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TitleEffects of soil composition and mineralogy on the bioaccessibility of arsenic from tailings and soil in gold mine districts of Nova Scotia
AuthorMeunier, L; Walker, S R; Wragg, J; Parsons, M B; Koch, I; Jamieson, H E; Reimer, K J
SourceEnvironmental Science & Technology (ES & T) vol. 44, no. 7, 2010 p. 2667-2674, (Open Access)
Alt SeriesEarth Sciences Sector, Contribution Series 20090357
Mediapaper; on-line; digital
File formatpdf
ProvinceNova Scotia
Subjectsenvironmental geology; soils science; mineralogy; soils; soil studies; soil geochemistry; heavy metals contamination; arsenic; concentration; tailings geochemistry; tailings analyses; tailings; environmental analysis; environmental studies; mineralogical analyses
Illustrationstables; histograms
ProgramEcosystems Risk Mitigation, Environmental Geoscience
AbstractBioaccessibility tests and mineralogical analyses were performed on arsenic-contaminated tailings and soils from gold mine districts of Nova Scotia, Canada, to examine the links between soil composition, mineralogy, and arsenic bioaccessibility. Arsenic bioaccessibility ranges from 0.1% to 49%. A weak correlation was observed between total and bioaccessible arsenic concentrations, and the arsenic bioaccessibility was not correlated with other elements. Bulk X-ray absorption nearedge structure analysis shows arsenic in these near-surface samples is mainly in the pentavalent form, indicating that most of the arsenopyrite (As1-) originally present in the tailings and soils has been oxidized during weathering reactions. Detailed mineralogical analyses of individual samples have identified up to seven arsenic species, the relative proportions of which appear to affect arsenic bioaccessibility. The highest arsenic bioaccessibility (up to 49%) is associated with the presence of calcium-iron arsenate. Samples containing arsenic predominantlyasarsenopyrite or scoroditehavethe lowest bioaccessibility (<1%). Other arsenic species identified (predominantly amorphous iron arsenates and arsenic-bearing iron(oxy)hydroxides) are associated with intermediate bioaccessibility (1 to 10%). The presence of a more soluble arsenic phase, even at lowconcentrations, results in increased arsenic bioaccessibility from the mixed arsenic phases associated with tailings and mineimpacted soils.