Iowa State University Soil,

July 3, 2001

Dear Dennis,

Enclosed please find our third six-month project report on the Nichols site.

If you have any questions concerning the data presented please feel free to contact us.

Department of Agronomy

Crop, Soil, and Environmental SciencesAmes, Iowa 50011-1010

515 294-1360

FAX 515 294-3163

Our results continue to support the conclusion that the ammonium present in these soil samples is “fixed” and thus potentially unavailable for nitrification or nitrate production. We are currently running a series of experiments to determine under what conditions, if any, this “fixed” ammonium can nitrify.

Dennis M. Burchett -Vice President Environmental/Regulatory ServicesUnited Agri Products419 18th Street, P.O. Box 1286

Greeley, Colorado

Iowa State UniversityOF SCIENCE AND TECHNOLOGY

JOtl';er

V -

Sincerely,

QBill EvangelouProfessor 1!

rJ i Chois...E;uc;k._o? -̂------------

O37Z

BY

THIS PROGRESS REPORT WAS PREPARED FOR:

This report includes accomplishments in the third 6-month period of the project.

THIRD PROGRESS REPORT ON SOIL AMMONIUM STATUS OF NICHOLS SITE

AGRONOMY DEPARTMENT IOWA SATE UNIVERSITY

AMES, IA 50011-1010 Phone (515) 294-9237

Fax: (515) 294-3163

V.P. EVANGELOU, PRINCIPAL INVESTIGATOR ([email protected]) LETICIA S. SONON, POST-DOCTORAL FELLOW

JUTTA R.V. PILS, Ph.D. STUDENT

Dennis M. Burchett, Vice President Environmental/Regulatory Services United Agri Products

419 18th Street, P.O. Box 1286 Greeley, Colorado 806-1286 USA

Phone (970) 356-4400

CONTRIBUTING/CONSULTING CO-PIsLarry Halverson, Soil Microbiologist

Robert Horton, Soil Physicist Michael Thompson, Soil Mineralogist

TABLE OF CONTENTS

Page No.

PRACTICAL SUMMARY 11.

TECHNICAL SUMMARY 32.

GENERAL OBJECTIVES 63.

4.. 7

STUDIES CONDUCTED 135.

5.113

5.219

5.330

APPENDICES 346.

ii

78

810

4.14.2

MINERALOGICAL AND CHEMICAL CHARACTERIZATION OF SOIL CLAYS COLLECTED FROM NICHOLS SITE ......

EXPERIMENTS ON K+-Ca2+ EXCHANGE ON THE

ENTIRE EXCHANGE PHASE OF CLAY SAMPLES

METHODOLOGY......................RESULTS AND DISCUSSION

3030

1921

1314

EXPERIMENTS ON K+-Ca2+ EXCHANGE WITH VARIOUS

OSMOTICA....................................................................................................

5.2.1 METHODOLOGY......................5.2.2 RESULTS AND DISCUSSION

5.3.1 METHODOLOGY.......................5.3.2 RESULTS AND DISCUSSION

5.1.1 METHODOLOGY......................5.1.2 RESULTS AND DISCUSSION

EXPERIMENTS ON K+-Ca2+ AND NH4+-Ca2+ EXCHANGE

AT LOW FRACTIONAL LOAD LEVELS..................................

4.2.1 X-RAY DIFFRACTION (XRD)4.2.2 INFRARED SPECTRA (FT-IR)

LIST OF FIGURES

Page No.

15

16

22

23

25

28

iii

Figure 2. Relationship between equilibrium NH4 concentration (CRnh4) and

adsorbed NHZ for NH4+-Ca2+ exchange at low fractional load on soil

samples from three areas (S-l, S-2 and S-3) of the Nichols site...........

Figure 5. Influence of K-load on the exchange phase (Ek) on the Vanselow

selectivity coefficient of soil sample S-l...............................................

Figure 6. Relationship between exchangeable and fixed cations (K+ and Ca2+) at

various K-loads on the exchange phase (Er) for K+-Ca2+ exchange

in S-l soil sample. Lines were drawn to establish trends.........................

Figure 4. Relationship between K-equivalent in the solution phase versus

K-load on the exchange phase for K+-Ca2+ exchange in soil sample (S-l).

The nonpreference line (solid line without data) represents a relationship

when Kv=l.............................................................................................................

Figure 1. Relationship between the equilibrium K+ concentration ratio (CRr)

and adsorbed K+ for K+-Ca2+ exchange at low fractional load on soil

samples. The three data sets represent sampling sites (S-l, S-2 and S-3)

in the Nichols site..........................................................................................

Figure 3. Relationship between the equilibrium K+ concentration ratio

(CRK=K+/(Ca2+)1/2)) and exchangeableK+ for K+-Ca2+ exchange on soil

sample (S-l).......................................................................................................

LIST OF TABLES

Page No.

Table 1. Area of the -1630 cm'1 water deformation band for surface and

subsurface samples of the Nichols site, 11

18

Table 3. Equilibria data of K -Ca exchange on soil sample S-l 27

31

iv

Table 4. Equilibria solution chemistry, adsorbed K+ and fixed NH4+ of S-l

surface soil treated with various osmotica..............................................

Table 2. Equations describing the linear portion of the exchange isotherm

plots of adsorbed K vs. CRk and adsorbed NH4 vs. CRnh4 of soil

samples from three Nichols site areas (S-l, S-2, S-3).......................

LIST OF APPENDIX FIGURES

Page No.

39

40

41

44

v

Appendix Figure 6. X-ray diffractogram for samples S-2 (30-60 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................

Appendix Figure 10. X-ray diffractogram for samples S-3 (30-60 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).........................................................................

Appendix Figure 7. X-ray diffractogram for samples S-2 (60-90 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................

Appendix Figure 5. X-ray diffractogram for samples S-2 (0-30 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K. treated, and e = K + 100° C treated)....................................................................

Appendix Figure 3. X-ray diffractogram for samples S-l (60-90 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................... 37



Appendix Figure 9. X-ray diffractogram for samples S-3 (0-30 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)........................................................................... 43

Appendix Figure 2. X-ray diffractogram for samples S-l (30-60 cm) under different treatments (a - untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)........................................................................... 36

Appendix Figure 8. X-ray diffractogram for samples S-2 (90-120 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)........................................................................... 42

I-

45

46

47

48

49

50

51

52

53

54

55

56

57

58

vi

Appendix Figure 21. IR-spectra of S-3 (0-30 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)

Appendix Figure 22. IR-spectra of S-3 (30-60 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample) ....................




Appendix Figure 16. IR-spectra of S-l (90-120 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)





Appendix Figure 14. IR-spectra of S-l (30-60 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample) ...................................

