Implications of Mitigating Ozone and Fine Particulate Matter Pollution in the Guangdong-Hong Kong-Macau Greater Bay Area of China Using a Regional-To-Local Coupling Model.

Ultrahigh-resolution air quality models that resolve sharp gradients of pollutant concentrations benefit the assessment of human health impacts. Mitigating fine particulate matter (PM) concentrations over the past decade has triggered ozone (O) deterioration in China. Effective control of both pollutants remains poorly understood from an ultrahigh-resolution perspective. We propose a regional-to-local model suitable for quantitatively mitigating pollution pathways at various resolutions. Sensitivity scenarios for controlling nitrogen oxide (NO) and volatile organic compound (VOC) emissions are explored, focusing on traffic and industrial sectors. The results show that concurrent controls on both sectors lead to reductions of 17%, 5%, and 47% in NO, PM, and VOC emissions, respectively. The reduced traffic scenario leads to reduced NO and PM but increased O concentrations in urban areas. Guangzhou is located in a VOC-limited O formation regime, and traffic is a key factor in controlling NO and O. The reduced industrial VOC scenario leads to reduced O concentrations throughout the mitigation domain. The maximum decrease in median hourly NO is >11 μg/m³, and the maximum increase in the median daily maximum 8-hr rolling O is >10 μg/m³ for the reduced traffic scenario. When controls on both sectors are applied, the O increase reduces to <7 μg/m³. The daily averaged PM decreases by <2 μg/m³ for the reduced traffic scenario and varies little for the reduced industrial VOC scenario. An O episode analysis of the dual-control scenario leads to O decreases of up to 15 μg/m³ (8-hr metric) and 25 μg/m³ (1-hr metric) in rural areas.