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

Water from River Manyera, a tributary of the River Niger, was tested for toxic metals (Cd, Cr, Pb, and Hg) and physico-chemical properties over a three-month period. Six sampling stations along the river with a gold ore processing region were used to gather triplicate water samples. Physico-chemical parameters (pH, temperature, electrical conductivity, alkalinity, hardness, dissolved solids, suspended particles, dissolved oxygen, biological oxygen requirement, nitrate, phosphate, and chloride) as well as trace metals were investigated. The results were compared to drinking water standards set by the World Health Organization (WHO) and the Standard Organization of Nigeria (SON). Organoleptic characteristics revealed that they were brownish in colour with an unpleasant taste and odour. Temperatures at the sampling stations ranged from 29.070 3.010 to 34.300 2.770°C, while pH levels varied from 6.830 0.925 to 8.167 0.680. Total hardness was measured in milligrammes per litre and ranged from 32.130 2.910 to 38.898 5.338 mg/L, while total alkalinity (TA) was measured in milligrammes per litre and ranged from 5.267 0.358 to 10.637 1.528 mgCaCO3/L. The values of electrical conductivity (EC) ranged from 43.629 6.351 to 248.330 2.887 S cm-1. The concentrations of nitrate, phosphate, and chloride were 0.154 0.004 – 1.959 0.149 mg/L, 0.019 0.004 – 0.330 0.312 mg/L, and 0.855 0.079 – 3.192 0.802 mg/L, respectively. Cd concentrations varied from 0.030 0.017 to 0.1220.036 mg/L, whereas Pb and Cr concentrations were 0.044 0.010 to 1.307 0.290 mg/L and 0.037 0.012 to 0.1440.023 mg/L, respectively. Throughout the months, no Hg was detected in any of the sampling stations. The physico-chemical parameters all fell within WHO and SON guidelines. However, the ranges of mean Cd, Pb, and Cr values exceeded WHO and SON standards, indicating that R. Manyera water was unfit for drinking.

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