珠三角地区大气PM2.5理化特性季节规律与成因

Causes,physical and chemical properties of atmospheric PM_(2.5) in Pearl River Delta during four seasons

基于珠三角大气超级站2013年8月至2014年3月PM2.5、PM2.5中主要水溶性无机离子组分及其重要气态前体物等参数的逐时在线监测结果,揭示当地大气PM2.5中二次无机组分与其气态前体物的相互作用,以及PM2.5理化特性与成因的季节差异。结果表明,观测期间,PM2.5、PM10的年平均质量浓度分别为64.2、105.1μg/m3,PM2.5在PM10中所占比例（PM2.5/PM10）平均为61.1%。SO2-4、NO-3、NH＋4的年平均质量浓度分别为16.6、9.0、10.2μg/m3,3者之和（SNA）占PM2.5的比例（SNA/PM2.5）平均为55.8%,体现了二次转化对珠三角地区PM2.5污染的重要影响;不同季节,SNA/PM2.5为46.0%--64.3%,夏季最低,冬季最高,其中SO2-4、NH＋4对PM2.5的贡献相对稳定,NO-3贡献的季节差异较大;秋、冬季各项观测参数浓度的日变化规律相对明显,夏季除HNO3和NH3外,多项观测参数在低浓度水平波动,日变化规律不明显;珠三角大气中具有足量气态NH3以中和硫酸盐和硝酸盐,PM2.5中NH＋4、SO2-4、NO-3主要以（NH4）2SO4和NH4NO3形式存在;本研究站点夏季的硫氧化率和氮氧化率均高于广州市,这充分体现了该站点的区域性特征。

Based on the online observation of PM2.5,its major water-soluble inorganic ions and gaseous precursors during August of 2013 to March of 2014 at the atmospheric supersite in Pearl River Delta,the inter-action of the secondary compositions and their precursors were discussed.And the seasonal variation patterns of physical and chemical properties of atmospheric PM2.5 were revealed.During the whole measurement period,the average concentrations of PM2.5and PM10 were 64.2,105.1μg/m3.And the ratio of PM2.5/PM10 was 61.1%.The average concentrations of SO2-4,NO-3and NH＋4were 16.6,9.0,10.2μg/m3.And their sum contribution to PM2.5（SNA/PM2.5）was 55.8%.It indicated that secondary transformation played an important role in PM2.5pollution.The average SNA/PM2.5varied from 46.0%to 64.3% during four seasons.It was lowest in summer and highest in winter.The contributions of SO2-4and NH＋4to PM2.5 were relatively stable,while the contributions of NO-3in different seasons were quite different.Most of the pollutants showed obvious diurnal variations during autumn and winter,with high concentrations at night and low values during the daytime.And quite a few of them fluctuated at low levels with no clear diurnal variations in summer.NH3 was abundant to neutralize sulfate and nitrate.And NH＋4,SO2-4,NO-3should be mainly in the form of（NH4）2SO4and NH4NO3 in PM2.5.The average sulfur oxidation ratio and nitrogen oxidation ratio of the supersite were higher than those of Guangzhou,which reflecting the regional property of the supersite.