ABSTRACT
AR SEN IC has been known as a highly toxic element for centuries. Arsenic is ubiquitous in earth’s crust in miniscule amounts, e.g., less than 0.01 % by mass [1]. Orpiment (As2 S3), realgar (AsS) and arsenopyrite (FeAsS) are some of the commonly encountered solid phases in which arsenic exists in subsurface soils [2,3]. Note that sulfur and iron are the two com mon companions of arsenic, and these compounds are formed in subsurface soils under a highly reducing environment. Geochemical or biogeochemical weathering of these solid phases often, if not always, contributes to elevated levels of dissolved arsenic in groundwaters. Historically, anthropogenic sources have also been responsible for discharg ing arsenic in the environment. Arsenic is commercially used to produce arsenical pesti cides, wood preservatives, ceramics, semiconductors and other materials. Mine drainage, smelter wastes and agricultural drainage water have also been found to be responsible for el evated concentrations of As in soil and water [4-6]. Arsenic compounds present in soil and water exist primarily in two oxidation states, namely, (+III) and (+V).
