Spatial variation of trace elements in the Tiete river bottom sediments (Sao Paulo, Brazil): enrichment factors and anthropogenic contributions

The spatial variation of some trace elements (Ni, Cr, Zn, Cu, Sc, Co, Rb, Sr, Cs, Pb, Th and U) was studied in the bottom sediments of the Tietê river in São Paulo, Brazil. The main objective was to identify the enrichment factors and possible anthropic contributions to the observed high toxicity of these chemical elements in this drainage basin, which crosses the metropolitan area of São Paulo city with about 20 millions people and receives a large load of domestic and industrial wastes. The chemical analyses were performed after the chemical extraction procedure using alkaline fusion with Lithium tetraborate. An Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) and a Neutron Activation Analysis (NAA) were used for the analytical purposes. The enrichment factor was calculated by the relationship between the concentration of each trace element in the bottom sediment and the natural soil background in the drainage basin, weighted by the conservative Sc