Although the spatial distribution of heavier PAHs is similar to that of ∑16PAHs (Fig. 5), lighter PAHs (2- to 3-ring PAHs) have some special characteristics. Fig. 5a shows that many isolated areas have high concentrations of 2-ring PAHs. These areas were more widely distributed than those with heavier PAHs and their concentrations were lower. This distribution of 2-ring PAHs is because the melting and boiling points of Nap are the lowest among the 16 PAH congeners, which easily leads to (S)-Crizotinib from the soil environment, and the lighter weight PAHs are also vulnerable to long-range atmospheric migration. In addition, more than half of the mutualism total PAHs from coal combustion and vehicle sources in urban soils generate heavier PAHs (above 3-ring PAHs). These characteristics can account for the lower concentrations of 2-ring PAHs and the low coincidence of spatial distributions between total PAHs and heavier PAHs (4–6 ring PAHs). The most isolated area was located in the northeastern suburban area. Compared with urban and rural soils, the greater contribution of oil sources from the nearby petrochemical enterprise may affect its spatial distribution.