MECHANISMS OF PHYSICOCHEMICAL INTERACTION OF MERCURY WITH RIVER SEDIMENTS FROM A GOLD MINING REGION IN BRAZIL - RELATIVE MOBILITY OF MERCURY SPECIES

Mercury accumulation in the food chain, as a consequence of gold recov ery in Brazil, has been an issue of concern. Reactions of Hg in the en vironment are quite complex, and can involve various Hg chemical speci es. Laboratory experiments were carried out on Hg-0 solubility, Hg com plexation and sorption on river sediments from a gold mining region in Brazil. The reactivity and the mobility of Hg species were considered . Results indicate that methyl mercury is more mobile than ionic mercu ry, and that the presence of humic acid enhances drastically the solub ility of Hg-0. The soluble complex formed has a relatively lower inter action at the sediment/water interface and is more prone to spread thr ough the aquatic environment.