Environment and Climate Change Canada, National Wildlife Research Centre, Ottawa, Ontario, Canada.
North Slave Research Centre, Aurora Research Institute, Aurora College, Yellowknife, Northwest Territories, Canada.
J Hazard Mater. 2023 Jun 15;452:131230. doi: 10.1016/j.jhazmat.2023.131230. Epub 2023 Mar 16.
Arsenic contamination from mining poses an environmental challenge due to the mobility of this redox-sensitive element. This study evaluated arsenic mobility in sediments of Yellowknife Bay (Canada), a large subarctic water body impacted by gold mining during the 20th century. Short-term measurements of arsenic flux from sediment, arsenic profiling of the water column and sediment porewater, and mass balance modelling were conducted to assess the importance of sediment as an arsenic source. Sediment arsenic fluxes were highly variable throughout Yellowknife Bay and ranged from - 65-1520 µg m day. Elevated fluxes measured near the mine site were among the highest published for well-oxygenated lakes. Redox boundaries were typically 2-3 cm below the sediment surface as indicated by porewater profiles of iron, manganese, and arsenic, with arsenic maxima of 65-3220 µg L predominately as arsenite. Sediment arsenic flux was positively related to its solid-phase concentration. Modelling indicated sediment was a principal source of arsenic to the water column. Adsorption and precipitation processes in the oxidizing environment of near-surface sediments did not effectively attenuate arsenic remobilized from contaminated sediments. Internal recycling of legacy arsenic between sediment and surface water will impede a return to background conditions in Yellowknife Bay for decades.
采矿造成的砷污染是一个环境挑战，因为这种氧化还原敏感元素具有移动性。本研究评估了加拿大黄刀湾（Yellowknife Bay）沉积物中的砷迁移性，黄刀湾是一个大型亚北极水体，在 20 世纪受到金矿开采的影响。进行了短期沉积物砷通量测量、水柱和沉积物孔隙水砷剖面分析以及质量平衡建模，以评估沉积物作为砷源的重要性。整个黄刀湾的沉积物砷通量变化很大，范围为-65-1520 µg m day。在矿区附近测量到的高通量是在富氧湖泊中发表的最高通量之一。如孔隙水铁、锰和砷的剖面所示，氧化还原边界通常在沉积物表面以下 2-3 厘米处，砷的最大值为 65-3220 µg L，主要以亚砷酸盐形式存在。沉积物砷通量与其固相浓度呈正相关。模型表明，沉积物是向水柱砷的主要来源。在近表面沉积物氧化环境中，吸附和沉淀过程并不能有效地减轻受污染沉积物中再移动的砷。几十年来，沉积物和地表水之间的砷的内部循环将阻碍黄刀湾恢复到背景条件。
