Department of Geological Sciences and Geological Engineering, Queen's University, Miller Hall, Kingston, ON K7L 3N6, Canada.
Department of Geological Sciences and Geological Engineering, Queen's University, Miller Hall, Kingston, ON K7L 3N6, Canada.
Sci Total Environ. 2019 Mar 1;654:563-575. doi: 10.1016/j.scitotenv.2018.11.065. Epub 2018 Nov 6.
Forty-seven sediment cores were collected as part of a spatial survey of Long Lake, Yellowknife, NWT, Canada to elucidate the physical and geochemical controls on the distribution of arsenic (As) in sediments impacted by the aerial deposition of arsenic trioxide (AsO) from ore roasting at legacy gold mines. High-resolution profiles of dissolved As in bottom water and porewater were also collected to determine As remobilization and diffusion rates across the sediment-water interface. Arsenic concentrations in Long Lake sediments ranged from 2.2 to 3420 mg kg (dry weight). Two distinct types of sediment As concentration profiles were identified and are interpreted to represent erosional and depositional areas. Water depth is the best predictor of As concentration in the top 5 cm of sediments due to the inferred focusing of fine-grained AsO into deeper water. At greater sediment depths, iron (Fe) concentration, as a likely indicator of As, Fe, and sulphur (S) co-diagenesis, was the best predictor of As concentration. The sediments are a source of dissolved As to surface waters through diffusion-controlled release to bottom water. Arsenic concentrations, solid-phase speciation, and diffusive efflux varied laterally across the lake bottom and with sediment depth due to the interplay between sediment-focusing processes and redox reactions, which has implications for human health and ecological risk assessments.
作为对加拿大西北地区耶洛奈夫朗湖空间调查的一部分，采集了 47 个沉积物岩芯，以阐明受历史金矿焙烧产生的三氧化二砷（AsO）空中沉降影响的沉积物中砷（As）分布的物理和地球化学控制因素。还采集了底部水和孔隙水的溶解 As 高分辨率剖面，以确定 As 在沉积物-水界面的再迁移和扩散速率。朗湖沉积物中的 As 浓度范围为 2.2 至 3420mgkg（干重）。确定了两种不同类型的沉积物 As 浓度分布曲线，分别代表侵蚀区和沉积区。由于推断出细粒 AsO 聚焦到更深的水中，水深是预测沉积物顶层 5cm 中 As 浓度的最佳指标。在更深的沉积物中，铁（Fe）浓度作为 As、Fe 和硫（S）共成岩的可能指标，是预测 As 浓度的最佳指标。由于沉积物聚焦过程和氧化还原反应的相互作用，沉积物通过扩散控制释放到底部水中成为地表水溶解 As 的来源，这对人类健康和生态风险评估具有重要意义。
