PHYSICO-CHEMICAL ASSESSMENT AND TOXIC METAL LEVELS OF WATER SAMPLES FROM RIVER MANYERA, NIGERIA

Toxic metals (Cd, Cr, Pb and Hg) concentrations and physico-chemical properties of water from River Manyera, a tributary of the River Niger, were assessed over a 3-month period. Triplicate water samples were collected from 6 sampling stations on the River which has a gold ore area processing near it. Organoleptic parameters (Odour, Taste and Colour), physico-chemical parameters (pH, temperature, electrical conductivity, alkalinity, hardness, dissolved solids, suspended solids, dissolved oxygen, biological oxygen demand, nitrate, phosphate and chloride) and trace metals were analyzed. Results were compared to World Health Organization (WHO) and Standard Organization of Nigeria (SON) drinking water standards. Results of organoleptic parameters showed that they were brownish in colour and had objectionable taste and odour. Temperature ranged from 29.070 ± 3.010 to 34.300 ± 2.770°C across the sampling stations while pH had a range of 6.830 ± 0.925 – 8.167 ± 0.680. Total hardness ranged from 32.130 ± 2.910 to 38.898 ± 5.338 mg/L while total alkalinity (TA) had a range of 5.267 ± 0.358 – 10.637 ± 1.528 mgCaCO3/L. Electrical conductivity (EC) values ranged from 43.629 ± 6.351 to 248.330 ±2.887 µS cm-1. Nitrate, phosphate and chloride concentrations had ranges of 0.154 ± 0.004 – 1.959 ± 0.149, 0.019 ± 0.004 – 0.330 ± 0.312 and 0.855 ± 0.079 – 3.192 ± 0.802 mg/L, respectively. Mean Cd concentration ranged from 0.030 ± 0.017 to 0.122 ±0.036 mg/L while Pb and Cr had ranges of 0.044 ±0.010 – 1.307 ±0.290 and 0.037 ± 0.012 – 0.144 ±0.023 mg/L. Hg was undetected in all the sampling points across the months. Values for the physico-chemical parameters were within WHO and SON limits. However, ranges of mean concentrations of Cd, Pb and Cr exceeded WHO and SON limits and indicates that R. Manyera water was not fit for use as drinking water source.