Distribution dynamics and health risks of polyaromatic hydrocarbons and heavy metals in the anthropogenically impacted Omi-Asoro Stream, Nigeria

Abstract

The study carried out concerted analytical measurements of twenty polyaromatic hydrocarbons (PAHs) and eighteen heavy metals in the Omi-Asoro Stream, Ilesa, Nigeria to unravel their sources and the impacts of anthropogenic activities around it. Samples from the stream water were collected in March 2023. The resident PAHs were subjected to solid-phase extraction (SPE) and analyzed on a gas chromatograph-mass spectrometer. The acid-extracted heavy metals were also analyzed with an inductively coupled plasma-optical emission spectrometer (ICP-OES). Results showed that naphthalene (6.00 ± 7.79 μg/L) and fluoranthene (2.99 ± 4.24 μg/L) were the two dominant PAHs in the stream water. Similarly, Fe and Zn, with concentrations (μg/L) of 1291 ± 2361 and 53.1 ± 89.3, respectively, were the dominant heavy metals. Fe concentration constituted 84.4% of the total heavy metals in the water. Using principal component analysis (PCA), the PAH sources were traced to internal combustion engines, biomass burning, and pesticides/wood preservatives. The heavy metal sources were resolved to internal combustion of engines, metallic wear/rust, electronic devices, geogenic releases and agrochemicals. The risk assessment showed that among the detected PAHs, benzo(a)pyrene constituted a carcinogenic effect on humans. The heavy metals which posed carcinogenic effects included As, Ni, Cd and Cr. Thus, the industrial and agricultural activities, as well as emissions from the internal combustion of engines in the area released the environmental pollutants which adversely impacted the stream.