Universidade Federal Fluminense, Instituto de Geociências, Departamento de Geologia e Geofísica Marinha, Avenida General Milton Tavares de Souza, S/n, Niterói, RJ, CEP: 24210346, Brazil.
Universidade Federal Fluminense, Instituto de Geociências, Departamento de Geologia e Geofísica Marinha, Avenida General Milton Tavares de Souza, S/n, Niterói, RJ, CEP: 24210346, Brazil.
J Environ Manage. 2020 Oct 15;272:111086. doi: 10.1016/j.jenvman.2020.111086. Epub 2020 Jul 20.
The present study deals with bioavailability of trace metals in the Doce river continental shelf, southeast of Brazil. The bottom sediments of the study area were firstly sampled a few weeks before the biggest environmental disaster of Brazil, the collapse of the Fundão dam in November of 2015. The disaster released around 40 Mm of iron ore tailings into Doce river basin and an estimate of 10 Mm reached the river delta, having the adjacent continental shelf as the final destination. One year and a half later, on April of 2017, the continental shelf was sampled again. A total of 48 stations were evaluated concerning concentrations of trace metals (Zn, Cu, Pb, Ni, Cr) and other ancillary variables before and after the accident. Trace metals were determined through fractionation in order to assess mobility and establish the ecological risk through RAC index. Before the accident, trace metals mobility was Pb > Ni > Cu > Zn > Cr, with Pb Cu, Ni and posing high ecological risk (RAC>30%) in many stations. Differences in concentrations of metal from pre to post accident were significant, and the increase of trace metals was observed. The mobility order after the accident changed to: Cu > Pb > Ni > Zn > Cr. Metal fractionation showed remarkable changes after the accident, with elements such as Cu, Ni and Zn highly associated with reducible fractions originated from the tailings composition. Despite the decrease of RAC to medium risk after the accident in most stations, the bioavilability of Cu, Pb, Ni and Zn increased as show by their higher accumulation in the bioavailable fractions.
本研究探讨了巴西东南部多斯河大陆架中微量元素的生物可利用性。在 2015 年 11 月丰当大坝坍塌这一巴西最大的环境灾难发生前的几周，对研究区域的底泥进行了首次采样。这场灾难导致约 4000 万吨铁矿尾矿进入多斯河流域，其中估计有 1000 万吨到达河口三角洲，最终的目的地是相邻的大陆架。一年半后，也就是 2017 年 4 月，再次对大陆架进行了采样。在事故前后，共评估了 48 个站点的痕量金属（Zn、Cu、Pb、Ni、Cr）浓度和其他辅助变量。通过分级来确定痕量金属的移动性，并通过 RAC 指数建立生态风险。事故发生前，痕量金属的移动性顺序为 Pb>Ni>Cu>Zn>Cr，其中 Pb、Cu 和 Ni 在许多站点存在高生态风险（RAC>30%）。事故前后金属浓度差异显著，且痕量金属浓度增加。事故后，金属的移动性顺序变为 Cu>Pb>Ni>Zn>Cr。金属分级显示，Cu、Ni 和 Zn 等元素与尾矿成分中的可还原部分高度相关，发生了显著变化。尽管大多数站点的 RAC 在事故后降至中等风险，但 Cu、Pb、Ni 和 Zn 的生物可利用性增加，因为它们在可利用部分的积累更高。
