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Environ Chem Lett (2015) 13:4958 DOI 10.1007/s10311-014-0487-x
REVIEW
Biogeochemistry of selenium. A review
Virender K. Sharma Thomas J. McDonald
Mary Sohn George A. K. Anquandah
Maurizio Pettine Radek Zboril
Received: 25 September 2014 / Accepted: 21 October 2014 / Published online: 4 November 2014 Springer International Publishing Switzerland 2014
Abstract Selenium levels and speciation in environmental compartments and the dynamics of global Se cycling continue to be a subject of intense interest largely because Se is both an essential element and a toxicant at elevated levels. While Se containing amino acids and proteins are known to be critical for normal metabolic functions in many life forms, selenosis, poisoning due to chronic excessive Se intake, has been associated with neurological impairment. This paper reviews the current understanding of the biogeochemistry of selenium in the natural environment. The factors that affect Se speciation in natural environments are chemical, physical, and biological processes. Several inorganic species of Se (-2, 0, ?4, and ?6) and organic species (monomethylated and dimethylated) have been reported in aquatic systems. Both HSeO3- and SeO32- would be present in natural waters.
Under mild oxidizing conditions, HSeO3- and SeO32- are the major species, while HSe- would be the dominant
species at pH greater than 4 and strong reducing conditions. The biogeochemistry of selenium is discussed in terms of variation of speciation with pH and redox conditions, sorption on solid surfaces, role of reducing species under oxic/anoxic conditions, and interaction with natural organic matter.
Keywords Selenium Speciation Abiotic reduction
Sorption Organic matter
Introduction
Selenium (Se) as an element has been known since 1817 and has been found in all of the earths environmental compartments including the atmosphere, geosphere, hydrosphere, and biosphere. Selenium resembles sulfur chemically and in the geosphere is associated with sulfur deposits and coal (Dauphas 2013; Wang and Becker 2013). The amount of Se found in coal worldwide is approximately 1.01.6 mg Se kg-1, but in some parts of the world, such as the US, Russia, and China, high Se concentrations of up to 43 mg Se kg-1 have been found (Lenz and Lens 2009). In terrestrial systems, minerals are the primary source, but Se is also derived from man-made sources related to its use in a number of industries such as ceramics and...