Avaliação dos níveis atuais de mercúrio total em área contaminada no município de Descoberto - MG

Abstract

In December 2002 outcrop of metallic mercury was observed in the town of Serra of Grama, rural municipality of Descoberto - MG. The metal came in place after the corrections made by backhoe on the access road to the area. In the region of gold mining were developed from 1824 until the mid- twentieth century. Mercury (Hg) is used in the final stage of mining for separating gold and other minerals metal concentration. This study aims to evaluate the current concentration of total mercury in the contaminated area in the municipality of Descoberto - MG. Having specific objectives: to assess the levels of total mercury over soil profiles; evaluate the concentration of total mercury in river sediments; analyze the variability of the mercury concentration in the dry and rainy seasons and compare the concentration of mercury found with levels allowed by Brazilian law and with previous studies in the area. The proposed methodology consisted of collecting samples of soil and sediment at sites defined by reconnaissance visits, survey of existing historical data and results obtained in other studies already conducted on site. Quantification of total mercury in soils showed values between 0.03 and 16.55 mg / kg. The results obtained in the evaluation of total mercury in sediments bought contamination of river sediments between 0.03 and 1.67 mg / kg. Regarding the variability of the mercury concentration in the dry season and rainy noticed an increase in mercury levels in soils and sediments in the rainy season. It is concluded that mercury contamination remains in the area not happening its reduction with time as shown by the results obtained in this work. The significant increase in the concentration of mercury in sediments and soils in the rainy season is justified as a consequence of the transport of soil and sediment contaminated materials due to the large volume of water that characterizes this season. Points previously chosen as a reference showed mercury concentrations. These new outbreaks may be related to the spread of the contaminant in the atmosphere since the metallic mercury has high volatility. The place is completely abandoned by the authorities and is not verified any effective action by the government in relation to the remediation of the site. The results shows the possibility of transfer of mercury to the surrounding population, contamination extrapolate beyond the area initially assessed by environmental agencies.