苯乙烯-臭氧反应产生的二次有机气溶胶的吸湿性研究

基于自主搭建的加湿串联差分迁移率分析仪(hygroscopic tandem differential mobility analyzer,H-TDMA)和实验室烟雾箱模拟系统,分别对有无种子气溶胶(硫酸铵)存在的条件下,苯乙烯臭氧氧化反应体系产生的二次有机气溶胶(secondary organic aerosol,SOA)的吸湿性进行了研究.通过对反应产生的不同粒径的SOA粒子(70nm,85nm,100nm)的吸湿性测量,发现无论有无种子气溶胶的存在,产生的SOA粒子的吸湿生长因子(growthfactor,GF)(相对湿度为85％)都随着反应时间的继续而逐渐增大；并且在有硫酸铵种子气溶胶存在的条件下产生的SOA的吸湿性比无种子气溶胶情况下产生的粒子的吸湿性更强,但比纯的硫酸铵无机气溶胶的吸湿性要小.分析表明随着氧化反应的进行,更多的吸湿性较大的高极性氧化产物分配到SOA粒子中,导致这些粒子的GF由反应初始阶段的＜1逐渐增大到＞1；而在有种子气溶胶存在的条件下产生的SOA粒子,由于受硫酸铵种子气溶胶较强吸湿性的影响,比没有种子气溶胶时产生的纯SOA相对要强,但这种影响受限于外层包裹的有机组分的较低的吸湿性(相对于硫酸铵),因此远小于纯硫酸铵气溶胶的吸湿生长因子.而不同粒径的SOA粒子的吸湿性生长因子随时间的演化关系所表现出来的一致性,也表明了在本实验条件下,产生的SOA气溶胶粒子的化学组成不依赖于粒子的粒径.

Hygroscopicity of SOA Formed by Ozonolysis of Styrene

The hygroscopic property of secondary organic aerosols(SOA) formed by ozonolysis of styrene has been comprehensively studied on the basis of self-assembled hygroscopic-tandem differential mobility analyzer (H-TDMA) and the homemade smog chamber.SOA was produced in the dry chamber(RH<5%) in the presence and absence of ammonium sulfate seed particles,and the diameter-based(70 nm,85 nm,100 nm) hygroscopic growth factor(GF) of the SOA as a function of time has been measured by using H-TDMA.It is found that the aerosol water uptake increases with reaction time in the experiment for all the SOA with or without seed particles,which indicates that more highly oxidized polar compounds(more hygroscopic) are partitioned into particles according to the reaction time.The effect of seed particles on the hygroscopicity of the aerosols,although limited by the wrap of organic components,is also investigated.And different classified diameters of SOA exhibit similar hygroscopic growth factors,suggesting that the aerosol composition is independent of particle size.