【摘要】 二次有机气溶胶(SOA)是大气光化学反应的产物,也是城市和郊区大气中细粒子的主要成分.本研究致力于考察高浓度无机气溶胶颗粒对SOA生成的影响.实验系统采用2m3的温控烟雾箱,以干燥的CaSO4和(NH4)2SO4为无机种子气溶胶,研究了间二甲苯/NOx/空气体系光氧化生成SOA的过程.实验结果显示间二甲苯和NOx在紫外光照下会产生大量SOA,SOA产率可用单产物模型表征.CaSO4气溶胶的存在对SOA产率曲线没有明显的影响,而(NH4)2SO4气溶胶的存在使气相半挥发性氧化产物的生成量增加36%,显著地增加了SOA的产率.(NH4)2SO4粒子在含水有机物作用下显现的弱酸性可能是导致这一影响的主要原因.该实验结果有助于更详尽地阐明中国颗粒物污染严重城市SOA的生成机理,从而为进一步修正空气质量模型提供依据.更多还原

【Abstract】 Secondary organic aerosol (SOA), resulting from atmospheric photochemical reactions, is a major contributor to fine particulate matter (PM) in urban and rural areas. The objective of this study is to examine whether and how highly concentrated inorganic aerosols affect SOA formation. The experiments were conducted with irradiated m-xylene/NOx/air mixtures in the presence of dry CaSO4 and (NH4)2SO4 seed aerosols in a 2 m3 smog chamber. The results indicate that SOAs are generated in m-xylene/NOx/air mixtures upon ultraviolet light irradiation, and the SOA yields can be fit to a one-product model. The presence of CaSO4 aerosols in the system was found to have no effect on SOA yields. However, the presence of (NH4)2SO4 aerosols increased the semivolatile organic compound production by 36%, which may be attributed to the weak acidity caused by the interaction of (NH4)2SO4 with water-contained organic material. The outcome of this work can help better understand the SOA formation mechanism, especially in some Chinese big cities experiencing serious PM pollution. Furthermore, the effect of (NH4)2SO4 on SOA formation could be integrated into current air quality simulation models and help improve the accuracy of the model prediction results.更多还原