Transcript Sludge Puppies Presentation

Derivation of Soil Quality
Criteria Based on
Chemical Speciation of
Pb2+ and Cu2+
S. Sauvé1,2, A. Dumestre1, M. McBride1
and W. Hendershot2
1Cornell
University-Soil Crop and Atmospheric Sciences (NY)
2McGill University-Macdonald Campus (QC, Canada)
(e-mail: [email protected])
Free Ion Activity Model


Metal toxicity is controlled by free metal ion
activity in aquatic systems
In soils, we need to:
– distinguish between soil total metal (insoluble),
solution dissolved concentrations and solution
free metal activity
– quantify the impact of soil pH and soil organic
matter on metal speciation

Bioavailability, mobility and chemical
reactivity depends on the speciation of the
metals present in the soil solution
Pb Distribution
-1
Pb (µg·kg )
Total
Dissolved
Free
1.E+7
1.E+5
1.E+3
1.E+1
1.E-1
pH=5.2 pH=6.9 pH=4.3 pH=7.5
Site
Sauvé S, Dumestre A, McBride M, Hendershot W. 1998. «Derivation of soil
quality criteria using predicted chemical speciation of Pb2+ and Cu 2+ »
Environmental Toxicology and Chemistry 17:1481-1489.
Experimental Soils

Soils from various origins:
– urban, agricultural, orchard, industrial, forest
– from Ithaca (NY), Québec (Can), Denmark and
France


Contamination: pesticides, sewage sludge,
battery recycling and industrial sources
Soil “Totals” by HNO3 digestions, dissolved
metals by GFAAS of 0.01 M KNO3 extracts
and free metal by ion selective electrode
(Cu2+) and differential pulse anodic
stripping voltammetry (Pb2+)
0
0
2
2
4
4
6
8
10
12
3
4
5
6
pH
7
8
9
Pb 5(PO 4)3OH
Pb 5(PO 4)3Cl
PbSO 4
PbHPO 4
PbO
Pb(OH) 2
pCu 2+
pPb2+
Pb2+ and Cu2+ Solubility
6
8
10
12
3
4
5
6
pH
7
8
9
Cu 3(PO 4)2·H2O
Cu 4(OH) 6SO 4
CuO
CuCO 3
Cu(OH) 2
Sauvé S. 1999. «Chemical speciation, solubility and bioavailability of lead,
copper and cadmium in contaminated soils » Ph.D. Dissertation, Department of
Soil, Crop and Atmosphetric Sciences, Cornell University, Ithaca, NY.
Adsorption Model

Assuming competitive binding of H+ and
Me2+ to a deprotonated surface (S):
2
Me  SurH y  MeSur  y  H


with certain assumptions can be simplified to:
2
pMe  a  b  pH  c log10(Metal Total )
• Applied with succes to the soil solution speciation
of Cd2+, Cu2+ and Pb2+
Regressions for Solution
Free Metal Activity
pCu
2
 140
.  pH  170
.  log 10(Total )  3.42
2
R  0.848, p  0.001, N  66
pPb
2
 0.62  pH  0.84  log 10(Total )  6.78
2
R  0.643, p  0.001, N  84
Sauvé S, Dumestre A, McBride M, Hendershot W. 1998. «Derivation of soil
quality criteria using predicted chemical speciation of Pb2+ and Cu 2+ »
Environmental Toxicology and Chemistry 17:1481-1489.
Pb2+, pH and Total Pb
Sauvé S, McBride M, Hendershot W. 1997. «Speciation of lead in contaminated
soils » Environmental Pollution 98:149-155.
Cu2+, pH and Total Cu
Sauvé S. 1999. «Chemical speciation, solubility and bioavailability of lead,
copper and cadmium in contaminated soils » Ph.D. Dissertation, Department of
Soil, Crop and Atmosphetric Sciences, Cornell University, Ithaca, NY.
Soil Solution Free Metal
Activity
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
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Only a very small fraction of the total metal is
free and available for chemical reactions
This free metal fraction can be predicted using
simply soil total metal and pH
A semi-mechanistic model is successful
independently of the soil origin and of the source
of the metal contamination
Soil organic matter can be incorporated into the
regression, soil OM decreases free Cu2+ activity
Bioassay Model
Endpoint  a  parameter  b

