Polycyclic Aromatic Hydrocarbons and Organochlorine Pesticides in Floodplain Soils: a Case Study of Onuku River in Okitipupa, Nigeria

Abstract We report on the sources, distribution, and toxicity of sixteen polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in floodplain soils of the Onuku River in Okitipupa, Nigeria. A simple, low-cost, analytical method based on ultrasonic extraction followed by silica gel cleanup and gas chromatography analysis was used to quantify the compounds. Five PAHs with an average trace concentration of 0.25 (benzo(a)pyrene) – 21.3 µg/kg (benzo(g,h,i)perylene) were identified, while the OCPs residues ranged from 0.116 (aldrin) – 2.18 µg/kg (p,p’-DDT). High spatial distribution of OCPs was mostly recorded among the sampling sites, whereas chlorothalonil, δ-BHC, and p,p’-DDT were the most predominant. High distribution of HMW-PAHs with 6- ring (75.6%) as the most predominant compositions in the study area. The diagnostic ratio of specific PAH compounds revealed pyrogenic origin. Further, the toxic equivalency factors (TEFs) evinced that the carcinogenic potency of (benzo(a)pyrene and the equivalent concentration (BaPeq) of PAHs load were relatively low.