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Transcript of Year 4 Research Fate of CCA-Treated Wood n Evaluate Fate of Wood Treated With Preservative Chemicals...
![Page 1: Year 4 Research Fate of CCA-Treated Wood n Evaluate Fate of Wood Treated With Preservative Chemicals ä Evaluate CCA- and alternative-chemical- treated.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649e1b5503460f94b090ab/html5/thumbnails/1.jpg)
Year 4 Research
Fate of CCA-Treated Wood
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Evaluate Fate of Wood Treated With Preservative Chemicals Evaluate CCA- and alternative-chemical- treated
wood through TCLP and SPLP (Phase I) Evaluate arsenic species in leachates collected from
landfills(Phase II)
Objectives
Note: Complimentary Study on Chromium Speciation
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Phase I: Leaching of Alternative-Chemical Treated-Wood Products
Samples Include ACQ-Treated Wood CBA “ “ CC “ “ *** CDDC “ “ CCA “ “ Treated Through Facility A CCA “ “ Treated Through Facility B Untreated Wood Unknown Treated Wood (?)
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Sample Processing
8, 2”x4”x16 ft were purchased
AC
Q
AC
Q
AC
QC
BA
CBA
CBA
CC
A,1
CC
CC
CC
CD
DC
CD
DC
CD
DC
CC
A,1
CC
A,1 C
CA,
2
CC
A,2
CC
A,2
U
U
U
X
X
X
16ft
1 2 3 .....8
2 ft
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Analytical Methods for Alternative Chemicals
Description of Leaching Test Plan Review of existing methods for analysis
of alternative chemicals(AWPA, EPA, and others)
Proposed methods of analysis Questions for TAG
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Plan for Leaching
Primary Leaching Tests TCLP SPLP
Additional Leaching Tests Deionized/Distilled Water Synthetic Seawater
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Leaching Tests
Wood Sample
Size reducedfollowing standardleaching protocols
Leaching Test
18 hour contact, 20:1 Liquid to Solid ratio, Rotary extraction
Leachate Analysis
Leachate analyzedusing standardizedmethods
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Methods of Analysis
Sources of methods: AWPA Standards EPA Methods Instrument Manufacturer Methods Other
Methods are often matrix specific The matrix of interest in the this study is
aqueous leaching fluid
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Chemicals to be Analyzed
CC
CCA
ACQ
CBA
CDDC
As, Cr, Cu
Cu
Cu, B
Cu
Cu
--
DDAC
Tebuconazole
Dimethyldithio-carbamate
Citrate
PreservativeInorganicChemical(s)
OrganicChemical(s)
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Inorganic Methods
ICP-AES
FLAA
GFAA
6010B
7211
7210
A21-93
A11-93
A11-93
AnalyticalMethod
EPAMethod
AWPAStandard
Note: Methods may require extraction or digestiondepending on the matrix or method
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Organic Chemical Analysis
Citrate
DDAC
CDDC
Tebuconazole HPLC, GC
Colorimetric
HPLC,Titration
UV Spec
A16-A/17-97
A25-94 *
A23-94/A24-94
A2-98
OrganicChemical
AnalyticalTechnique
AWPA Method(liquids)
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Other Analytical Methods
Citrate by Ion Chromatography Dionex methods manual
Alternative Titration for DDAC Manufacturer suggestion
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Proposed Methods
Methods selected based on resources available, time constraints, and analytical objectives
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Analysis of Inorganic Chemicals
Copper and Boron will be analyzed using ICP, FLAA, or GFAA following US EPA methods (including acid digestion).
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ICP
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Perkin-Elmer 5100 FLAA/GFAA
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Analysis of Tebuconazole
A GC/MS will be used for analysis. Based on a modified version of AWPA
method A24-94 Detection limit is approximately 100 g/L
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Trace 2000 GC/MS
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Analysis of DDAC (ACQ)
A two-phase titration analysis will be performed following method A17-97.
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Titration Setup
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Analysis of CDDC
Analysis will be performed using a colorimetric method specified in A25-94 and instrument methods manual.
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Hach DR/4000U Spectrophotometer
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Analysis of Citrate
Analysis will be performed using Ion Chromatography
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Dionex DX-500 Ion Chromatograph
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Chromatogram
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Other Possibilities
Toxicity Tests MET-plate Microtox Algal assay Yeast assay
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Questions for TAG
Are we missing any analytes of concern?
Suggestions on methods? Comments on leaching tests?
