粤北山地城市近地面臭氧污染特征及气象影响因素分析--以韶关为例

Analysis of characteristics of surface ozone pollution and meteorological factors in a mountain city of northern Guangdong:A case study in Shaoguan

利用2015-2019年韶关市3个地面环境空气质量国控站逐时臭氧(O_(3))观测资料、同期的气象资料、ECMWF(欧洲中期天气预报中心)ERA5再分析资料和2017-2019年广东南岭背景空气自动监测站逐时臭氧(O_(3))观测资料,对粤北山地城市(以韶关为例)的近地面臭氧污染特征及气象影响因素进行了系统分析,包括韶关近地面O_(3)污染变化特征及其与气象因子的关系,以及O_(3)传输路径和潜在源区;特别针对多盆地地形的特点,分析了盆地效应对O_(3)浓度变化规律的影响.结果表明:①即使是在远离珠三角的粤北山地城市,2015-2019年近地面O_(3)污染超标持续时间逐年加长,韶关O_(3)MDA8(臭氧日最大8 h滑动平均浓度)第95分位数的增长趋势为3.965μg·m^(-3)·a^(-1);②O_(3)年变化特征呈单峰型分布,峰值出现在9月;日变化特征也呈单峰型分布,峰值出现在15:00-16:00;③韶关O_(3)传输通道一是来自广东省清远和珠三角(如广州、佛山、肇庆)地区,二是来自江西省赣州;④受盆地效应主导,盆地内的3种典型站点(城区站、工业区站、郊区站)O_(3)分布变化特征基本相似,背风坡“盆地效应”下沉气流易导致近地面O_(3)堆积.

Based on the hourly monitoring data of ozone(O_(3))concentrations and meteorological conditions at three environmental air quality monitoring stations in Shaoguan City from 2015 to 2019,the fifth-generation global atmospheric reanalysis data(ERA5)produced by ECMWF(European Centre for Medium-Range Weather Forecasts),and the hourly monitoring data of O_(3)concentrations at Nanling Background Air Automatic Monitoring Station in Shaoguan City from 2017—2019,the variation characteristics of surface O_(3)pollution and its relationship with meteorological factors in a mountain city of northern Guangdong(Shaoguan)were analyzed,including the characteristics of near-surface O_(3)pollution variations in Shaoguan and its correlation with meteorological factors,O_(3)transport channel and potential source areas,especially the“basin effects”on the variation of O_(3)concentration due to the special topographic structure in Shaoguan.The results indicated that:①Even far away from the Pearl River Delta,the duration of surface ozone pollution in Shaoguan City increased year by year during 2015—2019,and the 95th percentile of maximum daily 8-hour average O_(3)(MDA8)increased with a trend of 3.965μg·m^(-3)·a^(-1).②The annually variation characteristics of O_(3)showed a single peak distribution,and the peak value appeared in September.The daily variation characteristics also showed a single peak distribution,and the peak value appeared during 15:00—16:00.③The main transport channels of O_(3)pollution over Shaoguan City came from Guangdong Province(Qingyuan)and Pearl River Delta area(e.g.,Guangzhou,Foshan and Zhaoqing)and Jiangxi Province(Ganzhou).④The distribution characteristics of O_(3)in three typical stations(urban station,industrial station and suburban station)were similar due to“basin effects”.The cause of the O_(3)pollution in Shaoguan was that O_(3)could transfer through transport channel and then accumulate near the surface driven by the downdraft on leeward slope.