Abstract:
Heavy metals are released into water ecosystems naturally or via human activities. Weathering and decomposition of metal containing rocks and ores can transfer heavy metals into waters and have led to human exposure. This research was aimed to investigate the concentration levels and associated risks of selected heavy metals including Fe, Cu, Zn, Mn, Pb, Cr, Cd, Co and Ni in gold mining drainage receiving Tumet River and Shegol pond found in Menge district of Assosa Zone, Benishangul-Gumuz Regional State, Ethiopia. Water samples were collected from four sampling sites (i.e., three sites from Tumet River and one sampling site from Shegol Pond). Wet digestion technique was employed to prepare the water samples for analysis of the selected heavy metals using flame atomic absorption spectrophotometer (FAAS).The mean (±SD) concentration levels of the metals observed were in the range of 0.023±0.0025-43.35±1.394 mg/l and 0.019 ± 0.0015- 39.92 ± 1.28mg/l in dry and wet seasons, respectively in Tumet River, and for Shegol pond the range was 0.032±0.001-27.07±2.44 mg/l and 0.030±0.00057- 26.41±2.11mg/l in dry and wet seasons, respectively for the studied metals. The result of non-carcinogenic human health risk assessment showed that except Cr, Zn and Mn the other studied heavy metals (Fe, Cu, Pb, Co, Cd and Ni) can individually (HQ > 1) pose human health risks in both dry and wet seasons. In addition, the hazard index result indicate that at each sites the studied heavy metals can jointly pose non-carcinogenic risks to the local communities (HI >1). Furthermore, the cancer risk assessment result further indicated that the heavy metals such as Pb, Cr, Cd, and Ni (ILCR >1*10-4 or ILCR > 1*10-6) can possibly cause carcinogenic risk to the surrounding community groups for both seasons and water systems. Our results strongly urge an urgent policy and management interventions by regional as well as federal governments to avert the possible effects/risks to human and the environment caused by this heavy metals pollution due to the various forms of mining activities running in the studied region.
