Influence of mining related activities on levels of mercury in water, sediment and fish from the Ankobra and Tano River basins in South Western Ghana

Abstract

Background: Mercury (Hg) used in gold amalgamation is a major source of contamination in developing countries. The present study evaluates the concentrations of total mercury in water, sediment and fish from the Ankobra and Tano Rivers, which drain the major gold mining areas in Ghana. Total mercury (T‑Hg) analysis was carried out using an atomic absorption spectroscopy (Perkin Elmer model 5100PC) equipped with a flow injection analysis system (FIAS, AS‑90). Results: Water, sediment and fish T‑Hg concentrations were 0.145–1.078 μg/L, 23.39–73.31, and 0.03–0.443 μg/g dw, respectively in Ankobra basin, while in Tano basin levels of 0.214–0.250 μg/L, 14.43–21.51, 0.068–0.413 μg/g were found for water, sediment and fish, respectively. The T‑Hg concentration in water from both basins were within the World Health Organization threshold limits for drinking water except at River Asuo Kofi. Concentration of T‑Hg in the sediment exceeded Environmental Protection Agency ecotoxicological threshold in some sampling stations, suggest‑ ing potential adverse ecological effects. T‑Hg levels in fish from both basins were lower than the WHO value (<0.500 μg/g (wet wt). The target hazard quotient values, suggest that human should minimizing meals/week of the analyzed species to avoid deleterious effect during lifetime. Conclusions: The results suggested that mining activities significantly contribute to the considerable environmental Hg contamination in both Ankobra and Tano River basins. Therefore Hg levels should carefully monitored and con‑ trolled to reduce its inputs and mitigate potential health consequences of Hg accumulation in the environment.