Environmental drivers influencing polycyclic aromatic hydrocarbon (PAH) mobilization in rainwater: Insights from physicochemical correlations in Ondo State, Nigeria

This study investigated the influence of seasonal meteorological conditions and physicochemical parameters on the mobilization of polycyclic aromatic hydrocarbons (PAHs) in harvested rainwater across Ondo State, Nigeria, a petroleum impacted region. Rainwater samples were collected monthly from April to August 2024 and analyzed for sixteen United States Environmental Protection Agency priority PAHs, alongside pH and electrical conductivity. The objective was to evaluate the combined effects of rainfall intensity and water chemistry on PAH occurrence and associated health risks. Total PAH concentrations increased markedly during the mid wet season, particularly between July and August, coinciding with intense rainfall. Both low and high molecular weight PAHs, including fluoranthene, pyrene, phenanthrene and anthracene, were dominant. Significant positive correlations were observed between total PAHs and pH and electrical conductivity, indicating strong physicochemical control on PAH behavior in rainwater. Health risk assessment showed hazard quotients exceeding unity for oral and dermal exposure, while incremental lifetime cancer risk values surpassed recommended limits, especially for children. Diagnostic ratios suggested predominantly pyrogenic sources. Overall, seasonal rainfall and water chemistry jointly regulate PAH mobilization and associated health risks in harvested rainwater.