University of Toronto, Department of Earth Sciences, 22 Russell Street, Toronto, ON, M5S 3B1, Canada.
Johns Hopkins University Bloomberg School of Public Health, Department of Environmental Health and Engineering, 615 N. Wolfe Street, Baltimore, MD, 21205-2103, USA; University of British Columbia, Norman B. Keevil Institute of Mining Engineering, Vancouver, BC, V6T IZ4, Canada.
Chemosphere. 2018 Jul;202:777-787. doi: 10.1016/j.chemosphere.2018.03.081. Epub 2018 Mar 12.
Mercury (Hg) concentrations and stable isotopes along with other trace metals were examined in environmental samples from Ecuador and Peru's shared Puyango-Tumbes River in order to determine the extent to which artisanal- and small-scale gold mining (ASGM) in Portovelo-Zaruma, Ecuador contributes to Hg pollution in the downstream aquatic ecosystem. Prior studies investigated the relationship between ASGM activities and downstream Hg pollution relying primarily on Hg concentration data. In this study, Hg isotopes revealed an isotopically heavy Hg signature with negligible mass independent fractionation (MIF) in downstream sediments, which was consistent with the signature observed in the ASGM source endmember. This signature was traced as far as ∼120 km downstream of Portovelo-Zaruma, demonstrating that Hg stable isotopes can be used as a tool to fingerprint and trace sources of Hg over vast distances in freshwater environments. The success of Hg isotopes as a source tracer in fresh waters is largely due to the particle-reactive nature of Hg. Furthermore, the magnitude and extent of downstream Hg, lead, copper and zinc contamination coupled with the Hg isotopes suggest that it is unlikely that the smaller artisanal-scale activities, which do not use cyanidation, are responsible for the pollution. More likely it is the scale of ores processed and the cyanide leaching, which can release other metals and enhance Hg transport, used during small-scale gold mining that is responsible. Thus, although artisanal- and small-scale gold mining occur in tandem in Portovelo-Zaruma, a distinction should be made between these two activities.
对厄瓜多尔波托维洛-萨拉莫地区和秘鲁普扬戈-通贝斯河共享流域的环境样本中的汞 (Hg) 浓度和稳定同位素以及其他微量元素进行了检测，以确定小规模和手工采金 (ASGM) 在多大程度上导致下游水生生态系统受到汞污染。先前的研究主要依靠汞浓度数据调查了 ASGM 活动与下游汞污染之间的关系。在本研究中，汞同位素揭示了下游沉积物中具有显著非质量分馏（MIF）的重同位素特征，这与 ASGM 源端元中观察到的特征一致。这种特征一直追溯到波托维洛-萨拉莫下游约 120 公里处，表明汞稳定同位素可用于在淡水环境中追踪和追踪汞的来源。汞同位素作为示踪剂在淡水中取得成功主要是由于汞的颗粒反应性质。此外，下游汞、铅、铜和锌污染的程度和范围，再加上汞同位素表明，不太可能是那些不使用氰化物的小规模手工活动导致了污染。更有可能的是，在小规模采金过程中处理的矿石规模和氰化物浸出，会释放其他金属并增强汞的迁移，这是导致污染的原因。因此，尽管在波托维洛-萨拉莫地区同时存在小规模和手工采金活动，但应该对这两种活动加以区分。
