Arsenic bioaccessibility in environmentally important arsenic minerals

The potential risk to humans from incidental ingestion of As-contaminated soil and mine waste is influenced by the mineralogical composition of the As phases present. Using the Solubility Bioaccessibility Research Consortium in vitro assay, simulating gastric conditions, we determined the oral bioaccessibility of As in 16 environmentally important As mineral(oid)s commonly found in mine waste and contaminated soils. Our results revealed a wide range of bioaccessibility values closely related to the solubility of the mineral(oid)s. Bioaccessibility values ranged from 0.15 % in minerals with great environmental stability such as scorodite and pharmacosiderite, to complete (100 %) release from minerals such as adamite, erythrite and pharmacolite. Intermediate bioaccessibility levels were observed in minerals such as arsenolite and yukonite, ranging from 6 % to 67 %. In mixtures with soil, the bioaccessibility of As in mineral(oid)s with low solubility was significantly reduced, with bioaccessibility values up to 8.7 times lower due to the effective adsorption of As by the soil. We conclude that the bioaccessibility of As in natural soil and mine waste is intricately influenced by both the mineralogical composition of As phases and the As retention capacity of natural materials under acidic conditions of gastric fluids.