江西省极端干旱下臭氧污染特征及成因分析

Characteristics and Mechanisms of the Ozone Pollution Episode During the Extreme Drought in Jiangxi Province

基于气象和环境空气质量监测数据,分析了江西省干旱对臭氧污染的影响,并结合VOCs在线监测数据,对2022年9月极端干旱下江西省臭氧污染过程特征及污染成因进行分析。结果表明:江西省臭氧污染与气象干旱间存在一定联系,干旱情况下缺少降水对臭氧及其前体物VOCs的湿清除作用,易促使臭氧超标概率随着无雨日数的增加逐步上升。江西省2022年9月出现历史性极端干旱情况,干旱期间江西省11个地市共出现151 d臭氧超标天,NO2常于午夜和早晨出现浓度峰值,从而促进上午臭氧浓度的迅速上升。此外,南昌市林科所站点VOCs在线监测数据也显示:极端干旱期间逐日VOCs体积分数为11.9×10^(-9)~35.5×10^(-9),较8月明显升高。对OFP贡献前十的物种主要为OVOCs和芳香烃,与8月相比,芳香烃、烯烃和烷烃的OFP略有下降,OVOCs的OFP升高明显,其中乙醛对臭氧的贡献甚至上升143%,前期长时间的无降水可能是乙醛等OVOCs浓度上升的重要原因之一。

Based on meteorological and ambient air quality monitoring data,this paper examines the impacts of drought on ozone pollution in Jiangxi Province were analyzed in this paper,and combined with online monitoring data of volatile organic compounds(VOCs)from urban atmospheric supersites,the process characteristics and pollution causes of ozone pollution in Jiangxi Province under the extreme drought in September 2022 were emphatically analyzed.The results showed that there was a certain relationship between ozone pollution and meteorological drought in Jiangxi Province.In arid conditions,the absence of wet removal effect of precipitation on ozone and its precursor VOCs,which could easily result in a gradual increase in the probability of exceeding ozone standards as the number of rainless days increases.During the historical extreme drought in Jiangxi on September 2022,a total of 151 days of ozone exceeded the standard in 11 cities of Jiangxi Province.The peak concentration of NO2 was observed during midnight and early morning,contributing to the sharp rise in ozone concentration during the morning.In addition,the online monitoring data of VOCs at the Nanchang Institute of Forestry also showed that the daily VOCs volume fraction during the extreme drought was 11.9×10^(-9)-35.5×10^(-9),significantly higher than the previous August.The top 10 species contributing to OFP were mainly OVOCs and aromatic hydrocarbons.Compared with August,the ozone generation potential of aromatic hydrocarbons,alkenes,and alkanes slightly decreased,while the generation potential of OVOCs increased significantly.In which the contribution of acetaldehyde to ozone even increased by 143%.The long period of no precipitation in the early stage may be one of the important reasons for the increase of OVOCs concentration such as acetaldehyde.