Distribution, sources and factors influencing the dissipation of polycyclic Aromatic hydrocarbons in urban soils

The sources and the distributions of 23 polycyclic aromatic hydrocarbons (PAHs) in surface (0–5 cm depth) and subsurface (5–10 cm depth) soil in Riyadh, Saudi Arabia, were studied. Isomeric diagnostic ratios of the PAHs (the (anthracene/(anthracene + phenanthrene)), (benz(a)anthracene/(benz(a)anthracene + chrysene)), (fluoranthene/(fluoranthene + pyrene)), (indeno(1,2,3-cd)pyrene/(indeno(1,2,3-cd)pyrene + benzo(g,h,i)perylene)), and (benzo(a)pyrene/benzo(g,h,i)perylene) concentration ratios) were used to determine which anthropogenic sources of PAHs were dominant in different areas. The study area included four areas characterized by different anthropogenic activities; an urban area, an area strongly affected by traffic, a bare area, and an industrial area. The PAHs in all four area types were mainly emitted from factories and other mixed sources. The PAHs concentrations and patterns in some areas reflected the roles of anthropogenic activities in causing environmental pollution, especially the role of infrastructure projects (through emissions during the building work itself and emissions from heavy machinery and transport to and from the site). In contrast, PAHs concentrations and patterns in southern Riyadh showed that the recent improvements in the road network, which has improved traffic flow, have led to decreases in PAHs contamination caused by fuel combustion.