Assessment of trace metal contamination and bioavailability in an Environmental Protection Area: Guaxindiba estuarine system (Guanabara Bay, Rio de Janeiro Brazil)

Abstract

Guaxindiba River, located inside an Environmental Protected Area (EPA) inside Guanabara Bay, was evaluated concerning trace metals and arsenic. A total of 7 sediment cores up to 80 cm were extracted along the river and in the channel that connects Guaxindiba and Caceribu rivers. No natural enrichment from bottom to top was observed, suggesting a constant mobilization of the sedimentary column along the Guaxindiba River. Results showed elevated concentrations of Zn (175.77-321.01 mg.kg−1) and Ni (27.71-108.39 mg.kg−1) surpassing the probable effect levels (PEL) reference values. Sediments were considered severely enriched in Ni (EF >10) and Cu (EF>5). No enrichment was observed for As. The evaluation of bioavailability through the Risk Assessment Code (RAC), however, revealed medium risk for Zn and Ni, which exhibited high concentrations, and low risk for sediments severely enriched in Cu. Despite exhibiting minor enrichment and low concentrations, under PEL, the RAC revealed high risk for Cd, for bioavailability. Overall, the Guaxindiba River proved to be contaminated by recent pollution, in spite of its localization inside an EPA.