional group composition of bacterial cell walls, especially the S sites, that are important in metal binding, (2) reactivity of S sites with Hg under a range of biogeochemical conditions (e.g., pH, metal concentration, bacterial species), and (3) the fate of adsorbed and transformed metals with cell decomposition. The bulk adsorption experiments on Hg(II) were conducted by our collaborator Dr. Jeremy Fein (University of Notre Dame) as a function of pH and chloride concentration and on three representative bacterial species: Bacillus subtilis, a common gram-positive aerobic soil species; Shewanella oneidensis, a facultative gram-negative surface water species; and Geobacter sulfurreducens, an anaerobic iron-reducing gram-negative species that is capable of Hg methylation.

Based on the results from bulk sorption measurements, we focused our molecular investigations as a function of Hg concentration (0.5-350 M) at pH values of 6.0 (± 0.5). We conducted detailed X-ray absorption spectroscopy studies (XANES and EXAFS) at the Hg LIII

and S K absorption edges to identify the nature of S sites on bacteria, and the types of Hg complexes as a function of Hg concentration. Our results clearly document that the structure and the coordination environment of Hg complex change dramatically with small changes in aqueous phase concentration even in the nanomolar range (Fig. 19).

26

The XAS results indicate that the dominant Hg(II)-binding groups on bacterial surfaces are thiols when aqueous Hg concentration was below 50 M. Above this concentration carboxyls became the primary binding sites for Hg(II). In addition, our studies suggest that the Hg-S complex changes from a trigonal or a T-shaped HgS3 complex with Hg-S distances at 2.51 Å at a Hg concentration of ~ 0.5 M to HgS or HgS2 type complexes with Hg-S distances around 2.3 Å in the Hg concentration range of ~2.5-25 M. Studies at the S K-absorption edge also provided direct evidence that Hg binds to S groups via interactions with thiol groups. We also found that all of the bacteria we studied exhibited the same types of coordination environments for Hg(II); however, the relative concentrations of the complexes change as a function of Hg concentration.

The changes in the structure of Hg-S complexes on bacterial surfaces at sub-micromolar Hg concentrations can significantly influence Hg methylation rates and its transport in contaminated aquatic systems. Studies are in progress to evaluate the stability of Hg-S complexes on bacterial surfaces, and the nature of Hg-S complexes in the case of methylating bacteria to establish a correlation between methylation rates and the type of surface complex.

Figure 19. Fourier transform magnitude of EXAFS data for Hg adsorbtion to Shewanella oneidensis as a function of a dsorbed Hg at pH 5.5 (± 0.2). The red and green lines correspond to 2.51 and 2.32 Å (phase corrected), respectively.

F. Theoretical Modeling of Solid-Aqueous Interfaces and Interfacial Reactions

1. Density functional theory investigation of the (1-102) surface of a-Al2O3 and a-Fe2O3 – effects of hydration and protonation (Shela Aboud, Jennifer Wilcox (Department of Energy Resources Engineering, Stanford University) and Gordon E. Brown, Jr.)

We have used self-consistent density functional theory (DFT) to investigate the stabilities of different oxygen- and hydrogen-terminated (1-102) surfaces of a-Al2O3 and a-Fe2O3.

27

Figure 20. Hexagonal unit cell for a-Fe2O3 and a-Al2O3.

Computations Methods – Density functional theory calculations were performed with the Vienna ab initio Simulation Package (VASP) [1] using the projector augmented wave (PAW) method [2] to describe the ion-electron interactions. Electron exchange-correlation functionals were represented with the generalized gradient approximation (GGA), and the model of Perdew, Burke and Ernzerhof (PBE) [3] was used for the nonlocal corrections. The a-Fe2O3 simulations were conducted including spin polarization, where the spin interpolation of the exchange-correlation function was from Vosko, Wilk and Nusair [4]. A plane wave expansion cutoff of 450 eV was applied, and the surface Brillouin zone integration was calculated using a gamma centered 4x4x4 Monkhorst-Pack mesh [5]. Methfessel and Paxton [6] Gaussian smearing of order 1 was used with a width of 0.2 eV to accelerate convergence of the total energy calculations. Geometric optimization was performed using the conjugate-gradient algorithm until the absolute value of the forces on unconstrained atoms was less than 0.03 eV/Å.

Bulk Properties (lattice parameters) – The bulk simulations of a-Al2O3 and a-Fe2O3 were conducted using a 10-atom unit cell (4 Al or Fe and 6 O) as shown in Figure 20. The starting structures for the VASP simulations were constructed based on experimentally measured atomic coordinates [7,8]. a-Fe2O3 is antiferrormagnetic at temperatures below the Morin transition temperature, TM = 250K [9], with the spins aligned along the [111] rhombohedral axis.

Previous spin-polarized DFT calculations of bulk a-Fe2O3

were able to reproduce the most energetically stable antiferromag-netic spin configuration, which results in alternating layers of spin along the c-axis of the hexagonal unit cell [10]. Accounting for the correct spin orientation in the DFT simulations is critical for determining the correct geometric properties of the a-Fe2O3 lattice [11]. The simulated equilibrium lattice parameters were determined by varying the size of the unit cell to minimize the free energy of the system. The resulting parameters for a, b, and c are given in Table 1 along with the initial experimental values. Both materials match very well with the experimental values. The a-Al2O3 and a-Fe2O3 unit cell volumes were found to increase by 1%

and decrease by 0.1%, respectively. To benchmark the accuracy of the DFT simulation parameters, a bulk simulation was run for a-Al2O3 and the layer spacing along the [ 211 ] direction was calculated and compared with previous work by Trainor et al. [13] as shown in Figure 21. The relaxed layer spacing is in excellent agreement (within 2%) with the previous work.

Table 1 Lattice parameters (Å) [7,8] Bandgap (eV) [12,13]a b c

Exp - Al2O3 4.759 4.759 12.991 9Calc - Al2O3 4.807 4.807 13.122 5.84Exp - Fe2O3 5.038 5.038 13.772 2.2Calc - Fe2O3 5.031 5.031 13.753 0.45

28

The partial density of states (DOS) was calculated by projecting the electron wavefunctions onto spherical harmonics centered on the metal and oxygen atoms. Figure 22 shows a plot of the DOS for a-Al2O3 and a-Fe2O3. In the case of a-Fe2O3 only the DOS of the majority spins are shown. The DFT underestimates the bandgap of both materials as shown in Table 2 which is a well know effect of GGA functionals. The fully localized limit of the GGA, or GGA+U adds a Coulomb repulsion term to the DFT Hamiltonian [14] and was

developed, in part, to correct band gap errors for insulators [7].

(1-102) Oxygen-Terminated Surfaces – The (1-102) surfaces were constructed by cleaving the bulk oxides along the ( 211 ), (110), and (-111) planes as shown in Figure 23 for a-Fe2O3. The solid and dashed Fe atoms correspond to spin up and spin down states. The corresponding a-Al2O3 structure is analogous without the spin states. In the simulation along the [1-12] direction, the slab consists of 20-24 atomic layers and is separated by approximately 30Å of vacuum to ensure electronic isolation from periodic images. The energy change resulting from increasing the structure to 30 atomic layers and 40 Å of vacuum was less than 0.5%. Also these parameters are consistent with previous DFT studies of a-Fe2O3 that used 16-22 layers and a 10 Å vacuum region [15].

There are two stable configurations of the oxygen-terminated surface for the (1-102) structure and are shown in Figures 24(a) and 24(b) for a-Al2O3. The configuration denoted model 1 (M1) in Figure 24(a) corresponds to O atoms adsorbed directly at the Fe/Al sites in the ideal stoichiometric-terminated surface, whereas model 2 (M2) shown in Figure 24(b) corresponds to the ideal stoichiometric-terminated surface with the first layer Fe/Al atoms removed. Table 2 shows the layer relaxation compared to the bulk for M1 and M2 in a-Al2O3.

29

Figure 21. Bulk a-Al2O3 structure with equilibrated layer spacing that is less than 2% different compared with the work of Trainor et al. [13] as shown in

Figure 22. Density of states calculated for bulk for (a) a-Al2O3 and (b) a-Fe2O3.

The M2 surface with the missing atoms has been found to correspond to the optimal configuration for both a-Al2O3

[16] and a-Fe2O3 [9].

(1-102) Protonated Surfaces – While CTR x-ray diffraction studies can do an excellent job of predicting the surface oxygen configuration and atomic layering structure, the protonation states of oxygen groups cannot be uniquely determined. However, the DFT computational studies provide a valuable tool to help understand how hydrogen is oriented on the surface and also how far into the structure protonation of oxygens occurs. In this study, several layers of the surface oxygen atoms were protonated, the energy of the system was recorded, and the corresponding layer relaxation was measured. While a complete thermodynamic analysis is currently underway, results show that the M2 surfaces are generally the most energetically stable. Shown in Figure 25 are the three most energetically stable protonated M2 surfaces which have varying amounts of bound hydrogen including (a) (HO)2-(HO)2-

30

Figure 23. Stoichiometric structure of the ( 0211 ) a-Fe2O3

(1x1) surfaces showing (a) a cleavage plane in the unit cell, (b) top view of the ( 0211 ) surface with the (1x1) cell outlined with the black dashed lines, and (c) side view showing the atomic layers of the slab for 2 (1x1) cells.

Figure 24. Two stable oxygen terminated surfaces of a-Al2O3 denoted (a) M1 for oxygen added to the stoichiometric and (b) M2 for the surface missing the top layer metal atoms.

(a) (b)

Al2-R, (b) (HO)2-Al2-(HO)2-Al2-R, to (c) (H2O)2-(HO)2-Al2-R., where R is the repeating sequence of the stoichiometric structure.

Figure 25(c) contains the maximum number of hydrogen atoms that can attach to the surface oxygen atoms for the M2 surface and corresponds to 5 hydrogen atoms per unit surface a-Al2O3. Structures with increased protonation did not converge. Similarly, simulations with more than 3 hydrogen atoms per unit surface a-Al2O3 did not converge for the M1 surface. This is consistent given the charge state of the surface Al in the M1 and M2 surfaces are III and VI, respectively for the nonprotonated surfaces. Table 3 shows the layer relaxation for the different surfaces considered in this work compared to experimental CTR x-ray diffraction studies by Trainor et al. [16]. Overall, the results for all the surfaces compare reasonably

well with the best trend found for the surface with only the terminating oxygen protonated. It is interesting to note that the surface with the most protons per unit a-Al2O3 and therefore a balanced surface Al charge has a structure that is most bulk-like. This result is consistent with previous DFT results of a-Fe2O3 as well [15]. Only the (HO)2-(HO)2-Fe2-R protonation state for the M1 surface has been calculated for a-Fe2O3 and the layer spacing is compared with the DFT calculations of Lo et al. [15] in Table 4. As can be seen, the agreement is good, with a maximum difference of 5.6% occurring between layers 4 and 5. Table 3. Calculated layer spacing with percent relaxation in parenthesis for protonated a-Al2O3 surfaces.

Layer (HO)2-Al2-R (HO)2-(HO)2-Al2-R

(HO)2-(HO)2-Al2-(HO)2-R

(H2O)2-(HO)2-Al2-R

Trainor et al. [16] (Model B)

Δ(1-2) (Å) 1.219 1.122 1.201 1.378 1.460

Δ (2-3) (Å) 0.226 (-67.43%) 0.517 (-26.0%) 0.425 (-39.17%) 0.680 (-2.69%) 0.368 (-48.3%)

Δ (3-4) (Å) 0.662 (89.64%) 0.573 (64.1%) 0.571 (63.70%) 0.340 (-2.69%) 0.465 (31.3%)

Δ (4-5) (Å) 1.192 (-10.14%) 1.205 (-9.12%) 1.221 (-7.85%) 1.322 (-0.33%) 1.200 (-11.0%)

Δ (5-6) (Å) 0.426 (22.16%) 0.351 (0.78%) 0.423 (21.34%) 0.350 (0.17%) 0.403 (13.7%)

Δ (6-7) (Å) 0.702 (0.41%) 0.723 (3.44%) 0.656 (-6.17%) 0.706 (1.00%) 0.781 (9.8%)

Δ (7-8) (Å) 0.668 (-4.49%) 0.655 (-6.25%) 0.657 (-6.02%) 0.692 (-1.04%) 0.641 (-9.8%)

Δ (8-9) (Å) 0.344 (-1.40%) 0.365 (4.65%) 0.362 (3.77%) 0.343 (-1.59%) 0.344 (-3.0%)

Δ (9-10) (Å) 1.339 (0.96%) 1.312 (-1.05%) 1.302 (-1.82%) 1.316 (-0.78%)

Δ (10-11) (Å) 0.339 (-2.81%) 0.348 (-.26%) 0.349 (0.06%) 0.344 (-1.26%)

Layer M1

(O2-O2-Al2-R)

M2

(O2-O2-Al2-R)

Δ(1-2) (Å) 1.432 0.852

Δ (2-3) (Å) 0.350 (-0.18%) 0.884 (26.4%)

Δ (3-4) (Å) 0.648 (-7.33%) 0.366 (4.73%)

Δ (4-5) (Å) 0.750 (7.27%) 1.279 (-3.53%)

Δ (5-6) (Å) 0.392 (12.371%) 0.380 (8.97%)

Δ (6-7) (Å) 1.316 (0.78%) 0.756 (8.20%)

Δ (7-8) (Å) 0.368 (5.31%) 0.700 (0.27%)

Δ (8-9) (Å) 0.721 (3.10%) 0.342 (-1.92%)

Δ (9-10) (Å) 0.709 (1.46%) 1.366 (3.01%)

31

Table 2. Calculated layer spacing with percent relaxation in parenthesis.

Preliminary Results – There are several issues concerning how to include the proper magnetic state of both the Fe in the surface and in the bulk at ambient temperatures. Below the Morin transition temperature (TM < 260K) a-Fe2O3 is antiferromagnetic, but at room temperature, the oxide is weakly ferromagnetic due to spins being deflected from the c axis, that is, spin-canted, by an angle of < 0.10. Furthermore, the temperature at which the transition to a weakly ferromagnetic state, and even the transition to the paramagnetic state (in bulk defined as the Neel temperature TN = 900K) depend on the particle size. This clearly signifies the differences in surface magnetization compared to the bulk. The spin canting will influence the free energy in the system and furthermore should play a significant role in the surface reactivity posing interesting questions in terms of how to account for the correct magnetic state in the DFT calculations to extrapolate the thermodynamic free energies to relevant temperature and pressure conditions. VASP does allow for the use of noncollinear spin densities, but it is in the beta-stage of code production and extra care must be taken when using it for these calculations.

Following previous work in the literature, the present DFT calculations assume the antiferromagnetic state of the bulk material and the surface atoms without including spin canting. Regardless, individual spin states of the Fe atoms will change in magnitude as a function of the layer relaxation, and in this work a Bader charge analysis [17] is used to calculate the individual magnetic moments. Since the charge density is not a quantum mechanical observable, defining the actual value of the atomic charge is not straightforward. Charge partitioning schemes such as the Mulliken population analysis depend on the assignment of the basis set to the atoms, so it is not applicable for plane-wave methods that are needed for periodic structure simulations. Within the approach proposed by Bader the continuous electron density for each spin state is partitioned into volumes based on the steepest decent path such that the flux of the charge density through

the interatomic surfaces vanishes at every point on the surface. The total Bader charge on a point is then found by summing up the contribution from all the points in the corresponding region. The magnetic moment for Fe in the bulk oxide is calculated to be ± 3.5µB, which is lower than

32

Figure 25. Various protonated M2 a-Al2O3 surfaces with (a) (HO)2-(HO)2-Al2-R, (b) (HO)2-Al2-(HO)2-Al2-R, to (c) (H2O)2-(HO)2-Al2-R., where R is the repeating sequence of the stoichiometric structure.

the experimental value of ± 4.6µB [18], but in good agreement with the other DFT calculations [15,19]. The magnetic moment projected on the axis perpendicular to the surface of the Fe in the top layer relaxes to ± 2.8µB which is also consistent with the work of Lo et al. [15].

Conclusions – Density functional theory calculations of clean and protonated ( 0211 ) a-Al2O3 surfaces have been performed, and calculated layer spacing values show reasonable overall agreement with experimental CTR diffraction measurements. A full ab initio thermodynamic calculation is currently underway to investigate the stability of the different surfaces, but preliminary results show that the M2 surface is the most stable, which is consistent with experimental work. Inclusion of hydrogen on the surface and subsurface oxygen atoms is found to stabilize the atomic layers. The oxygenated

surface Al atoms without protonation have a formal charge of III and VI for M1, the surface corresponding to the stoichiometric termination and M2, the surface formed by removing the first layer of metal atoms, respectively. As expected from a charge neutrality standpoint the maximum number of protons that the surface unit a-Al2O3 can have is 3 and 5 for the M1 and M2 surfaces, respectively. In fact, when the M2 surface contains the maximum of 5 hydrogen atoms per unit a-Al2O3 on the surface, the layer spacing matches most closely with the bulk, which is again consistent based on the equivalent charge states.

Initial simulations of the protonated structure of the M1 surface of a-Fe2O3 show reasonable agreement with previous DFT calculations. In both this work and that of Lo et al. [15], the magnetic state of the oxide is assumed to be antiferromagnetic, which is consistent with the behavior of the spin orientation below the Morin transition temperature (TM < 260K). However, this is probably not the most accurate representation either to describe the surface atoms or to extrapolate to higher temperatures in the ab initio thermodynamic calculations. Spin canting should be included to accurately capture the surface reactivity of a-Fe2O3 under relevant temperature and pressure conditions.

References[1] G. Kresse and J. Hafner, Phys. Rev. B 1993, 48, 13115; G. Kresse and J. Furthmuller,

Comput. Mater. Sci. 1996, 6, 15.[2] Blöchl, P. E., Phys. Rev. B 1994, 50 17953; Kresse, G. and Joubert, D., Phys. Rev. B 1999,

59, 1758. [3] J. P. Perdew, K. Burke, and M. Ernzerhof, Generalized gradient approximation made simple.

Phys. Rev. Lett. 1996, 77, 3865.[4] S. H. Vosko, L. Wilk and M. Nusair, Can. J. Phys. 1980, 58, 1200.[5] H. J. Monkhorst and J. D. Pack, Phys. Rev. B 1976, 13, 5188.[6] M. Methfessel and A. T. Paxton, Phys. Rev. B 1989, 40, 3616.

Layer M1-((HO)2-(HO)2-Fe2-R)

VASP Lo et al.15 Δ(1-2) (Å) 1.297 Δ (2-3) (Å) 0.288 0.279 (-19%) Δ (3-4) (Å) 0.848 0.886 (12%) Δ (4-5) (Å) 0.784 0.831 (5%) Δ (5-6) (Å) 0.322 0.320 (-7%) Δ (6-7) (Å) 1.377 1.435 (1%) Δ (7-8) (Å) 0.340 0.340 (-1%) Δ (8-9) (Å) 0.758 0.796 (1%) Δ (9-10) (Å) 0.757 0.795 (1%) Δ (10-11) (Å) 0.347 0.346 (0%)

Table 4. Calculated layer spacing with percent relaxation in parenthesis for a protonated a-Fe2O3 surface.

33

[7] R. L. Blake, R. E. Hessevick, T. Zoltai, and L. W. Finger, Refinement of the hematite structure. Am. Mineral. 1966, 51, 123-129.

[8] R. E. Newnham, and Y. M. de Haan, Refinement of the Al2O3, Ti2O, V2O3 and Cr2O3

structures. Zeits. Kristallogr. 1962, 117, 235-237.[9] C. G. Shull, W. Strauser, and E. O. Wollan, Neutron diffraction by paramagnetic and

antiferromagnetic substances. Phys. Rev. 1951, 83, 333.[10] M. Catti, G. Valerio, and R. Dovesi, Theoretical study of electronic, magnetic, and

structural properties of a-Fe2O3 (hematite). Phys. Rev. B 1995, 51, 7441.[11] G. Rollmann, A. Rohrbach, P. Entel, and J. Hafner, First-principles calculations of the

structure and magnetic phases of hematite. Phys. Rev. B 2004, 69, 165107.[12] H.H. Tippins, Phys. Rev. B 1970, 1, 126.

[13] B T. Fujii, F.M.F. de Groot, G.A. Sawatzky, F.C. Voogt, T. Hibma and K. Okada, Phys. Rev. B 1999, 5, 3195. 

[14] J. Jin, X. Ma, C.-Y. Kim, D.E. Ellis, and M.J. Bedzyk, Adsorption of V on a hematite (0001) surface and its oxidation: Submonolayer coverage. Surf. Sci. 2007, 601, 3082.

[15] C. Lo, K. S. Tanwar, A. M. Chaka, and T. P. Trainor, Density functional theory study of the clean and hydrated hematite ( 0211 ) surfaces. Phys. Rev. B 2007, 75, 075425.

[16] T. P. Trainor, P. J. Eng, G. E. Brown Jr., I. K. Robinson, and M. De Santis, Crystal truncation rod diffraction study of a-Al2O3 ( 0211 ) surface. Surf. Sci. 2002, 496, 238-250.

[17] Henkelman, A. Arnaldsson, and H. Jónsson, Comput. Mater. Sci 2006, 36, 254; E. Sanville, S. D. Kenny, R. Smith, and G. Henkelman, J. Comp. Chem.2007, 28, 899; W. Tang, E. Sanville, and G. Henkelman, J. Phys.: Condens. Matter 2009, 21, 084204.

[18] J. M. D. Coey, G. A. Sawatzky, J. Phys C: Solid State Phys. 1971, 4, 2386; E. Kren, P. Szabo, G. Konczos, Phys. Lett. 1965, 19, 103.

[19] A. Rohrbach, J. Hafner, G. Kresss, Phys. Rev. B 2004, 70, 125426; X.-G. Wang, W. Weiss, Sh. Shaikhutdinov, M. Ritter, M. Peterson, F. Wagner, R. Schlögl, and M. Scheffler, Phys. Rev. Lett. 1998, 81, 1038.

2. Pb(II) adsorption on isostructural hydrated alumina and hematite (0001) surfaces: A DFT study (Sara E. Mason, Christopher R. Iceman, Kunaljeet S. Tanwar, Thomas P. Trainor, and Anne M. Chaka)

The persistence of lead (Pb) in contaminated topsoil is ranked as one of the most serious environmental issues in the U.S. and other countries. Adsorption of Pb at the aqueous interface of nanoscale metal oxide and metal (oxy)hydroxide particles is perhaps the most significant process responsible for controlling contaminant sequestration and mobility, but the process is poorly understood at the molecular level. Experimental studies of absorption of Pb(II) onto bulk minerals have indicated significant differences in reactivity, but the molecular basis for these differences has remained elusive due to the challenges of observing and modeling the complex chemistry that exists at the metal−oxide/water interface. In this work, we present a detailed ab initio theoretical investigation aimed at understanding the fundamental physical and chemical characteristics of Pb adsorption onto the (0001) surface of two common minerals, α-Al2O3 and α-Fe2O3. The results of our periodic density functional theory (DFT) calculations show that the adsorption energy of Pb(II) on hematite is more than four times the value on isostructural alumina with the same fully hydroxylated surface stoichiometry due to bonding interactions enabled by the partially occupied Fe d-band. Site preference for Pb(II) adsorption on alumina

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(Fig. 26) is shown to depend strongly on the cost to disrupt highly stable hydrogen bonding networks on the hydrated surface, but is less of a factor for the stronger Pb-hematite interaction.

Figure 26. Top views of the optimized Pb/M2O3 geometries on the 1D2U H-bonded surfaces. Al, Fe, O, H, and Pb are shown in magenta, light gray, red, white, and dark gray, respectively. Pb−O bonds are drawn in green, and rPb−O distances are labeled (in Å). Structure names, values of Eads, and the shortest Pb−M separations are indicated in each panel (from [1]).

Reference[1] Mason, S. E., C. R. Iceman, K. S. Tanwar, T. P. Trainor, and A. M. Chaka, Pb(II) adsorption on isostructural hydrated alumina and hematite (0001) surfaces: A DFT study. J. Phys. Chem. C 2009, 113, 2159-2170.

G. Dynamics of Biofilms at Solid-Aqueous Solution Interfaces, and Molecular Genomics and Biofilm Physiology (Spormann et al.)

As part of this NSF EMSI project, we have developed a better fundamental understanding of the cellular and environmental factors required for electron transfer in the model Fe(III)-reducing bacterium Shewanella oneidensis MR-1. We used physiological, genetic, and biochemical approaches. The key findings of our work can be summarized as follows:

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(1) Fe(III) reduction can occur at multiple cellular sites and shows great variability with respect to the solubility of the Fe(III). CymA was discovered to be a previously unidentified ferric reductase.

(2) CymA appears to act as an electron transfer switch with specific interactions to terminal oxidoreductases in the periplasm, such as nitrate reductase, fumarate reductase, and MtrA. This finding is based on mutational analysis of CymA.

(3) The periplasm contains a network of redox-active proteins, which results in a significant pool of promiscuously transferred electrons in this cytochrome system. This system seems to amount to a periplasmic, ‘delocalized’ electron storage that may have important implications for electron transfer to redox-active minerals.

(4) There is genetic redundancy in Shewanella species, which provides a unique biological means for evolvability of new electron-transfer processes. These findings are based on suppressor studies.

(5) The mxd genes play key roles in mediating cell contact to insoluble Fe(III) minerals during catabolic electron transfer.

(6) The mxd genes are controlled primarily by the cellular growth state, where in slow or non-growing populations, the operon is expressed.

Collectively our findings reveal a picture of a microbe-mineral redox interaction in which Shewanella uses a partially redundant cytochrome network to mediate electron transfer to Fe(III), while differences in the pathways exist depending on the Fe(III) solubility and complexation state. Cell contact to a surface is mediated by the mxd genes and is most pronounced when cells are carbon-starved. Moreover, Fe(III) reduction may not be a continous process but occurs in discrete steps depending on the interaction surface and duration of the organism and the mineral.

1. Genome-level respiratory plasticity as revealed by insertion sequence-mediated adaptive evolution in Shewanella oneidensis MR-1 (Carmen Cordova, Yang Yu, Alfred M. Spormann)

Genome evolution in prokaryotes involves genomic rearrangements by insertion sequence – mediated integration into the chromosome or recombination-linked inversions/deletions. The genome of S. oneidensis MR-1, metal-reducing bacterium abundantly present in sediments and soil, encodes for over 200 transposases as well as a split superintegron, which has activity in acquiring foreign genes. In this study, we report the expansion of the function of non c-type cytochromes in the respiratory pathways of S. oneidensis MR-1 through insertion sequence (IsSOD1)-mediated expression. Shewanella oneidensis MR-1 utilizes a complex electron network primarily of c-type cytochromes, as well as iron-sulfur proteins, molybdoenzymes, and flavins to respire a variety of compounds under anaerobic conditions, including Fe(III) and Mn(IV) present in a mineral phase. Critical to several respiratory pathways is CymA, a cytoplasmic membrane bound tetraheme c-type cytochrome that is believed to transfer electrons from the quinol pool to different periplasmic oxidoreductases. In order to fully understand the path of electron transfer from CymA to external electron acceptors, we previously constructed various CymA alleles to investigate intramolecular and intermolecular electron flow. During experimentation involving non-functional CymA alleles, we identified a ΔcymA suppressor mutant that is capable of CymA-independent respiration on electron acceptors previously linked to CymA-dependent respiratory pathways such as fumarate, nitrate, DMSO

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and ferric citrate. Through molecular, biochemical, and genetic analysis we established that the complex NrfCD had functionally replaced CymA in the electron transfer network. NrfD, a nine transmembrane integral membrane protein, is a functional homolog to CymA and forms a complex with the periplasmic iron sulfur protein, NrfC; however, it had not been previously shown that this complex could act as a respiratory branching point. In addition, we found that expression of NrfCD was activated due to the upstream insertion of a mobile genetic element (IsSOD1), which belongs to the IS3 family of insertion sequences. We also showed that the rewiring of the electron transfer pathways in the S. oneidensis in the suppressor strain involves differential regulation of global regulators that have been implicated previously in respiratory pathway control under anaerobic conditions. Our work here illustrates that an alternative route of electron transfer independent of CymA can evolve rapidly. This study exemplifies how IS element-mediated expression enables microorganisms to rapidly access novel functions in enzymes already present in their genomes.

H. Environmental Applications

1. Environmental chemistry of arsenic (Fendorf Group)Despite the severe health effects arsenic is causing globally, the processes governing

aqueous concentrations remain unresolved, limiting our ability to predict arsenic concentrations in space (between wells, for example) and time (future concentrations) as well as preventing an assessment of the impact of human activities on the arsenic problem. We have been conducting both laboratory and field research as part of the Stanford EMSI program to address the fate- controlling processes of arsenic. (Appendix E contains an article in the March 24, 2009 issue of the Stanford Report on research by the Fendorf Group on arsenic poisoning in Asia.) Our work over the past year illustrates several important aspects of arsenic biogeochemistry controlling its fate and transport and can be summarized in three major points (elaborated upon below). First, on a thermodynamic basis, As(V) reduction is more favorable than that of Fe(III) and thus is likely the initial step in As release to pore-water under anaerobic conditions. Second, while As may be sequestered through incorporation in secondary iron oxides, the solubility of discrete As(III)-Fe(II) precipitates is not a major pathway limiting its dissolved concentrations. Third, heterogeneous pore sizes common to soils and sediments lead to arsenic partitioning along flow boundaries that are subject to rapid pulses of dissolution upon shifts from aerobic to anaerobic conditions.

a. Thermodynamic constraints on arsenic and iron reduction (Ben Kocar and Scott Fendorf)

Reduction of As(V) and Fe(III) are generally postulated to transpire at similar redox potentials, but the reduction sequence, viewed through production of dissolved As(III) and Fe(II), varies (see, e.g., [1]). While kinetic factors may often determine observed Fe(III) and As(V) reduction, thermodynamic viability has an overriding control on whether a reaction can proceed and on the energy yield for respiration. At present, there is a paucity of data concerning the thermodynamic favorability of processes representative of field conditions. We therefore performed a thermodynamic evaluation of Fe(III)-(hydr)oxide and As(V) reduction; sulfate reduction may also impact the fate of both As and Fe, and we thus include this redox active constituent in our analysis. To place our thermodynamic calculations in the direct context of field conditions, we evaluated reaction favorability(s) using solid and aqueous phase measurements

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from a field site in Cambodia, where As release from shallow (< 4m) sediments is known to occur (see [2,3]).

Hydrogen, acetate, and lactate were evaluated as electron donors based on the partial equilibrium approach for examining electron donor and acceptor utilization within sediments [4,5]. The partial equilibrium approach assumes that the rate-limiting step driving biogeochemical reactions is the fermentation of organic matter, and that the kinetics of fermentation, and resulting production of low molecular weight carbon species (e.g., acetate, lactate, etc.) and hydrogen are slow compared to the kinetics of TEA reduction. The electron- accepting processes are therefore close to equilibrium, while organic matter fermentation is not.

Under standard-state conditions, the Gibbs free energy of reaction for ferrihydrite and singly protonated arsenate (HAsO4

2-) are the most favorable on a per mol electron donor basis for hydrogen, acetate, and lactate oxidation, followed by goethite, hematite, di-protonated arsenate (H2AsO4

2-), and finally, sulfate reduction. However, the driving force for reaction will depend not only on the intrinsic reaction favorability (standard-state conditions) but also on the concentration gradients established by the reactants and products, such as Fe2+ accumulation during Fe-(hydr)oxide reduction. The Gibbs free energy of reaction for As, Fe, and S reduction, for example, will change by ~10 kJ/mol with each 100-fold change in acetate concentration; changing the product concentrations of each reaction, including As(III) (As reduction), Fe2+ (Fe reduction), HS- (sulfate reduction), and acetate (lactate oxidation) will also decrease the favorability of each reaction accordingly.

On the basis of the Gibbs free energy calculated for reaction conditions, As(V) (either HAsO4

2- or H2AsO4- at circumneutral pH, pKa2 = 6.8) reduction is the most favorable reaction

across a range of As, H2, lactate, acetate, and pH values representative of possible field conditions. Ferrihydrite reduction is the only process for solid-phase iron-(hydr)oxide reduction, which yields similar Gibbs free energy to As(V) reduction; ferrihydrite reduction, however, is more favorable than As(V) reduction only at high As(III):As(V) ratios, and the relative favorability diminishes markedly at Fe2+ activites greater than 8 x 0 (). On a thermodynamic basis, As reduction is therefore generally expected to occur regardless of the presence of reducible Fe(III)(s) or sulfate, and will likely only be inhibited in the presence of high O2 or NO3

-.

Thus, our analysis illustrates that with the exception of very low As(V) and Fe(II) activities, As(V) reduction is more favorable than reduction of Fe(III) in goethite and hematite, and is more favorable than ferrihydrite reduction above (Fe2+) of ~1.0 x 10-5 (M). Details of the analysis and findings can be found in [6].

b. Controls on arsenic solubility within anaerobic environments (Ben Kocar and Scott Fendorf)

In soils and sediments, reductive dissolution and transformation of Fe(III)-(hydr)oxides have long been considered to trigger As release under anaerobic conditions; however, recent studies show that reductive biomineralization can sequester As. Formation of Fe(II)-As(III) solids has been proposed as a potential mechanism of As sequestration under anaerobic conditions, and, in fact, a solid of this type has been observed by abiotic reaction of Fe(II) with

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As(III) [7]. However, the conditions favorable for formation of an Fe(II)-As(III) precipitate and long-term stability of this phase are unknown. Further, the precise composition of this solid in addition to its (stoichiometrically consistent) structure is unknown. To understand the environmental conditions required for the formation of an Fe(II)-As(III) precipitate and its control on dissolved arsenic concentrations, the composition, structure, and solubility of the Fe(II)-As(III) precipitate were investigated. We found that the Fe(II)-As(III) precipitate has a composition of H7Fe4(AsO3)5 with a log Kso=33.97 for the following dissolution reaction (1):

H7Fe4(AsO3)5 + 8H+ = 4Fe2+ + 5H3AsO3 (1)

The Fe(II)-As(III) precipitate has a pH dependent solubility and requires millimolar concentrations of dissolved Fe(II) and As(III) at pH < 7.5. Hence, it is unlikely that this phase controls As concentrations except in “extreme” environments having either a low pH (pH < 4) and/or millimolar As(III) concentrations.

c. Influence of soil physical structure on arsenic fate (Yoko Masue-Slowey, Celine Palud, Kate Tufano, Sean Benner, Ben Kocar, Matthew Marcus (LBNL), Peter Nico (LBNL), and Scott Fendorf)

A multitude of biogeochemical processes may impact the fate of As and, as a consequence of the physical complexity within soils, they may vary at the sub-micron scale [8]. Soils are structured media having a multitude of pore domains that result in advective and diffusively controlled solute transport. Solutes move rapidly via advection along preferential flow paths (e.g., aggregate exterior) and slowly via diffusion into intra-aggregate pore space. As a consequence primarily of diffusion-limited oxygen egress combined with biological demand, aggregate interiors are typically more chemically reducing than exterior regions—even in aerated soils, aggregates may become reducing within a few millimeters of the exterior [9]. However, the role of soil physical complexity on biogeochemical heterogeneity impacting the fate and transport of As are unresolved. Accordingly, we investigated the development of As and Fe geochemical gradients within Fe containing aggregates, and evaluated the importance of As(V) and Fe(III) reduction processes under anoxic and aerated advecting solute conditions. To resolve the role of soil physical structure on As transport, we examined As desorption from constructed aggregates—a fundamental unit of soil structure. Spherical aggregates were made with As(V)-bearing ferrihydrite-coated sand inoculated with Shewanella sp. ANA-3 and placed in a cylindrical reactor; advective flow of anoxic or aerated solutes was then initiated around the aggregates.

Role of Anaerobiosis within Mass-Transport Limited Aggregate. We have shown that physical heterogeneity common to soils and sediments will have a strong influence on the biogeochemical conditions controlling the fate and transport of As. Even within aerated soils, anaerobiosis within aggregates, or any diffusion-controlled environment, will result in As(V) and Fe(III) reduction. Importantly, accumulation of As near the advective flow boundary under aerated conditions could accelerate As release upon the onset of full anaerobic conditions. Additionally, an increased As/Fe molar ratio within the aggregate interior under aerated flow also suggest an increased potential for As release upon continuation of the reactions. Once As occupancy reaches their maximum as Fe continue to dissolve, As may start diffusing toward the aggregate

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exterior and the advective flow domain. Although our experimental system demonstrates the importance of physical heterogeneity, we must also recognize the complexities of microbial processes and distribution of organic carbon in soils. Development of redox gradients within intra-aggregate space may be restricted in subsurface soils, where carbon delivery replies on the preferential flow along inter-aggregate macropores. Further, in the presence of As(III)-oxidizers under aerated or nitrate-reducing conditions, As(III) diffusion from intra-aggregate space into inter-aggregate macropores could be oxidized, promoting As retention. Ultimately, site-specific chemical, biological, and physical complexities must be considered to understand and predict arsenic fate and transport.

Intra-aggregate Redistribution and Transformation of As and Fe under Aerated Flow. An anaerobic center exists within aggregates under aerated flow as the rate of oxygen consumption via aerobic respiration exceeds the rate of oxygen diffusion into the aggregate. As a result, the aggregate exterior remains aerated while the mid-section and interior become anaerobic. Although redistribution of As and Fe was minimum during first 20 d, drastic changes in As and Fe content were observed by 52 d. Three discrete zones of As and Fe result due to difference in redox status and diffusion gradients: accumulation of As and Fe in the exterior, depletion of As and Fe in the mid-section, and no change in As, despite the loss of Fe, in the interior section.

During the initial 20 d, As did not accumulate in the aggregate exterior, likely due to desorption of labile As and an insufficient supply of Fe(II) from the aggregate mid-section and interior to induce As retention with ferrihydrite transformation products (goethite and magnetite). After an initial period of As(V) desorption, depleting a small labile fraction of As(V) consistent with outer-sphere complexes noted by Catalano et al. [10], the remnant As(V) remains strongly partitioned on the solids, consistent with desorption trends for advective flow columns [11]. During this time, initial transformation of ferrihydrite to magnetite in the mid-section and interior of the aggregates likely consumes Fe(II) and thus limits its diffusion into the aggregate exterior.

Both As and Fe accumulated in the exterior region of the aggregate after 52 d of reaction, illustrating a large internal redistribution of both elements within the aggregate. Arsenic and Fe lost from the internal regions redistributes in the aerated exterior, as noted by the loss of Fe from the mid-section and interior and the loss of As from the mid-section. Migration of Fe toward the exterior results from reductive dissolution in the interior and oxidative (re)precipitation of Fe(III) hydroxides in the exterior, maintaining a diffusion gradient. Arsenic(III) accumulation in the exterior is likely due to incorporation within the reprecipitating Fe solids rather than re-adsorption onto ferrihydrite since the latter moieties tend to desorb with changes in solute levels [11]. An abrupt change in the dominant As speciation from As(V) to As(III) 3 mm from the aggregate exterior is consistent with the zone of Fe accumulation, indicating oxygen is maintained as the dominant electron acceptor for microbial respiration in the outer rim of the cortex (0-3 mm) and would likewise be conducive to Fe(II) oxidation. Unlike Fe(II), As(III) oxidation by molecular oxygen is slow [12] and thus As(III) is likely to remain within the oxygenated zone. Within the mid-section, the appreciable loss of Fe coupled with a diffusional gradient established by As(III) binding with reprecipitating Fe(III) solids in the exterior results in a depletion of As. The mid-section lost 0.004 mmol As and 0.102 mmol Fe, and the proportion of As(III), relative to As(V), increased over time up to 88 % after 52 d.

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In the interior region of the aerated aggregate, Fe loss is prominent; however, no change in As content is noted. The elevated As/Fe molar ratio is in part due to As association with newly formed magnetite, a reductive sequestration process also found in the mid-section and interior of the aggregate under anoxic flow. The highest amount of magnetite (15 mole % Fe) was measured within the interior of aggregate under aerated flow. Temporal increases in magnetite within aggregate mid-section and interior are likely due to gradual increase in pore-water Fe(II) concentration.

Arsenic desorption and release to advecting water was similar between anoxic and aerated systems for the first 20 d; thereafter, the anoxic advecting solutes increased As release relative to the aerated counterpart. With aerated advecting solutes, Fe(III) remained oxidized, or was oxidized, in the cortex of the aggregate, forming a ‘protective’ barrier that limited As release to the advective channel. However, anaerobiosis within the aggregate interior, even with aerated flow, ultimately promotes internal re-partitioning of As to the exterior region; due to As(V) and Fe(III) reduction in the interior, As diffuses and is retained proximal to the advecting flow domain. Further details on arsenic migration and repartitioning within physically complex media representative of soils and sediments are provided in Masue-Slowey et al. [13] and Tufano et al. [11,14], and additional information on iron transformations are noted in Pallud et al. [15].

References[1] Islam, F. S.; Gault, A. G.; Boothman, C.; Polya, D. A.; Charnock, J. M.; Chatterjee, D.;

Lloyd, J. R., Role of metal-reducing bacteria in arsenic release from Bengal delta sediments. Nature 2004, 430, 68-71.

[2] Kocar, B.; Polizzotto, M.; Benner, S.; Ying, S.; Ung, M.; Ouch, K.; Samreth, S.; Suy, B.; Phan, K.; Sampson, M.; Fendorf, S., Integrated biogeochemical and hydrologic processes driving arsenic release from shallow sediments to groundwaters of the Mekong Delta. Appl. Geochem. 2008, 23(11), 3059-3071.

[3] Polizzotto, M.; Kocar, B. D.; Benner, S. B.; Sampson, M.; Fendorf, S., Near-surface wetland sediments as a source of arsenic release to ground water in Asia. Nature 2008, 454, 505-508.

[4] Postma, D.; Jakobsen, R., Redox zonation: Equilibrium constraints on the Fe(III)/SO4-

reduction interface. Geochim. Cosmochim. Acta 1996, 60(17), 3169-3175.[5] Postma, D.; Larsen, F.; Hue, N. T. M.; Duc, M. T.; Viet, P. H.; Nhan, P. Q.; Jessen, S.,

Arsenic in groundwater of the Red River floodplain, Vietnam: Controlling geochemical processes and reactive transport modeling. Geochim. Cosmochim. Acta 2007, 71, 5054-5071.

[6] Kocar, B.D.; Fendorf, S., Thermodynamic constraints on reductive reactions influencing the biogeochemistry of arsenic in soils and sediments. Environ. Sci. Technol. 2009, 43, 4871-4877.

[7] Thoral, S.; Rose, J.; Garnier, J. M.; van Geen, A.; Refait, P.; Traverse, A.; Fonda, E.; Nahon, D. Bottero, J. Y., XAS study of iron and arsenic speciation during Fe(II) oxidation in the presence of As(III). Environ. Sci. Technol. 2005, 39, 9478-9485.

