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DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING
Citation:
Impellitteri**, C A., H. E. Allen, AND W. G. Peijnenburg. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING. Second Annual Symposium on Natural Organic Matters in Soils and Water, North Central Region, Columbus, OH, 3/19-20/2001.
Description:
Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), and humic acids (HA). Absolute concentrations and relative percentages of DOC fractions were calculated as a function of pH. The soils were also anlayzed for solid phase total organic carbon (boat sampler) and toal recoverable metals (EPA Method 3051). Partitioning coefficients wqere calculated for the metals and organic carbon (OC) by dividing the solid phase concentrations by the solution concentrations. Cu and Pb concentrations in solution as a function of extract equilibrium pH tended to be greatest at low and high pH resulting in parabolic desorption/dissolution curves. The increased soluble concentrations of Cu and Pb at higher pH positively correlated with and increase in DOC with increasing pH. For Zn and Cd, the desorption/dissolution pattern shows high solution concentrations at low pH with no increase at higher pH. While the absolute concentrations of all three operationally defined fractions of OC generally increase with increasing pH, the relative percent increase is greatest for HA. Correlation analysis strongly suggests that HA plays a major role in increrasing the concentration of solution Cu and Pb at higher pH values (pH>6). The FA fraction is consistently present over a wide pH range. Thus, in more acidic environments, FA is probably more important than HA in governing organo-metallic interactions.