DISTRIBUTION, RISKS AND SOURCE APPORTIONMENT OF POLYCYCLIC AROMATIC HYDROCARBONS IN SOIL AROUND CHARCOAL PRODUCTION SITES IN SAPELE, DELTA STATE, NIGERIA

Abstract

The study investigated the concentrations, risks and sources of the USEPA sixteen priority polycyclic aromatic hydrocarbons (16-PAHs) in soils around charcoal production sites in Sapele, Delta State, Nigeria. A stain-less steel auger was used in collection of a total of 21 surface soil samples, the PAHs concentration were determined by a gas chromatograph equipped with mass spectrometry (GC-MS). The concentration of the soil PAHs varied from 338 to 5082 µg kg^-1 for all the sites. The distribution pattern of PAHs in the soil were in the order of 3 Rings> 4 Rings> 5 Rings> 6 Rings and 2 Rings PAHs. The benzo(a)pyrene toxic equivalency (BaP_TEQ) and mutagenic equivalency (BaP_MEQ) values of PAHs in these soils ranged from 43.6 to 580 µg kg^-1 and 45.8 to 541 µg kg^-1 respectively. The ecological risk assessed using risk quotient suggested that there is low ecological risk to organisms in soil. The hazard index values indicated that there is the presence of non-carcinogenic effects on exposure to PAHs for children in 42 % of the soil samples. The total cancer risk values resulting from a child’s and an adult’s exposure of PAHs exceeded the target value of 1 × 10^-6 suggesting that exposure to PAHs in these soils carries a significant risk of cancer to humans. The isomeric ratio indicated that the major sources of PAHs in these soils is high temperature combustion processes