Isolation and determination of polycyclic aromatic hydrocarbons in surface runoff and sediments

The distribution of Polycyclic Aromatic Hydrocarbons (PAHs) was investigated in surface runoff and sediments of Lagos, Osogbo and Ile-Ife Western areas of Nigeria. Method for the analysis of PAHs was based on Liquid-Liquid extraction of the runoff and a soxhlet extraction of the sediments followed by a clean up adsorption procedure. The PAHs were separated and quantified by Gas Chromatography-Mass spectrometry (GC-MS) technique. A blank experiment was done using triply distilled water and following the same procedure for the samples to establish blank levels. In both street runoff and sediments 13 PAHs were identified and quantified. At Osogbo and Ile-Ife areas, the mean levels of PAHs in surface runoff ranged between 0.10-15.81 mg L-1 while in the Lagos area the levels were between 0.1-73.72 mg L-1. Generally, the PAH levels in surface runoff of Lagos constitute 53.03 mg L-1 average Sigma PAH detected in the study area compared to 31.96 mg L-1 average Sigma PAH contribution made by samples from Osogbo and Ile-Ife. The levels of PAHs in sediments are relatively higher compared to those of the street runoff in the study area. PAHs in sediment of Lagos contribute an average of 228.57 mg kg(-1) Sigma PAH to the total sediment PAH burden compared to Osogbo and Ile-Ife areas that contribute only 91.13 mg kg(-1) average Sigma PAH to the total PAH burden of the study area. The relatively higher average Sigma PAHs reported for Lagos area compared with those of Osogbo and Ile-Ife, is consistent with higher industrial activities and traffic density of the former (1000-10000 vehicles/hr) than the later (450-1500 vehicles/hr).