Geography and Environmental Studies, Carleton University, Ottawa, ON K1S 5B6, Canada.
Environment and Climate Change Canada, National Wildlife Research Centre, Ottawa, ON K1A 0H3, Canada.
Environ Pollut. 2020 Apr;259:113888. doi: 10.1016/j.envpol.2019.113888. Epub 2020 Jan 6.
The contributions of contaminant sources are difficult to resolve in the sediment record using concentration gradients and flux reconstruction alone. In this study, we demonstrate that source partitioning using lead isotopes provide complementary and unique information to concentration gradients to evaluate point-source releases, transport, and recovery of metal mining pollution in the environment. We analyzed eight sediment cores, collected within 24 km of two gold mines, for Pb stable isotopes, Pb concentration, and sediment chronology. Stable Pb isotope ratios (Pb/Pb, Pb/Pb) of mining ore were different from those of background (pre-disturbance) sediment, allowing the use of a quantitative mixing model. As previously reported for some Arctic lakes, Pb isotope ratios indicated negligible aerosol inputs to sediment from regional or long-range pollution sources, possibly related to low annual precipitation. Maximum recorded Pb flux at each site reached up to 63 mg m yr in the period corresponding to early years of mining when pollution mitigation measures were at a minimum (1950s-1960s). The maximum contribution of mining-derived Pb to these fluxes declined with distance from the mines from 92 ± 8% to 8 ± 4% at the farthest site. Mining-derived Pb was still present at the sediment surface within 9 km of Giant Mine more than ten years after mine closure (5-26 km, 95% confidence interval) and model estimates suggest it could be present for another ∼50-100 years. These results highlight the persistence of Pb pollution in freshwater sediment and the usefulness of Pb stable isotopes to quantify spatial and temporal trends of contamination from mining pollution, particularly as concentrations approach background.
仅使用浓度梯度和通量重建，难以在沉积物记录中解决污染物来源的贡献问题。在这项研究中，我们证明了使用铅同位素进行源分配可以为浓度梯度提供补充和独特的信息，从而评估金属采矿污染在环境中的点源释放、传输和恢复。我们分析了八个沉积物岩芯，这些岩芯是在距离两个金矿 24 公里范围内采集的，用于分析 Pb 稳定同位素、Pb 浓度和沉积物年代。采矿矿石的稳定 Pb 同位素比值（Pb/Pb、Pb/Pb）与背景（干扰前）沉积物的比值不同，这使得可以使用定量混合模型。与一些北极湖泊的情况一样，Pb 同位素比值表明，来自区域或远程污染源的气溶胶输入对沉积物的影响可以忽略不计，这可能与年降水量低有关。在每个地点记录的最大 Pb 通量在与采矿污染最小化（20 世纪 50 年代至 60 年代）时期相对应的时期达到了高达 63mg·m-2·yr-1。从矿场最远处的站点开始，采矿衍生 Pb 对这些通量的最大贡献从 92%±8%下降到 8%±4%。在矿山关闭后超过十年的时间里，距离 Giant 矿 9 公里范围内的沉积物表面仍存在采矿衍生 Pb（5-26 公里，95%置信区间），模型估计表明它可能还会存在大约 50-100 年。这些结果突出了 Pb 污染在淡水沉积物中的持久性，以及 Pb 稳定同位素在量化采矿污染的空间和时间趋势方面的有用性，尤其是在浓度接近背景的情况下。