Appendix Figure 11.treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)

Appendix Figure 12. X-ray diffractogram for samples S-3 (90-120 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated) ;....


PRACTICAL SUMMARY1.

The practical significance of the findings described in this report are as follows: First, the

clay minerals contained in the soil of the Nichols site are for the most part smectites. X-

traditional extraction techniques, an index of potential nutrient bioavailability, failed.

This strongly suggested that the soil “fixed” ammonium would not be readily transformed

to nitrate (NO3’) and the soil’s potential to produce NO3 would be most likely negligible.

Additional observations that would be of importance to NO3 production was the amount

elucidated in our follow up experiments.

In order to shed light in some of the above observations, we carried out studies on

available for NO3 production. Furthermore, we found out that there were two soil

1

of water retained by the soil, determined by spectroscopy, when untreated and treated

with potassium or calcium (Ca2+). These data tell us that upon addition of K+ many of

“whole” and “low” fractional isotherms. The purpose of these isotherms was to reveal if

soil “fixed” NH4+ was independent of exchangeable K+ and determine the different soil

the soil samples showed the quantity of water retained by the clay samples increased,

which hints that the clay may release with time some of its “fixed” NH4+. Furthermore,

treatment with Ca2+ showed a large increase in water retention which may also suggest

some potential release of “fixed” NFL/. It appears that there is some conflict between

traditional NFL/ extraction techniques and spectroscopic techniques which would be

sinks of exchangeable monovalent cations that are available on the Nichols site soil

samples. Our “whole” isotherms showed that “fixed” NEL/ was independent of

exchangeable K+. This again suggested that the “fixed” NH/ would not most likely be

ray diffraction evidence suggested that these smectites have the potential to fix

ammonium (NH/) and potassium (K+). Attempts to extract the “fixed” NFL/ and K+ by

to influence the release of fixed ammonium which is subject to nitrification.

soil. We will be using the following approaches:

Control1.

j A |

Sugars with low/high K /Ca ratios2.

• Fresh com vegetation

• Dry com vegetation

• Pure osmoticum

High redox3.

Low redox4.

Lime-induced volatilization5

The purpose of the above treatments is to evaluate potential release of the “fixed” NH4+

on the basis of what we have learned so far. Furthermore, we want to determine how we

can take this released “fixed” NFL|+ and transform it to NH3 gas or nitrogen (N2) gas.

I

2

We are now continuing to elucidate the role of soil redox or Eh on the release of “fixed”

NH4+. Currently we have designed and started to run a number of experiments to reveal

how this above knowledge can be used to remove, if possible, “fixed” NIL|+ from the

weakly. Moreover, the findings revealed that all soil samples tested, using low fractional

isotherm studies, contained negligible quantities of exchangeable NH4+ and most of the

NH4+ present is in the “fixed” or “confined” form. Addition of osmotica (sugars) appears

monovalent Cation sinks. One soil sink held the monovalent cations (K+ or NH«+) very

strongly but not “fixed” and the other soil sink held the monovalent cations (K+ or NH4+)

2. TECHNICAL SUMMARY

accessible sites and non-extractable sites, most likely internal sites. Ammonium ions

occupying clay external or easily accessible clay sites were readily available while those

in the clay internal sites were “confined” and therefore considered unavailable.

Soil samples from the Nichols site as well as normal Iowa agricultural soils appear to

3

unsuccessful. A 3-week nitrification study was performed to determine whether or not

this “fixed” NH4+ fraction could be nitrified (NH4+

exhibit high tendency to fix ammonium (see Project Report No. 2). Attempts to extract

the fixed NH4+ using cation exchange resin and cations, such as K+ and Ca2+, were

The availability of soil “fixed” NH4+ and its possible contribution to groundwater

pollution, in the form of NO3, has been the overall focus of this research project. Earlier

research activities involved chemical and mineralogical characterization of soil samples

collected from the Nichols site. This was followed by a series of experiments that

examined the releasability of “fixed” NH/ under various conditions. Our mineralogical

Distinction in ammonium clay sink was made through chemical means, i.e.,

exchangeable (-available) NH/ fraction was displaceable from clay exchange sites by K

ions (1 M KC1 extraction); “fixed” NH4+ by clay destructive techniques.

analysis showed that the Nichols soil samples (S-l, S-2 and S-3) were highly smectitic in

nature. Owing to the smectite’s expansive properties, NH4 ions were shown to occupy

two distinct clay sites: easily extractable sites, most likely external sites or easily

> NO3-) under a set of optimum

incubation conditions. Our results indicated that soil sample S-l, with the highest “fixed”

NH?, did not produce significant amount of NO3 at any depth compared to soil samples

S-2 and S-3 with lower “fixed” NH/. This implied that “fixed” NH4+ was not

bioavailabie and furthermore "fixed” Nil/ bioavaiiabiiity was independent of soil

sample.

For a holistic understanding of the chemistry of NH4+ in the Nichols site, we needed to

quantity-intensity approach for simulating Nichols site soil conditions. The results of

these experiments would enable us to describe the ability of soil from the Nichols site to

exchangeable with the soil solution. Such observation was in full agreement with our

earlier experimental results which, showed that NH4 ions were tightly fixed by the S-l

clay samples.

A second set of experiments was carried out in order to evaluate the entire exchange

4

maintain a certain cation concentration in solution as influenced by the soil clay surfaces

and the quantity of soil adsorbed NH4+.

phase of the clay samples from the Nichols site. The purpose of this evaluation was to

determine the nature of the clay surface and furthermore evaluate if the quantity of K+ on

The low fractional load isotherm studies suggested that the three Nichols soil samples (S-

1, S-2, and S-3) exhibited comparable ability to adsorb/desorb K+ by the exchanger

phase. However, in the NFLi+-Ca2+ system, the S-l soil sample showed marginal ability

to provide soil solution NH4+ buffering compared to the other two soil samples. It

implied that a large fraction of the adsorbed NH4+ remained “fixed” and, therefore, non

Nichols site. Our experiments describe cation exchange equilibria between soil and soil

solution at relatively low fractional loads of K+ and NH4+ employing a modified

investigate its interaction with other cations, commonly found in all agricultural soils,

e.g., K+ and Ca2+. Our present report (Third Report) provides detailed exchange

reactions of K+ versus Ca2+ and, NFL/ versus Ca2+ in soil samples collected from the

5

the clay controlled the quantity of “fixed” KJ and/or “fixed” NH4+. Throughout the entire

isotherm, K+ ions were preferentially adsorbed over Ca2+ by the exchange sites. The

exchanger demonstrated two classes of sorption sites: high affinity and low affinity sites.

