Metals in the Sediments of Reservoirs: Is There Potential Toxicity?

Metals are important recognized for their potentially toxic character to communities, in addition to being bioaccumulative in some organisms. In this work, the concentrations of cadmium, chromium, copper, lead, mercury, and zinc in sediments from three sampling points in the Billings, Guarapiranga, and Rio Grande reservoirs (São Paulo, Brazil) between the years 2008 and 2017 were evaluated. Data were compared to regional reference values, to local legislation, and to sediment quality values: threshold effect level (TEL), probable effect level (PEL), and Sediment Assessment Criteria (CQS). Billings reservoir sediment samples had the highest number of metals with contents above the reference values and above the PEL. There were high copper concentrations in the Guarapiranga and the Rio Grande reservoirs probably due to the management system currently in use, which is based on Copper Sulphate Pentahydrate. The data analyzed here indicate that the lack of regionalized indexes with background values and toxicity criteria for sediment, specific for each of these reservoirs, is a great problem for more accurate and predictive analysis. This study shows that the current contamination levels of the reservoir sediments are reducing the water.