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.

汞（在厄瓜多尔和秘鲁共享的Puyango-Tumbes河的环境样本中检查了Hg）浓度和稳定同位素以及其他痕量金属，以确定厄瓜多尔Portovelo-Zaruma进行手工和小规模金矿开采（ASGM）的程度导致下游水生生态系统中的汞污染。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。在这项研究中，汞同位素揭示了下游沉渣中同位素重的汞特征，其质量独立分数（MIF）可忽略不计，这与在ASGM源端成员中观察到的特征一致。这个特征可以追溯到Portovelo-Zaruma下游约120公里处，表明汞稳定同位素可以用作在淡水环境中远距离指纹识别和追踪汞来源的工具。汞同位素在淡水中作为源示踪剂的成功很大程度上归因于汞的颗粒反应性。此外，下游汞，铅，铜和锌的污染的程度和程度以及汞同位素表明，不使用氰化作用的较小手工规模的活动不太可能造成污染。在小规模金矿开采中使用的矿石的规模和氰化物浸出的可能性更大，氰化物浸出可以释放其他金属并提高汞的传输。因此，尽管在波托韦洛-祖鲁马的手工和小规模采金活动同时进行，但应在这两种活动之间加以区分。