Distribution and enrichment of heavy metals at the Tapacurá River basin, northeastern Brazil

Abstract

Distribution and enrichment of heavy metals in the sediments at the Tapacura River basin (Northeastern Brazil) were examined. Sediment samples from eight sites in the basin were collected each three months in the period from April/1997 to January/1999 and between June/2005 and March/2006. Metal levels in sediments varied from 550 to 32,606 Fe, 13.46 to 157.62 Mn, 0.96 to 57.32 Cu, &lt0.01 to 1.31 Pb, &lt0.0005 to 3.30 Cd, 4.03 to 55.16 Zn, 0.06 to 6.53 Ni and 0.04 to 5.90 Cr mg g-1 dw. The concentrations of metals in the industrial and agricultural areas were higher than those in the urban areas. The results demonstrated that terrigenous sediments from the industrial and agricultural areas are dominating factor controlling the spatial variations of heavy metals on the Tapacura River. Grain size and anthropogenic influences are also major factors modifying the spatial variations of heavy metals. Pb and Cd had higher enrichment factors. The maximum potential contamination indices for the basin were 218 to Pb and 660 to Cd. The correlation analysis showed that the Fe and OM varied independently from one another, implies that the concentration of metals in sediments can not be interpreted simply by a change in grain size. The first step to apply a remedial measure is the inspection of the agricultural areas and the use controlled of fertilizers and herbicides. Information of this nature on heavy metals can provide valuable contribution to the program of sanitation at the Companhia Pernambucana de Meio Ambiente - CPRH.