The data suggested that the clay internal sites (interlayers) comprise the high affinity

sites, which were more active in sorbing K at the lower end of the CRk values. In other

words, at the lower equilibrium K+ concentration or ratio (CRk < 0.2), K+ ions were

strongly held. The foregoing observation was also supported by the relatively high

selectivity coefficient (Kv > 22) at this point. As the solution was loaded with more K+

(increasing CRk), the exchanger selectivity for K+ ions decreased implying that these ions

could be easily replaced from the exchange phase. Release of “fixed” NH/ throughout

the entire isotherm was not evident at all. “Fixed” NH4+ remained at ~7.5 cmolc kg'1

regardless of K+-load on the exchanger. This implied that application of K+ or increased

levels of K+ would not have any influence on level of “fixed” NH4+.

A follow-up study on K+-Ca2+ and NTL|+-Ca2+ exchange as influenced by glucose was

carried out to further investigate the effect of osmotic pressure, a potential influence

induced by the decomposition of vegetation in late fall. This study was an offshoot of

our previous findings that showed “fixed” ammonium in glucose-treated soil samples

markedly decreased after a 20-day incubation period (see Project Report No. 2).

Mannitol, along with glucose, was added to soils with solutions of various K+/Ca2+ ratios.

Soil samples representing the control (no osmoticum) generally had higher “fixed” NH/

than those that received osmoticum regardless of the equilibrium K+ concentration ratio

(K+/(Ca2+)1/2). In other words, “fixed” NH4+ decreased upon the introduction of an

osmoticum into the system. The data suggested that some “fixed” NH4+ may become

bioavailable due to the production of osmoticum during decomposition of natural

GENERAL OBJECTIVES3.

6

vegetation on the Nichols site. Our goai is to develop procedures by which bioavailable

NH4+ would be transformed to gas products N2 or N2O.

The purpose of this portion of the overall laboratory investigation was to determine and

characterize K+-Ca2+ and NH4+-Ca2+ exchange reactions in soil samples representing the

Nichols site and relate this to the bioavailability of NH4+. Moreover, the role of

osmoticum in the release of “fixed” NH4+ was investigated to evaluate its potential role

in the remediation strategies for the “fixed” NH4+-rich Nichols site.

4.

METHODOLOGY4.1

X-Ray Analysis. Approximately 150 mg of clay, representing the S-l, S-2, and S-3

areas of the Nichols site, and 10 ml of 1 M KCl.were added to 50-ml polyethylene

centrifuge tubes. The mixtures were agitated in a reciprocating shaker for 30 minutes.

third time, clay suspensions were mounted on ceramic tiles for x-ray examination.

Desired clay orientation was achieved by adding clay suspension in small increments

using a Pasteur pipette. The tiles were washed three times with deionized water to

remove excess salt. The same procedure was followed for clay samples treated with 1 M

MgCh and with deionized water. All tiles were stored in a dessicator containing

saturated MgNCh to maintain a relative humidity of approximately 54%. After x-raying

all equilibrated tiles at 54% relative humidity, the K-tiles were heated to 100 °C and the

Mg-tiles were treated with 30% glycerol prior to x-ray diffraction. X-ray diffraction

analysis was carried out using the Siemens D500 Diffraktometer equipped with Siemens

Kristalloflex x-ray generator.

Fourier-Transform Infrared (FT-IR) Analysis: Clay samples representing the S-l, S-

2 and S-3 areas of the Nichols site were saturated with 10 ml of 1 M KC1 in 50-ml

polyethylene centrifuge tubes. The mixtures were agitated in a reciprocating shaker for

30 minutes. After centrifuging at 1500 rpm for 5 minutes and decanting the supernatant,

7

MINERALOGICAL AND CHEMICAL CHARACTERIZATION

OF SOIL CLAYS COLLECTED FROM NICHOLS SITE

After centrifuging at 1500 rpm for 5 minutes, salt wash was repeated two more times to

ensure complete saturation of the exchange sites by K+. After shaking the samples for the

salt wash was repeated two more times to ensure complete saturation of the clay samples

with K+. After washing with deionized water, the clay samples were air dried for FT-IR

analysis. The same procedure was used to saturate the ciay samples with ca2+ using 1 M

CaCh. The clay samples were mixed with KBr on a 1:10 weight ratio recommended for

FT-IR analysis using diffuse reflectance or DRIFT. The clay-KBr mixture was finely

ground using mortar and pestle and approximately 15 mg of the mixture sample was

placed in an FT-IR sample cup holder and analyzed with the Nicolet Magna-IR 560

Spectrometer.

RESULTS AND DISCUSSION4.2

4.2.1 X-Ray Diffraction (XRD)

NH4+. For example, exchangeable K+ or NH4+ is associated with the > 14 A peak

whereas the 10 A peak represents possible “caged” or “fixed” NH4 or K ions within the

collapsed interlayer of 2:1 expandable clay minerals.

General mineralogical characterization can be made for these soils based on x-ray

diffraction peaks. Spectra 'a' in Appendix Figs. 1-12 represent the untreated samples and

are used as reference. In order to differentiate between 2:1 expanding clay minerals and

8

2:1 non-expanding clay minerals, subsamples representing S-l, S-2 and S-3 soil samples

were treated with Mg2+ (b) and Mg2+ + glycerol (c). In general, all clay samples saturated

with Mg2+ showed a 14 A peak. Magnesium-saturated clay samples were treated with

glycerol to differentiate smectite and vermiculite. If smectite dominates the clay fraction,

the near 14 A peak shifts to >18 A, whereas in the case of vermiculite the 14 A peak

The data in Appendix Figs. 1-12 show x-ray of S-l, S-2 and S-3 samples from the

Nichols site. These XRD data are also used to identify “fixed” or exchangeable K+ or

remains the same, lhe 10 A peak can be due to mica or collapsed vermiculite due to

“caged” NH4 ions. Mica is also associated with a sharp high intensity peak, comparable

to the quartz peak, at a d-spacing of 3.3 A.

smectite.

Description of XRD Spectra

smectite was present in the clay sample.

vermiculite as the dominant clay mineral. In order to provide additional support for

9

eliminated the possibility of chlorite being present in the clay sample, whereas the

collapse of the >14 A to 10 A peak after the KC1 plus 100 °C treatment (e) ensured

observed for Mg treated (b) and for Mg + glycerol treated samples (c), which indicated

presence of smectites. The disappearance of the 14 A peak after KC1 treatment (d)

The untreated (a) and magnesium-treated (b) S-2 clay for the 0-30 cm depth revealed d-

spacing of 14 A. Clay samples representing the lower depths showed an increase in d-

spacings after Mg treatment from 14 A to ~16 A. After application of glycerol (c) to the

Mg-treated clay samples, the interlayer spacing increased to 18 A, eliminating

Clay subsamples representing S-l, S-2 and S-3 soil samples were also treated with IN

KC1 (d) to observe possible enhancement/appearance of the 10 A peak, which would

support presence of vermiculite. The KC1 treated clay samples were then heated to 100

°C (e) to verify which of the two 2:1 clay minerals, smectite or vermiculite, was present.

