The Oxidation of Arsenite by Aquatic Sediments

Sediments from five lakes in southern Saskatchewan, Canada, oxidize As(III) (arsenite) to As(V) (arsenate). The oxidation is not affected by flushing N2 or air through the sediment suspensions, nor does the addition of HgCl2 to the system eliminate the conversion of As(III) to As(V). The oxidation is an abiotic process with microorganisms playing a relatively minor role in this system. Because As(III) is more toxic and sorbed to a lesser extent by sediments than As(V), the suspended and bottom sediments may potentially alleviate the toxicity of As(III) through abiotic oxidation in aquatic environments.