Study on the NO2 pollution and its connection with PM2.5 and O3 in Dazhou based on source apportionment

Abstract

Dazhou, as one of the key construction cities in the Sichuan-Chongqing economic belt, has experienced accelerated economic development, accompanied by a dense population, extensive infrastructure construction, and rapid industrial growth. Consequently, air pollution has become increasingly severe, with the mass concentration of NO₂, a primary pollutant, being a significant constraint on air quality management in the city. This study utilizes the WRF-CMAQ (Weather Research and Forecasting Model-Community Multi-scale Air Quality) model to quantitatively analyze the main sector sources of NO₂ in Dazhou during different seasons in 2022. The findings reveal that industrial sources contribute the most to NO₂ pollution in spring and winter, while transportation sources dominate in autumn. Additionally, the correlation between PM_2.5, O₃, and NO₂ concentrations, which exhibit significant seasonal variations, was examined. Notably, in summer, a negative correlation between O₃ and NO₂ concentrations was observed, while a positive correlation between PM_2.5 and NO₂ concentrations was evident in winter. Furthermore, the correlation between NO₂, O₃ and PM_2.5 concentrations across different sectors was analyzed using ISAM (The Integrated Source Apportionment Method). In spring, the energy sources of NO₂ and the transportation sources of O₃ are significantly negatively correlated, with a correlation coefficient of −0.94. Additionally, the residential sources of NO₂ are significantly positively correlated with the transportation sources of PM_2.5, with a correlation coefficient of 0.96. In autumn, the energy sources of NO₂ exhibit the most significant correlations with the industrial sources of O₃ and the transportation sources of NO₂ and PM_2.5. In winter, the correlations among various sectors for O₃ pollution are not significant, with correlation coefficients ranging from 0.02 to 0.63. The highest correlation is observed between the industrial sources of NO₂ and the residential sources of PM_2.5, reaching 0.98. This study analyzed the main source sectors of NO₂ in Dazhou City and the correlation with the source sectors of O₃ and PM_2.5 by using the CMAQ-ISAM source apportionment method, revealing the importance of seasonal cooperation in air pollution control in Dazhou and emphasizing its significance for long-term pollution management.