Mercury Sources and Release Rates

About 130 tons of Hg is released aimually by alluvial gold mining to the Amazonian 

Natmal sources of mercury and natural bio-geochemical processes contribute heavily to reported elevated mercury concentrations in fish and water samples collected up to 900 km downstream from local gold mining activities. Based on analysis of water, sediments, and fish samples systematically collected along a 900-km stretch of the Madeira River in 1997, it was concluded that the elevated mercury concentrations in samples were due mainly to natural sources and that the effects of mercury released from gold mining sites were localized. This needs to be verified. 

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