ASSESSMENT OF HEAVY METALS IN SOIL FROM THREE DIFFERENT RIVERS IN ABEOKUTA METROPOLIS

This study was carried out to examine heavy metals concentrations in the soil samples rivers at of Ita–Oshin, Lafenwa, and Sokori areas of Abeokuta Metropolis, Ogun State, Nigeria. Sediment samples were analyzed for selected heavy metals (Cd, Cr, Pb, Zn, Mn, Cu, As, and Fe) by Atomic Absorption Spectrophotometry method. The results revealed heavy metals concentrations ranging from 2.07mg/kg – 2.98mg/kg for Cd, 1.12mg/kg – 4.66mg/kg for Cr, 5.15mg/kg – 17.18mg/kg for Pb, 5.55mg/kg – 14.04mg/kg for Zn, 174.62mg/kg – 218.83mg/kg for Mn, 0.28mg/kg – 1.47mg/kg for Cu, 1.15mg/kg – 2.32mg/kg for As and 4.53mg/kg – 7.38mg/kg for Fe in the three locations respectively. The results showed that the concentrations of Zn, Pb, Cu, Cr, and As in the soil are low but may require monitoring to prevent an increase. The concentration of Mn was higher than the stipulated limit of 50.0mg/kg set by USEPA and this may constitute a risk to the people living in the environment. However, the soil is less contaminated but may increase if the area is not managed well to continue to enhance its quality. The results showed that the mean concentration of these heavy metals were 1.41 mg/kg cadmium, 1.06 mg/kg arsenic, 0.32 mg/kg copper, 0.84 mg/kg chromium, 19.54 mg/kg iron, 2.43 mg/kg manganese, 3.53 mg/kg lead, 1.61 mg/kg zinc; 1.40 mg/kg cadmium, 1.05 mg/kg arsenic, 0.36 mg/kg copper, 0.84 mg/kg chromium, 19.56 mg/kg iron, 2.44 mg/kg manganese, 3.48 mg/kg lead, 1.78 mg/kg zinc; 1.44 mg/kg cadmium, 1.03 mg/kg arsenic, 0.38 mg/kg copper, 0.85 mg/kg chromium, 19.70 mg/kg iron, 2.46 mg/kg manganese, 2.98 mg/kg lead, 1.66 mg/kg zinc. These concentrations were compared with WHO Standard which indicated high levels for Cd, Pb, Zn, and Mn. The high levels of theses heavy metals were attributed to the discharge of untreated industrial wastes into these rivers, which indicated the level of pollution in those rivers. Consequently, River Ogun is polluted with high levels of toxic heavy metals like Cd, Pb, Zn and Mn. This will have long-term effects on the health status of the people that are using the river on daily basis for drinking and other purposes without proper treatment before use.