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Bernine KhanUniversity of Miami
Arsenic:Arsenic: Toxicity, Mobility & Analytical
Methods for Speciation
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Part I - Characteristics Arsenic Species Arsenic Toxicity Arsenic Mobility
Part II - Arsenic Speciation Study Purpose of Study Goals for Year 4 Hydride Generation Method - SDDC
OutlineOutline
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Definition
Various species of an element which make up the total concentration of that element
- different oxidation states (e.g. arsenic +3, +5, -3)
inorganic - contains sulfur
organic - contains carbon/hydrogen groups
SpeciationSpeciation
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Why are we interested in speciation? Not all species are toxic Total concentration - over-/under-estimate toxicity Standards EPA’s MCL for DW- 50 g/L (5 g/L) As TCLP limit - 5000 g/L
SpeciationSpeciation
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Arsenic SpeciesArsenic Species
AsH3 - arsine (gas)
As(III) - inorganic arsenite
As(V) - inorganic arsenate
MMAA - monomethylarsonic acid
DMAA - dimethylarsinic acid
TMAO - trimethylarsine oxide
AsB - arsenobetaine (marine) *
AsC - arsenocholine (marine) *
Decreasing Toxicity
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Arsenic SpeciesArsenic Species
AsH3 - arsine (gas)
As(III) - inorganic arsenite
As(V) - inorganic arsenate - CCA
MMAA - monomethylarsonic acid
DMAA - dimethylarsinic acid
TMAO - trimethylarsine oxide
AsB - arsenobetaine (marine) *
AsC - arsenocholine(marine) *
Decreasing Toxicity
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Arsenic SpeciesArsenic Species
AsH3 - arsine (gas)
As(III) - inorganic arsenite
As(V) - inorganic arsenate
MMAA - monomethylarsonic acid
DMAA - dimethylarsinic acid
TMAO - trimethylarsine oxide
AsB - arsenobetaine (marine)*
AsC - arsenocholine (marine)*
Decreasing Toxicity
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Arsenic SpeciesArsenic Species
AsH3 - arsine (gas)
As(III) - inorganic arsenite
As(V) - inorganic arsenate
MMAA - monomethylarsonic acid
DMAA - dimethylarsinic acid
TMAO - trimethylarsine oxide
AsB - arsenobetaine (marine)*
AsC - arsenocholine (marine)*
Decreasing Toxicity
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Toxicity DataToxicity Data
Arsenic Compound
Inorganic arsenite [As(III)]
Inorganic arsenate [As(V)]
MMAA - monomethylarsonic
DMAA - dimethylarsinic acid
TMAO - trimethylarsine oxide
AsB - arsenobetaine (marine)
AsC - arsenocholine (marine)
LD50
(mg/kg)
4.5
14-18
1,800
1,200
10,600
10,000
6,000
Animal
rat
rat
mouse
mouse
mouse
mouse
mouse
LD50 - concentration at which 50% of a population dies.Low LD50 - more toxic High LD50 - less toxic
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Arsenic MobilityArsenic MobilityReducing O2 & Eh
As(V)+5
As(III)+3
As(III)+3
AsH3 (aq)
AsS+3
As
Most surface waters
Most ground waters
0 2 4 6 8 10 12 14
pH
Eh (
volt
s)0.75
0.50
0.25
0
-0.25
-0.50
-0.75
Eh-pH diagram
measure of system state (aerobic/ anaerobic)
As(III) - OxidizedAs(V) - ReducedMethylation
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Hyphenated techniques
Separation + detection methods
Separate As(III) and As(V) from interfering ions
Detection methods - detect & quantify
Part IIPart IIArsenic Speciation StudyArsenic Speciation Study
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Purpose of StudyPurpose of Study
• CCA treated wood disposed of in unlined C&D landfills
• Leaching studies show significant amounts of CCA leaching from wood under varying pH solutions
• Determine the total arsenic & individual concentration of As(III) & As(V) species
• Chemical Hydride Generation method
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Leaching StudyLeaching Study(Warner et al. 1990)
Arsenic leaching increases linearly with decreasing pH
Buffer pH %
As
citric acid/NaOH 2.5 -
citric acid/NaOH 3.5 68citric acid/NaOH 4.5
52citric acid/NaOH 5.5
32distilled water 7.0
17borax/HCl 8.5
9
Buffer pH %
As
H2SO4 2.5 40H2SO4 3.5 23H2SO4 4.5 17
Arsenic after 40 days - retention of 1.99 kg/m3 in new wood
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Goals for Year 4Goals for Year 4Current Study:
• Analysis of As(III) & As(V) by Chemical Hydride Generation (CHG) method
• SDDC - CHG method chosen - NaBH4
to reduce arsenic to its gaseous form (arsine) so as to be detected
• SDDC method - Test reproducibility using standard solutions
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Silver Diethyldithiocarbamate (SDDC) Method
Current StudyCurrent Study
20 10 5 2 1 0 ug
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Results of SDDC MethodsResults of SDDC Methods
Absorbance
0.185
0.082
0.038
0.03
0.018
0.009
Conc. (g)
20
10
5
2
1
0
Absorbance
0.17
0.072
0.05
0.02
0.018
0.009
Conc. (g)
20
10
5
2
1
0
Arsenite [As(III)]
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y = 0.0086x + 0.0057
R2 = 0.9846
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 5 10 15 20 25
Concentration (ug)
Ab
so
rba
nc
eAs(III) Calibration CurveAs(III) Calibration Curve
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Results of SDDC MethodsResults of SDDC Methods
Absorbance
0.24
0.15
0.078
0.04
0.02
0.009
Conc. (g)
20
10
5
2
1
0
Absorbance
0.24
0.142
0.08
0.037
0.03
0.015
Conc. (g)
20
10
5
2
1
0
Arsenate [(As(V)]
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y = 0.0113x + 0.0189R2 = 0.9951
0
0.05
0.1
0.15
0.2
0.25
0.3
0 5 10 15 20 25
Concentration (ug)
Ab
so
rba
nc
eAs(V) Calibration CurveAs(V) Calibration Curve
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Goals for Year 4Goals for Year 4
Next Steps:
• Determine how best to preserve sample
• Analyse GW samples near C&D landfills
• Analyse leachate from MSW and C&D(?) landfills
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Speciation of Chromium
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Chromium Speciation
Background
Methods of Analysis
Proposed Methodology
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Chromium Exists as Several Chemical Species
Most common oxidation states: 0, +3, +6
0: Elemental Chromium (Cr)+3: Trivalent Chromium
Species: Cr+3, Cr2O3
+6: Hexavalent ChromiumSpecies: CrO4
2-, Cr2O7-
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Chromium Speciation Important!
