Peer Review #1 of "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 (v0.1)"

Abstract

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℃), low relative humidity (RH<60%), and low wind speed (WS<3m/s) were favorable for O 3 formation and accumulation, and the O 3 pollution days (MDA8 O 3 >160µg/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 3concentration. 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.