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Complex interactions of As with the environment and its unique chemical properties leads to its global abundance and distribution. Emerging issues related to As contamination is mainly due to its mobilization to natural systems leading to toxicity. Mobility and toxicity of As depends on its concentration and oxidation state in that particular system. Among drinking water sources, ground water is the most potent reservoir of As. Baseline concentration of As is also found in river water and lakes which depends on bedrock lithology, geothermal sources, pH, alkalinity and anthropogenic pollution (Andreae and Andreae, 1989; Lerda and Prosperi, 1996; Nimick, 1998).  Under natural condition highest concentration of As is found in ground water due to the strong water-rock interaction leading to its mobilization and accumulation (Smedley and Kinniburgh, 2002). Airborne As exposure and toxicity is also a potent health concern in various regions of the globe. Around 70% of the global atmospheric As flux comes from the anthropogenic inputs including fossil fuel burning and other industrial emissions (Nriagu and Pacyna, 1988). Natural sources of As in atmosphere include volcanic eruptions, wind erosion, volatilization from soil and marine aerosols. Studies done by Shraim et al. (2003), indicate that urine and hair samples collected from residents near a coal burning site in Changqing (Guizhou, PR China) showed an increased As concentration. Generally due to low As content in the atmosphere (10-5–10-3 mgm3 in unpolluted areas), atmospheric As exposure possesses little threat to living organism compared to the ground water contamination (Finkelman, 1999; WHO, 2001). Plants absorb the necessary ions and nutrients directly from the soil solution. Thus, the concentration and speciation of As compounds in soil solution determines the amount of As present in plant (Onken et al., 1995). In soil, As occurs in both organic and inorganic form, with inorganic arsenite and arsenate in higher concentrations. Inorganic oxyanions of As leaches out from the rocks and sediments containing As minerals. Generally, arsenate species commonly occur under oxidising condition and arsenite species dominating under moderate reducing condition (Deuel et al., 1972; Masscheleyn et al., 1991; Marin et al., 1993). As based pesticides and other pollutants along with microbial activity are the common source of organic As in the soil solution (Woolson et al., 1977; Pongratz et al., 1988; Turpeinen et al.,1999). 

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