The Ozone Concentration and Changes in the Sensitivity of Its Formation in Guangdong-Hong Kong-Macao Greater Bay Area (GBA) from a Carbon Neutral Perspective

To investigate the potential impact of emission reduction measures on ozone (O3) formation under the carbon neutrality target, we examined the changes in O3 concentration and their sensitivity to various parameters in the urban and suburban areas of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). In this study, we used the Weather Research and Forecasting (WRF), the Sparse Matrix Operator Kernel Emissions (SMOKE) and the Community Multi-scale Air Quality Modeling system (CMAQ) air quality model to simulate O3 formation in three key years of 2020, 2030 and 2060, based on the Ambitious-pollution-Neutral-goal scenario data from the Dynamic Projection for Emissions in China (DPEC) model. The decoupled direct method (DDM) module embedded in CMAQ was used to calculate the first-order sensitivity coefficients of O3 to nitrogen oxides (SO3_NOx) and volatile organic compounds (SO3_VOC). The results show several important trends in the O3 concentrations and sensitivity. (1) For the changes in O3 concentrations, in terms of different seasons, the O3 concentration in the GBA region shows an increasing trend in winter in both 2030 and 2060 compared to 2020. In terms of different cities, the O3 concentration in Shenzhen shows a significant increasing trend compared to the other cities. (2) For changes in O3 sensitivity, SO3_NOx shows an increasing trend, with the negative area declining and the positive area increasing. In 2030, the negative absolute value of SO3_NOx is reduced, indicating that the NOx titration effect will be weakened. In 2060, SO3_NOx becomes positive in most areas of the GBA region. For SO3_VOC, the future scenario shows positive values throughout the study area for all years, but a decreasing trend.