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.
In this study, the ecological and human health exposure risks due to the effects of abattoir and power station on heavy metal input into the sediments of Oji River in Enugu State Nigeria were assessed. Heavy metals in the sediments were measured using atomic absorption spectrometry. Pollution of the sediments was assessed using: contamination factor (CF), degree of contamination (CD), geochemical accumulation index (I geo ) and pollution load index (PLI), whereas the ecological risk was assessed using potential ecological risk index. Non-carcinogenic risks of exposure by humans to the heavy metals were assessed using hazard index. Obtained results indicate that the abattoir contributed to heavy metal input into the sediments significantly (unlike the power station) and most likely due to the use of waste tires at the abattoir as fuel. All pollution parameters (CF, CD, I geo and PLI) reveal that pollution of the sediment with heavy metals around the abattoir is most profound and the ecological risk of heavy metals in the sediments is very high. Non-carcinogenic risk of exposure to heavy metals due to inadvertent ingestion and contact with sediments is insignificant.
This study investigated the potential of nutrients input into Ekulu river to cause unwanted growth of algae that could adversely affect the aquatic ecosystem. The concentrations of nitrogen, silicon and phosphorus in the water column of Ekulu river were determined in addition to determining the pH, electrical conductivity, total dissolved solids, total organic carbon, dissolved oxygen, biochemical oxygen demand and chemical oxygen demand following standard procedure by APHA (1998). The results show that there was increase in concentration of phosphorus, nitrogen and silicon in the rainy season. The N/P ratios varied from 6.2-15.7 indicating the possibility of nitrogen being the limiting nutrient as ratio values are less than the optimum value of 16. The Si/N ratio for both dry and wet seasons varied from 2.7-9.1 indicating that Si input into the river is adequate and favourable to the growth and development of diatoms rather than non-diatom phytoplankton species such as dinoflagellates. Consequently, there is no significant risk of eutrophication at the present level of nutrients and silicon in Ekulu river.
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