Collapse of the >14 A peak to the 10 A peak upon heating indicated presence of

Based on the above clay mineralogical characterization, x-ray diffractograms of sample

S-l at all four depths show similar trends. Shift from 14 A to >18 A d-spacing was

minerals.

4.2.2 Infrared Spectra (FT-IR)

10

Intensities of the 14 A and 10 A peaks and their significance in regard to NHZ “caging”

or fixation has been described in Project Report No. 2.

The data in Appendix Figs. 13 to 24 show FT-IR spectra for the soil samples S-l, S-2,

and S-3 of the Nichols surface and subsurface soil samples under different treatments,

distinguishing smectite from vermiculite, KC1 treatment was introduced. Vermiculite

was not present in these samples as the 10 A peak did not intensify upon K-saturation

whereas the lack of a 14 A peak eliminates the presence of chlorite. After heating the K

samples to 100 °C the shift from 14 A to 10 A supported the presence of smectite.

where ‘a’ represents untreated or control, ‘b’ represents Ca-saturated, and ‘c’ represents

K-saturated. Table 1 shows the area of the approximately 1630 cm'1 water deformation

band. This band is associated with water molecules mostly within the clay interlayer.

All clay samples showed a significant increase of water molecules in the interlayer after

the soil sample was saturated with 1 M CaCh. This showed possible clay expansion due

to the Ca ion. However, the corresponding increase in the wavenumber of the NFL/

deformation band (-1430 cm'1), did not support release of the NH4 ion as would be

expected. Only sample S-2 (90-120 cm depth ) indicated a decrease in the NFL/

The x-ray diffractograms of clay sample S-3 were nearly identical to clay sample S-2

with the only difference that the Mg treatment showed 14 A peak as the untreated sample

at all four depths. The increase to 18 A peak after glycerol treatment (c) and the collapse

of the 14 A peak to 10 A after heat treatment, suggested the presence of smectite

I

Table 1. Area of the ~1630 cm*1 water deformation band for surface and subsurface samples of the Nichols site.

Treatment Area Sample-ID TreatmentSample-ID Area

S-2 (60-90 cm)S-l (0-30 cm)

S-2 (90-120 cm)S-l (30-60 cm)

S-3 (0-30 cm)S-l (60-90 cm)

S-3 (30-60 cm)S-l (90-120 cm)

S-3 (60-90 cm)S-2 (0-30 cm)

S-3 (90-120 cm)S-2 (30-60 cm)

16.44

22.53

19.76

8.96

35.36

9.10

10.98

26.91

13.1

12.45

19.38

8.63

17.28

32.91

14.81

Untreated

Ca-saturated

K-saturated

12.91

26.57

11.81

10.59

25.71

6.38

17.28

27.71

13.25

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

Untreated

Ca-saturated

K-saturated

8.69

34.63

15.74

Untreated

Ca-saturated

K-saturated

14.92

25.43

20.22

19.21

25.90

20.18

12.97

28.40

15.48

12

Note that x-ray and FT-IR spectroscopic data suggest certain expected behavior with

respect to soil NH4+ release/fixation. Wet chemistry evidence are needed to verify this

suggestion. The following section provides some wet chemistry evidence on NFL/ and

K+ fixation/exchange behavior.

deformation band from 1431 cm'1 for the untreated sample to 1423 cm'1 for the K+

saturated, and to 1407 cm'1 for the Ca2+ saturated sample. This wavenumber decrease

suggested that expansion of the interlayer weakened the NH4+ clay lattice interaction.

However, all other eleven samples showed an increase in wavenumbers of the NH4+-

deformation band suggesting that NH4+ was in a non-exchangeable form despite

interlayer expansion by cation saturation.

STUDIES CONDUCTED5.

5.1

METHODOLOGY5.1.1

Sample Treatment. Surface (0-30 cm) soil samples from 3 sites (S-l, S-2, and S-3)

the end of the equilibration period, pH and electrical conductivity were measured in each

suspension. The mixture was then centrifuged at 8,000 rpm for 5 min. The supernatant

was collected and analyzed for cations using the atomic absorption spectrophotometry

(AAS). All experimental units were carried out in duplicates.

13

EXPERIMENTS ON K+-Ca2+ AND NH/-Ca2+ EXCHANGE AT LOW

FRACTIONAL LOAD LEVELS

were passed through a 2-mm sieve. Twenty-five milliliters of each solution with a

specified K+/Ca2+ ratio were added to 2.5-g soil sample. The mixture was equilibrated on

a reciprocal shaker at a speed of 180 cycles min’1 for 24 h and at room temperature. At

Solution Preparation: Solutions of varying K+/Ca2+ ratios were prepared using KC1 and

CaCh. The initial K concentrations ranged from 2.9 to 13 mmol L’1 while those for Ca2+

ranged from 3.97 to 11.9 mmol L'1. After equilibration, K+ and Ca2+ concentrations

ranged from 0.28 to 11 mmol L'1 and 0.18 to 8 mmol L’1, respectively, resulting in an

array of CRk. values (0.005 to 0.200 (mol L_1)1/2), simulating the Nichols site.

5.1.2 RESULTS AND DISCUSSION

14

The data in Figs. 1 and 2 show examples of the relationship between the equilibrium

concentration ratio (CRk or CRnh4) and adsorbed K+ or NH/ at low fractional loads. In

the K+-Ca2+ exchange (Fig. 1), the adsorbed K increased as the concentration ratio of K+

in solution increased. The curves were generally curvilinear but the curvilinearity was

more expressed in the S-l soil. In particular, S-l soil sample exhibited curved portions at

CRk values <0.05 and >0.15 (L mol'1)172. This foregoing trend could suggest two things:

high K+ affinity sites were adsorbing K+ at lower CRk values but exchange sites became

inaccessible at high CRk values. One plausible explanation for the behavior of S-l soil

sample is the “pinching” effect of the K+ ions. Perhaps, the clay interlayers collapsed

towards the K+ ions as the latter enter the internal surfaces. Under this condition, the

internal surfaces would be excluded from any exchange reaction. The K+-Ca2+ exchange

would now be limited to only certain sites and hence, decreasing the exchangeable K+

concentration at a given CRk level.

