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Water quality and sediment pollution load index of Oyan dam, Ogun river, Ogun state, Nigeria

Water and Sediment analysis are ways of evaluating the quality of a water body using different mathematical models. Samples were collected fortnightly for 3 months at 3 sampling points. Water samples were analyzed for pH, DO, EC, turbidity, BOD, COD, TDS, TN, TOP, Cl^-, Na²⁺, Alkalinity and Ca²⁺ and sediment samples were analyzed for metals (Fe, Mg, Zn, Pb, Cr, Cu, and Ni), NO₃^-, PO₄^3- and pH. Water Quality Index (WQI) was used to determine the quality of water sample while the degrees of metal pollution were evaluated using the following pollution indexes; Enrichment ratio (Er), Pollution load index (PLI) and Geo-accumulation index (Igeo). All water parameters had values below the WHO standards except for Na⁺. The WQI for each site indicated that the water is of good quality with values ≤ 50. The result of the metal analysis in the sediment followed the trend Mg>Fe>Zn>Cu>Pb>Ni>Cr. N0₃^- and P0₄^3- are higher than WHO standards but the metal analysis values fall within or below the range of WHO standards. The Er shows that Cu, Zn, Cr, Pb and Ni have values less than 1 (<1), PLI values are less than 1 (PLI <1). The following metals showed high values of Igeo index; Mg (Igeo >5), Fe (Igeo >2<3), Zn at sampling sites 2 and 3 (Igeo >4<5). Conclusively, the water is of good quality and the sediment showed no pollution from the metals except for Fe, Zn and Mg.

 

Keywords: Metals, Pollution Load Index, Sediment, Water Quality Index

*Correspondence: tyloveng@gmail.com, 08068496117

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