Levels and risk assessments of polycyclic aromatic hydrocarbons in soil situated around unlined dumpsite in Okpunoeze, Nnewi, Nigeria

Abstract

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are organic pollutant found in the soil which can cause several health effects to human beings and the environment. The study was aimed at evaluating the concentration level of PAHs of soil located around an open/unlined dumpsite. 32 samples comprising of 16 samples each of upstream and downstream (control) were obtained in both seasons. The concentration of PAHs was ascertained using gas chromatography interfaced with a flame ionisation detector (FID). Toxic and mutagenic risk assessments were employed to evaluate the toxicity risk. The probability of cancer health risks was determined through dermal and ingestion routes. Molecular PAHs ratios were used to predict the potential sources. The PAHs concentrations in the upstream and downstream ranged from ND – 120.6 µg/kg and 0.03–7.08 µg/kg respectively. Total PAHs concentrations in the upstream and downstream ranged from 20.57–144.28 µg/kg and 11.43–18.84 µg/kg respectively. The upstream samples PAH concentrations were greater than the downstream site in both seasons. The PAH concentration in the wet season was greater than the dry season values, which was possibly due to leachate pollution. The four-ringed PAHs were the most prominent in the PAHs, while the six-ringed PAHs were the least dominant PAHs for both seasons. Benzo(a)pyrene values estimated from Ba and Ba were found to have possible chances of carcinogenic and mutagenic risks in the soil samples for both upstream and downstream locations. There were no chances of possible carcinogenic risks through ingestion and dermal exposure routes. The values of diagnostic ratios obtained confirmed that PAHs sources are predominantly from pyrolytic sources for upstream location. Downstream diagnostic ratios values had a slightly dominant petrogenic source than the pyrolytic sources.