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Selenium is a metal found in natural deposits as ores containing other elements. At typical groundwater pH values (7.0 to 9.5) only anionic forms of selenious (Se IV) or selenic (Se VI) acid are found. *Maximum Contaminant Level (MCL) — The highest level of a contaminant that is allowed in drinking water.
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Selenium is a priority pollutant and all public water agencies are required to monitor its concentration. 4.3 These test methods determine the dominant species of selenium reportedly found in most natural and wastewaters, including selenities, selenates, and organo-selenium compounds.
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Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust.
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some areas, selenium levels in groundwater may approach 6000 µg/l (Cannon, 1964). Concentrations increase at high and low pH as a result of conversion into compounds of greater solubility in water. Levels of selenium in tap water samples from public water supplies around the world are usually much less than 10 µg/l but may exceed 50
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Selenium compounds are released to the air during the combustion of coal and petroleum fuels, and during the smelting and refining of other metals. From 1987 to 1993, according to the Toxics Release Inventory selenium releases to land and water totaled over 1 million lbs.
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Selenium dioxide is an industrial exposure hazard since it forms selenite, an irritant, with water or sweat. Other selenium compounds released during coal or petroleum combustion may …
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Selenium compounds are released to the air and water in flue gas and fly ash during the combustion of coal and petroleum fuels (e.g. in coal-fired power stations), during the smelting and refining of metals such as copper, lead and zinc, from glass and ceramics manufacturing, and from refuse incinerators.
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The 4 natural oxidation states of selenium are elemental selenium (0), selenide (-2), selenite (+4), and selenate (+6). Inorganic selenate and selenite predominate in water whereas organic selenium compounds (selenomethionine, selenocysteine) are the major selenium species in …
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Selenium Compounds Hazard Summary Selenium is a naturally occurring substance that is toxic at high concentrations but is also a nutritionally essential ... exposed to high levels of selenium in food and water have reported discoloration of the skin, pathological deformation and …
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Selenium and its compounds were also concluded to be harmful to the environment. About these substances. The screening assessment focused on the selenium moiety, and therefore includes all forms of selenium found in commerce and those found in the environment, which are referred to collectively as selenium and its compounds.
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Elemental selenium (14) and selenium sulfide (15) are poorly absorbed. After absorption, water-soluble selenium compounds appear to be rapidly distributed to most organs, the highest concentrations being in kidney, liver, spleen, and testes (16,17). Selenium compounds are biotransformed into excretable metabolites, including unknown as
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As presented in Fig. 2a, the water-soluble fraction of C. violifolia contained only a negligible amount of selenite (48 μg g −1 as Se) that accounts for only 1.3% of total selenium. Also, the SAX-ICP-MS chromatogram indicates that most of the soluble selenium compounds are either cationic or neutral at the pH of the separation (pH 6.0).
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The greatest use of selenium compounds is in electronic and photocopier components, but they are also widely used in glass, pigments. rubber. metal alloys, textiles, petroleum, medical therapeutic agents, and photographic emulsions. ... Some people who drink water containing selenium well in excess of the maximum contaminant level (MCL) for ...
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Selenium in drinking water can come from discharge from mines, natural deposits, dischage from refineries, or from agricultural runoff leaching natural selenium compounds from dry, undeveloped land. What are the Health Effects of Selenium Exposure?
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Selenium sulfide is a pharmaceutical compound used in anti-dandruff shampoos and is very different than the inorganic or organic selenium compounds found in foods and the environment. (1,2,4) a EPA has classified elemental selenium as a Group D, not classifiable as to human carcinogenicity, and selenium sulfide as a Group B2, probable human ...
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Organoselenium compounds (or seleno-organic) are chemical compounds containing carbon-to-selenium chemical bonds. Organoselenium chemistry is the corresponding science exploring their properties and reactivity. Selenium belongs with oxygen and sulfur to the group 16 elements or chalcogens, and similarities in chemistry are to be expected. Organoselenium compounds are found …
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