By analyzing the migration of PAHs with different rings in the soil (Table 2 and Fig.1) , we found that the
ratio of low molecular weight PAHs (2-3 rings) to total PAHs in surface soils was small, but increased
rapidly with the increase of soil depth. The concentration of Σ2 rings PAHs in soil profile depth changed
with the peak at 60-70 cm, The concentration of Σ3 rings PAHs in soil profile depth changed with the
peak at 40-50 cm, and low rings PAHs higher migration ability; and Σ4 rings PAHs got the peak at 30-40
cm depth, Σ5 rings PAHs got the peak at 30-40 cm depth, then gradually reduced; and 6 rings PAHs with
peak at 0-10 cm depth.. Factors affecting the vertical migration of PAHs include the physical and
chemical properties of PAHs, content of organic carbon and clay in soil, leaching and human disturbance,
etc. 2-3 rings PAHs with the lg KOW