[8] Tokunaga, T. K.; Wan, J. M.; Hazen, T. C.; Schwartz, E.; Firestone, M. K.; Sutton, S. R.; Newville, M.; Olson, K. R.; Lanzirotti, A.; Rao, W., Distribution of chromium contamination and microbial activity in soil aggregates. J. Environ. Qual. 2003, 32, 541-549.

[9] Sexstone, A. J.; Revsbech, N. P.; Parkin, T. B.; Tiedje, J. M., Direct measurement of oxygen profiles and denitrification rates in soil aggregates. Soil Sci. Soc. Am. J. 1985, 49, 645-651.

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[10] Catalano, J. G.; Zhang, Z.; Park, C. Y.; Fenter, P.; Bedzyk, M. J,. Bridging arsenate surface complexes on the hematite (012) surface. Geochim. Cosmochim. Acta 2007, 71, 1883-1897.

[11] Tufano, K. J.; Reyes, C.; Saltikov, C. W.; Fendorf, S., Reductive processes controlling arsenic retention: Revealing the relative importance of iron and arsenic reduction. Environ. Sci. Technol. 2008, 42, 8283-8289.

[12] Inskeep, W. P.; McDermott, T. R.; Fendorf, S., In Environmental Chemistry of Arsenic; Frankenberger, W. T., Eds.; Marcel Dekker: New York, 2002, pp 183-215.

[13] Masue-Slowey, Y.; Kocar, B. D.; Pallud; C.; Fendorf, S., Dependence of arsenic fate and transport on biogeochemical heterogeneity arising from physical structure of soils and sediments. Environ. Sci. Technol. (2009, submitted).

[14] Tufano, K.T.; Benner, S.G.; U. Mayer, K.; Marcus, M.A.; Nico, P.S.; Fendorf, S., Aggregate-scale heterogeneity in iron (hydr)oxide reductive transformation. Vadose Zone J. (2009, in press).

[15] Pallud, C.; Masue-Slowey, Y.; Fendorf, S., Aggregate-scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from coupled biogeochemical and physical processes. Geochim. Cosmochim. Acta (2009, submitted).

2. Aluminum reactions with silica in soils and sediments (Myneni Group)Aluminum is one of the eight most abundant elements found in our planet, and it forms

all of the most commonly occurring Al-silicates in rocks, soils and sediments. In all these materials, Al exist primarily either in the tetrahedral or octahedral coordination environment with O2- or OH- ions. In some minerals, such as in micas and clay minerals, tetrahedral Al coexists with octahedral Al in small concentrations (to a maximum of 25%), and the concentration of tetrahedral Al decreases with progressive weathering of these minerals (for example, among clays or micas, muscovite contains the highest concentration of tetrahedral Al, and clay minerals pyrophyllite and kaolinite contain none). Thus minerals with purely tetrahedral Al are rare or absent in all weathering environments. In the last 3 years we have been examining the coordination chemistry of inorganic and organic complexes of Al in aqueous solutions, and its reactions with different solids. We are using this information from simple model systems to evaluate the nature of Al in different soils and sediments. As described later (and contrary to the popular opinion), our recent X-ray microscopy and X-ray scattering studies indicate that Al in tetrahedral coordination is very common in natural environments.

All of the silicates, oxyhydroxides and hydroxides of Al found in all weathering environments exhibit Al in primarily octahedral coordination. Minerals reported to contain only tetrahedral Al are Na-Al-silicate, albite (a high temperature phase common in igneous and metamorphic rocks), and Al-phosphates (in both crystalline and amorphous phases). However, bulk soil and sediment diffraction studies and mineral dissolution studies indicate that albite weathers rapidly when exposed to water, and it is not known to exist in highly weathered soils and sediments. Similarly, the phosphate ion concentration in most soils and sediments is not high enough to precipitate Al-phosphates.

However, our recent X-ray microscopy studies of several highly weathered soils, freshwater lake sediments, and shallow and deep marine sediments indicate the abundance of nanoparticles with only tetrahedral Al (see Fig. 27). The distribution of these particles in soils and sediments vary from less than 1% to as high as 5%, and their sizes are mostly in the

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nanometer region with the largest particle in the size range of 1-2 microns. From the soft X-ray spectroscopy and microscopy studies we learned that these particles also contain high quantities of Si with minor quantities of Na, suggesting that this is some type of a Na-Al-silicate. The Al- and Si-XANES spectral features of these phases also indicate that their structure is close to that of albite, with significant variations in the energies for different electronic transitions. Based on these preliminary studies we are hypothesizing that this newly identified phase is a hydrated form of Na-Al-silicate with varying degrees of crystallinity, and the nanometer size of these particles makes them thermodynamically stable under these ambient P-T conditions. If not for these nanometer size ranges, these phases would not have been stable. We are in the process of analyzing the X-ray scattering data to evaluate the structures of these new phases.

Figure 27. (left) Scanning Transmission X-ray Micrograph of freshwater lake sediment at the Al K-edge. Brightest regions in the image shown on the left indicate the concentration of tetrahedrally coordinated Al. The scale bar is 1 M. (right) Al-XANES spectra are for different particles, which show either purely tetrahedrally coordinated Al (green and red spectra), or both tetrahedral and octahedrally coordinated Al (blue and purple spectra) in different parts of the image. The peak around 1566 eV in the Al-XANES spectra indicates the presence of tetrahedral Al, while the octahedral Al indicates the transitions around 1568-1572 eV. Corundum (a-Al2O3), with only octahedral-Al, is an exception to this energy range, but it is absent in weathering environments.

3. Environmental chemistry of mercury in mercury mining environments (Adam D. Jew, Mae S. Gustin (University of Nevada, Reno), James J. Rytuba, Christopher S. Kim (Chapman University), Ruben Kretzschmar (ETH-Zurich), and Gordon E. Brown, Jr.)

Although significant progress has been made in understanding the speciation and cycling of Hg in Hg mineralized regions such as the California Coast Range, there is still much to learn about the biogeochemical processes affecting the speciation, transformations, and cycling of Hg, particularly (1) the abundance of Hg(0) in contaminated soils, sediments, and mine wastes, (2) its impact on atmospheric evasion of Hg, (3) the extent of sorption of Hg(II) on Fe(III)-oxyhydroxides and NOM in such settings, (4) microbial processes that enhance HgS solubility, and (5) correlations between Hg speciation and Hg stable isotope fractionation. During the past year, we have made significant progress in areas (1), (2), and (4) and have initiated new studies in areas (3) and (5), which will be continued during the next year.

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During the past year, we developed a liquid-N2 sample stage for EXAFS spectroscopy studies of complex Hg-mine wastes, and a protocol for slowly crystallizing Hg(0) liquid to crystalline a-Hg. In preliminary studies using this new sample stage and sample preparation protocol, we have succeeded in detecting and quantifying Hg(0) in samples taken from various Hg mine sites [1,2]. Mercury is a liquid at room temperature, and the structural disorder of the liquid results in a poorly defined EXAFS spectrum of Hg(0) (Fig. 28). Thus our previous ambient-T EXAFS studies of Hg-mine wastes [3] failed to detect Hg(0) in such samples. The freezing point of Hg(0) is -38.83°C, so by freezing Hg(0)-containing samples slowly in LN2 and measuring their EXAFS spectra at 77 K using the specially built sample cryostage at SSRL BL 11-2, we have been able to obtain an excellent EXAFS spectrum of Hg(0) (Fig. 28). Quenching the sample in LN2, as is typically done when using a liquid He cryostat for EXAFS, produces Hg(0) glass with the same weak EXAFS intensities as liquid Hg(0). However, using our new sample preparation protocol and low-T sample stage, we can now conduct EXAFS spectroscopy studies of Hg(0) in complex mine-wastes at concentrations > 50 ppm because of the fact that the low-T Hg(0) LIII-EXAFS spectrum is out of phase with the Hg L III-EXAFS spectra of cinnabar, metacinnabar, and other Hg-bearing phases (Fig. 29). Using this new approach, we propose to reanalyze mine waste samples from the Hg mines in the California Coast Range listed above. Preliminary low temperature EXAFS work on samples from several of these sites has shown that some Hg mine wastes contain up to 25% elemental Hg. The results of these studies will be important in evaluating Hg-contaminated sites in the California Coast Range for possible remediation actions and in understanding Hg cycling.

This new low-T EXAFS speciation method for quantifying Hg(0) in environmental samples has important implications for understanding Hg evasion into the atmosphere from Hg-contaminated mine wastes and soils. We have collaborated with Prof. Mae Gustin of the University of Nevada, Reno on relating Hg evasion from mine wastes into the atmosphere, but our earlier ambient-T EXAFS studies could not detect Hg(0) in such wastes. Fluxes of Hg released from samples following exposure to light vs. dark periods were measured by Prof. Gustin on Hg-mine waste samples on which we have carried out EXAFS analysis of Hg speciation. Results were then normalized to Hg concentration and particle surface area. Large differences between the flux ratio of Hg released after light exposure to Hg released in the dark could not be explained by total Hg alone or by the Hg-containing species we detected in these

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Figure 28: Effect of low temperature (77K) on the L3-edge EXAFS spectrum of elemental Hg.

Figure 29. Low-temperature (77K) EXAFS spectra of cinnabar, metacinnabar, and elemental Hg.

earlier studies (Fig. 30). However, our new low-T EXAFS results show that there is a good correlation between light/dark flux of Hg and the amount of Hg(0) in samples, with two trends observed relating to the type of Hg deposit (Fig. 30).

Cinnabar and metacinnabar are often considered to be the most stable forms of Hg and of little or no environmental hazard. Under general conditions, cinnabar and metacinnabar have stability constants of 10-53.3 and 10-52.7, respectively. Numerous studies have been carried out on the stability of HgS in the presence of organic matter and sulfide, but these studies were conducted under neutral to basic pH conditions that are quite reducing and thus far from those at

Hg mine sites. A few studies have been carried out on bacterial interactions with HgS, but these studies used HgS to stress or sterilize the bacterium instead of determining how bacteria interactdirectly with HgS [4,5]. The Brown group has initiated a study of the effect of a bacterial consortium found in the New Idria Hg mine AMD system on the dissolution of HgS. Because HgS dominates the waste material at abandoned Hg mine sites in the California Coast Range, it is important that we understand its stability in AMD systems. Thermodynamically, S-oxidizing bacteria should be able to use HgS for energy by oxidizing S in an aerobic environment, but this suggestion has not been proven. The biggest hurdle with bacterial oxidation of HgS is the high level of Hg released when HgS starts dissolving and its effect on the bacteria. However, the main Hg detoxification pathway using mer genes is quite efficient at detoxifying Hg and is quite widespread [4]. The importance of the resistance pathway is that bacteria with high Hg resistance, such as those from Hg mine AMD sites, should be capable of dissolving relatively insoluble HgS, releasing Hg into the environment in a dissolved and highly reactive form.

Our preliminary study of the effect the New Idria AMD bacterial consortium has on HgS,

[Fe(II)], [HS-], carbon, and community diversity within the AMD system has produced intriguing results. Several bacterial 16S rRNA clone libraries of the New Idria biofilm have been created at several different times to determine the dominant species present and to screen for a potential bacterium responsible for HgS dissolution. The clone libraries generally consist of Fe-oxidizing species as the dominant groups of bacteria, containing 65-75% of the clones for the three

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Figure 30. Hg flux (light/dark ratios) vs. total Hg (ppm) (left) and % elemental mercury (right).

different years we have sampled the bacterial consortium at the New Idria AMD site. We found a single bacterium capable of oxidizing S that is 97% similar to the heterotrophic Thiomonas sp. Even though the isolate has similarities to other Thiomonas, such as being acidophilic and only being able to use complex carbon sources [6], the isolate from the New Idria AMD site is capable of growing at pH of 0 to 7 and Hg concentrations of at least 20 ppm. Even though studies of isolate interactions with HgS have not begun; the HgS dissolution study using the AMD community is yielding interesting results. The experiment consists of exposing the AMD biofilm material to four mineral substrates (cinnabar, metacinnabar, tailings, and calcine material) incubated in water from the field site and filtered initially through 0.2µm and then 0.1µm filters to sterilize the water. The results of our preliminary experiments on the effect of the Thiomonas sp. isolate on dissolution of the four different types of Hg-containing solids under aerobic conditions are shown in Figure 31.

Figure 31. [Hgt] as a function of incubation time under aerobic conditions with living cells inoculated. Mass of protein added was 7.88 µg. Error bars are smaller than symbols, with all errors ≤ 5%.

References[1] Jew, A. D., Kim, C. S., Rytuba, J. J., Gustin, M. S., and Brown, Jr., G. E., EXAFS of frozen

elemental mercury and its implications for abandoned mercury mine wastes. (abstract) Abstracts and Program of 2008 LCLS/SSRL Users Meeting and Workshops, October 15-18, 2008, SLAC National Accelerator Laboratory, Menlo Park, CA, p. 96, 2008.

[2] Jew, A. D., Kim, C. S., Rytuba, J. J., Gustin, M. S., and Brown, Jr., G. E., EXAFS of frozen elemental mercury and its implications for abandoned mercury mine wastes. (abstract) Abstracts of 9th International Conference on Mercury as a Global Pollutant, Guiyang, China, June 7-12, 2009.

[3] Kim, C. S., Rytuba, J. J., and Brown, Jr., G. E., Geological and anthropogenic factors influencing mercury speciation in mine wastes. Appl. Geochem. 2004, 19, 379-393.

[4] Barkay, T., Miller, S. M., and Summers, A. O., Bacterial mercury resistance from atoms to ecosystems. FEMS Microbiol. Rev. 2003, 27, 355-384.

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[5] Baldi, F. and Olson, G. J. (1987) Effects of cinnabar on pyrite oxidation by Thiobacillus ferrooxidans and cinnabar mobilization by mercury-resistant strain. Appl. Environ. Microbiol. 1987, 53(4), 772-776.

[6] Moreira, D. and Amils, R.. Phylogeny of Thiobacillus cuprinus and other mixotrophic thiobacilli: Proposal for Thiomonas gen. nov. Int. J. Systematic Bacteriol. 1997, 47(2), 522-528.

I. New Experimental Developments in Synchrotron Radiation-Based Spectroscopies and Micro-Imaging 1. Development of a new ambient pressure XPS spectrometer at the Stanford Synchrotron Radiation Lightsource (Hirohito Ogasawara and Anders Nilsson)

A new ambient pressure XPS system on BL 13-2 has been constructed in the Nilsson-Ogasawara Group based on funding from DOE through the Stanford Institute for Materials and Energy Sciences and Japan for fuel cell catalysis work. The instrument contains a 5-stage differential pumping system in which the 2nd stage contains a new novel cryopanel where the electrons and gases pass through the interior of a cryopump (Figure 32). The electron spectrometer is a Scienta SES 100, which has been modified to incorporate 3 stages of differential pumping. The ambient-pressure XPS endstation at the ALS operates by backfilling the whole stainless steel UHV chamber and therefore suffers from severe difficulties in maintaining a clean sample due to the release of gases from the chamber walls. The new SSRL instrument is designed to achieve much cleaner conditions. The sample is enclosed inside a small gas cell made of titanium, which is a material with less desorption of carbon containing gases, and together with a flow through system allows for simultaneous pumping of the cell, which we anticipate will lead to much cleaner conditions. Because the beamline provides a small focus, we expect that the sample to differential pumping nozzle distance can be shorter which allows for a significantly higher pressure (20 Torr) relative to the ALS instrument (2 Torr).

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Figure 32. (Left) The Nilsson-Ogasawara ambient-pressure XPS system for beamline 13-2 at SSRL. (Right) Schematic drawing of the inside of the main chamber indicating the gas cell with the sample, incoming beam direc-tion, cryopanel, and electron spectrometer.

III. EDUCATION AND OUTREACH ACTIVITIES

A. Stanford EMSI Education and Outreach Activities at Stanford University

1. The 6th Stanford-Berkeley Summer School on Synchrotron Radiation and its Applications in the Physical Sciences

The 6th joint Stanford-Berkeley summer school on synchrotron radiation and its applications in the physical sciences was held on August 17-22, 2008 at the SLAC Linear Accelerator Laboratory. The Stanford-Berkeley summer school is jointly organized by Stanford University, University of California Berkeley, Lawrence Berkeley National Laboratory (LBNL), and the Stanford Synchrotron Radiation Lightsource (SSRL). Anders Nilsson (Stanford) and Dave Attwood (Berkeley) have been the organizers of this one-week summer school since 2001. It alternates between Stanford and Berkeley. The summer school provides lecture programs on synchrotron radiation and its broad range of scientific applications in the physical sciences, visits to SSRL and the Advanced Light Source (ALS) where the students also have the opportunity to psrticipate in research on a beamline. The program is designed to introduce students and postdocs to the fundamental properties of synchrotron radiation and how to understand and use spectroscopic, scattering, and microscopy techniques in various scientific applications.

The 2008 Summer School attracted 42 students from various parts of the world. The students came from diverse fields representing the full community of synchrotron radiation users including atomic and molecular physics, condensed matter physics, surface science, chemistry, material science, environmental science, and biophysics. There were 5 countries represented by the participants, with most of them enrolled for graduate studies in the US. Applicants were chosen based on their academic record and a description on how the use of synchrotron radiation could impact their planned research projects.

The program consisted of 4 days of lectures and one full day visit to the ALS in Berkeley. The morning of the first day consisted of two lectures by Dave Attwood (UC Berkeley) on synchrotron radiation generation, properties, brightness, and coherence. The first lecture provided a strong background for the students to understand how different sources around the world differ in these unique properties and the difference between radiation from bend magnets, wigglers, and undulators. The second lecture was focused on the definition of brightness and coherence and how it affects different imaging experiments. In the afternoon Anders Nilsson (SSRL) gave an introduction and overview of different spectroscopic and scattering techniques that the students will lear about during the week-long school. There was a strong emphasis on what unique types of information the different methods can provide and how they are related to each other. The last lecture on Monday was given again by Anders Nilsson on core-level spectroscopy where he introduced x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, Auger and x-ray emission spectroscopy in terms of creation and decay of core holes. He demonstrated the versatility of the atom-specific information that can be obtained using core levels with examples from surface physics and chemistry, also including new results on liquid water.

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On Tuesday morning Alessandra Lanzara (UC Berkeley) demonstrated how band structure can be probed using angle resolved photoemission spectroscopy. Her lecture included the principles of momentum conservation, symmetry rules, and applications to correlated materials. Berfore lunch there was a lecture on EXAFS with a focus on chemistry presented by Samuel Webb (SSRL). This lecture showed the complimentary information that can be obtained using both the near edge and the extended fine structure with examples from the field of molecular environmental science. On Tuesday afternoon two lectures were given by Mike Toney (SSRL) on x-ray diffraction and scattering. He introduced Braggs Law and reciprocal space and gave scientific examples in materials science and macromolecular crystallography. The second lecture was given on scattering by non-crystalline materials with particular emphasis on surfaces, interfaces, and nanoporous films.

Wednesday was dedicated to a full-day visit to the ALS in Berkeley. In the morning there was a lecture by Tony Warwick (ALS) on synchrotron beam lines. He explained in detail all the components of a monochromator and the principles of gratings and refocusing optics. Before lunch there was a tour of the ALS. In the afternoon the students were divided into small groups and visited specific beamlines of their choice to interact closely with the staff and learn in detailed how different experiments are carried out.

The 4th day started with a lecture by Jo Stöhr (SSRL) on x-ray absorption spectroscopy with a strong emphasis on the near-edge region. He presented the unique spectral-chemical sensitivity and usage of the polarization properties of synchrotron radiation for linear and circular dichroism. Jo Stöhr gave a second lecture on the applications of spectro-microscopy in magnetism using x-ray absorption resonances as contrast. He demonstrated phenomena such as aligment of antiferromagnetic domains, spin injection, vortex dynamics, and x-ray holography. In the afternoon there was a lecture by Dave Attwood on imaging at high spatial resolution with soft x-ray microscopy. This lecture included use of multilayer mirrors and zone plate lenses, with examples from biology and magnetic nanoparticles. The last lecture of the day was devoted to the future potential of x-ray free electron lasers given by Kelly Gaffney (PULSE/SLAC). Here the student could learn about micro-bunching in the SASE process leading to a fully coherent and ultra-short x-ray source that will be realized in 2009 with the Linac Coherent Light Source (LCLS) at SLAC.

The lecture on Friday morning was given by Gordon Brown (Stanford University) on the applications of synchrotron radiation to environmental chemistry. In his lecture he demonstrated how a combination of all the different methods presented during the school can be used to solve different problems of importance to the environment. The last lecture of the school was given by Lars Pettersson (Stockholm University, Sweden) on how to theoretically simulate x-ray and electron spectra using density functional theory. He showed examples taken from molecular interactions on surfaces and in liquid with a special emphasis on water. In the afternoon there was a long discussion about different questions of both general interest but also related to various topic covered in the school moderated by Anders Nilsson, David Atwood, Gordon Brown, and Lars Pettersson. Each student also described their interests in synchrotron radiation and their present research project.

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Funding for this year’s Summer Schools was provided by SSRL, LBNL, and NSF through the Stanford EMSI. All other expenses were covered by student registration fees. The school was part of the outreach activities within the NSF-funded Stanford Environmental Molecular Science Institute and the ERC for EUV Science and Technology.

2. SEMSI Summer Science Teachers Institute on Environmental Chemistry and Environmental Microbiology of Mercury (July 21-24, 2009, Stanford Campus)

The 2009 workshop entitled “Mercury in the Environment” was held at Stanford University on July 21-24 and was attended by 15 high school science teachers from San Francisco Bay Area high schools, one from Washington State, and one from Bangkok, Thailand. We targeted the advertisement to teachers who are interested in new science pedagogy as well as environmental science and chemistry. Stanford EMSI Participants in the 2009 teacher workshop include Dr. Bryan Brown, Dr. Gordon Brown, Dr. Scott Fendorf, Mr. Adam Jew (Stanford graduate student from Gordon Brown’s group), Dr. Ben Kocar (Stanford post-doc in Scott Fendorf’s group), Dr. Jennifer Saltzman, Dr. Aaron Slowey (USGS), and Dr. Alfred Spormann. The workshop schedule is given below.

EMSI Summer Teacher WorkshopJuly 21-24, 2009

TIME DESCRIPTION OF ACTIVITY INSTRUCTIONAL LEAD

TUESDAY, JULY 21

9:00 - 10:00 Welcome and Introductions, including EMSI introduction Jennifer Saltzman, Bryan Brown, Gordon Brown

10:00 - 11:00 Cognitive Apprenticeship TeachingConnecting science research to classroom teaching

Bryan Brown

11:00-11:15 Break11:15 - 12:15 Natural vs. Anthropogenic Sources of Mercury,

Geological Origins, Technological Uses, Human Health Impacts

Gordon Brown

12:15 - 1:00 Lunch1:00 - 2:00 Practice Lesson Plan Writing – 20 second story Bryan Brown2:00 – 2:15 Break2:15 - 3:00 Chemical Principles of Mercury Lecture Scott Fendorf3:00 - 3:25 Problem Set on Mercury Solubility Scott Fendorf3:25 – 3:50 Lesson Design Bryan Brown3:50 - 4:00 Question Cards Jenny Saltzman

TIME DESCRIPTION OF ACTIVITY INSTRUCTIONAL LEAD

WEDNESDAY, JULY 22

9:00 – 9:10 Announcements Jenny Saltzman9:10 – 10:15 Microorganisms and Mercury Lecture Alfred Spormann 10:15 – 10:30 Break10:30 - 11:15 Lesson Development 1 Bryan Brown11:15 - 12:00 Mercury Case Studies: California Coastr Range Mines:

Mercury in Fish: Minamata, Japan Gordon Brown

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12:00 - 12:45 Lunch12:45 – 1:15 Problem Set on Concentration Units Adam Jew1:15 - 2:45 Lesson Development 2 Bryan Brown2:45 – 3:00 Break3:00 – 4:00 New Almaden Mine Trip Introduction Adam Jew4:00-4:15 Question Cards Jenny Saltzman

TIME ACTIVITY INSTRUCTIONAL LEAD

THURSDAY, JULY 23

9:00 - 10:00 Drive to New Almaden 10:00 - 10:30 Why is There Mercury in These Hills? Lecture Gordon Brown

10:30 - 10:45 Sampling Plan and Methodology Review Adam Jew and Aaron Slowey

10:45 - 12:00 Water Sampling (30 minutes at each site) Adam Jew and Aaron Slowey

12:30 - 1:00 Lunch1:00 - 2:30 Trip up to Mine Hill – 1.5 hours Led by Gordon Brown

3:00-4:00 Drive Back to CampusTIME ACTIVITY INSTRUCTIONAL LEAD

FRIDAY, JULY 24

9:00-9:10 Announcements Jenny Saltzman9:10-9:30 Data Review (20 minutes) Aaron Slowey9:30-9:50 Introduction to Laboratories Lecture (20 minutes) Gordon Brown

10:00-11:00 Lab Tours – Tekran, Environ. SEM, X-ray Diffraction, 20 minutes at each station

Adam Jew (Tekran), Bob Jones (SEM), Ben Kocar (X-ray Diff.)

11:15-12:15 Lesson Development 3 Science Team12:15-1:00 Lunch1:00-2:30 Lesson Development 4 Science Team2:30-3:45 Lesson Presentations Teachers and Science Team3:45-4:00 Evaluation Jenny Saltzman

A paper entitled “Translating Science: Examining science teachers' use of science research for classroom teaching” was submitted to Science & Education in July 2009. This manuscript is based on information gathered from teachers who participated in the Stanford EMSI teacher workshops in 2005 and 2006. This work was done by Prof. Bryan Brown, Stanford School of Education, and Dr. Jennifer Saltzman, Stanford School of Earth Sciences.

Abstract: This research project examined the contentious relationship between using new scientific research while teaching basic science concepts to students. We conducted a 2-year qualitative study of 27 science teachers’ perspectives on how to best integrate science research into teaching. We interviewed teachers prior to and after participating in our professional development training. The results of the interviews highlighted the teachers’ reliance on contemporary news reports to provide them new information about research. Additionally, the teachers demonstrated a reliance on the news resources to help them translate science research to young science learners. The implications of this research highlight the need for the science

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community to support science teachers by providing curricular and news resources that are accessible to a diverse student population. 3. SLAC Summer Undergraduate Intern Program

This program is designed to bring in college students from around the U.S. for a summer research experience at SLAC. Several EMSI members have 2009 summer interns as part of this program, which is funded by SLAC.

4. Stanford Summer Undergraduate Research Intern Program

This program internal to Stanford offers funding to Stanford students to participate in research projects at Stanford. Student funding is provided by Stanford University through the Office of the Dean of Undergraduate Studies. Over the past three years, the Stanford EMSI has attracted six undergraduates from this program to work on EMSI-related projects. Three who have worked in the Brown Group include (1) Samia Rogers, who extended her summer research project on mercury distribution in the vicinity of the New Idria Mine, CA in Summer 2006 to an honors thesis during her senior year in 2007 with the Brown Group, (2) Valentina Fontiveros, who worked in the Brown group during Summer 2007 and continued working in the Brown Group in the Fall of 2007 on mercury adsorbed on iron oxide particles at the New Idria Mercury Mine under the mentorship of graduate student Adam Jew, and (3) Patricia Tcaciuc, who was supported by the NSF-EMSI grant, and worked with the Brown group during the summer of 2008 on the synthesis and characterization of ferrihydrites. Patricia, was double major in Chemistry and Environmental Engineering at MIT, and is now a first-year graduate student in chemical oceanography in the Woods Hole-MIT Oceanographic Institute.

5. High School Student Intern Program

In partnership with local high schools in the Stanford Area, Stanford University has a program to provide summer research experiences for high school students. Senior members of the Stanford EMSI have mentored several high school students over the past three years. For example, during Summer 2007, Adam Jew in the Brown group mentored York Wu from a San Jose High School, and York is now an undergraduate at Harvard. During Summer 2008, Phi Luong from a Cupertino High School worked in the Brown Group with Adam Jew as his mentor, and Phi is continuing his work with us this summer. Phi was recently admitted to Stanford University for Fall 2009.

6. Participation of Stanford EMSI Scientists in National and International Meetings

Members of the Stanford EMSI and their students and post-docs presented a significant number of oral presentations and poster presentations at a number of national and international meetings. A listing of many of these presentations is given later in this report (Appendix B).

7. Science Journalist Workshops

The Stanford EMSI held its third annual Science Journalists Workshop on October 24, 2008 for members of the National Association of Science Writers, who were holding their annual meeting at Stanford University in October 2008. By taking advantage of the professional

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organizations we were able to attract a more diverse audience from news agencies of all types. The workshop announcement is given on the next page.

Science Journalists Workshop Announcement

Atoms to Ecosystem: Effects of Contaminants on Humans & the Environment

Offered by the Stanford Environmental Molecular Science Institute(Gordon Brown, Scott Fendorf, Andrea Foster, Adam Jew, Anders Nilsson, Jennifer Saltzman)

October 24, 2008

The workshop will begin with an introduction to the Environmental Molecular Science Institute by its director, Gordon Brown. The institute’s focus is chemical and microbiological interactions at solid-aqueous solution interfaces in Earth’s near-surface environment, where natural waters, natural organic matter, and biological organisms interact with natural solids and environmental contaminants. Although the field of surface chemistry is approaching 200 years old, rudimentary models dominate the molecular description of solid-aqueous solution interfaces and abiotic and biotic environmental interfacial reactions. Such reactions have played key roles in shaping the geosphere and biosphere of Earth throughout much of geologic time and now help mediate anthropogenic impacts on the environment. Molecular-level understanding of environmental interfaces is needed to help mitigate these impacts through better predictive models and improved remediation strategies.

To begin the in-depth focus on mercury in the environment, a curiosity-driven experiment by Gordon Brown and graduate student Adam Jew will be presented. Brown cooked different samples of two yellowfin tuna for different lengths of time, followed by analysis of the mercury content of these samples by Jew. The hypothesis that Brown and Jew were testing is that cooking tuna reduces its mercury content due to the volatility of methylmercury – the most abundant and toxic species of mercury in tuna. Brown will present his new data, which addresses this hypothesis. You will have to attend the workshop to find out if eating sushi is worse than eating canned (and cooked) tuna. The results of this experiment help set the stage for the next lecture on the geochemistry, uses, and human impact of mercury. In this lecture, Brown emphasizes the local sources of mercury from extensive mining in the California Coast Range and its use in gold mining, as well as the cycling of mercury in ecosystems and differences in toxic properties of different mercury species. He also explains how the molecular-level speciation of mercury is determined in mercury mine wastes as well as in tuna using the extremely intense x-rays from the Stanford Synchrotron Radiation Laboratory.

For the second part of the day, we will switch from mercury to arsenic in the environment, another element that is very dangerous to humans. Andrea Foster (USGS) and Scott Fendorf (Stanford) will discuss the sources and geochemistry of arsenic in Bangladesh and California. They will present the target levels in drinking water in California as well as the natural sources and cycles of arsenic. Fendorf will present his compelling research on the

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cycling of arsenic in Bangladesh and the challenges of reducing the risk of arsenic poisoning there.

The final section of the workshop will focus on ground-breaking research on the molecular-level structure of bulk water as well as the process of science. Prof. Anders Nilsson (SLAC) will describe some of the unique properties of water that are not seen in other liquids and form the basis for our existence on earth. It is most surprising to many how little we know about the structure of liquid water and how water structure is connected to its properties. Nilsson will discuss his new results on water structure, which differ significantly from the traditional structure that is described in text books. He will also talk about his experience with challenging conventional wisdom in science and the endeavor to interact with his peers in the community when a new paradigm is proposed.

8. Geoscape Bay Area Workshop

Geoscape Bay Area was offered for the first time on July 7-10, 2009. This workshop was for sixth grade science teachers who teach Earth sciences as the primary curriculum in the California State Standards. Eighteen teachers participated in the 4-day workshop, interacting with scientists and students in the laboratory, the classroom, and the field. Teachers learned about the geology, water, energy, coastal ocean, and ecosystems by using the San Francisco Bay Area as an example of a local geoscape. A geoscape is a way to look at the geological landscape - water resources, natural hazards, earth resources, and ecosystems – and the connections between the natural and human systems. This workshop enhanced the skills, confidence, and knowledge of teachers who teach the sixth grade curriculum of Earth sciences.

Geochemistry was one of the many strands that ran through the workshop. On the first day, teachers learned about geological history of the Bay Area. On Day 2, teachers brought in samples of soil from their school or home to examine as part of the session focused on local geochemistry. This session was led by Geochemist Dr. Kate Maher of Stanford University. On Day 3, we discussed the natural and human-built fresh water system, and the sources of energy in California. On the final day, we discussed ecosystem services and agricultural needs, including nutrient cycling. This session was co-led by graduate student Jessica Lee (in Scott Fendorf’s research group). Also teachers created posters that represented the connections that they made between the systems and processes of the Earth that we discussed all week. Teachers shared activities that they have successfully used in the classrooms to teach the complex Earth system.

This workshop was funded in part by the Stanford EMSI. Participant costs, including stipends and meals, were funded by the EMSI. Stanford University School of Earth Sciences funded the development of the workshop curriculum.

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Geoscape Bay Area WorkshopJuly 7-10, 2009

TIME TUESDAY JULY 79:00 - 10:00 Welcome and Introductions10:00 - 12:15 Tectonic Setting of the San Francisco Bay Area12:15 - 1:00 Lunch1:00 – 3:30 Field Trip3:30 - 4:00 Geoscape Creation and Question Cards

TIME WEDNESDAY JULY 89:00– 12:00 Plate Tectonics in California

12:00 - 12:45 Lunch12:45 – 1:30 Quake-Catcher Network

1:30-2:00 Geoscape2:00-2:15 Break2:15-4:00 Geochemistry of the Bay Area

Question CardsTIME THURSDAY JULY 9

9:00 - 12:00 Water in the Bay Area 11:30-12:00 Geoscape12:00 - 12:45 Lunch1:00 – 3:30 Energy in the Bay Area 3:30-4:00 Geoscape Creation and Question Cards

TIME FRIDAY JULY 109:00– 11:00 Coastal Ecology of the Bay Area11:00-11:15 Break11:15-12:15 Ecosystem Services 12:15-1:00 Lunch1:00 – 3:45 Putting Together the Geoscape Bay Area3:45-4:00 Evaluation

9. Environmental Courses at Stanford University Relevant to the Stanford EMSI

Gordon Brown continues to teach a 4-unit senior-level undergraduate course in Environmental Geochemistry each year. In addition, the Stanford EMSI introduced a graduate-level seminar series that meets monthly for seminars and discussions of topics relevant to the Stanford EMSI. Scott Fendorf and Stanford colleague Prof. Christopher Francis offered a graduate level seminar series on Geomicrobiology & Microbial Geochemistry. Alfred Spormann offers a year-long graduate-level course on Environmental Microbiology each year as well as a summer course at Hopkins Marine Station in Monterey, CA on marine environmental microbiology.

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B. Stanford EMSI Education and Outreach Activities at the University of Alaska, Fairbanks

Our primary education efforts are directly linked with the EMSI-sponsored research of the Trainor group. The interface structure studies have been carried out by UAF graduate students Kunaljeet Tanwar and Raena Rowland and UAF postdoctoral research associates Sarah Petitto and Chris Iceman. These studies are done in close collaboration with a range of investigators from institutions located throughout the country, including Mike Toney (SSRL), Gordon Brown (Stanford U.), Anne Chaka (NIST), Peter Eng (U. of Chicago), and Glenn Waychunas (Lawrence Berkeley National Laboratory). The broad range of investigators and tools utilized in these studies have resulted in our students and postdoctoral associates having received training in diverse techniques such as synchrotron based x-ray scattering and spectroscopy, periodic density functional theory, and atomic force microscopy – often working with leading experts and within state-of-the-art facilities. We have also utilized our field studies to gain student interest and introduction to molecular environmental sciences. These projects have involved two UAF graduate students: Vanessa Ritchie and Anastasia Ilgen. Hence, the training of our students and post-doctoral associates in modern techniques and concepts of molecular environmental sciences has been a primary goal, and highly successful.

We have also used our work to expose undergraduate and high school students to the concepts and applications of molecular environmental sciences. During summer of 2008 the UAF group hosted Logan Daum, a former Fairbanks High School student and now MIT undergraduate for a summer internship. Logan is interested in computer programming and physics/physical chemistry. As such he spent the majority of his time developing a Monte-Carlo code for analyzing surface structures. Work on this project has continued in the summer 2009 with Jose Figueroa, a visiting undergraduate student from the University of Puerto Rico. The code is being developed using the MPI libraries for parallel execution and is work done in conjunction with our colleagues at the Arctic Region Supercomputing Center. This is a highly unique opportunity to provide early career college students access to supercomputing resources and an advanced code development project, as well as provide exposure to advanced chemical concepts and the molecular aspects of environmental science.

C. Stanford EMSI Education and Outreach Activities at Princeton University

At Princeton University, two undergraduate students Ms. Lauren Miller and Mr. Jeffrey King both Chemistry majors), and the researches of two visiting scientists Dr. Gustavo Martinez (Dept. of Agronomy and Soils, University of Puerto Rico) and Dr. Anne Kotchevar (Dept. of Chemistry, California State University, Hayward, CA) were supported by SEMSI in 2009. The salary of post-doctoral scholar Dr. Bhoopesh Mishra was shared between SEMSI and an exploratory grant from DOE (ERSP).

Dr. Martinez has been focusing his studies on the biogeochemistry of P in freshwater lakes, and how mineralogy and geochemistry of lakes (pH, dissolved oxygen/Eh), and the seasonal temperature fluctuations (e.g. overturning of lake waters) influence P-cycling in lacustrine environments. The studies conducted using X-ray spectroscopy indicate that the dominant forms of P in the particulate fraction and in sediments are inorganic and

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organophosphates, which gradually convert to apatite with ageing and depth. These results are in direct contrast to P-speciation and the retention mechanisms proposed very recently. We are continuing these studies and evaluating the seasonal influences on Fe and P speciation in freshwater lakes.

Dr. Kotchevar, and both undergraduates are conducting their independent work on the chemistry of organochlorines in the weathering environments. Using high-resolution mass-spectrometry, they have been conducting detailed speciation of organochlorines in weathering leaves (Mr. King), and lichens and fungi (Ms. Miller) found in the forest ecosystems, and the studies are currently in progress. We are also examining whether there is any seasonal variation in the speciation of organohalogens in the forest ecosystems.

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APPENDIX A: PUBLICATIONS BASED ON WORK SUPPORTED BY THE STANFORD EMSI (Sept. 2004 – Nov. 2009)

(Stanford EMSI Senior Investigators indicated in bold-face type)

A. Papers Published in Peer-Reviewed Journals, Proceedings Volumes, and Book Chapters(1) Andersson, K., A. Gómez, C. Glover, D. Nordlund, H. Öström, T. Schiros, O. Takahashi,

H. Ogasawara, L. G. M. Pettersson, and A. Nilsson, Molecularly intact and dissociative adsorption of water on clean Cu(110): A comparison with the water/Ru(001) system. Surf. Sci. Lett. 585(3), L183-L189 (2005).

(2) Andersson, K., G. Ketteler, H. Bluhm, S. Yamamoto, H. Ogasawara, L. G. M. Pettersson, M. Salmeron and A. Nilsson, Auto-catalytic water dissociation on Cu(110) at near ambient conditions. J. Am. Chem. Soc. 130, 2793-2797 (2008).

(3) Andersson, K., G. Ketteler, H. Bluhm, S. Yamamoto, H. Ogasawara, L. G. M. Pettersson, M. Salmeron and A. Nilsson, Bridging the pressure gap in water and hydroxyl chemistry on metal surfaces: Cu(110). J. Phys. Chem. C 111, 14493-14499 (2007).

(4) Andersson, K., A. Nikitin, L. G. M. Pettersson, A. Nilsson, and H. Ogasawara, Water dissociation on Ru(001): an activated process. Phys. Rev. Lett. 93, 196101 (2004).

(5) Andersson, K., M. Nyberg, H. Ogasawara, D. Nordlund, T. Kendelewicz, C. S. Doyle, G. E. Brown, Jr., L. G. M. Pettersson, and A. Nilsson, Experimental and theoretical characterization of the structure of defects at the pyrite FeS2 (100) surface. Phys. Rev. B 70(19), 195404/1 – 195404/5 (2004).

(6) Benner, S. G., M. L. Polizzotto, B. D. Kocar, S. Ganguly, K. Phan, K. Ouch, M. Sampson, and S. Fendorf, Groundwater flow in an arsenic-contaminated aquifer, Mekong Delta, Cambodia. Appl. Geochem. 23, 3072-3087 (2008).

(7) Benzerara, K., G. E. Brown, Jr., and T. Tyliszczak, Studies of the interactions between microbes and minerals by scanning transmission x-ray microscopy. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 726-730 (2007).

(8) Benzerara, K., A. Meibom, Q. Gautier, J. Kazmierczak, J. Stolarski, P. Lopez-Garcia, N. Menguy, and G.E. Brown, Jr., Nanotextures of aragonite in lacustrine stromatolites from the Satonda crater lake, Indonesia. In: Tufas, Speleothems, and Stromatolites, Geological Society of London (2009, in press).

(9) Benzerara, K., N. Menguy, N. R. Banerjee, G. E. Brown, Jr., and F. Guyot, Alteration of submarine basaltic glass from the Ontong Java Plateau: a STXM and TEM study. Earth Planet. Sci. Lett. 260, 187-200 (2007).

(10) Benzerara, K., N. Menguy, P. López-García, T. H. Yoon, J. Kazmierczak, T. Tyliszczak, F. Guyot, and G. E. Brown, Jr., Nanoscale detection of organic signatures in carbonate microbialites. Proc. Nat. Acad. Sci. U.S.A. 103, 9440-9445 (2006).

(11) Benzerara, K., V. M. Miller, G. Barell, V. Kumar, J. Miot, G. E. Brown, Jr., and J. C. Lieske, Search for microbial signatures within human and microbial calcifications using soft X-ray spectromicroscopy. J. Investigative Medicine 54(7), 367-379 (2006).

(12) Benzerara, K., G. Morin, T. H. Yoon, J. Miot, T. Tyliszczak, C. Casiot, F. Farges, and G. E. Brown, Jr., Nanoscale study of As transformations by bacteria in an acid mine drainage system. Geochim. Cosmochim. Acta 72(16), 3949-3963 (2008).

(13) Benzerara, K., T. H. Yoon, T. Tyliszczak, B. Constantz, A. M. Spormann, and G. E. Brown, Jr., Scanning transmission x-ray microscopy study of microbial calcification. Geobiology 2, 249-259 (2004).

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(14) Benzerara, K., T. H. Yoon, N. Menguy, T. Tyliszczak, and G. E. Brown, Jr., Nanoscale environments associated with bioweathering of a Mg-Fe-pyroxene. Proc. Nat. Acad. Sci. U.S.A. 102(19), 979-982 (2005).

