Abstract:

Identifying the key influencing factors for different types of ozone (O₃) pollution days is of great significance for the effective implementation of O₃ pollution control measures. To elucidate the discrepancies in key precursors and meteorological factors influencing days with different types of O₃ pollution, this study analyzed the pollution characteristics of different types of O₃ pollution days in key regions from 2017 to 2022. Bozhou City, located at the intersection of Jiangsu, Anhui, Shandong, and Henan provinces, was selected as a typical subject to analyze the variation characteristics and differences in precursors and meteorological factors under different types of O₃ pollution days. Additionally, correlation analysis, backward trajectory, and random forest methods were utilized to assess the meteorological conditions of O₃ pollution, origins of air masses, and magnitude of influence of precursors and meteorological factors. The results showed the following: 1) The increase in precursor concentrations was positively correlated with the proportion of days with high O₃ exceedances (both the hourly O₃ mass concentrations and daily maximum 8-hour average O₃ mass concentrations exceeded the standards) and low O₃ exceedances (the hourly O₃ mass concentrations exceeded the standard, and the daily maximum 8-hour average O₃ mass concentrations did not exceed the standard). When the daily NO₂ concentration was between 30 and 40 μg·m⁻³, the proportion of days with high O₃ exceedance reached 71.4%. When the daily average concentration of CO was less than 0.4 mg·m⁻³, the proportion of days with low O₃ exceedances was 83.3%. 2) The status of O₃ pollution is closely related to meteorological conditions. When the daily average temperature was below 35 ℃, the increase in temperature was conducive to an increase in the O₃ concentration, and the frequency of high-value exceedance days tended to increase. When the relative humidity was in the range of 50%-60%, the occurrence of high O₃ exceedance days was more favorable. When the relative humidity was in the range of 60%-70%, the occurrence of low O₃ exceedance days was more favorable. 3) Days with high O₃ exceedances were significantly influenced by air masses from the northwest and southeast, whereas days with low O₃ exceedances were more affected by air masses from the south and northeast. 4) Random forest results showed that for high O₃ exceedance days, the relative humidity (40.9%) and temperature (26.4%) had significant effects. For days with low O₃ exceedances, the relative humidity (30.4%) and NO₂ (26%) had significant effects.

Key words: O₃ high and low value exceedance, precursors, meteorological factors, backward trajectory, random forest, Bozhou City

摘要： 为了解不同类型O₃污染日关键O₃前体物和气象因素差异及其影响，在研究2017－2022年中国重点区域不同类型O₃污染日O₃污染特征的基础上，以苏皖鲁豫交界地区典型城市亳州市为例，分析了不同类型O₃污染日下O₃前体物和气象因素变化特征及差异；同时，通过相关性分析、后向轨迹、随机森林等方法研究了O₃污染气象条件、气团来源，及前体物与气象因素影响大小。结果表明，1）O₃高值超标（O₃质量浓度小时值和日最大8 h均值均超标）和O₃低值超标（O₃质量浓度小时值不超标，但日最大8 h均值超标）天数的占比与其前体物质量浓度的高低整体呈现一致的变化关系；NO₂质量浓度日均值在30－40 μg·m⁻³区间时，O₃高值超标日占比高达71.4%；CO质量浓度日均值<0.4 mg·m⁻³时，O₃低值超标日占比为83.3%。2）O₃污染状态与气象条件较为密切。当日均气温在35 ℃以下时，气温的升高有利于O₃质量浓度的升高且高值超标天数出现频率占比呈增加趋势；当相对湿度在50%－60%区间时，更有利于O₃高值超标天的出现；当相对湿度在60%－70%区间时，更有利于O₃低值超标天的出现。3）O₃高值超标日受西北和东南气团影响较大，低值超标日受南部和东北方向气团影响较大。4）随机森林分析结果表明，O₃高值超标日相对湿度（40.9%）和气温（26.4%）影响较大；O₃低值超标日相对湿度（30.4%）和NO₂（26.0%）影响较大。

关键词: O₃高低值超标, 前体物, 气象因素, 后向轨迹, 随机森林, 亳州市