Abstract

The levels of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in surface water, sediment, fish (Mugil cephalus) and prawn (Penaeus monodon) from fishing areas affected by oil and gas exploration activities, along Bonny River, Southern Nigeria. Samples were collected for a period of four months (July to October) and analyzed using Gas chromatography coupled to flame ionization detector (GC/FID). Biota-sediment accumulation factor (BSAF) and Bioaccumulation factor (BAF) were assessed using the accumulated levels of PAHs in the biota. Benzo(a)anthracene was the most dominant congener in the surface water, sediment, fish, and shrimp samples comprising about 75, 52, 50 and 17%, respectively, of the sixteen PAHs detected. Total PAH concentrations ranged from 0.07 to 3.67 mg/L in water, 0.09 to 0.16 mg/kg in sediments, 0.06 to 0.13 mg/kg in fish and 0.02 to 0.11 mg/kg in prawn. The sources of contamination of PAHs in Bonny River were of both petrogenic and pyrolytic origin, however, a strong pyrolytic source fingerprint was observed to be dominant at almost all the stations investigated. BSAF values of total PAHs in fish was higher than prawn indicating higher accumulation in fish. Assuming prawn as the main prey of the fish (Mugil cephalus), bioaccumulation factor of PAHs in fish ranged from 0 to 1.36, suggesting tissue bioaccumulation. Estimated daily intake (EDI) of PAHs through consumption of fish and prawn were observed to be lower than the reference dose (RfD) indicating low risk from consumption. Results of the estimated excess cancer risk (ECR) for Benzo (a) anthracene in fish, however, suggests that lifetime exposure to Benzo(a)anthracene through fish consumption could result in cancer risk which calls for public health and safety concerns.