中文摘要：

为研究NO_2对SO_2/H2O/空气体系气溶胶成核过程的影响,采用纳米扫描迁移率粒子粒径谱仪（Nano-SMPS）,对NO_2/SO_2/H2O/空气混合气体在X-射线作用下生成粒子的粒径和浓度进行测量.结果表明,粒子的粒径在2.0-63.8 nm之间,最高数浓度可达到1.4×107cm-3.成核粒子谱的分布呈双峰模式,其中一个谱峰中心位置在4.0 nm附近,另一个在7.0-14.6 nm之间,分别对应于均相成核和离子诱导成核两种过程.在均相成核方面,NO_2和SO_2均能参与气溶胶成核,而对气溶胶的生长没有明显影响,粒子的粒径主要集中在4.0 nm附近.在离子诱导成核方面,当混合气体中φ（SO_2）低于2.12×10-6时,加入NO_2可促进粒子生成;而当超过该值时,NO_2的加入反而会降低气溶胶成核粒子的总数浓度.当φ（SO_2）为3.61×10-6时,在φ（NO_2）分别为0.13×10-6、0.18×10-6和0.84×10-6的条件下,气溶胶成核粒子的总数浓度比不含NO_2下分别减少了25.9%、33.1%和49.0%.研究显示,NO_2和SO_2对·OH的反应竞争作用是影响NO_2/SO_2/H2O/空气体系气溶胶成核的重要机制.

英文摘要：

New particle formation induced by a soft X-ray radiolysis in NO_2/SO_2/H_2O/air gas mixtures was investigated by using a nanometer scanning mobility particle sizer（ Nano-SMPS）. The role of NO_2 in the formation was especially discussed. The electrical mobility size distribution of the newly formed particles was measured; it exhibited a bimodal shape. The diameter of particles was measured from 2. 02 to 63. 80 nm. The maximum concentration reached 1. 4 × 107cm- 3. The intensity of the first peak with center at -4. 0 nm could be enhanced with both NO_2 and SO_2gases,and its formation mechanism was assigned as homogenous nucleation. The second peak with a bigger center size（ 7. 0-14. 6 nm） was mainly from the ion-induced nucleation process,and the addition of NO_2 and SO_2gases enhanced both its intensity and center size. In addition,the experimental results also showed that the total particle number was influenced by the concentrations of SO_2 and NO_2. The total particle number increased with NO_2 when the concentration of SO_2 was below 2. 12 × 10-（- 6）,whereas NO_2 exerted a negative effect on the particle number when the concentration of SO_2 was high.When the concentration of SO_2 was fixed at 3. 61 × 10-（- 6）,the concentrations of new particle decreased 25. 9%,33. 1% and49. 0% after NO_2 with concentrations of 0. 13 × 10-（- 6）,0. 18 × 10-（- 6）and 0. 84 × 10-（- 6）was added in the reaction chamber. These phenomena can be explained by the competition of NO_2 and SO_2in the production channel of ·OH radicals.