Influence of mine drainage on water quality along River Nyaba in Enugu South-Eastern Nigeria

摘要

Major and trace elements concentration were measured in water samples collected in and around Okpara coal mine in Enugu southeastern Nigeria to investigate the influence of mine drainage on the quality of water. The cations and trace elements were determined by ICP- MS while the anions were measured by spectrophotometer and titration methods. Field parameters such as pH, temperature and conductivity were determined in the field using standard equipment. The results show that the water is acidic to moderately acidic (pH 2.84 to 6.69) with pH increasing along the flow direction. The mean values of pH (4.66 (dry), 4.22 (wet), Colour (334.34 TCU (dry), 153.11 TCU (wet) and turbidity (53,67 NTU (dry), 17.43 NTU (wet) as well as iron (6.35 mg/L(dry), 5.14 mg/L(wet), aluminum(1.14 mg/L(dry), 4.30 mg/L(wet), manganese (1.43 mg/L(dry), 5.36 mg/L (wet) and nickel, 0.053 mg/L (wet) recorded in the dry and wet seasons are above levels recommended by WHO for drinking water and other domestic purposes. Mean levels of fluoride (5.4 mg/L) with ranged of 0.00 to 45 mg/L, potassium (12 mg/L) with ranged of 1.17 to 27.85 mg/L and nickel (53.10 µg/L) with ranged of 1.50 to 309.30 µg/L, as well as maximum levels of chromium (100 µg/L) with ranged of 0.05 to 100 µg/L , chloride(400 mg/L) with ranged of 40 to 400 mg/L, nitrate(1012 mg/L) with ranged of 158 to 1012 mg/L and sulphate (517 mg/L) with ranged of 10 to 512 mg/L obtained in the wet season are above the WHO maximum permissible level. Generally, the levels of the elements decrease with distance away from the mine waste except for nitrate and fluoride. Thus the quality of the water is most probably influenced by acidic mine drainage and it impact on human health and the environment could be severe. Microbial assessment and element speciation are recommended for further quality assessment in the study area.