Distribution Ratios of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Soils

Distribution ratios and sources of polycyclic aromatic hydrocarbons (PAHs), including Fluoranthene (Flt), Pyrene (Pyr), Benzo(a)pyrene (BaP), Benzo(k)fluoranthene (BkP), Indeno(1,2,3-cd)pyrene (IP), Benzo(ghi)perylene (BgP) in urban surface and subsurface soil collected from Riyadh city, Saudi Arabia was studied. The sum of the six PAHs ranged from 30.5-1016.6 ng g-1 with an average of 286.6 in surface samples and from 25.5-1501.7 ng g-1 with an average of 287.9 ng g-1 in subsurface samples. The magnitude of the PAHs was found in the following order: Pyr > Flt > BgP > IP > BkF > BaP. The ratios of benzo(a)pyrene to benzo(ghi)perylene (BaP/BghiP) indicated that diesel and gasoline vehicular exhausts were the predominant local emission sources of PAHs. The maximum values of Ind/(Ind+BgP) and Flt/(Flt+Pyr) indicated predominantly that the sources of these PAHs are pyrogenic sources due to combustion. It was also observed that soil samples of industrial areas possess the highest PAHs concentrations, and that the PAHs concentrations decreased with increasing distance from Riyadh city.