(15) Bergmann, U., D. Nordlund, Ph. Wernet, M. Odelius, L. G. M. Pettersson and A. Nilsson,Isotope effects in liquid water probed by x-ray Raman spectroscopy. Phys. Rev. B 76, 024202 (2007).

(16) Bergmann, U., A. D. Cicco, Ph. Wernet, E. Principi, P. Glatzel and A. Nilsson, Nearest-neighbor oxygen distances in liquid water and ice observed by x-ray Raman based extended x-ray absorption fine structure. J. Chem. Phys. 127, 174504 (2007).

(17) Bernard, S., K. Benzerara, O. Beyssac, G. E. Brown, Jr., L. Grauvogel Stamm, and P. Duringer, Ultrastructural and chemical study of modern and fossil spores by Scanning Transmission X-ray Microscopy (STXM). Reviews of Paleobotany and Palynology 156, 248-261 (2009).

(18) Bernard, S., K. Benzerara, O. Beyssac, N. Menguy, F. Guyot, G. E. Brown, Jr., and B. Goffe, Exceptional preservation of fossil plants spores in high-pressure metamorphic rocks. Earth Planet. Sci. Lett. 262(1-2), 257-272 (2007).

(19) Berrodier, I., F. Farges, M. Benedetti, M. Winterer, G. E. Brown, Jr., and M. Deveughéle, Adsorption mechanisms of trivalent gold on iron- and aluminum-oxyhydroxides. Part I: X-ray absorption and Raman scattering spectroscopic studies of Au(III) adsorbed on ferrihydrite, goethite and boehmite. Geochim. Cosmochim. Acta 68, 3019-3042 (2004).

(20) Bickmore, B. R., K. M. Rosso, I. D. Brown, and S. N. Kerisit, Bond-valence constraints on liquid water structure. J. Phys. Chem. A 113, 1847-1857 (2009).

(21) Bickmore, B. R., K. M. Rosso, and S. C. Mitchell, Is there hope for multi-site complexation modeling? In: Surface Complexation Modeling (J. Lutzenkirchen, ed.), Elsevier, NY, pp. 269-283 (2006).

(22) Bluhm, H., K. Andersson, T. Araki, K. Benzerara, G. E. Brown, Jr., J. J. Dynes, S. Ghosal, M. K. Gilles, H.-Ch. Hansen, J. C. Hemminger, A. P. Hitchcock, G. Ketteler, E. Kneedler, J. R. Lawrence, G. G. Leppard, J. Majzlam, B. S. Mun, S. C. B. Myneni, A. Nilsson, H. Ogasawara, D. F. Ogletree, K. Pecher, M. Salmeron, D. K. Shuh, B. Tonner, T. Tyliszczak, and T. H. Yoon, Soft x-ray microscopy and spectroscopy using the Molecular Environmental Science beamline at the Advanced Light Source. J. Elec. Spectros. Rel. Phenom. 150(2-3), 86-104 (2006).

(23) Bluhm, H., M. Hävecker, A. Knop-Gericke, M. Kiskinova, R. Schlögl, M. Salmeron, In situ photoemission studies of gas/solid interfaces at near atmospheric pressures. Mat. Res. Soc. Bull. 32, 1022-1030 (2007).

(24) Bluhm, H. and H. C. Siegmann, Surface science with aerosols. Surf. Sci. 603, 1969 (2009).(25) Borch, T. and S. Fendorf, Phosphate interactions with iron (hydr)oxides: Mineralization

pathways and phosphorus retention upon bioreduction. In: Adsorption to Geomedia II (M. A. Barnett and D. B. Kent, eds.), Academic Press, NY, pp. 321-348 (2008).

(26) Bostick, B. C., C. Chen, and S. Fendorf, Arsenite retention mechanisms within estuarian sediments of Pescadero, CA. Environ. Sci. Technol. 38, 3299-3304 (2004).

(27) Bostick, B. C., S. Fendorf, and G. E. Brown, Jr., In situ analysis of thioarsenite complexes in neutral to alkaline arsenic sulfide solutions. Mineral. Mag. 69(5), 781-795 (2005).

(28) Brown, G. E., Jr., J. G. Catalano, A. S. Templeton, T. P. Trainor, F. Farges, B. C. Bostick, T. Kendelewicz, C. S. Doyle, A. M. Spormann, K. Revill, G. Morin, F. Juillot,

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and G. Calas, Environmental interfaces, heavy metals, microbes, and plants: Applications of XAFS spectroscopy and related synchrotron radiation methods to environmental science. Physica Scripta T115, 80-87 (2005).

(29) Brown, G. E., Jr., T. Kendelewicz, T. P. Trainor, K. S. Tanwar, A. M. Chaka, P. J. Eng, S. Yamamoto, A. Nilsson, H. Bluhm, D. E. Starr, M. Salmeron, J. G. Catalano, T. H. Yoon, K. Benzerara, G. Morin, G. Ona-Nguema, F. Juillot, B. Cances, and G. Calas, Recent advances in surface, interface, and environmental geochemistry. Water-Rock Interaction-12, Proceedings of the 12th International Water-Rock Interaction Conference, Kunming, China (Thomas Bullen and Yanxin Wang, eds.), Taylor & Francis, Publishers, London, Vol. 1, pp. 3-11 (2007).

(30) Brown, G. E., Jr., T. P. Trainor, and A. M. Chaka, Geochemistry of mineral surfaces and factors affecting their chemical reactivity. In: Chemical Bonding at Surfaces and Interfaces (A. Nilsson, L. G. M. Pettersson, and J. Norskov, eds.), Elsevier, New York, pp. 457-509 (2007).

(31) Cancès, B., M. Benedetti, F. Farges, and G. E. Brown, Jr., Adsorption mechanisms of trivalent gold onto iron oxy-hydroxides: From the molecular scale to the model. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 217-219 (2007).

(32) Cancès, B., F. Juillot, G. Morin, V. Laperche, L. Alvarez, O. Proux, J-L. Hazemann, G. E. Brown Jr., and G. Calas, XAS evidence of As(V) association with iron oxyhydroxides in a contaminated soil at a former arsenical insecticides processing plant. Environ. Sci. Technol. 39(24), 9398-9405 (2005).

(33) Cancès, B., F. Juillot, G. Morin, V. Laperche,, D. Polya, D.J. Vaughan, J-L. Hazemann, O. Proux, G. E. Brown Jr., and G. Calas, Change in arsenic speciation through a contaminated soil profile: an XAS based study. Sci. Total Environ. 397, 178-189 (2008).

(34) Catalano, J. G., T. P. Trainor, P. J. Eng, G. A. Waychunas, and G. E. Brown, Jr., CTR diffraction and grazing incidence XAFS study of U(VI) adsorption to a-Al2O3 and a-Fe2O3

(1-102) surfaces. Geochim. Cosmochim. Acta 69(14), 3555-3572 (2005).(35) Cavalleri, M., L-Å. Näslund, D. C. Edwards, P. Wernet, H. Ogasawara, S. Myneni, L.

Ojamae, M. Odelius, A. Nilsson, and L. G. M. Pettersson, The local structure of protonated water from x-ray absorption and density functional theory. J. Chem. Phys. 124(19), 194508/1-194508/8 (2006).

(36) Chalmin, E., F. Farges, and G. E. Brown, Jr., A pre-edge analysis of Mn K-edge XANES spectra to help determine the speciation of manganese in minerals and glasses. Contr. Mineral. Petrol. 157(1), 111-126 (2009).

(37) Chambers, S. A., T. C. Droubay, K. M. Rosso, S. M. Heald, S. A. Schwartz, K. R. Kittilstved, and D. R. Gamelin, Ferromagnetism in oxide semiconductors. Mat. Today 9(11), 28-35 (2006).

(38) Coskuner, O., Preferred conformation of the glycosidic linkage of methyl--mannose. J. Chem. Phys. 127, 015101-1 – 015101-7 (2007).

(39) Coskuner, O. and E. A. A. Jarvis, Coordination studies of Al-EDTA in aqueous solution. J. Phys. Chem. A 112, 2628-2633 (2008).

(40) Coskuner, O., E. A. A. Jarvis, and T. C. Allison, Water dissociation in the presence of metal ions. Angew. Chem. Int. Ed. 46, 7853-7855 (2007).

(41) Crot, C. A., C. Wu, M. L. Schlossman, T. P. Trainor, P. J. Eng, and L. Hanley, Determining the conformation of an adsorbed Br-PEG-Peptide by long-period x-ray standing wave fluorescence. Langmuir 21(17), 7899-7906 (2005).

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(42) Deng, X., T. Herranz, Ch. Weis, H. Bluhm, and M. Salmeron, Adsorption of water on CuO2 and Al2O3 thin films. J. Phys. Chem. C 112, 9668-9672 (2008).

(43) Deshmukh, A. P., C., Pacheco, M. B. Hay, and S. C. B. Myneni, Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part II: 2D NMR spectroscopy. Geochim. Cosmochim. Acta 71 3533-3544 (2007).

(44) Droubay, T. C., K. M. Rosso, S. M. Heald, D. E. McCready, C. M. Wang, and S. A. Chambers, Structure, magnetism, and conductivity in epitaxial Ti-doped a-Fe2O3 hematite. Phys. Rev. B 75, 104412/1-104412/7 (2007).

(45) Edwards, D. C. and S. C. B. Myneni, Near edge x-ray absorption fine structure spectroscopy of bacterial hydroxamate siderophores in aqueous solutions. J. Phys. Chem. A 110, 11809-11818 (2006).

(46) Fandeur, D., F. Juillot, G. Morin, L. Olivi, A. Cognigni, S. Webb, J-P. Ambrosi, E. Fritsch, F. Guyot, and G. E. Brown, Jr., XANES evidence for oxidation of Cr(III) to Cr(VI) by Mn-oxides in a lateritic regolith developed on serpentinized ultramafic rocks on New Caledonia. Environ. Sci. Technol. 43 (19), 7384-7390 (2009).

(47) Farges, F., K. Benzerara, and G. E. Brown, Jr., Chrysocolla redefined as spertiniite. 13th

Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 223-225 (2007).(48) Farges, F. and G. E. Brown, Jr., Coordination environments of highly charged cations

(Ti, Cr, and Light REE’s) in borosilicate glass/melts to 1120°C. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 208-210 (2007).

(49) Farges, F., M-P. Etcheverry, P. Trocellier, E. Curti, and G. E. Brown, Jr., Durability of silicate glasses: an historical approach. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 44-50 (2007).

(50) Farges, F., Y. Lefrère, S. Rossano, A. Berthereau, G. Calas, and G. E. Brown, Jr., The effect of redox state on the local structural environment of iron in silicate glasses: a combined XAFS spectroscopy, molecular dynamics, and bond valence study. J. Non-Crystal. Solids 344(3), 176-188 (2004).

(51) Farges, F., S. Djanarthany, S. de Wispelaere, M. Munoz, B. Magassouba, A. Haddi, M. Wilke, C. Schmidt, M. Borchert, P. Trocellier, W. Crichton, A. Simionovici, P.-E. Petit, M. Mezouar, M.-P. Etcheverry, I. Pallot-Frossard, J. R. Bargar, G. E. Brown, Jr., D. Grolimund, and A. Scheidegger, Water in silicate glasses and melts of environmental interest: from volcanoes to cathedrals. Physics and Chemistry of Glasses 46(4), 350-353 (2005).

(52) Farges, F., R. Siewert, G. E. Brown, Jr., A. Guesdon, and G. Morin, Structural environment around molybdenum in silicate glasses and melts: Part I. Influence of composition and oxygen fugacity on the local structure of molybdenum. Canadian Mineral. 44(3), 731-753 (2006).

(53) Farges, F., R. Siewert, C. W. Ponader, G. E. Brown, Jr., M. Pichavant, and H. Behrens, Structural environment around molybdenum in silicate glasses and melts: Part II. Effect of temperature, pressure, water, halogens, and sulfur. Canadian Mineral. 44(3), 755-773 (2006).

(54) Fendorf, S., M. J. Herbel, K. T. Tufano, and B. D. Kocar, Biogeochemical processes controlling the cycling of arsenic in soils and sediments. In: Biophysico-Chemical Processes of Heavy Metals and Metalloids in Soil Environments, IUPAC Division VI-Chemistry and the Environment (A. Violante, P. M. Huang, and G. Gadd, eds.), John Wiley & Sons, Chichester, England, pp. 313-338 (2007).

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(55) Fendorf, S., and B. D. Kocar, Biogeochemical processes controlling the fate and transport of arsenic: Implications for South and Southeast Asia. In. D.L. Sparks (Ed) Advances in Agronomy. ASA Publication, WI. (2009, in press).

(56) Gescher, J. S., C. D. Cordova, and A. M. Spormann, Dissimilatory iron reduction in Escherichia coli: Identification of CymA of Shewanella oneidensis and NapC of E. coli as ferric reductases. Mol. Microbiol. 68(3), 706-719 (2008).

(57) Ghose, S. K., S. C. Petitto, K. S. Tanwar, C. S. Lo, P. J. Eng, A. M. Chaka, T. P. Trainor, Surface structure and reactivity of iron oxide-water interfaces. In: Adsorption of Metals to Geomedia II (M. O. Barnett and D. B. Kent, eds.), American Chemical Society, Washington D.C., pp. 1-24 (2008).

(58) Ginder-Vogel, M. A. and S. Fendorf, Biogeochemical uranium redox transformations: Potential oxidants of uraninite. In: Adsorption to Geomedia II (M. A. Barnett and D. B. Kent, eds.), Academic Press, NY, pp. 293-321 (2008).

(59) Ha, J., F. Farges, and G. E. Brown, Jr., Adsorption and precipitation of aqueous Zn(II) on hematite nano- and microparticles. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 238-240 (2007).

(60) Ha, J., A. Gélabert, A. M. Spormann, and G. E. Brown, Jr., Role of extracellular polymeric substances in metal complexation on Shewanella oneidensis: Batch uptake, thermodynamic modeling, ATR-FTIR, and EXAFS study. Geochim. Cosmochim. Acta (2009, in press).

(61) Ha, J., T. P. Trainor, F. Farges, and G. E. Brown, Jr., Interaction of Zn(II) with hematite nanoparticles and microparticles: Part 1. EXAFS spectroscopy study of Zn(II) adsorption and precipitation. Langmuir 25(10), 5574-5585 (2009).

(62) Ha, J., T. P. Trainor, F. Farges, and G. E. Brown, Jr., Interaction of Zn(II) with hematite nanoparticles and microparticles: Part 2. ATR-FTIR and EXAFS spectroscopy study of the Zn(II)-oxalate-hematite ternary system. Langmuir 25(10), 5586-5593 (2009).

(63) Ha, J., T. H. Yoon, Y. Wang, C.B. Musgrave, and G.E. Brown, Jr., ATR-FTIR and quantum chemical study of the interaction of lactate with hematite nanoparticles. Langmuir 6683-6692 (2008).

(64) Haddi, A., M. Harfouche, F. Farges, P. Trocellier, E. Curti, and G. E. Brown, Jr., On the coordination of actinides and fission products in silicate glasses. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 256-258 (2007).

(65) Hansel, C. M., S. Fendorf, P. M. Jardine, C. A. Francis, Changes in bacterial and archaeal community structure and functional diversity along a geochemically variable soil profile. Appl. Environ. Microbiol. 74(5), 1620-1633 (2008).

(66) Hay, M. B. and S. C. B. Myneni, Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1: Infrared spectroscopy. Geochim. Cosmochim. Acta 71, 3518-3532 (2007).

(67) Hay, M. B. and S. C. B. Myneni, Geometric and electronic structure of the aqueous Al(H2O)6

3+ complex. J. Phys. Chem. A 112, 10595-10603 (2008).(68) Herbel, M. J. and S. Fendorf, Transformation and transport of arsenic within ferric

hydroxide coated sands upon dissimilatory reducing bacterial activity. In: Advances in Arsenic Research: Integration of Experimental and Observational Studies and Implications for Mitigation. ACS Symp. Series 915 (Advances in Arsenic Research), (P.A. O’Day, D. Vlassopoulos, X. Meng, and L.G. Benning, eds.), pp. 77-90 (2005).

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(69) Herbel, M. J. and S. Fendorf, Biogeochemical processes controlling the speciation and transport of arsenic within iron coated sands. Chem. Geol. 228(1-3), 16-32 (2006).

(70) Huang, C., K. T. Wikfeldt, T. Tokushima, D. Nordland, Y. Harada, U. Bergmann, M. Niebuhr, T. M. Weiss, Y. Horikawa, M. Leetmaa, M. P., Ljungberg, O. Takahashi, A. Lenz, L. Ojamäe, A. P. Lyubartsev, S. Shin, L. G. M. Pettersson, and A. Nilsson, The inhomogeneous structure of water at ambient conditions. Proc. Nat. Acad. Sci. U.S.A. 2009, 106 (Early Edition).

(71) Iordanova, N., M. Dupuis, and K. M. Rosso, Charge transport in metal oxides: A theoretical study of hematite a-Fe2O3. J. Chem. Phys. 122(14), 144305/1-144305/10 (2005).

(72) Jackson, W. E., F. Farges, M. Yeager, P. A. Mabrouk, S. Rossano, G. A. Waychunas, E. I. Solomon, and G. E. Brown, Jr., Multi-spectroscopic study of Fe(II) in silicate glasses: Implications for the coordination environment of Fe(II) in silicate melts. Geochim. Cosmochim Acta 69, 4315-4332 (2005).

(73) Johnson, S. B., G. E. Brown, Jr., T. W. Healy, and P. J. Scales, Adsorption of organic matter at mineral/water interfaces: 6. Effect of inner-sphere vs. outer-sphere adsorption on colloidal stability. Langmuir 21(14), 6356-6365 (2005).

(74) Johnson, S. B., T. H Yoon, B. Kocar, and G. E. Brown, Jr., Adsorption of organic matter at mineral/water interfaces: 2. Outer-sphere adsorption of maleate on aluminum oxide and implications for dissolution processes. Langmuir 20(12), 4996-5006 (2004).

(75) Johnson, S. B., T. H. Yoon, A. J. Slowey, and G. E. Brown, Jr., Adsorption of organic matter at mineral/water interfaces: 3. Implications of surface dissolution for adsorption of oxalate. Langmuir 20(26), 11480-11492 (2004).

(76) Johnson, S. B., T. H. Yoon, and G. E. Brown, Jr., Adsorption of organic matter at mineral/water interfaces: 5. Effects of adsorbed natural organic matter analogs on mineral dissolution. Langmuir 21(7), 2811-2821 (2005).

(77) Juillot, F., C. Maréchal, G. Morin, D. Jouvin, S. Cacaly, P. Telouk, M. F. Benedetti, P. Ildefonse, S. Sutton, F. Guyot, and G. E. Brown, Jr., Evidence for contrasted isotopic signatures between anthropogenic and natural Zn in smelter-impacted soils from Northern France. Geochim. Cosmochim. Acta 73 (2009, in press).

(78) Juillot, F., G. Morin, J-L. Hazemann, O. Proux, S. Belin, V. Briois, G. E. Brown, Jr., and G. Calas, EXAFS signatures of structural Zn at trace levels in layered minerals. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 247-249 (2007).

(79) Juillot, F., G. Morin, P. Ildefonse, G. Calas, and G. E. Brown, Jr., EXAFS signature of structural Zn at trace levels in natural and synthetic tri- and dioctahedral 2:1 phyllosilicates. Am. Mineral. 91 (8-9), 1432-1441 (2006).

(80) Jun, Y-S., S. K. Ghose, T. P. Trainor, P. J. Eng, and S. T. Martin, Structure of the hydrated (10-14) surface of rhodochrosite (MnCO3). Environ, Sci, Technol. 41, 3918-3925 (2007).

(81) Kelsey, K. E., J. F. Stebbins, D. M. Singer, G. E. Brown, Jr., J. L. Mosenfelder, and P. D. Asimow, Cation field strength effects on high pressure aluminosilicate glass structure: Multinuclear NMR and La XAFS results. Geochim. Cosmochim. Acta 73, 3914-3933 (2009).

(82) Kendelewicz, T., C. S. Doyle, B. C. Bostick, and G. E. Brown, Jr., Initial oxidation of fractured surfaces of FeS2 (100) by molecular oxygen, water vapor, and air. Surf. Sci. 558(1-3), 80-88 (2004).

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(83) Kerisit, S. and K. M. Rosso, Computer simulation of electron transfer at hematite surfaces. Geochim. Cosmochim. Acta 70, 1888-1903 (2006).

(84) Ketteler, G., P. Ashby, B. S. Mun, I. Ratera, H. Bluhm, B. Kasemo, M. Salmeron, In situ photoelectron spectroscopy of water adsorption on model biomaterial surfaces. J. Phys. Condens. Matt. 20(18), 184024/1-184024/7 (2008).

(85) Ketteler, G., S. Yamamoto, H. Bluhm, K. Andersson, D. E. Starr, D. F. Ogletree, H. Ogasawara, A. Nilsson and M. Salmeron, The nature of the water nucleation sites on TiO2(110) surfaces revealed by ambient pressure x-ray photoelectron spectroscopy. J. Phys. Chem. C. 111, 8278-8282 (2007).

(86) Kocar, B. D., T. Borch, and S. Fendorf, Arsenic repartitioning during biogenic sulfidization and transformation of ferrihydrite. Geochim. Cosmochim. Acta (2009, in press).

(87) Kocar, B. D., and S. Fendorf, Thermodynamic constraints on reductive reactions influencing the biogeochemistry of arsenic in soils and sediments. Environ. Sci. Technol. 43, 4871-4877 (2009).

(88) Kocar, B. D., M. J. Herbel, K. J. Tufano, and S. Fendorf, Contrasting effects of dissimilatory iron(III) and arsenic(V) reduction on arsenic retention and transport. Environ. Sci. Technol. 40, 6715-6721 (2006).

(89) Kocar, B. D., M. L. Polizzotto, S. G. Benner, S. Ying, M. Ung, K. Ouch, S. Samreth, B. Suy, K. Phan, M. Sampson, and S. Fendorf, Integrated biogeochemical and hydrologic processes driving arsenic release from shallow sediments to groundwaters of the Mekong Delta. Appl. Geochem. 23(11), 3059-3071 (2008).

(90) Komlos, J., B. Mishra, A. Lanzirotti, S. C. B. Myneni, and P. R. Jaffe, Real-time speciation of uranium during active bioremediation and U(IV) reoxidation. J. Environ. Eng. 134, 78-86 (2008).

(91) Leetmaa, M., K. T. Wikfeldt, M. P. Ljungberg, M. Odelius, J. Swenson, A. Nilsson, and L. G. M. Pettersson, Diffraction and IR/Raman data do not prove tetrahedral water. J. Chem. Phys. 129, 084502-1 - 084502-13 (2008).

(92) Lepot, K., K. Benzerara, G.E. Brown, Jr., and P. Philipot, Nanoscale evidence for microbial mineralization of Archaean stromatolites. Nature Geosciences 1, 118-121 (2008).

(93) Lepot, K., K. Benzerara, G.E. Brown, Jr., and P. Philippot, Organic matter heterogeneities in 2.72 Ga stromatolites: Alteration versus preservation by sulfur incorporation. Geochim. Cosmochim. Acta (2009, in press).

(94) Leri, A. C., M. B. Hay, A. Lanzirotti, W. Rao, and S. C. B. Myneni, Quantitative determination of absolute organohalogen concentrations in environmental samples by x-ray absorption spectroscopy. Anal. Chem. 78, 5711-5718 (2006).

(95) Leri, A. C., M. A. Marcus, and S. C. B. Myneni, X-ray spectroscopic investigation of natural organochlorine distribution in weathering plant material. Geochim. Cosmochim. Acta 71, 5834-5846 (2007).

(96) Lo, C. S., K. S. Tanwar, A. M. Chaka, and T. P. Trainor, Density functional theory study of the clean and hydrated hematite (1-102) surface. Phys. Rev. B 75, 075425-1 – 075425-15 (2007).

(97) Majzlan, J. and S. C. B. Myneni, Speciation of sulfate in acid waters and its influence on mineral precipitation. Environ. Sci. Technol. 39, 188-194 (2005).

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(98) Mason, S. E., C. R. Iceman, K. S. Tanwar, T. P. Trainor, and A. M. Chaka, Pb(II) adsorption on isostructural hydrated alumina and hematite (0001) surfaces: A DFT study. J. Phys. Chem. C 113, 2159-2170 (2009).

(99) Miot, J., K. Benzerara, G. Morin, A. Kappler, S. Bernard, M. Obst, C. Férard, F. Skouri-Panet, J-M. Guigner, N. Posth, M. Galvez, and G. E. Brown, Jr., Iron biomineralization by anaerobic neutrophillic iron-oxidizing bacteria. Geochim. Cosmochim. Acta 73(3), 696-711 (2009).

(100)Miot, J., G. Morin, F. Skouri-Panet, C. Ferard, E. Aubry, J. Briand, Y. Wang, G. Ona-Nguema, F. Guyot, and G. E. Brown, Jr., EXAFS study of arsenic speciation in Euglena gracilis exposed to arsenite. Environ. Sci. Technol. 42, 5342-5347 (2008).

(101)Miot, J., G. Morin, F. Skouri-Panet, C. Ferard, A. Poitevin, E. Aubry, G. Ona-Nguema, F. Juillot, F. Guyot, and G. E. Brown, Jr., Speciation of arsenic in Euglena gracillis cells exposed to As(V). Environ. Sci. Technol. 43(9), 3315-3321 (2009).

(102)Morin, G., G. Ona-Nguema, Y. Wang, N. Menguy, F. Juillot, O. Proux, F. Guyot, G. Calas, and G. E. Brown, Jr., EXAFS analysis of arsenite and arsenate adsorption on maghemite. Environ. Sci. Technol. 42, 2361-2366 (2008).

(103)Morin, G., Y. Wang, G. Ona-Nguema, F. Juillot, G. Calas, E. Aubry, J.R. Bargar, and G. E. Brown, Jr., EXAFS and HRTEM evidence for surface precipitation of arsenic(III) on nanocrystalline magnetite: Implications for As sequestration. Langmuir 25 (16), 9119-9128 (2009).

(104)Mrazek, J, Spormann, A. M., Karlin S., Genomic comparison between Shewanella and Vibrio, and with other g-proteobacteria. Environ. Microbiol. 8(2), 273-288 (2006).

(105) Näslund, L-Å., D. C. Edwards, Ph. Wernet, U. Bergmann, H. Ogasawara, L. G. M. Pettersson, S. Myneni, and A. Nilsson, X-ray absorption spectroscopy study of the hydrogen bond network in the bulk water of aqueous solutions. J. Phys. Chem. A 109(27), 5995-6002 (2005).

(106)Näslund, L-Å., J. Lüning, Y. Ufuktepe, H. Ogasawara, Ph. Wernet, U. Bergmann, L. G. M. Pettersson, and A. Nilsson, X-ray absorption spectroscopy measurements of liquid water. J. Phys. Chem. B 109(28), 13835-13839 (2005).

(107)Neiss, J., B. Stewart, P. Nico, and S. Fendorf, Geochemical constrains on microbially mediated uranyl reduction under hydrodynamic conditions. Environ. Sci. Technol. 41, 7343-7348 (2007).

(108) Nilsson, A., H. Ogasawara, M. Cavelleri, D. Nordlund, M. Nyberg, Ph. Wernet and L. G. M. Pettersson, The hydrogen bond in ice probed by soft x-ray spectroscopy and density functional theory. J. Chem. Phys. 122, 154595/1-8 (2005).

(109)Nilsson, A. and L. G. M. Pettersson, Chemical bonding on surfaces probed by x-ray emission spectroscopy and density functional theory. Surf. Sci. Repts. 55, 49-167 (2004).

(110)Nilsson, A. and L. G. M. Pettersson, Adsorbate electronic structure and bonding on metal surfaces. In: Chemical Bonding at Surfaces and Interfaces (A. Nilsson, L. G. M. Pettersson, and J. Norskov, eds.), Elsevier, New York, pp. 57-142 (2007).

(111)Nilsson, A., Ph. Wernet, D. Nordlund, U. Bergmann, H. Ogasawara, M. Cavalleri, L-Å. Näslund, T. K. Hirsch, L. Ojamäe, P. Glatzel, M. Odelius and L. G. M. Pettersson, Comment on energetics of hydrogen bond network rearrangements in liquid water. Science 308, 793a (2005).

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(112)Nordlund, D., M. Odelius, H. Bluhm, H. Ogasawara, L. G. M. Pettersson, A. Nilsson, Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory. Chem. Phys. Lett. 460, 86-92 (2008).

(113)Nordlund, D., H. Ogasawara, H. Bluhm, O. Takahashi, M. Odelius, M. Nagasono, L.G.M. Pettersson and A. Nilsson, Probing the electron delocalization in liquid water and ice at attosecond timescales, Phys. Rev. Lett. 99, 217406 (2007).

(114)Ogletree, D. F., H. Bluhm, E. L. D. Hebenstreit, and M. Salmeron, Photoelectron spectroscopy under ambient pressure and temperature conditions. Nucl. Instrum. Methods A 601, 151 (2009).

(115)Ona-Nguema, G., G. Morin, F. Juillot, G. Calas, and G. E. Brown, Jr., Arsenite sorption onto 2-line ferrihydrite, hematite, goethite, and lepidocrocite under anoxic conditions: a XANES and EXAFS study. Environ. Sci. Technol. 39(23), 9147-9155 (2005).

(116)Ona-Nguema, G., G. Morin, Y. Wang, N. Menguy, F. Juillot, L. Olivi, G. Aquilanti, M. Abdelmoula, C. Ruby, F. Guyot, G. Calas, and G. E. Brown, Jr., Arsenic sequestration at the surface of nano-Fe(OH)2, ferrous-carbonate hydroxide, and green-rust after bioreduction of arsenic-sorbed lepidocrocite by Shewanella putrefaciens. Geochim. Cosmochim. Acta 73(5), 1359-1381 (2009).

(117)Polizzotto, M. L., S. G. Benner, B. D. Kocar, M. Sampson, and S. Fendorf, Near-surface wetland sediments as a source of arsenic release to groundwater in Asia. Nature 454, 505-508 (2008).

(118)Polizzotto, M. L., C. F. Harvey, G-C. Li, B. Badruzzman, M. Newville, and S. Fendorf, Solid-phases and desorption processes of arsenic within Bangladesh sediments. Chem. Geol. 228, 97-111 (2006).

(119)Polizzotto, M. L., C. F. Harvey, S. R. Sutton, and S. Fendorf, Processes conducive to the release and transport of arsenic into aquifers of Bangladesh. Proc. Nat. Acad. Sci. USA 102, 18819-18823 (2005).

(120)Poussart, P. M., S. C. B. Myneni, and Lanzirotti, A., Tropical dendrochemistry: A novel approach to estimate age and growth from ringless trees. Geophys. Res. Lett. 33(17) L1771/1-L17711/5 (2006).

(121)Rogers, J. H., J. R. Bargar, G. A. Waychunas, T. H. Yoon, and G. E. Brown, Jr., A novel spectrometer system for hard x-ray interfacial environmental chemistry. Synchrotron Radiation Instrumentation 2003, AIP Conference Proceedings 705, 981-984 (2004).

(122)Rosso, K. M. and D. J. Vaughan, Sulfide mineral surfaces. Reviews in Mineralogy and Geochemistry 61, 505-556 (2006).

(123)Rosso, K. M. and D. J. Vaughan, Reactivity of sulfide mineral surfaces. Reviews in Mineralogy and Geochemistry 61, 557-607 (2006).

(124)Sahai, N. and K. M. Rosso, Computational molecular basis for improved silica surface complexation models. In: Surface Complexation Modeling (J. Lutzenkirchen, ed.), Elsevier, NY, pp. 359-396 (2007).

(125)Salmeron, M., H. Bluhm, M. Tatarkhanov, G. Ketteler, T. Shimizu, A. Mugarza, X. Deng, T. Herranz, S. Yamamoto, A. Nilsson, Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups. Faraday Disc. 141, 221 (2009).

(126)Schiros, T., S. Haq, H. Ogasawara, O. Takahashi, H. Öström, K. Andersson, L. G. M. Pettersson, A. Hodgson, and A. Nilsson, Structure of water adsorbed on the Cu(110) Surface: H-up, H-down, or both? Chem. Phys. Lett. 429, 415-419 (2006).

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(127)Schiros, T., L-Å. Näslund, K. Andersson, J. Gyllenpalm, G. S. Karlberg, M. Odelius, H. Ogasawara, L. G. M. Pettersson and A. Nilsson, Structure and bonding of water-hydroxyl mixed phase on Pt(111). J. Phys. Chem. C 111, 15003-15012 (2007).

(128)Singer, D. M., F. Farges, and G. E. Brown, Jr., Biogenic UO2 – characterization and surface reactivity. 13th Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 277-279 (2007).

(129)Singer, D. M., S. B. Johnson, J. G. Catalano, F. Farges, and G. E. Brown, Jr., Sequestration of Sr(II) by calcium oxalate – A batch uptake study and EXAFS analysis of model compounds and reaction products. Geochim. Cosmochim. Acta 72, 5055-5069 (2008).

(130)Singer, D. M., K. Maher, and G.E. Brown, Jr., Uranyl-chlorite sorption/desorption: Evaluation of different sequestration processes. Geochim. Cosmochim. Acta 73, 5989-6007 (2009).

(131)Singer, D. M., J. M. Zachara, and G. E. Brown, Jr., Uranium speciation as a function of depth in contaminated Hanford Sediments – A micro-XRF, micro-XAFS, and micro-XRD study. Environ. Sci. Technol. 43(3), 630-636 (2009).

(132)Slowey, A. J. and G. E. Brown, Jr., Transformations of mercury, iron, and sulfur during the reductive dissolution of iron oxyhydroxide by sulfide. Geochim. Cosmochim. Acta 71(4), 877-894 (2007).

(133)Slowey, A. J., S. B. Johnson, M. Newville, and G. E. Brown, Jr., Speciation and colloid transport of arsenic from mine tailings. Appl. Geochem. 22, 1884-1898 (2007).

(134)Slowey, A. J., S. B. Johnson, J. J. Rytuba, and G. E. Brown, Jr., Role of organic acids in promoting transport of mercury from mine tailings. Environ. Sci. Technol. 39(20), 7869-7874 (2005).

(135)Starr, D. E., C. Weis, S. Yamamoto, A. Nilsson, and H. Bluhm, NO2 adsorption on Ag(100) supported MgO(100) thin films: controlling the adsorption state with film thickness. J. Phys. Chem. C 113, 7355-7363 (2009).

(136)Stewart, B. D., P. S. Nico, and S. Fendorf, Stability of uranium incorporated into Fe (hydr)oxides under fluctuating redox conditions. Environ. Sci. Technol. 43, 4922-4927 (2009).

(137)Strathmann, T. J. and S. C. B. Myneni, Speciation of aqueous Ni(II)-carboxylate and Ni(II)-fulvic acid solutions: Combined ATR-FTIR and XAFS analysis. Geochim. Cosmochim. Acta 68, 3441-3458 (2004).

(138)Strathmann, T. J. and S. C. B. Myneni, Effect of soil fulvic acid on Ni(II) sorption and bonding at the aqueous-boehmite (g-AlOOH) interface. Environ. Sci. Technol. 39(11), 4027-4034 (2005).

(139)Tanwar, K. S., J. G. Catalano, S. C. Petitto, S. K. Ghose, P. J. Eng, and T. P. Trainor, Hydrated a-Fe2O3 (1-102) surface structure: Role of surface preparation. Surf. Sci. Lett. 601, L59-L64 (2007).

(140)Tanwar, K. S., C. S. Lo, P. J. Eng, J. G. Catalano, D. Walko, G. E. Brown, Jr., G. A. Waychunas, A. M. Chaka, and T. P. Trainor, Surface diffraction study of the hydrated hematite (1-102) surface. Surf. Sci. 601, 460-474 (2007).

(141)Tanwar, K. S., S. C. Petitto, S. K. Ghose, P. J. Eng, T. P. Trainor, Structural study of Fe(II) adsorption on hematite (1-102). Geochim. Cosmochim. Acta 72(14), 3311-3325 (2008).

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(142)Tanwar, K. S., S. C. Petitto, S. K. Ghose, P. J. Eng, and T. P. Trainor, Fe(II) adsorption on hematite (0001). Geochim. Cosmochim, Acta 73, 4346-4365 (2009).

(143)Thormann, K. M., S. Duttler, R. M. Saville, M. Hyodo, S. Shukla, Y. Hayakawa, and A. M. Spormann, Control of formation and cellular detachment from Shewanella oneidensis MR-1 biofilms by cyclic di-GMP. J. Bacteriology 188(7), 2681-2691 (2006).

(144)Thormann, K. M., R. M. Saville, S. Shukla, and A. M. Spormann, Induction of rapid detachment in Shewanella oneidensis MR-1 biofilms. J. Bacteriology 187(3), 1014-1021 (2005).

(145)Thormann, K. M., R. M. Saville, S. Shukla, D. A. Pelletier, and A. M. Spormann, Initial phases of biofilm formation in Shewanella oneidensis MR-1. J. Bacteriology 186(23), 8096-8104 (2004).

(146)Toevs, G. R., M. J. Morra, M. L. Polizzotto, D. G. Strawn, B. C. Bostick, and S. Fendorf, Metal(loid) diagenesis in mining-impacted sediments of Lake Coeur’d Alene, Idaho. Environ. Sci. Technol. 40, 2537-2543 (2006).

(147)Toevs G., M. J. Morra, L. Winowiecki, D. Strawn, M. L. Polizzotto, and S. Fendorf, Depositional influences on porewater arsenic in sediments of a mining-contaminated freshwater lake. Environ. Sci. Technol. 42(18), 6823-6829 (2008).

(148)Tokushima, T., Y. Harada, O. Takahashi, Y. Senba, H. Ohashi, L. G. M. Pettersson, A. Nilsson and S. Shin, High resolution x-ray emission spectroscopy of liquid water: The observation of two structural motifs. Chem. Phys. Lett. 460 (4-6), 387-400 (2008).

(149)Trainor, T. P., A. M. Chaka, P. J. Eng, M. Newville, G. A. Waychunas, J. G. Catalano, and G. E. Brown, Jr., Structure and reactivity of the hydrated hematite (0001) surface. Surf. Sci. 573(2), 204-224 (2004).

(150)Trainor, T, P., A. S. Templeton, and P. J. Eng, Structure and reactivity of environmental interfaces: Application of grazing angle x-ray spectroscopy and long-period x-ray standing waves. J. Elec. Spectros. Rel. Phenom. 150(2-3), 66-85 (2006).

(151)Tufano, K. T., S. G. Benner, K. U. Mayer, M. A. Marcus, P. S. Nico, and S. Fendorf, Aggregate-scale heterogeneity in iron (hydr)oxide reductive transformation. Vadose Zone J. (2009, in press).

(152)Tufano, K. T. and S. Fendorf, Confounding impacts of iron reduction on arsenic retention. Environ. Sci. Technol. 42, 4777-4783 (2008).

(153)Tufano, K. T., C. Reyes, C. W. Saltikov, and S. Fendorf, Reductive processes controlling arsenic retention: Revealing the relative importance of iron and arsenic reduction. Environ. Sci. Technol. 42, 8283-8289 (2008).

(154)Tyliszczak, T., T. Warwick, A. L. D. Kilcoyne, S. Fakra, D. K. Shuh, T. H. Yoon, G. E. Brown, Jr., S. Andrews, V. Chembrolu, J. Strachan, and Y. Acremann, Soft x-ray scanning transmission microscope working in an extended energy range at the Advanced Light Source. Synchrotron Radiation Instrumentation 2003, AIP Conference Proceedings 705, 1356-1359 (2004).

(155)van Hullenbusch, E., F. Farges, M. Lenz, P. Lens, and G. E. Brown, Jr., Selenium speciation in biofilms from granular sludge bed reactors used for wastewater treatment. 13th

Int. XAFS Conf. 2006, Am. Inst. Phys. Conf. Proc. 882, 229-231 (2007).(156)Vaughan, D. J. and K. M. Rosso, Bonding in sulfide minerals. Reviews in Mineralogy and

Geochemistry 61, 231-264 (2006).

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(157)Verdaguer, A., J. J. Segura, J. Fraxedas, H. Bluhm, and M. Salmeron, Discharge of insulating surfaces by water adsorption: a near-ambient pressure X-ray photoelectron spectroscopy study. J. Phys. Chem. C 112, 16898-16901 (2008).

(158)Verdaguer, A., Ch. D. Weis, G. Oncins, G. Ketteler, H. Bluhm, M. Salmeron, Growth and structure of water on SiO2 films on Si investigated by Kelvin probe microscopy and in situ X-ray spectroscopies. Langmuir 23, 9699 (2007).

(159)Waluyo, I., D. Nordlund, L-Å Näslund, H. Ogasawara, L. G. M. Pettersson and A. Nilsson, Spectroscopic evidence for the formation of 3-D crystallites during isothermal heating of amorphous ice on Pt(111). Surf. Sci. 602, 2004-2008 (2008).

(160)Waluyo, I., D. Nordlund, L-Å Näslund, H. Ogasawara, L. G. M. Pettersson and A. Nilsson, Increased fraction of weakened hydrogen bonds of water in aerosol OT micelles. J. Chem. Phys. 131, 031103 (2009).

(161)Wander, M. C. F., S. Kerisit, K. M. Rosso, and M. A. A. Schoonen, Kinetics of triscarbonato uranyl reduction by aqueous ferrous iron: A theoretical study. J. Phys. Chem. A 110, 9691-9701 (2006).

(162)Wander, M. C. F., K. M. Rosso, and M. A. A. Schoonen, Structure and charge hopping dynamics in green rust. J. Phys. Chem. C 111(30), 11414-11423 (2007).

(22) Wang, Y., G. Morin, G. Ona-Nguema, F. Juillot, F. Guyot, G. Calas, and G. E. Brown, Jr., Extended x-ray absorption fine structure analysis of arsenite and arsenate adsorption on green rust. Environ. Sci. Technol. (2009, in press).

(163)Wang, Y., G. Morin, G. Ona-Nguema, N. Menguy, F. Juillot, E. Aubry, F. Guyot, G. Calas, and G. E. Brown, Jr., Arsenite adsorption at the magnetite-water interface during aqueous precipitation of magnetite: EXAFS evidence for a new arsenite surface complex. Geochim. Cosmochim. Acta 72, 2573-2586 (2008).

(164)Waychunas, G. A., Y. S. Jun, P. J. Eng, S. K. Ghose, and T. P. Trainor, Anion sorption topology on hematite: Comparison of arsenate and silicate. In: Adsorption of Metals to Geomedia II (Mark O. Barnett and Douglas B. Kent, eds.), Elsevier, New York, pp. 31-62 (2008).

