Occurrence, source and risk assessment of polycyclic aromatic hydrocarbons in Ogun River and Lagos Lagoon, Southwest, Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants that have raised great concern worldwide because of their ubiquity and persistence in both marine and terrestrial environments. Ogun River and Lagos Lagoon are potential hotspots of PAHs contamination because they receive organic pollutants from various anthropogenic sources within and outside the surrounding cities. This study investigated the occurrence, sources and risk assessment of PAHs in Ogun River and Lagos Lagoon. One hundred and twenty samples from forty locations were collected and analyzed for sixteen PAHs. The target compounds were analyzed using Gas Chromatograph–Mass Spectrometer (GC–MS). The total PAHs (∑16PAHs) concentration ranged from 5308–7081 ng/L with an average of 6327 ng/L for Ogun River and 4786–6647 ng/L with an average of 5479 ng/L for Lagos lagoon. Results obtained from the source diagnostic ratios and factor analysis suggested inputs from natural processes like the combustion of biomass and coal as well as anthropogenic sources for both Ogun River and Lagos Lagoon. The PAHs risk assessment indicated that the water could pose serious threat to human health but the carcinogenic risk assessment indicated negligible health hazard.