Polycyclic aromatic hydrocarbons (PAHs) contamination of soils and water around automobile repair workshops in Eket metropolis, Akwa Ibom State, Nigeria

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are very toxic and persistent environmental contaminants. The paper is aimed at investigating the PAHs levels in soil collected at 0–30 cm depths from 5 automobile repair workshops within Eket metropolis/the underground water around its vicinity. The soils and water were prepared in the laboratory following standard procedures and were analysed for 16 US EPA priority PAHs using Gas Chromatography–Mass Spectrometer (GC–MS). Total PAHs concentrations in soil (Ʃ16 EPA PAHs) from all sampling sites were in the range of 0.82–12.98 mg/kg and 0.47–14.85 mg/kg for both dry and rainy seasons respectively and did not follow regular pattern with depth. Total PAHs concentrations in underground water from all sampling sites were in the range of 1.71–16.07 mg/l and 1.07–12.97 mg/l for both dry and rainy seasons respectively. According to European commission contamination classification and WHO maximum permissible limit for PAHs in drinking water (0.002 mg/l), the sites are said to be moderately to heavily contaminated. The total BaPeq for the soil and water samples indicated a moderate carcinogenic burden and hence low health risk. The calculated values obtained from diagnostic ratios shows that the PAHs in this study were from both pyrogenic and petrogenic sources. The correlation between total PAHs concentration in soil and water for both seasons indicated that the automobile repair activities had a moderate effect on the soil as well as the underground water around it. Therefore, boreholes should not be sited close to automobile repair yards to enable its suitability for domestic, irrigation and recreational usage.