(165)Waychunas, G. A., T. P. Trainor, P. Eng, J. G. Catalano, G. E. Brown, Jr., J. A., Davis, J. Rogers, and J. R. Bargar, Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: arsenate on hematite (0001) and (10-12). Analytical and Bioanalytical Chemistry 383(1), 12-27 (2005).

(166)Wei, J., A. Saxena, B. Song, B. B. Ward, T. J. Beveridge, and S. C. B. Myneni, Elucidation of functional groups on Gram-positive and Gram-negative bacterial surfaces using infrared spectroscopy. Langmuir 20, 11433-11442 (2004).

(167)Wernet, Ph., D. Nordlund, U. Bergmann, M. Cavalleri, M. Odelius, H. Ogasawara, L-Å. Näslund, T. K. Hirsch, L. Ojamaee, P. Glatzel, L. G. M. Pettersson, and A. Nilsson, The structure of the first coordination shell in liquid water. Science 304 (5673), 995-999 (2004).

(168)Wernet, Ph., D. Testemale, J-L. Hazemann, R. Argoud, P. Glatzel, L. G. M. Pettersson, A. Nilsson, U. Bergmann, Spectroscopic characterization of microscopic hydrogen-bonding disparities in supercritical water. J. Chem. Phys. 123(15), 154503/1-154503/7 (2005).

(169)Wigginton, N. S., K. M. Rosso, A. S. Stack, and M. F. Hochella, Jr., Influence of bacterial multiheme cytochromes on long-range electron tunneling to hematite (001) surfaces. J. Phys. Chem. C 113, 2096-2103 (2009).

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(170)Wigginton, N. S., K. M. Rosso, M. F. Hochella, Jr., Long-range electron transfer across cytochrome-hematite (a-Fe2O3) interfaces. J. Phys. Chem. B 111, 12857-12864 (2007).

(171)Wikfeldt, K. T., M. Leetmaa, M. P. Ljungberg, A. Nilsson, and L. G. M. Pettersson, On the range of water structure models compatible with x-ray and neutron diffraction data. J. Phys. Chem. B 113, 6246-6255 (2009).

(172)Yamamoto, S., K. Andersson, H. Bluhm, G. Ketteler, D. E. Starr, T. Schiros, H. Ogasawara, L. G. M. Pettersson, M. Salmeron, and A. Nilsson, Hyroxyl-induced wetting of metals by water at near-ambient conditions. J. Phys. Chem. C 111(22), 7848-7850 (2007).

(173)Yamamoto, S., H. Bluhm, K. Andersson, G. Ketteler, H. Ogasawara, M. Salmeron, A. Nilsson, In situ X-ray photoelectron spectroscopy of water on metals and oxides under ambient conditions. J. Phys. Condens. Matt. 20, 184025 (2008).

(23) Yamamoto, S., T. Kendelewicz, J.T. Newberg, G. Ketteler, D.E. Starr, E.R. Mysak, K. Andersson, H. Ogasawara, H. Bluhm, M. Salmeron, G. E. Brown, Jr., and A. Nilsson, Water adsorption on a-Fe2O3(0001) at near ambient conditions. J. Phys. Chem. C (2009, in press).

(174)Yoon, J., J. Ha, J. Hwang, B-H. Hwang, and G. E. Brown, Jr., Study of iodide adsorption on organbentonite using x-ray absorption spectroscopy. J. Mineral. Soc. Korea 22(1), 23-34 (2009).

(175)Yoon, T. H., K. Benzerara, S. Ahn, R. G. Luthy, T. Tyliszczak, and G. E. Brown, Jr., Nanometer-scale chemical heterogeneities of black carbon materials and their impacts on PCB sorption properties: Soft x-ray spectromicroscopy study. Environ. Sci. Technol. 40(19), 5923-5929 (2006).

(176)Yoon, T. H., S. B. Johnson, and G. E. Brown, Jr., Adsorption of Suwannee River Fulvic Acid on mineral surfaces: An in situ ATR-FTIR study. Langmuir Lett. 20(14), 5655-5658 (2004).

(177)Yoon, T. H., S. B. Johnson, and G. E. Brown, Jr., Adsorption of organic matter at mineral/water interfaces: 4. Adsorption of humic acid at boehmite-water interfaces and impact on boehmite dissolution. Langmuir 21(11), 5002-5012 (2005).

(178)Yoon, T. H., S. B. Johnson, C. S. Doyle, K. Benzerara, T. Tyliszczak, D. K. Shuh, and G. E. Brown, Jr., In-situ characterization of aluminum-containing mineral-microorganism aqueous suspensions using scanning transmission x-ray microscopy. Langmuir Lett. 20(24), 10361-10366 (2004).

(179)Yoon, T. H., S. B. Johnson, C. B. Musgrave, and G. E. Brown, Jr., Adsorption of organic matter at mineral/water interfaces: I. ATR-FTIR spectroscopic and quantum chemical study of oxalate adsorbed at boehmite/water and corundum/water interfaces. Geochim. Cosmochim. Acta 68, 4505-4518 (2004).

(180)Yoon, T. H., T. P. Trainor, P. J. Eng, J. R. Bargar, and G. E. Brown, Jr., Trace element partitioning at polymer film-metal oxide interfaces: Long-period x-ray standing wave (XSW) study on the partitioning of Pb(II) and As(V) ions at mineral-PAA film interfaces. Langmuir 21, 4503-4511 (2005).

B. Manuscripts Submitted for Publication and in Review (1) K. Benzerara, N. Menguy, M. Obst, T. Tylisczak, G. E. Brown, Jr., and A.

Meibom, Nanoscale skeletal architecture of a scleractinian coral. Earth Planet. Sci. Lett. (submitted).

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(2) S. Bernard, K. Benzerara, O. Beyssac, and G.E. Brown, Jr., Multiscale characterization of pyritized plant tissues in high-grade metamorphic rocks. Geochim. Cosmochim. Acta (submitted).

(3) S. Bernard, O. Beyssac, K. Benzerara, N. Findling, G. Tzvetkov, and G.E. Brown, Jr., NEXAFS, Raman, and XRD signatures of anthracene-based cokes and saccharose-based chars subimitted to high temperature pyrolysis. Carbon (submitted).

(2) H. Bluhm, Photoemission spectroscopy under humid conditions. J. Electron Spectrosc. Relat. Phenom. (submitted).

(3) D. Fandeur, F. Juillot, G, Morin, S.M. Webb, J-L. Hazemann, O. Proux, L. Olivi, A. Cognigni, J-P. Ambrosi, E. Fritsch, F. Guyot, and G. E. Brown, Jr., Cr(VI) scavenging at the goethite surface after natural oxidation of Cr(III) by Mn-oxides in a lateritic regolith from New Caledonia. Geochim. Cosmochim. Acta (submitted).

(4) Ghose, S. K., G. A. Waychunas, P. J. Eng, T. P. Trainor, Ordered water and surface functional groups on hydrated goethite (100) surfaces. Geochim. Cosmochim. Acta (submitted).

(5) Ha, J., C. Cordova, T.H. Yoon, T. Tyliszczak, Y. Wang, A. M. Spormann, and G. E. Brown, Jr., Microbial reduction of hematite nanoparticles and microparticles by Shewanella oneidensis MR-1 and EPS-defficient strains: Macroscopic, -XRD, and STXM study. Langmuir (submitted).

(6) Ilton, E. S., Boily, J.-F., Skomurski, F. N., Rosso, K. M., Cahill, C. L., Bargar, J. R., and Felmy, A. R., The influence of dynamical processes at the magnetite-solution interface on the reduction of U(VI). Environ. Sci. Technol. (submitted).

(7) Masue-Slowey, Y., B. D. Kocar, C. Pallud, and S. Fendorf, Dependence of arsenic fate and transport on biogeochemical heterogeneity arising from physical structure of soils and sediments. Environ. Sci. Technol. (submitted).

(8) Michel, F. M., V. Barrón, J. Torrent, C. J. Serna, M. P. Morales, A. Ambrosini, Q. S. Liu, J-F. Boily, C. A. Cismasu, and G. E. Brown, Jr., Ordered ferrimagnetic form of ferrihydrite reveals link between structure and magnetism. Proc. Nat. Acad. Sci. U.S.A. (2010, accepted).

(9) Myneni, S. C. B., Applications of X-ray and infrared spectroscopy and spectromicroscopy methods in studying microbe-mineral interfaces. In: X-ray Spectromicroscopy & Environmental Sciences, Springer, NY (submitted).

(10) J.T. Newberg, D.E Starr, S. Posgaard, S. Yamamoto, S. Kaya, T. Kendelewicz, E. Mysak, M.B. Salmeron, A. Nilsson, G.E. Brown, Jr., and H. Bluhm, Water reaction with MgO(100) probed by ambient pressure XPS. J. Phys. Chem. C. (submitted).

(10) Nico, P. S., and B. D. Stewart, and S. Fendorf, Incorporation of uranium(VI) into Fe(hydr)oxides during Fe(II)-catalyzed remineralization. Environ. Sci. Technol (submitted).

(11) Pallud, C., M. Kausch, S. Fendorf, and C. Meile, Spatial patterns of iron transformations within artificial soil aggregates: Experimental and modeling analysis of diffusion limited iron cycling. Environ. Sci. Technol. (submitted).

(12) Pallud, C., Y. Masue-Slowey, and S. Fendorf, Aggregate-scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from coupled biogeochemical and physical processes. Geochim. Cosmochim. Acta (submitted).

(13) Petitto, S. C., K. S. Tanwar, S. K. Ghose, P. J. Eng, and T. P. Trainor, Surface structure of magnetite (111) by crystal truncation rod diffraction. Surf. Sci. (submitted).

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(14) Revill, K. L., M. A. Ginder-Vogel, S. Fendorf, Competitive microbial reduction of U(VI) and Fe(III): Biofilm influence on substrate availability and utilization. Environ. Sci. Technol. (submitted).

(15) T. Schiros, L-Å. Näslund, D. Nordlund, O. Takahashi, H. Ogasawara, A. Nilsson and L. G. M. Pettersson, When water isn’t wet: Origin of the hydrophobic monolayer. Phys. Chem. Chem. Phys. (submitted).

(16) Schiros, T., H. Ogasawara, K. Andersson, J. B. MacNaughton, H. Öström, O. Takahashi, L. G. M. Pettersson and A. Nilsson, Unique water-water coordination tailored by a metal surface. Phys. Rev. Lett. (submitted).

(17) Schiros, T., O. Takahashi, K. Andersson, H. Öström, L. G. M. Pettersson, A. Nilsson and H. Ogasawara, The role of substrate electrons in the wetting of a metal surface. J. Chem. Phys. (submitted).

(18) Schuetz, B., A. Spormann, and J. Gescher, MtrA and FccA in periplasmic electron transfer in Shewanella oneidensis MR-1. J. Bacteriol. (2009, submitted).

(19) Skomurski, F. N., S. N. Kerisit, and K. M. Rosso, Structure, charge distribution, and electron hopping dynamics in magnetite (Fe3O4) (100) surfaces from first principles. Geochim. Cosmochim. Acta. (submitted).

(20) Stewart, B. D., R. T. Amos, and S. Fendorf, Simultaneous microbial reduction of uranium(VI) and iron(III). J. Environ. Qual. (submitted).

(21) Stewart, B. D., M. A. Mayes, and S. Fendorf, Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments. Environ. Sci. Technol. (submitted)

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APPENDIX B: PRESENTATIONS OF STANFORD EMSI-SUPPORTED RESEARCH AT SCIENTIFIC MEETINGS

(Presenter in blue type, EMSI PI’s in bold-face type; names of graduate students, post-doctoral students, and undergraduate students are underlined)

A. Stanford EMSI-Related Presentations by Brown Group (June 2006 - July 2009)

• Banerjee, Neil R., Benzerara, Karim, Menguy, Nicolas, and Brown, Gordon E., Jr. (Contributed Talk): “Nanometer-scale Study of Microbial Alteration Textures in Submarine Basaltic Glass,” American Geophysical Union Fall Annual Meeting, San Francisco, CA, Dec. 2006.

• Benzerara, Karim, Sylvan Bernard, Kevin Lepot, Jennyfer Miot, and Gordon E. Brown, Jr. (Contributed Talk): “STXM-based Study of Microbial Fossils in Recent and Ancient Rocks,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

• Benzerara, Karim, Anders Miebom, Purificacion Lopez-Garcia, Josef Kazmierczak, and Gordon E. Brown, Jr. (Invited Talk): “Study of Mineral-Microbe Assemblages Down to the nm-Scale in Carbonate Microbialites,” 19th Goldschmidt Conference, Davos, Switzerland, June 2009.

• Benzerara, Karim, Jennyfer Miot, and Gordon E. Brown, Jr. (Invited Talk): “Impact of Microbes on Fe Redox Cycles in the Environment,” Workshop on STXM and X-ray Nanoprobe Capabilities and Needs for Geo-, Environmental, and Biological Sciences, Stanford, CA, July 2007.

• Benzerara, Karim, Tyliszczak, Tolek, and Brown, Gordon E., Jr. (Invited Talk): “Study of Interactions Between Microbes and Minerals by Scanning Transmission X-ray Microscopy (STXM),” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Benzerara, Karim, Menguy, Nicolas, Lepot, Kevin, and Brown, Gordon E., Jr. (Contributed Talk): “Study of Bioweathering and Nano-biominerals at the Nanoscale in Natural Samples,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, United States, Sept. 10-14, 2006, GEOC-127.

• Benzerara, Karim, Jennyfer Miot, Neil R. Banerjee, Nicolas Menguy, Tolek Tyliszczak, Gordon E Brown, Jr., and Francois Guyot (Contributed Talk): “Study at the Nanoscale of the Alteration of Submarine Basaltic Glass from the Ontong Java Plateau,” 17th Goldschmidt Conference, Cologne, Germany, August 2007.

• Benzerara, Karim, Yoon, Tae-Hyun, Singer, David M., Menguy, Nicolas, Lepot, Kevin, Philipot, Pascal, Morin, Guillaume, Juillot, Farid, Calas, Georges, Tyliszczak, Tolek, and Brown, Gordon E., Jr. (Invited Talk): “Synchrotron X-ray Spectromicroscopy Studies of Minerals and Biominerals in Complex, Multi-phase Samples”, U.C. Berkeley Workshop on Imaging Complex Pore Structure of Cement, Berkeley, CA, April 2008.

• Bernard, Sylvan, Karim Benzerara, Otto Beyssac, and Gordon E. Brown, Jr. (Contributed Talk): “Scanning Transmission X-ray Microscopy Analysis of Metamorphic Biogenic Carbon,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

• Bernard, Sylvan, Otto Beyssac, Karim Benzerara, Gordon E. Brown, Jr., S. Mostefaoui, Anders Meibom, and Bernard Goffe (Contributed Talk): “Imaging Traces of Life in Metamorphic Rocks Using Raman, STXM, and NanoSIMS,” 18th Goldschmidt Conference, Davos, Switzerland, June 2009.

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• Brown, Gordon E., Jr. (Invited Talk): “Stanford EMSI – Current and Future Research Efforts,” Workshop on the Development of New User Research Capabilities in Environmental Molecular Science, W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, August 2006.

• Brown, Gordon E., Jr. (Invited Talk): “Interfaces, Heavy Metals, Microbes, and Plants: Shedding New Light on Environmental Science at the Molecular Level,” Stanford-Berkeley Summer School in Applications of Synchrotron Radiation in the Physical Sciences, U.C. Berkeley, June 2006.

• Brown, Gordon E., Jr. (Keynote Talk): “Chemical and Microbial Processes at Environmental Interfaces – From Molecular to Field Scales,” Annual Meeting of the Center for Environmental Molecular Science, Stony Brook University, Stony Brook, NY, November 2006.

• Brown, Gordon E., Jr. (Invited Talk): "Environmental Interfaces, Heavy Metals, Microbes, and Plants: Shedding New Light on Environmental Science at the Molecular Level,” Arrhenius Laboratory, Chemistry Department, Stockholm University, Stockholm, Sweden, March 2007.

• Brown, Gordon E., Jr. (Plenary Lecture): “A Geochemists View of the Environment from the Molecular Perspective,” 17th Goldschmidt Conference, Patterson Medal Ceremony, Cologne, Germany, August 2007.

• Brown, Gordon E., Jr. (Invited Talk): Hudnall Symposium in Memory of Prof. Joseph V. Smith, “Applications of Synchrotron Radiation to Earth Materials”, Department of the Geophysical Sciences, University of Chicago, Chicago, IL, October 2007.

• Brown, Gordon E., Jr. (Invited Talk): “Reminiscences of a Mineralogist Who Went Astray”, Third Roebling Medalist Lecture, Geological Society of America Annual Meeting, Denver, CO, October 2007.

• Brown, Gordon E., Jr. (Invited Talk):“A Case for Environmental Science at the ‘Next Generation’ Light Source”, LSU Workshop on Enabling Grand Challenge Science, The Light Source of the Future: Baton Rouge, LA, January 2008.

• Brown, Gordon E., Jr. (Invited Talk): “Applications of Synchrotron Radiation in the Environmental Sciences”, Stanford-Berkeley Summer School in Applications of Synchrotron Radiation in the Physical Sciences, Stanford Linear Accelerator Center and Stanford University, Stanford, CA, August 2008.

• Brown, Gordon E., Jr. (Invited Talk): “Applications of Synchrotron Radiation in the Earth, Environmental, and Energy Sciences,” Department of Earth & Environmental Sciences Colloquium, Ludwig Maxmillian University, Munich, Germany, June 2009.

• Brown, Gordon E., Jr., John R. Bargar, Karim Benzerara, Thomas Kendelewicz, Juyoung Ha, David M. Singer, Alexandre Gélabert, Yingge Wang, Thomas P. Trainor, Kunaljeet S. Tanwar, Anne M. Chaka, Peter J. Eng, Susumu Yamamoto, Anders Nilsson, Hendrik Bluhm, David E. Starr, Miquel Salmeron, Glenn A. Waychunas, Jeffrey G. Catalano, Tae- Hyun Yoon, Guillaume Morin, Georges Ona-Nguema, Jennyfer Miot, Sophie Lebrun, Farid Juillot, Francois Farges, Alfred M. Spormann, and Georges Calas (Invited Talk):“Molecular Environmental and Interface Science - Applications of Synchrotron X-rays to Pollutants and Their Interactions at Environmental Interfaces”, A Symposium on The Future of X-ray Science – in honor or Prof. Joachim Stohr, Director of SSRL, on his 60 th

birthday, SLAC, Stanford, CA, September 2007.

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• Brown, Gordon E., Jr., Benzerara, Karim, Yoon, Tae-Hyun, Ha, Juyoung, Cordova, Carmen D., Spormann, Alfred M., Tyliszczak, Tolek, Tanwar, Kunaljeet S., Trainor, Thomas P., Eng, Peter J., Kendelewicz, Tom, Yamamoto, Susumu, Bluhm, Hendrik, Starr, David E., Ketteler, Guido, Salmeron, Miquel, and Nilsson, Anders (Contributed Talk): “Applications of Synchrotron Radiation Methods to Processes at Environmental Interfaces,” Symposium on Applications of Synchrotron Radiation in Environmental Geochemistry, 16 th Goldschmidt Conference, Melbourne, Australia, September 2006.

• Brown, Gordon E., Jr., Benzerara, Karim, Yoon, Tae-Hyun, Ha, Juyoung, Cordova, Carmen D., Spormann, Alfred M., Morin, Guillaume, Calas, Georges, and Tyliszczak, Tolek (Invited Talk): “Soft X-ray Spectromicroscopy Studies of Environmental Interfaces,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept. 10-14, 2006, COLL-418.

• Brown, Gordon E., Jr., Benzerara, Karim, Yoon, Tae-Hyun, Ha, Juyoung, Cordova-Ardy, Carmen D., Spormann, Alfred M., Morin, Guillaume, Calas, Georges, and Tyliszczak, Tolek (Invited Talk): “Soft X-ray Spectromicroscopy Studies of Microbial Processes at Environmental Interfaces,” Energy Recovery Linac Workshop on Frontier Applications of X-ray Science in Biology, Cornell University, Ithaca, NY, June 2006.

• Brown, Gordon E., Jr., Francois Farges, Anders Nilsson, and Lars G. M. Pettersson (Invited Talk): “Structural Models of Silicate Melts and Water from Spectroscopic and Scattering Studies”, DOE-BES Workshop on Molecular Dynamics and Structure of Geofluids, Claremont Resort, Berkeley, CA, December 2007.

• Brown, Gordon E., Jr., Alexandre Gélabert, Yingge Wang, Cristina Cismasu, Juyoung Ha, Georges Ona-Nguema, Karim Benzerara, Guillaume Morin, Yuheng Wang, Farid Juillot, Francois Guyot, Georges Calas, Tae-Hyun Yoon, John R. Bargar, Peter J. Eng, Alexis S. Templeton, Thomas P. Trainor, and Alfred M. Spormann (Keynote Talk): “Synchrotron X-ray Studies of Bacteria-Mineral-Metal Ion Interactions,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

• Brown, Gordon E., Jr., Juyoung Ha, David M. Singer, Yingge Wang, Alexandre Gélabert, Francois Farges, Thomas P. Trainor, John R. Bargar, Peter J. Eng, and Alfred M. Spormann (Invited Paper): “Interaction of Zn(II)aq with Mineral Nano-and Microparticles, Bacterial Surfaces, and Biofilm-Coated Metal Oxides,” American Chemical Society 237th

National Meeting, Salt Lake City, UT, March 2009.• Brown, Gordon E., Jr., Juyoung Ha, Alexandre Gélabert, David M. Singer, Yingge Wang,

John R. Bargar, Peter J. Eng, Yong Choi, Tom Kendelewicz, and Alfred M. Spormann (Contributed Talk): “Sorption Processes on Small and Dirty Mineral Particles – Do Size and Cleanliness Matter?” 19th Goldschmidt Conference, Davos, Switzerland, June 2009.

• Brown, Gordon E., Jr., Adam D. Jew, Aaron J. Slowey, Christopher S. Kim, Gregory V. Lowry, Sam Shaw, Mae S. Gusin, and James J. Rytuba (Invited Talk): “Mercury Pollution in California: From Subduction to Mercury in Tuna,” EAWAG Seminar (Swiss Federal Institute of Aquatic Science & Technology), Dubendorf, Switzerland, November 2008.

• Brown, Gordon E., Jr., Adam D. Jew, Aaron J. Slowey, Christopher S. Kim, Gregory V. Lowry, Sam Shaw, Mae S. Gusin, and James J. Rytuba (Invited Talk): “Mercury Pollution in California: From Subduction to Mercury in Tuna,” Department of Earth Sciences Colloquium, Washington University, St. Louis, St. Louis, MO, April 2009.

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• Brown, Gordon E., Jr., Tom Kendelewicz, Thomas P. Trainor, Kunaljeet S. Tanwar, Anne M. Chaka, Peter J. Eng, Susumu Yamamoto , Anders Nilsson, Hendrik Bluhm, David E. Starr, Miquel Salmeron, Jeffrey G. Catalano, Tae-Hyun Yoon, Karim Benzerara, Guillaume Morin, Georges Ona-Nguema, Farid Juillot, Benjamin Cances, Francois Farges, and Georges Calas (Plenary Lecture): “Recent Advances in Surface, Interface, and Environmental Geochemistry,” 12th International Symposium on Water-Rock Interaction, Kunming, China, August 2007.

• Brown, Gordon E., Jr., Aaron Slowey, Adam Jew, Christopher S. Kim, Greg V. Lowry, Sam Shaw, Mae S. Gustin, and James J. Rytuba (Invited Talk): “Mercury Speciation in Mining Environments,” 17th Goldschmidt Conference, Symposium on Speciation and Reactivity of Trace Elements in Natural Environments, Cologne, Germany, August 2007.

• Brown, Gordon E., Jr., Thomas P. Trainor, Peter J. Eng, Anne M. Chaka, Jeffrey G. Catalano, Tae-Hyun Yoon, Stephen B. Johnson, Tom Kendelewicz, Susumu Yamamoto, Hendrik Bluhm, David E. Starr, and Anders Nilsson (Keynote Talk): “Factors Controlling the Reactivity of Metal Oxide Surfaces,” Australian Colloid and Interface Symposium – Inorganic Oxide Surfaces, Sydney, Australia, February 2007.

• Brown, Gordon E., Jr., Thomas P. Trainor, Peter J. Eng, Anne M. Chaka, Jeffrey G. Catalano, Tae-Hyun Yoon, Stephen B. Johnson, Tom Kendelewicz, Susumu Yamamoto, Hendrik Bluhm, David E. Starr, and Anders Nilsson (Invited Talk): “Factors Controlling Chemical Reactivity at Metal Oxide-Aqueous Solution Interfaces,” Session on Inorganic Interfaces and Biology, 1st ERA-Chemistry Flash Conference, L’Escandille, Autrans, France, March 2007.

• Brown, Gordon E., Jr., Thomas P. Trainor, Peter J. Eng, Anne M. Chaka, Jeffrey G. Catalano, Tae-Hyun Yoon, Stephen B. Johnson, Tom Kendelewicz, Susumu Yamamoto, Hendrik Bluhm, David E. Starr, and Anders Nilsson (Invited Talk): “Factors Controlling Chemical Reactivity at Metal Oxide-Aqueous Solution Interfaces,” Department of Chemistry Seminar, Universite Pierre et Marie Curie, Paris VI, Paris, France, March 2007.

• Brown, Gordon E., Jr., Thomas P. Trainor, Peter J. Eng, Anne M. Chaka, Thomas Kendelewicz, Susumu Yamamoto, Hendrik Bluhm, David E. Starr, Juyoung Ha, Yingge Wang, Alexandre Gélabert, and Anders Nilsson (Invited Talk): “Factors Controlling the Reactivity of Metal Oxide Surfaces”, Geochemistry Division Symposium on Advanced Approaches to Investigating Adsorption at the Solid-Water Interface, American Chemical Society 235th National Meeting, New Orleans, LA, April 2008.

• Brown, Gordon E., Jr., Yingge Wang, Alexandre Gélabert, Cristina Cismasu, Juyoung Ha, Georges Ona-Nguema, Karim Benzerara, Guillaume Morin, Yuheng Wang, Farid Juillot, Francois Guyot, Georges Calas, Tae-Hyun Yoon, John R. Bargar, Peter J. Eng, Alexis S. Templeton, Thomas P. Trainor, and Alfred M. Spormann (Invited Talk): “Microbial and Chemical Interactions at Mineral Surfaces and Their Impact on Trace Element Cycling,” ETH-Zurich, Department of Environmental Sciences, Zurich, Switzerland, November 2008.

• Brown, Gordon E., Jr., Yingge Wang, Alexandre Gélabert, Juyoung Ha, Cristina Cismasu, Georges Ona-Nguema, Karim Benzerara, Jennyfer Miot, Yuheng Wang, Nicolas Menguy, Guillaume Morin, Farid Juillot, Francois Guyot, Georges Calas, Francois Farges, Thomas P. Trainor, Johannes Gescher, Carmen Cordova, and Alfred M. Spormann (Invited Talk): “Synchrotron X-ray Studies of Heavy Metal-Mineral-Microbe Interactions,” Geochemistry of Earth’s Surface 8, London, U.K., August 2008.

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• Brown, Gordon E., Jr., Tae-Hyun Yoon, Stephen B. Johnson, David M. Singer, Juyoung Ha,

Yingge Wang, Alexandre Gélabert, Karim Benzerara, Thomas P. Trainor, and Alfred M. Spormann (Keynote Talk): “Interaction of Organic Molecules and Microorganisms with Mineral Surfaces and Their Impact on Metal Ion Sorption Processes,” Frontiers in Mineral Sciences 2007 Conference, Cambridge, U.K., June 2007.

• Catalano, Jeffrey G., David M. Singer, Thomas P. Trainor, Francois Farges, Steven M. Heald, Peter J. Eng, John M. Zachara, and Brown, Gordon E., Jr. (Invited Talk): “Uranium Speciation in Contaminated Sediments: XAFS Studies of Model and Natural Systems,” Glen T. Seaborg Institute for Transactinium Science Seminar Series, Lawrence Berkeley National Laboratory, Berkeley, CA, January 2007.

• Catalano, Jeffrey G., David M. Singer, Thomas P. Trainor, Francois Farges, Steven M. Heald, Peter J. Eng, John M. Zachara, and Brown, Gordon E., Jr. (Invited Talk): “Uranium Speciation in Contaminated Sediments: XAFS Studies of Model and Natural Systems,” Institut de Minéralogie et de Physique des Milieux Condensés, Boucicaut Campus, University of Paris VI-VII, Paris, France, March 2007.

• Cismasu, Cristina, F. Marc Michel, Jonathan F. Stebbins, A. Patricia Tcaciuc, and Gordon E. Brown, Jr. (Poster): “Molecular- and nm-scale Investigations of the Structure and Compositional Heterogeneity of Naturally Occurring Ferrihydrite,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2008.

• Cismasu, Cristina, F. Marc Michel, Jonathan F. Stebbins, A. Patricia Tcaciuc, and Gordon E. Brown, Jr. (Poster): “Molecular- and nm-scale Investigation of the Structure and Compositional Heterogeneity of Naturally Occurring Ferrihydrite,” American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

• Cismasu, Cristina, Georges Ona-Nguema, Dominic Bonin, Micolas Menguy, and Gordon E. Brown, Jr. (Contributed Talk): “Zinc and Arsenic Immobilization and Magnetite Formation Upon Reducction of Maghemite by S. putrifaciens,” Goldschmidt 2008 Conference, Vancouver, B.C., Canada, August 2008.

• Fandeur, Dik, Farid Juillot, Emannuel Fritsch, L. Olivi, Guillaume Morin, Gordon E. Brown, Jr., Samuel Webb, and Jean-Paul Ambrosi (Contributed Talk): “Cr Behavior after Oxidation by Mn-Oxides Along a Weathering Profile in New Caledonia,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

• Fandeur, Dik, Farid Juillot, Guillaume Morin, Samuel Webb, L. Olivi, Jean-Louis Hazemann, Gordon E. Brown, Jr., and Emmanuel Fritsch (Contributed Talk): “XANES Investigation of the Redox Behavior of Cr in a Tropical Context,” 19th Goldschmidt Conference, Davos, Switzerland, June 2009.

• Farges, Francois and Brown, Gordon E., Jr. (Poster): “Ti, Cr, and REE’s in Borosilicate Melts: Comparison with Quenched Glasses,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Farges, Francois, Benzerara, Karim, and Brown, Gordon E., Jr. (Poster): “Chrysocolla Redefined as Spertiniite,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Farges, Francois, Trocellier, P., Curti, E., Etcheverry, M.-P., and Brown, Gordon E., Jr. (Plenary Lecture): “Durability of Silicate Glasses: An Historical Outlook,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

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• Gélabert, Alexandre, Yingge Wang, Johannes Gescher, Juyoung Ha, Carmen D. Cordova, David M. Singer, Alfred M. Spormann, Thomas P. Trainor, Peter J. Eng, and Gordon E. Brown, Jr. (Contributed Talk): “Trace Element Speciation and Distribution Study at Shewanella oneidensis MR-1 Biofilm/Mineral/Water Interfaces,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2006.

• Gélabert, Alexandre, Yingge Wang, Juyoung Ha, Georges Ona-Nguema, Alfred M. Spormann, John R. Bargar, Peter J. Eng, Sanjit K. Ghose, and Gordon E. Brown, Jr. (Contributed Talk): “Parameters Controlling Trace Metal Adsorption at the Biofilm/Mineral Interface Based on Long-Period X-ray Standing Wave Fluorescence Yield (XSW-FY) Spectroscopy: Comparison with a Thermodynamic Approach,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

• G é labert , Alexandre , Yingge Wang, Georges Ona-Nguema, Juyoung Ha, Carmen Cordova-Ardy, Johannes Gescher, John R. Bargar, Francois Farges, Alfred M. Spormann, and Gordon E. Brown, Jr. (Contributed Talk): “Adsorption of Metal Cations on Shewanella oneidensis surfaces: II. Impact of Biofilm Coatings on Mineral Surface Reactivity,” Frontiers in Mineral Sciences 2007, Cambridge, UK, June 2007.

• Ha, Juyoung, Carmen Cordova-Ardy, Tae-Hyun Yoon, Francois Farges, Alfred M. Spormann, and Brown, Gordon E., Jr. (Invited Talk): “Reactivity of Hematite Nanoparticles in the Presence of Zn(II)aq and Shewanella oneidensis,” Workshop on Colloidal Ceramic Processing - The Role of Interfaces, University of Melbourne, Melbourne, Australia, February 2007.

• Ha, Juyoung, Farges, Francois, and Brown, Gordon E., Jr. (Contributed Talk): Adsorption and Precipitation of Zn(II)aq on Hematite Nano- and Macroparticles,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Ha, Juyoung, Farges, Francois, and Brown, Gordon E., Jr. (Contributed Talk): Adsorption and “Precipitation of Zn(II)aq on Hematite Nano- and Macroparticles,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, United States, Sept. 10-14, 2006, COLL-224.

• Ha, Juyoung, Cordova, Carmen D., Yoon, Tae-Hyun, Spormann, Alfred M., and Brown, Gordon E., Jr. (Contributed Talk): “Microbial Reduction of Hematite: Effects of Particle Size and Exopolysaccharides,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, United States, Sept. 10-14, 2006, COLL-082.

• Ha , Juyoung , Francois Farges, Thomas P. Trainor, and Gordon E. Brown, Jr. (Contributed Talk): “Adsorption of Zn(II) on Oxalate-Coated Hematite (a-Fe2O3) Nano- and Micro-particles,” Frontiers in Mineral Sciences 2007, Cambridge, UK, June 2007.

• Ha, Juyoung, Alex andre G é labert , Yingge Wang, Alfred M. Spormann, and Gordon E. Brown, Jr. (Contributed Talk): “Adsorption of Metal Cations on Shewanella oneidensis Surfaces: I. Determination of Metal Binding Sites Using Spectroscopic and Modeling Approaches,” Frontiers in Mineral Sciences 2007, Cambridge, UK, June 2007.

• Ha, Juyoung, Alex andre G é labert , Yingge Wang, Alfred M. Spormann, and Gordon E. Brown, Jr. (Contributed Talk): “Study of Proton, Pb2+, and Zn2+ Adsorption onto Shewanella oneidensis MR-1 Strain and a Mutant Strain (ΔEPS): Spectroscopic Observation and Modling Approach,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

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• Ha, Juyoung, Thomas P. Trainor, Francois Farges, Carmen Cordova, Tae-Hyun Yoon, Tolek Tyliszczak, Yingge Wang, Alfred M. Spormann, and Gordon E., Brown, Jr. (Contributed Talk): “Study of Hematite Nanoparticle Interaction with Zn(II), Oxalate, and Shewanella oneidensis using ATR-FTIR, EXAFS, and STXM.” American Geophysical Union Fall Meeting, San Francisco, CA, December 2008.

• Harfouche, Messaoud, Farges, Francois, Munoz, Manuel, Wilke, Max, and Brown, Gordon E., Jr. (Poster): “On the Coordination of Tetravalent Actinides in Silicate Glasses and Melts: The Titanite View,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Hullebusch, Eric van, Farges, Francois, Lenz, Mark, Lens, Piet, and Brown, Gordon E., Jr., “Selenium Speciation in Biofilms from Granular Sludge Bed Reactors Used for Wastewater Treatment,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Jew, Adam D., Christopher S. Kim, James J. Rytuba, Mae S. Gustin, and Gordon E. Brown, Jr. (Contributed Talk): “EXAFS of Frozen Elemental Mercury and Its Implications for Abandoned Mercury Mine Wastes,”San Francisco Estuarine Institute Mercury Coordination Meeting, San Francisco, CA, February 2009.

• Jew, Adam D., Christopher S. Kim, James J. Rytuba, Mae S. Gustin, and Gordon E. Brown, Jr. (Contributed Talk): “EXAFS of Frozen Elemental Mercury and Its Implications for Abandoned Mercury Mine Wastes,” International Conference on Mercury as a Global Pollutant. Guiyang, China, June 2009.

• Jew, Adam D., Samia B. Rogers, James J. Rytuba, Alfred M. Spormann, and Gordon E. Brown, Jr. (Poster): “Bacterially Mediated Breakdown of Cinnabar and Metacinnabar and Environmental Implications,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2006.

• Juillot, Farid, Morin, Guillaume, Hazemann, Jean-Louis, Proux, Olivier, Belin, S., Briois, V., Brown, Gordon E., Jr., and Calas, Georges (Poster): “EXAFS Signatures of Structural Zn at Trace Concentration Levels in Layered Minerals,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Kendelewicz, Tom, Sarp Kaya, John T. Newberg, Hendrik Bluhm, Anders Nilsson, Rossitza Pentcheva, Wolfgang Moritz, and Gordon E. Brown, Jr. (Contributed Talk): “Photoemission Study of the Reaction of Fe3O4(100) with Water at Near Ambient Conditions.” 19th Goldschmidt Conference, Davos, Switzerland, June 2009.

• Kendelewicz, Tom, Susumu Yamamoto, Hendrik Bluhm, Guido Ketteler, Klas Andersson, David E. Starr, Miquel Salmeron, Anders Nilsson, and Gordon E. Brown, Jr. (Contributed Talk): “Reaction of molecular water with (0001) surfaces of hematite (Fe2O3): a high pressure XPS study,” 24th European Conference on Surface Science, Paris, France, September 4-8, 2006.

• Kendelewicz, Tom, Susumu Yamamoto, Sarp Kaya, John T. Newberg, Hendrik Bluhm, Anders Nilsson, and Gordon E. Brown, Jr. (Contributed Talk): “Photoemission Study of Water Reaction with (100) and (111) Surfaces of Magnetite Under Near-Ambient Conditions,” 26th European Conference on Surface Science (ECOSS-26), Parma, Italy, August 2009.

• Michel, F. Marc, Cristina Cismasu, John B. Parise, and Gordon E. Brown, Jr. (Invited Talk): “Evaluating the Structure of Poorly Crystalline Iron Oxyhydroxides,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

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• Michel, F. Marc, Cristina Cismasu, Daniel R. Strongin, John B. Parise, and Gordon E. Brown, Jr. (Invited Talk): “Real-Space Structural Analysis of Ferrihydrite Nanoparticles,” American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

• Michel, F. Marc, Cristina Cismasu, A. Patricia Tcaciuc, John B. Parise, and Gordon E. Brown, Jr. (Contributed Talk): “Structural Aspects of Synthetic Ferrihydrite,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2008.

• Miot, Jennyfer, Karim Benzerara, Guillaume Morin, Andreas Kappler, Martin Obst, Gordon E. Brown, Jr., and Francois Guyot (Contributed Talk): “Iron Biomineralization by Neutrophilic Nitrate-Reducing Iron-Oxidizing Bacteria,” 19th Goldschmidt Conference, Davos, Switzerland, June 2009.

• Morin, Guillaume, Benzerara, Karim, Miot, Jennyfer, Casiot, C., Bruneel, O., Calas, Georges, Brown, Gordon E., Jr. (Contributed Talk): “Bacterial Formation of Arsenic Ion Hydroxysulfates in Acid Mine Drainage,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Morin, Guillaume, Georges Ona-Nguema, Yuheng Wang, and Gordon E. Brown, Jr. (Contributed Talk): “Mechanisms of Arsenite Sequestration by Fe(II)-(hydr)oxides After (Bio)reduction of Fe(III)-Oxyhydroxides,” American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

• Morin, Guillaume, Georges Ona-Nguema, Yuheng Wang, Farid Juillot, Nicolas Menguy, Georges Calas, and Gordon E. Brown, Jr. (Contributed Talk): “Arsenic(III) Polymerization Upon Sorption of Iron(II,III)-(Hydr)oxide Surfaces - Implications for Arsenic Mobilty Under Reducing Conditions,” 18th Goldschmidt Conference, Davos, Switzerland, June 2009.

• Ona-Nguema, Georges, Guillaume Morin, Yuheng Wang, Farid Juillot, Francois Guyot, Georges Calas, and Gordon E. Brown, Jr. (Contributed Talk): “As(V)-bearing Lepidocrocite and Green Rust Reduction by Shewanella putrefaciens: Evidence for Fe(II) Carbonate Hydroxide Formation,” Goldschmidt 2007 Conference, Cologne, Germany, August 2007.

• Ona-Nguema, Georges, Guillaume Morin, Yuheng Wang, Farid Juillot, M. Abdelmoula, C. Ruby, Francois Guyot, Georges Calas, and Gordon E. Brown, Jr. (Contributed Talk): “Arsenite Sequestration by Fe(II)-Containing Minerals after Microbial Dissimilatory Reduction of Arsenic-Sorbed Lepidocrocite,” 18th Goldschmidt Conference, Davos, Switzerland, June 2009.

• Siebner, Hagar, Samuel M. Webb, and Gordon E. Brown, Jr. (Poster): “Mercury retention and accumulation by plants at the abandoned New Idria Mine Site: A Preliminary XRF and XRD Study,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2008.

• Siebner, Hagar, Samuel M. Webb, and Gordon E. Brown, Jr. (Poster): “Mercury Accumulation in Plant Roots at the Abandoned New Idria Mine Site,” American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

• Singer, David M., Farges, Francois, and Brown, Gordon E., Jr. (Poster): “Biogenic UO2 – Characterization and Reactivity,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Singer, David M., Kate Maher, and Gordon E. Brown, Jr. (Contributed Talk): “Uranyl-Chlorite Sorption/Desorption: Evaluation of Different Sorption Mechanisms,” Goldschmidt 2008 Conference, Vancouver, B.C., Canada, August 2008.

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• Singer, David M., Kate Maher, and Gordon E. Brown, Jr. (Contributed Talk): “Uranyl-Chlorite Sorption/Desorption: Evaluation of Different Sorption Mechanisms,” American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

• Slowey, Aaron J. and Brown, Gordon E., Jr. (Poster): “Transformations of Mercury During Reductive Dissolution of Iron-oxyhydroxide by Sulfide,” 13th International Conference on X-ray Absorption Fine Structure (XAFS), Stanford, CA, July 10-14, 2006.

• Van der Hoven, Mary T., Shela Aboud, Jennifer Wilcox, Michael Odelius, and Gordon E. Brown, Jr. (Poster): “Modeling the Interaction of UO2

2+ with Corundum and Hematite Surfaces,” American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

• Wang, Yingge, Alexandre Gélabert, Yong Choi, Juyoung Ha, Johannes Gescher, Carmen Cordova, John R. Bargar, Joe Rogers, Peter J. Eng, Francois Farges, Alfred M. Spormann, and Gordon E. Brown, Jr. (Contributed Talk): “The Impact of S. oneidensis MR-1 Biofilm Coatings on the Reactivity of Hematite,” American Chemical Society 237th National Meeting, Salt Lake City, UT, March 2009.

