Abstract: A total of 95 soil samples from 18 profiles and five soil layers were collected from a large chemical engineering site in northeast China, with 16 priority polycyclic aromatic hydrocarbons (PAHs) being detected by GC/MS. The concentration, spatial distribution of PAHs in surface soils (0-3 m) and the vertical distribution across soil profile (0-16 m) were analyzed. The potential risks were assessed by the model of incremental lifetime cancer risk (ILCR). The results showed that ∑PAHs in the surface soils ranged from 0.13 to 553.5 mg·kg^-1, with an average of 67.0 mg·kg^-1. The ∑PAHs concentration was relatively high around the chemical company and the thermal power plant. 4ring PAHs were dominant in the depths of 0-3 m and 4-7 m, while lowring (2-ring and 3-ring) PAHs were dominant in the depths of 8-11 m. The ∑PAHs concentrations decreased with increasing soil depth in the undisturbed soil profiles, while relatively high concentrations of PAHs were found at a depth of more than 16 m in the disturbed soil profiles. According to the Soil Environmental Quality Risk Control Standard for Soil Contamination of Development Land in China, the concentration of BaP exceeded the value of soil environmental quality pollution risk control standards for class I construction land by 60.6 times. The results of health risk assessment showed that the ILCRs value was 9.6×10^-11-7.2×10^-5, being potential carcinogenic risk.

Key words: nitrogen absorption, cucumber, NO₃^--N/NH₄⁺-N ratio, nitrogen metabolism.