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

Abstract

Abstract. The implementation of strict emission control during the 11th National Minority Games (NMG) in September 2019 provided a valuable opportunity to assess the impact of such emission controls on the characteristics of VOCs and other air pollutants. Here, we investigated the characteristics of VOCs and the O3–NOx–VOC sensitivity comprehensively in Zhengzhou before, during, and after the NMG by delivering field measurements combined with WRF-CMAQ (Weather Research and Forecasting Community Multiscale Air Quality) model simulations. The average mixing ratios of VOCs during the control periods were 121 ± 55 µg m−3 and decreased by about 19 % and 11 % before and after emission reduction. The ozone precursors (NOx) also decreased significantly during the control period; however, the ozone pollution 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 petroleum gas (LPG). The results show that the major source emissions, such as coal combustion and solvent utilization, were significantly reduced during the control period. As for ozone formation potential (OFP), the value during the control period was 183 ± 115 µg m−3, which was 0.23 and 0.17 times lower than before and after the control period, respectively. Solvent utilization and combustion controls were the most important measures taken to reduce OFP during the NMG period. Control policies can effectively reduce carcinogenic risk. However, non-cancer risks of ambient VOC exposures were all exceeding the safe level (hazard quotient = 1) during the sampling periods, and emphasis on the reduction of acrolein emissions was needed. In addition, the WRF-CMAQ model simulation indicated that O3 formation was controlled by VOCs in Zhengzhou. The results of the Empirical Kinetic Modeling Approach showed that the NOx reduction in Zhengzhou might lead to higher ozone pollution. It is suggested that reduction ratios of the precursors (VOCs : NOx) should be more than 2, which can effectively alleviate ozone pollution.

Chemical Characteristics and Source-Specific Health Risks of the Volatile Organic Compounds in Urban Nanjing, China

“…LCR values of 1,2-dibromoethane, naphthalene, and 1,1,2-Trichloroethane for a few samples were above the threshold. As shown in Table S2, compared with previous results in other cities such as Langfang [97], Beijing [98], and Zhengzhou [57], the average NCR of VOCs (sum of all calculated NCR divided by the number of calculated VOCs) in this study (2.69 × 10 −5 ) was a little higher than those in Langfang (2.54 × 10 −5 ) and Beijing(1.58 × 10 −5 ), but lower than that in Zhengzhou (5.28 × 10 −5 ), while the average LCR value (2.49) was lower than those determined in these cities, except in Langfang (5.17). In particular, acrolein was found to The relative contributions of different sources in the morning and afternoon samples are shown in Figure 8b,c.…”

“…Both LCR and NCR values were calculated for the measured VOCs. The recommended safety thresholds of LCR and NCR are 1 × 10 −6 and 1 for adults, respectively [57]. As shown in Figure 9, based on the campaign average concentrations, only one compound (acrolein, 2.36), exceeded the NCR threshold, and only two compounds (benzene and 1,2-dichloroethane, 2.07 × 10 −6 and 13.15 × 10 −6 ) exceeded the LCR threshold.…”

“…We performed a quantitative health risk assessment on the VOCs by using the method recommended by the US EPA and the Exposure Factor Handbook of Chinese Population (US EPA, 1989; Ministry of Ecology and Environment of China, 2013), which have been widely used previously [57][58][59]. There are two health risk indicators: Lifetime carcinogenic risk (LCR) and noncarcinogenic risk (NCR).…”

“…The following supporting information can be downloaded at: https://www. mdpi.com/article/10.3390/toxics10120722/s1, Figure S1 S1: The available parameters for NCR and LCR assessment of VOCs and the results of this work, with selected results from other cities in China [57,97,98]; Table S2: Selected studies of VOCs measurements in the five economically developed regions in China [13][14][15][16]41,54,73,88,93,[100][101][102][103][104].…”

Research progresses on VOCs emission investigationsviasurface and satellite observations in China

“…a 22, 81 and 82.b 17, 28, 68, 72, 76 and 83–89.c 7.d 2, 4, 14, 16, 18, 19, 21, 29–31, 35, 48, 49, 58, 70, 73, 75 and 90–109.e 71 and 109–111.f 1, 14, 15, 22, 30, 31, 35, 37, 65, 93, 95, 107, 112–115 and 115–118.g 35.h 17, 37, 74, 116 and 119–121.i 122 and 123.j 13, 20, 23, 32–34, 51, 57, 94, 123–127, 127–129 and 129–134.k 123.l 26 and 135–137.m 23, 25, 26, 119…”