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

Natural attenuation remediation is based on the intrinsic attenuation capac ities 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, oxid ation, or reduction) between arsenic and minerals play an important role in the natural attenuation of arsenic, and could present important pathways f or arsenic cycling in the subsurface environment. Iron oxides and kaolinite s 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 i ndicators for site characterization. Integration of mineralogical and geoch emical indicator parameters would greatly improve the quality of site chara cterization. The current MCL in the USA for arsenic in drinking water may s oon be lowered to 5 mug/L. It is estimated that lowering the arsenic MCL wo uld cost billions of dollars per year. The natural attenuation could be a p otential cost-effective approach for solving the problem of arsenic-contami nated groundwater.