Análise da contaminação dos solos e ar por Hg e por Cr, Cu, Ni, Zn nos Distritos de Chiúta e Moatize

Abstract

Gold mining activities in the Moatize and Chiúta districts of Tete province are characterized by the use of rudimentary techniques for gold concentration, resulting in serious environmental and health problems due to the release of mercury (Hg) vapors during the amalgam burning process. The aim of this study was to determine the concentrations of Hg in soils and air, and of Cr, Cu, Ni and Zn in the soils of these districts. To achieve these objectives, we used the X-ray fluorescence (XRF) technique to determine Cr, Cu, Ni and Zn in sediment samples, and a LUMEX Hg analyzer (atomic absorption spectrometer) to measure Hg concentrations in sediments and air. However, the analyses of the metals Cr, Cu, Ni and Zn showed a high relative error, indicating low accuracy of the method and making a conclusive analysis of these elements impossible. For this reason, it was not possible to conduct a detailed discussion of these metals. Hg concentrations in the sediments reached alarming levels, with a peak of 4434 μg/kg in the basin sediments. In the air, Hg levels exceeded the limits established by the World Health Organization (WHO), with measurements reaching 53300 ng/m3 at specific points in the villages of Machinga and Kazula. The results confirm a punctual contamination by Hg in the areas studied, caused mainly by mining activities, especially in the vicinity of gold processing sites. This pollution poses a direct threat to the health of local populations and to environmental integrity, compromising soil quality and food security. Given the severity of the environmental impacts, it is essential to implement strict environmental control measures and adopt sustainable mining practices to mitigate the negative effects caused by human activities in the districts of Chiúta and Moatize.(TRADUÇAO NOSSA)