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

In this study, ambient ozone (O(3)) 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. O(3) 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 O(3) formation and accumulation, and the O(3) pollution days (MDA8 O(3) > 160 µg/m(3)) were predominantly observed when the wind was traveling from the easterly and southerly. O(3) 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 O(3) pollution. In order to clarify the formation mechanism and source of O(3), 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 NO(x) may increase O(3) concentration. When the emission reduction ratio of anthropogenic VOCs/NO(x) higher than 1:1, the O(3) will decrease. O(3) control strategies analysis shows that the O(3) targets of 5% and 10% O(3) concentration reductions are achievable through precursor control, but more effort is needed to reach the 30% and 40% reduction control targets.