Garimpos de ouro e a contaminação ambiental por mercúrio : avaliação da dinâmica do contaminante em áreas de exploração garimpeira no sul da Amazônia, Brasil

Abstract

Mercury (Hg) is an environmental contaminant with high potential harmful to human and environmental health, when in toxic concentrations in the atmosphere, water or soil. Despite its danger, it is a metal widely used in gold mining areas. Its dynamics is directly related to the role played by the atmosphere, both in relation to global dispersion and in relation to its deposition from natural or anthropogenic emission sources. Considering the above, this study evaluated the dynamics of mercury, mainly its deposition and accumulation, in areas of gold mining by Artisanal and Small-scale Gold Mining (MAPEO) in southern Amazonia, Brazil, using as a basis forest areas and areas of soybean cultivation. In forest areas, when analyzing the dynamics of atmospheric mercury deposition on the different forest strata, there was a difference in the concentration of the metal between these strata, suggesting the existence of a vertical movement within the forest in both directions, that is, from the upper strata (canopy) to litter and soil, as well as from soil and litter to the forest canopy. It was recorded that there is a different dynamics of mercury deposition/accumulation between the study areas, due to the proximity to MAPEO areas in the region where the forest areas closest to the MAPEOs accumulate higher concentrations of mercury. Regarding soybean cultivation areas in the same region, it was shown that the concentration of mercury in the soil does not indicate contamination in the region, despite the proximity to the MAPEOs. In the analyzed crops, the atmospheric deposition of mercury is evidenced due to the higher concentrations of the metal in the leaves of the plants cultivated in the area close to the largest amount of MAPEO, which presented three times more mercury than the other areas. Thus, it is assumed that soybean has the potential to be used as a bioindicator of atmospheric mercury deposition of MAPEO. In general, the evidence of atmospheric mercury deposition in forested areas under the influence of MAPEOs, indicates the need for its conservation, as they actively participate in the dynamics of deposition/accumulation of the metal in the region, being the main responsible for 'capturing' these emissions. It is observed that regardless of the atmospheric dispersion of mercury in the environment, the forest areas closer to the MAPEOs accumulate higher concentrations of mercury. In contrast to soybean farming areas, where the mercury concentration in the soil indicates the absence of contamination in the region, despite the history of mercury emissions by MAPEO. Thus, it can be admitted that the dynamics of mercury in the region affects different vegetation cover differently, indicating the need to consider this activity as an important source of mercury to the environment and pointing to the need for environmental monitoring in the southern region of the country. Amazon to ensure the sustainability of production activities in the region.