• Wang, Yingge, Alexandre Gélabert, Juyoung Ha, Georges Ona-Nguema, Johannes Gescher, Carmen Cordova, John R. Bargar, Joe Rogers, Peter J. Eng, Sanjit K. Ghose, Alfred M. Spormann, and Gordon E., Brown, Jr. (Contributed Talk): “Impact of S. oneidensis MR-1 Biofilm Coatings on Trace Element Partitioning at Metal-Oxide/Water Interfaces: A Long-Period XSW-FY Study,” 18th Goldschmidt Confernece, Vancouver, B.C., Canada, August 2008.

• Wang, Yingge, Georges Ona-Nguema, Alex andre G é labert , Alfred M. Spormann, and Gordon E. Brown, Jr. (Poster): “Evidence for Arsenate Detoxification by Shewanella oneidensis Strain MR-1 Using X-ray Absorption Spectroscopy,” Frontiers in Mineral Sciences 2007, Cambridge, UK, June 2007.

• Wang, Yuheng, Guillaume Morin, Georges Ona-Nguema, Nicolas Menguy, Francois Guyot, Jean-Louis Hazemann, Georges Calas, and Gordon E. Brown, Jr. (Poster): “Mechanisms of Arsenic Scavenging by Iron (Hydro)oxides in Anoxic Environments,” 17th Goldschmidt Conference, Symposium on Speciation and Reactivity of Trace Elements in Natural Environments, Cologne, Germany, August 2007.

• Yoon, Jihae, Juyoung Ha, Gordon E. Brown, Jr., and Jinyeon Hwang (Poster): “Characteristics of Organobentonite and Study of Iodide Adsorption on Organibentonite Using X-ray Absorption Spectroscopy,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2008.

B. Stanford EMSI-Related Presentations by the Fendorf Group (January 2005 - July 2008)

• S. Fendorf (Invited Talk): “Processes Governing the Largest Mass Poisoning in History: Arsenic in Drinking Water of Asia,” University of Delaware, 2005.

• S. Fendorf (Invited Talk): “Integrated Process Controls on Elemental Cycling within the Critical Zone,” National Science Foundation Workshop on “Frontiers in Exploration of the Critical Zone”, University of Delaware, 2005.

• S. Fendorf (Invited Talk): “Gaining a Molecular-Level Understanding of Processes Governing the Fate and Transport of Ions/Chemical within Soils,” Frontiers in Soil Science Research, National Academy of Sciences, Washington, DC, 2005.

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• S. Fendorf, C. M. Hansel, and S. G. Benner (Invited Talk): “Biotransformation Rates of Iron Governing Chromium and Uranium Transport,” American Geophysical Union Fall Meegting, San Francisco, CA, December 2005.

• S. Fendorf (Invited Talk): “Biogeochemical Processes Governing the Fate of Chromium and Uranium within Soils and Waters,” Stanford Environmental Engineering and Science Seminar Series, 2006.

• S. Fendorf (Invited Talk): “Dependency of Electron Transfer Rates on Changing and Localized Solid Phase Chemistry,” Biogeochemical Grand Challenge, Pacific Northwest National Laboratory, 2006.

• S. Fendorf (Invited Talk): “Heterogeneity in Biogeochemical Processes Impacting Contaminant Fate and Transport,” DOE Environmental Remediation Science Program Investigator Meeting, Warrenton, VA, 2006.

• S. Fendorf (Invited Talk): “Pathways of Ferric (Hydr)oxide Reductive Transformation and Impacts on Contaminant Transport,” Telluride Workshop: Iron Redox Chemistry at Environmentally Relevant Surfaces, Telluride, CO, 2006.

• S. Fendorf (Invited Talk): “The Largest Mass Poisoning in History: Arsenic in Drinking Water,” Pinhead Institute’s Public Lecture, Telluride, CO, 2006.

• S. Fendorf, B. D. Kocar, K. J. Herbel, and M. J. Herbel (Invited Talk): “Biogeochemical Processes Governing the Cycling of Arsenic in Surface and Subsurface Environments,” American Chemical Society National Meeting, San Francisco, CA, 2006.

• S. Fendorf (Invited Talk): “Processes Governing the Transport of Arsenic: Contrasts Between the Mekong and Ganges-Brahmaputra Deltas,” Columbia University Earth Science Forum, 2006.

• B.D. Kocar, S. C. Ying, M. L. Pollizzotto, and S. Fendorf (Invited Talk): “Arsenic Release from Tropical Soils,” San Francisco State University, San Francisco CA, 2006.

• Masue, Y., T. Borch, and S. Fendorf (Invited Talk): “Factors Affecting Arsenic Retention under Anaerobic Conditions,” 4th Symposium of Kanazawa University Center of Excellence Program. Kanazawa, Japan, 2006.

• S. Fendorf (Invited Talk): “Biogeochemical Process Heterogeneity Impacting Contaminant Dynamics in Subsurface Environments,” DOE Environmental Remediation Science Program Meeting, Leesburg, VA, 2007.

• S. Fendorf (Invited Talk): “The Coupling of Physical, Chemical, and Biological Processes: Governing Controls on Water Quality,” Workshop on “Metals, Environment, and Human Health”, Stony Brook University, NY, 2007.

• S. Fendorf (Invited Talk): “Process Controlling the Migration of Arsenic in Southeast Asia,” Soil Science Society of America Annual Meeting, New Orleans, LA, 2007.

• S. Fendorf (Invited Talk): “Spatial and Temporal Variations in Biogeochemical Processes Influencing Arsenic Concentrations within the Mekong Delta,” Joint EAWAG/University of Manchester Workshop on Arsenic in Groundwaters of South-East Asia with Emphasis on Cambodia & Vietnam. Manchester, England, 2007.

• M. L. Polizzotto, Harvey, C., Badruzzaman, B., Ali, A., Benner, S. G., and Fendorf, S. (Invited Talk): “Influxes and Solid Phase Controls on Arsenic in Southeast Asian Groundwater,” ETH/EAWAG Joint Meeting on Arsenic in Munshiganj, Bangladesh, Zurich, Switzerland, 2007.

• S. Fendorf (Invited Talk): “Soil Processes Controlling Arsenic Concentrations in Aquifers of Asia,” Environmental Science Seminar Series, U.C. Riverside, 2008.

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• S. Fendorf (Invited Talk): “A Quest for Safe Drinking Water,” Troubled Water Seminar Series, Stanford University, 2008.

• B. D. Kocar, B. D. Stewart, M. J. Herbel, and S. Fendorf (Contributed Presentation): “Arsenic Mobilization Influenced By Iron Reduction And Sulfidogenesis Under Dynamic Flow,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2004.

• Polizzotto, M. L., Fendorf, S., and Harvey, C. (Contributed Presentation): “Redox Cycling and Arsenic Transport to Groundwater in Bangladesh,” EOS, Transactions American Geophysical Union, December 2004.

• Polizzotto, M. L., Harvey, C., and Fendorf, S. (Contributed Presentation): “Surface Redox Processes and Arsenic Transport to Aquifers in Bangladesh,” Soil Science Society of America Annual Meeting, November 2004.

• B. D. Kocar, T. Borch, and S. Fendorf (Contributed Presentation): “Release of Arsenic and Transformation of Iron (Hydr)oxides During Sulfidogenesis,” Soil Science Society of America Annual Meeting, Salt Lake City, UT, 2004.

• B. D. Kocar, T. Borch, and S. Fendorf (Contributed Presentation): “Sulfidogenesis Controls on Iron (hydr)Oxide Transformation and Release of Arsenic,” 230th Annual Meeting of the American Chemical Society, Washington, D.C., 2005.

• B. D. Kocar, K. T. Tufano, Y. Masue, B. D. Stewart, M. J. Herbel, and S. Fendorf (Contributed Presentation): “Reactions of Biogenic Ferrous Iron and Sulfide with Arsenic-Doped Ferrihydrite: Pathways of Arsenic Mobilization and Sequestration,” ISSM/ISEB Meeting, Jackson Hole, WY, 2005.

• B. D. Kocar, K. T. Tufano, Y. Masui, B. D. Stewart, M. J. Herbel, and S. Fendorf (Contributed Presentation): “Arsenic Mobilization Influenced By Iron Reduction and Sulfidogenesis,” 16th

Goldschmidt Conference, Moscow, ID, 2005.• K. T. Tufano, B. D. Stewart, B. D. Kocar, and S. Fendorf (Contributed Presentation):

“Deciphering the Role of Reductive Iron Transformations on Arsenic Transport,” Soil Science Society of America Conference, Salt Lake City, UT, 2005.

• K. T. Tufano, B. D. Stewart, B. D. Kocar, and S. Fendorf (Contributed Presentation): “Stimulated Migration of Arsenic by Reductive Transformation of Iron,” American Chemical Society National Meeting, Washington, DC, 2005.

• K. T. Tufano, B. D. Stewart, M. J. Herbel, and S. Fendorf (Contributed Presentation): Stimulated Migration of Arsenic and Uranium by Reductive Transformation of Iron. 16th

Goldschmidt Conference, Moscow, ID, 2005.• K. T. Tufano, B. D. Stewart, and S. Fendorf (Contributed Presentation): Stimulated Migration

of Arsenic by Reductive Transformation of Iron. Stanford Synchrotron Radiation Laboratory Users Meeting, Menlo Park, CA, 2005.

• Masue, Y., T. Borch, B. D. Kocar, and S. Fendorf (Contributed Presentation): “Arsenic Attenuation upon Bioreduction of Ferrihydrite,” Soil Science Society of America Annual Meeting. Salt Lake City, UT, 2005.

• Masue, Y., T. Borch, B. D. Kocar, and S. Fendorf (Contributed Presentation): “Arsenic Attenuation and Iron Cycling upon Bioreduction of Ferrihydrite,” Stanford Synchrotron Radiation Laboratory Users Meeting. Menlo Park, CA, 2005.

• Polizzotto, M. L., Kocar, B. D., Sampson, M., Ouch, K., Ung, M., Oum, R., Benner, S. G., and Fendorf, S. (Contributed Presentation): Arsenic Contamination in the Flood Plain Aquifer of the Mekong Delta, Cambodia,” Geological Society of America Annual Meeting, October 2005.

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• B. D. Kocar, S. C. Ying, M. L. Polizzotto, U. Mengieng, S. Samreth, L. Moniphea, M. Sampson, and S. Fendorf (Contributed Presentation): “Arsenic Retention and Release from Ferrihydrite and Tropical Soils During Iron and Sulfate Reduction,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2006.

• B. D. Kocar, S. C. Ying, M. L. Polizzotto, U. Mengieng, S. Samreth, L. Moniphea, M. Sampson, and S. Fendorf (Contributed Presentation): Iron (hydr)oxide Transformation and Release of Arsenic from Tropical Soils during Iron and Sulfate Reduction,” Soil Science Society of America Annual Meeting, Indianapolis, IN, 2006.

• B. D. Kocar, Y. Masue, K. T. Tufano, S. C. Ying, M. L. Polizzotto, T. Borch, and S. Fendorf (Contributed Presentation): “Iron (Hydr)oxide Transformation and Release of Arsenic from Ferrihyrite and Tropical Soils During Sulfate Reduction,” World Congress of Soil Science, Philadelphia, PA, 2006.

• Masue, Y., T. Borch, B. D. Kocar, and S. Fendorf (Contributed Presentation): “Arsenic Attenuation upon Bioreduction of Ferric (Hydr)oxides,” World Congress of Soil Science. Philadelphia, PA, 2006.

• Masue, Y., T. Borch, B. D. Kocar, and S. Fendorf (Contributed Presentation): “Arsenic Attenuation upon Bioreduction of Ferrihydrite,” General Meeting of the International Mineralogical Association, Kobe, Japan, 2006.

• K. T. Tufano and S. Fendorf (Contributed Presentation): “Biogeochemical Conditions Governing Arsenic Migration in Surface and Subsurface Environments” 16th Goldschmidt Conference, Melbourne, Australia, August 2006.

• K. T. Tufano and S. Fendorf (Contributed Presentation): “Unearthing the Role of Reductive Iron Transformations on Arsenic Transport,” World Soils Congress, Philadelphia, PA, 2006.

• K. T. Tufano, P. S. Nico, S. G. Benner, and S. Fendorf (Contributed Presentation): “Gradients in Iron Oxide Transformation Induced by Pore-scale Heterogeneity,” Stanford Synchrotron Radiation Laboratory Annual Users Meeting, Menlo Park, CA, 2006.

• M. L. Polizzotto, K. Ouch, B. D. Kocar, M. Sampson, S. G. Benner, and S. Fendorf (Contributed Presentation): „Arsenic Contamination of Groundwater in the Mekong River Delta, Cambodia,” EPA STAR Meeting, Washington, DC, 2006.

• Y. Masue-Slowey, K. T. Tufano, R. Loeppert, and S. Fendorf (Contributed Presentation): “Alteration in Arsenic Retention Upon Reductive Transformation of Alumino-Ferrihydrite,” Soil Science Society of America Annual Meeting, New Orleans, LA, 2007.

• Y. Masue-Slowey, S. M. Webb, and S. Fendorf (Contributed Presentation): “Solubility and Structure of Ferrous Arsenite Precipitate: Implications for Arsenic Geochemical Cycling in Anaerobic Environments,” Stanford Synchrotron Radiation Laboratory Annual Users Meeting, Stanford, CA, 2007.

• M. L. Polizzotto, Benner, S. G., Kocar, B. D., Sampson, M., Ouch, K., Phan, K., and Fendorf, S. (Contributed Presentation): „Evaluating Sources of Arsenic to Groundwater in the Mekong Delta Based on Coupled Hydrologic and Biogeochemical Analyses,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2007.

• M. L. Polizzotto, Benner, S. G., Kocar, B. D., Sampson, M., Ouch, K., Fendorf, S. (Contributed Presentation): “Contributions of Natural Arsenic Cycling and HumanDdisturbance to History's Largest Mass Poisoning,” Stanford Environmental Molecular Sciences Institute Annual Meeting, Stanford, CA, August 2007.

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• B. D. Stewart and S. Fendorf (Contributed Presentation): “Geochemical Conditions Convoluting the Fate of Uranium in Surface and Subsurface Environments,” Stanford Environmental Molecular Sciences Institute Annual Meeting, Stanford, CA, August 2007.

• B. D. Stewart, J. Neiss, and S. Fendorf (Contributed Presentation): “Constraints on Microbial Reduction of Uranium within Soils and Sediments,” DOE Environmental Remediation Sciences Program Annual PI Meeting. Lansdowne, VA, 2007.

• B. D. Stewart, P. S. Nico, R. T. Amos, and S. Fendorf (Contributed Presentation): “Quantitatively Describing and Predicting Electron Balance between Competitive Iron and Uranium Reduction.” American Chemical Society Spring National Meeting, Chicago, IL, 2007.

• K. T. Tufano and S. Fendorf (Contributed Presentation): “Confounding Impacts of Iron Reduction on Arsenic Retention,” Stanford Synchrotron Radiation Laboratory Users Meeting, Stanford, CA, 2007.

• K. T. Tufano and S. Fendorf (Contributed Presentation): “Controls on Arsenic Retention in Surface and Subsurface Environments: Resolving the Impact of Iron Reduction,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2007.

• Tufano, K. T. and S. Fendorf (Contributed Presentation): “Reductive Iron Transformations Can Promote and Inhibit Arsenic Mobility,” Soil Science Society of America Conference, New Orleans, LA, 2007.

S. C. Ying , B. D. Kocar, S. Fendorf, and C. A. Francis. (Contributed Presentation): “Diversity and As-Adsorption Properties of Mn(III)-Oxidizing Bacteria Within Tropical Wetlands of the Mekong Delta,” American Geophysical Union Annual Fall Meeting, San Francisco, CA, December 2007.

S. C. Ying , B. D. Kocar, S. Fendorf, and C. A. Francis (Contributed Presentation): “Arsenic Mobilization within Deltaic Soils of Asia: Diversity of Arsenic(V) Reductase (arrA) Genes across Redox Gradients,” American Society of Microbiology Annual Meeting, Toronto, Ont., Canada, 2007.

S. C. Ying , B. D. Kocar, M. Sampson, S. Fendorf, and C. A. Francis (Contributed Presentation): “Near Surface Pore Water and Surface Water Cycling of Arsenic and Manganese in the Mekong Delta, Cambodia,” Association of American Geographers Annual Meeting, San Francisco, CA, 2007.

Benner, S. G. , Polizzotto, M. L., Kocar B. D., Sampson, M., Fendorf, S. (Contributed Presentation): “Linking Hydrologic Drivers to Arsenic Contamination in Asia: Results from a Field Site in Cambodia,” American Geophysical Union Annual Fall Meeting, San Francisco, USA, 2008.

S. Fendorf, B. D. Kocar, K. T. Tufano, Y. Masue, M. L. Polizzotto, C. Pallud, and S. G. Benner (Invited Talk): “Defining Spatial and Temporal Variations in Biogeochemical Processes Governing Arsenic Mobility,” 18th Goldschmidt Conference, Vancouver, B.C., Canada, August 2008.

S. Fendorf (Invited Talk): “Case Study: Arsenic in Southeast Asia and California. Atoms to Ecosystems,” EMSI Workshop for Environmental Journalists, Stanford, CA., August 2008.

S. Fendorf (Invited Talk): “Metal Distribution and Biogeochemical Cycles of the Twenty-First Century,” Soil Science Society of America – Geological Society of America Joint National Meeting. Houston, TX, 2008.

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S. Fendorf (Invited Talk): “Culprit of the Largest Mass Poisoning in History: Soil Processes Controlling Arsenic Transport into Asian Groundwater,” Kansas State University Department of Agronomy Lecture, Manhattan, KS, 2008.

S. Fendorf (Invited Talk): “Process-level Heterogeneity Controlling the Fate of Arsenic,” American Chemical Society Summer Meeting, Philadelphia, PA, 2008.

• M. L. Polizzotto (Contributed Presentation): “Contributions of Natural Arsenic Cycling and Human Disturbance to History's Largest Mass Poisoning,” Woods Institute Young Environmental Scholars Meeting, Stanford, CA, 2008.

• B. D. Stewart , P. S. Nico, and S. Fendorf (Contributed Presentation): “Stability of Uranium Incorporated into Fe(hydr)oxide Structure upon Oxidation and Under Fluctuating Redox Conditions,” DOE Environmental Remediation Sciences Program Annual PI Meeting. Lansdowne, VA, 2008.

B. D. Kocar , Polizzotto, M. L., Ying, S. C., Benner, S. G., Sampson, M., and Fendorf, S. (Contributed Presentation): “Coupled Biogeochemical and Hydrologic Processes Governing Arsenic Mobility within Sediments of Southeast Asia,” American Geophysical Union Annual Fall Meeting, San Francisco, USA, December 2008.

B. D. Kocar , Ying, S. C., Polizzotto, M. L., Benner, S. G., Ung, M., Suy, B., Phan, K., Sampson, M., and Fendorf, S. (Contributed Presentation): “Coupled Biogeochemical and Hydrologic Processes Governing Arsenic Transport within Evolving Sedimentary Basins of Southeast Asia,” Soil Science Society of America Annual Meeting, Houston, TX, 2008.

B. D. Kocar , Ying, S. C., Polizzotto, M. L., Ung, M., Suy, B., Phan, K., Samreth, S., Sampson, M., Benner, S. G., and Fendorf, S. (Contributed Presentation): “Deriving and Simulating the Coupled Biogeochemical and Hydrologic Processes Governing Arsenic Transport within Evolving Sedimentary Basins of Southeast Asia,” 18th Goldschmidt Conference, Vancouver, BC, Canada, August 2008.

B. D. Stewart , P. S. Nico, and S. Fendorf (Contributed Presentation): ”Stability of Uranium Incorporated into Fe(hydr)oxide Structure Upon Oxidation and Under Fluctuating Redox Conditions,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2008.

B. D. Stewart , P. S. Nico, and S. Fendorf (Contributed Presentation): “Stability of Uranium Incorporated into Fe(hydr)oxide Structure Under Fluctuating Redox Conditions,” 18th

Goldschmidt Conference, Vancouver, B.C., Canada, August 2008. S. G. Benner , M. L. Polizzotto, B. D. Kocar, M. Sampson, and S. Fendorf (Invited Talk):

“Hydrologic Constraints on Arsenic Behavior: Observations from a Field Site in Cambodia,” AGU Chapman Conference on Arsenic in Groundwater of Southern Asia, Siem Reap, Cambodia, 2009.

S. Fendorf (Invited Talk): “Pathogens and Poisons,” Stanford Ethics Society Seminar Series, Stanford, CA, 2009.

S. Fendorf (Invited Talk): “A Water Crisis for a Billion People: Pathogen and Poison Infected Waters of Asia,” Stanford Synchrotron Radiation Lightsource Seminar Series. SLAC, CA, 2009.

B. D. Kocar , M. L. Polizzotto, S. C. Ying, S. G. Benner, M. Sampson, and S. Fendorf (Contributed Presentation): “Coupled Biogeochemical and Hydrologic Processes Governing Arsenic Mobility within Sediments of Southeast Asia,” American Geophysical Union Fall Meeting, San Francisco, CA, December 2009.

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B. D. Kocar , M. L. Polizzotto, S. C. Ying, S. G. Benner, M. Sampson, and S. Fendorf (Invited Talk): “Measuring and Simulating the Near-Surface Biogeochemical and Hydrologic Processes Governing Arsenic Transport in the Mekong Delta, Cambodia,” AGU Chapman Conference on Arsenic in Groundwater of Southern Asia, Siem Reap, Cambodia, 2009.

M. L. Polizzotto , B. D. Kocar, S. G. Benner, M. Sampson, K. Phan, K. Ouch, and S. Fendorf (Contributed Presentation): “Coupled Hydrologic and Biogeochemical Processes Controlling Arsenic in Cambodian Groundwater,” AGU Chapman Conference on Arsenic in Groundwater of Southern Asia, Siem Reap, Cambodia, 2009.

L. Seyfferth , and S. Fendorf (Contributed Presentation): “Silicate Mineral Impacts on Arsenic Accumulation in Rice (Oryza sativa L.),” 19th Goldschmidt Conference, Davos, Switzerland, June 2009.

C. Stanford EMSI-Related Presentations by the Nilsson Group (May 2006 - June 2008)

• X-ray Absorption Spectroscopy; Experimental Observations and Interpretations (Invited Talk)Stockholm Discussion meeting; Structure and Molecular Scale Properties of Liquid Water (June 2006)

• Ultrafast Surface Chemistry (Invited Talk)Workshop on Catalysis for the 4GLS facility, London, UK (June 2006)

• The Water MysteryJournalist Workshop at Stanford University (June 2006)

• X-ray Induced Excitation and Dynamics in Aqueous System (Invited Talk)Gordon Research Conference on Radiation Chemistry, Waterville, Maine (July 2006)

• Hydrogen Bonding Configurations in Water and Aqueous Systems (Invited Talk)Conference on Physics, Chemistry and Biology of Water, Vermont (October 2006)

• The Mystery of Water; Liquid Phase and on Surfaces (Invited Talk)Max Plank Society Winterschol, Ringberg Castle, Bavaria, Germany (February 2007)

• Ultrafast Surface Chemistry (Invited Talk)SLAC-DESY workshop on FEL science, Hamburg, Germany (June 2007)

• Hydrogen Bonding in Water; in the Liquid Phase and on Surfaces (Invited Talk)17th International Vacuum Congress, Stockholm, Sweden (July 2007)

• Microscopic Origin of Wetting of Metals by Water, 17th International Vacuum Congress (IVC-17), Stockholm, Sweden (July 2007)

• In-situ XPS for Environmental Science and Catalysis, 2007 SSRL/LCLS Users' Meeting: Joint SSRL/ALS Workshop "Introduction to Synchrotron Methods, 2007.

• Surface water chemistry on metals and oxides: Recent results and future AP-XPS design (Invited Talk) “Radiation Techniques", Menlo Park, USA (September 2007), Invited lecture

• Ambient Pressure Photoelectron Spectroscopy (Invited Talk)2007 ALS Users' Meeting Workshop, Berkeley, USA (October 2007)

• Challenges for the futureWorkshop on the Future of X-ray Science, Stanford (October 2007)

• Synchrotron Radiation; Unique Opportunities (Invited Talk)Mexican Society for Chrystallography, Guadalajara (October 2007)

• Energy and Environmental Science Research using Synchrotron RadiationWorkshop for MAXIV, Lund, Sweden (October 2007)

• Hydrogen Bonding in Water; in the Liquid Phase and on Surfaces (Invited Talk)

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International Workshop on Interfacial Water Structure and Dynamics, Shanghai, China (December 2007)

• New Experimental X-ray Studies of Bulk Water; Indications of Spatially Separated Two Structural Motifs, International Workshop on Aqueous Solutions and their Interfaces, Heraklion, Greece (June 2008)

D. Stanford EMSI-Related Presentations by Dennis Nordlund (May 06 - April 07)

• Photoelectron Spectroscopy of Liquid Water Stockholm Discussion meeting; Structure and Molecular Scale Properties of Liquid Water (June 2006), Invited talk

• The Isotope Effect in Liquid Water probed by X-ray Raman Spectroscopy2nd Annual Stanford EMSI meeting, Stanford, USA (August 2006), Presentation

• Ultrafast Electron Delocalization in Liquid Water33rd Annual SSRL Users Meeting, Stanford, USA (October 2006), Invited Talk

• Ultrafast Spectroscopy of Liquid Water at SSRLPulse Seminar, SSRL, Menlo Park, Ca, USA (February 2006), Presentation

• X-ray and Electron Spectroscopy of WaterCanadian Association of Physicists annual congress, Saskatoon, Canada (June 2007)

E. Stanford EMSI-Related Presentations by Susumu Yamamoto (May 06 - April 07)

• Water adsorption on a-Fe2O3(0001) at near-ambient conditions (Poster Presentation)4th Annual University of California Symposium on Surface Science and Its Applications, Berkeley (February 2006)

• Water chemistry on metal surfaces at near ambient conditions studied by photoelectron spectroscopy: Comparison between Cu(110) and Cu(111) surfaces (Poster Presentation)231st American Chemical Society National Meeting, Atlanta (March 2006)

• Water adsorption on hematite (0001) and rutile (110) at near-ambient conditions (Oral Presentation), 231st American Chemical Society National Meeting, Atlanta (March 2006)

• Water adsorption on a-Fe2O3(0001) and TiO2(110) at near-ambient conditions (Oral Presentation) 232nd American Chemical Society National Meeting, San Francisco (September 2006)

• Different Wetting Behavior on Cu (110) and (111) at Ambient Conditions: In-situ Photoemission Spectroscopy Study (Oral Presentation), The tenth ISSP International Symposium (ISSP-10) on Nanoscience at Surfaces, Kashiwa, Japan (October 2006)

• Microscopic Wetting of Water on Metals at Near Ambient Conditions (Poster Presentation)Advanced Light Source users' meeting, Berkeley (October 2006)

• Water Adsorption from Submonolayer to Multilayer Coverage on TiO2(110) and Fe2O3(0001) by In-situ Spectroscopy (Oral Presentation), American Vacuum Society 53rd International Symposium, San Francisco (November 2006)

F. Stanford EMSI-Related Presentations by Klas Andersson (May 06 - April 07)

• Structure and properties of mixed H2O:OH stripes on Ru(001) (Oral Presentation)24th European Conference on Surface Science, Paris, France (September 2006)

G. Stanford EMSI-Related Presentations by Hendrik Bluhm (January 2006 – June 2009)88

• H. Bluhm, S. Yamamoto, J. T. Newberg, T. Kendelewicz, D. E. Starr, S. Kaya, K. Andersson, H. Ogasawara, G.E. Brown, Jr., M. Salmeron, A. Nilsson (Invited Talk): “Water Adsorption on Oxide and Metal Surfaces: From UHV to Ambient Conditions,” 25th European Conference on Surface Science (ECOSS), July 27 – August 2, Liverpool, UK, (2008). • H. Bluhm (Invited Talk): “Aqueous solution and ice/vapor interfaces studied with ambient pressure photoemission spectroscopy,” Seminar, Chemistry Department, Lehigh University, May 14, Bethlehem, PA (2008).• H. Bluhm (Invited Talk): “Investigation of liquid/vapor and ice/vapor interfaces using ambient pressure photoemission spectroscopy,” International Workshop on Molecular Structure and Dynamics of Interfacial Water, December 14-18, Shanghai, China (2007). • H. Bluhm (Invited Talk): “Investigation of liquid/vapor and ice/vapor interfaces using ambient pressure photoemission spectroscopy,” Surface Science Seminar, Materials Sciences Division, Lawrence Berkeley National Laboratory, November 1, Berkeley, CA (2007).• H. Bluhm (Invited Talk): “Liquid/vapor and solid/vapor interfaces studied using ambient pressure photoemission spectroscopy,” Advanced Light Source Seminar, April 11, Berkeley, CA (2007). • D. E. Starr, Ch. D. Weiss, S. Yamamoto, A. Nilsson, M. Salmeron, and H. Bluhm (Invited Talk): “The interaction of H2O and NO2 with thin MgO(100) films grown on Ag(100) as studied with ambient pressure photoemission spectroscopy,” 233 American Chemical Society National Meeting, March 25-29, Chicago, IL (2007).• H. Bluhm (Invited Talk): “Ambient pressure photoemission for atmospheric and environmental science,” Seminar, School of Earth Sciences, Stanford University, January 26, Stanford, CA (2007). • D. E. Starr, Ch. D. Weiss, S. Yamamoto, A. Nilsson, M. Salmeron, and H. Bluhm (Invited Talk): “The interaction of H2O and NO2 with thin MgO(100) films grown on Ag(100) as studied with ambient pressure photoemission spectroscopy,” 233rd American Chemical Society National Meeting, March 25-29, 2007, Chicago, IL. • J. T. Newberg, D. E. Starr, S. Yamamoto, S. Kaya, K. Andersson, T. Kendelewicz, G. Ketteler, G. E. Brown, Jr., A. Nilsson, M. Salmeron, and H. Bluhm (Poster): “The interaction of water with periclase and hematite surfaces,” 3rd Annual ERSP PI Meeting, Lansdowne, VA, April 7-10, 2008.• J. T . Newberg, D. E. Starr, S. Kaya, S. Yamamoto, A. Nilsson, and H. Bluhm (Contributed Talk): “Water uptake on thin film MgO using ambient pressure XPS,” American Physical Society March Meeting, March 10-14, New Orleans, LA (2008).• D. E. Starr, Ch. D. Weis, S. Yamamoto, A. Nilsson, M. Salmeron, and H. Bluhm (Contributed Talk): “The Interaction of NO2 with MgO(100) Studied with Photoemission Spectroscopy,” American Vacuum Society 54th International Symposium, October 14 - 19, Seattle, WA (2007).• D. E. Starr, Ch. D. Weis, S. Yamamoto, A. Nilsson, M. Salmeron, and H. Bluhm (Contributed Talk): “Thickness Dependence of the Interaction of NO2 with Thin MgO(100) Films Grown on Ag(100) as Studied by Photoemission Spectroscopy,” American Vacuum Society 54th

International Symposium, October 14 - 19, Seattle, WA (2007).• D. E. Starr, E. Mysak, K. R. Wilson, and H. Bluhm (Invited Talk): “Aerosol interfaces examined using ambient pressure photoemission spectroscopy,” Gordon Research Conference on Atmospheric Chemistry, August 26 - 31, Big Sky, MT (2007).

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• D. E. Starr, M. Ammann, K.R. Wilson, and H. Bluhm (Contributed Talk)” “Aqueous solution and ice/vapor interfaces studied with ambient pressure photoemission spectroscopy,” VUV XV – The 15th International Conference on Vacuum Ultraviolet Radiation Physics, July 29 – August 3, Berlin, Germany (2007). • D. E. Starr, Ch. D. Weiss, S. Yamamoto, A. Nilsson, M. Salmeron, and H. Bluhm (Contributed Talk): “The interaction of H2O and NO2 with thin MgO(100) films grown on Ag(100) as studied with ambient pressure photoemission spectroscopy,” VUV XV – The 15th

International Conference on Vacuum Ultraviolet Radiation Physics, July 29 – August 3, Berlin, Germany (2007). • D. E. Starr, K. R. Wilson, and H. Bluhm (Poster): “A combined droplet train / photoemission spectroscopy experiment for the investigation of heterogeneous reactions on liquid surfaces,” Gordon Research Conference on Chemical Reactions on Surfaces, February 11 - 16, Ventura, CA (2007).• D. E. Starr, Ch. D. Weiss, S. Yamamoto, A. Nilsson, M. Salmeron, and H. Bluhm (Invited Talk): “The interaction of H2O and NO2 with thin MgO(100) films grown on Ag(100) as studied with ambient pressure photoemission spectroscopy,” 5th International Workshop on Oxide Surfaces (IWOX V), January 7-12, 2007, Tahoe City, CA.• S. Yamamoto, K. Andersson, H. Bluhm, G. Ketteler, D. E. Starr, Th. Schiros, S. Wang, M. Salmeron, H. Ogasawara, and A. Nilsson (Contributed Talk): “Wetting on metal surfaces at ambient conditions: a photoemission spectroscopy study,” American Vacuum Society 53rd

International Symposium, San Francisco, CA, November 12 - 17, 2006.• G. Ketteler, S. Yamamoto, H. Bluhm, T. Kendelewicz, K. Andersson, D. E. Starr, G. E. Brown, Jr., A. Nilsson, and M. Salmeron (Contributed Talk): “Water adsorption from submonolayer to multilayer coverage on TiO2(110) and Fe2O3(0001) by in situ spectroscopy,” American Vacuum Society 53rd International Symposium, San Francisco, CA, November 12 - 17, 2006.• D. E. Starr, G. Ketteler, S. Yamamoto, T. Kendelewicz, G. E. Brown, Jr., A. Nilsson, M. Salmeron, and H. Bluhm (Contributed Talk): “The interaction of H2O with MgO(100) as studied with ambient pressure photoemission spectroscopy,” American Vacuum Society 53rd

International Symposium, San Francisco, CA, November 12 - 17, 2006.• M. Salmeron, A. Verdaguer, G. Ketteler, Ch. Weiss, H. Bluhm, and D. E. Starr (Invited Talk): “Growth and structure of water on amorphous SiO2 investigated by Kelvin probe microscopy and in situ X-ray photoelectron spectroscopy,” American Vacuum Society 53rd International Symposium, San Francisco, CA, November 12 - 17, 2006.• H. Bluhm (Invited Talk): “Ambient pressure photoemission for atmospheric and environmental science,” Seminar, Chemistry Department, UC Irvine, Irvine, CA, November 1, 2006.• H. Bluhm (Invited Talk): “Ambient pressure photoemission spectroscopy for environmental science and catalysis,” Advanced Light Source User’s Meeting, Lawrence Berkeley National Laboratory, Berkeley, CA, October 9-11, 2006.• S. Yamamoto, K. Andersson, H. Bluhm, G. Ketteler, D. E. Starr, Th. Schiros, S. Wang, M. Salmeron, H. Ogasawara, and A. Nilsson (Invited Talk): “Different wetting behaviour on Cu(110) and (111) at ambient conditions: in situ photoemission spectroscopy study,” 10th

International Symposium on Nanoscience at Surfaces (ISSP-10), Kashiba, Chiwa, Japan, October 9-13, 2006.

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• S. Yamamoto, G. Ketteler, T. Kendelewicz, H. Bluhm, D. E. Starr, K. Andersson, H. Ogasawara, M. Salmeron, G. E. Brown Jr., and A. Nilsson (Invited Talk): “Water adsorption on a-Fe2O3 (0001) and TiO2 (110) at ambient conditions,” 10th International Symposium on Nanoscience at Surfaces (ISSP-10), Kashiba, Chiwa, Japan, October 9-13, 2006.• S. Yamamoto, G. Ketteler, T. Kendelewicz, H. Bluhm, K. Andersson, H. Ogasawara, D. E. Starr, G. E. Brown, Jr., M. Salmeron, and A. Nilsson (Contributed Talk): “Water adsorption from submonolayer to multilayer coverage on TiO2(110) and Fe2O3(0001) by in situ spectroscopy,” 232nd American Chemical Society National Meeting, San Francisco, CA, September 10-14, 2006.• D. E. Starr, G. Ketteler, S. Yamamoto, T. Kendelewicz, G. E. Brown, Jr., A. Nilsson, M. Salmeron, and H. Bluhm (Contributed Talk): “Interaction of H2O with MgO(100) as studied with ambient pressure photoemission spectroscopy,” 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006.• G. Ketteler, S. Yamamoto, K. Andersson, H. Bluhm, D. E. Starr, D. F. Ogletree, H. Ogasawara, A. Nilsson, and M. Salmeron (Contributed Talk): “Water adsorption from submonolayer to multilayer coverge on TiO2(110) by in situ photoelectron spectroscopy,” 24th

European Conference on Surface Science, Paris, France, September 4-8, 2006.• D. E. Starr, G. Ketteler, S. Yamamoto, T. Kendelewicz, G. E. Brown, Jr., A. Nilsson, M. Salmeron, and H. Bluhm (Contributed Talk): “Interaction of H2O with MgO(100) as studied with ambient pressure photoemission spectroscopy,” 24th European Conference on Surface Science, Paris, France, September 4-8, 2006.• T. Kendelewicz, S. Yamamoto, H. Bluhm, G. Ketteler, K. Andersson, D. E. Starr, M. Salmeron, A. Nilsson, and G. E. Brown, Jr. (Contributed Talk): “Reaction of molecular water with (0001)surfaces of hematite (Fe2O3): a high pressure XPS study,” 24th European Conference on Surface Science, Paris, France, September 4-8, 2006.• H. Bluhm (Invited Talk): “Ambient pressure photoemission spectroscopy at the ALS MES beamline,” 2nd Annual Stanford EMSI Meeting, Stanford, CA, August 7-8, 2006.• K. Andersson, S. Yamamoto, G. Ketteler, D. E. Starr, A. Nilsson, M. Salmeron, and H. Bluhm (Poster): “The interaction of water with environmentally relevant surfaces,” Annual ERSD PI Meeting, Warrenton, VA, April 3-5, 2006.

H. Stanford EMSI-Related Presentations by Satish Myneni (2006-2009)

• Workshop on STXM and X-ray Nanoprobe Capabilities and Needs in the Environmental, Geological, and Biomedical Sciences, Stanford Linear Accelerator Center, Stanford, CA, July 9, 2007.

• User’s Conference, Stanford Linear Accelerator Center, Stanford, CA, October, 2007.• NSLSII Workshop on Earth & Environmental Sciences, January 22, 2008.• Warren Lecture, Department of Civil Engineering, University of Minnesota, Jan. 25, 2008.• American Chemical Society National Meetings, New Orleans, April 7, 2008.• Canadian Light Source, Workshop on Synchrotron Applications in Earth and Environmental

Sciences, May 5, 2008.• World Congress of Soil Science, Philadelphia (Keynote)• Frontiers in Geochemistry. American Chemical Society National Meetings, San Francisco

(Keynote) & two other presentations at the same conference by our group members

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• Workshop on Spectromicroscopy, Advanced Photon Source, Argonne National Laboratory, Chicago (Invited)

• National Synchrotron Light Source, Brookhaven National Laboratory (Invited)• National Synchrotron Light Source Users Conference, Brookhaven National Laboratory

(Invited)• Department of Civil Engineering and Geological Sciences, University of Notre Dame (Invited)

I. Stanford EMSI-Related Presentations by Rosso Group (2007-2009)

• Wigginton, N. S., K. M. Rosso, L. Shi, B. H. Lower, and M. F. Hochella, Jr., (Invited Talk):  "Insights into enzymatic reduction of metal-oxides from single-molecule tunneling studies of multiheme cytochromes." Goldschmidt 2007 Conference, Cologne, Germany, August 20, 2007.

• Rosso, K. M. (Invited Talk):  "Dynamics of Electron Transfer at Environmental Interfaces."  Washington University Earth and Planetary Sciences Speaker, St. Louis, MO, February 28, 2008. 

• Rosso, K. M., S. N. Kerisit, M. Valiev, D. M. Smith, N. A. Deskins, S. Yanina, N. S. Wigginton, T. P. Straatsma, and M. Dupuis (Contributed Talk): "Computational Bioelectrochemistry for Cytochrome-Electrode Interfaces."  234nd ACS National Meeting, Boston, MA.

• Rosso K. M., S. Yanina, S. N. Kerisit, J. G. Catalano, and P. Fenter (Invited Talk): "Electron Transfer at Oxide-Water Interfaces," GSA Denver Annual Meeting, Denver, CO, October 2007. 

• Rosso, K. M., S. N. Kerisit, M. Dupuis, X. Wang, and M. Valiev (Invited Talk):  "Fundamental Aspects of Electron Transfer at the Metal Oxide/Microbe Interface," Washington State University Chemistry Department Seminar Series, Pullman, WA, April 10, 2006. 

• Rosso, K. M., F. N. Skomurski, M. C. Wander, N. S. Wigginton, S. N. Kerisit, and S. Yanina.  (Invited Talk): "Advances in Mechanistic Understanding of Abiotic and Microbial Electron Transfer Kinetics."  2nd Annual ERSP PI Meeting, Landsdowne, VA, April 17, 2007. 

• Skomurski, F. N.   (Invited Talk): "From Atomic Bombs to Atomic Orbitals: Applications of Mineralogy to Nuclear Waste Management," Eastern Washington University Geology Department Invited Lecture, Cheney, WA, November 15, 2007. 

Skomurski, F. N. , Kerisit, S. N., and Rosso, K. M. (Contributed Talk): “Electron-transfer rates in magnetite surfaces: Implications for uranium reduction.” 18th Goldschmidt Conference, Vancouver, British Columbia, Canada, July 13-18, 2008.

Skomurski, F. N. , Kerisit, S. N., Ilton, E. S., and Rosso, K. M. (Invited Talk): “U6+ interactions with Fe2+ in magnetite.” American Chemical Society Spring Meeting, Salt Lake City, UT, March 22-26, 2009.

J. Stanford EMSI-Related Presentations by Spormann Group (2006-2009)

• Spormann, Alfred M., Kai Thormann, and Soni Shukla (Invited Talk): “Role of Biofilms in Microbe-Mineral Interation in Shewanella oneidensis MR-1”, Department of Biology, Auckland University, Auckland NZ, February, 2006.

• Spormann, Alfred M., Kai Thormann, and Soni Shukla (Invited Talk): “Role of Biofilms in

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Microbe-Mineral Interaction in Shewanella oneidensis MR-1”, Department of Chemical Engineering, Stanford University, Stanford, CA, October, 2006.

• Spormann, Alfred M. (Invited Talk): “Stability and Physiological Diversification in Biofilm Populations”, Amercian Society for Microbiology, Toronto, Canada, May 2007.

