Conversion, sorption, and transport of arsenic species in geological media

This work addresses the inter-conversion and sorption of inorganic As species in representative geological media. Through the sensitive quantification of As(III) and As(V) with liquid chromatography–inductively coupled plasma-mass spectrometry, and through integrated batch and column approaches, it is shown that natural media can either reduce or oxidize As species. Oxidation of As(III) to As(V) is shown in the Hanford sediment, while reduction of As(V) to As(III) is shown for the surface soil of Savannah River Site. Overall, the sorption distribution coefficient of As(V) onto geological media is much larger than that of As(III), and a reduction of the more sorptive As(V) to As(III) will lead to groundwater enrichment with As. Coupled with the different sorption behavior of As(III) and As(V), the inter-conversion of these species will strongly affect the geochemical cycling of redox-sensitive As in the subsurface.