The concentration of PAHs at different depth of the profile showed in Table 1; Vertical distribution of
different rings PAHs showed on Fig.1; Vertical distribution of total PAHs showed on Fig.2. Due
to 6 rings PAHs are impermeable and insusceptible to oxidation damage, the concentration of 6 rings
PAHS were highest at the depth of 0-10 cm, and high rings PAHs were more easily accumulated in the
soil surface. However, the concentration of PAHs at the top surface was attenuation because of the
photolysis and other acts of migration and transformation (Fig.1). Further down observed that the
concentrations of PAHs were varying at different depths in profile: gradually increased from top to the
depth of 30-40 cm, where the peak appeared, and then gradually decreased (Fig.2). That’s may be soil in
this area were dominated by alluvial sandy soil which can play a role of adsorption and enrichment to
PAHs. On the other hand, this adsorption and enrichment can retard and retain PAHs downward
migration, made them migrate slowly and penetrate down difficultly. However, after many years of
long-term pollution there was still a certain amount of PAHs into the soil of 90-100 cm depth because of
factors like rainwater leaching and combination with soil clay.