Predicting arsenic solubility in contaminated soils using isotopic dilution techniques

A M Tye, S D Young, N M J Crout, H Zhang, S Preston, E H Bailey, W Davison, S P McGrath, G I Paton, K Kilham

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Abstract

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 Na2HAsO4.7H(2)O) 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 soliddouble left right arrowsolution equilibria of As in the microcosm soils was described by a simple model based on competition between HAsO42- and HPO42- for "labile" adsorption sites.

Original languageEnglish
Pages (from-to)982-988
Number of pages7
JournalEnvironmental Science & Technology
Volume36
DOIs
Publication statusPublished - 2002

Keywords

  • TRACE-ELEMENTS
  • LEAD ARSENATE
  • SORPTION
  • GOETHITE
  • CADMIUM
  • BIOAVAILABILITY
  • MOBILITY
  • METALS
  • ZINC

Cite this

Tye, A. M., Young, S. D., Crout, N. M. J., Zhang, H., Preston, S., Bailey, E. H., Davison, W., McGrath, S. P., Paton, G. I., & Kilham, K. (2002). Predicting arsenic solubility in contaminated soils using isotopic dilution techniques. Environmental Science & Technology, 36, 982-988. https://doi.org/10.1021/es0101633