AN ASSESSMENT OF THE POLLUTION OF HEAVY-METALS IN JACAREPAGUA BASIN, RIO-DE-JANEIRO, BRAZIL - A STATISTICAL APPROACH

The paper presents the metal pollution assessment of Jacarepagua basin rivers and lagoons based on statistical analysis of metal concentrati on in bottom sediments. It is demonstrated that Pavuna and Fundo Creek s are the main sources of anthropogenically introduced metals to the l agoons. Due to the weak process of water circulation in the lagoons th e contamination is restricted to the discharge areas of both rivers. M etal concentration in river sediments appears to be highly dependent o n rainfall events thus a seasonal (wet and dry seasons) variation in t heir concentration can be proposed. The examination of metal lognormal distribution plots indicates that concentration values, related to th e curve inflexion(s), can be operationally used as thresholds between polluted and unpolluted areas. These values were; 0.92 mu g g(-1) for Cd, 165 mu g g(-1) for Zn, 15 mu g g(-1) for Cr and 26 mu g g(-1) for Ni. Factor analysis was used to examine the main sources of metals to the aquatic environment. It can be suggested that the steel and chemic al industries would be the most important sources of metals released t o the aquatic environment.