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. The implementation of strict emission control during the 11th National Minority Games (NMG) in September 2019 provided a valuable opportunity toassess the impact of such emission controls on the characteristics of VOCs and other air pollutants. Here, we investigated the characteristics ofVOCs and the O3–NOx–VOC sensitivity comprehensively in Zhengzhou before, during, and after the NMG by delivering fieldmeasurements combined with WRF-CMAQ (Weather Research and Forecasting Community Multiscale Air Quality) model simulations. The average mixingratios of VOCs during the control periods were 121 ± 55 µg m−3 and decreased by about 19 % and 11 % before and afteremission reduction. The ozone precursors (NOx) also decreased significantly during the control period; however, the ozonepollution was severe during the entire observation period. Positive matrix factorization analysis indicated seven major sources of ambient VOCs,including coal combustion, biomass burning, vehicle exhausts, industrial processes, biogenic emissions, solvent utilization, and liquefied petroleumgas (LPG). The results show that the major source emissions, such as coal combustion and solvent utilization, were significantly reduced during thecontrol period. As for ozone formation potential (OFP), the value during the control period was 183 ± 115 µg m−3, which was0.23 and 0.17 times lower than before and after the control period, respectively. Solvent utilization and combustion controls were the mostimportant measures taken to reduce OFP during the NMG period. Control policies can effectively reduce carcinogenic risk. However, non-cancerrisks of ambient VOC exposures were all exceeding the safe level (hazard quotient = 1) during the sampling periods, and emphasis on thereduction of acrolein emissions was needed. In addition, the WRF-CMAQ model simulation indicated that O3 formation was controlled by VOCsin Zhengzhou. The results of the Empirical Kinetic Modeling Approach showed that the NOx reduction in Zhengzhou might lead tohigher ozone pollution. It is suggested that reduction ratios of the precursors (VOCs : NOx) should be more than 2, which caneffectively alleviate ozone pollution.

atmospheric chemistry and physics

Characterization of ambient volatile organic compounds, source apportionment, and the ozone–NO&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;–VOC sensitivities in a heavily polluted megacity of central China: effect of sporting events and emission reductions