Abstract:Based on the data from meteorological and environmental monitoring stations, O3 meteorological condition evaluation index, O3 source apportionment products, GDAS and other data, combined with HYSPLIT model and other methods, the spatiotemporal variation characteristics of O3 pollution in Shaanxi Province from May to October (warm season) in 2019-2023 are analyzed. The impact of meteorological conditions on the changes of O3 concentration is quantitatively evaluated. At the same time, the contributions of local source, transport and different precursors to O3 pollution are quantitatively separated. Finally, the transport path of O3 pollution is explored. The results show that in the warm season of 2022, O3 pollution in Shaanxi was the heaviest, while in 2020 the pollution was the lightest. The O3 concentration showed a typical unimodal pattern in monthly and daily variations, with monthly peak occurring in June, daily peak appearing from 15:00 BT to 16:00 BT and daily minimum value at 07:00 BT. The O3 pollution in Guanzhong Region was the heaviest, mainly concentrated in the inner layer of the trumpet mouth terrain, whilst the O3 pollution was the lightest in southern Shaanxi. During the warm season of 2022, the O3 comprehensive meteorological conditions were the worst, which was the main reason for the heaviest O3 pollution in Shaanxi in 2022. So the O3 concentration in Shaanxi increased by 8.1% in 2022 compared to that in the previous year, and meteorological conditions contributed 7.7% to it. If the emission source remained unchanged, the O3 concentration in Shaanxi during the warm season of 2020 should have increased by 4.4% compared to that in 2019, but the observed O3 concentration decreased by 5.3%, which fully reflects the positive effects of regional air pollution control. The O3 comprehensive meteorological conditions in northern Shaanxi were the worst, but the O3 concentration in Guanzhong Region was the highest, which was mainly related to the high emissions of O3 precursors and regional transport in Guanzhong Region. In the warm season of 2023, the concentration of O3 in Shaanxi was mainly affected by precursor NOx, and the contribution of external transport was greater than local contribution. The main transport pathway was the southeast path, along which Henan and Hubei provinces had the greatest impact on the O3 transport in Shaanxi, contributing 6% and 4%, respectively.