Evolution of surface ozone pollution in Yangtze Rriver Delta between 2019 and 2022: influences of meteorology and emissions

Abstract

The Yangtze River Delta (YRD) suffers severe surface ozone (O₃) pollution during summer (June-July-August, JJA). Elucidating the role of meteorology and emissions is crucial for effective controls on O₃ pollution. We used the Weather Research and Forecasting (WRF) - Community Multiscale Air Quality (CMAQ) modeling system to quantify the influences of meteorology, anthropogenic and biogenic emissions on O₃ variations in the YRD between 2019 and 2022. Contrasting trends in surface O₃ were found in the Hangzhou Bay (HZB) (3.3 μg m⁻³ yr⁻¹) and the rest of the YRD (−1.9 μg m⁻³ yr⁻¹). Underlying factors affecting surface O₃ differed between these two subregions. In HZB, meteorological variations dominated the strong O₃ increase with a contribution of ∼94 %. By contrast, in the rest of the YRD, meteorology (42 %) and anthropogenic emissions (53 %) were both key contributors to the modest O₃ decrease. Our results reveal a shift in O₃ drivers in contrast to 2013–2019, characterized by an increasing importance of meteorology and a decreasing contribution of anthropogenic emissions. Consequently, the anthropogenically driven O₃ decrease, which ensues from current pollutant control policies, is difficult to offset the strong positive meteorological influence such as in HZB. There is an urgent need for stricter and more efficient control of O₃ precursor emissions to mitigate the substantial influences of meteorology. Emissions of non-methane volatile organic compounds are of particular concern, as they are still on the rise.