Geochemical behavior and remobilization potential of trace elements in surface sediments from the baixada santista industrial area, Southeastern Brazilian coast

Abstract

A three-stage sequential extraction procedure optimized by the European Community Bureau of Reference (BCR) was applied to assess the geochemical behavior and environmental mobility of As, Cr, Cu, Ni, Pb and Zn in surface sediments from two ecosystems under different anthropogenic influences, the Estuarine Complex of Santos and Sao Vicente (ECSSV) upper estuary (high anthropogenic influence) and the Bertioga channel (low anthropogenic influence), both of which are located on the coast of Sao Paulo, Brazil. In general, the difference between the regions varied considerably for almost all these elements, and the values for the Bertioga channel were always lower than those found in the upper estuary. Among all the elements, Zn showed the greatest mobility, being present mainly in the acid-soluble fraction. Arsenic and Pb were associated with the reducible fraction, and Cu and Ni in the oxidizable fraction. Meanwhile, Cr was mainly found in the residual fraction. Although previous studies, regarding total concentrations suggest the probable enrichment of Cu, Pb and Zn in the surface sediments of the ECSSV, according to our results and the Risk Assessment Code (RAC) analysis, only Zn presented a high risk of bioavailability, and the modified Risk Assessment Code (mRAC) only showed six samples in the inner estuary with a medium risk of mobilization. Therefore, this study can serve as a management tool and optimize the monitoring efforts of chemical pollution in the region.