The effects of total organic carbon content (TOC) on the migration of polycyclic aromatic hydrocarbons (PAHs) in the soil were investigated. This study analyzed the vertical properties of the concentrations and distributions of PAHs and TOC at various soil profiles from functionally different environmental regions including nature reserves, ploughs, orchards, farmlands, metropolitan areas, and industrial parks. The vertical migration properties of PAHs in soils were examined by conducting leaching experiments in soil columns. The concentrations of PAHs varied from region to region and showed strong, positive correlations with TOC in the same region. Furthermore, based on the leaching experiments, the transport abilities of PAHs were significantly influenced by TOC, although they could all be transported to the deep layers by TOC in soil columns. The downward migration of PAHs decreased with the increase in TOC and vice versa. The properties of the composition and structure of PAHs also had an obvious influence on their residues and migration in soil profiles at the same TOC conditions. In addition, the transport of PAHs was related to the amount of leaching water, the leaching time, and the additional PAHs.
Keywords: Beijing area; PAHs; TOC; leaching; migration; soil column.