Synergic effect of gold mining and damming on mercury contamination in fish
Synergic effect of gold mining and damming on mercury contamination in fish
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DOI：
10.1021/es049149r
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发表时间：
2005-04-15
影响因子：
11.4
通讯作者：
Cossa, D
中科院分区：
文献类型：
--
作者：
Boudou, A;Maury-Brachet, R;Cossa, D
自20世纪80年代末以来，几项研究表明，亚马逊盆地的人类在他们的鱼类饮食中暴露于高汞水平。黄金开采在合并过程中释放出金属，侵蚀自然富含汞的土壤，被认为是主要的污染源。在这里，我们提出了一个比较研究的结果，汞分布在水和鱼的两个相邻的河流在法属圭亚那，有和没有金矿开采活动。由于两个系统之间悬浮颗粒物的显著差异，开采河流中未经过滤的水样的总汞浓度(25.4-34.9 ng L-1)高于参考水样(2.1-5.4 ng L-1)。令人惊讶的是，上游13种常见鱼类之间的汞浓度没有显著差异。与此形成鲜明对比的是，在两条河流流经的水电站水库下游捕获的鱼的汞浓度，比上游高出8倍。汞形态测量使人们能够将鱼类中的这些差异与单甲基汞的水分布联系起来，单甲基汞是沿水生食物网生物聚集的汞化学物种。事实上，两条河流的平均溶解甲基汞浓度都很低且相似(0.03-0.06 ng L-1)，而水电站大坝流出的水中的平均溶解一甲基汞浓度高出10倍(高达0.56ngL-1)。沿水柱剖面的溶解单甲基汞测定表明，无机汞的甲基化发生在水库深层缺氧部分。我们的结论是，与黄金开采相关的汞动员不足以解释鱼类中的高浓度，还需要有利于汞甲基化的环境条件，如缺氧。
Since the late 1980s, several studies have shown that human populations in the Amazon basin are exposed to high mercury levels in their fish diet. Gold mining, which releases the metal during the amalgamation process and erodes soils naturally rich in mercury, is regarded as the main contamination source. Here, we present the results of a comparative study of mercury distribution in the water and fish of two adjacent rivers in French Guiana, with and without gold mining activities. As a consequence of a marked difference in suspended particulate matter between the two systems, total mercury concentrations in unfiltered water samples were higher in the mined river (25.4-34.9 ng L-1) as compared to the reference one (2.1-5.4 ng L-1). Surprisingly, no significant differences were observed in mercury concentrations between 13 common fish species at upstream sites. In sharp contrast, mercury concentration of fish caught downstream a hydroelectric reservoir, where the two rivers flow, was up to 8-fold higher than that upstream. Mercury speciation measurements allowed one to relate these differences in fish to the water distribution of monomethylmercury, the mercury chemical species that biornagnifies along aquatic foodwebs. Indeed, mean dissolved monomethylmercury concentrations were low and similar in both rivers (0.03-0.06 ng L-1), while they were 10 times higher (up to 0.56 ng L-1) in the water outflowing the hydroelectric dam. Dissolved monomethylmercury determinations along a water column profile suggest that methylation of inorganic mercury occurs in the deep anoxic part in reservoir. We conclude that mercury mobilization related to gold mining is not solely sufficient to account for high concentrations in fish and that environmental conditions that favor mercury methylation, such as anoxia, are needed.