Laserfiche WebLink
SELENIUM IN SELENIFEROUS ENVIRONMENTS 19 <br />are seldom > 500 mg Se/kg. Values range from < 1 to nearly 300 mg Se/kg <br />in the Cretaceous black shales in Wyoming (NAS-NRC, 1983). Approximately <br />2 mg Se/kg occurs in the Cretaceous Pierre and related shales, which are <br />the parent material for much of the seleniferous soil in the northern Great <br />Plains of the USA and the Prairie region of Canada. These seleniferous soils <br />may have higher concentrations of Se in the subsoil because of chemical <br />weathering. Shales are also the principal sources of Se-toxic soil in Ireland, <br />Australia, Israel, and several other countries of the world (Abuereish & <br />Lahham, 1987; Anderson et al., 1961; Lakin, 1948; Rosenfeld & Beath, 1964; <br />Swaine, 1955; NAS-NRC, 1983). <br />The relatively high concentration of Se in some phosphate rocks (Rader <br />& Hill, 1935), particularly western phosphates (1-178 mg Se/kg), is signifi- <br />cant because of the wide use of phosphate fertilizers. Robbins and Carter <br />(1970) suggested that normal superphosphate can be expected to retain about <br />60070 and concentrated superphosphate about 40070 of the Se found in the <br />original rock. The decrease in the Se concentration results from volatiliza- <br />tion and loss of some Se during the smelting process. <br />Coal often contains from 1 to 20 mg Se/kg, although some coal from <br />the People's Republic of China has > 1000 mg Se/kg (O.E. Olson, 1986, <br />personal communication). Upon combustion, coal releases large amounts of <br />Se into the ecosystem. This topic will be covered in more detail later in this <br />chapter. Crude oil also contains Se. Ellrich et al. (1985) measured the Se and <br />S concentrations in 45 crude oils of southern West Germany and reported <br />a range of 0.02 to 0.2 mg Se/kg. The Se and S values were highly correlated. <br />There are no known ore deposits sufficiently high in Se to permit min- <br />ing it exclusively. Most commercially available Se is extracted from copper <br />refinery slime along with the recovery of other precious metals (NAS-NRC, <br />1976, 1983). Total production of Se in the world was 1.89 x 106 kg Se in <br />1983, including 200 x 103 kg in the USA (Jensen, 1985). Production by <br />continent was as follows: <br />North America 645 x 103 kg <br />South America 330 <br />Europe 395 <br />Africa 230 <br />Asia 190 <br />Oceana 95 <br />Selenium is used in the manufacture of batteries, glass, and electronic equip- <br />ment, and as a reagent in remedies for eczema, fungus infections, antidan- <br />druff products, veterinary therapeutic agents, injectables, feed additives, and <br />fertilizers. The demand for fertilizer Se may exceed 28 x 103 kg by 1990 <br />(Korkman, 1985). <br />SELENIUM IN SOIL <br />The concentration of Se in most soils lies within the range of 0.01 to <br />2 mg Se/kg. However, high concentrations of up to 1200 mg Se/kg total <br />