Predicting arsenic solubility in contaminated soils using isotopic dilution techniques.

Tye, A. M. and Young, S. D. and Crout, N. M. J. and Zhang, Hao and Preston, S. and Bailey, E. H. and Davison, William and Mcgrath, S. P. and Paton, G. I. and Kilham, K. (2002) Predicting arsenic solubility in contaminated soils using isotopic dilution techniques. Environmental Science and Technology, 36 (5). pp. 982-988. ISSN 0013-936X

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An isotopic dilution assay was developed to measure radiolabile As concentration in a diverse range of soils (pH 3.30−7.62; % C = 1.00−6.55). Soils amended with 50 mg of As kg-1 (as Na2HAsO4·7H2O) were incubated for over 800 d in an aerated “microcosm” experiment. After 818 d, radiolabile As ranged from 27 to 57% of total applied As and showed a pH-dependent increase above pH 6. The radiolabile assay was also applied to three sets of soils historically contaminated with sewage sludge or mine-spoil. Results reflected the various geochemical forms in which the arsenic was present. On soils from a sewage disposal facility, radiolabile arsenate ranged from 3 to 60% of total As; mean lability was lower than in the equivalent pH range of the microcosm soils, suggesting occlusion of As into calcium phosphate compounds in the sludge-amended soils. In soils from mining areas in the U.K. and Malaysia, radiolabile As accounted for 0.44−19% of total As. The lowest levels of lability were associated with extremely large As concentrations, up to 17 000 mg kg-1, from arsenopyrite. Soil pore water was extracted from the microcosm experiment and speciated using “GEOCHEM”. The solidsolution equilibria of As in the microcosm soils was described by a simple model based on competition between HAsO42- and HPO42- for “labile” adsorption sites.

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Journal Article
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Environmental Science and Technology
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20 Jan 2009 09:52
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18 Sep 2023 00:08