Deeper NOx emission reductions toward better air quality in the Yangtze River Delta: Numerical evidences from NOx and VOCs emissions control measures

Mitigating air pollution in the Yangtze River Delta (YRD), one of China's most densely populated regions, is critical for reducing pollution-related health impacts. This study uses the WRF-Chem model to simulate the concentrations of two key pollutants, PM_2.5 and O₃, and to assess their responses to various emission control measures. Our objective is to provide actionable insights for designing effective clean air policies to improve future air quality in the YRD. The sensitivity analysis using the Comprehensive Air Quality Index (CAQI) underscores the complex interactions between PM_2.5, O₃, and reductions in NOx and VOC emissions. Notably, NOx reductions exhibit the greatest potential for lowering CAQI in summer, but in winter, the positive effects on PM_2.5 reduction may be offset by higher O₃ levels. Despite this trade-off, deep NOx emission cuts remain the most effective strategy for controlling both PM_2.5 and O₃ pollution in the YRD. These findings provide critical numerical insights and serve as a strong foundation for policymakers to develop targeted air quality management strategies.