The basis and mode of heavy metal pollution of sampled water and plant (Ipomoea aquatica) obtained from Agodi Reservoir, Ibadan were investigated in this study. Of interest was possible gradient effect in the reservoir and variations that could be associated with changing climate. The aims were to determine the water quality and estimate ecological resilience of adjoining flora. Chemical analyses of the water samples were done using standard analytical methods while heavy metals in the water and plant samples were determined using Atomic Absorption Spectrophotometer (AAS). Heavy metal concentrations in sampled water were Cd 0.12, Co 0.19, Cu 12.40, Fe 43.75, Mn 64.81, Ni 0.17, Pb 0.005 and Zn 23.12 all measured in mg/L. All of these except for Cu and Pb exceeded the WHO standard. The concentration of heavy metals (mg/kg) in Ipomoea aquatic were Cd 0.24, Co 0.19, Cu 0.31, Fe 153.07, Mn 28.26, Ni 0.03, Pb 5.82 and Zn 35.90. The values obtained for Cd, Fe, Mn and Pb were higher while that of Co, Cu, Ni and Zn were lower to the WHO standards. Among the chemical parameters analyzed, only total hardness (TH) was higher, while SO42-, PO43-, NO3-, Cl- and Alk were lower than the WHO allowable limits for drinking water. One-way analysis of variance (T-statistics) showed that the chemical contents and heavy metals recorded in the water and plant samples were insensitive to their location inside the reservoir, exhibiting no gradient effect. Also, there was no seasonal variation (wet or dry season) in the heavy metal concentration and the chemical parameters measured except for TH which is higher in the dry season. Albeit, the higher concentrations of Cd and Pb in Ipomoea aquatic and Cd, Cu, Fe, Mn, Ni and Zn in the water are concerns for safety when water and plants from the reservoir would, one way or the other, find their way into the food chain.

The concentration of nine heavy metals in Oreochromis niloticus and Ipomoea aquatica inhabiting Agodi reservoir, Oyo State, Nigeria were investigated for twelve months. The concentrations of the metals were carried out using PG990 Atomic Absorption Spectrophotometer. The Ecological Risk Quotient (ERQ) was calculated using standard methods while the tolerability was determined with Box Plot analysis. The metal bioaccumulation in O. niloticus and I. aquatica followed the order Mn > Fe > Zn > Cu > Co > Pb > Cd > Cr > Ni and Fe > Zn > Mn > Cu > Pb > Cd > Co > Cr > Ni respectively. The results revealed O. niloticus to bioaccumulate the metals more than I. aquatica. Most of the examined metals were higher than the safety limit for the metals concentration in O. niloticus and I. aquatica. Also, I. aquatica had higher tolerability for heavy metals than O. niloticus. In O. niloticus, metal concentration, as well as ERQ, was higher in the wet season while no particular order was observed for I. aquatica. The ERQ result revealed that Cd, Fe, Mn, Zn, Cu and Pb exhibited a high level of ecological risk to both the aquatic flora and fauna as the ERQ values were above the risk limit of one (1). Thus, there is a significant environmental risk associated with heavy metals in the water body.

The concentration of nine heavy metals in Oreochromis niloticus and Ipomoea aquatica inhabiting Agodi reservoir, Oyo State, Nigeria were investigated for twelve months. The concentrations of the metals were carried out using PG990 Atomic Absorption Spectrophotometer. The Ecological Risk Quotient (ERQ) was calculated using standard methods while the tolerability was determined with Box Plot analysis. The metal bioaccumulation in O. niloticus and I. aquatica followed the order Mn>Fe>Zn>Cu>Co>Pb>Cd>Cr>Ni and Fe>Zn>Mn>Cu>Pb>Cd>Co>Cr>Ni respectively. The results revealed O. niloticus to bioaccumulate the metals more than I. aquatica. Most of the examined metals were higher than the safety limit for the metals concentration in O. niloticus and I. aquatica. Also, I. aquatica had higher tolerability for heavy metals than O. niloticus. In O. niloticus, metal concentration, as well as ERQ, was higher in the wet season while no particular order was observed for I. aquatica. The ERQ result revealed that Cd, Fe, Mn, Zn, Cu and Pb exhibited a high level of ecological risk to both the aquatic flora and fauna as the ERQ values were above the risk limit of one (1). Thus, there is a significant environmental risk associated with heavy metals in the water body.

The concentration of nine heavy metals in Oreochromis niloticus inhabiting Agodi reservoir, Nigeria, was investigated. Samples were collected at the inlet, centre and outlet of the reservoir. The concentration of the metals was determined with Atomic Absorption Spectrophotometer. Ecological Risk Quotient (ERQ) was used to numerically quantify the ecological risks associated with the mineral, while Box Plot was used to evaluate the tolerance of the fish to heavy metals. The ERQ, which was in the order of Mn > Fe > Zn > Cu > Cd > Pb > Cr > Co > Ni, showed that Ni, Co, Cr and Pb had values of less than one, implying that they did not constitute an ecological threat to the environment, while Mn, Fe, Zn, Cu and Cd were of ecological risk. Results revealed that the concentration of Cd, Co and Ni exceeded the bio-tolerance of the fish at the inlet, while Cd, Pb, Cu and Ni were beyond the tolerability of the fish at the centre. Similarly, the concentration of Co, Cu, Cr, Pb, Zn and Ni was above the tolerance limit of the fish. This showed that Fe and Mn were within the tolerance range of the fish and that the tolerability of the fish in relation to the location was inlet < Centre < Outlet.

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