Aquatic gastropods as mercury indicators in the Pantanal of Pocone region (Mato Grosso, Brasil)

Gold mining is the principal polluting activity in the municipality of Pocone at the northern limit of the Pantanal of Mato Grosso, Brasil and is characterized by the inadequate use of mercury in the gold extraction process. A way to contribute to the assessment of the environmental impact of mercury release in the Pantanal is to make use of bioaccumulation. Thus, determinations of total mercury in 188 Gastropods of three different species were made in seven different sampling sites during the dry and wet periods. Increase of mercury levels in the snails was restricted to the gold mining area and adjacent sedimentation areas. The largest mercury concentrations were found at the Tanque dos Padres site, reaching 2.04 mug g(-1) in individuals of Pomacea scalaris. In the other sampling sites, molluscs collected in the Araras/Piuval Bay complex, a mercury retention area, showed the largest mercury concentration, reaching up to 1.12 mug g(-1).