珠江三角洲地区气溶胶分档活化特性与闭合实验

Size-resolved activation properties of aerosols over the Pearl River Delta and ansensitivitystudy of the CCN slosure

使用SMPS与CCNC系统相结合,于2011年12月在广州番禺大气成分站开展了40～200nm气溶胶粒子的分档活化观测.活化率曲线和统计结果显示0.109%、0.20%、0.39%、0.67%四个过饱和比下临界干粒径Dmid依次为143.7,99.5,74.7,62.6nm;对应的截断粒径Dcut为171.9,119.1,90.2,72.5nm.进一步分析表明,气溶胶粒子的活化能力主要受粒径控制,成分与混合状态的影响在活化临界位置附近最为显著.本次观测结果与华北地区和周边城郊地区相比,气溶胶活化能力较弱.闭合实验计算得到的CCN数浓度与观测值存在很好的相关性(R2=0.9477),计算值较观测值高约16%.考虑到仪器系统误差等因素,认为两者闭合良好.对CCN数浓度计算中使用的3个因子,即气溶胶数浓度NCN、气溶胶谱型NSD、活化率曲线ARSR进行了敏感性实验,结果显示各因子对CCN数浓度的影响程度存在如下关系:NCN>NSD>ARSR.

This work utilized SMPS and CCNC system to measure size-resolved activation properties of atmospheric particles with diameters of 40-200nm at the CAWNET station in Panyu, Guangzhou, December 2011. The activation curve and statistical results show that the critical dry diameters Druid are 143.7, 99.5, 74.7and 62.6nm, respectively, at supersaturation of 0.109%, 0.20%, 0.39%, 0.67%, and the cut-off diameters Dcut are 171.9, 119.1, 90.2and 72.5nm, respectively. This indicates that the activation ability of an aerosol particle is mostly controlled by its size, while composition and mixing state of the particle have an effect around the activation critical point. It is also found that the activation ability of aerosols observed in this study is generally weaker than that observed in North China and suburban regions. Our results also show that the CCN number concentrationscalculated based on the size-resolved activation ratio and aerosol size distribution is well correlated with the observed valuess, with an average overestimation of 16%.Further sensitivity tests show thatparticle concentration NCN, normalized size distribution NSD and activation curve ARsR are the three most important factors to the calculated CCN concentration and their relative importance are NCN〉 NSD〉 ARSR.