Jozef Stefan International Postgraduate School, Jamova Cesta 39, 1000, Ljubljana, Slovenia.
School of Nuclear and Allied Sciences, College of Basic and Applied Sciences, University of Ghana, Legon, Ghana.
Environ Monit Assess. 2021 Mar 10;193(4):180. doi: 10.1007/s10661-021-08920-7.
Studies on the influence of CN on Hg methylation rates in aquatic systems draining gold mining (artisanal and small-scale) communities in Africa are rare. The study assessed the influence of CN on Hg methylation in aquatic sediments of two major river systems draining artisanal and small-scale gold mining (ASGM) communities of the Prestea-Huni Valley district, Southwestern Ghana. The miners extract gold (Au) through exclusive amalgam [Hg-Au] formation or cyanidation of Au-rich Hg-contaminated tailings, or a combination of both techniques. Hg water solubility and probable mercuric compounds in sediments of Hg-contaminated CN-loaded (River Aprepre) and Hg-contaminated non-CN (River Ankobra) aquatic systems within the district were investigated. THg was determined by CV-AAS after HF/HNO/HCl digestion. MeHg in sediments were extracted with HSO/KBr/CuSO-CHCl; followed by aqueous-phase propylation, preconcentration-on-Tenax, and GC-CV-AFS. River Aprepre showed 4.58-14.83 ngMeHg/g as Hg (1.4-3.7% THg as MeHg), with 241-415 ngTHg/g, and 0.05-0.21 mgCN/kg. For River Ankobra, MeHg ranged 0.24-1.21 ngMeHg/g (0.08-0.35% THg as MeHg) with 162-490 ngTHg/g dw and CN < 0.001 mg/kg. There was positive correlation (r = 0.5974; p < 0.01) between MeHg and CN in River Aprepre. The water-soluble fraction of Hg in sediment from both rivers was < 1% of THg. Hg in sediments from River Aprepre were generally more soluble than that from River Ankobra, indicating that Hg in sediments from River Aprepre were potentially more bioavailable for methylation. Accordingly, the presence of CN in Hg-dominated river sediments potentially influences and enhances the solubility and mobility of Hg, resulting in increased Hg methylation rates.
关于氰化物（CN）对非洲金矿开采（手工和小规模）社区水系汞甲基化速率影响的研究很少。本研究评估了 CN 对加纳西南部普雷斯特山谷矿区两个主要河流系统（手工和小规模金矿开采社区）水成沉积物中汞甲基化的影响。矿工们通过独家汞金合金（Hg-Au）形成或富汞污染尾矿的氰化作用来提取金（Au），或者同时使用这两种技术。本研究调查了该地区受 Hg 污染的 CN 负荷（Aprepre 河）和 Hg 污染非-CN（Ankobra 河）水系沉积物中的 Hg 水溶性和可能的汞化合物。使用 HF/HNO/HCl 消解后，通过 CV-AAS 测定总汞（THg）。用 HSO/KBr/CuSO-CHCl 提取沉积物中的 MeHg；然后进行水相丙基化、Tenax 预浓缩和 GC-CV-AFS。Aprepre 河的 MeHg 浓度为 4.58-14.83ngMeHg/g（THg 的 1.4-3.7%为 MeHg），THg 浓度为 241-415ng/g，CN 浓度为 0.05-0.21mg/kg。对于 Ankobra 河，MeHg 的范围为 0.24-1.21ngMeHg/g（THg 的 0.08-0.35%为 MeHg），THg 浓度为 162-490ng/g dw，CN 浓度 <0.001mg/kg。Aprepre 河的 MeHg 与 CN 之间存在正相关关系（r=0.5974；p<0.01）。两条河流沉积物中 Hg 的水溶性部分均 <1%THg。Aprepre 河沉积物中的 Hg 通常比 Ankobra 河沉积物中的 Hg 更易溶解，这表明 Aprepre 河沉积物中的 Hg 更具生物利用性。因此，Hg 为主的河流沉积物中 CN 的存在可能会影响和增强 Hg 的溶解度和迁移率，从而增加 Hg 的甲基化速率。
