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Madeira River Basin is a gold-mining area, where in 1984 about 10 tons of gold were extracted from the river sediment. The gravimetrically separated heavy and fine particles are amalgamated with mercury and gold is recovered by heating the amalgam. Some 5-30% of the mercury is lost during amalgamation, mainly into the river, and 20% is released to the atmosphere by burning. According to a conservative estimate 100 tons of mercury were lost into the environment of the Madeira River between 1979 and 1985. At the outlet of reburning instillations in Porto Velho 292 [micro]g/m3, and in nearby streets 3.2 [micro]g/m3, atmospheric mercury concentrations were measured. At other places atmospheric concentrations were not higher than in Rio de Janeiro. In water, suspended particles, and bottom sediments higher concentrations were measured in forest streams adjacent to the river than in Madeira River itself. Thus the mean [+ or -] smallcap~Ssmallcap~D values in forest streams were 3.05 [+ or -] 4.5 [micro]g/l water, 1.21 [micro]g/g dry weight in suspended particles (only 3 values), and 10.2 [+ or -] 30.3 [micro]g/g dry weight in bottom sediment; in the river these values were 1.56 [+ or -] 2.9 [micro]g/l, 0.50 [+ or -] 0.13 [micro]g/g and 0.13 [+ or -] 0.11 [micro]g/g respectively. [Although these values are high, they are very much lower than in the sediments of Minamata Bay, Japan.] Concentrations in fish ranged from 0.21 to 2.7 [micro]g/g wet weight. There was no noticeable difference between fish caught in the gold-mining area and 180 km downstream. Mercury concentration in hair depended more on eating habit than mining. In a mining area where diet did not include fish, the main hair mercury concentration was 2.4 [+ or -] 2.1 [micro]g/g, whereas in 2 fish-eating mining areas mean concentrations were 4 to 8 times higher with 40 [micro]g/g maximum.newline~Laszlo Magos, https://www.cabdirect.org/cabdirect/abstract/19902070147

Madeira River Basin is a gold-mining area, where in 1984 about 10 tons of gold were extracted from the river sediment. The gravimetrically separated heavy and fine particles are amalgamated with mercury and gold is recovered by heating the amalgam. Some 5-30% of the mercury is lost during amalgamation, mainly into the river, and 20% is released to the atmosphere by burning. According to a conservative estimate 100 tons of mercury was lost into the environment of the Madeira River between 1979 and 1985. At the outlet of reburning instillations in Porto Velho 292 [micro]g/m3, and in nearby streets 3.2 [micro]g/m3, atmospheric mercury concentrations were measured. At other places atmospheric concentrations were not higher than in Rio de Janeiro. In water, suspended particles, and bottom sediments higher concentrations were measured in forest streams adjacent to the river than in Madeira River itself. Thus the mean [+ or -] smallcap Ssmallcap D values in forest streams were 3.05 [+ or -] 4.5 [micro]g/l water, 1.21 [micro]g/g dry weight in suspended particles (only 3 values), and 10.2 [+ or -] 30.3 [micro]g/g dry weight in bottom sediment; in the river these values were 1.56 [+ or -] 2.9 [micro]g/l, 0.50 [+ or -]0.13 [micro]g/g and 0.13 [+ or -] 0.11 [micro]g/g respectively. [Although these values are high, they are very much lower than in the sediments of Minamata Bay, Japan.] Concentrations in fish ranged from 0.21 to 2.7 [micro]g/g wet weight. There was no noticeable difference between fish caught in the gold-mining area and 180 km downstream. Mercury concentration in hair depended more on eating habit than mining. In a mining area where diet did not include fish, the main hair mercury concentration was 2.4 [+ or -] 2.1 [micro]g/g, whereas in 2 fish-eating mining areas mean concentrations were 4 to 8 times higher with 40 [micro]g/g maximum.newline Laszlo Magos, https://www.cabdirect.org/cabdirect/abstract/19902070147