摘要
本文阐述和评论了影响亚马孙河流域汞循环的途径,并提出了新的研究方向。对于汞污染源的讨论,无论是天然的还是人为的,都缺乏基本的论据。毫无疑问,黄金矿山释放的汞已经局部地提高了环境中汞的浓度,但在整个亚马孙河流域,与一些学者在远离金矿的土壤中测出的高浓度数值相比,这种负荷并不显著。土壤中汞的高浓度现象有一个合理的解释,即B层(淀积层)是在地质时期蓄积了汞的'海绵体',当发生侵蚀和森林火灾时,汞又被释放回循环体系。源于人类活动导致的亚马孙河流域森林的环境退化,很可能会加速汞的释放。汞在还原性的缺氧环境——沉积物和水中——的转换也是理解汞的环境甲基化的一个关键性问题。在亚马孙河流域环境所做的这项研究非常有限,研究结果只能得出受限的结论,进一步的工作应注重结合时间和空间变化的监测计划。
In this paper, the processes that affect mercury (Hg) cycling in the Amazonian environment were reviewed, criticized and new directions of research are proposed. The discussion of the origin of the mercury contamination, whether natural or anthropogenic is marked by a lack of fundamented arguments from both sides. Undoubtedly mercury inputs from gold mining have locally increased environmental concentrations, but in the whole Amazon, these loads would be insignificant, considering the high concentrations observed by some authors in remote soils. A reasonable process that should explain these elevated concentrations in soil is that B horizons function as a mercury 'sponge' that have been accumulating mercury over a geological time scale, releasing it back to cycling during erosion and forest fires. The environmental degradation of the Amazonian forest due to human activities is probably enhancing the release of that mercury to the cycle. Mercury transformations in reduced, anoxic environments-sediments and waters-are also a key problem for the understanding of the environmental methylation. The studies that have been carried out in the Amazonian environment are too restricted and results permit only circumstantial conclusions. Large efforts must be directed to monitoring programs considering time and space variability.
