Department of Environmental Science, School of Biological Sciences, University of Cape Coast, Cape Coast, Ghana.
Department of Environmental Sciences, Jožef Stefan Institute, Jamova Cesta 39, Ljubljana, Slovenia.
Environ Monit Assess. 2023 Apr 22;195(5):604. doi: 10.1007/s10661-023-11122-y.
The study assessed the spatial distribution of total mercury (THg) in soils, sediments, mining wastes, and Au-rich Hg-contaminated tailings from artisanal and small-scale gold mining (ASGM) from Offin, Lower and Upper Pra, Birim, and Anum Rivers, Pra River Basin, Southwestern Ghana. THg measurement using Cold Vapor Atomic Absorption Spectrometry (CVAAS) after acid digestion with HNO/HCl/HF and k-INAA, as a reference method, and both provided comparable results. A digestion method, HNO/HClO/HSO acid mixture before CVAAS provided lower results, which indicates that the use of HF is of fundamental importance in THg analysis based on acid digestion and its omission may significantly underestimate the presence of Hg in soils and sediments. THg in soils, sediments, Au-rich Hg-contaminated tailings, and mining wastes from the river basin were liberated into a solution for measurement using HNO/HCl/HF. The study revealed Offin and Lower Pra Rivers showed high distribution (ranges; mg Hg kg) of THg in soils (103-770) and sediments (0.20-20.8), respectively; Upper Pra and Anum rivers showed the lowest THg in soils (2.20-3.20) and sediments (0.004-0.02), respectively. About 76.0% of THg in sediments was lower than the USEPA guideline of 0.2 mg Hg kg. The highest mean THg (mg Hg kg) in Au-rich Hg-contaminated tailings (1673 ± 4.8, n = 4) and mining wastes (17.3-21.5) were from the river Offin. The study showed Offin (Dunkwa-on-Offin site 1) and Lower Pra (Beposo Township) rivers are Hg hotspots that need attention.
该研究评估了加纳西南部普里河流域奥芬、下普雷、上普雷、伯里姆和阿努姆河的手工和小规模金矿开采（ASGM）产生的土壤、沉积物、采矿废物和富含金的汞污染尾矿中总汞（THg）的空间分布。使用 HNO/HCl/HF 酸消解后，通过冷蒸气原子吸收光谱法（CVAAS）进行 THg 测量，作为参考方法，两种方法均提供了可比的结果。使用 HNO/HClO/HSO 酸混合物进行消解的方法提供了较低的结果，这表明在 THg 分析中使用 HF 是至关重要的，其缺失可能会显著低估土壤和沉积物中 Hg 的存在。采用 HNO/HCl/HF 酸消解后，从流域中提取土壤、沉积物、富含金的汞污染尾矿和采矿废物中的 THg 并溶解于溶液中进行测量。研究表明，奥芬河和下普雷河的土壤（103-770）和沉积物（0.20-20.8）中 THg 分布较高；上普雷河和阿努姆河的土壤（2.20-3.20）和沉积物（0.004-0.02）中 THg 分布最低。约 76.0%的沉积物中 THg 低于美国环保署规定的 0.2mg Hg kg 标准。富含金的汞污染尾矿（1673±4.8，n=4）和采矿废物（17.3-21.5）中 THg 的最高平均值来自奥芬河。研究表明，奥芬（Dunkwa-on-Offin 地点 1）河和下普雷河（Beposo 镇）是需要关注的汞热点。