Unlike in S-l soil, the exchangeable K+ concentrations in S-2 and S-3 soil samples

concomitantly increased with CRk. This trend may indicate that the loading of K+ ions in

the solution did not alter the clay exchange sites in adsorbing/desorbing K+ ions. Simply

put, the interlayers could have not participated in the exchange process or K+ did not

induce an interlayer “pinching” effect within the range of CRk this experiment was

carried out. Subsequently, the K+-Ca2+ exchange in S-2 and S-3 soils was exclusive to

readily exchanging surfaces of the clays only. The surfaces may include expanded

interlayers and/or external surfaces only. One additional point that Fig. 1 reveals is that

S-l soil exhibits little exchangeable K+. This is revealed from the fact that its y-intercept

exhibits a relatively small negative value (0.58 cmolc kg'1; Table 2). The negative value

4.00

3.00

2.00 -

1.00

0.00

-4.00

-5.00

0.000 0.1500.050 0.200 0.250

15

♦ S-1

HS-2

AS-3

o>o o

o- eE,

* -1.00 -I o n

8 -2.00 - ■o <

-3.00

CRk (mol L'1)1/2

Figure 1. Relationship between the equilibrium K concentration ratio (CRk) and adsorbed K+ for K+-Ca2+ exchange at low fractional load on soil samples. The three data sets

represent sampling areas (S-1, S-2 and S-3) in the Nichols site.

0.100

7.0

6.0

-1.0

0.04 0.08 0.12 0.16 0.20

16

-2.0 J—

0.00

Figure 2. Relationship between equilibrium NH4 concentration ratio (CRnfm) and adsorbed NH4+ for NH4+-Ca2+ exchange at low fractional load on soil samples from three areas

(S-1, S-2 and S-3) of the Nichols site.

! <S-1 |

bs-2

•g 2.0 .ag 1.0 ■u <

0.0

CF^fmolL-1)1'2

8.0

17

of the y-intercept reveals exchangeable K+ under the experimental conditions

(approximately 10 meq L' Ca“ in solution). However, the same can not be said for soil

samples S-2 and S-3. These two samples contain large amounts of exchangeable K+

under the experimental conditions, which are designed to simulate soil field conditions.

Note that the y-intercept is highly negative for both soil samples (1.91 and 5.87 cmolc

kg'1). These quantities represent large amounts of soil exchangeable K+.

The NH4+-Ca2+ exchange is graphically presented in Fig. 2. Here, the isotherms are

slightly curvilinear for the three soil samples (S-l, S-2 and S-3) studied. But again, the

isotherm line was more curved at CRnh4<0.05 in the S-l soil sample and such

observation was not necessarily evident in the other two soils. However, unlike K -Ca

exchange, NHi+-Ca2+ exchange does not exhibit major negative y-intercept (Table 2). It

signified that the quantity of exchangeable NH/ was negligible. Any residual inorganic

NH4+ present in the soil was “fixed”. The latter quantity was determined by using the

HF-HC1 procedure, which is designed to extract tightly held NH4+.

Figure 2 also suggests that the newly added NH4+ became exchangeable. This is revealed

by the slope of the plots in Fig. 2. These slopes are relatively small (48 to 74) and signify

exchangeable NH4+. Slope greater than 100 would signify tightly held NH4+ and

significantly greater than 100 would suggest “fixed” NH/. These data suggest that the

ability of these soil samples to fix any additional NH4+ is not apparent. However, the

plots do reveal if the "fixed" NHf1- can become exchangeable which may lead to NO3

formation.

V

R2Prediction Equation y-interceptSoil Slope

- - cmolc kg*1 - -

K-Ca

NH4-Ca

00

0.948

0.989

0.994

-0.59

-5.87

-1.91

-0.59

0.19

0.05

y = 41.95x-0.58

y = 41.89x-5.87

y = 31.21x-1.91

S-l

S-2

S-3

S-l

S-2

S-3

Table 2. Equations describing the linear portion of the exchange isotherm plots of adsorbed K vs. CRr and adsorbed NH/ vs.

CRnh4 of soil samples from three Nichols site areas (S-l, S-2 and S-3).

ExchangeSystem

y = 54.29x - 0.59

y = 74.87x + 0.19

y = 48.06x + 0.05

0.954

0.973

0.977

41.95

41.89

30.21

54.29

74.87

48.06

cmolc kg*‘/(mol L*1)172

5.2

5.2.1 METHODOLOGY

our earlier chemical tests. Potassium-saturated soil (KSOii) was prepared by adding 300

exchange sites. After the third saturation cycle, the supernatant was decanted and the

remaining solid materials were washed thoroughly with deionized, distilled water until

approximately -30% and labeled as KSOii. The calcium-saturated soil (CaSOii) was

prepared by using 1 N CaCh solution following the procedure as described above for

Ksoil-

19

mL of 1 N KC1 to a 150 g soil sample. The mixture was shaken on a reciprocal shaker at

a speed of 180 cycles min’1 and allowed to equilibrate for three days. After equilibration,

EXPERIMENTS ON K+-Ca2+ EXCHANGE ON THE ENTIRE

EXCHANGE PHASE OF CLAY SAMPLES

Soil Preparation and Pre-Treatment: Soil samples representing the S-l area of the

Nichols site were pre-saturated with either K. or Ca . The 0-30 cm depth sample was

selected because generally this depth had the highest level of “fixed” NH/ as shown by

the electrical conductivity registered at -1.0 mmhos/cm (equivalent to approximately 10

meq K+ L’1). The solid materials were partially air-dried to a moisture content of

the liquid was decanted and the solid was again washed with 300 mL of 1 N KC1. These

steps were carried out in three cycles to ensure maximum K+ saturation of the soil

The following initial treatment percentages (% K/% Ca) were used in the experiment: Tj-

5% K / 95% Ca; T2- 10% K / 90% Ca; T3- 20% K / 80% Ca; T4- 30% K / 70% Ca; Ts-

40% K / 60% Ca; T6- 50% K / 50% Ca; T7- 60% K / 40% Ca; Tg- 70% K / 30% Ca; T9-

80% K / 20% Ca; Tio-90% K /10% Ca; T,,-95% K / 5% Ca.

equilibration, electrical conductivity and pH of each tube was measured.

spectrophotometry (AAS). Correction was made for the soil-entrapped solution after

20

Preparation of Solution with Various K+/Ca2+ Ratios: Solutions of different K+ to

Ca2+ ratios and an ionic concentration of 10 meq/L were prepared using KC1 and CaCl2.

