氨对二次有机气溶胶光学特性的影响

Ammonia effect on optical properties of secondary organic aerosols

开展一系列甲苯/NOx光氧化烟雾箱模拟实验,研究大气环境中氨对二次有机气溶胶(SOA)光学特性的影响.采用特氟龙膜作为烟雾箱的反应腔材料,实验过程中同时检测颗粒的粒径分布、光学参数和质谱信息.讨论不同氨体积分数对甲苯光氧化生成SOA的消光截面、复折射率及粒径等参数的变化特征.研究发现,上述实验中SOA的消光作用均以散射为主;随着粒径的增大,消光截面呈指数增大,复折射率则先增大后减小.与低湿无氨环境相比,增湿或加氨均导致SOA中元素O和C物质的量之比增大、复折射率增大;高湿加氨条件下,SOA的粒径明显减小、颗粒数密度急剧增大、SOA中元素O和C的物质的量之比、元素N和C的物质的量之比均增大.

A series of toluene/NOx photo-oxidation experiments were carried out in a smog chamber,and the effect of ammonia on the optical properties of secondary organic aerosols(SOA)evolved by toluene was investigated.The chamber was made of Teflon.The distribution of SOA particle size,extinction efficiency,and mass spectrometric patterns were measured simultaneously during the experimental process.The variation of SOA parameters was discussed,including extinction section,refractive index,and particle size by changing ammonia volume fraction.Results show that the extinction of SOA was dominated by scattering.With the increase of particle size,the extinction cross section exponentially increases,the refractive index firstly increases and then decreases.Compared with low humidity ammonia free environment,the increase of molar ratios of O to C and refractive index of SOA was found either increasing humidity or with ammonia.Under high humidity with ammonia,there is obvious decrease of particle size,sharp increase of number density of particles,and increase both molar ratios of O to C and N to C.