Abstract
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.
Highlights
China’s ozone (O3) concentrations have shown a gradual upward trend over recent years
Studies on China’s O3 pollution in China have focused on more developed regions, such as Beijing-Tianjin-Hebei (BTH) (Duan et al, 2008; Xu et al, 2011; Zhang et al, 2014b; Yan et al, 2016b), the Yangtze River Delta (YRD) (Wang et al, 2020b; Zhang et al, 2020b), the Pearl River Delta (PRD) (Chen et al, 2019; He et al, 2019), and the Guanzhong Plain (GZP) (Hui et al, 2021), which is close to the Loess Plateau
We focused on the relationship between meteorological parameters (T, relative humidity (RH), wind speed (WS), and WR) and O3 concentrations between May to August from 2017 to 2019 because O3 pollution days mainly occurred during this period
Summary
China’s ozone (O3) concentrations have shown a gradual upward trend over recent years. With stricter air pollution control and the increase of comprehensive studies on PM between 2014 and 2017 (Cao et al, 2008a; Cao et al, 2008b; Liu et al, 2004; Wang et al, 2011; Zhang et al, 2014a; Xiaoye, 2002), the PM2.5 pollution problem plaguing Loess Plateau, and many other parts of China (Cao et al, 2012; Zhang et al, 2019), has been effectively alleviated, while O3 concentrations continue to rise. O3 has become the primary pollutant affecting Loess Plateau’s ambient air quality in the summer
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