Mechanisms of physico-chemical 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 recovery in Brazil, has been an issue of concern. Reactions of Hg in the environment are quite complex, and can involve various Hg chemical species. Laboratory experiments were carried out on Hg-0 solubility, Hg complexation 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 mercury, and that the presence of humic acid enhances drastically the solubility of Hg-0. The soluble complex formed has a relatively lower interaction at the sediment/water interface and is more prone to spread through the aquatic environment.