Department of Geography & Spatial Information Techniques, Ningbo University, Ningbo, Zhejiang, 315211, China; Institute of East China Sea, Ningbo University, Ningbo, Zhejiang, 315211, China.
College of Meteorology and Oceanography, National University of Defense Technology, Changsha, Hunan, 410073, China.
Environ Pollut. 2023 Oct 15;335:122347. doi: 10.1016/j.envpol.2023.122347. Epub 2023 Aug 8.
The strict emission control measures have profoundly changed the air pollution in the Yangtze River Delta (YRD) region, China. However, the impacts of decreasing fine particulates (PM) and nitrogen oxide (NOx) on summer ozone (O) formation still remain disputable. We perform simulations in the 2018 summer over the YRD using the WRF-Chem model that considers the aerosol radiative forcing (ARF) and HO heterogeneous loss on aerosol surface. The model reasonably reproduces the measured spatiotemporal surface O and PM concentrations and aerosol compositions. Model sensitivity experiments show that the NOx mitigation during recent years changes daytime O formation in summer from the transition regime to the NOx-sensitive regime in the YRD. The decreasing NOx emission generally weakens O formation and lowers ambient O levels in summer during recent years, except for some urban centers of megacities. While, the haze alleviation characterized by a decline in ambient PM concentration in the past years largely counteracts the daytime O decrease caused by NOx mitigation, largely contributing to the persistently high levels of summertime O. The counteracting effect is dominantly attributed to the attenuated ARF and minorly contributed by the suppressed HO uptake and heterogeneous loss on aerosol surface. These results highlight that the repeated O pollution in the YRD is closely associated with NOx and haze alleviation and more efforts must be taken to achieve lower O levels.
严格的排放控制措施深刻改变了中国长三角（YRD）地区的空气污染。然而，减少细颗粒物（PM）和氮氧化物（NOx）对夏季臭氧（O）形成的影响仍存在争议。我们使用 WRF-Chem 模型在 2018 年夏季对 YRD 进行了模拟，该模型考虑了气溶胶辐射强迫（ARF）和 HO 在气溶胶表面的非均相损耗。该模型合理地再现了测量的时空表面 O 和 PM 浓度以及气溶胶组成。模型敏感性实验表明，近年来 NOx 的减排使 YRD 夏季的 O 形成从过渡态转变为 NOx 敏感态。近年来，NOx 排放的减少通常会减弱 O 的形成并降低夏季的环境 O 水平，但大城市的一些城市中心除外。然而，过去几年中以环境 PM 浓度下降为特征的雾霾缓解在很大程度上抵消了由 NOx 减排引起的白天 O 减少，这在很大程度上导致了夏季 O 水平的持续升高。这种抵消作用主要归因于减弱的 ARF，而次要归因于抑制的 HO 摄取和非均相损耗在气溶胶表面上的损耗。这些结果表明，YRD 地区的反复 O 污染与 NOx 和雾霾缓解密切相关，必须采取更多措施来实现更低的 O 水平。
