Geochemistry and index of geoaccumulation of mercury in surface sediments from Santos-Cubatao Estuary, State of Sao Paulo, Brazil.

The concentrations of mercury in surface sediments (<63 mu m fraction) from Santos-Cubatao Estuary, located in State of Sao Paulo, southeast Brazil, were determined to obtain the level of contamination in this highly polluted area. Fifteen stations distributed though seven rivers were sampled (156 samples collected) from September 1997 to August 1998 (12 stations sampled monthly) and during March, June, September and December 1998 (three stations sampled quarterly). The levels of mercury varied from 0.10 to 6.77 ppm, with the index of geoaccumulation of the rivers varying between grades 1 and 3 (annual average). The Cubatao is the most polluted river and the main agent of Hg dispersion in the study area. Geochemical data revealed that Hg levels in surface from Santos-Cubatao Estuary at present are as elevated as in past (for instance, by comparison 1980's), when Cubatao city was known as one of the most polluted cities in the world.