Exchange Reaction Experiment: The K+-Ca2+ exchange reaction was carried out

employing a batch technique. Triplicate 2.5-g soil samples were placed in pre-weighed

50-mL centrifuge tubes. The weight of KSOii to Ca50n ratio in each centrifuge tube was

matched with the corresponding K+ to Ca2+ concentration ratio of the solution described

previously. Twenty-five mL of the corresponding K to Ca ratio solution was added to

suspensions were then centrifuged at 8,000 rpm for 5 min and the supernatants were

collected in clean container and later analyzed for K+ and Ca2+ using atomic absorption

equilibration. The solid phase was then extracted with 1 M NTUOAc and extracts were

analyzed for exchangeable K+ and Ca2+. Determination of “fixed” K+ and “confined or

fixed” NH4+ were carried out following the HNO3 and HF-HC1 procedures, respectively.

each of the centrifuge tube. The mixture was placed on a reciprocating shaker for 7 days

under room temperature to reach a K+-Ca2+ exchange equilibrium state. After

The


The data in Fig. 3 show the influence of CRk (CRk = K+/(Ca2+)1/2) on exchangeable K ■+

increasing CRk, there was a corresponding increase in ExK. A closer inspection of the

21

(ExK). The overall plot of CRk vs. ExK produced a curvilinear line approaching a y-

maximum of 18 cmolc kg’1, which, theoretically represents the CEC of S-l soil. Upon

S-l soil sample. Throughout the entire isotherm, all equilibrium data points are above the

nonpreference line, suggesting a preferential sorption of K+ over Ca2+ by the clay surface.

Furthermore, these data point out an abrupt change in the slope of experimental plot as

The data in Fig. 4 demonstrate the relationship between the equivalent fraction of K+ in

the solution phase versus the equivalent fraction of K+ in the exchange phase, otherwise

known as fractional isotherm. The experimental curve illustrates the monovalent cation

preference by the exchanger in a heterovalent exchange reaction (K+-Ca2+ exchange) on

and this fraction may not be exchanging with the solution phase. As the CRk was

increased and the relationship became linear, K+ may have been adsorbed by exchange

sites in the planar or basal surfaces. This fraction of K+ was exchangeable with the

solution. The practical significance of this observation is that the K+ associated with the

less than 20% of the observed CEC of the S-l sample was not readily desorbed or

released to the soil solution, hence not readily available for plant uptake. This is

consistent with expected behavior supported by the FT-IR and x-ray data.

curve, however, revealed a biphasic relationship rather than the expected curvilinear

relationship asymptotically approaching the cation exchange capacity (CEC) of the soil

sample. The plot (Fig. 3) appears curvilinear at lower CRk values and becomes linear at

sthe higher CRk values. This two-part curve suggested' the presence of different sorption

sites on the clay surface. At CRk < 0.20, specific interlayer sites may have adsorbed KT"

18

16

14

12 -

10 -

8 -

6

4 ■

2

0.20 0.40 0.60 1.00 1.20 1.40

22

o 4—

o.oo

Figure 3. Relationship between the equilibrium PC concentration ratio (CRic=K+/(Ca2+)1/2) and exchangeable K+ for K+-Ca2+ exchange on soil sample S-l.

aw

i

u

JU s

4) ©£

AQ

w

I

I

0.80

CRk (mole L'1)’72

x" x'

/

*

*

4

I

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

nonpreference line

0.20- I0.10

Ek (solution phase)

23

0.00

0.00

Figure 4. Relationship between K-equivalent in the solution phase versus K-load on the exchange phase for K+-Ca2+ exchange in soil sample S-l. The nonpreference

line (solid line without data) represents the relationship when Kv=l.

C/5

XS ex

OJD fl a x

Q XO

*

x1

z" t

I t

I

I

I

I

II

I I

/

/

✓ II

f I

0.10 020 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Er approaches zero, which signifies high affinity sites for the monovaient cation by the

clay surface.

24

The data in Fig. 5 show change in cation affinity as a function of cation load on the

exchange phase (Ek). These data revealed that there are at least two classes of exchange

sites with respect to K -Ca exchange in the Nichols S-l soil sample. At low equivalent

K+-load, the soil exhibited high affinity for K+. Furthermore, a strong preference for K+

over Ca2+ is shown up to Ek=0.2, but an abrupt decline in Kv occurred beyond this point.

At higher K+-loads (Ek>0.40), the magnitude of Kv approached 3 indicating a

diminishing preference for K+ by the exchanger phase. The entire isotherm, however, did

not show any reversal of preference, i.e., Ca2+ over K+, but strongly suggested a different

solid and solution phase environment at both ends of the curve. The system behaved as

an ideal solid-solution at higher CRk environments and that the surface was complexing

with the cations uniformly at Ek values >0.40. The significance of these data is that a

fraction of the K+ load was strongly held by the soil. Indirectly, this may also suggest

that any NH4+ associated with these exchange sites would also be strongly held and thus,

relatively unavailable to organisms for producing NO3.

The affinity of an ion by the exchange phase of a soil can be determined by using the

Vanselow selectivity coefficient, Kv. In K+-Ca2+ exchange, the magnitude of Kv usually

represents the relative affinity of K with respect to Ca" by the clay surface. When Kv=l

at a given level of exchangeable K, the exchanger at that level of K+ load shows no

preference for either K+ or Ca2+. On the otherhand, a KV>1 at any given level of

exchangeable K+ signifies exchange preference for K+. Conversely, Kv values less than 1

indicate preference of Ca2+ over K+ by the exchange phase.

50.00

45.00

40.00 -

35.00 -

20.00 -

15.00

10.00

5.00

0.80 1.000.20 0.40 0.60

Ek (exchange phase)

25

0.00 J—

0.00

4

Figure 5. Influence of K-load on the exchange phase (Ek) on the Vanselow selectivity coefficient of soil sample S-l.

;♦ II I I I I II I I II

I t I

I

\

\

\

30.00 -

E 25.00 - e

£

26

perhaps due to protonation of functional groups at the clay edges and planar surfaces. At

low pH, protonation of some functional groups could lend to the reduction in electrical

Another observation in this experiment was that the calculated CEC (sum of ExK and

ExCa) increased towards the direction of the K+-rich end of the isotherm; On the other

surface potential, a condition that would the favor sorption of monovalent ion over that of

divalent ion. As the pH increased, deprotonation of these functional groups would result

in greater surface electrical potential, a condition favorable for Ca2+ sorption resulting in

lower Kv values. Deprotonation, however small, at higher pH may explain the increase in

CEC at the K-rich end of the isotherm.

A graphical presentation of the relationship between exchangeable and fixed cations at

various K-loads on the exchange phase is given in Fig. 6. It (Fig. 6) illustrates the inverse

trends of exchangeable K+ and Ca2+ along the K-load exchange phase axis. At high K+-

load, exchangeable Ca was low and vice versa. Concentration of “fixed” K slightly

increased towards the K-rich end of the isotherm. “Fixed” NH4+, however, remained at

approximately 7.5 cmolc kg'1 all throughout the isotherm, which implied that additional

fixation or desorption was negligible. This observation appeared to be consistent with our

hand, Kv appeared to be influenced by pH; as pH decreased, Kv increased and vice versa.

