Arsenic enrichment in sediment on the eastern continental shelf of Brazil.

Autor: Cagnin RC; Department of Oceanographie, University of Espírito Santo State, Vitória, ES 29075-910, Brazil. Electronic address: renatacaiado@hotmail.com., Quaresma VS; Department of Oceanographie, University of Espírito Santo State, Vitória, ES 29075-910, Brazil., Chaillou G; Canada Research Chair in Geochemistry of Hydrogeosystems, Département de Biologie, Chimie, Géographie, Université du Quebec à Rimouski, Rimouski, QC G5L 3A1, Canada., Franco T; Department of Oceanographie, University of Espírito Santo State, Vitória, ES 29075-910, Brazil., Bastos AC; Department of Oceanographie, University of Espírito Santo State, Vitória, ES 29075-910, Brazil.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2017 Dec 31; Vol. 607-608, pp. 304-316. Date of Electronic Publication: 2017 Jul 27.
DOI: 10.1016/j.scitotenv.2017.06.162
Abstrakt: 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.
(Copyright © 2017 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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