气象条件对西安市夏季和冬季近地面大气环境污染特征影响

Effects of Meteorological Conditions on the Characteristics of Near-surface Atmospheric Environmental Pollution in Summer and Winter in Xi’an, China

利用2018年1—12月西安市13个环境空气质量监测点的六项大气污染常规分析指标(PM10、PM2.5、O3、SO2、NO2和CO)逐小时监测数据,结合气象条件(温度、相对湿度、风向、风速、大气压、光照、紫外辐射、混合层高度及大气能见度)和颗粒物样品采集,对西安市近地面大气污染物浓度特征进行分析,结果表明,西安市近地面大气污染物浓度呈现明显的季节变化特征,冬季空气污染物主要为颗粒物(PM10、PM2.5)对应质量浓度分别为:(154.04±92.88)、(101.84±60.11)μg·m^−3,PM2.5/PM10的值为0.66,夏季空气污染物主要为O3,质量浓度为(89.07±20.62)μg·m^−3;西安市冬季PM2.5数浓度、表面积浓度、质量浓度分别为(51890±14619)cm^−3、(2882.21±939.83)μm^2·cm^−3、(0.32±0.13)mg·m^−3,PM10数浓度、质量浓度、表面积浓度分别为(51897±14618)cm^−3、(3410.50±1060.31)μm2·cm−3、(0.86±0.29)mg·m^−3,数浓度粒径分布集中在0.010≤dp≤0.484μm,占总数浓度的99.13%,表面积浓度粒径分布集中在0.072≤dp≤8.136μm,占总表面积浓度的98.32%,质量浓度粒径分布集中在0.316≤dp≤8.136μm,占总质量浓度的98.75%。颗粒物数浓度对大气能见度影响最大的3个粒径段分别为dp=0.762μm、dp=1.956μm、dp=1.232μm,3个粒径段与能见度的R2(拟合优度)分别为:0.840、0.789、0.775;西安市夏季,在近地面环境温度大于30.23℃,相对湿度小于58.09%,光照强度大于107.83 W·m^−2,紫外辐射强度大于324.10μW·cm−2时,有利于近地大气层中高质量浓度O3((112.16±53.01)μg·m^−3)的生成与累积。研究结果可为西安市及汾渭平原其他城市大气污染物减排、大气污染防治策略的制定提供数据支持。

Through the routine analysis of six air pollution indexes(PM10,PM2.5,O3,SO2,NO2,CO)monitored hourly by 13 national air quality monitoring stations in Xi'an from January to December 2018,and combined with meteorological conditions(temperature,relative humidity,wind direction,wind speed,barometric pressure,solar radiation,ultraviolet radiation,mixed layer height,visibility)and particulate matters sampling campaign,the characteristics of near-surface air pollutants in Xi'an were analyzed.The results showed an obvious seasonal variation on the concentration of atmospheric pollutants in Xi’an.Air pollutants are mainly particulate matters in winter,the mass concentration of PM10 and PM2.5 were(154.04±92.88)μg·m^−3 and(101.84±60.11)μg·m^−3 respectively.Besides,the value of PM2.5/PM10 was 0.66,while the mass concentration of O3 reached its peak in summer,which was(89.07±20.62)μg·m^−3.In addition,the number concentration,area concentration and mass concentration of PM2.5 in winter were(51890±14619)cm−3,(2882.21±939.83)μm^2·cm^−3 and(0.32±0.13)mg·m^−3 respectively,and that for PM10 were(51897±14618)cm^−3,(3410.50±1060.31)μm^2·cm^−3 and(0.86±0.29)mg·m^−3.The diameter range 0.010‒0.484μm,accounted for 99.13%of the total number concentration.The diameter range 0.072‒8.136μm,accounted for 98.32%of the total area concentration.And the particle size range 0.316‒8.136μm accounted for 98.75%of the total mass concentration.Moreover,the three particle sizes which influence the visibility of the atmosphere most were dp=0.762μm,dp=1.956μm and dp=1.232μm,respectively.The R2(goodness of fit)of the three particle sizes and visibility are:0.840,0.789 and 0.775.When the ambient near-surface temperature is higher than 30.23℃,the relative humidity is less than 58.09%,the solar radiation is greater than 107.83 W·m^−2 and the ultraviolet radiation is greater than 324.10μW·cm−2,it is beneficial to the formation and accumulation of higher mass concentration O3((112.16±53.01)μg·m^−3)in the near-surface atmosphere in summer(in)Xi'an.This study would provide Xi'an and other cities in Fen-wei Plain with data support on atmospheric pollutants reduction and air pollution control strategies.