Mineralogic Constraints on the Bioavailability of Arsenic in Smelter-Impacted Soils

Superfund risk assessments and the resulting soil arsenic (As) cleanup levels selected for mining sites are currently based on the toxicity of soluble As in drinking water. However, Anaconda soils and house dusts contain less soluble smelter-related As phases, consisting primarily of metal−arsenic oxides and phosphates. If accidentally ingested, As bioaccessibility is restricted by the sparingly soluble nature of As-bearing phases, the prevalence of authigenic carbonate and silicate rinds, the kinetic hindrance to dissolution, and the inaccessibility of encapsulated As. These limitations to As disolution explain the lower bioavailability factors observed for Anaconda As-bearing soils.