Nonlinear relationship between air pollution and precursor emissions in Qingdao, eastern China

Highlights

	● The production of PM2.5 in January and O3 in June was a VOC-limited regime.
	● Compared to other sources, industry VOC control benefits more PM2.5 and O3 levels.
	● Both levels have the strongest response to NO x cuts from transportation and industry.
	● Further control of combined pollution depends on the deep reduction of NO x .

Abstract

Exploring the nonlinear relationship between air pollution and precursor emissions in Qingdao, eastern China is crucial for improving air quality. We simulated 32 emission reduction scenarios based on different volatile organic compound (VOC) and nitrogen oxide (NO_x) emission reduction ratios using the Weather Research and Forecasting-Comprehensive Air Quality Model Extensions model. The emission reduction of VOCs was beneficial for reducing fine particulate matter (PM_2.5) concentration in January and ozone (O₃) concentration in June. However, NO_x must be reduced by at least 48% and 70% to decrease PM_2.5 and O₃ concentrations, respectively, when VOCs are not reduced. The responses of PM_2.5 and O₃ concentrations to emission reductions from different sources were also evaluated. The reduction in VOC emissions from different sources decreased the PM_2.5 concentration in January, and O₃ concertation in June, while NO_x reduction resulted in an increase. Controlling VOC emissions from industry has a positive effect on improving local PM_2.5 and O₃, while the emission reductions of NO_x from transportation and industry are not conducive to reducing PM_2.5 and O₃ concentrations. The synergistic emission reduction pathways for NO_x and VOCs during PM_2.5 and O₃ combined pollution were also analyzed. The VOC and NO_x emission reductions were beneficial for reducing the comprehensive Air Quality Index (sAQI) values. When the NO_x emission reduction was large, the sAQI improvement gradually exceeded that of VOCs. A collaborative optimization path should be adopted that focuses on controlling VOCs first, and further control of combined pollution should depend on the deep reduction of NO_x.

Graphical abstract

Keywords

PM_2.5 / O₃ / Emission reduction / Nonlinear relationship / WRF-CAMx

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Acknowledgements

This work was funded by the Shandong Postdoctoral Science Foundation (No. SDCX-ZG-202303008).

Conflict of Interests

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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