Avaliação da qualidade da água sob impacto das atividades de implantação de garimpo no município de São Martinho da Serra

Abstract

This research was developed to evaluate the quality of waters under to the artisanal mining (garimpo) impact in a catchment, at the headwater of Ibicuí-Mirim River, in São Martinho da Serra - RS. The catchment area is 33.12 km2 and the landuse is predominantly agricultural and the extraction of gemstones activity. The water quality characteristics were evaluated periodically through the following parameters: temperature, pH, electric conductivity, turbidity, DO, BOD5, COD, total solids, suspended solids, dissolved solids, fixed solids, volatile solids, total and fecal coliforms. Five detailed investigations were also made in order to quantify the following parameters: alkalinity, Aluminium, Calcium, Copper, Chromium, Iron, Phosphate, Magnesium, Manganese, Nitrate, Sodium and Zinc. The water samples were collected in dry weather and during the rainfall events, enabling the obtaining of the runoff load pollutant. The results presented an increasing on the electric conductivity, turbidity and solids values due to mineral extraction. The wet weather event mean concentrations (EMC) were over than the ones obtained in dry weather, indicating that the runoff affects the water quality of the receiving body. Despite that mining is a recent activity in São Martinho da Serra, it is already causing local deterioration of the water quality. The results showed the necessity of a continuous water resources monitoring process, in order to minimize the negative environmental effects of the gemstones exploitation activity.