Evaluation of Heavy Metals on Wetland Biodiversity of Oluwa River (South west Nigeria) POME Poluuted Area

Abstract

The evaluation of Mg, Ca, Na, K, Cu, Mn, Fe, Hg, Zn and Pb concentrations in some component of biodiversity {Fish (Oreochromis niloticus);water ; soil sediment and submerge vegetation} from Oluwa River, Ondo State, Nigeria using X-ray fluorescence (XRF) technique is discussed. The river was stratified into four zones. Zone A, (ZA) was point of direct effluent discharge from the Palm Oil factory, zone B was point 50m away from ZA, towards the direction of water flow, zone C was point 100m away from ZA and zone D the control zone, was point 100m upstream from ZA without contact with the effluent. Physico-chemical parameters such as BOD, COD, DO2, Temperature, conductivity and pH were also measured. Biodiversity samplings were carried out once weekly for 4 weeks and samples collected were prepared for analyses/measurements. The analytical samples are irradiated with high energy electrons of 109Cd to produce fluorescent X-rays was produced which passes to the Silicon-lithium detector through Mo target as a source of monochromatic X-rays. The spectrum of energy generated on the detector was processed by a Multi- Channel Analyzer to obtain analytical data. The intensity of the fluorescent X-rays on the detector is proportional to the concentration of the individual element of interest in the sample. This method can identify up to 30 or more elements at the same time. The results showed varying levels of heavy metals in the fishes, Water, Bottom sediment and submerged vegetation (biodiversity). The concentrations of Cr, Mn, Cu, and Ni in the fishes were much higher than WHO and FEPA maximum permissible limits, while the concentrations of Zn and Pb were lower than the standards. Results showed that pH; chemical oxygen demand (COD); biological oxygen demand (BOD); conductivity and temperature (ToC) of POME were critical for the survival of aquatic organisms. Water pH; dissolved oxygen (DO); COD; BOD and ToC were most critical (P<0.05) at ZA and improved along ZC, while there was no effect in ZD. There were positively high correlation between DO/pH; COD/pH; BOD/pH; conductivity/pH; ToC/pH/COD/BOD and conductivity. Negative correlation also existed between COD/DO; BOD/DO; conductivity/DO and ToC/DO. Regression analyses indicated high coefficient of determination R2 between the water parameters and low R2 between DO/ToC which had equation as DO = 72.0-2.45ToC. Biodiversity mineral concentration was excessively high due to POME pollution, indicating possible subtoxic effect. The results suggest that the lake is polluted with Cr, Mn, Cu and Ni and the consumption of fishes of the lake is life threatening to man. This is a confirmation that fish in river Oluwa within the polluted areas must have either migrated out of the zones or died due to POME toxicity.