Impacts of Meteorological Factors, VOCs Emissions and Inter-Regional Transport on Summer Ozone Pollution in Yuncheng

Summer ozone (O3) pollution in China has become increasingly serious in recent years. This study is based on hourly data of near-surface ozone (O3) and nitrogen oxides (NOx) and volatile organic compounds (VOCs) from June to August 2020 in Yuncheng, combined with meteorological data to analyse the characteristics of O3 pollution in summer and the influence of meteorological factors, precursors, and long-range transport on O3 pollution. In this paper, the VOCs/NOx characteristic ratio method was used to explore the sensitivity of O3 generation. Backward trajectories, cluster analysis, potential source contribution factor (PSCF) analysis and concentration weight trajectory (CWT) analysis were also calculated using Trajstat software. In 2020, Yuncheng had persistent O3 pollution, with the highest concentrations in June, significantly higher than July and August. Conditions of high temperature, low relative humidity and low wind speed contribute to the O3 accumulation. VOCs are the main precursors to the local production of O3. Besides, the long-range transport analysis shows that southeast-oriented air masses are the main direction influencing summer O3 pollution. The primary potential source areas of O3 are in the central and southern part of Henan province, the north-western Anhui province, and the northern Shaanxi. In addition, northern Hubei and southwestern Shandong also influence O3 pollution in summer Yuncheng.