Diffuse sources of pollution and their influence on the nature of the sediments in Água Preta Lake

Abstract

Sediments in aquatic systems are indicators of contamination levels. Therefore, they play an important role in the assessment of the nature and intensity of human impact on aquatic environments. The objective of this work was to assess the levels of pollution by determining the concentrations of various metals and phosphorus forms in the sediments of Agua Preta Lake, which supplies water to the Metropolitan Region of Belem, in north-eastern Brazil. Our data indicate non-uniform sedimentation with a large granulometric fraction of silt. The predominant form of phosphorus was inorganic phosphorus, to the detriment of the organic form. Observed mean concentrations of nickel, copper, lead, and zinc were lower than the PEL (Probable Effect Level). However, the highest observed concentrations of nickel and lead exceeded the prescribed TEL (Threshold Effect Level), which suggests pollution from an anthropogenic source.