Efeitos da actividade mineira na qualidade da água da bacia hidrográfica do Rio Zambeze no distrito de Moatize

Abstract

Mining generates economic benefits, however there are several cases where it causes impacts on the environment, particularly on water resources. Mozambique registered a significant development of the mining industry in recent years, due to to its geology rich in mineral resources and relative political stability. the province of Tete, with a reserve of 23 billion tons, is a reference for the operations of coal mining, particularly in Moatize. The Moatize coal basin, in the province of Tete, is part of the hydrographic basin of the Zambezi River, with a total area of ​​about 1.37 million km2 , and is characterized by a intense mining. The watershed area of ​​the Zambezi River in Mozambique occupies about 137,000 km2 . As Mozambique is a developing country, mining operations take place in rural areas where the population depends of surface and underground water reservoirs as a source of water for consumption and domestic use. Due to this fact, it is essential to assess the impacts of the mining activity on water resources. The present study was carried out in Moatize District, Tete Province, Mozambique, with the aim of evaluating the impact of mining activities on water resources. You field parameters and samples were collected at 16 points, in a period of sampling between the months of September and October 2020. These were collected taking into account its position in relation to 3 mining companies located in the District of Moatize and were analyzed in the Department of Chemistry of Eduardo Mondlane University and the National Laboratory of Hygiene, Water and Food (LNHAA). With the study it was observed that the pH values ​​(6.2±0.1 - 8.2±0.0) in the area were close to neutral to alkaline. Mining activity has negative effects on the water quality not only downstream but also upstream, due to the nature topography of the region. The amounts of Electrical Conductivity (138.7±1.5 – 11.2x103±0.0, μS/cm), Total dissolved solids (89.0±1.0 - 7338.0±79.7, mg/L), Sulfates (<0.04 – 1233.8±0.8, mg/L), Iron (BDL – 2.88±0.02 mg/L) and ions general increase due to mining activities carried out in the region, with the mining influence greater on groundwater than surface water courses.