Norman B. Keevil Institute of Mining Engineering, University of British Columbia, 517-6350 Stores Road, Vancouver, BC, V6T 1Z4, Canada.
Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
Curr Environ Health Rep. 2020 Sep;7(3):303-310. doi: 10.1007/s40572-020-00276-3.
To examine cyanide (CN-) contamination of a large river in southeastern Ecuador that has been severely impacted by the indiscriminate discharge of untreated gold processing effluents.
Poor environmental stewardship of cyanide (CN-) use by 87 gold processing centers in Portovelo-Zaruma in southern Ecuador to leach residual gold from Hg-contaminated tailings has resulted in high CN- contamination of the Puyango-Tumbes River downstream from the centers. Free CN- concentrations were high in river surface waters for 50 km below the processing plants, with the highest concentration 9088 times above the CCME standard of 5 μg/L and 1136 times above the 24-h LC concentration of 40 μg/L free CN- for some fish species. Due to cyanidation of mercury-contaminated tailings, the formation of Hg-CN complexes is a grave concern, as these complexes have been shown to be highly bioavailable. Preliminary tests conducted in a laboratory using bioassays with Danio rerio sp. and varying concentrations of synthetic Hg(CN) salt have shown significant THg bioaccumulation in muscle and kidney fish tissues exposed to concentrations >0.12 mg/L. Furthermore, low MeHg results in fish tissues demonstrated little occurrence of methylation and that the bulk of the total mercury content was in the form of inorganic mercury. Although construction of a communal tailings facility (CTF) in Portovelo is a positive development to reduce riverine pollution, the requirement to truck tailings up to the CTF likely results in inadequate compliance of environmental regulations that are poorly enforced.
检查厄瓜多尔东南部一条大河的氰化物 (CN-) 污染情况，这条河受到未经处理的金矿处理废水的无差别排放的严重影响。
厄瓜多尔南部波托维洛-萨拉莫 87 家金矿处理中心在氰化物 (CN-) 使用方面缺乏良好的环境管理，将汞污染尾矿中的残留金浸出，导致下游普扬戈-通贝斯河受到高浓度 CN- 的污染。处理厂下游 50 公里范围内的河流水面游离氰化物浓度较高，最高浓度是加拿大环境管理委员会标准（5μg/L）的 9088 倍，是一些鱼类 24 小时 LC 浓度（游离氰化物 40μg/L）的 1136 倍。由于汞污染尾矿的氰化作用，Hg-CN 络合物的形成是一个严重的问题，因为这些络合物具有很高的生物利用度。在实验室使用 Danio rerio sp. 进行生物测定，并使用不同浓度的合成 Hg(CN)盐进行的初步测试表明，暴露于浓度 >0.12mg/L 的鱼肌肉和肾脏组织中，总汞的生物积累量显著增加。此外，鱼组织中低 MeHg 的存在表明甲基化的发生很少，总汞含量的大部分以无机汞的形式存在。尽管在波托维洛建造一个公共尾矿设施（CTF）是减少河流污染的一个积极举措，但将尾矿用卡车运到 CTF 的做法可能导致环境法规的执行不力，从而无法充分遵守这些法规。
