Impact of Iron Ore Mining On Heavy Metal Concentration In Soils of Kishushe Area In Wundanyi, Taita Taveta County

Abstract

The study of heavy metal deposition and accumulation in soils is of great interest due to the negative consequences it presents to environment and human health. Mining and milling activities such as ore grinding, ore concentration, and disposal of mine waste and waste water contribute to heavy metal pollution in the environment. These metals can be deposited in soils through discharge and dispersion to nearby agricultural soils. Once deposited in soil, they can be transmitted to ground water, surface water, food and atmosphere. Therefore, soil pollution directly threatens human health through its impacts on quality of food, drinking water and air. This study aimed at investigating and evaluating the impact of iron ore mining on heavy metal concentration in soils of Kishushe area in Wundanyi. The concentration levels as well as the distribution patterns were investigated. Fe was found to be the main constituent in soil samples at 8 – 12.5 %. Other elements that were determined at substantial levels were Mn (1,540 – 3,940 μg g-1), Ti (2,472 – 17,300 μg g-1), Cu (71 – 496 μg g-1), Zn (76 – 130 μg g-1), Sr (51 – 184 μg g-1), Zr (259 – 590 μg g-1) and Pb (26- 68 μg g-1). The global average values for agricultural soils are Fe (5%), Ti (10,000 μg g-1), Mn (2,000 μg g-1), Sr (1,000 μg g-1), Zr (550 μg g-1), Zn (300 μg g-1), Cu (120 μg g-1) and Pb (70 μg g-1). Pb, Zn, Sr and Zr levels were within the global values while Fe, Cu, Ti and Mn were slightly above. It was also observed that the levels were generally higher in study area than those recorded in the control area. The soil samples analysed by XRD technique showed the minerals quartz, albite, microcline and hornblende were present in substantial amounts. In conclusion, although the study showed that the contamination levels are low, it is important to put in place pollution mitigation measures and strictly adhere to them. It is also necessary to conduct follow-up studies to assess any changes.