Transcript AWPI Meeting, April 27 - CCA Research Homepage

Year 4 Research
Fate of CCA-Treated Wood
Objectives

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)
Note: Complimentary Study on Chromium Speciation
Phase I: Leaching of AlternativeChemical 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 (?)
U
X
CCA,2 CC
CBA
CCA,1 ACQ
X
CBA CCA,2 CDDC CC
ACQ CCA,1CDDC
CC
2
CBA
U
2 ft
CDDC CCA,2
16ft
U
8, 2”x4”x16 ft
were purchased
X

ACQ CCA,1
Sample Processing
1
3 .....8
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

Plan for Leaching

Primary Leaching Tests
 TCLP
 SPLP

Additional Leaching Tests
 Deionized/Distilled
 Synthetic
Seawater
Water
Leaching Tests
Wood
Sample
Size reduced
following standard
leaching protocols
Leaching
Test
18 hour contact,
20:1 Liquid to
Solid ratio,
Rotary extraction
Leachate
Analysis
Leachate analyzed
using standardized
methods
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
Chemicals to be Analyzed
Preservative
Inorganic
Chemical(s)
Organic
Chemical(s)
CCA
As, Cr, Cu
--
ACQ
Cu
DDAC
CBA
Cu, B
Tebuconazole
CDDC
Cu
Dimethyldithiocarbamate
CC
Cu
Citrate
Inorganic Methods
Analytical
Method
ICP-AES
EPA
Method
AWPA
Standard
6010B
A21-93
FLAA
7210
A11-93
GFAA
7211
A11-93
Note: Methods may require extraction or digestion
depending on the matrix or method
Organic Chemical Analysis
Organic
Chemical
Analytical
Technique
DDAC
HPLC,Titration
CDDC
Colorimetric
Tebuconazole
Citrate
HPLC, GC
UV Spec
AWPA Method
(liquids)
A16-A/17-97
A25-94 *
A23-94/A24-94
A2-98
Other Analytical Methods

Citrate by Ion Chromatography
 Dionex

methods manual
Alternative Titration for DDAC
 Manufacturer
suggestion
Proposed Methods

Methods selected based on resources
available, time constraints, and analytical
objectives
Analysis of Inorganic Chemicals

Copper and Boron will be analyzed using
ICP, FLAA, or GFAA following US EPA
methods (including acid digestion).
ICP
Perkin-Elmer 5100 FLAA/GFAA
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 mg/L

Trace 2000 GC/MS
Analysis of DDAC (ACQ)

A two-phase titration analysis will be
performed following method A17-97.
Titration Setup
Analysis of CDDC

Analysis will be performed using a
colorimetric method specified in A25-94 and
instrument methods manual.
Hach DR/4000U
Spectrophotometer
Analysis of Citrate

Analysis will be performed using Ion
Chromatography
Dionex DX-500 Ion
Chromatograph
Chromatogram
Other Possibilities

Toxicity Tests
 MET-plate
 Microtox
 Algal
assay
 Yeast assay
Questions for TAG
Are we missing any analytes of concern?
 Suggestions on methods?
 Comments on leaching tests?

