Studies of interfacial reactions between arsenic and minerals and its significance to site characterization

Abstract.

Natural attenuation remediation is based on the intrinsic attenuation capacities of the subsurface. Geochemistry of the subsurface controls the fate, transport, transformation, and bioavailability of contaminants. This paper demonstrates that interfacial reactions (e.g., adsorption, desorption, oxidation, or reduction) between arsenic and minerals play an important role in the natural attenuation of arsenic, and could present important pathways for arsenic cycling in the subsurface environment. Iron oxides and kaolinites were used for this experimental study. Based on the different behavior of minerals, it is suggested that some types of minerals can act as mineral indicators for site characterization. Integration of mineralogical and geochemical indicator parameters would greatly improve the quality of site characterization. The current MCL in the USA for arsenic in drinking water may soon be lowered to 5 µg/L. It is estimated that lowering the arsenic MCL would cost billions of dollars per year. The natural attenuation could be a potential cost-effective approach for solving the problem of arsenic-contaminated groundwater.