This pH decrease signifies an increased affinity for the K+ ions by the clay surface

The data in Table 3 show cation exchangeability on S-l soil sample. The data show a pH

gradient on the isotherm. For example, the pH of the K+-rich isotherm was higher

(pH=4.72) than that of the Ca-rich isotherm (pH=4.28). Apparently, Ca was exchanging

with aluminum more efficiently than K+. In fact, the concentration of exchangeable Al3+

at the end of the equilibration period was slightly lower in the Ca2+-rich end of the

isotherm, implying Al3+ release into the soil solution and hence, lower pH.

Table 3. Equilibria data of K+-Ca2+ exchange on soil sample S-l.

Solution Exchangeable Total* Kv“Fixed KpH

Ca KK Ca

mM-

4.28±0.01f 5.18± 0.05 2.94±0.170.80±0.12 9.91±0.39 25.6712.82±0.88 0.86 42.87

nd:4.95± 0.02 3.43±0.071.43 ±0.034.30 ±0.02 12.05±0.43 11.23±0.24 26.71 22.36

4.19± 0.10 4.58±0.153.22 ±0.12 10.96±0.544.30 ±0.01 11.70±0.33 27.23 0.98 12.42

4.63± 0.15 3.48± 0.07 5.21±0.354.29 ± 0.02 8.58±0.81 13.40±0.57 27.19 nd 10.42

6.20±0.275.91 ±0.12 2.71 ±0.08 8.27±0.594.33 ±0.02 13.26±0.55 27.73 nd 8.35

2.02±0.13 7.44±0.19 8.09±0.636.66 ±0.144.41. ±0.06 13.04±0.06 28.57 0.97 7.36

1.50 ±0.17 8.67±0.887.99 ±0.45 7.65±0.644.44 ± 0.03 12.50±0.14 28.82 nd 6.10

10.70±1.070.83 ±0.19 6.15±0.279.68 ±1.55 30.12 nd4.48 ± 0.03 13.26±0.27 4.85

12.48±0.370.41±0.06 4.26±0.4010.68± 0.14 13.78±0.41 30.534.56 ±0.01 1.04 4.21

0.09 ±0.01 16.11±0.11 2.32±0.4511.26± 0.124.66 ± 0.03 14.53±0.86 32.95 nd 3.11

16.31 ±0.2311.49±0.02 0.08± 0.00 1.50±0.26 14.91±0.37 32.724.72 ± 0.02 1.16 3.56

* Total = Exchangeable (K+Ca) + Fixed K♦ ♦ , i - rr- •

Exch.Al

Vanselow selectivity coefficient f Standard deviation

not determined

(L mol4)172cmolc kg'1

« ExK □ ExCa X Fixed NH4

18

16

14

... A...-...12

10

8•X-X- -x- XX6

4

2

0.30.2 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Ek (exchange phase)

28

Figure 6. Relationship between exchangeable and fixed cations (K+ and Ca2+) at various K-loads on the exchange phase (EK) for K+-Ca2+ exchange in S-l soil sample. Lines

were drawn to establish trends.

o0.1

44u

o E u a .2

u aO) u fl o

A ..

□

.J-”

A Fixed K

29

The above overall data strongly suggested that “fixed” K+ and NHZ are constant and

independent of K+ load. We strongly feel that this is a critical information for this

particular project.

earlier findings showing that “fixed” NH/ in S-l soil was energetically strong and

relatively irreversible.

EXPERIMENTS ON K-CA EXCHANGE WITH VARIOUS OSMOTICA5.3

5.3.1 METHODOLOGY

Osmoticum sources and soil treatment: Potassium-calcium exchange reactions under

various osmotica was studied using the batch technique. The osmotica were glucose

(C6H12O6) and mannitol (CgHuOe) both at 4% on weight to volume basis (w/v). Five

grams of S-l soil sample were weighed into 150-mL Erlenmeyer flasks. To one group of

flasks, 2.0 g of glucose was added, another group 2.0 g mannitol was added, and a third

(EC), redox potential and osmotic pressure were measured at the end of the equilibration

period. The osmotic pressure was indirectly obtained by measuring the osmolality of the

absorption spectrophotometry (AAS). The solid materials in the flasks were analyzed for

fixed ammonium following the HF-HC1 procedures.


Data on equilibria solution chemistry at various osmotica are shown in Table 4.

Introduction of osmotica to the solution invariably results in an increase in osmotic

pressure. Osmotic pressure varied from 1.31 to 1.44 MPa in the presence of 4% glucose

or mannitol as compared to 0.19 - 0.22 MPa for the soil solution alone. Solution pH

values were comparable between osmotica and control treatments. The only difference

30

group served as the control (untreated). To each of the sample in the test tubes, 25 mL

of solution composed of various ratios of K+/Ca2+ was added. The mixture was shaken on

a mechanical shaker at 180 cycles min'1 for 24 h. Solution pH, electrical conductivity

solution by a vapor pressure osmometer. The mixture was then centrifuged at 8,000 rpm

for 5 min and the supernatants were analyzed for cations (K+ and Ca2+) using atomic

Table 4. Equilibria solution chemistry, adsorbed K and fixed NH4 of S-l surface soil treated with various osmotica.

Solution phase Solid phase

Osmoticum CRkFixed NH4PH(K+/(Ca2+)1/2)

(mS cm'1)-lxl/2 (MPa)(mol L ) (mV)

H2O (control) 8.93

Glucose (4%) 6.56

Mannitol (4%) 7.07

0.190.210.210.22

1.311.381.401.39

-0.432.732.811.45

3.853.333.243.31

613622622615

7.459.958.849.49

7.615.547.537.59

0.151.721.962.01

3.863.293.263.30

0.142.282.522.61

621623629616

0.15

1.822.002.06

3.86

3.213.213.29

623

619625615

5.25

7.715.657.62

0.023

0.0960.1710.213

1.35

1.441.421.44

-0.43

1.532.551.22

Electricalconductivity

Redox potential

Osmotic

pressure

-0.49*

2.271.770.73

0.0240.0920.1640.214

AdsorbedK

cmolc kg'1

Mean FixedNH/‘

0.0240.0890.148

__________________0.206 _______________________________* Negative value indicates K desorption from the exchange phase. ** Mean fixed NH4 within an osmoticum treatment.

noted was a higher soil pH in the lowest CRk system, a trend consistent in all three

Electrical conductivity (EC) decreased in the presence of osmoticum osmotica.

d-spacing.

bioavailable. These results reveal that sugars released from vegetation in the fall may

32

compared to those without osmoticum as expected. Redox potentials (613 to 629 mV)

were approximately similar in all treatment systems.

which received osmoticum regardless of the equilibrium CRk values. In other words,

“fixed” NH4+ decreased upon the introduction of an osmoticum into the system.

