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Träfflista för sökning "WFRF:(Lazaro C) srt2:(2002-2004)"

Sökning: WFRF:(Lazaro C) > (2002-2004)

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2.
  • Oliveira, Lazaro J., et al. (författare)
  • Mercury behavior in a tropical environment – the case of small scale gold mining in Poconé, Brazil.
  • 2004
  • Ingår i: Environmental Practice. ; 6, s. 13-26
  • Tidskriftsartikel (refereegranskat)abstract
    • An estimated 50 tons of mercury (Hg) have been emitted by goldminers in the Bento Gomes river basin, in the municipality ofPocone´, Brazil, since the 1980s. Since the mid-1990s, the stateagency for environmental protection, FEMA (Fundac¸a˜o Estadualdo Meio Ambiente de Mato Grosso), has enforced regulations toreduce Hg emissions to air and water and has also implementedan environmental assessment program. The objectives of thisstudy were to evaluate efforts to reduce emissions of Hg to airand water from nine improved amalgamation centers, and toassess the pollution level in sediment at 25 sites around Pocone´.In spite of the fact that retorts were used, results showed largeemissions of Hg when burning amalgam, resulting in Hg airconcentrations above the limit for occupational air (50 microg/m3)at all centers except one. Keeping washing water in closedsystems and dumping residues in specially prepared sitesreduced Hg emissions to watercourses. The average Hgconcentration of fine sediments (<74 microm) in the Bento Gomesriver basin was 104 ng Hg/g dry weight, three to four timeshigher than the background level; large amounts of Hgcontaminated sediments are re-suspended during the rainyseason. In conclusion, present emissions to local watercourseshave been efficiently reduced, but the use of retorts in improvedamalgamation centers has not adequately reduced Hg emissionsto air, which is why the use of Hg remains an occupational andenvironmental problem.
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3.
  • Wolpher, Henriette, et al. (författare)
  • Will the power plant at Rio Manso, Brazil, cause elevated mercury levels of fish and reduced fish populations?
  • 2003
  • Ingår i: Revista Saúde e Ambiente. ; 6:1-2, s. 12-26
  • Tidskriftsartikel (refereegranskat)abstract
    • In newly constructed hydroelectric reservoirs, it has been shown that the mercury concentration in fish rises. This phenomenon is known mainly from studies in the Nothern Hemisphere. In the present study, the background levels of mercury in fish, soil, and sediment in an area of western Brazil were determined before the area was inundated due to the construction of a hydroelectric power plant. Predatory fish from Rio Manso and Rio Casca were analysed for mercury (Hg). The total Hg concentration in the 13 samples ranged between 72 and 755 ng/g w.w. Organic carbon, nitrogen, and sulphur, total Hg, and citrate-dithionite-bicarbonate (cdb) extractable aluminium, iron, and manganese of soil and sediment were also determined to get a better understanding of parameters influencing Hg geochemistry. The average Hg concentrations in soil and sediment were 24.5 and 24.7 ng/g dry weight, respectively, which is within the background levels found in the region. Both sediment and soil were rich in amorphous aluminium and iron oxy-hydroxides. Mercury correlated positively to these in sediments and negatively in soil. A strong positive correlation between mercury and sulphur was found in sediment. Finally, it is discussed how the hydro power plant has influenced the environment and especially the fish population, indicating an acute need of measures to minimize present and future deterioration.
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