Sediments and Water Column Contamination by Heavy Metals in Ekulu River, Nigeria: Ecological and Human Health Risk Assessment

Abstract

Acid mine drainage from a defunct coal mine, agricultural run-off and indiscriminate waste disposal constitute major threat to the quality of Ekulu river of Enugu State, Nigeria. In this study, Ekulu river sediments and water column pollution by heavy metals and the associated ecological and human health exposure risks were assessed. The heavy metals were measured using atomic absorption spectrometry. The parameters used in assessing the pollution of the sediments were contamination factor, contamination degree, geochemical accumulation index and pollution load index whereas the ecological risk of the heavy metals in the sediments was assessed using potential ecological risk index. The parameters employed in assessing the carcinogenic and non-carcinogenic risks of exposure by humans to the heavy metals were hazard index and risk index. The results obtained indicate that the chromium and lead input into the sediments around the defunct coal mine area during the wet season was significant and most probably due to the discharge of acid coal mine drainage into the river. Elevated values of ecological and human health exposure risks around 4 km distance away (Damija) from the defunct coal-mine area are most likely due to anthropogenic activities.