• Spormann, Alfred M., Kai Thormann, and Soni Shukla (Invited Talk): “Role of Biofilms in Microbe-Mineral Interaction in Shewanella oneidensis MR-1”, Department of Biology, Yale University, Stanford, CA, October, 2007.

• Spormann, Alfred M., Johannes Gescher, and Carmen Cordova (Invited Talk): “Essential Components of the Shewanella oneidensis MR-1 Extracellular Electron Transport Chain” PNNL, Grand Challenge in Biogeochemistry, 2007.

• Spormann, Alfred M. (Invited Talk): Role of Biofilms in Microbe-Mineral Interaction in Shewanella oneidensis MR-1”, Swiss Society for Microbiology, Interlaken, Switzerland, June 2007.

• Spormann, Alfred M. (Invited Talk): “Stability and Physiological Diversification in Biofilm Populations”, Bellagio Meeting on Evolution of Microbial Complexity and Heterogeneity, Bellagio, Italy, October 2008.

K. Stanford EMSI-Related Presentations by Trainor Group (2006-2009)

• S. K. Ghose, G. A. Waychunas, P. J. Eng, T. P. Trainor, and J. G. Catalano (Contributed Talk): “Surface Structure and Reactivity of Hydrated Goethite (a-FeOOH) (100) Surface,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept. 10-14, 2006.

• C. S. Lo, K. S. Tanwar, S. K. Ghose, A. M. Chaka, and T.P. Trainor (Contributed Talk): “Structure and Reactivity of Pb(II) on Hydrated Hematite and Goethite Studied via Density Functional Theory,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept. 10-14, 2006.

• S. C. Petitto, K. S. Tanwar, S. K. Ghose, P. J. Eng, M. F. Toney, and T. P. Trainor (Poster): “Surface Structure and Reactivity of Hydrated Magnetite (111) Under Environmentally Relevant Conditions,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept. 10-14, 2006.

• K. S. Tanwar, C. S. Lo, P. J. Eng, S. K. Ghose, S. C. Petitto, and T. P. Trainor (Poster): “An Assessment of Surface Structure and Reactivity Modification Induced by Fe(II) Sorption on a-Fe2O3 (1-102),” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept. 10-14, 2006.

• T. P. Trainor (Invited Keynote Address): “X-ray Scattering and Spectroscopic Studies of the Mineral-Water Interface,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept. 10-14, 2006.

• T. P. Trainor, P. J. Eng, A. M. Chaka, G. E. Brown Jr., K. S. Tanwar, S. C. Petitto, C. S. Lo, S. K. Ghose, and G. A. Waychunas (Contributed Talk): “Structure of the Iron-oxide Aqueous Solution Interface via Coupled Surface X-ray Diffraction and Density Functional Theory,” Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept. 10-14, 2006.

• T. P. Trainor, P. J. Eng, A. M. Chaka, C. S. Lo, K. S. Tanwar, S. K. Ghose, and S. C. Petitto (Contributed Talk): “Structure of the Iron-Oxide Aqueous Solution Interface: Surface X-ray Diffraction and Density Functional Theory Studies,” 16th Annual Goldschmidt Conference, Melbourne, Australia, Aug. 27-Sept. 1, 2006.

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• S. C. Petitto, K. S. Tanwar, S. K. Ghose, P. J. Eng, M. F. Toney, and T. P. Trainor (Contributed Talk): “Surface Structure of the Hydrated Fe3O4 (111) Surface Under Environmentally Relevant Conditions,” 5th International Workshop on Oxide Surfaces (IWOX V), Lake Tahoe, CA, January 7-12, 2007.

• T. P. Trainor (Invited Keynote Address): “X-ray Scattering and Spectroscopic Studies of the Mineral-Water Interface,” Materials Research Society National Meeting, Boston, MA, Nov. 26-28, 2007.

• T. P. Trainor (Invited Talk): “X-ray Scattering and Spectroscopic Studies of the Mineral-Water Interface,” Geological Society of America National Meeting, Denver, CO, Oct. 28-30, 2007

• T. P. Trainor, S.H. Mueller, V. Ritchie, and M. Newville (Invited Keynote Address): “Antimony Mobility Associated with the Oxidation of Stibnite-bearing Waste Rock from the Eastern Tintina Gold Province, Alaska and Yukon,” Frontiers in Mineral Sciences 2007, Cambridge University, U.K., June 26-28, 2007.

• T. Douglas, M. E. Walsh, T. P. Trainor, A. Jones, C. J. McGrath, and C. Weiss (Poster): “Breakdown of Nitramine (RDX, HMX) and Nitroaromatic (TNT) Explosives on Soil Surfaces,” Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April 6-18, 2008.

• S. K. Ghose, G. A. Waychunas, P. J. Eng, and T. P. Trainor (Contributed Talk): “Structure and Reactivity of Hydrated Goethite (100) Interface and Arsenic Sorption: CTR and RAXR Study,” 18th Annual Goldschmidt Conference, Vancouver, Canada, July 13-18, 2008.

• A. Ilgen, S. Mueller, M. Newville, and T. P. Trainor (Contributed Talk): “Arsenic and Antimony Speciation in Water and Bottom Sediments Associated with Geothermal Waste Fluids: Dachny Geothermal Field, Kamchatka, Russia,” Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April 6-18, 2008.

• A. Ilgen, M. Newville, and T. P. Trainor (Contributed Poster): “Arsenic and Antimony Interactions with Kaolinite, Montmorillonite and Nontronite Clays,” Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April 6-18, 2008.

• S. C. Mason, K. S. Tanwar, T. P. Trainor, and A. M. Chaka (Contributed Talk): “Pb(II) Sorption on Hydrated Oxide Surfaces,” Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April 6-18, 2008.

• S. C. Petitto, K. S. Tanwar, S. K. Ghose, P. J. Eng, and T. P. Trainor (Poster): “Surface Structure and Composition of Oxidized and Reduced Hydrated Magnetite (111),” Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April 6-18, 2008.

• K. S. Tanwar, S. C. Petitto, S. K. Ghose, P. J. Eng, and T. P. Trainor (Contributed Talk): “Structural Investigation of Fe(II) Adsorption on a-Fe2O3 (1-102) and (0001) Using Crystal Truncation Rod Diffraction,” Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April 6-18, 2008.

• T. P. Trainor (Invited Talk): “Surface X-ray Diffraction and Spectroscopy: Structural Analysis of Geochemical Interfaces,” Canadian Light Source Earth and Environmental Science Theme Workshop. Saskatoon, Saskatchewan, CA, May 5-6, 2008.

• T. P. Trainor (Invited Talk): “Structural Analysis of Geochemical Interfaces,” Advanced Photon Source Scientific Advisory Committee Cross-cut Review of Geological, Environmental and Planetary Science. Argonne, IL, July 9-10, 2008.

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• T. P. Trainor (Invited Talk): “X-ray Scattering and Spectroscopic Studies of the Mineral-Water Interface,” Workshop on X-ray Absorption Spectroscopy and Advanced Techniques, 2008, Paul Scherer Institute, Laussane, Switzerland, October 7-8, 2008.

• G. A. Waychunas, P. J. Eng, S. K. Ghose, Y. R. Shen, D. Spagnoli, T. P. Trainor, and L. Zhang (Contributed Talk): “Ordering of Water Near Mineral Interfaces: Recent Observations, Simulations and Consequences,” Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April 6-18, 2008.

• A. M. Chaka, C. R. Iceman, S. C. Mason, and T. P. Trainor (Contributed Talk): “Interactions of Water with Hematite and Alumina Surfaces,” Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, UT, March 22-26, 2009.

• C. R. Iceman, K. S. Tanwar, S. C. Mason, A. M. Chaka, and T. P. Trainor (Contributed Talk): “Solvated Ion and Explicit Water Contributions to the Energy of the 1-102 Hematite Surface,” Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, UT, March 22-26, 2009.

• A. Ilgen, M. Newville, and T. P. Trainor (Contributed Talk): “Role of Dissolved Iron(II) and Structural Iron in Clay Mineral Mediated Redox Transformations of Arsenic and Antimony,” Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, UT, March 22-26, 2009.

• S. C. Mason, C. R. Iceman, T. P. Trainor, and A. M. Chaka (Contributed Talk): “Reactivity Relationships in Hydrated Oxides Extracted from DFT Studies,” Abstracts of Papers, 237th

ACS National Meeting, Salt Lake City, UT, March 22-26, 2009.• S. C. Petitto, R. J. Rowland, K. S. Tanwar, S. K. Ghose, P. J. Eng, and T. P. Trainor

(Contributed Talk): “Surface Structure and Composition of Oxidized and Reduced Hydrated Magnetite (111),” Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, UT, March 22-26, 2009.

• T. P. Trainor, C. R. Iceman, K. S. Tanwar, S. C. Petitto, P. J. Eng, S. C. Mason, A.M. Chaka (Invited Talk): “Structure and Modification of Iron-Oxide Surfaces During Reaction With Dissolved Iron,” Goldschmidt 2009 Conference, Davos, Switzerland, June 21-26, 2009.

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APPENDIX C: PARTICIPANTS IN STANFORD EMSI (2008-2009)

Stanford EMSI Management TeamGordon E. Brown, Jr. Principal Investigator; Depts. of Geological & Environmental Sciences,

Photon Science, and Chemical Engineering, Stanford University, and SSRL; gordon.brown@stanford.edu

Anders Nilsson Co-Principal Investigator; Dept. of Photon Science, SLAC and Stanford Synchrotron Radiation Lightsource, Stanford University; nilsson@slac.stanford.edu

Jennifer Saltzman Director of Education and Outreach; School of Earth Sciences, Stanford University; saltzman@stanford.edu

Alfred M. Spormann Co-Principal Investigator; Depts. of Civil & Environmental Engineering and Chemical Engineering; spormann@stanford.edu

Stanford EMSI Senior InvestigatorsKarim Benzerara Institut de Minéralogie et de Physique des Milieux

Condensés, University of Paris VI-VII; karim.benzerara@impmc.jussieu.fr

Hendrik Bluhm Chemical Science Division, Lawrence Berkeley National Laboratory; HBluhm@lbl.gov

Bryan A. Brown Coordinator of Educational Outreach, School of Education, Stanford University, brbrown@stanford.edu

Georges Calas Institut de Minéralogie et de Physique des Milieux Condensés, University of Paris VI; georges.calas@impmc.jussieu.fr

Anne M. Chaka National Institute of Standards and Technology, Gaithersburg, MD; anne.chaka@nist.gov

Brent R. Constantz Calera Corporation, Los Gatos, CA, bconstantz@caleracorp.comFrancois Farges National Museum of Natural History, Paris; farges@mnhn.fr Scott E. Fendorf Dept. of Environmental Earth Systems Science, Stanford University;

fendorf@stanford.eduAndrea L. Foster U.S. Geological Survey; afoster@usgs.govFarid Juillot Institut de Minéralogie et de Physique des Milieux

Condensés, University of Paris VII; Farid.Juillot@impmc.jussieu.fr

Guillaume Morin Institut de Minéralogie et de Physique des Milieux Condensés, University of Paris VI; guillaume.morin@impmc.jussieu.fr

Satish C. B. Myneni Dept. of Geosciences, Princeton University; smyneni@princeton.eduGeorges Ona-Nguema Institut de Minéralogie et de Physique des Milieux

Condensés, University of Paris VI; Georges.Ona-nguema@impmc.jussieu.fr

Lars G. M. Pettersson Dept. of Physics, Stockholm University; lgm@physto.se Kevin M. Rosso Pacific Northwest National Laboratory; Kevin.Rosso@pnl.govJames J. Rytuba U.S. Geological Survey; jrytuba@mojave.wr.usgs.gov

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Miquel B. Salmeron Division of Materials Sciences, Lawrence Berkeley National Laboratory; mbsalmeron@lbl.gov

Mark P. Taylor Science & Technology Division, Corning Incorporated, Corning, NY Thomas P. Trainor Dept. of Chemistry & Biochemistry; University of Alaska, Fairbanks;

fftpt@uaf.eduJennifer Wilcox Dept. of Energy Resources Engineering, Stanford University;

wilcoxj@stanford.edu

Graduate and Undergraduate Students, Post-Docs, and Research AssociatesShela Aboud Dept. of Energy Resources Engineering, Stanford University;

shelaa@stanford.edu (Stanford research associate in Wilcox Group)Cristina Cismasu Dept. of Geological & Environmental Sciences, Stanford University;

cismasu@stanford.edu (Stanford graduate student in Brown Group)Carmen D. Cordova Dept. of Civil & Environmental Engineering, Stanford University;

treegirl@stanford.edu (Stanford graduate student in Spormann Group)Logan Daum Fairbanks High School student, Fairbanks, AK (high school intern in

Trainor Group)Dik Fandeur Dept. of Earth Sciences, University of Paris VII (U. Paris VII graduate

student and collaborator with Brown Group)Jose Figueroa Dept. of Chemistry, University of Puerto Rico (undergraduate intern in

Trainor Group, University of Alaska, Fairbanks)Juyoung Ha Dept. of Geological & Environmental Sciences, Stanford University;

jyha@stanford.edu (Stanford graduate student in Brown Group)Congcong Huang Stanford Synchrotron Radiation Laboratory, Stanford University;

congcong@stanford.edu (Stanford graduate student in Nilsson Group)Ningdong Huang Stanford Synchrotron Radiation Laboratory, Stanford University;

ndhuang@stanford.edu (Stanford graduate student in Nilsson Group)Christopher R. Iceman Dept. of Chemistry & Biochemistry, University of Alaska, Fairbanks;

fncri@uaf.edu (U. Alaska postdoctoral scholar in Trainor Group)Anastasia Ilgen Dept. of Chemistry & Biochemistry, University of Alaska, Fairbanks;

(U. Alaska, Fairbanks graduate student in Trainor Group)Adam D. Jew Dept. of Geological & Environmental Sciences, Stanford University;

adamjew@stanford.edu (Stanford graduate student in Brown Group)Sarp Kaya Stanford Synchrotron Radiation Lightsource, Stanford University;

sarpkaya@slac.stanford.edu (SSRL postdoctoral scholar in Nilsson Group)

Tom Kendelewicz Dept. of Geological & Environmental Sciences, Stanford University; kendelewicz@stanford.edu (Stanford senior research associate in Brown Group)

Guido Ketteler Materials Sciences Division, Lawrence Berkeley National Laboratory; guidoketteler@gmail.com (LBNL post-doctoral scholar in Salmeron Group)

Jeffrey King Dept. of Chemistry, Princeton University (Princeton undergraduate working in the Myneni Group)

Benjamin D. Kocar Dept. of Geological & Environmental Sciences, Stanford University; kocar@stanford.edu (Stanford postdoctoral scholar in Fendorf Group)

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Phi Luong Lowell High School, Cupertino, CA (High School Intern in Brown Group)

Sara C. Mason National Institute of Standards & Technology; sara.mason@nist.gov (NIST postdoctoral fellow in Chaka Group)

Yoko Masue-Slowey Dept. of Geological & Environmental Sciences, Stanford University; ymasue@stanford.edu (Stanford graduate student in Fendorf Group)

F. Marc Michel Dept. of Geological & Environmental Sciences, Stanford University; fmichel@stanford.edu (Stanford postdoctoral scholar in Brown Group)

Lauren Miller Dept. of Chemistry, Princeton University (Princeton undergraduate working in the Myneni Group)

Jennyfer Miot Institut de Minéralogie et de Physique des Milieux Condensés, University of Paris VI; miot@impmc.jussieu.fr (University of Paris VII graduate student – collaborator with Brown Group)

Bhoopesh Mishra Dept. of Geosciences, Princeton University (Princeton postdoctoral scholar in Myneni Group)

John T. Newberg Chemical Sciences Division, Lawrence Berkeley National Laboratory; JTNewberg@lbl.gov (LBNL postdoctoral scholar in Bluhm Group)

Celine Palud Dept. of Environmental Earth Systems Science (Stanford postdoctoral scholar in Fendorf Group)

Sarah C. Petitto Dept. of Chemistry & Biochemistry, University of Alaska, Fairbanks, AK; fnscp@uaf.edu (U. Alaska postdoctoral scholar in Trainor Group)

Matthew Polizzotto Dept. of Geological & Environmental Sciences, Stanford University; mattyp@stanford.edu (Stanford postdoctoral scholar in Fendorf Group)

Vanessa Ritchie Dept. of Chemistry & Biochemistry, University of Alaska, Fairbanks, AK (U. Alaska graduate student in Trainor Group)

Raena J. Rowland Dept. of Chemistry & Biochemistry, University of Alaska, Fairbanks, AK (U. Alaska graduate student in Trainor Group)

Soni Shukla Dept. of Civil & Environmental Engineering, Stanford University; sonis@stanford.edu (Stanford postdoctoral scholar in Spormann Group)

Hagar Siebner Dept. of Geological & Environmental Sciences, Stanford University; siebner@stanford.edu (Stanford postdoctoral scholar in Brown Group)

David M. Singer Dept. of Geological & Environmental Sciences, Stanford University; dmsinger@stanford.edu (Stanford graduate student in Brown Group)

Kunaljeet S. Tanwar Dept. of Chemistry, University of Alaska, Fairbanks (U. Alaska graduate student in Trainor Group+)

Kate T. Tufano Dept. of Geological & Environmental Sciences (Stanford graduate student in Fendorf Group)

Mary Van der Hoven Dept. of Geological & Environmental Sciences, Stanford University; mtvand2@stanford.edu (Stanford graduate student in Brown Group)

Ira Waluyo Stanford Synchrotron Radiation Laboratory; iwaluyo@stanford.edu (Stanford graduate student in Nilsson Group)

Yingge Wang Dept. of Geological & Environmental Sciences, Stanford University; ygwang@stanford.edu (Stanford graduate student in Brown Group)

Yuheng Wang Institut de Minéralogie et de Physique des Milieux Condensés, University of Paris VI;

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Yuheng.Wang@impmc.jussieu.fr (U. Paris VI graduate student – collaborator with Brown Group)

Susumu Yamamoto Stanford Synchrotron Radiation Lightsource; susumu@amolf.nl (SSRL postdoctoral scholar in Nilsson Group)

Samantha Ying Dept. of Geological & Environmental Sciences, Stanford University; samying@gmail.com (Stanford graduate student in Fendorf Group)

Jihae Yoon Dept. of Geological & Environmental Sciences, Stanford University; jhyoon1@pusan.ac.kr (Stanford postdoctoral scholar in Brown Group)

Tae-Hyun Yoon Dept. of Chemistry, Hanyang University, Sewoul, South Korea (Assistant Professor – former Ph.D. student and postdoctoral scholar in the Brown Group)

Yang Yu Dept. of Civil & Environmental Engineering, Stanford University; (Stanford graduate student in the Spormann Group)

Other Participants

John R. Bargar Stanford Synchrotron Radiation Lightsource; bargar@slac.stanford.edu (Stanford Synchrotron Radiation Lightsource Senior Scientific Staff Member – collaborator with the Brown Group)

Sean G. Benner Dept. of Geosciences, Boise State University, Boise, ID; sbenner@boisestate.edu (Assistant Professor and collaborator with the Fenbdorf Group)

Uwe Bergmann Stanford Synchrotron Radiation Lightsource; Bergmann@SLAC.stanford.edu (Stanford Synchrotron Radiation Lightsource Senior Scientific Staff Member and collaboratory with the Nilsson Group)

Yong Choi Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL; eng@cars.uchicago.edu (CARS Senior Research Associate and collaborator with the Brown Group)

Peter J. Eng Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL; eng@cars.uchicago.edu (CARS Senior Research Associate and collaboratory with the Brown Group)

Alexandre Gélabert University of Paris VII (Assistant Professor and former postdoctoral scholar in the Brown Group)

Sanjeet K. Ghose Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL; ghose@cars.uchicago.edu (CARS postdoctoral scholar and collaborator with the Brown and Trainor Groups)

Mae S. Gustin Dept. of Environmental and Resource Sciences, University of Nevada, Reno, Reno, NV (Professor and collaborator with the Brown Group)

Christopher S. Kim Dept. of Chemistry, Chapman University, Orange, CA (Assistant Professor and former Ph.D. student and current collaborator with the Brownb Group)

Anne Kotchevar Dept. of Chemistry, California State University, Hayward, Hayward, CA (Professor and collaborator with the Myneni Group)

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Ruben Kretzschmar Dept. of Environmental Sciences, ETH-Zurich, Zurich, Switzerland; ruben.kretzschmar@env.ethz.ch (visiting Professor and collaborator with the Brown and Fendorf Groups)

Matthew Marcus Advanced Light Source, Lawrence Berkeley National Laboratory (Beamline Scientist and collaborator with the Fendorf Group)

Gustavo Martinez Dept. of Agronomy and Soils, University of Puerto Rico (Professor and collaborator with the Myneni Group)

Nicolas Menguy Institut de Minéralogie et de Physique des Milieux Condensés, University of Paris VI; nicolas.menguy@impmc.jussieu.fr (Charges de Rescherche, CNRS – collaborator with Brown Group)

Wolfgang Moritz Dept. of Earth and Environmental Sciences, University of Munich, Munich, Germany (Professor Emeritus and collaborator with the Brown Group)

Peter Nico Earth Sciences Division, Lawrence Berkeley National Laboratory (Beamline Scientist and collaborator with the Fendorf Group)

Dennis Norlund Stanford Synchrotron Radiation Lightsource;( SSRL scientific staff and collaborator with the Nilsson Group)

Hirohito Ogasawara Stanford Synchrotron Radiation Laboratory, Stanford University; hirohito@slac.stanford.edu (SSRL scientific staff and collaborator with the Nilsson Group)

Rossitza Pentcheva Dept. of Earth and Environmental Sciences, University of Munich, Munich, Germany (Assistant Professor and collaborator with the Brown Group)

Joe Rogers Stanford Synchrotron Radiation Lightsource; jrogers@slac.stanford.edu (technical and engineering support staff member and collaborator with the Brown Group)

Aaron J. Slowey U.S. Geological Survey, Menlo Park, CA (Mendenhall Fellow and former Ph.D. student in Brown Group)

Michael F. Toney Stanford Synchrotron Radiation Lightsource; mftoney@slac.stanford.edu (Stanford Synchrotron Radiation Lightsource Senior Scientific Staff Member and collaborator with the Trainor Group)

Tolek Tyliszczak Advanced Light Source, Lawrence Berkeley National Laboratory (Beamline Scientist and collaborator with the Brown Group)

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APPENDIX D: Program with Abstracts of 4th Annual Meeting of the Stanford Environmental Molecular Science Institute

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4th Annual Meeting of the Stanford Environmental Molecular Science Institute

August 25-26, 2008

Hartley Conference Center–Mitchell Earth Sciences Building (Aug. 25)Room 111-Y2E2 Building (Aug. 26) Stanford University, Stanford, CA

Final Program2008 Stanford Environmental Molecular Science Institute

4th Annual MeetingStanford University, Stanford, CA – August 25-26, 2008

Monday, August 25, 2008 (Hartley Conference Center, Mitchell Earth Science Building)8:15-8:45 Continental breakfast

8:45-9:00 Gordon Brown (Stanford University and SLAC) – Introduction9:00-9:20 Anders Nilsson (SLAC) – Density fluctuations in water with a bimodal

distribution of local structures9:20-10:00 Lars Pettersson (Stockholm University) – Plenary Lecture – Water and

OH adsorption on metal surfaces and theoretical modeling of diffraction and OH stretch IR/Raman

10:00-10:20 Sarp Kaya (Stanford University) – Interaction of water with BaF2(111) at ambient conditions

10:20-10:40 John Newberg (LBNL) – Thin film water on MgO(100): A new perspective using APPES

10:40-11:00 Break

11:00-11:20 Sarah Petitto (University of Alaska, Fairbanks) – Surface structure and composition of oxidized and reduced hydrated magnetite (111)

11:20-11:40 Frances Skomurski (PNNL) – Reduction of U6+ by magnetite: Observed oxidation states and calculated rates of electron transfer

11:40-12:00 Christopher Iceman (University of Alaska, Fairbanks) – Computational surface studies of metal ion partitioning on hematite

12:00-12:20 Sara Mason (NIST) – Pb(II) adsorption on isostructural hydrated alumina and hematite (0001) surfaces: A DFT study

12:20-1:20 Lunch (sandwiches will be provided)

1:20-1:40 Marc Michel (Stanford University) – Structural aspects of synthetic ferrihydrite

1:40-2:00 Cristina Cismasu (Stanford University) – Molecular- and nm-scale investigation of the structure and compositional heterogeneity of naturally occurring ferrihydrite

2:00-2:20 Karim Benzerara (University of Paris VII) – Iron biomineralization by anaerobic neutrophillic iron-oxidizing bacteria

2:20-2:40 Satish Myneni (Princeton University) – Surface functional groups on bacterial cell surfaces: Composition and implications for metal and mineral surface binding

2:40-3:00 Juyoung Ha (Stanford University) – Study of proton, Pb2+, and Zn2+

adsorption onto Shewanella oneidensis MR-1 strain and mutant strain (ΔEPS): Spectroscopic observations and modeling approach

3:00-3:20 Break

3:20-3:40 Carmen Cordova (Stanford University) – CymA-independent respiratory plasticity in Shewanella oneidensis MR-1

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3:40-4:00 Yuri Gorby (Venter Institute) – Bacterial nanowires and long-range electron transfer

4:00-4:20 Samantha Ying (Stanford University) – Competitive redox and adsorption of arsenic between iron and manganese

4:20-4:40 Ben Kocar (Stanford University) – Defining and simulating the coupled biogeochemical and hydrologic processes governing arsenic mobility within soils and sediments of the Mekong Delta, Cambodia

4:40-5:10 Jennifer Saltzman (Stanford University) – Update on educational outreach in 2007-08

5:10-5:30 Tom Trainor (University of Alaska, Fairbanks) and Satish Myneni (Princeton University) – Discussion of EMSI Outreach Activities at the University of Alaska, Fairbanks and Princeton University

5:30-7:30 Poster Session (Beer, Soft Drinks, and Chips) First Floor, Green Building

7:30 - Dinner (on your own)

Monday Poster Session Presentations (First Floor – Green Earth Sciences Building) 1. Andrea Foster (U.S. Geological Survey) – Role of microbes in attenuation and

mobilization of arsenic at the Lava Cap Mine Superfund site, Nevada County, CA2. Congcong Huang (Stanford University) – Experimental evidence for the existence of

density heterogeneities on a nanometer scale in ambient water3. Ningdong Huang (Stanford University) – An indication of crossover in the dependence

of hydrophobic solvation on solute size by X-ray absorption spectroscopy4. Adam Jew (Stanford University) – EXAFS of frozen elemental mercury and its

implications for abandoned mercury mine wastes5. Tom Kendelewicz (Stanford University) – Dissociative and molecular adsorption of

water on the magnetite (111) surface studied with high pressure photoemission6. Mikael Leetmaa (Chalmers University, Sweden) – Diffraction and IR/Raman data do

not prove tetrahedral water7. Yoko Masue-Slowey (Stanford University) – Development of arsenic and iron

biogeochemical gradients upon anaerobiosis at the soil aggregate scale 8. Katrin Otte (University of Munich) - Stability, electronic and magnetic properties of

iron oxy-hydroxides under high pressure: Insights from first principles9. Rossitza Pentcheva (University of Munich) – Water adsorption on Fe3O4(001): Insights

from first principles10. Matthew Polizzotto (Stanford University)– Arsenic from near-surface sediments to

groundwater sustaining Asian mass poisoning11. Hagar Siebner (Stanford University) – Mercury accumulation and retention by plants at

the absndoned New Idria mine site: A preliminary XRF study12. David Singer (Stanford University) – Uranyl-chlorite sorption/desorption: Evaluation

of different sequestration mechanisms 13. Mary Van der Hoven (Stanford University) – Modeling the interaction of UO2

2+ with corundum and hematite surfaces

14. Ira Waluyo (SSRL) – X-ray absorption spectroscopy of alkali fluoride solutions15. Yingge Wang (Stanford University) – Parameters controlling the partitioning of trace

metal(loid)s at the Shewanella oneidensis MR-1 biofilm/mineral/water interface

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16. Susumu Yamamoto (SSRL) – Water adsorption on a-Fe2O3(0001) at near ambient conditions

17. Jihae Yoon (Stanford University) – Study of iodide adsorption on organobentonite using X-ray absorption spectroscopy and X-ray diffraction

Tuesday, August 26, 2008 (Room 111, Y2E2 Building)8:30-9:00 Continental breakfast

9:00-10:30 Gordon Brown, Scott Fendorf, Satish Myneni, and Tom Trainor (discussion leaders) – What have we learned over the past 10 years about metal oxide and metal sulfide surfaces and their interactions with aqueous solutions and microbial organisms?

10:30-10:45 Break

10:45-12:00 Anders Nilsson and Kevin Rosso (discussion leaders) What are some of the remaining first-order questions?

12:00-1:15 Lunch (sandwiches will be provided)

1:15-2:15 Karim Benzerara, Hendrik Bluhm, Anne Chaka, Miquel Salmeron, and Jennifer Wilcox (discussion leaders) – What advances in molecular-level surface techniques, molecular biology methods, and theory have been made during the past decade and what new information have they revealed about metal oxide and metal sulfide surfaces?

2:15-2:30 Gordon Brown and Anders Nilsson – Concluding remarks

2:30 Meeting adjourned

2:30-3:00 Closed meeting of Stanford EMSI Advisory Committee (George Helz (chair), Brent Constantz, Yuri Gorby, David Shuh)

3:00-3:45 Meeting of EMSI PI's with Members of the Stanford EMSI Advisory Committee

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2008 SEMSI Annual Meeting Participant ListSEMSI Advisory Committee Brent Constantz Calera Corporation, Los Gatos, CA; brent@calera.bizGeorge Helz, Chair Chemistry Department, University of Maryland; helz@umd.eduYuri Gorby J. Craig Venter Institute, San Diego, CA; ygorby@jcvi.orgDavid Shuh Chemical Sciences Division, LBNL; dkshuh@lbl.gov

SEMSI PI'sKarim Benzerara Institut de Minéralogie et de Physique des Milieux

Condensés, University of Paris VI-VII; karim.benzerara@impmc.jussieu.fr

Hendrik Bluhm Chemical Science Division, Lawrence Berkeley National Laboratory; HBluhm@lbl.gov

Gordon Brown Dept. of Geological & Environmental Sciences, Stanford University, and SSRL; gordon.brown@stanford.edu

Anne Chaka National Institute of Standards and Technology, Gaithersburg, MD; anne.chaka@nist.gov

Francois Farges National Museum of Natural History, Paris; farges@mnhn.fr Scott Fendorf Dept. of Environmental Earth Systems Science, Stanford University;

fendorf@stanford.eduAndrea Foster U.S. Geological Survey; afoster@usgs.govSatish Myneni Dept. of Geosciences, Princeton University; smyneni@princeton.eduAnders Nilsson Stanford Synchrotron Radiation Laboratory, Stanford University;

nilsson@slac.stanford.eduLars G. M. Pettersson Dept. of Physics, Stockholm University; lgm@physto.se Kevin Rosso Pacific Northwest National Laboratory; Kevin.Rosso@pnl.govJim Rytuba U.S. Geological Survey; jrytuba@mojave.wr.usgs.gov Jennifer Saltzman School of Earth Sciences, Stanford University; saltzman@stanford.eduAlfred Spormann Dept. of Civil & Environmental Engineering and Clark Center for

BioX; spormann@stanford.eduThomas Trainor Dept. of Chemistry & Biochemistry; University of Alaska, Fairbanks;

fftpt@uaf.eduJennifer Wilcox Dept. of Energy Resources Engineering, Stanford University;

wilcoxj@stanford.edu

Graduate and Undergraduate Students, Post-Docs, and Research AssociatesShela Aboud Dept. of Energy Resources Engineering, Stanford University;

shelaa@stanford.edu (Stanford research associate)Cristina Cismasu Dept. of Geological & Environmental Sciences, Stanford University;

cismasu@stanford.edu (Stanford graduate student)Carmen Cordova Dept. of Civil & Environmental Engineering, Stanford University;

treegirl@stanford.edu (Stanford graduate student)Juyoung Ha Dept. of Geological & Environmental Sciences, Stanford University;

jyha@stanford.edu (Stanford graduate student)Congcong Huang Stanford Synchrotron Radiation Laboratory, Stanford University;

congcong@stanford.edu (Stanford graduate student)

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Ningdong Huang Stanford Synchrotron Radiation Laboratory, Stanford University; ndhuang@stanford.edu (Stanford graduate student)

Christopher Iceman Dept. of Chemistry & Biochemistry, University of Alaska, Fairbanks; fncri@uaf.edu (U. Alaska postdoctoral scholar)

Adam Jew Dept. of Geological & Environmental Sciences, Stanford University; adamjew@stanford.edu (Stanford graduate student)

Sarp Kaya Stanford Synchrotron Radiation Laboratory, Stanford University; sarpkaya@slac.stanford.edu (SSRL postdoctoral scholar)

Tom Kendelewicz Dept. of Geological & Environmental Sciences, Stanford University; kendelewicz@stanford.edu (Stanford senior research associate)

Benjamin Kocar Dept. of Geological & Environmental Sciences, Stanford University; kocar@stanford.edu (Stanford graduate student)

Marc Michel Dept. of Geological & Environmental Sciences, Stanford University; fmichel@stanford.edu (Stanford postdoctoral scholar)

Sara Mason National Institute of Standards & Technology; sara.mason@nist.gov (NIST postdoctoral fellow)

Yoko Masue-Slowey Dept. of Geological & Environmental Sciences, Stanford University; ymasue@stanford.edu (Stanford graduate student)

John Newberg Chemical Sciences Division, Lawrence Berkeley National Laboratory; JTNewberg@lbl.gov (LBNL postdoctoral scholar)

Hirohito Ogasawara Stanford Synchrotron Radiation Laboratory, Stanford University; hirohito@slac.stanford.edu (SSRL scientific staff)

Sarah Petitto Dept. of Chemistry & Biochemistry, University of Alaska, Fairbanks, AK; fnscp@uaf.edu (U. Alaska postdoctoral scholar)

Matthew Polizzotto Dept. of Geological & Environmental Sciences, Stanford University; mattyp@stanford.edu (Stanford postdoctoral scholar)

Soni Shukla Dept. of Civil & Environmental Engineering, Stanford University; sonis@stanford.edu (Stanford postdoctoral scholar)

Hagar Siebner Dept. of Geological & Environmental Sciences, Stanford University; siebner@stanford.edu (Stanford postdoctoral scholar)

David Singer Dept. of Geological & Environmental Sciences, Stanford University; dmsinger@stanford.edu (Stanford graduate student)

Mary Van der Hoven Dept. of Geological & Environmental Sciences, Stanford University; mtvand2@stanford.edu (Stanford graduate student)

Yingge Wang Dept. of Geological & Environmental Sciences, Stanford University; ygwang@stanford.edu (Stanford graduate student)

Ira Waluyo Stanford Synchrotron Radiation Laboratory; iwaluyo@stanford.edu (Stanford graduate student)

Samantha Ying Dept. of Geological & Environmental Sciences, Stanford University; samying@gmail.com (Stanford graduate student)

Jihae Yoon Dept. of Geological & Environmental Sciences, Stanford University; jhyoon1@pusan.ac.kr (Stanford postdoctoral scholar)

GuestsJohn Bargar Stanford Synchrotron Radiation Laboratory, bargar@slac.stanford.edu Katrin Otte Dept. of Earth and Environmental Sciences, U. Munich

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Rossitza Pentcheva University of Munich; Rossitza.Pentcheva@lrz.uni-muenchen.de

Abstracts of Oral Presentations(in order of presentation)

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Density Fluctuations in Water with a Bimodal Distribution of Local Structures

Congcong Huang1, K. T. Wikfeldt2, T. Tokushima3, D. Nordlund1, Y. Harada3, U. Bergmann1, M. Niebuhr1, T. Weiss1, M. Leetmaa2, M. P. Ljungberg2, A. Giertz5, L. Ojamäe5, A. P.

Lyubartsev6, O. Takahashi4, S. Shin1,7, L. G. M. Pettersson2 and A. Nilsson1

1 Stanford Synchrotron Radiation Laboratory, P.O.B. 20450, Stanford, CA 94309, USA2 FYSIKUM, Stockholm University, AlbaNova, S-10691 Stockholm, Sweden

3 RIKEN/SPring-8, Sayo-cho, Sayo, Hyogo 679-5148, Japan4 Department of Chemistry, Hiroshima University, Higashi-Hiroshima 739-8526, Japan

5 Department of Chemistry, Linköping University, S-581 83 Linköping, Sweden6 Division of Physical Chemistry, Stockholm University, S-10691 Stockholm, Sweden

7 Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan

Liquid water shows many anomalies in its thermodynamic properties such as compressibility, density variation, and heat capacity. In the low-temperature regime, below the freezing point, these properties deviate particularly strongly from a normal liquid. Although the anomalies are extreme in the supercooled region, they are also present at ambient conditions where most of the physical, chemical, and biological processes involving water occur. Here we show using small angle x-ray scattering the presence of density fluctuations with a correlation length of around 1 nm in ambient water. X-ray emission1 and x-absorption spectroscopy2

measurements shows that the fluctuations give rise to a bimodal distribution of two distinct local structures; low density–low entropy tetrahedral and high density–high entropy highly hydrogen-bond distorted structures. In the fluctuating network, the structure of the tetrahedral local structure shows no detectable change with temperature, whereas the structure of the high density component changes continuously with temperature. We propose that the tetrahedral and the high density-high entropy structure are related to low- and high-density amorphous ice, respectively. The high-density structure dominates in the liquid at ambient conditions and is related to structures with strongly perturbed hydrogen-bonds, giving the spectral features in the x-ray absorption spectra as discussed in the much debated 2004 Science paper2. The present results show that the anticipated extreme differences in the hydrogen bonding environments in the supercooled regime remain at ambient conditions well above a potential second critical point at -45°C between low- and high-density water.

1. Tokushima, T., Harada, Y., Takahashi, O., Senba, Y., Ohashi, H., Pettersson, L. G. M., Nilsson, A., and Shin, S., High resolution x-ray emission spectroscopy of liquid water: The observation of two structural motifs. Chem. Phys. Lett. 460, 387-400 (2008) (Frontier Article).

2. Wernet, Ph., Nordlund, D., Bergmann, U., Cavalleri, M., Odelius, M., Ogasawara, H., Näslund, L. Å., Hirsch, T. K., Ojamäe, L., Glatzel, P., Pettersson, L. G. M., and Nilsson, A., The structure of the first coordination shell in liquid water. Science 304, 995-999 (2004).

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Water and OH Adsorption on Metal Surfaces andTheoretical Modeling of Diffraction and OH Stretch IR/Raman

Lars G. M. Pettersson

FYSIKUM, AlbaNova University Center, Stockholm University S-106 91 Stockholm, Sweden

In this talk I will first discuss factors determining the bonding of water and coadsorbed hydroxyl to metals. Bonding to structurally isomorphic but electronically different Pt(111) and Cu(111) will be compared as well as to the electronically isomorphic but structurally different Cu(110) and Cu(111) surfaces. The focus will be on the theoretical analysis of the bonding with introduction of the techniques used. In the second part of the talk I will discuss Reverse Monte Carlo (RMC) modeling of x-ray and neutron diffraction data in connection with popular molecular dynamics (MD) simulation models for water. RMC can be used to fit any data set that can be computed based on a structure model. It is thus a powerful and general tool for developing and evaluating structure models, but requires very fast and thus often approximate computational techniques. Here I will critically analyze the commonly used E-field approximation to OH stretch IR/Raman spectra and will also demonstrate a promising application of RMC to x-ray absorption spectroscopy (XAS).

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Interaction of Water with BaF2(111) at Ambient Conditions

Susumu Yamamoto1, Sarp Kaya 1 , Ning Dong Huang1, John T. Newberg2, Hendrik Bluhm2, and Anders Nilsson1

1 Stanford Synchrotron Radiation Laboratory, P.O.B. 20450, Stanford, CA 94309, USA2 Chemical Sciences Division, Lawrence Berkeley National Laboratory,

Berkeley, CA 94720, USA

Aggregation of water and ice nucleation on ionic surfaces have been topics of interest for many years due to their importance in environmental and atmospheric chemistry. A thin film of water covering solid surfaces can participate in transformations, which in most of the cases cause modifications in their surface structures, reactivates, etc. Of particular interest is the formation and nature of the first few layers of water where its molecular environment is expected to be different. Depending on the differences between water-water and water-surface interaction energies, water molecules can be found in the form of clusters or two-dimensional wetting layers. As an ionic salt, BaF2(111) is considered to be a promising model surface at which the formation of a wetting layer of ice is expected due to the close match between the lattice parameters of the surface and of ice. In addition, due to the slightly soluble nature of BaF2, the surface chemistry might be influenced by dissolution of the surface ions from the solid phase through interactions with water molecules.

We have investigated the structural building blocks of water molecules on BaF2(111) surface at relative humidity (RH) values ranging between 1% and 95 %. In-situ X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) measurements were performed at H2O partial pressures up to 1.5 Torr using the Ambient Pressure Photoelectron Spectroscopy (APPES) setup at the Advance Light Source (ALS). Oxygen K-absorption edge spectrum was used as a direct meausure of the local bonding structure of water molecules adsorbed on BaF2(111) surfaces. Even at RH values lower than 5%, an apparent increase of absorption intensity was observed. Accordingly, it was also found by XPS that monolayer coverage can be obtained at 10-15% RH. Even though spectra measured with different polarizations are similar, some small differences were observed in the pre-edge (~535 eV) and main edge (542 eV). These changes in pre- and post-absoption edges reveal that the structure of water on the BaF2(111) surface is similar to the topmost surface of hexagonal ice (or like liquid water) which is lacking two-dimensional long-range order. Additional water layers obtained at higher relative humidities have slightly different hydrogen bonding structures. In addition, the lateral hydrogen bonding network becomes more apparent with increasing water coverage.

