2019—2022年运城市暖季夜间臭氧增强事件污染特征及驱动因素分析  

Characteristics and drivers of nocturnal ozone enhancement events in the warmseason in the city of Yuncheng during 2019—2022

作　　者：史治辉 张强 罗淑贞 罗嘉昕 赵兴赟 樊亭亭 郑烈龙 姜旭朋 SHI Zhihui;ZHANG Qiang;LUO Shuzhen;LUO Jiaxin;ZHAO Xingyun;FAN Tingting;ZHENG Lielong;JIANG Xupeng(College of Urban and Environmental Sciences,Northwest University,Xi’an 710127)

机构地区：[1]西北大学,城市与环境学院,西安710127

出　　处：《环境科学学报》2025年第2期291-305,共15页Acta Scientiae Circumstantiae

基　　金：国家重点研发计划(No.2019YFC0214203);国家自然科学基金青年科学基金(No.41807342);大气重污染成因与治理攻关项目(No.DQGG-05-32,DQGG202110)。

摘　　要：近年来,运城市频繁出现夜间臭氧增强(Nocturnal ozone enhancement,NOE)事件.本研究基于2019—2022年暖季(4—9月)运城市国控站点大气污染物数据结合同期气象资料,分析运城市夜间O_(3)污染特征,并探讨夜间臭氧增强事件的潜在驱动因素.结果表明:①运城市在2019—2022年暖季期间共观测到185次NOE事件,年际变化呈逐年下降趋势,其中,6月出现NOE事件的频率和O_(3)浓度均最高,且大多数NOE事件发生在0:00—2:00之间;夜间O_(3)峰值(Nighttime ozone peak,NTOP)平均浓度为117μg∙m^(-3),且86%的NTOP达到日间峰值水平的1/2以上;与周围城市相比,运城市夜间的O_(3)-8 h浓度在高百分位污染更重.②山谷风日下夜间逐小时O_(3)浓度均大于非山谷风日,且在20:00以及01:00后山谷风日的O_(3)浓度与非山谷风日的差异逐渐增大,均大于10μg∙m^(-3);同时,在午夜随着山谷风环流强度的增加,NOE事件发生的频率也随之增加.③在典型NOE事件观测期间,当温度主要分布在(30±3)℃,相对湿度为40%±5%且风向为西南风或东南风时夜间O_(3)浓度容易出现超标现象;此外,当风速和大气边界层高度较低时会抑制O_(3)在垂直方向上的扩散,从而进一步加剧NOE事件的发生.④后向轨迹聚类分析表明,经过主城区东南部和南部的短距离气团区域传输占比较大,是运城市出现夜间O_(3)高值的原因之一;利用潜在源贡献因子法(PSCF)和浓度权重轨迹法(CWT)分析进一步得出夜间O_(3)浓度潜在源区分布在河南省西部、陕西省南部及湖北省北部等地.In recent years,nocturnal ozone enhancement(NOE)events have occurred frequently in Yuncheng City.This study analyzed the characteristics of nighttime ozone pollution in Yuncheng City and explored the potential driving factors of NOE using air pollutant and meteorological data from the Yuncheng National Control Station during the warm seasons(April-September)of 2019—2022.The results showed that:①During the warm season from 2019 to 2022,a total of 185 occurrences of NOE were recorded in Yuncheng City,showing a decreasing trend in interannual variation.The highest frequency of NOE events and O_(3)concentration was observed in June,with most NOE events occurring between 0:00 and 2:00.The nighttime O_(3)peak(NTOP)concentration averaged 117μg∙m^(-3),with 86%of NTOP exceeding half of the daytime peak levels.Compared to surrounding cities,Yuncheng City experienced higher nighttime O_(3)-8 h concentrations at the high percentile.②Nighttime hourly O_(3)concentrations are significantly higher on valley wind days compared to non-valley wind days.This disparity in O_(3)levels becomes more pronounced after 20:00 and post-01:00,with both exceeding 10μg∙m^(-3).Concurrently,the incidence of NOE escalates in correlation with the intensity of the valley wind circulation during the night.③During typical NOE event observation,the O_(3)concentration at night is likely to exceed the standard when the temperature is mainly distributed at(30±3)℃,the relative humidity is 40%±5%and the wind direction is southwest or southeast.Furthermore,diminished wind speeds and reduced atmospheric boundary layer heights impede vertical O_(3)diffusion,exacerbating the likelihood of NOE.④The cluster analysis of backward trajectories shows that regional transport of short-range air masses,which traverse the southeastern and southern sectors of the primary urban area,significantly contributes to elevated nocturnal O_(3)levels in Yuncheng City.Subsequent potential source contribution function(PSCF)and concentrationweighted trajectory(CWT)

关 键 词：夜间臭氧增强 山谷风 气象因素 聚类分析 运城 

分 类 号：X51[环境科学与工程—环境工程] X16