Magnitude of K+ adsorption differed between CRrS within each osmoticum (Table 4). In

the H2O treatment, adsorbed K+ decreased as CRk increased. It was evident from the

above observations that selectivity for K+ was highest at low solution K+ concentration

ratio (K+/(Ca2+)I/2) or CRk- This trend was attributed to soil-site heterogeneity where

highly selective sites for K+ fill up first. Potassium, being a weakly hydrated cation, may

have collapsed the interlayers, leading to NH4+ fixation as well.

The presence of osmotica in the solution phase modified the relationship between CRk-

and adsorbed K+ relationship. In the presence of glucose or mannitol, K+ adsorption

peaked in the mid-CRK range. An apparent trend was noted in the “fixed” NH4+ data.

Soil samples representing the control generally had higher “fixed” NH4+ than those,

The above results were consistent with our earlier findings with respect to glucose (see

Project Report No. 2). In that study, “fixed” NH4+ decreased after a 19-d incubation

period but a large reduction in “fixed” NH4+ was noted in glucose-treated samples. The

x-ray data of the latter soils indicated that the glucose-treated samples displayed a greater

In other words, some “fixed” NH4+ became exchangeable and thus,

33

contribute to the release of “fixed” NH/. We feel that this is important information

which we will use to test if decaying vegetation would release “fixed” NH/.

6. APPENDIX

34

3.3 A

5.0 A-10.0 A 7.2 A 4.2 A3.2 A

' e

0MMTd

Mi

c*•■ •

i b

a Wk

Two-Theta

r

2“T-

23

w cn

"T

6

I

10

I

14I

18

I

28

Appendix Figure 1. X-ray diffractogram for sample S-l (0-30 cm) under different treatments (a = untreated, b = Mg treated,

c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).

3318

J -18.0 A

C 4. . a > *

-1..OA-14OA

5.0 A 4.2 A7.2 A

?_

e

•• I

c

<2

b

-

■)T Tr

18141062

Two-Theta

I

18

>» ■+j « c a> +■> c

w o>



3323 28

3.3 A3.2 A

i

' iiI

----- XJr-.

r jJ. j*

r

-10.0 A

-14.0 A -18.0 A

. - J JU *»

-18.0 A-10.0 A

7.1 A 5.0 A-14.0 A

e

4

c

a

Two-Theta

I

18

I

18

r

2

—r

6

I

23

I

28



I

10

I

14 33

> b

5.0 A7.2 A

Sftasi 1 e1 .•

1

c... •_»:-'

b....—r'"M‘

Two-Theta

—I

18—)

33

[

10

—r

6

>» .-W (Jj c a> +■> c

co00



V--r^4

1428

I

232

18

ft'’

—"<• -'<*''** 11

- .-7h

1 '■».

, “L ■

J

-14.0 A ~1°.o A 7.9 A

18.0 A

-10.0 A22.1 A

-14.0 A 7.1 A 5.0 A

‘ e

d

b

a

Two-Theta

I

18

I

10

I

33r

2

I

14

I

23T

6

Appendix Figure 5. X-ray diffractogram for sample S-2 (0-30 cm) under different treatments (a = untreated, b = Mg treated,


28

c

I

18

CD

3.2 A-14.0 A 7.9 A

3.3 A7.0 A 5.0 A 4.2 A 3.6 A-18.0 A

3.1 A

d

1 f

■Ata c

bb-;

--v""1

a

Two-Theta

c Q>

i

33

i

23r-

2

I

14

k

Appendix Figure 6. X-ray difiractogram for sample S-2 (30-60 cm) under different treatments (a = untreated, b = Mg treated,


T*1.

I.J

1810 286

F

llfo-

-10.0 A

12.7 A

I

18

if

? "i!

/ \

i.

>» -M

-14.0 A

-10.0 A

d

c

Two-Theta

e

~l

3318

I

18

r

2

"T“

6

I

28


c = Mg + Glycerol treated, d = K treated, and e — K + 100° C treated).

10 14

| 16.5 A ' I ' • -

b

I

23

-18.0 A

18.0 A

-14.0 A

-10.0 A 7.1 A 5.0 A

I

V efi

k/ d!

c,z

b

aTrr T

18 2314 182 6

Two-Theta

I

28

I

10

I

33



-

>» IS c

c

15.8 AI I

J

■ ,3^ ,

I

;V B, IK

'A

V b

P1

I

iI ;.f

1 |

/I ft

KJ

-10.0 A 3.6 A

3.2 A

3.1 A

■ AfcJt fori % iijj.

18

Two-Theta

I

10

I

28

I

23

I

6

-14.0 A

-18.0 A



33142

4.2 A

I

18

-14.0 A-10.0 A

c

b

a

62 10 18

Two-Theta

e

d

I

28

I

14



23 33

18.0 A

I

18

-14.0 A

18.0 A

-10.0 A7.1 A 14.2 A5.0 A

Le

b

a

18

Two-Theta

)

18

I

14

I

23

I

33I

10

r

2

cn

>»

w c 0) +-> c

~F

6



28

id

3.1 A

-14.0 A

3.2 A

-18.0 A-10.0 A 7.1 A 5.0 A 4.2 A

3.1A

efi -i

d

‘ c J,-. ■■• -J /!■

b

a

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I

18

—I

33

]

10

I

23

~r

6

]

14

I

28

I

18

-Ucn



2

L

>»

W c M. 0>£

<*.•_ r

fT

Ak r ?

I h • •'

3.6 A 3.3 A

36973285

16323619

1871

C

b

a

30003500 2000 1500

-J

Appendix Figure 13. IR-spectra of S-l (0-30 cm) under different treatments (a = untreated, b - Ca treated,and c = K treated sample).

2500Wavenumbers (cm-1)

,1405

3277

16283694

1875

b

c

3616

a

T

2000 150030003500

-p. oo

Appendix Figure 14. IR-spectra of S-l (30-60 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).


1403

3616

20003500 3000 1500

'-O



3693

3500 2000 1500



3000

36921626

3000 20003500 1500

Appendix Figure 17. IR-spectra of S-2 (0-30 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).


3325

162831441420

1385

a

20003500 15003000

tn



2000 15003000



3500

1624

1866

T

3000 20003500 1500

Ul4^



334536921628

3616

1424b

1873

C

a

T

3500 20003000 1500

Ch th



33691629

b

C

I a

20003500 3000 1500

Ui o



1868

36221626 1431

3366

b

1863

a

cLA

3692

3000T

3500 2000 1500

Appendix Figure 23. JR-spectra of S-3 (60-90 cm) under different treatments (a = untreated, b = Ca treated,

and c = K treated sample).


3394 16263621

b1431

1872

a c

T T

30003500 2000 1500

00


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