苏州市近地面臭氧时空分布特征及模拟分析

Spatial-temporal Distribution Characteristics and Simulation Analysis of Subaerial Ozone in Suzhou City

文章利用2016-2019年苏州市臭氧(O_(3))环境监测站点数据,分析了苏州市O_(3)浓度的时空分布特征及其与NO_(2)、CO的相关性,并利用WRF-Chem模式模拟了苏州地区O_(3)高浓度事件来探究湖陆风对O_(3)迁移的影响。结果表明:苏州市O_(3)明显超标且2017年超标最为严重;O_(3)污染日具有明显的季节特征,以O_(3)作为首要污染物在春夏季尤为突出;月变化呈现双峰型特征,前2年峰值出现时间要略早于后2年;各季节日变化均为单峰型特征,在15:00前后浓度达到最高;空间上市区浓度整体高于周边城市,但在湖陆风盛行的2017年夏季截然相反;苏州市夏季存在明显的O_(3)“周末效应”,周末的夜间和上午O_(3)浓度高于工作日,而工作日在O_(3)峰值时段浓度更高;模拟的O_(3)高浓度事件证明了太湖湖陆风的存在,而高温时段湖风会将城区O_(3)往下风向的周边城市移动,造成苏州东北部城市O_(3)浓度要远高于城区;O_(3)浓度与NO_(2)、CO存在极显著相关性,而大气氧化剂OX(O_(3)+NO_(2))在白天由O_(3)控制,冬季夜间则完全由NO_(2)控制。

Based on the monitoring data of O_(3) over the years of 2016-2019 in Suzhou City,this paper analyzed the temporal and spatial distribution characteristics of O_(3) and its correlation with NO_(2) and CO,and simulated the high-O_(3)-concentration incident in Suzhou by WRF-Chem model for exploring the impact of lake-land breeze on O_(3) migration.From 2016 to 2019,O_(3) concentration in Suzhou evidently exceeded the limit of the relevant state standard,particularly in 2017.The days when O_(3) pollution occurred had obviously seasonal feature,and particularly in spring and summer,O_(3) became the primary pollutant;as to the O_(3) monthly variation,O_(3) concentration featured bimodal pattern,and the peaks of the first two years appeared slightly earlier than the next two years,while for each season the diurnal variation was all characterized by a single-peak pattern,and the concentration reached the highest at 15:00.Spatially,the urban O_(3) concentration was generally higher than that of the towns in the vicinity of Suzhou,however,in the summer of 2017 when the lake-land breeze prevailed,the situation became totally in opposition.Furthermore,there appeared an obvious O_(3)“weekend effect”during summer,and the O_(3) concentration at night and in the morning on weekends was higher than that on weekdays,yet O_(3) concentration was much higher during the O_(3) peak-value period on weekdays.To sum up,the simulated high-O_(3)-concentration incident of Suzhou proved the existence of lake-land breeze from Lake Taihu,and during the high-temperature period,the lake breeze brought O_(3) moving from Suzhou’s urban area to the nearby towns in its downwind,causing the O_(3) concentration in the towns northeast to Suzhou to rise higher than that in the urban area;moreover,through analyzing the co-relationship between atmospheric oxidant OX(O_(3)+NO_(2))and O_(3) as well as NO_(2),O_(3) concentration was closely correlated with the presences of NO_(2) and CO,and that during the daytime,the OXin Suzhou was controlled by O_(3),but was totally controlled by NO_(2) at the night in winter.