8153 - Laserfiche WebLink

Home Browse Search

SELENIUM IN SELENIFEROUS ENVIRONMENTS 39 the blood was different, but once absorbed, both chemical forms behaved identically. In a second study, Weissman et al. (1983) used beagle dogs (Canis familiaris) and calculated that the animals absorbed 52 and 73% of the Se from the Se metal and selenious acid aerosols, respectively. In this study the aerosols had 0.7 and 0.5 µm MMAD, respectively. Selenium absorption from the Se° or HZSe03 forms was 73 and 96~a when given by stomach pump and 10 and 50°Io when given in the feed, respectively. Selenium that was absorbed into the blood was translocated to various organs with awhole-body biolog- ical half-life of 34 d. Urine was the major route of excretion, accounting for 70 to 80% of the excreted Se. Atmospheric deposition patterns, based on elemental concentrations in mosses, have been reported in Norway (Rambaek & Steinnes, 1980). More recently, Froslie et al. (1985) measured the trace element concentration in the livers of 6 to 8 month old lambs that had grazed on unfertilized moun- tain pastures at 11 different geographical areas in that country. They reported correlation coefficients for elemental concentrations in liver vs. atmospheric deposition of each element as follows: Pb: 0.94*** Cd: 0.78** Se: 0.73** As: 0.66** Mo: 0.30 Zn: 0.04 Cu: -0.21 These values strongly indicate a relationship between atmospheric deposi- tion of several trace elements, including Se, and intake by grazing animals. The Se intake by the Iambs may not only be due to the metal concentration sorbed by the plants from the atmospheric fallout but could be affected by ingestion of soil (Mayland et al., 1975), since surface soils showed a similar trace element contamination pattern. Froslie et al. (1985) concluded that the Se fallout from aerosol sources over southern and southwestern Norway played a beneficial role in reducing the incidences of Se-deficiency disorders in livestock. Freshwater lakes or other waters may also receive Se by natural cycling processes or as discharges of wastes from irrigation drainage, like that at Kesterson in central California, or from coal-combustion or refuse incinera- tion plants. Soluble Se forms (selenite, selenate) present in the water have a relatively high bioavailability and may be responsible for reduced reproduc- tion (Gillespie & Baumann, 1986) and growth (Sorensen & Bauer, 1984; Soren- sen, 1986) in fish. The Se passes along the food chain from algae to rotifer to larval fish to larger fish and to fish-eating birds and even humans (Ben- nett et al., 1986; Bertram & Brooks, 1986; Gissel-Nielsen &Gissel-Nielsen, 1978; Hodson et al., 1986; Chapter 8 of this publication). This aspect of Se cycling will require persistent monitoring and adoption of management strate- gies to reduce overall risks of Se toxicosis in plants and animals.