Characteristics of ozone pollution and VOCs source analysis in the northern cities of Zhejiang, China

Abstract

As an important industrial area in the Yangtze River Delta region, the northern part of Zhejiang Province, including Hangzhou, Jiaxing and Huzhou, is experiencing severe ozone pollution from 2020 to 2022. By analyzing the observations measured at 23 stations in northern Zhejiang, the spatiotemporal features of the ozone pollution and the relationship between ozone and volatile organic compounds (VOCs) were discussed in this paper. The results revealed that, during the 3 years, the average ozone concentration in three cities increased from 153 to 173 μg m⁻³, and the average ozone-polluted days increased from 29 to 58 days. The relationship between temperature and ozone showed a suppression of temperature on ozone photochemistry when that is higher than 34 °C. The mean concentrations of VOCs were 32.10 ppb and the ozone formation potential were 174.52 μg m⁻³ in Northern Zhejiang in 2022. Among all the observed VOCs species, the concentrations of alkanes and OVOCs could accounted for 30.87.% and 30.35%, however, alkenes and aromatic hydrocarbons were the first two main contributors (24.41% and 36.33%, respectively) to the photochemical production of ozone in northern Zhejiang. The potential source areas of alkenes and aromatic hydrocarbons were complex in northern Zhejiang, the analysis of the Concentration Weighted Trajectory (WCWT) indicated the potential source areas almost exist in all directions. In addition, the surrounding areas with high WCWT value could not be ignored. The regional joint prevention and emission control strategy are required in the ozone pollution control in Northern Zhejiang.