Department of Oceanographie, University of Espírito Santo State, Vitória, ES 29075-910, Brazil.
Department of Oceanographie, University of Espírito Santo State, Vitória, ES 29075-910, Brazil.
Sci Total Environ. 2017 Dec 31;607-608:304-316. doi: 10.1016/j.scitotenv.2017.06.162. Epub 2017 Jul 27.
This study focuses on the vertical distribution of total and reactive As in two contrasted coastal sedimentary environments: the Abrolhos Continental Shelf (ACS), a carbonate and siliciclastic shelf sediment, and the Doce River Continental Shelf (DRCS), a submerged delta system. The Doce River was the location of a massive ore tailings dam collapsed in November 2015. Millions of liters of tailings were dumped into the river and reached the continental shelf, causing the country's biggest environmental disaster. We evaluated the As content in sediment of the DRCS before the dam collapse. At both sites, the total As background measured in bottom sediment revealed relative natural enrichment (above 8mg/kg). Content of As decrease with depth; reactive As showed surficial peaks which were associated with Fe and Mn oxides. The ACS sediment did not show significant enrichment or contamination of As, with an enrichment factor (EF) of approximately 2 and a geoaccumulation index (Igeo) near 0. In contrast, the DRCS exhibited severe As enrichment (EF=15) and contamination (Igeo between 3-4). This enrichment is attributed to long-term iron and gold exploitation in the Doce River watershed. The high levels of reactive As, up to 108 mg/kg, alert us to an environmental risk due to potential As bioaccessibility. These data provide an important perspective on the As contamination in continental shelves and encourage the monitoring of the ore mine environmental impacts.
阿布洛罗什大陆架（ACS），一个碳酸盐和硅质碎屑架沉积物，以及多斯河大陆架（DRCS），一个淹没的三角洲系统。2015 年 11 月，多斯河上的一个大型矿石尾矿坝发生了灾难性的溃坝事件。数百万升的尾矿被倾倒进河里并进入了大陆架，引发了巴西历史上最严重的环境灾难。我们评估了溃坝前 DRCS 沉积物中的砷含量。在这两个地点，底层沉积物中测量到的总砷背景值都显示出相对自然的富集（高于 8mg/kg）。砷含量随深度减少；反应性砷在表层出现峰值，与铁和锰氧化物有关。ACS 沉积物没有表现出明显的砷富集或污染，富集因子（EF）约为 2，地质累积指数（Igeo）接近 0。相比之下，DRCS 则表现出严重的砷富集（EF=15）和污染（Igeo 在 3-4 之间）。这种富集归因于多斯河流域长期的铁和金矿开采。高达 108mg/kg 的高浓度反应性砷提醒我们注意由于潜在的砷生物可利用性而带来的环境风险。这些数据为大陆架上的砷污染提供了一个重要视角，并鼓励对矿山环境影响进行监测。
