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Selenium: Environmental significance, pollution, and biological treatment technologies
Published in Lea Chua Tan, Anaerobic treatment of mine wastewater for the removal of selenate and its co-contaminants, 2018
L.C. Tan, Y.V. Nancharaiah, E.D. van Hullebusch, P.N.L. Lens
Selenium is furthermore a raw material used for the vulcanization of rubbers to increase abrasion resistance and a toner agent for photographic prints. For agricultural uses, sodium selenite is used as an additive for fertilizer, insecticides and foliar sprays. Moreover, selenium can also form covalent bonds with many other elements and through this, can detoxify toxic metals such as mercury and arsenic (Rosen and Liu 2009). Selenium supplements can alleviate mercury poisoning by increasing mercury excretion and can also decrease biomarkers related to oxidative stress in humans (Sears 2013). This is because selenium is a mercury chelator and able to form extremely stable compounds or organic complexes with mercury. Another study by Siscar et al. (2013) on the liver of deep-sea fish further observed that a higher Se concentration is required relative to the mercury concentration in order to lower the mercury toxicity.
Minerals
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
Gypsum is formed chiefly by the evaporation of salt water in shallow inland seas, the calcium sulphate in solution being precipitated, as at the southern end of the Dead Sea; extensive deposits of Permian age, hundreds of metres thick, are worked at Stassfurt in Germany. Gypsum is also formed by the decomposition of pyrite (FeS2) in the presence of calcium carbonate, e.g. crystals of selenite found in the London Clay are due to this reaction. Gypsum is much used in the building industry in the manufacture of plasters and plasterboard, and as a retarder of cement. Selenite is the transparent variety of gypsum. Alabaster is white or pink massive gypsum; and the form known as satin-spar is composed of silky fibres, occurring in veins.
Effects of selenium on the uptake of toxic trace elements by crop plants: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Muhammad Rizwan, Shafaqat Ali, Muhammad Zia ur Rehman, Jörg Rinklebe, Daniel C. W. Tsang, Filip M. G. Tack, Ghulam Hasan Abbasi, Afzal Hussain, Avanthi Deshani Igalavithana, Byung Cheon Lee, Yong Sik Ok
In the environment, Se exists in inorganic and organic forms (Gupta & Gupta, 2017; Natasha et al., 2018). The inorganic forms of Se include selenite (HSeO3− and SeO32−, oxidation state IV), selenate (SeO42−, VI), selenide (HSe−, II), and elemental Se (0). Common organic forms of Se in biological matter include methylated selenium compounds, selenoamino acids, and selenoproteins. Selenate, the most soluble species, is predominant in aerobic conditions (pH + pe > 15) in most arable soils, whereas selenite dominates in anoxic environments (pH + pe = 7.5–15), such as paddy soils (Fordyce, 2013; Pilbeam et al., 2015; Wang et al., 2017). Selenate is comparatively more mobile in soil solution than selenite. Furthermore, selenide species of Se are stable under acidic environments and are uncommon in cultivated soils.
Selenium in soil-microbe-plant systems: Sources, distribution, toxicity, tolerance, and detoxification
Published in Critical Reviews in Environmental Science and Technology, 2022
Anamika Kushwaha, Lalit Goswami, Jechan Lee, Christian Sonne, Richard J. C. Brown, Ki-Hyun Kim
Globally, the annual commercial production of Se is projected to reach approximately 2.5 × 103 to 2.8 × 103 tons, with Canada, Germany, Japan, and Belgium the main producers (Mehdi et al., 2013). According to the US Geological Survey (2017), various forms of Se are produced globally and used widely in different industries. Metallurgy consumes 40% of the global supply, glass industries 25%, pigment and chemical industries 10%, electronics 10%, agriculture sector 10%, and other applications 5%. Se is used to manufacture semiconductors and photoelectric cells due to its optical-electrical properties (Macaskie et al., 2010). The precise combination of Se and other metals (e.g., cadmium and tellurium) in such products determines their photoelectric properties, yielding sensors used for military and industrial applications, including photovoltaic solar cells and safety shields for high-energy light sources (Kapoor et al., 1995). Se is photovoltaic and photoconductive, i.e., increase in electrical conductivity with light intensity (Stillings, 2017). Researchers have made a relatively inexpensive material by embedding Se in zinc oxide in a form that offers promising properties for solar power conversion (American Institute of Physics, 2010). It is also used as an accelerator and vulcanizing agent in the rubber industry, improving rubber products' resilience by increasing their resistance to heat, oxidation, and abrasion. It can be used as a catalyst to hydrogenate or dehydrogenate organic compounds, crude oil, and coal and is employed to produce edible fats, plastics, soaps, and waxes. It also provides antioxidant properties to inks and oils and nondrying properties to linseed, tung, and oiticica oils (Stillings, 2017). Se sulfide is used in anti-dandruff shampoos (Sanfilippo & English, 2006). In the agriculture sector, sodium selenite is used as an additive for fertilizers, insecticides, and foliar sprays (El-Ramady et al., 2015). In addition to its agricultural and industrial applications, Se has been used as an animal and human dietary supplement.