The Impact of a River on the Water Quality of Nearby Wells: A Case Study of Aluko River, Ilorin, Nigeria

Hand dug wells were sampled in 5 selected areas in the vicinity of River Aluko course, Ilorin. The ranges of the average value of the parameters studied are: 6.8-8.3 for pH; 325-524 mg/l for total hardness (TH); 0.039-0.69 for organic carbon content; 29-30 O C for temperature; 0.683-0.863 mg/l for total dissolved solids (TDS); 0.014- 0.068 mg/l for total suspended solids (TSS); 0.701-0.914 mg/l for total solids (TS); 6.60-21.50 mg/l for total alkalinity; 0.73-1.90 mg/l for chloride; 0.129-0.273 mg/l for nitrate; and 0.008-0.243 mg/l for sulphate. All the trace metals except Fe and K were within the WHO standard for drinking water. The % bioavialable metals (F1 + F2 + F3) for Fe, Mn, Ni, Zn, Co, Cd and Cu ranges between 87.1 and 95.4, 20.7 and 78.4, 39.3 and 68.7, 42.5 and 65.8, 64.0 and 86.6 and 92.9, 88.2 and 92.9, 40.00 and 60.10 respectively. The proportion of the mean metals concentrations of the bioavailable metals follows the order Fe > Cd > Co > Ni > Zn > Cu > Mn and the % bioavailable metal for the five locations is in the order: Ikokoro > Baboko > Ita-Amodu > Opomolu > Edun. The assessment of the well sediment using enrichment factor, EF, and geoaccumulation index revealed that Co and Cd from all the sampling points were evidenced as having more enrichment and mostly due to anthropogenic sources; whereas, Mn, Ni, and Zn were enriched from natural sources. Keywords: Bioavailability, Geochemical indices, Sequential extraction, Well-water