Previsão de drenagem ácida em minas de carvão em Moatize, Tete

Abstract

Mining is an economic activity that has grown in the last 25 years exponentially in the central and northern regions of Mozambique. It has been used as a source of income for local families for their own subsistence, and by large companies that use the products from this activity to trade on the international market. Examples of mining explorations are found in the provinces of Manica, where gold is extracted, Nampula province, where heavy sands are explored, and in the province of Tete, where mineral coal is explored. This study aims to evaluate the possibility of generating acid mine drainage (AMD) in mineral coal mines in the district of Moatize, Tete province, proposing to carry out leaching tests of the waste material located in the piles and dams of rejects. The leachates produced during these tests were analyzed, where hydrogen potential (pH) values were obtained between 6,990 and 8,420, electrical conductivity (EC) values between 77.1 and 3720 μS/cm, sulfate (SO42-) values between 8,196 and 3008.190 mg/l, Calcium (Ca) between 0.421 and 78.877 mg/l, Iron (Fe) between 0.012 and 0.060 mg/l, Zinc (Zn) between 0.119 and 2.764 mg/l, Manganese (Mn) between 0.001 and 1.849 mg/l and Aluminum (Al) between 0.024 and 7.733 mg/l. The values obtained were compared to legal standards such as Decree nº 18/2004 of June 2nd (revised and updated by Decree nº 67/2010 of December 31st) which presents the environmental quality standards of the EPA and WHO for drinking water. human consumption, and there were values outside these limits established in the initial weeks of the leaching tests, but in the end these results were within the same limits. It can be concluded that the occurrence of acid drainage in these coal mines is unlikely, due to the constant dissolution of minerals that neutralize this process, which is manifested by the increasing trend in pH in these waste samples analyzed.