Heavy metal pollution in waters and Soils from Mining activities in Mirelani, North-Eastern Tanzania

This study reports on heavy metal pollution in waters and soils from Tanzanite Mines in Merelani, Simanjiro District, Manyara Region, Tanzania. A total of 56 water samples from the study area were collected and analysed both "in situ" and in geochemical laboratory by AAS and HACH machines. A total of 100 mine waste and soil samples were collected from Mines of Blocks B, D and Merelani residential areas and analysed by using AAS machine. The uphill areas without mining activities gave background values for the soil samples. Majengo-KIA residential area, which is 25 km east of the mines gave background values for the water samples. The results revealed relatively high conductivity in the Mines (7040 µSiem) and Merelani water samples (1500 µSiem) compared to WHO (1998) acceptable values of (1000 µSiem). Total dissolved solids in Mines and Merelani water samples were (5,028 mg/I) and (694 mg/I) respectively, higher than the WHO (1998) which is (500 mg/I). There were high mean concentrations of Cd, Pb, Cr, Fe, Mn and Ni in mine water relative to WHO (1998) acceptable values. Concentration of the principal heavy metals Cd, Cu, Pb and Zn in soil samples showed similar trends as heavy metal concentration in .water. The high heavy metal concentration could be from discarded batteries the main source of energy for lighting systems in underground mines. Leaching of metal scraps, -explosive remnants, detonating and cabling wires and anthropogenic sources can as well contribute to heavy metal pollution. It is recommended to use rechargeables and solar energy as alternatives to batteries and treat water in areas of elevated heavy metals. In addition, it is suggested to investigate heavy metals wet and dry air deposition and effects on biota, gases concentrations and nutrient load in water sources. Moreover, conduct periodic water monitoring and research other pollution sources of heavy metals. The Merelani community should contain the discarded batteries, explosive remnants, metal scraps, cabling and detonating wires to dispose them as hazardous waste. Education to the Miners and the Merelani community about the effects of environmental pollution and degradation is crucial. There should be routine medical check ups for heavy metal toxicity to the mining communities.