Lead adsorption to metal oxides and organic material of freshwater surface coatings determined using a novel selective extraction method

Surface coatings were collected in three lakes and a river in China to study the role of the components of natural surface coatings in controlling Pb adsorption. Chemical reagents, 0.02 mol/l NHOH HCl + 0.01 mol/l HNO3, 0.4 mol/l Na2S2O4 and 10% oxalic acid, were employed to extract one or more components from surface coatings, and then Pb adsorption to extracted and unextracted surface coatings was carried out. The observed Pb adsorption to extracted and unextracted surface coatings were analyzed using the nonlinear least squares fitting (NLSF) to estimate the relative contribution of components to the total Pb adsorption. The amounts of Pb absorption to components described by estimated Gamma(max) ranged from 0.1126 to 0.7291 (mol Pb/mol Mn) for Mn, 0.0528 to 0.1927 (mol Pb/mol Fe) for Fe and 0.0196 to 0.1020 (mol Pb/kg COD) for organic material, respectively. In all waters studied, metal oxides contributed most to Pb adsorption with a lesser role indicated for organic material. (C) 2002 Elsevier Science Ltd. All rights reserved.