Polycyclic aromatic hydrocarbons and organochlorine pesticides in floodplain soils: A case study of Onuku River in Okitipupa, Nigeria

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. Gas chromatography 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 high molecular weight PAHs (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. Furthermore, 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. Hence, regular monitoring of HMW-PAHs is required in the site.