Avaliação do impacto ambiental da mineração artesanal: contaminação por metais pesados em sedimentos do Distrito de Chifunde

Abstract

Sediment can originate from a variety of sources, including the decomposition of rocks, soil, organic debris, plant and animal remains, and also from activities human resources, such as civil construction, agriculture and mining. When the water carries these particles, can deposit them in different locations, creating layers of sediment around the over time. The purpose of this study is to analyze the concentrations and behavior of heavy metals in the soil, highlighting cases of contamination in Tete Province, specifically in the district of Chifunde, originating from activities artisanal mining. The study also addresses the main technologies and techniques (in-situ and ex-situ) for remediate contaminated soils. The analysis is carried out in a case of contamination of sediments by arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) in sediments from sediment basins and river located in the district of Chifunde and in the town of Luia. The comparison of results obtained with natural levels and established limits is essential for distinguish between high concentrations of anthropogenic origin and those naturally higher. Two analysis techniques were used, including fluorescence X-rays available at the National Institute of Mines and the mercury analyzer available in the laboratory of the Faculty of Medicine of the Eduardo Mondlane University. You results revealed maximum concentrations of 942.43mg/kg of As, 1mg/kg of Cd, 249.75mg/kg Cr, 3802.61mg/kg Cu, 4.33mg/kg Hg, 235.74mg/kg Ni, 249.57 mg/kg of Pb and 120.51mg/kg of Zn. The presence of Cd was not detected in the samples under study. Zn contamination was not verified, as all samples have concentrations below 200 mg/kg. In the determinations of Ni, Cu, Cr concentrations above the permissible limits were determined, thus constituting a risk to ecosystems as well as human health (TRADUÇÃO NOSSA).