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Thin Film Water on MgO(100): A New Perspective Using APPES

John T. Newberg1, David E. Starr1, Susumu Yamamoto2, Sarp Kaya2, Hirohito Ogasawara2, Tom Kendelewicz3, Miquel B. Salmeron4, Gordon E. Brown, Jr.3, Anders Nilsson2

and Hendrik Bluhm1

1 Chemical Sciences Division, Lawrence Berkeley National Laboratory,

Berkeley, CA 94720, USA2 Stanford Synchrotron Radiation Laboratory, P.O. Box 20450, Stanford, CA 94309, USA

3 Surface and Aqueous Geochemistry Group, Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94309, USA

4 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA

Water on MgO(100) is one of the most widely studied water‐surface interactions, both

theoretically and experimentally, due to the simple rock salt cubic structure of MgO. However, fundamental questions about whether water adsorbs molecularly or dissociatively under ambient conditions remain unanswered. We present results on the interaction of water with MgO(100) films grown on Ag(100) using ambient pressure photoemission spectroscopy (APPES). XPS results show that at ~0.1% relative humidity (RH) ~0.3 ML of water is observed on the MgO surface (1 ML = 0.31 nm). However, at this RH the surface of MgO is completely passivated with an overlayer of hydroxide that has a thickness similar to that of brucite (Mg(OH)2 (1 ML = 0.48nm). Thus, molecular water is no longer interacting with MgO(100), but instead with a chemically transformed OH‐terminated surface. As the RH is increased from 0.1% to 25%, the brucite overlayer thickness remains at ~1 ML, while the thin film water increases from ~0.3 to 1.5 ML. Polarization-dependent O K‐edge NEXAFS show that the OH‐moieties have out‐of‐plane transitions, consistent with the vertically oriented hydroxide geometries seen in the bulk brucite crystal structure. The formation of a brucite overlayer is consistent with a favorable Gibbs free energy for the bulk reaction of liquid and gas phase water with MgO (‐27 and ‐36 kJ/mol, respectively). These results indicate that even under the lowest ambient RH values in the environment, metal oxides that have thermodynamically stable hydroxides are chemically transformed at the surface due to thin film water. Thus, the mere presence of thin film water can have great implications for how mineral surfaces interact with organic, biological, and toxic inorganic species in the environment.

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Surface Structure and Composition of Oxidized and Reduced Hydrated Magnetite (111)

Sarah C. Petitto1, Raena J. Rowland1, Kunaljeet S. Tanwar1, Sanjit K. Ghose2, Peter J. Eng2, Michael F. Toney3, and Thomas P. Trainor1

1Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, AK 997752Consortium for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60439

3Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, CA 94025

Mineral surfaces, particularly Fe-(hydr)oxides, play a predominant role in controlling the composition of natural waters and regulating the transport and bioavailability of aqueous contaminants. A key to understanding the role these interfaces play in the environment is the development of detailed structural models that allow for structure/reactivity relationships to be determined for predicting the extent and rate of chemical reactions. The synchrotron-based X-ray crystal truncation rod (CTR) diffraction was used to determine surface structure, relaxations, and chemical identity of surface moieties of a magnetite (Fe3O4) (111) surface prepared via chemical and mechanical polishing (CMP). Exposing the Fe3O4(111) to hydrated conditions resulted in a surface with two co-existing structural domains: 75% oxygen-octahedral iron and 25% oxygen-tetrahedral-octahedral-tetrahedral iron (mixed-iron termination). The CMP-prepared hydrated surface also is found to undergo structural modification as a function of a hydration time (hours to days) where the mixed-iron termination lattice sites are sequentially becoming less occupied with time. These changes indicate that the Fe3O4(111) surface is undergoing a weathering-type process, which results in an oxygen-octahedral iron termination as the dominant surface structure. These results imply that the iron atoms occupying the octahedral lattice sites are the more stable iron lattice sites and the more probable principal irons that control the surface reactivity of magnetite.

To control and understand how the surface structure/composition changes with varying redox conditions, electrochemical impedance spectroscopy (EIS) was used where the resultant surface was characterized using in-situ CTR, X-ray surface diffraction phase and texture analyses, and flow injection analysis of Fe(II) along with ex-situ atomic force microscopy (AFM). The EIS results show the oxidized then re-reduced surface has a slightly higher resistance compared to the initially reduced surface with a highly rough surface as no CTR’s were obtained. However, X-ray surface diffraction phase and texture analyses found the co-existence of textured iron-oxide phases: magnetite (Fe3O4) (001), hematite (a-Fe2O3) (110) and (006), and goethite (FeOOH) (200) in the near surface region. Complementary AFM images show the formation of surface precipitates, suggesting the ordered surface is buried under these globules and the presence of other iron-oxide phases. The terminating surface structures of oxidized and reduced Fe3O4(111) surfaces determined as a function of time and variable redox conditions are used as a model pathway for how a magnetite surface might evolve under environmental conditions in nature, and its implication on the surface reactivity will be discussed.

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Reduction of U6+ by Magnetite:Observed Oxidation States and Calculated Rates of Electron Transfer

Frances N. Skomurski, Sebastien Kerisit, Eugene S. Ilton, and Kevin M. Rosso

Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA

The reductive adsorption of U6+ in solution by Fe2+ in magnetite (Fe3O4) retards radionuclide transport in some sub-surface environments and helps minimize radionuclide release from waste-packaging materials surrounding spent nuclear fuel. Experimentally, magnetite reduces U6+ to U4+; however, reduction is not always complete, resulting in mixed-valent U on the magnetite surface [1,2]. In order to explore whether heterogeneous electron transfer could be a rate-limiting step in the reduction of U6+ by magnetite, both experimental and computational techniques were used in this study. First, natural magnetite samples were cleaved parallel to the (001) surface and exposed to uranyl-nitrate solution at pH 4.5 under anoxic conditions for ~90 hours. U4+/U5+/U6+ and Fe2+/Fe3+ ratios on both clean and U-exposed surfaces were measured using XPS. Results indicate a significant amount of U6+ adsorption on both samples, but partial reduction to U5+ was only observed on one sample. Differences in initial Fe2+/Fe3+ ratios of each sample may contribute to the discrepancy in the amount of observed U-reduction. These results indicate that reduction is dependent on the availability of surface Fe2+, which in part depends on the transport of electrons from the bulk to the surface.

Before comparisons can be made for electron-transfer rates between Fe2+ (in magnetite) and U6+ (adsorbed), rates of electron transfer must be established for magnetite surface environments. Quantum-mechanical calculations were used to determine the availability of Fe2+ in vacuum-terminated versus hydrated (001) surface environments, and to calculate rates of electron transfer between edge-sharing Fe2+O6 and Fe3+O6 octahedra from a variety of bulk and surface environments. The amount of atomic relaxation surrounding the iron dimers was found to significantly affect rates of electron transfer. At surfaces, where atomic relaxation varies depending on local site structure and proximity to the surface plane, rates of electron transfer span five orders of magnitude from 109-1014 hops/second. Electron transfer rates measured for magnetite powders are in the range of 1012 hops/second [3]. In general, rates for both vacuum and hydrated surfaces are generally 2 to 3 orders of magnitude slower than bulk-like rates, and surprisingly the presence of water does not have a significant effect on charge distribution or on rates of electron transfer. These findings suggest that slow Fe2+/Fe3+ interchange rates at the surface could be rate-limiting if processes such as reductive adsorption involve similar rates of electron transfer.

Finally, a quantum mechanical cluster approach was used to determine rates of electron transfer between Fe2+ in magnetite and U6+ by docking a hydrated uranyl molecule to representative iron dimer moeities in a bidentate, inner-sphere fashion. Since complete reduction to U4+ requires a two-electron-transfer process, energies were calculated for the following reaction steps: U6+/Fe2+/Fe2+, U5+/Fe2+/Fe3+, and U4+/Fe3+/Fe3+. The reduction of U6+ to U5+ is energetically favorable, and rates of electron transfer are on the order of 106 hops/second. However, the reduction of U5+ to U4+ with this configuration is not energetically favorable. Increasing the number of coordinating ligands for the U4+ cation was assessed but did not increase the endergonicity of conversion to U4+. If a less-reducing starting case is considered

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(i.e. U6+/Fe2+/Fe3+), then the reduction to U5+ is less favorable, indicating that the locally available concentration of Fe2+ is a large driving force in the reduction of U6+ on the magnetite surface. These results are fully consistent with the experimental cases described above where more reduction is seen for the stoichiometric magnetite than the slightly oxidized sample. [1] Missana et al. , J. Colloid Interface Sci. 261, 154-160 (2003). [2] Scott et al., Geochim. Cosmochim. Acta 69 (24), 5639-5646 (2005).[3] Mizoguchi and Inoue, J. Phys. Soc. Jpn. 21 (7), 1310-1323 (1996).

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Computational Surface Studies of Metal Ion Partitioning on Hematite

Christopher R. Iceman1, Kunaljeet S. Tanwar1, Sara E. Mason2, Anne M. Chaka2, and Thomas P. Trainor1

1Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, AK 997752Physics Department (Optical Technology Division), National Institute of Standards and

Technology, Gaithersburg, MD 20899Iron oxides are widely abundant natural substrates that influence transport and

availability of numerous environmental contaminants. In aqueous environments, the surface structure and therefore reactivity of iron oxide surfaces can be altered by physical and chemical changes in the environment. This in turn will influence the equilibrium partitioning ratios of metals ions (and other species) to mineral surfaces, which are dictated by thermodynamic stability of the sorption complex and solvation free energy of the aqueous ions. However, a detailed and systematic description of the energetics involved in the transfer of ions to the surface from the solution phase and vice versa is lacking from our current ab initio thermodynamics models of interfacial processes. The current study is focused on providing a thermodynamic description of how surface energy varies with extent of metal ion (specifically Fe3+) partitioning on hematite surfaces and developing a methodology to account for the solvation energy of Fe3+ within the overall thermodynamic potential (i.e. Gibbs Free Energies) of the mineral/fluid systems.

Density functional theory (DFT) calculations are being used to examine the structure and surface energies of hydroxylated hematite(1-102) with variable amounts of additional Fe3+

included at the crystal lattice sites at the surface. Currently five unique surface coverage geometries representing 25, 50, and 75% filling of surface lattice sites are being considered. These modified surfaces are being explored to ascertain the surface energy as a function of percentage site occupancy. Interestingly, the results suggest the hydrogen-bonding network at the surface contributes significantly to the surface energetics and entropies of these structures. Furthermore, complementary calculations of the solvation enthalpy and free energy of Fe3+ has shown that available solvation models are adequate for use in ab initio thermodynamic surface energy calculations. Calculation of the free energies involved in solute partitioning from the liquid phase to the surface will be needed to accurately describe systems where layer occupancies are variable. These methods compare directly to previous work and are extended for use with new solvation models and ab initio quantum mechanical methods employed in gas phase studies.

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Pb(II) Adsorption on Isostructural Hydrated Alumina andHematite (0001) Surfaces: A DFT Study

Sara E. Mason1,2, Christopher R. Iceman2 , Kunaljeet S. Tanwar2 , Thomas P. Trainor2 , and Ann M. Chaka1

1 Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA

2 Department of Chemistry and Biochemistry, University of Alaska Fairbanks, P.O. Box 756160, Fairbanks, AK 99775, USA

The persistence of lead (Pb) in contaminated topsoil is ranked as one of the most serious environmental issues in the U.S. and other countries. Adsorption of Pb at the aqueous interface of nanoscale metal oxide and metal (oxy)hydroxide particles is perhaps the most significant process responsible for controlling contaminant sequestration and mobility but is poorly understood. Experimental studies of absorption of Pb onto bulk minerals has indicated significant differences in reactivity, but the molecular basis for these differences has remained elusive due to the challenges of observing and modeling the complex chemistry that exists at the water-oxide interface. In this work we present a detailed ab initio theoretical investigation aimed at understanding the fundamental physical and chemical characteristics of Pb adsorption onto the (0001) surface of two common minerals, α–Al2O3 and α–Fe2O3. The results of our periodic density functional theory (DFT) calculations show that Pb(II) binds more strongly (by ≈30%) to hematite than to isostructural alumina with the same fully hydroxylated surface stoichiometry due to stabilization of the Pb-O covalent interactions by the partially occupied Fe d-band. Site preference for Pb(II) adsorption on alumina is shown to depend strongly on the cost to disrupt highly stable hydrogen bonding networks on the hydrated surface, but is less of a factor for the stronger Pb-hematite interaction.

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Structural Aspects of Synthetic Ferrihydrite

F. Marc Michel1, Cristina Cismasu1, A. Patricia Tcaciuc2,John B. Parise3, and Gordon E. Brown Jr.1,4

1 Surface & Aqueous Geochemistry Group, Department of Geological and Environmental Sciences, Stanford University, Stanford, CA, USA

2 Departments of Chemistry and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA

3 Department of Geosciences, Stony Brook University, Stony Brook, NY, USA4 Stanford Synchrotron Radiation Laboratory, SLAC, Menlo Park, CA, USA

The role of natural ferrihydrite in geochemical and biological systems and the use of synthetic ferrihydrite in technological and industrial applications are attracting broad scientific attention. The importance of ferrihydrite in these systems is primarily related to its large reactive surface area (>350 m2∙g-1) which has been shown to effectively scavenge a variety of potential contaminants (e.g., arsenic, chromium). In general, the association of ferrihydrite with metals and metalloids through sorption and co-precipitation is expected to alter its reactivity and thus affect its overall role in aqueous geochemical systems. Such changes in the reactivity of ferrihydrite nanoparticles, typically with all dimensions less than ~7 nm, are inextricably related to their atomic structure, i.e., the 3-dimensional arrangement of atoms. Evaluating the structures of particles with extreme small particle sizes (<10 nm) and substantial disorder has proven difficult by conventional methods for structure determination, which are most sensitive to either short-range order (X-ray absorption spectroscopy) or long-range periodicity (X-ray or electron diffraction). However, the recent application of high-energy X-ray total scattering coupled with pair distribution function (PDF) analysis is providing new insight into the structural aspects of ferrihydrite, a material with no known crystalline counterpart. The information obtainable both directly and indirectly from the PDF will be discussed primarily using examples of synthetic inorganically derived ferrihydrites. This work on synthetic samples complements our investigations of natural ferrihydrites forming in acid mine drainage-impacted waters. Such natural samples are inherently more complex because they typically form in the presence of dissolved inorganic species such as silica, aluminum, chromium, sulphate, etc., as well as organic matter. The complexity of natural ferrihydrites necessitates the use of synthetically-derived samples in order to evaluate specific changes in certain fundamental aspects of these phases, i.e., size, shape, composition, and structure.

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Molecular- and nm-scale Investigation of the Structure and Compositional Heterogeneity of Naturally Occurring Ferrihydrite

Cristina Cismasu1, F. Marc Michel1, Jonathan F. Stebbins2, A. Patricia Tcaciuc3 and Gordon E. Brown Jr.1,4

1 Surface & Aqueous Geochemistry Group, Department of Geological and Environmental Sciences, Stanford University, Stanford, CA, USA

2 Solid State NMR Facility, Department of Geological and Environmental Sciences, Stanford University, Stanford, CA, USA

3 Departments of Chemistry and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA

4 Stanford Synchrotron Radiation Laboratory, SLAC, Menlo Park, CA, USAFerrihydrite is a hydrated Fe(III) nano-oxide that forms in particularly vast quantities in

contaminated acid mine drainage environments. As a result of its high surface area, it is one of the most important environmental sorbents, and plays an essential role in the geochemical cycling of pollutant metal(loid)s in these settings. Despite its environmental relevance, this nanomineral remains one of the least understood environmental solids in terms of its structure (bulk and surface), compositional variations, and the factors affecting its reactivity. Under natural aqueous conditions, ferrihydrite often precipitates in the presence of several inorganic compounds such as aluminum, silica, arsenic, etc., or in the presence of organic matter. These impurities can affect the molecular-level structure of naturally occurring ferrihydrite, thus modifying fundamental properties that are directly correlated with solid-phase stability and surface reactivity. Currently there exists a significant gap in our understanding of the structure of synthetic vs. natural ferrihydrites, due to the inherent difficulties associated to the investigation of these poorly crystalline nanophases. In this study, we combined a variety of synchrotron- and laboratory-based techniques to characterize naturally occurring ferrihydrite from an acid mine drainage system situated at the New Idria mercury mine in California. We used scanning transmission X-ray microscopy (STXM) high resolution imaging (30 nm) to evaluate the spatial relationship of major elements Si, Al, and C within ferrihydrite. Al and Si K-edge near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and 27Al nuclear magnetic resonance (NMR) spectroscopy were used to obtain short-range structural information. We have additionally used high-energy X-ray total scattering and pair distribution function (PDF) analysis to elucidate quantitative structural details of these samples. By using this array of techniques we attain the highest level of resolution permitted by current analytical methods to study such naturally occurring nanomaterials, both at the molecular- and nm-scale. This work provides structural information at the short-, medium- and long-range, and provides evidence of compositional heterogeneity with respect to the major elements, as well as evidence of mineral/organic matter associations.

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Iron Biomineralization by Anaerobic Neutrophilic Iron-Oxidizing Bacteria

Jennyfer Miot1, Karim Benzerara1, Martin Obst2, Andreas Kappler3, Gordon E. Brown, Jr.4,

and Guillaume Morin1

1 Institut de Minéralogie et de Physique des Milieux Condensés, UMR 7590, CNRS and IPGP, Paris, France

2 BIMR McMaster University Hamilton & Canadian Light Source3 Center for Applied Geoscience (ZAG), Tuebingen, Germany

4 Surface & Aqueous Geochemistry Group, Department of Geological & Environmental Sciences, Stanford University, USA

Iron-oxidizing bacteria (IRB), which couple Fe(II) oxidation to nitrate or CO2 reduction under anoxic conditions and at neutral pH, were discovered only a few years ago (Widdel et al., 1993, Straub and Buchholz-Cleven, 1998). IRB may have a major impact on the Earth’s surface geochemistry and the mobility of metal pollutants; however, the way they deal with Fe(III), which is highly insoluble under neutral pH conditions, is still poorly understood. In this talk, we will focus on Fe-biomineralization by two different bacterial strains: BoFeN1, a -Proteobacterium close to Acidovorax sp., which couples oxidation of iron to nitrate reduction, and Rhodobacter sp. strain SW2, a phototrophic iron-oxidizing bacterium. It has been reported previously that these bacteria show different biomineralization patterns (Kappler and Newman, 2003; Kappler et al. 2005). Although BoFeN1 cells become incrusted by Fe-precipitates, SW2 cells keep iron precipitate formation away from the cellular structures. Over the last two years, we have carried out additional studies of these biomineralization patterns in order to understand the origin of these differences (Miot et al., submitted to GCA; Miot et al., in prep for AEM).

The identity of the biominerals formed through Fe(II) bio-oxidation was determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The texture, structure, and chemistry of these minerals were followed at the nanometer scale by Scanning Transmission Electron Microscopy (STEM) and synchrotron-based Scanning Transmission X-ray Microscopy (STXM) along the time course of a culture. STXM analyses provided information on the speciation (type of bonding and redox state) of both carbon and iron at the 20-nm scale. In particular, the redox state of iron-bearing phases was mapped at the submicrometer-scale. The progressive oxidation of Fe(II) and subsequent changes in the mineralogy of Fe rich phases were shown to be associated with the progressive encrustation of the BoFeN1 cells. Additionally, an intimate mixture of organic carbon species and iron-rich minerals resulting from bacterial activity was observed in both BoFeN1 and SW2. Finally, we used cryo-ultramicrotomy and cryo-TEM to image the association between organic molecules and Fe-precipitates within the encrusted BoFeN1 cells down to the nm-scale.

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This study provides a precise scenario at the submicrometer scale of the mineralogical evolution of iron biomineralization, triggered by iron-oxidizing bacteria under anoxic conditions.

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Surface Functional Groups on Bacterial Cell Surfaces:Composition and implications for metal and mineral surface binding

Satish C. B. Myneni and Bhoopesh Mishra

Department of Geosciences, Princeton University, Princeton, NJ 08544

Bacteria are ubiquitous in the environment and play an important role in several biogeochemical processes in the natural and contaminated environments. Surface functional groups of bacteria and the reactions involving them are important variables that modify the function of bacteria in bacterial mediated biogeochemical reactions. However, the surface chemistry of bacteria is poorly understood, and most of what is currently known about bacteria surfaces is derived from the extraction and isolation of cell wall membranes and potentiometric titrations.

Using XAS and X-ray spectromicroscopy (STXM), and infrared spectroscopy we studied the C-, N-, P-, and S-functional group composition of several different Gram-positive and Gram-negative bacterial species in a variety of solution chemical conditions. The STXM studies on C-functional groups indicated the presence of unsaturated C=C representing different aliphatic and aromatic moieties, C=O of amide and carboxyls, and C-N of amines in high abundance. The relative concentration of amides and carboxyls was evaluated using surface sensitive infrared spectroscopy, which indicated that amide groups are present at much higher concentration than carboxyls in all of the bacterial species examined. Although similar results were reported for C-functional groups in the previous STXM studies conducted on different bacterial species, the interpretation regarding the concentration of amides and carboxyls is debatable for some of them.

The studies of N-functional groups indicated the presence of amine and amide groups in high abundance and also showed evidence of weak signatures representing C=N groups. While many of these groups do not exhibit strong affinity to metals and mineral surfaces on their own, the unsaturated C=N groups may play an important role in metal binding. The identified P-groups are primarily in the form of phosphate esters, which is not surprising considering the P-chemistry of cell wall membranes. The S functional groups identified are primarily in the form of sulfides with traces of oxidized sulfur (sulfonate and sulfate). The sulfides are identified as cysteine and methionine, with traces of cystine. Cysteine, identified from cell potentiometric titrations, is also considered to be in a small fraction. Interestingly all these groups are common to both Gram-positive and Gram-negative bacterial surfaces without any detectable differences.

We also examined the reactions of Hg with the bacterial cells at a range of Hg concentrations and solution pH conditions. These in-situ XAS (XANES & EXAFS) studies showed surprises regarding the binding sites of Hg in the very low Hg concentration range. A summary of our studies on surface functional groups of bacteria and their reactions with Hg will be discussed.

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Study of Proton, Pb+2 and Zn+2 Adsorption onto Shewanella oneidensis MR-1 Strain and a Mutant Strain (ΔEPS): Spectroscopic Observation

and Modeling Approach

Juyoung Ha1, Alexandre Gélabert1, Yingge Wang1, Alfred M. Spormann2,and Gordon E. Brown, Jr.1,3

1Surface & Aqueous Geochemistry Group, Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA

2Department of Civil & Environmental Engineering, Stanford University, Stanford, CA, USA 3Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road, SLAC, MS 69, Menlo Park,

CA 94025, USA

In this study we examined the adsorption affinities of Pb2+ and Zn2+ on Shewanella oneidensis strain MR-1 (wild type) and a mutant strain (ΔEPS), which is deficient in exopolysaccharide (EPS) production, and developed a model to describe the thermodynamic and chemical properties of the bacterial surfaces.

ATR-FTIR spectra of wild type and the ΔEPS mutant strain both exhibited carboxyl, amide, phosphate, and carbohydrate groups. Potentiometric titrations indicated that both wild type and ∆EPS mutant cells exhibit similar surface charge as a function of pH, suggesting a weak contribution of the removed polysaccharides to the overall charge of S. oneidensis surfaces. Negative electrophoretic mobilities at pH > 3.5 were observed on both strains of S. oneidensis indicating that the outermost layer of organic groups, such as carboxyls, bear negative charges. No significant differences in metal uptake were observed for the three different ionic strengths investigated (1M, 0.1M, and 0.01M of NaNO3), indicating that the structure of the cell wall does not depend on electrolyte concentration. Extended X-ray absorption fine structure (EXAFS) spectroscopic studies of Zn2+ and Pb2+ on both strains of bacteria were combined with equilibrium titration studies to investigate the nature of metal binding sites on S. oneidensis. Based on these experimental results, the thermodynamic stability of metal complexes on the two different strains of S. oneidensis and the concentration of binding sites on the bacterial surfaces for such complexes will be discussed.

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CymA-independent Respiratory Plasticity in Shewanella oneidensis MR-1

Carmen Cordova and Alfred M. Spormann

Departments of Chemical Engineering, of Civil and Environmental Engineering, of Geological and Environmental Sciences, of Biological Sciences

Stanford University

Shewanella oneidensis MR-1 respires a variety of compounds under anaerobic conditions, including Fe(III) and Mn(IV) present in a mineral phase. Such respiratory versatility is facilitated through a complex branched electron network which includes cytochromes, iron-sulfur proteins, quinones, and dehydrogenases. A common branch point to several respiratory pathways is the electron transfer protein, CymA. CymA is a cytoplasmic membrane bound tetraheme cytochrome c protein that is believed to transfer electrons from the quinol pool to different periplasmic oxidoreductases. In order to fully understand the path of electron transfer through the cell to external electron acceptors, we previously created various CymA constructs which included mutant forms deficient in each of the heme attachment sites. Our results indicated that the integrity of each heme attachment site was required for respiration on DMSO, ferric citrate, and fumarate either directly for electron transfer or indirectly, for protein stability. Furthermore, this approach allowed for identification of a suppressor mutant that is capable of CymA-independent respiration on electron acceptors previously linked to CymA-dependent respiratory pathways. Our experiments show that a suppressor mutant isolated under fumarate respiring conditions is capable of respiring on other electron acceptors such as nitrate and DMSO. There exists evidence to support that the nature of the suppressor mutation is extragenic. In addition and in contrast to the complemented parental strain, the suppressor strain shows a different response of susceptibility towards DCCD, an ATP synthase inhibitor, under fumarate respiring conditions. While our previous work indicated that CymA had various roles both as a central electron transfer protein and also as a terminal metal reductase, our work here illustrates that an alternative route of electron transfer (independent of CymA) through the cell towards external electron acceptors may exist. Our current efforts are directed towards finding the genetic basis of suppression.

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Bacterial Nanowires and Long-Range Electron Transfer

Yuri A. Gorby

J. Craig Venter Institute, 10355 Science Center Drive, San Diego, CA 92129

Bacteria catalyze redox reactions that can significantly influence the fate and transport of heavy metals, radionuclides, and organic contaminants in subsurface sediments and groundwater. Approaches for remotely detecting, monitoring, and controlling microbial redox reactions require an improved understanding of the components and mechanism that coordinate electron transfer reactions. Recent research demonstrates that organisms ranging from sulfate-reducing bacteria to oxygenic, phototrophic cyanobacteria produce electrically conductive appendages called bacterial nanowires. Dissimilatory metal-reducing bacteria, such as Shewanella and Geobacter, produce nanowires that mediate the transfer of electron from cells to solid phase electron acceptors, such as iron and manganese oxides. This presentation will provide a status report on our current understanding of bacterial nanowires and their role(s) in extracellular electron transfer.

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Competitive Redox and Adsorption Reactions of Arsenic between Iron and Manganese Oxides

Samantha C. Ying1, Benjamin D. Kocar1, Chris Francis2, and Scott Fendorf2

1 Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 2 Department of Environmental Earth Systems Science, Stanford University, Stanford, CA

Manganese and Fe (hydr)oxides are ubiquitous phases that occur in terrestrial systems and are principal sorbents for many trace metals, including arsenic (As).  Their propensity for arsenic retention is, however, further modified by redox conditions and that is particularly relevant at the anaerobic-aerobic interface.  Here, the high redox potential of Mn(III/IV) oxides relative to As(III), and in contrast to Fe(III) oxides, leads to As(V) production and consequential greater arsenic retention.  Thus, despite typically being present at concentrations less than one tenth that of Fe oxides, Mn oxide phases may have controlling influences on arsenic retention.   Accordingly, here, we examine competitive arsenic retention upon As(III) reaction with the Fe oxide goethite and Mn oxide birnessite.  Using a Donnan cell—where each oxide is isolated by a semi-permeable membrane through which arsenic can migrate—we are able to decipher the time-dependent retention of arsenic on each phase.  Our results demonstrate that Mn oxides rapidly oxidize As(III) to As(V) and initially retain the proportionally greatest quantity of arsenic; however, subsequent desorption and diffusional transport leads to an increasing quantity of As(V) on goethite.  Our results demonstrate an intricate redox and retention process whereby Mn oxides serve to increase arsenic retention on both Fe and Mn solids. 

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Defining and Simulating the Coupled Biogeochemical and Hydrologic Processes Governing Arsenic Mobility within Soils and Sediments of the

Mekong Delta, Cambodia

Benjamin Kocar1, Matthew Polizzotto1, Samantha Ying1, Shawn Benner2, Mickey Sampson3, and Scott Fendorf4

1Department of Geological & Environmental Sciences, Stanford University, Stanford CA2Department of Geology, Boise State University, ID

3Resource Development International, Cambodia4 Department of Environmental Earth Systems Science, Stanford University, Stanford, CA

Weathering of As-bearing rocks in the Himalayas has resulted in the transport of sediments down major river systems such as the Brahmaputra, Ganges, Red, Irrawaddy, and Mekong. Groundwater in these river basins commonly has As concentrations exceeding the World Health Organization's recommended drinking water limit (10 µg/L) by more than two orders of magnitude. Coupling of hydrology and biogeochemical processes underlies the elevated concentrations of arsenic in these aquifers, necessitating studies that allow their deconvolution. We used a combination of spectroscopic and wet chemical measurements to resolve the dominant processes controlling As release and transport in surficial soils/sediments within an As-afflicted field area of the Mekong delta. Our results illustrate that clay (0-12m deep) underlying oxbow and wetland environments are subjected to continuously reducing conditions due to ample carbon input and saturated conditions. Ensuing reductive mobilization of As from As-bearing Fe (hydr)oxides results in its migration to the underlying sandy aquifer (>12 m deep). Reactive transport modeling using PHREEQC and MIN3P was constrained with chemical and hydrologic field measurements, and provides a calibrated illustration of As release and transport within our field site. Our resulting simulations indicate that As release occurs within the clays underlying organic-rich, permanently inundated locations providing sufficient As to the aqueous phase for widespread contamination of the aquifer, and that release occurs for several thousand years prior to depletion of As from the solid phase.

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Update on Educational Outreach in 2007-08

Bryan Brown1 and Jennifer Saltzman2

1 School of Education, Stanford University2 School of Earth Sciences, Stanford University

The Stanford EMSI educational outreach program consists of workshops for high school science teachers and for science journalists. In the summer of 2008, the EMSI continued its efforts to provide outreach to local educators. We provided our annual summer workshop to 12 participants teachers. These participants were high school teachers (chemistry, biology and environmental science). We continued with the 4-day workshop, and added a tour of the New Almaden Mine as well as some problem sets. This group of teachers spent a lot of time formulating their lesson plans and are well prepared to teach their lessons in the classroom. The written lessons plans as well as the video of teachers in the classroom will be hosted on our ‘Web Learning Center’ website at http://emsi-teacherworkshop.stanford.edu.

On the educational research side, we have been investigating how teachers are developing the ability to integrate emerging scientific findings into their everyday teaching of simple scientific ideas. We conducted pre- and post- interviews of the 25 teachers who participated in the 2005 and 2006 workshop. We are currently analyzing the results from the interviews and plan to submit the results from our finding in an educational research journal.

In conjunction with the Society of Environmental Journalists annual meeting, we presented a one day workshop to 23 science journalists on September 5, 2008. The focus of the “Atoms to Ecosystems: Effects of Contaminants on Humans & the Environments” workshop was on the environmental chemistry of mercury and arsenic, both of which have appeared in many news articles over the past few years because of their widespread impact on humans. This was offered a pre-meeting option. We attracted an international audience as well as a broad reach across the US (California, Nebraska, Colorado, Virginia, New York, North Carolina). Two journalists from Canada and one from Mexico attended. We had two Spanish language writers – the one from Mexico and one from a southern California university. We will be repeating this workshop for a new audience, the National Association of Science Writers who will be having their annual meeting at Stanford University in October 2008. By taking advantage of the professional organizations we are able to attract a more diverse audience from news agencies of all types.

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Abstracts of Poster Presentations(in alphabetical order by first author)

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Role of Microbes in Attenuation and Mobilization of Arsenic at the Lava Cap Mine Superfund Site,

Nevada County, CA

Andréa L. Foster 1, Georges Ona-Nguema2, Kate Tufano3, and Gordon E. Brown, Jr.3

1 Geologic Division, U.S. Geological Survey, Menlo Park, CA, USA2 Institut de Minéralogie et de Physique des Milieux Condensés, UMR 7590,

CNRS and IPGP, Paris, France3 Surface and Aqueous Geochemistry Group, Dept. of Geological & Environmental Sciences,

Stanford University, Stanford CA 94305-2115, USA

The Lava Cap Mine Site (LCMS) is typical of hundreds of low-sulfide, quartz-vein hosted gold deposits in the Sierra foothills of CA in that primary iron sulfides (pyrite, arsenopyrite) contain up to several weight percent arsenic (As). Ore extraction generated solid waste (tailings) typically containing one half to several thousand parts per million As. Minimizing transformation of As from solid phase species in the tailings to dissolved, inorganic species that can be transported in waters is the primary challenge facing the management of historically-mined sites of this type.

Mine adit waters from these types of deposits are characterized by near-neutral pH, low dissolved oxygen, and relatively high concentrations of dissolved iron (Fe) and As produced by oxidation of the primary sulfide minerals. We have documented, that sheath forming bacteria of the genus Leptothrix reduce dissolved As and Fe concentrations in tributaries receiving mine adit waters via precipitation of Fe oxyhydroxide on their sheaths. Arsenic sorbed to this biogenic iron oxyhydroxide is very similar to As sorbed to chemically-precipitated Fe oxyhydroxide. Monitoring the performance of a naturally-occurring, passive Leptothrix bioreactor shows that it is effective for removal of As, Fe, and Mn from surface waters. However, deposition of the same material under sub- to anoxic conditions (as could occur after its transport by seasonal rain events) could effect the remobilization of As due to the action of several types of bacteria. Our presentation will include quantification and speciation of As in water, tailings, and Leptothrix-dominated colonies. In addition, we will present culture-based and genetic-based characterization of of iron-reducing, arsenic-reducing, and sulfate-reducing microbial communities that have the potential to mobilize As from the site.

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Experimental Evidence for the Existence of Density Heterogeneities

on a Nanometer Scale in Ambient Water Congcong Huang1, K. T. Wikfeldt2, T. Tokushima3, D. Nordlund1, Y. Harada3,

U. Bergmann1, M. Niebuhr1, T. Weiss1, M. Leetmaa2, M. P. Ljungberg2, A. Giertz5, L. Ojamäe5,

O. Takahashi4, S. Shin1,6, L. G. M. Pettersson2, and A. Nilsson1

1 Stanford Synchrotron Radiation Laboratory, P.O.B. 20450, Stanford, CA 94309, USA

2 FYSIKUM, Stockholm University, AlbaNova, S-10691 Stockholm, Sweden.3 RIKEN/SPring-8, Sayo-cho, Sayo, Hyogo 679-5148, Japan

4 Department of Chemistry, Hiroshima University, Higashi-Hiroshima 739-8526, Japan

5 Department of Chemistry, Linköping University6 Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwanoha,

Kashiwa, Chiba 277-8581, Japan

Liquid water shows many anomalies in its thermodynamic properties

such as compressibility, density variation and heat capacity [1, 2]. In the low-temperature regime, below the freezing point, these properties deviate particularly strongly from a normal liquid. Several theories have been proposed to account for the behavior related to either a stability limit conjecture [3] or to the presence of a second critical point associated with the coexistence curve separating two states of the liquid: low density and high density water [4]. However, also a singularity free scenario based on a percolation picture has been suggested [5, 6]. Other two-state models of water, not necessarily related to the existence of a thermodynamic singularity below the melting point of ice, have also been proposed based on coexistence of low density-low entropy and high density-high entropy forms of water [7, 8]. Although the anomalies are extreme in the supercooled region they are also present at ambient conditions where most of waters physical, chemical and biological processes occur. Here we report, using a combination of small angle x-ray scattering, x-ray emission spectroscopy and x-ray Raman scattering measurements, the presence of density inhomogeneities on a dimension of 1-2 nm in ambient water caused by two distinct different structural motifs. These correspond to low density – low energy tetrahedral and high density – high energy highly hydrogen-bond distorted motifs which interconvert in population with temperature without appearance of intermediate structures. The structure and dimension of the tetrahedral component are independent of temperature whereas the structure of the high density component changes continuously with temperature. This leads to a higher density and smaller energy difference

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between the two motifs at lower temperatures. The present results show that many of the anticipated more extreme differences in the hydrogen bonding environments in the supercooled regime remain at ambient conditions up to temperatures where water starts to follow normal thermodynamic liquid behavior. [1] P. G. Debenedetti, J. Phys.: Condens. Matter 15, R 1669 (2003). [2] O. Mishima et al., Nature 396, 329 (1998). [3] R. J. Speedy, J. Phys. Chem. 86, 982 (1982). [4] P. H. Poole et al., Nature 360, 324 (1992). [5] S. Sastry et al. Phys. Rev. E 53, 6144 (1996). [6] H. E. Stanley et al., J. Chem. Phys. 73, 3404 (1980). [7] H. Tanaka, J. Chem. Phys. 112, 799 (2000). [8] M. Vedamuthu, J. Phys. Chem. 98, 2222 (1994).

An Indication of Crossover in the Dependence of Hydrophobic Solvation on Solute Size by X-ray Absorption Spectroscopy

Ningdong Huang, Dennis Nordlund, and Anders Nilsson

Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd., Menlo Park, CA 94025

Like many other facts of nature, the low solubility of nonpolar molecules (such as hydrocarbon liquids) in water is easy to observe but unexpectedly difficult to explain. Sufficiently large molecules with one polar group, here for example tetra-alkyl ammonium bromides, exhibiting the thermodynamics behavior expected from hydrophobic effects are used as model systems for study on effects of hydrophobic molecules on the hydrogen bonding network in aqueous solution. Near-edge fine structure x-ray absorption (XAS), or denoted NEXAFS, with sensitivity to the chemical environment, bond lengths and bond angles investigates local bonding configurations in the first shell of liquid water. We show XAS studies on hydrophobic effects in aqueous solutions of tetra-alkyl ammonium bromides.

At low concentrations, neither tetra-butyl ammonium bromide (TBAB) with longer hydrocarbon chains nor tetra-methyl ammonium bromide (TMAB) with small methyl groups shows obvious impact on the structure of hydrogen bonding network in bulk water. However at high concentration with the same ratio of number of hydrocarbon groups to that of water solvent molecules present in the solution, while 4M TMAB remains bulk water like; XAS indicates more broken hydrogen bonds in 1M TBAB compared to bulk water. This is some direct evidence of different interaction mechanism between bulk water and hydrophobic molecules with different sizes since TBAB and TMAB have similar structures and differ mainly in the length of hydrocarbon chains.

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EXAFS of Frozen Elemental Mercury and Its Implications for Abandoned Mercury Mine Wastes

Adam D. Jew1, Chris S. Kim2, James J. Rytuba3, Mae S. Gustin4, and Gordon E. Brown Jr.1,5

1Surface & Aqueous Geochemistry Group, Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA

2Department of Chemistry, Chapman University, One University Drive, Orange, CA 92866, USA3Geologic Division, United States Geological Survey, 345 Middlefield Road,

Menlo Park, CA 94025, USA4Department of Environmental and Resources Sciences, University of Nevada-Reno,

Reno, NV 89557, USA5Stanford Synchrotron Radiation Laboratory, SLAC, 2545 Sand Hill Road, MS 69,

Menlo Park, CA 94025, USA

Mercury in the environment is a large concern from both ecosystem and human health perspectives. Mine wastes at inoperable mercury mines throughout California can be highly elevated in mercury concentration, with some materials having mercury concentrations above 2% wt. It is of prime importance to know the speciation of Hg within these sediments to gauge potential bioavailability of Hg from these impacted areas of California. In order to assess Hg speciation within impacted sediments, Hg EXAFS studies have previously been conducted at room temperature. However, elemental Hg at room temperature is a liquid, which results in very little structure in the EXAFS region, thus making it difficult to determine relative proportions of elemental Hg in sediments. Hg LIII EXAFS of Hg mine wastes previously analyzed at room temperature were re-analyzed at 77K to determine what proportion of the Hg speciation consists of elemental Hg. By using least squares fitting it is shown that some Hg impacted mine wastes contain up to 25% elemental Hg. The same sediment samples used in the frozen EXAFS studies were also used in measuring the flux of Hg leaving the sediments during both light and dark exposures. Ratios between light and dark exposures for Hg fluxes, when normalized to concentration, showed some samples having nearly 60 times more Hg released when exposed to light versus the dark. The light/dark ratios of the mine sediments did not relate to overall Hg concentrations and could not be explained by Hg speciation determined from room temperature EXAFS. By doing EXAFS at 77K we see that there is a correlation between Hg light:dark fluxes and percentages of elemental Hg, with higher ratios correlating with higher Hgo percentages. Sediment samples with light:dark ≤4 show no evidence of elemental Hg from EXAFS, while samples that show ratios at nearly 60 contained ~25% elemental Hg. This research illustrates that a significant species of Hg has been neglected from the overall Hg speciation in environmental samples. The correlation between elemental Hg and light:dark fluxes should allow researchers to determine which mine wastes have the highest possibility of gaseous Hg emissions into the surrounding environment. In order to accurately determine speciation of Hg within sediments by EXAFS cryostat temperatures are needed and a rethinking of previous work on Hg speciation in the environment needs to be done.

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Dissociative and Molecular Adsorption of Water on the Magnetite (111) Surface Studied with High Pressure Photoemission

Tom Kendelewicz1, Susumu Yamamoto2, Hendrik Bluhm3, Anders Nilsson2, and Gordon E. Brown, Jr.1,2

1 Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 94305-2115

2 Stanford Synchrotron Radiation Laboratory, SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025

3 Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA

The reaction of water with solid surfaces is of the utmost importance in all areas of science and engineering. Recently developed high-pressure photoemission spectroscopy (HPPES) provides the unique possibility of extending the great analytical power of XPS to environmentally, technologically and biologically relevant water pressures [1].

Here we present results of a study of the reaction of water with clean and air exposed (111) surfaces of magnetite at pressures of up to 1 Torr and relative humidities (RH) up to 100%. The tunable synchrotron radiation source allows measurement of all relevant electronic levels (O 1s, Fe 2p, C 1s, valence band) at similar kinetic energies, which results in the same probing depth. Iron oxides and hydroxides, including magnetite, are among the most abundant materials at Earth’s surface and thus they are important sobents of toxic metals in aqueous environments. In addition they are widely used as catalysts or catalyst supports. Several UHV photoemission studies of the reaction of water vapour with pristine, in-vacuum cleaned or epitaxally grown, (111) surfaces of magnetite have been reported [2-6]. These studies have provided a basis for conceptual models and theoretical calculations on idealized oxide/hydroxyl/water interface. However, real world interfaces always contain some adventitious carbon. It is therefore important to consider the role of this contaminant in reactions involving water. For this reason we conducted a parallel study on UHV prepared surfaces and on similarly prepared surfaces which, before exposure to high water doses, were intentionally exposed to air.

To bridge the pressure gap our results are compared with earlier studies in which water (ice) condensation was achieved at low pressures (pH2O ~10-7) and cryogenic temperatures [2,3,4]. We find that for clean magnetite surfaces initial hydroxylation is limited to sub-monolayer quantities of hydroxyl species. At room temperatures the onset of strong hydroxylation is observed above 10-4 Torr and hydroxyl formation saturates at below ~1 Torr (4% RH). The hydroxylation step is followed by the uptake of molecular water, which continues and extends to several layers for higher relative humidities. These steps resemble the behaviour observed at lower water pressures when temperature is systematically lowered to cryogenic values. Hydroxylation of clean magnetite is often heterogeneous with some areas showing negligible effects; depending on Fe/O ratio. The O 1s chemical shift of hydroxyl species varies between 1.1 and 1.5 eV. These values are much smaller than the ~2.1-2.4 eV universally accepted for this interface in prior XPS studies [2,4,6], but they agree well with chemical shifts reported for model iron oxyhydroxides, like goethite. The O 1s chemical shift of molecular water varies from 3 to 3.3 eV.

