Environmental fate of mercury from gold mining in the Brazilian Amazon

Abstract

Large quantities of mercury are being released into the waters of the Amazon and its tributaries by gold-mining activities. Large releases are also taking place into the air. In this paper, the fate of mercury released to the environment by gold mining in the Brazilian Amazon is reviewed. Mercury contamination is presently widespread in the Amazon region. A major source of mercury in the local environment is the burning of the gold–mercury amalgam, which releases from 30 to 150 t of mercury yearly into the Amazon atmosphere. Air samples collected close to mining sites showed extremely high mercury concentrations (up to 7.5 μg∙m−3). Inside gold-dealers' shops or in amalgam-burning stations, ambient air concentrations may reach 100 μg∙m−3. A secondary source is the discharge of metallic mercury into rivers during the amalgamation process. Sediment concentrations frequently range from 0.3 to 3.0 μg∙g−1 in contaminated sites. However, values as high as 19.8 μg∙g−1 have been reported in some sites. Waters of many rivers are also contaminated, although reliable data on dissolved mercury concentrations are still lacking. Local carnivorous fishes typically show mercury concentrations higher than 1.0 μg∙g wet wt.−1 in contaminated sites and methyl mercury represents over 90% of the total content. Human groups with fish-based diets frequently show evidence of mercury contamination, with high mercury concentrations in hair (up to 70 μg∙g−1). However, a reliable epidemiological study on the affected population still has to be carried out.Key words: mercury, gold mining, Amazon, sediments, aquatic biota, humans.

Neurotoxic Effects of Low-Level Methylmercury Contamination in the Amazonian Basin

“…Martinelli et al, 1988;Palheta and Taylor, 1995;Pfeiffer et al, 1989Pfeiffer et al, , 1991Pfeiffer et al, , 1993. Environmental studies in this region suggest that there may be two important sources for mercury contamination.…”

Mercury Removal from Aqueous Solution by Mixed Mineral Systems II. The Role of Solution Composition and Ageing

“…birds, fish, seals, and man, is thereby threatened [2][3] Three forms of non-biodegradable mercury contaminant namely elemental mercury (Hg0), oxidized mercury (Hg 2+ ) and particulate-bound mercury (HgP) exist. The oxidized form of mercury is transformed into its toxic methylated species, transferred and bioamplified as monomethy l merury (MMHg) in the aquatic food chains [4][5][6][7][8][9][10][11][12][13] The major sources of Hg emission worldwide comes from coal combustion and Au amalgamation [14][15][16]. Alluvial Au mining activities, using elemental Hg for Au-Hg amalgamation constitute biogeochemical reactors where dissolved organic matter (OM), SO4 and Fe oxides favor bacterial activity [17].…”

Transport, distribution and speciation of mercury in the Amazon River at the confluence of black and white waters of the Negro and Solimões Rivers

“…Previous research has focused primarily on the dynamics of Hg in gold-mining areas. Hg released from gold-mining activities was commonly thought to be responsible for the Hg contamination of aquatic ecosystems (Malm et al, 1990(Malm et al, , 1995Nriagu et al, 1992;Pfeiffer et al, 1993). However, recent studies have shown the importance of the pre-anthropogenic sources in the elevated Hg concentrations measured in the superficial mineral horizons of remote forested oxisols of the Tapajós basin (Roulet et al, 1998b).…”