Arsenic speciation in contaminated urban waters, Accrington (UK) using IC-ICP-MS

A hyphenated ion chromatography-ICP-MS technique has been developed to determine aqueous speciation of arsenic and applied to a study of arsenic behaviour in a contaminated urban waterway in NW England. The waters studied are subject to point source industrial discharges of inorganic arsenic resulting in total arsenic concentrations reaching several hundred mug l(-1). Waters immediately below the discharge during relatively dry conditions in April 2000 were found to contain arsenic concentrations of up to 140 mug l(-1) exclusively as inorganic arsenic and with As(V)/mu Sigma As similar to 0.6. Upon mixing with a relatively arsenic free tributary, not only were total arsenic concentrations found to decrease markedly but the As(V)/Sigma As ratio also decreased to below 0.3. The variation in As(V)/Sigma As ratio is due to the preferential adsorption of As(V) on iron oxyhydroxide-rich sediment observed downstream of the confluence of the two streams.