Risk Assessment of Polycyclic Aromatic Hydrocarbons PAHs in Soils and Tubers Crops Collected from Ikot Oborenyin, South-south Nigeria

Aims: This study aimed to investigate the levels, patterns sources and health risk of Polycyclic Aromatic Hydrocarbons (PAH) in soils and root crops of Ikot Oborenyin, Nigeria.

Study Design: Samples were collected from two sites; the study and control sites. At each site, a plot was chosen with a variety of tuber crops. Manihot esculenta, Colocasia esculenta, Dioscorea rotundata and Dioscorea dumentorum.

Methodology: Concentrations of 16 priority PAHs were measured using gas chromatography- Mass spectrometry. Health risk assessment was carried out using the toxicity equivalency factor method.

Results: Results revealed detectable levels of the 16 PAHs in soil and plant samples, with concentrations ranging from 19.8 µg/kg to 80.7 µg/kg. PAH levels in tuber crops were Manihot esculenta (12.3-74.8 µg/kg); Colocasia esculenta (26.2-110.4 µg/kg); Dioscorea rotundata (21.5-166.4 µg/kg) and Dioscorea dumentorum (19.3-80.7 µg/kg). Higher molecular weight PAHs were dominant in soils with a 4 ring> 3 ring>5 ring >6 ring> 2 ring gradient. Lower molecular weight PAHs were the most abundant in the crop samples, accounting for 56.8% to 69% of plant PAHs. Results show that combustion of liquid fuel was the primary source of PAHS. BaPeq values calculated for soils and plants were higher than the allowable target values for soils and vegetables.

Conclusion: The study revealed the potential for carcinogenic risks associated with soils and some food crops obtained from Ikot Oborenyin, Nigeria, consequently, remediation of the soils is suggested to prevent adverse effects.