VOC characteristics, chemical reactivity and sources in urban Wuhan, central China

et al. 2021

Preprint

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-VOCs sensitivity comprehensively in Zhengzhou before, during, and after the NMG by delivering field measurements combined with the WRF (Weather Research and Forecasting)-CMAQ (Community Multi-scale Air Quality) model simulations. The average mixing ratios of VOCs during the control periods were 34 ppbv, and cut down by about 16% 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 μg/m3, which was 0.23 and 0.17 times lower than those before and after control period, respectively. Solvent utilization and combustion controls were the most important measures taken to reduce OFP during NMG period. Through control policies, it 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 Modelling Approach showed that the NOx reduction in Zhengzhou might led to higher ozone pollution. It is suggested that reduction ratios of the precursors (VOCs : NOx) is more than 2, which can effectively alleviate ozone pollution.

Section: Identification Of Pmf Factorsmentioning

confidence: 85%

“…The percentages of ethyl acetate, tetrachloroethylene, carbon tetrachloride, chloroform, dichloromethane were high. Those substances are important organic solvents, and typical tracers of solvent usage (Hui et al, 2018(Hui et al, , 2020. Meanwhile, there are virtually no other short chain hydrocarbon in this source.…”

Section: Identification Of Pmf Factorsmentioning

confidence: 99%

Characterization of ambient volatile organic compounds, source apportionment, and the ozone-NOx-VOC sensitivities in a heavily polluted megacity of central China: Effect of sporting events and the emission reductions

Shang

et al. 2021

Preprint

“…Source 2 accounts for larger percentages of carbon disulfide and halohydrocarbon, such as cis-1,2-dichloroethylene, chlorotrifluoromethane, trichloromethane, dichloromethane, 1,2-dichloroethane, and 1,2-dichloropropane, followed by some aromatics. Some previous studies indicated that these species were related to industrial processes (Hui et al, 2020;Zhang et al, 2018). Furthermore, ethylene, considered the blood of the industrial development (C. Song et al, 2019;Zheng et al, 2020), accounted for almost 65 % of the TVOCs in this factor.…”

Section: Identification Of Pmf Factorsmentioning

confidence: 86%

“…S. Yu et al: VOC characteristics during the control period verse impacts on human health, which induce cancer directly and are associated with increased long-term health risks (Hu et al, 2018;Jaars et al, 2018). Since the beginning of the 21st century, heavy air pollution events have frequently occurred in China, characterized by regional and complex air pollution (R. Ma et al, 2019).…”

mentioning

confidence: 99%

Characterization of ambient volatile organic compounds, source apportionment, and the ozone–NOx–VOC sensitivities in a heavily polluted megacity of central China: effect of sporting events and emission reductions

Shang

et al. 2021

Atmos. Chem. Phys.

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.

“…In this study, we measured 70 VOC species and divided these species into three categories according to their signal-to-noise ratio (S/N) and detection limit (BDL). In general, species were classified as strong if the S/N was >2, weak if the S/N was between 0.2 and 2 or if the BDL percentage was >50%, and bad if the S/N was <0.2 or if the BDL percentage was >60% ( Hui et al, 2020 ). Ultimately, 46 VOC species were selected and served as inputs of the PMF model.…”

Section: Methodsmentioning

confidence: 99%

Ambient ozone pollution at a coal chemical industry city in the border of Loess Plateau and Mu Us Desert: characteristics, sensitivity analysis and control strategies

Zhang

et al. 2021

PeerJ

In this study, ambient ozone (O3) pollution characteristics and sensitivity analysis were carried out in Yulin, a city in the central area of the Loess Plateau during 2017 to 2019 summer. O3 concentrations increased for 2017 to 2019. Correlation and statistics analysis indicated high temperature (T > 25 °C, low relative humidity (RH < 60%), and low wind speed (WS < 3 m/s) were favorable for O3 formation and accumulation, and the O3 pollution days (MDA8 O3 > 160 µg/m3) were predominantly observed when the wind was traveling from the easterly and southerly. O3 concentration in urban area of Yulin was higher than that in background. The pollution air masses from Fenwei Plain increase the level and duration of O3 pollution. In order to clarify the formation mechanism and source of O3, online measurements of volatile organic compounds (VOCs) were conducted from 7 July to 10 August in 2019. The average of VOCs concentration was 26 ± 12 ppbv, and large amounts of alkenes followed by aromatics, characteristic pollutants of the coal chemical industry, were detected in the ambient air. To further measure the sensitivity, the observation-based model (OBM) simulation was conducted. Empirical Kinetic Modeling Approach (EKMA) plot and relative incremental reactivity (RIR) value indicated Yulin located on VOCs-limited regime. That implied a slight decrease of NOx may increase O3 concentration. When the emission reduction ratio of anthropogenic VOCs/NOx higher than 1:1, the O3 will decrease. O3 control strategies analysis shows that the O3 targets of 5% and 10% O3 concentration reductions are achievable through precursor control, but more effort is needed to reach the 30% and 40% reduction control targets.