Abstract：
In November 2015, the Fundão Dam break released millions of tons of metal-rich tailings into the Doce River Basin (DRB), causing catastrophic damage and potential ecological effects that reached the Atlantic Ocean. This study aimed to evaluate the geochemistry and toxicity of water and sediments collected in the DRB from 2015 to 2019 and to determine the spatial and temporal trends. Water and sediment samples were analyzed for metals and As by inductively coupled plasma optical emission spectrometry (ICP-OES), and acute toxicity for Daphnia similis or D. magna. Results were explored using geochemical indices and correlation analyzes. Overall, higher concentrations of metals and As in water and sediments were observed immediately after dam breakage, but the levels exhibited a decreasing trend over time, although the levels of some elements such as As and Mn remained high in the upper DRB. The geochemical indices indicated mostly low to moderate contamination, and the enrichment factor (EF) demonstrated a higher enrichment of Mn in the upper DRB. Acute toxicity to water fleas (D. similis and D. magna) was occasionally observed in waters and sediments, but the reference samples were toxic, and the short-term effects were not correlated with metals and As. Overall, the results showed limited bioavailability of metals and As and a decreasing trend in their concentrations, indicating an ongoing recovery process in DRB. These results are important to decision-making regarding the disaster and actions for environmental restoration.
摘要：
2015年11月，Fundão大坝决口向多西河流域（DRB）释放了数百万吨富含金属的尾矿，造成灾难性的破坏和到达大西洋的潜在生态影响。这项研究旨在评估2015年至2019年DRB中收集的水和沉积物的地球化学和毒性，并确定其时空趋势。通过电感耦合等离子体发射光谱法（ICP-OES）分析水和沉积物样品中的金属和砷，和急性毒性水蚤或D.magna。使用地球化学指数和相关性分析探索结果。总的来说,大坝破裂后立即观察到水和沉积物中金属和砷的浓度较高，但是随着时间的推移，水平呈现出下降的趋势，尽管某些元素如As和Mn的水平在上DRB中仍然很高。地球化学指数表明主要是低至中度污染，富集因子（EF）表明上部DRB中Mn的富集更高。对水蚤的急性毒性(D.similis和D.magna)偶尔在水域和沉积物中观察到，但是参考样本是有毒的，短期效应与金属和砷无关。总的来说,结果表明，金属和砷的生物有效性有限，其浓度呈下降趋势，指示DRB中正在进行的恢复过程。这些结果对于有关灾难和环境恢复行动的决策非常重要。
