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Evaluation of mercury methylation in fresh and pre dried sediments using ^(2.3)Hg radioisotope

Journal of Environmental Sciences 2000年第S1期12卷 66-75页

作者： J.R.Ikingura 1, H.Akagi 2. J.R.D.Guimaraes 3 (1. University of Dar es Salaam, P.O.Box 35052. Dar es Salaam, Tanzania 2. nat. inst. for minamata disease, 4058 hama,{2., 867 kumamoto, japan 3. Lab. de Radioisotopos, Universidade Federal Do Rio

Mercury methylation rates in fresh and pre dried river sediments were determined in sediment water systems spiked with 2.3 HgCl 2.at a level of 0.75—0.95 ppm as Hg. At the end of the incubation period (2.—38 days), methylmercury production in the fresh sediments was in the order of 3.0% to 13.75%, whereas in the pre dried sediments the methylation was much lower, at 0.6% to 3.9%. The highest methylation levels were generally recorded in the uppermost, 1 cm layer of the sediment column. Total mercury concentration in water in equilibrium with the 2.3 Hg spiked fresh sediments was in the range of 44.7 to 634 ng/L, whereas in equilibrium with the pre dried sediments the concentration was in the range of 19.5 to 34.5 ng/L. The proportion of methylmercury to total mercury in the water varied from 9.4% to 66.6% over the fresh sediments, and from 7.1% to 10.8% over the pre dried sediments. In the system consisting of water, sediment and sediment inverterbrates the concentrations of methylmercury were 8.61 to 15.69 ng/g in the sediment, 0.011 ng/ml in the water, and 9.2. to 40.69 ng/g in the inverterbrates. Methylmercury bioaccumualtion factors (BAFs) were in the order of 2.4 to 8087 relative to the water, and 0.2. to 7.31 relative to the sediment. These results provide further evidence for the tendency of methylmercury to accumulate in high concentrations in aquatic organisms, even at very low total mercury concentration in water.

关键词： mercury methylation rate methylmercury partitioning tropical river sediment

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Exposure of aboriginal people to methylmercury due to gold mining in the Amazon, Brazil

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Journal of Environmental Sciences 2000年第S1期12卷 45-50页

作者： Hirokatsu Akagi 1, Koichi Haraguchi 1, Yoshihide Kinjo 1, Olaf Malm 2. Fernando J. P. Branches 2. Jeans R. J. Guimaraes 2.(1.nat.onal inst.tute for{2. disease,{2., kumamoto 867, japan 2. inst.tute de Biofisica Carlos Chagas Filho,

This paper outlines the results of our study aiming at evaluating the actual extent of human exposure to Hg mainly in Tapajos River Basin in central Amazonia, which is considered to be the oldest and most productive gold mining area in the Amazon. Human hair and blood as well as fish samples were collected from gold mining areas and various fishing villages located at different distances from main gold mining areas, and analyzed for total mercury(T Hg) and methylmercury (MeHg) with new methods recently being developed in our laboratory. The results to date showed the inhabitants of fishing villages particularly in the upstream Tapajos areas were constantly exposed to MeHg at abnormally high levels, with little confounding exposure to inorganic Hg. A highly significant correlation between Hg in hair and blood was observed in fishing villages, and the ratios of hair Hg to blood Hg were very close to 2.0g, generally established for MeHg. While, the levels of MeHg in hair and blood of gold miners and goldshop workers were low, indicating that they were mainly exposed to Hg in inorganic form. From these data, together with the levels of MeHg in fish, Hg contaminat.on mechanisms are discussed.

关键词： methylmercury pollution human exposure gold mining Amazon

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