Seasonal distribution, source apportionment and risk assessment of polycyclic aromatic hydrocarbons in groundwaters in Owo, Southwestern Nigeria

The study focused on evaluating the seasonal distribution, source apportionment, and probabilistic risk assessment of polyaromatic hydrocarbons (PAHs) in groundwater. Groundwater samples were obtained from Owo, southwestern Nigeria and subjected to liquid-liquid extraction and quantified using gas chromatography-mass spectrometry. Total PAH concentrations varied from about 180 to 23,600 ng/L during the dry season. The wet season, on the other hand, exhibited a wider range, from about 1,550 to 150,000 ng/L. Seasonal variations were also found in PAH types and concentrations, with relatively higher concentrations recorded during the wet season. Diagnostic ratios and positive matrix factorization indicated that coal/biomass combustion and traffic-related vehicular emissions were the prevalent sources of PAHs in groundwater. Health risk assessment indicated potential carcinogenic risks (incremental lifetime cancer risk (ILCR) . 1E -04), while ecological assessment suggested medium (RQ(NC) , 800 and RQ(MPC)> 1) and high ecological risks (RQ(NC)> 800 and RQ(MPC)> 1). The study reflected the need for effective mitigation strategies.