雾天气下二次气溶胶均质成核生长过程  

Analysis of Homogeneous Nucleation and Growth Processes of Secondary Aerosols in Fog Weather

作　　者：刘义[1] 丁珏[1] 刘丽颖 张宝亮[1] 王庆涛[1] 应梦侃[1] 

机构地区：[1]上海大学上海市应用数学和力学研究所,上海200072 [2]上海市嘉定区环境保护局,上海201822

出　　处：《环境科学研究》2012年第11期1222-1228,共7页Research of Environmental Sciences

基　　金：国家自然科学基金项目(10802046);上海大学研究生创新基金项目(SHUCX112356)

摘　　要：二次气溶胶的核化过程涉及分子杂乱运动和碰撞,在分子间的范德华力作用下,大气环境系统中产生分子聚合,形成分子团、胚胎和核.基于此建立二次气溶胶核化和生长模型,并且采用颗粒群平衡模拟和多重蒙特卡洛方法,对雾天气下水汽均质同分子核化及H2O-H2SO4均质异分子核化的过程开展热力学和动力学数值研究.结果表明:在水汽均质核化过程中,当水汽过饱和比从2增至10时,水汽的成核速率增加约73个数量级,形成临界胚胎所需的分子数降低了97.3%.而对于H2O-H2SO4均质异分子核化过程,在环境温度271.15 K,气态H2SO4分子数浓度为5×107cm-3条件下,当RH(相对湿度)由80%增至100%时,二次气溶胶成核速率增加1.4倍;在气态H2SO4分子数浓度较高、RH较大时,核化形成的临界胚胎粒径较小.经过均质核化生长后,二次气溶胶粒径处于1.5～3.5 nm.The nucleation process of secondary aerosols involves the chaotic movement and collision of molecules. Van der Waals forces between molecules lead to molecular aggregation, and then molecular clusters, critical molecular clusters and nuclei are formed. Based on the mechanisms mentioned above, nucleation and growth models were established, and thermodynamic and dynamic properties of homogeneous nucleation processes for one moleeule H20 and different molecules H20-H2SO4 in dense fog atmosphere were simulated by the Particle Balance Model （PBM） and Multi-Monte Carlo （MMC） method. Moreover, the influence of temperature, humidity and vapor supersaturation ratio of the environment on particle nucleation ratio and critical molecular cluster scale were analyzed numerically. The evolution processes of particle number and diameter under different concentrations of sulfuric acid were also discussed. Results showed that during the homogeneous nucleation process of H20, the vapor supersaturation ratio of the environment increased from 2 to 10, then the nucleation rate of H20 increased by about 73 orders of magnitude, and the molecular number to form critical molecular clusters was reduced by 97.3%. During the nucleation processes of H20-H2 SO4, when the environment temperature was 271.15 K and the concentration of ambient gaseous sulfate acid was 5×10^7 cm-3, the particle nucleation rate was increased 1.4 times as the relative humidity was raised from 80% to 100%. The higher concentration of ambient gaseous sulfate acid and relative humidity can lead to larger critical molecular clusters of nuclei. The range of particle diameter by homogeneous nucleation and growth was mainly 1.5-3.5 nm.

关 键 词：二次气溶胶 均质核化 临界胚胎 热力学过程 生长 

分 类 号：X12[环境科学与工程—环境科学]