Arsenic:
Toxicity, Mobility & Analytical Methods for
Speciation
Bernine Khan
University of Miami
Outline
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
Speciation
Definition
Various species of an element which make up the total
concentration of that element
- different oxidation states (e.g. arsenic
inorganic - contains sulfur
organic - contains carbon/hydrogen groups
+3, +5, -3)
Speciation
Why are we interested in speciation?
 Not all species are toxic
 Total concentration - over-/under-estimate toxicity
Standards
 EPA’s MCL for DW- 50 mg/L (5 mg/L) As
 TCLP limit - 5000 mg/L
Arsenic Species
Decreasing
Toxicity
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) *
Arsenic Species
Decreasing
Toxicity
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) *
Arsenic Species
Decreasing
Toxicity
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)*
Arsenic Species
Decreasing
Toxicity
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)*
Toxicity Data
LD50
(mg/kg)
Animal
Inorganic arsenite [As(III)]
4.5
rat
Inorganic arsenate [As(V)]
14-18
rat
MMAA - monomethylarsonic
1,800
mouse
DMAA - dimethylarsinic acid
1,200
mouse
TMAO - trimethylarsine oxide
10,600
mouse
AsB - arsenobetaine (marine)
10,000
mouse
AsC - arsenocholine (marine)
6,000
mouse
Arsenic Compound
LD50 - concentration at which 50% of a population dies.
Low LD50 - more toxic
High LD50 - less toxic
Arsenic Mobility
Reducing O2 &
Eh
0.75
As(V)
+5
0.50
Most surface
waters
measure of system
state (aerobic/
anaerobic)
As(III)
+3
0.25
Eh (volts)
Eh-pH diagram
Most ground
waters
0
AsS
+3
-0.25
As(III) - Oxidized
As(V) - Reduced
Methylation
-0.50
As(III)
+3
-0.75
As
AsH3 (aq)
0
2
4
6
8
pH
10
12
14
Part II
Arsenic Speciation Study
Hyphenated techniques
Separation + detection methods
Separate As(III) and As(V) from interfering
ions
Detection methods -
detect & quantify
Purpose 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
Leaching Study
(Warner et al. 1990)
Arsenic leaching increases linearly with decreasing pH
Arsenic after 40 days - retention of 1.99 kg/m3 in new wood
Buffer
citric acid/NaOH
citric acid/NaOH
citric acid/NaOH
citric acid/NaOH
distilled water
borax/HCl
pH
2.5
3.5
4.5
5.5
7.0
8.5
% As
68
52
32
17
9
Buffer
H2SO4
H2SO4
H2SO4
pH
2.5
3.5
4.5
% As
40
23
17
Goals for Year 4
Current 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
Current Study
Silver Diethyldithiocarbamate
(SDDC) Method
20
10
5 2
ug
1
0
Results of SDDC Methods
Arsenite [As(III)]
Conc. (mg)
Absorbance
Conc. (mg)
Absorbance
20
0.185
20
0.17
10
0.082
10
0.072
5
0.038
5
0.05
2
0.03
2
0.02
1
0.018
1
0.018
0
0.009
0
0.009
As(III) Calibration Curve
0.2
+ 0.0057
y = 0.0086x
0.18
2
0.9846
R =0.16
Absorbance
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
0
5
10
15
Concentration (ug)
20
25
Results of SDDC Methods
Arsenate [(As(V)]
Conc. (mg)
Absorbance
Conc. (mg)
Absorbance
20
0.24
20
0.24
10
0.15
10
0.142
5
0.078
5
0.08
2
0.04
2
0.037
1
0.02
1
0.03
0
0.009
0
0.015
As(V) Calibration Curve
0.3
0.25
Absorbance
y = 0.0113x + 0.0189
R2 = 0.2
0.9951
0.15
0.1
0.05
0
0
5
10
15
Concentration (ug)
20
25
Goals 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
Speciation of Chromium
Chromium Speciation

Background

Methods of Analysis

Proposed Methodology
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 Chromium
Species: CrO42-, Cr2O7-
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)

Difference between Cr(VI) and Cr(III)
Factored into Regulations
RCRA Regulations
40 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…..
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.

Ingestion:
 Cr(III):
78,000 mg/kg
 Cr(VI):
390 mg/kg
Cr(III) versus Cr(VI)
Hexavalent chromium exists in alkaline,
strongly oxidizing environments
 Trivalent chromium exists in moderately
oxidizing and reduced environments

Eh (V)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Cr2O7 -
Cr 3+
CrO4 2Cr2O3
-0.2
-0.4
-0.6
0
2
4
6
8
pH
10
12
14
Eh (V)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Cr2O7 -
Cr 3+
CrO4 2Cr2O3
-0.2
-0.4
-0.6
0
2
4
6
8
pH
10
12
14
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)

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
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
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
Methods of Cr(VI) Analysis
Solvent extraction followed by total
chromium analysis
 Colorimetric Determinations
 Chromatographic Determinations

Selected Method

Ion Chromatography
Research Project:
Assessing the Impact of Chromium in the
Environment

Funding provided by Florida Department of
Environmental Protection
Tasks
1. Literature Review
2. Assessment of pH and ORP as
indicators or Cr speciation
3. Evaluate kinetics of conversion of
Cr(VI) to Cr(III) in natural soils
4. Develop guidance document
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
Previous Research

In year 2, wood ash containing CCA-treated
wood was found to leach chromium in an
unpredictable manner (relative to arsenic)
an
W
oo
d
0.
25
pc
f
0.
6
pc
f
2.
5
pc
W
ea
f
th
er
ed
C
&
D
1
C
&
D
2
C
&
5% D 3
C
C
5% A a
C
C
A
b
le
C
Arsenic Leachate Concentration (mg/l)
Arsenic Leaching from Wood Ash
1000
100
TCLP
SPLP
10
0.1
0.01
TC (5)
1
GWCTL
(0.05)
5%
C
D
D
D
b
a
3
2
1
100
CA
CA
C&
C&
C
pc
f
er
ed
C&
ea
th
2.
5
pc
f
pc
f
oo
d
0.
6
5%
W
W
0.
25
Cl
ea
n
Chromium Leachate Concentration (mg/l)
Chromium Leaching from Wood Ash
TCLP
SPLP
10
TC (5)
1
0.1
GWCTL
(0.10)
Questions