Concentrations of Pb, Cd and Zn in sediments of an estuarine complex affected by ancient mining activities in Southeast Brazil

Resumen

One of the first environmental disasters in Brazil took place in the Estuarine-Lagoon Complex of Iguape-Cananéia. The opening of an artificial channel in the 19th century diverted the flow of the Ribeira de Iguape River, which was heavily affected by mining activities, into the system. Since then the river became the main responsible for the flow of fresh water and suspended sediments to the estuarine region. This study aimed to evaluate the concentrations of lead, cadmium and zinc in the surface sediment at 10 points along the estuary, 15 years after mining activities had ceased. The concentrations of lead and cadmium varied from 19.3 to 67.9 µg.g-1 and from 2.4 to 3.6 µg.g-1 respectively, with higher concentrations mainly in areas near the mouth of the Ribeira de Iguape River (Iguape City and Juréia beach), whit values above the maximum limit established by the Brazilian Environmental Agency. Zinc varied from 10.4 to 22.8 µg.g-1, below the maximum established value whit no content differences between the points. This study reveals contamination points of the sediment by lead and cadmium in the estuarine region, still indicating a strong contribution of the ancient mining activities as of other humans’ activities such as agriculture and incorrect garbage and sewage disposal. Additionally, these results suggest that these contamination can cause adverse effects to the local biota, as so, the evaluation of metals takes great importance for the continuous monitoring of the environmental quality of the region.