二氧化硫/水/空气体系气溶胶成核实验研究

摘要

以 X-射线为辐射电离源对二氧化硫/水/空气体系的气溶胶成核过程进行了研究。实验结果表明,新生粒子来源于离子诱导成核与均相成核两种机制,前者产生带电颗粒,后者产生中性颗粒。离子对粒子成核有着重要的贡献,对粒子生长作用不明显,SO2对粒子成核与生长均有贡献。成核粒子谱分布呈双峰模式,其峰值会随着气体流速发生偏移。在低SO2浓度情况下,离子诱导成核占主导地位,随着SO2浓度的增加,均相成核的作用越来越明显。%New particle formation phenomena in the troposphere have received considerable attention, but the exact mechanism controlling the early stages of aerosol nucleation and growth is still not understood. In this paper, soft X-ray radiolysis of SO2/H2O/Air gas mixtures is carried out to investigate the competitive processes of ion-induced and binary homogeneous nucleation, experimentally. The electrical mobility distributions of newly formed particles were measured with a scanning mobility particle sizer (SMPS). Charged particles in the system are indicative of ion-induced nucleation; uncharged particles are produced by homogeneous nucleation. Ion, which mainly contributed to aerosol nucleation process, had nearly no effect on aerosol growth process. In contrast, SO2 enhanced both aerosol nucleation and growth process. The electrical mobility distribution of nanometer-sized particles appeared to be bimodal peaks. The position of big ones would shift with the flow rate of the gas mixture. At low SO2 concentrations, ion-induced nucleation mechanism may be a dominant factor; however, at increased SO2 concentrations the contribution of binary homogeneous nucleation relative to that of ion-induced nucleation increases accordingly.