Arsenic speciation in surface waters and lake sediments in an abandoned mine site and field observations of arsenic eco-toxicity

Abstract

Abstract The region of Cobalt in Ontario, Canada has been affected by arsenic (As) and trace metals contamination since the early twentieth century due to unconfined dumping of high As-containing tailings. The concentrations of total dissolved As in lakes and streams have exceeded Canadian drinking water quality guidelines. The present study was focused on the examination of conditions that could influence chemical transformations of As(III) to As(V) and As speciation in lakes and stream waters and sediment of this area, as toxicity and mobility differ between different forms of As. Laboratory results showed that the stability of As(III) is strongly influenced by temperature, light, the presence of nitrate and chloride and by pH. The study shows that although total As concentrations were relatively high in the water samples collected in the area, As(V) was the predominant species in almost all water samples, and the most toxic form of As (III) was low, often