[01] Abata Emmanuel Orimisan, Department of Chemistry, School of Sciences, Federal University of Technology, Akure, Nigeria. [02] Aiyesanmi Ademola Festus, Department of Chemistry, School of Sciences, Federal University of Technology, Akure, Nigeria. [03] Adebayo Albert Ojo, Department of Chemistry, School of Sciences, Federal University of Technology, Akure, Nigeria. [04] Ajayi Olabode Olumuyiwa, Department of Chemistry, School of Sciences, Federal University of Technology, Akure, Nigeria.

This study was carried out to investigate seasonal variations of polycyclic aromatic hydrocarbon (PAHs) in sediments of Ala River, South-west, Nigeria. The total amount of PAHs (ΣPAHs) concentration ranged from 1.70 - 5.73 μg.g^-1 dry weights during the wet season and from 2.93 - 6.05 μg.g^-1 dry weights during the dry season. The total concentrations of PAHs were higher in most of the sites during the dry season and 70% and 30% during the wet season. The result showed that the contaminants in Ala River were mainly a mixture of pyrogenic, petrogenic and few sources from vehicular emission using PAH diagnostic ratio. The ΣPAHs are between effect range low (ERL) and effect range median (ERM) but did not exceed ERM in all samples both in wet and dry season. The results of the present study showed ΣPAHs were below 1 μg.g^-1dw at all sampling locations. The principal component analysis was used to determine the origin of the PAHs. Analysis of Principal Component Analysis (PCA) indicated that the PAH variables could be reduced to six components, which accounted for 73.14% of the total variance for the data. The cluster analysis confirmed four major clusters arrangement of PAH concentration and this confirmed that Ala River contaminants were both from petrogenic and pyrolytic sources.

PAHs, Sediment, Ala River, Cluster Analysis, Petrogenic, Pyrogenic

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