The characteristics and properties of trivalent chromium and hexavalent chromium are greatly different.
Cr(VI) is much more toxic and mobile than Cr(III)
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Difference between Cr(VI) and Cr(III) Factored into Regulations
RCRA Regulations40 CFR 261.4(b)(6)(i)
A solid waste that is a characteristic or listed hazardous waste solely because of chromium is not hazardous if…..
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A solid waste that is a characteristic or listed hazardous waste solely because of chromium is not hazardous if…..
– (A) The chromium in the waste is exclusively (or nearly exclusively) trivalent chromium; and
– (B) The waste is generated from an industrial process which uses trivalent chromium exclusively (or nearly exclusively) and the process does not generate hexavalent chromium; and
– (C) The waste is typically and frequently man-aged in non-oxidizing environments.
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Ingestion: Cr(III): 78,000 mg/kg Cr(VI): 390 mg/kg
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Cr(III) versus Cr(VI)
Hexavalent chromium exists in alkaline, strongly oxidizing environments
Trivalent chromium exists in moderately oxidizing and reduced environments
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pH
Eh (V)
10 12 144 6 820
0.0
-0.2-0.4
-0.6
1.0
0.2
0.8
0.4
0.6
1.2
Cr2O3
CrO4 2-
Cr2O7 -
Cr 3+
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pH
Eh (V)
10 12 144 6 820
0.0
-0.2-0.4
-0.6
1.0
0.2
0.8
0.4
0.6
1.2
Cr2O3
CrO4 2-
Cr2O7 -
Cr 3+
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Chromium in Wood Preservation
The chromium in CCA preservative solution is hexavalent chromium.
Upon fixation in the wood, Cr(VI) becomes converted to Cr(III)
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When Might Cr(VI) Be Encountered?
If wood is improperly fixed (as a result, for example, of inadequate fixation time at low temperatures)
When in contact with oxidizing chemicals such as deck brighteners
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Oxidation of Chromium in the Environment
In the natural environment, chromium tends to exist as Cr(III)
Oxidation of Cr(III) to Cr(VI) as a result of manganese (hydr)oxides
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Methods of Cr(VI) Analysis
Typical chromium measurements are total chromium (Cr(III) + Cr(VI) + other)
Methods have been developed for Cr(VI) analysis
Sample holding time is minimal
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Methods of Cr(VI) Analysis
Solvent extraction followed by total chromium analysis
Colorimetric Determinations Chromatographic Determinations
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Selected Method
Ion Chromatography
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Research Project:Assessing the Impact of Chromium in the Environment
Funding provided by Florida Department of Environmental Protection
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Tasks
1. Literature Review2. Assessment of pH and ORP as
indicators or Cr speciation3. Evaluate kinetics of conversion of
Cr(VI) to Cr(III) in natural soils4. Develop guidance document
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Additional Tasks
5. Examine Cr(VI) in ash from combustion of wood containing CCA-treated wood
6. Examination of Cr(VI) formation potential in C&D debris disposal environments
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Previous Research
In year 2, wood ash containing CCA-treated wood was found to leach chromium in an unpredictable manner (relative to arsenic)
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Arsenic Leaching from Wood Ash
0.01
0.1
1
10
100
1000
Ars
en
ic L
ea
ch
ate
Co
nc
en
tra
tio
n (
mg
/l)
TCLPSPLP
TC (5)
GWCTL(0.05)
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Chromium Leaching from Wood Ash
0.1
1
10
100C
hro
miu
m L
each
ate
Co
nce
ntr
atio
n (
mg
/l)
TCLPSPLP
TC (5)
GWCTL(0.10)
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Questions