Abstract: Taking a petrochemical project of Nangang industrial area situated in the southern Binhai New Area, Tianjin as a case, the characteristics of dispersion and transport of air pollutant NO_x were simulated by using a boundary layer model, and its environmental impact was analyzed with consideration of its atmospheric stability and mixed layer thickness. The results showed that there were no apparent differences in the NO_x concentration at the 150 m height diffusion center among four seasons, whereas at the height of 10 m above ground the NO_x concentration had large differences in different seasons. NO_x concentration was highest in winter (0.03 μg·m^-3), followed by summer (0.024 μg·m^-3), but NO_x concentrations in spring and autumn were only 25%-50% of that in winter and summer. The dispersion direction of NO_x was consistent with the dominant wind direction in this area. In winter, NO_x dispersed to southeast due to the dominant northwest wind and thus the influence of pollutants on inland areas was least because NO_x mainly dispersed to the sea. Southwest wind prevailed in spring and autumn, leading to the dispersion of NO_x to the northeast to weakly affect the Tanggu coastal region. Different from other seasons, southeast wind prevailed in summer and NO_x dispersed to the northwest, making a certain impact on the inland. However, the concentration of NO_x after approximately 30 km diffusion to the northwest was only 0.002 μg·m^-3, which met the air quality standard for NO_x. Considering the high sensitivities of petrochemical production, storage and transport to high temperature and the characteristics of air pollutant dispersion, it is recommended to reduce the production scale and increase pollution control efforts in summer in order to decrease the risk of high temperature and the impact on the inland.

Key words: nitrogen level, intercropping, wheat powdery mildew, nitrogen accumulation and allocation