where the biological endpoint (yield reduction,
process inhibition etc.) were as reported in the
literature and the parameter was either total soil
Cu or Pb or predicted free Cu2+ or Pb2+, a and b
were fitted by the statistical software
Inhibition
% Inhibition
100
80
R2=0.127
60
40
20
0
1
10
100 1000
-1
Total Pb (mg·kg )
Sauvé S, Dumestre A, McBride M, Hendershot W. 1998. «Derivation of soil
quality criteria using predicted chemical speciation of Pb2+ and Cu 2+ »
Environmental Toxicology and Chemistry 17:1481-1489.
Inhibition
% Inhibition
100
80
R2=0.409
60
40
20
0
12
10
8
2+
Predicted pPb
6
Sauvé S, Dumestre A, McBride M, Hendershot W. 1998. «Derivation of soil
quality criteria using predicted chemical speciation of Pb2+ and Cu 2+ »
Environmental Toxicology and Chemistry 17:1481-1489.
Inhibition
% Inhibition
100
80
R2=0.424
60
40
20
0
12 11 10 9 8 7 6
2+
Predicted pCu
5
Sauvé S, Dumestre A, McBride M, Hendershot W. 1998. «Derivation of soil
quality criteria using predicted chemical speciation of Pb2+ and Cu 2+ »
Environmental Toxicology and Chemistry 17:1481-1489.
Soil Criteria
-1
Soil T otal Content (mg kg )
pH
pPb
2+
5 0 % =8.3
pPb 2 + 2 5 % =9.5
pCu
2+
5 0 % =7.7
pCu 2 + 2 5 % =9.6
5.5
6
6.5
7
177
415
972
2276
7
16
36
84
103
265
684
1766
8
20
52
135
Sauvé S, Dumestre A, McBride M, Hendershot W. 1998. «Derivation of soil
quality criteria using predicted chemical speciation of Pb2+ and Cu 2+ »
Environmental Toxicology and Chemistry 17:1481-1489.
Conclusion



Soil solution free metal activity of Pb2+ and Cu2+
may be predicted using a simple model
Estimated free metal activities are better
predictor of bioavailability than total soil metal
Soil quality criteria and risk assessment must
consider soil pH to reflect its predominant
influence on soil solution chemical speciation
and bioavailability
References

Sauvé S., A. Dumestre, M.B. McBride and W.H. Hendershot. 1998. Derivation of soil quality
criteria using predicted chemical speciation of Pb2+ and Cu2+. Environmental Toxicology and
Chemistry 17:1481-1489.

Sauvé S., M.B. McBride and W.H. Hendershot. 1997. Speciation of lead in contaminated soils.
Environmental Pollution. 98:149-155.

Sauvé S., M.B. McBride, W.A. Norvell and W.H. Hendershot. 1997. Copper solubility and
speciation of in situ contaminated soils: Effects of copper level, pH and organic matter. Water, Air
and Soil Pollution. 100:133-149.

Sauvé S., M.B. McBride and W.H. Hendershot. 1998. Soil solution speciation of Pb2+: Effects of
organic matter and pH. Soil Science Society of America Journal 62:618-621.

Sauvé S., M. McBride and W. Hendershot. 1998. Lead phosphate solubility in water and soil
suspensions. Environmental Science and Technology 32:388-393.

McBride M.B., Sauvé S. and W.H. Hendershot. 1997. Solubility control of Cu, Zn, Cd and Pb in
contaminated soils. European Journal of Soil Science 48:337-346.

Sauvé S., M.B. McBride and W.H. Hendershot. 1995. Ion-selective electrode measurements of
copper(II) activity in contaminated soils. Archives of Environmental Contamination and
Toxicology. 29:373-379.