Trace metals in port area waters on the Patos Lagoon estuary, RS

Abstract

The Rio Grande Channel, in the area of the Port of Rio Grande, receives direct and indirect contributions of trace metals, which can compromise the quality of the estuarine waters of the lagoon. In this study, data of trace metals studies from the monitoring program of the port area of the estuary, from 1996 to 2001, were interpreted. The objective was to evaluate the distribution of cadmium, copper, lead and zinc concentrations in the total fraction of surface waters along the port area, in areas known as Porto Novo, Superporto and São José do Norte located at the Rio Grande Canal. The results showed that only the cadmium and lead concentrations were different between summer/spring (0.94 μg.L-1 Cd and 1.94 μg.L-1 Pb) and winter/autumn (0.31 μg.L-1 Cd and 2.45 μg.L-1 Pb). Regarding the spatial variation, the concentrations of four metals analyzed did not differ between study areas. In terms of variations between the studied years, the metals lead, copper and zinc showed decreases of concentrations in the years 2000 and 2001, probably because dredging activities in the estuary which remobilized sediments, and thus releasing, diluting and dispersing the metals accumulated.