For surfaces pre-exposed to air and therefore coated in part by adventitious carbon, hydroxylation on order of a monolayer is independent of air pre-exposure time which varies from

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minutes to weeks and the surfaces appear to be quickly passivated. No further increase in hydroxyl coverage occurs for water exposure up to RH of 100%. For clean magnetite (111) surfaces the results are very similar with the exception that the intensity from the hydroxyl species, which remain constant on air exposed sample increases with RH up to ~4% and then remains constant for further hydration and dehydration.

References[1] D. F. Ogletree, H. Bluhm, G. Lebedev, C. S. Fadley, Z. Husain, and M. Salmeron, Rev. Sci.

Instrum. 73, 3872 (2002).[2] R. S. Cutting, C. A. Muryn, D. J. Vaughan, and G. Thornton, Surf. Sci. 602, 1155 (2008).[3] Y. Joseph, C. Kuhrs, W. Ranke, and W. Weiss, Surf. Sci. 433-435, 114 (1999).[4] Y. Joseph, W. Ranke, and W. Weiss, J. Phys. Chem. 104, 3224 (2000).[5] Y. Joseph, C. Kuhrs, W. Ranke, M. Ritter, and W. Weiss, Chem. Phys. Lett. 314, 195 (2000).[6] T. Kendelewicz, P. Liu, C. S. Doyle, G. E. Brown Jr., E. J. Nelson, and S. A. Chambers, Surf.

Sci. 453, 32 (2000).

Diffraction and IR/Raman Data Do Not Prove Tetrahedral Water

Mikael Leetmaa1, Kjartan Thor Wikfeldt1, Mathias P. Ljungberg1, Michael Odelius1, Jan Swenson2, Anders Nilsson1,3, and Lars G.M. Pettersson1*

1FYSIKUM, Stockholm University, AlbaNova University Center, SE-106 91, Stockholm, Sweden

2 Dept. Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden3Stanford Synchrotron Radiation Laboratory, P.O.B. 20450, Stanford, CA 94309, USA

We use the reverse Monte Carlo (RMC) modeling technique to generate two extreme water models that both reproduce available x-ray and neutron diffraction data as well as the electric field distribution as a representation of the OH-stretch Raman spectrum of liquid water with internal geometries following a quantum distribution. Forcing the fit to maximize the number of hydrogen (H-) bonds results in a tetrahedral model with 74% double H-bond donors (DD) and 21% single donors (SD). Maximizing instead the number of SD species gives 81% SD and 18% DD, while still reproducing the experimental data and losing only 0.7-1.8 kJ/mole interaction energy. By decomposing the simulated Raman spectrum we can relate the models to the observed ultra-fast frequency shifts in recent pump-probe measurements. Within the tetrahedral DD model the assumed connection between spectrum position and H-bonding indicates ultra-fast dynamics in terms of breaking and reforming H-bonds while in the strongly distorted model the observed frequency shifts do not necessarily imply H-bond changes. Both pictures are equally valid based on present diffraction and vibrational experimental data. There is thus no strict proof of tetrahedral water based on these methods. We also note that the tetrahedral model must, to fit diffraction data, be less structured than most models obtained from molecular dynamics simulations.

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Development of Arsenic and Iron Biogeochemical Gradients Upon Anaerobiosis at Soil Aggregate Scale

Yoko Masue-Slowey, Celine Pallud, Kate Tufano, Paul Bedore, and Scott Fendorf

Department of Environmental Earth Systems ScienceStanford University, Stanford, CA 94305

In aerated soils, As release is limited due to the strong interaction between As(V) and soil minerals. However, under anaerobic conditions, As desorption is stimulated by As(V) reduction to As(III) and reductive dissolution/transformation of Fe (hydr)oxides, common hosts of As. The effect of As(V) and Fe(III) reduction on As release has been extensively studied in laboratory batch and column systems; correlation of apparent Fe and As reduction, with concomitant release to pore water, has also been noted under field conditions. What remains unresolved is the coupling of biogeochemical and physical processes that ultimately control As transport within structured media such as soils. Soils are heterogeneous porous media that are comprised of individual aggregates having pores that are dominated by diffusive (aggregate interiors) or advective (aggregate exteriors) transport. As a consequence of physical and chemical differences in the interior and the exterior of aggregates, As(III,V) and Fe(II,III) chemical gradients develop. Here, we examine As release from constructed aggregates exposed to fluctuating redox conditions.

Artificial aggregates were made with As(V) adsorbed ferrihydrite-coated sand homogeneously inoculated with Shewanella sp. ANA-3 (model As(V) and Fe(III) reducer) and then fused using an agarose binder into spheres. Aggregates were placed in a flow reactor and saturated flow of aerobic or anaerobic artificial groundwater media was initiated. Redox fluctuated in select systems to examine changes in chemical gradient under changing aeration status.

Our results show that within aerated solutions, oxidized aggregate exteriors provide a “protective barrier” against As release despite anoxia within diffusively constrained aggregate interiors. During a transition to anaerobic conditions in advective zones, however, As is release and transport is promoted. Our study illustrates the microscale variation in biogeoechemical processes within soils and the importance of appreciating the spatial connection between reaction and transport fronts.

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Stability, Electronic and Magnetic Properties of Iron Oxy-hydroxides Under High Pressure: Insights from First Principles

Katrin M. Otte1, Rossitza Pentcheva1, and James R. Rustad2

1Section of Crystallography, Department of Earth and Environmental Sciences, University of Munich, Munich, Germany

2Geology Department, U.C. Davis, Davis, CA

Iron oxyhydroxides (FeOOH) play an important role in water treatment (e.g. in the binding of heavy metals and arsenic complexes), as inorganic pigments, and in magnetic recording. The high pressure behavior of water containing minerals is important for understanding the processes in the Earth's crust and lower mantle. Using density functional theory (DFT), we investigate the energetic, electronic, and magnetic properties of the iron oxyhydroxide-polymorphs (a-, -, g- and hp-FeOOH) under hydrostatic pressure. We find that at ambient conditions goethite (a) is the lowest energy phase, consistent with recent calorimetric measurements [1]. A transformation from the a- to the hp-phase is predicted at 9GPa, accompanied by a high-spin to low-spin transition [2]. While in the ground state Fe3+-ions are coupled antiferromagnetically, at high pressures a transition to a ferromagnetic alignment is found in hp-FeOOH. At ambient conditions all AFM phases are insulating within the generalized gradient approximation (GGA). However, a substantial improvement of the size of the band gap and a transition to a charge transfer type is achieved by including on-site Coulomb repulsion within the LDA(GGA)+U method [3]. Bond lengths are in a good agreement with available experimental data [4].

[1] Laberty and Navrotsky, Geochim. Cosmochim. Acta 62, 2905-2913 (1998).[2] K. Otte, R. Pentcheva, W.W. Schmahl, and J. R. Rustad, Earth Planet. Sci. Lett., submitted.[3] Anisimov et al., Phys. Rev. B 48, 16929 (1993).[4] Nagai et al., Am. Mineral. 88 1423 (2003).

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Water Adsorption on Fe3O4(001): Insights from First Principles

N. Mulakaluri1, R. Pentcheva1, W. Moritz1 und M. Scheffler2

1Department of Earth and Environmental Sciences, Section Crystallography,University of Munich, Munich, Germany

2Fritz-Haber-Institut of the MPG, Berlin, Germany

The interaction of water with a mineral surface is a fundamental process both in nature and technology. We study the influence of water adsorption on the energetics and properties of the Fe3O4(001) surface using density functional theory (DFT)-calculations with the FPLAPW method in the WIEN2k implementation. Furthermore we investigate the mode of adsorption of water (dissociative versus molecular) on the Fe3O4(001)-surface. We vary the concentration and orientation of water and hydroxyl groups starting from a single water molecule per (√2 ×√2)R45˚ unit cell and compare the surface stability of the different terminations as a function of the O2

and H2O pressure within the framework of ab-initio thermodynamics [1]. While for oxygen and water poor conditions a clean Jahn-Teller distorted bulk termination is stabilized (modified B-layer) [2,3], with increasing water pressure a water monomer parallel to the surface and, finally, a B-layer covered with four water molecules in a flat orientation is stabilized. The DFT-calculations give indications of a lifting of the (√2 × √2)R45o-reconstruction, consistent with low energy electron diffraction (LEED) measurements.

[1] X.-G. Wang et al., Phys. Rev. Lett. 81, 1038 (1998); K. Reuter and M. Scheffler, Phys. Rev. B 65, 035406 (2002).

[2] R. Pentcheva, F. Wendler, N. Jedrecy, H.L. Meyerheim, W. Moritz, and M. Scheffler, Phys. Rev. Lett. 94, 126101 (2005).

[3] R. Pentcheva, J. Rundgren, W. Moritz, S. Frank, D. Schrupp, und M. Scheffler, Surf. Sci., 602, 1299 (2008).

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Arsenic Release from Near-Surface Sediments to GroundwaterSustaining Asian Mass Poisoning

Matthew L. Polizzotto1 and Scott Fendorf2

1 Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 2 Department of Environmental Earth Systems Science, Stanford University, Stanford, CA

Tens of millions of people in South and Southeast Asia routinely consume groundwater with unsafe arsenic levels. Arsenic is naturally derived from eroded Himalayan sediments and is believed to enter solution following reductive release from solid phases under anaerobic conditions. However, the processes governing aqueous concentrations and location of arsenic release to pore water remain unresolved, limiting our ability to predict arsenic concentrations in space (between wells) and time (future concentrations) and to assess the impact of human activities on the arsenic problem. This uncertainty is partly attributed to a poor understanding of groundwater flow paths altered by extensive irrigation pumping in the Ganges-Brahmaputra Delta, where most research has focused. Here, using hydrologic and (bio)geochemical measurements, we show that on the minimally-disturbed Mekong Delta of Cambodia, arsenic is released from near-surface, river-derived sediments and transported, on a centurial time scale, through the underlying aquifer back to the river. Owing to similarities in geologic deposition, aquifer source rock, and regional hydrological gradients, our results represent a model for understanding pre-disturbance conditions for other major deltas of Asia. Furthermore, the observation of strong hydrologic influence on arsenic behavior indicates that release and transport of arsenic are sensitive to ongoing and impending anthropogenic disturbances. In particular, groundwater pumping for irrigation, changes in agricultural practices, sediment excavation, levee construction, and upstream dam installations will alter the hydraulic regime and/or arsenic source material and, by extension, influence groundwater arsenic concentrations and the future of this massive health crisis.

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Mercury Accumulation and Retention by Plants at the Abandoned New Idria Mine Site: A Preliminary µXRF Study

Hagar Siebner1, Gordon E. Brown, Jr.1,2, and Samuel Webb2

1 Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 94305-2115

2 Stanford Synchrotron Radiation Laboratory, SLAC, MS 69, 2575 Sand Hill Road, Menlo Park, CA 94025

Due to its high toxicity and increasing levels of exposure of life systems, mercury pollution became a serious global problem. A lot of research has been conducted with regard to Hg bio-cycles in aquatic systems. Much less is known about terrestrial Hg-cycles in general and in plants specifically. Plants takes an important part in Hg cycles; they are known to be an important sink for both atmospheric and soil Hg, the vegetation cover significantly influence soil erosion and migration of contaminants into aquatic systems. However, the mechanisms involved in interactions of Hg with plants and plants products are poorly studied. Information concerning interaction of Hg in plants at the molecular level is sparse. The presented study is intended to elaborate Hg retention, translocation and accumulation in these plants.

We have identified few plants species in the abandoned Hg mine site of New Idria, which were adapted to the hostile environment and according to the literature are able to accumulate high level of Hg either in their upper or lower parts.

We present here preliminary results of mercury distribution in roots and leaves samples taken from two different plants species growing in the New-Idria sites. Sampled were taken at two different locations; the mine adit and the acid drainage pond below it. Distribution appeared to be affected by plant species, growing conditions and developmental stage.

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Uranyl-Chlorite Sorption/Desorption: Evaluation of Different Sequestration Mechanisms

David M. Singer1, Kate Maher1, and Gordon E. Brown, Jr.1,2

1 Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, CA 94305-2115, USA

2 Stanford Synchrotron Radiation Laboratory, SLAC, MS 69, 2575 Sand Hill Road, Menlo Park, CA 94025, USA

Sequestration of soluble uranium (U) by clay minerals is a potentially major sink for U in contaminated environments. We have used a series of batch sorption/desorption experiments combined with U LIII-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy to investigate the dominant sorption mechanism(s) governing uranyl uptake by chlorite. U uptake was measured as function of ionic strength (0.001 to 0.1 M NaCl), pH (at pH 4, 6.5, and 10), and solution composition (over the U(VI) concentration range of 1x10-5 M to 1x10-6 M, and in the presence or absence of 2.5x10-4 M CO3 and Ca). Sorption was independent of ionic strength, suggesting a dominantly inner-sphere sorption mechanism. The maximum sorption loading was 0.28 moles U g-1 chlorite at pH 4, whereas the maximum sorption loading was 6.3 moles U g-1 chlorite pH 6.5 and pH 10. At pH 6.5, U(VI) uptake as a function of solution chemistry followed the trend CO3-Ca-free system > CO3-Ca-bearing system > CO3-bearing system. Conversely at pH 10, U(VI) uptake as a function of solution chemistry followed the trend CO3-Ca-bearing system > CO3-Ca-free system CO3-bearing system. A desorption experiment performed as a series of sequential extraction steps indicated that: (1) there was little to no weakly bound U(VI) or U(VI) coprecipitated with ferrihydrite, and (2) U(VI) inner-sphere sorption complexes are desorbed by 60-80% with 0.1 M HCl within one week, and 100% desorption is accomplished with 1.0 M HCl. Fits of the U LIII-edge EXAFS spectra of the sorption samples indicate that U(VI) forms inner-sphere sorption complexes at [Fe(O,OH)6] octahedral sites in a bidentate manner. When CO3 and Ca were included, the EXAFS spectra fits indicate that U(VI)-CO3 sorption complexes were present, although there was no evidence for U(VI)-CO3-Ca sorption complexes. The EXAFS-derived parameters were used to constrain the type(s) of U(VI)-bearing surface species and combined with the observed batch sorption trends as input for a surface complexation model (SCM) to evaluate the relationships between aqueous U(VI) speciation and surface species. The model successfully predicts U(VI) sorption in the CO3-Ca-free and CO3-bearing system, but under-predicts U(VI) sorption by up to 30% in the CO3-Ca-bearing system. Long-term exposure of chlorite to U(VI) to promote ferrihydrite formation or reduction of U(VI) by Fe(II) was performed under anaerobic conditions to determine the role these uptake mechanisms might play. Although there was no evidence for the formation of ferrihydrite, the U L III-edge XANES spectra of these samples indicated the presence of 25% U(IV), whereas no U(IV) was detected for the sorption samples. An additional contribution to the EXAFS spectra was observed, with corresponding Fourier transform peak at ~ 3.8 Å, that is consistent with the U-U pair correlation in uraninite. Surprisingly, the presence of Ca in solution prohibited U(VI) reduction. These results suggest that long-term exposure of chlorite to uranyl could result in U sequestration as the relatively insoluble UO2, versus more transient sorption complexes. The results presented in this study can aid surface complexation models of uranyl sorption on clay minerals by accounting for the change in sorption mechanisms as a function of solution chemistry.

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Modeling the Interaction of UO22+ with Corundum and Hematite Surfaces

Mary T. Van der Hoven1, Shela Aboud2, Jennifer Wilcox2, Michael Odelius3, and Gordon E. Brown, Jr.1,3

1 Surface and Aqueous Geochemistry Group, Department of Geological & Environmental Sciences, Stanford University, Stanford CA 94305-2115, USA

2 Department of Energy Resources Engineering, Stanford University, Stanford, CA, USA3 FYSIKUM, AlbaNova University Center, Stockholm University, S-106 91 Stockholm, Sweden

4 Stanford Synchrotron Radiation Laboratory, Menlo Park, CA 94025, USA

Uranyl (UO22+) is a common contaminant in soil and groundwater at nuclear facilities and at

uranium mining sites. However, its binding to the surfaces of common soil and aquifer materials is not well understood at the molecular scale. Quantum Mechanical (QM) modeling is a useful tool in providing insight into the molecular-level details of such interactions. The model used to simulate a system is undoubtedly the most important factor in the usefulness of QM investigations. Data from QM calculations on small cluster models of the hydrated corundum and hematite (1-102) surfaces (using Gaussian 03) and from QM calculations on slab models with periodic boundary conditions (using VASP) will be compared to existing experimental data. Density of states and charge distribution data from VASP calculations will also be presented and used to explain the differing observed mode of uranyl binding on the two minerals. Future work will use the refined QM models to understand the effect that citrate has on the binding of uranyl on corundum or hematite.

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X-ray Absorption Spectroscopy of Alkali Fluoride Solutions Ira Waluyo1, Dennis Nordlund1, Uwe Bergmann1, Lars G. M. Pettersson2, and Anders Nilsson1

1 Stanford Synchrotron Radiation Laboratory, SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025, USA

2 Department of Physics, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden

Ions are traditionally categorized into structure-breakers and structure-makers based on the strength of their interaction with water. However, this classification is ambiguous and based on macroscopic properties, offering no structural details of the water-ion interaction. X-ray absorption spectroscopy (XAS) is a powerful tool for studying the nature of the interaction between water molecules and ions due to its elemental specificity and sensitivity to the orbitals involved in hydrogen-bonding. We present XAS studies of alkali fluoride solutions in water, where the fluoride anion is generally recognized to be a strong structure-making ion that form strong interaction with water molecules.

Our results show that O 1s XAS spectra of water in low concentration alkali fluoride solutions (i.e. 1 m NaF, KF, and CsF) display no significant differences from the spectrum of bulk water, which is unexpected considering the strong interaction between fluoride and water. This is contrasted to the spectra of NaCl and KCl solutions, which at 1 m concentration already show changes from the bulk water spectrum. Our studies also show that the cations, which are generally regarded as weakly interacting with water, play an important role in the structuring of water in these solutions, especially at higher concentrations. O 1s XAS spectrum of 8 m KF solution resembles that of bulk water, except for a shift to higher energy related to the change in hydrogen bonding length, while the spectrum of 8 m CsF solution shows ice-like spectral features. Similarly, F 1s XAS spectra show considerable changes at higher concentrations of CsF compared to KF.

These data suggest that the nature of the interaction between ions and water is more complicated than simple structure-making and structure-breaking properties and that there are many factors, such as concentration and size of the cations, that can result in changes in the hydrogen-bonding network of water as well as the electronic structure.

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Parameters Controlling the Partitioning of Trace Metal(loid)s at the Shewanella oneidensis MR-1 Biofilm/Mineral/Water Interface

Yingge Wang1, Alexandre Gélabert1, Yong Choi2, Juyoung Ha1, Johannes Gescher3, John R. Bargar4, Joe Rogers4, Peter J. Eng4, Carmen Cordova3, Sanjit K. Ghose2,

Georges Ona-Nguema5, Alfred M. Spormann3, and Gordon E. Brown, Jr.1,4

1 Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 94305, USA

2 GSECARS, University of Chicago, Chicago, IL 60637, USA3 Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA

4 Stanford Synchrotron Radiation Laboratory, SLAC, Menlo Park, CA 94025, USA5 Institut de Minéralogie et de Physique des Milieux Condensés, UMR 7590, CNRS and IPGP,

Paris, France

Surface-attached microbial communities known as microbial biofilms are ubiquitous in natural environments. They are often present as coatings on mineral surfaces in soils and aquatic systems. Compared to bare mineral surfaces, these complex bacterial communities can induce significant changes in surface properties of minerals and sorption capacities for metal(loid) ions. However, such effects are still poorly understood at a molecular level due to the complex nature of these systems and the lack of appropriate tools to accurately probe such interfaces. In this study, long-period X-ray standing wave-florescence yield (XSW-FY) spectroscopy was used to measure in-situ partitioning of trace metal(loid) ions at S. oneidensis MR-1 biofilms- coated a-alumina (0001) and, (1-102) and hematite (0001) single crystal surfaces as a function of metal concentration, exposure time, and pH. The competitive sorption effects among various metal ions were also probed by simultaneously exposing biofilm/mineral interfaces to different trace elements simultaneously. To complement the in-situ XSW-FY measurements, grazing incidence X-ray adsorption fine structure (GI-XAFS) spectroscopic measurements at specific x-ray incidence angles were performed to probe ion speciation and local coordination environment at the mineral surfaces and in the biofilm. In addition, a number of surface characterization techniques including X-ray Photoemission Spectroscopy (XPS), X-ray reflectivity, atomic force microscopy (AFM), Electrokinetic analyzer (EKA), and confocal laser scanning microscopy (CLSM) have been applied to study the properties of clean and biofilm- coated mineral surfaces.

S. oneidensis MR-1 biofilm, a facultative gram-negative bacterium, were was grown on clean single crystal surfaces aerobically (10 days) and anaerobically (20 days) under flow-through conditions using minimal defined media and pyruvate as a carbon and energy source. Aqueous metal ions Pb(II) and Zn(II) XSW-FY partitioning profiles at biofilm coated hematite (0001) surfaces under aerobic conditions with concentrations ranging from 10-4M to 10-7 M at pH 6.0 showed that metal ions are preferentially sorbed at mineral surfaces at low concentrations (≤ 10e-6 M) and are increasingly partitioned into biofilms at higher concentrations (> 10e-6 M). However, most of As(V) sorbed at hematite (0001) surfaces for anaerobically grown S. oneidensis biofilm even at high concentration (10-

3M) and various exposure times (3-40 hrs) at pH 7.0. These results confirm that biofilms do not change the intrinsic reactivites of mineral surfaces, ; and instead they provide more sorption sites for metal(loid) ions. Hematite (0001) was found to be the most reactive surface for metal sorption at these complex interfaces followed by a-alumina (1-102) and a-alumina (0001). Significant changes in metal ion XSW-FY profiles at different exposure times (30 minutes, 3 hours, and 1 day) on fresh samples suggest the

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existence of diffusion limited processes occurring at the biofilm/mineral interface. Multiple metal ions partitioning at biofilm/mineral interfaces showed that at higher concentrations (>10e-5M -5 at pH 6.0 and 3 hours of exposure) there are no apparent competitive effects among Pb(II), Zn(II), and other metal ions including Cu(II), Co(II) and Ni(II). However, at lower metal concentrations (≤10-6M), longer exposure time (24 hrs), and with in the presence of additional metal ions, Zn(II) outcompete Pb(II) for metal oxide surface sites. GI-XAFS analysis of Pb(II) at S. oneidensis MR-1 biofilm- coated hematite surfaces indicate that carboxyl groups are responsible for Pb(II) complexation in the biofilm after 3 hours of exposure at pH 6, and no evidence of biomineralization have has been found under the tested conditions. The results of this study will provide new insights about the factors controlling trace element partitioning and speciation at complex microbe-mineral interfaces and an improved understanding of the nature of local microenvironments created by the microbial biofilm at mineral surfaces.

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Water Adsorption on a-Fe2O3(0001) at Near Ambient Conditions

Susumu Yamamoto1, Tom Kendelewicz2, John T. Newberg3, Guido Ketteler4, David E. Starr3, Erin R. Mysak3, Klas Andersson1, Hirohito Ogasawara1, Hendrik Bluhm3, Miquel Salmeron4,

Gordon E. Brown, Jr.1, 2, and Anders Nilsson1

1Stanford Synchrotron Radiation Laboratory, Stanford University, Menlo Park, CA 940252Department of Geological and Environmental Sciences, Stanford University,

Stanford, CA 943053Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 947204Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720

Chemical reactions on iron oxide surfaces are of key importance in environmental, geological, and technological systems. Under ambient conditions where most of important environmental and technological processes occur, oxide surfaces react with water and become partially covered with molecular H2O and/or its dissociated species of OH. It is well known that the presence of water on surfaces has a significant influence on the mechanisms and kinetics of surface chemical reactions. A detailed understanding of in situ surface compositions of iron oxides under ambient conditions is therefore essential for a thorough comprehension of important roles of iron oxides in the environmental and technological processes.

Here we have investigated the hydroxylation and water adsorption processes on the (0001) surface of hematite (a-Fe2O3) at near ambient conditions, using an ambient pressure photoelectron spectroscopy (AP-PES) setup at beamline 11.0.2 of Advanced Light Source (ALS). The experiments were performed at near ambient conditions of pressure (p(H2O)< 2 Torr) and temperature (T= 277~570 K), which corresponds to relative humidities of up to 33 %.

On the a-Fe2O3(0001) surface, the hydroxylation precedes water adsorption and already occurs at the very low relative humidity (RH) of ~1x10-7 % (i.e., p(H2O)~ 2x10-8 Torr at 295 K). As the RH is increased either by increasing water pressure at a constant temperature (isotherm) or by decreasing a sample temperature at a constant water pressure (isobar), the coverage of OH increases slowly between 1x10-7 and ~10-3 % RH. Above ~10-3 % RH, the OH coverage increases slightly more rapidly and approaches 1 monolayer (ML) at the maximum RH of 33 %. The depth profiling experiment by variation of incident photon energy demonstrates that the hydroxylation occurs only at the topmost surface.

The onset of water adsorption is varied from 1x10-6 % to 2.5x10-2 % RH depending on the sample temperature and water pressure. In the uptake curve of water, the inflection point is observed close to 1 ML, which may indicate the layer-by-layer growth of water on the hydroxylated a-Fe2O3(0001) surface. Accompanied with the continuous increase in the coverages of OH and H2O on the surface at higher RHs, the following characteristic changes are observed in the O 1s PES features: (1) the position of OH peak shifts to lower binding energies by ~0.2 eV, (2) the width of oxide peak decreases by ~0.3 eV. The possible origins of these changes in O 1s PES spectra at high RHs will be discussed.

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Study of Iodide Adsorption on Organobentonite using X-ray Absorption Spectroscopy and X-ray Diffraction

J ihae Y oon 1,2, Juyoung Ha1, Gordon E. Brown, Jr.1,3, Jinyeon Hwang2

1 Department of Geological & Environmental Science, Stanford University, Stanford, CA 94305-2115, USA

2 Division of Earth Environmental System, Pusan National University, Busan 609-735, Korea

3 Stanford Synchrotron Radiation Laboratory, SLAC, 2575 Sand Hill Road, MS 69, Menlo Park, CA 94025, USA

The adsorption of iodide on untreated bentonite and bentonites modified with an organic cation (i.e., hexadecylpyridinium chloride monohydrate (HDP+)), noted as organobentonite hereon, were investigated. The organobentonites and untreated bentonites were characterized using micro X-ray diffraction (-XRD) and electrophoretic mobility measurements prior to reaction with KI solutions. Based μ-XRD, the d001 spacing of untreated bentonite was 1.22 nm whereas organobentonites modified with HDP+ at different equivalent amounts corresponding to 100%, 200%, and 400% of the cation exchange capacity (CEC) of bentonite showed d001 spacing of 1.96 nm, 3.77 nm, and 3.77 nm, respectively. Our -XRD study indicates that organobentonites significantly expanded in basal spacing and organic cations were substantially intercalated into the interlayer spaces of montmorillonite. The electrophoretic mobility indicates that the untreated bentonite had a negative surface charge over the entire pH range examined (pH 2-12) whereas the organobentonite at an equivalent amount corresponding to 200% of the CEC had a positive surface charge over this pH range. We found significant differences in adsorption capacities of iodide depending on the bentonite properties as follows: iodide adsorption capacities were 439 mmol/kg for the bentonite modified with HDP+ at an equivalent amount corresponding to 200% of the CEC of bentonite whereas no adsorption of iodide was observed for the untreated bentonite. The molecular environments of iodine adsorbed on organobentonites were further studied using I K-edge and LIII-edge x-ray absorption spectroscopy (XAS). The X-ray absorption near-edge structure (XANES) of iodine spectra from organobentonites was similar to that of KI reference solution. Quantitative analysis of EXAFS spectra of organobentonite samples indicates that iodine is bound to carbon and the coordination number and interatomic distances between I–C varied depending on the organic concentration on bentonite. Linear combination fitting of EXAFS data suggests the fraction of iodine reacted with the organic compound increased from 45% to 71% with increasing loading of the organic compound on organobentonites. In this study, we observed significant differences in the adsorption environments of iodide depending on the property of the bentonite, and suggest that these molecular-level differences result in an organobentonite that has potential as reactive barrier material around a nuclear waste repository containing radioactive iodide.

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APPENDIX E. Article published in the March 24, 2009 Stanford Report on Arsenic Poisoning in Southeast Asia

Stanford Report, March 24, 2009Scientists solve puzzle of arsenic-poisoning crisis in Asia

BY CHELSEA ANNE YOUNG

Every day, more than 140 million people in southern Asia drink groundwater contaminated with arsenic. Thousands of people in Bangladesh, Cambodia, India, Myanmar and Vietnam die of cancer each year from chronic exposure to arsenic, according to the World Health Organization. Some health experts call it the biggest mass poisoning in history.

More than 15 years ago, scientists pinpointed the source of the contamination in the Himalaya Mountains, where sediments containing naturally occurring arsenic were carried downstream to heavily populated river basins below.

But one mystery remained: Instead of remaining chemically trapped in the river sediments, arsenic was somehow working its way into the groundwater more than 100 feet below the surface. Solving that mystery could have significant implications for policymakers trying to reverse the mass poisoning, said Stanford University soil scientist Scott Fendorf.

"How does the arsenic go from being in the sediment loads, in solids, into the drinking water?" said Fendorf, a professor of environmental Earth system science and a senior fellow at Stanford's Woods Institute for the Environment.

To find out, he launched a field study in Asia in 2004 with two Stanford colleagues: Chris Francis, an assistant professor of geological and environmental sciences, and Karen Seto, now at Yale University. The initial study was funded with a two-year Woods Institute Environmental Venture Projects grant. Five years later (with funding, in part, from the Stanford Environmental Molecular Science Institute provided by the National Science Foundation), the research team appears to have solved the arsenic mystery and is working with policymakers and government officials to prevent the health crisis from escalating.

"The real thing is, how do we help the people who are there?" Fendorf said. "But first, we have to understand the coupling of hydrology—the way the water is flowing—with the chemistry and biology."

Finding a study site

Arsenic-laden rocks in the Himalayas feed into four major river systems: the Mekong, Ganges-Brahmaputra, Irrawaddy and Red. Epidemiologists first identified arsenic poisoning in the 1980s in the Ganges-Brahmaputra Delta in Bangladesh. The sudden occurrence of the disease was linked to the increased use of wells for drinking water.

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Scientists had long assumed that the contamination process occurred deep underground, in buried sediments that release arsenic into aquifers 100 to 130 feet below the surface. But Fendorf and his colleagues had data suggesting otherwise. They suspected that the arsenic actually dissolved at a much higher depth, very close to the surface. "As the water starts to move down into the soil, it picks up arsenic. That was our hypothesis," he said. "We needed to follow the chemistry of the surface water as it moved down into the groundwater."

Fendorf and his colleagues began their fieldwork in the Brahmaputra River basin of Bangladesh. However, creating a hydrology model was a challenge, because the landscape was dotted with irrigation wells that alter the natural path of water. "When you draw out how the water might flow, it looks like spaghetti," Fendorf explained. "Before we even started we said there is no way this is going to be possible."

The researchers needed a less-developed site that was chemically, biologically and geologically similar to Bangladesh. The Mekong River in Cambodia offered a perfect alternative. Its headwaters are only 100 miles away from those of the Brahmaputra River. "All the chemistry up in the Himalayas is similar," Fendorf added. "The transport down the big river system is very similar as well."

More importantly, the Cambodia site was mostly undeveloped. "Cambodia had been under a 35-year civil war that had really repressed its development, so it was in essence Bangladesh 40 or 50 years ago," he said. "In some ways it would actually be setting the clock back and getting a snapshot back in time. By virtue of having this more simplistic system, we could really track the entire water flow."

Field results

The new field site was located just south of Cambodia's capital, Phnom Penh. Fendorf hired local workers to drill wells at three different depths throughout the 20-square-mile site. Testing the water for dissolved arsenic at various depths allowed the researchers to pinpoint where the toxin was migrating into the aquifer. To observe solids, they also installed water-sampling devices a foot or two below the surface. The data they collected allowed them to put together a model of arsenic cycling in the river delta.

"We found out that, sure enough, within the first 2 to 3 feet from the surface, arsenic was coming out of the solids—that is, the sediments transported down from the Himalayas—and into the water, and then it migrated down into the aquifer," Fendorf said. Aquifers are the source of drinking water for people who use wells throughout Cambodia, Bangladesh, Myanmar, India and Vietnam.

The culprits responsible for dissolving the arsenic turned out to be bacteria that live in the soil and sediment of the river basin. The researchers discovered that arsenic flowing down the river from the Himalayas sticks to rust particles called iron oxides. Upon reaching the river delta, these arsenic-laden particles are buried by several layers of soil, creating an oxygen-free, or anaerobic, environment. Normally, bacteria use oxygen to breathe. But in an anaerobic

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environment, they can use other chemicals, including rust and arsenic. As the bacteria metabolize the iron and arsenic, they convert it to a form that readily dissolves in water.

"As these sediments get buried very rapidly, the bacteria go through an anaerobic metabolism that dissolves the iron minerals and the arsenic with it," Fendorf said. "The arsenic goes into the water and the problem starts."

The results, published in the journal Nature, confirmed Fendorf's hypothesis: Arsenic contamination was occurring near the surface and, in fact, would take at least 100 years to reach the aquifer below. The Stanford team also showed that the 100-year-scale cycling of arsenic into the aquifer was a natural process that had been occurring for thousands of years, preceding any human influence. "We showed that there is a perpetual source of arsenic that replenishes from the surface," Fendorf said.

Solutions to the crisis

Understanding the area's hydrology will allow developers to strategically install wells that draw from areas free of dissolved arsenic, providing clean, drinkable water. Such targeted excavation can be extremely accurate, Fendorf said.

But what if a village needs a well but is unable to find an arsenic-free location to install it? Fendorf has proposed several solutions, including installing arsenic filters, collecting rainwater and purifying surface water. Each option has pros and cons, he said.

Filtering arsenic from well water raises the problem of how to dispose of leftover waste. "There aren't hazardous waste landfill sites," he noted. Additionally, the filter approach requires a dependable monitoring system. "If you do have a failure of the filter, how do you know when it occurs, and how are you going to be testing for that?" he asked.

Harvesting rainwater with collection tanks or rooftop gutters can be effective in certain locations and for certain people, he said. But areas with longer dry seasons require big tanks that are often too expensive. "These are areas where people are making less than $2 a day," Fendorf noted.

Another option is to use a disinfectant to purify surface water collected from ponds or rivers. The problem, he said, is that the filters have to be very cheap and easy to use. To solve the problem, Fendorf has been collaborating with Resource Development International (RDI), a non-governmental organization in Cambodia that makes affordable filters from locally discarded clay and rice hulls.

With these challenges in mind, Fendorf and Stanford post-doctoral scholar Matt Polizzotto have proposed finding the best option on a village-by-village basis. Beginning March 24, Fendorf will co-host a four-day meeting on arsenic poisoning in Siam Reap, Cambodia, with about 60 experts, including government officials, scholars, NGOs and funding agencies, such as the World Bank. The meeting was convened by the American Geophysical Union and the Woods Institute.

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"The first three days will be devoted to the arsenic groundwater problem," Fendorf said. "We hope to converge on a resolution, as a scientific body, on what we agree about the problem, what remains unresolved and what needs to be done to fill the gap. The final day of the meeting will look more holistically at the water problem, examining best options for bringing safe drinking water to the populace."

Land-use changes

According to Fendorf, the new understanding of arsenic cycling comes at a critical time for Cambodia, which is finally recovering from years of political unrest and is looking to bolster its economy by installing wells for drinking water and irrigation, and excavating soil to make roads and bricks. Such land-use changes could affect arsenic flow patterns throughout the delta, he warned, although in some cases, this may not be a bad thing. "The land-use changes will definitely modify the arsenic levels," he said. "Sometimes they might increase the level, and sometimes they might decrease it, depending on where they are situated and what the surrounding environment is like."

Although Fendorf and his colleagues came to Cambodia focused on understanding the science of arsenic contamination, they soon realized that what mattered most was the potential to make a difference in the lives of individuals. For example, the researchers tested each well they drilled for arsenic contamination. If it tested clean, they installed an additional well for domestic use and offered it to the landowner. If a well proved contaminated, the researchers would buy the landowner a rainwater-harvesting unit locally made by RDI.

"If we can give people a clean well or a rainwater harvesting unit, that's going to go a lot further, in the short term at least, than any of our study results," Fendorf said.

Chelsea Anne Young is a former science-writing intern at the Stanford News Service.

Editor's Note

Stanford scientists are co-hosting a conference on arsenic groundwater poisoning in Asia from March 24-27 in Seam Reap, Cambodia.

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Appendix F: SLAC Press Release on Research on Water by the Nilsson Group

August 11, 2009 - SLAC Researchers Reveal the Dance of WaterDate Issued: August 11, 2009

Contact:* Melinda Lee, SLAC Media and Outreach Manager: 1 (650) 926-8547, melinda.lee@slac.stanford.edu * Robert Brown, SLAC Director of Communications: 1 (650) 926-8707, robbrown@slac.stanford.edu

This artist's depiction shows two distinct structures of water: in the foreground, tetrahedral low-density water and in the background, distorted high-density water. (Image courtesy of Hirohito Ogasawara and Ningdong Huang, SLAC.)

Menlo Park, Calif.—Water is familiar to everyone—it shapes our bodies and our planet. But despite this abundance, the molecular structure of water has remained a mystery, with the substance exhibiting many strange properties that are still poorly understood. Recent work at the Department of Energy's SLAC National Accelerator Laboratory and several universities in Sweden and Japan, however, is shedding new light on water’s molecular idiosyncrasies, offering insight into its strange bulk properties.

In all, water exhibits 66 known anomalies, including a strangely varying density, large heat capacity and high surface tension.

Contrary to other "normal" liquids, which become denser as they get colder, water reaches its maximum density at about 4 degrees Celsius. Above and below this temperature, water is less dense; this is why, for example, lakes freeze from the surface down. Water also has an unusually large capacity to store heat, which stabilizes the temperature of the oceans, and a high surface tension, which allows insects to walk on water, droplets to form and trees to transport water to great height

"Understanding these anomalies is very important because water is the ultimate basis for our existence: no water, no life," said SLAC scientist Anders Nilsson, who is leading the

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experimental efforts. "Our work helps explain these anomalies on the molecular level at temperatures which are relevant to life."How the molecules arrange themselves in water's solid form, ice, was long ago established: the molecules form a tight "tetrahedral" lattice, with each molecule binding to four others. Discovering the molecular arrangement in liquid water, however, is proving to be much more complex. For over 100 years, this structure has been the subject of intense debate. The current textbook model holds that, since ice is made up of tetrahedral structures, liquid water should be similar, but less structured since heat creates disorder and breaks bonds. As ice melts, the story goes, the tetrahedral structures loosen their grip, breaking apart as the temperature rises, but all still striving to remain as tetrahedral as possible, resulting in a smooth distribution around distorted, partially broken tetrahedral structures.

Recently, Nilsson and colleagues directed powerful X-rays generated by the Stanford Synchrotron Radiation Lightsource at SLAC and the SPring-8 synchrotron facility in Japan at samples of liquid water. These experiments suggested that the textbook model of water at ambient conditions was incorrect and that, unexpectedly, two distinct structures, either very disordered or very tetrahedral, exist no matter the temperature.

In a paper published yesterday in the Proceedings of the National Academy of Sciences, the researchers revealed the additional discovery that the two types of structure are spatially separated, with the tetrahedral structures existing in "clumps" made of up to about 100 molecules surrounded by disordered regions; the liquid is a fluctuating mix of the two structures at temperatures ranging from ambient to all the way up near the boiling point. As the temperature of water increases, fewer and fewer of these clumps exist; but they are always there to some degree, in clumps of a similar size. The researchers also discovered that the disordered regions themselves become more disordered as the temperature rises.

"One can visualize this as a crowded dance restaurant, with some people sitting at large tables, taking up quite a bit of room—like the tetrahedral component in water—and other people on the dance floor, standing close together and moving slower or faster depending on the mood or 'temperature' of the restaurant—like the molecules in the disordered regions can be excited by heat, the dancers can be excited and move faster with the music," Nilsson said. "There's an exchange when people sitting decide to get up to dance and other dancers sit down to rest. When the dance floor really gets busy, tables can also be moved out of the way to allow for more dancers, and when things cool back off, more tables can be brought in."

This more detailed understanding of the molecular structure and dynamics of liquid water at ambient temperatures mirrors theoretical work on "supercooled" water: an unusual state in which water has not turned into ice even though it is far below the freezing point. In this state, theorists postulate, the liquid is made up of a continuously fluctuating mix of tetrahedral and more disordered structures, with the ratio of the two depending on temperature—just as Nilsson and his colleagues have found to be the case with water at the ambient temperatures important for life.

"Previously, hardly anyone thought that such fluctuations leading to distinct local structures existed at ambient temperatures," Nilsson said. "But that's precisely what we found."

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This new work explains, in part, the liquid's strange properties. Water's density maximum at 4 degrees Celsius can be explained by the fact that the tetrahedral structures are of lower density, which does not vary significantly with temperature, while the more disordered regions—which are of higher density—become more disordered and so less dense with increasing temperature. Likewise, as water heats, the percentage of molecules in the more disordered state increases, allowing this excitable structure to absorb significant amounts of heat, which leads to water's high heat capacity. Water's tendency to form strong hydrogen bonds explains the high surface tension that insects take advantage of when walking across water.

Connecting the molecular structure of water with its bulk properties in this way is tremendously important for fields ranging from medicine and biology to climate and energy research.

"If we don't understand this basic life material, how can we study the more complex life materials—like proteins—that are immersed in water?" asked Postdoctoral Researcher Congcong Huang, who conducted the X-ray scattering experiments. "We must understand the simple before we can understand the complex."

This research was conducted by scientists from SLAC, Stockholm University, Spring-8, University of Tokyo, Hiroshima University, and Linkoping University. The work was supported by the National Science Foundation, the Swedish Foundation for Strategic Research, the Swedish Research Council, the Swedish National Supercomputer Center and the Japanese Ministry of Education, Science, Sports and Culture through a Grant-in-Aid for Scientific Research.

SLAC National Accelerator Laboratory is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy Office of Science. SLAC's Stanford Synchrotron Radiation Lightsource is a national user facility that provides synchrotron radiation for research in chemistry, biology, physics and materials science to over two thousand users each year.

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