The contamination of environment and water resources by Selenium (Se) and its oxyanions from various sources are emerging contaminants of significant health and environmental concern. The primary sources include agricultural drainage water, mine drainage, residues from fossil fuels, thermoelectric power plants, oil refineries, and metal ores. Various methods and technologies have been developed which focus on the treatment of selenium-containing waters and wastewater. High concentrations of selenium in water cause various adverse impact to human health, such as carcinogenic, genotoxic, and cytotoxic effects. But in the lower concentrations, it is a useful constituent of the biological system. The range between toxicity and deficiency of selenium is minimal (40 to 400 μg per day), due to its dual nature. Selenium Contamination in Water contains the latest status and information on selenium’s origin, its chemistry and its toxicity to humans. The book represents a comprehensive and advanced reference book for students, researchers, practitioners, and policymakers in working in the field of metalloids, in particular selenium. A special emphasis is given on its geological distribution, monitoring techniques, and remedial technologies. As such, the authors critically analyze the various techniques used for the monitoring and removal of selenium from water. Featuring chapters arranged according to the major themes of the latest research, with specific case-studies from industrial experiences of selenium detection and removal, Selenium Contamination in Water will be particularly valued by researchers, practitioners, and policymakers in working in the field of metalloids including selenium.

Selenium concentration and speciation [Se (VI), Se (IV) and Se ( -II)] was determined along a flow path in the Carrizo Sand aquifer (southeastern Texas). Groundwater sampling was carried out in March 2006, from ten wells located along the flow path. The collected samples were filtered through 0.45 mum filters and then acidified to pH 2 using ultra pure HCl. Analysis for Se concentration and speciation was done using selective hydride generation - Atomic Absorption spectrometry (HG-AAS). Additional in situ measurements from each well included determination of pH, alkalinity, oxidation-reduction potential (Eh in mV), dissolved iron speciation, dissolved sulfide concentrations and dissolved manganese concentrations. Selenium concentrations in groundwaters of the Carrizo Sand aquifer are very low (i.e., nanomolal concentrations). Variations in redox condition and geochemical processes appear to exert important controls on the distribution of Se species in Carrizo groundwaters. Redox conditions fluctuate between oxic to mildly reducing environment, in regions proximal to the recharge zone (i.e. & sim;0-15 km). Downgradient at a distance of 15-41 km, Fe (III) reduction is the dominant process, which is followed by sulfate reduction dominating at a distance41 km along the flow path. Se (VI) and Se ( -II) show variable behavior in regions near the recharge zone, whereas Se (IV) dominates in this region. (Abstract shortened by UMI.).