@article {SHAO2021147712,
	title = {Quantifying the role of PM2.5 dropping in variations of ground-level ozone: Inter-comparison between Beijing and Los Angeles},
	journal = {Science of The Total Environment},
	volume = {788},
	year = {2021},
	pages = {147712},
	abstract = {In recent decade the ambient fine particle (PM2.5) levels have shown a trend of distinct dropping in China, while ground-level ozone concentrations have been increasing in Beijing and many other Chinese mega-cities. The variation pattern in Los Angeles was markedly different, with PM2.5 and ozone decreasing together over past decades. In this study, we utilize observation-based methods to establish the parametric relationship between PM2.5 concentration and key aerosol physical properties (including aerosol optical depth and aerosol surface concentration), and an observation-based 1-D photochemical model to quantify the response of PM2.5 decline in enhancing ground-level ozone pollution over a large PM2.5 concentration range (10{\textendash}120 μg m-3). We find that the significance of ozone enhancement due to PM2.5 dropping depends on both the PM2.5 levels and optical properties of particles. Ozone formation increased by 37\% in 2006{\textendash}2016 due to PM2.5 dropping in Beijing, while it becomes less important (7\%) as PM2.5 reaches below 40 μg/m3, similar to Los Angeles since 1980s. Therefore, the two cities show the convergence of air pollutant characteristics. Hence a control strategy prioritizing reactive volatile organic compound abatement is projected to yield simultaneous ozone and PM2.5 reductions in Beijing, as experienced in Los Angeles.},
	keywords = {ozone, PM, Pollution control, Volatile organic compounds},
	issn = {0048-9697},
	doi = {https://doi.org/10.1016/j.scitotenv.2021.147712},
	url = {https://www.sciencedirect.com/science/article/pii/S0048969721027832},
	author = {Min Shao and Wenjie Wang and Yuan, Bin and Parrish, David D. and Xin Li and Lu, Keding and Luolin Wu and Xuemei Wang and Ziwei Mo and Suxia Yang and Yuwen Peng and Ye Kuang and Chen, Weihua and Min Hu and Limin Zeng and Su, Hang and Yafang Cheng and Junyu Zheng and Yuanhang Zhang}
}
