Cloud condensation nuclei activity of isoprene secondary organic aerosol
Cloud condensation nuclei activity of isoprene secondary organic aerosol
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DOI：
10.1029/2010jd014706
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发表时间：
2011-01-22
影响因子：
4.4
通讯作者：
Pandis, Spyros N.
中科院分区：
文献类型：
--
作者：
Engelhart, Gabriella J.;Moore, Richard H.;Pandis, Spyros N.
本研究探讨了异戊二烯二级有机气溶胶（SOA）的云凝结核（CCN）活性，这可能是全球有机颗粒物和CCN的重要来源，是在温度可控的SOA室中由HONO/HOOH光解与OH氧化产生的。CCN浓度、活化直径和液滴生长动力学信息作为过饱和（从0.3%到1.5%）的函数被监测了几个小时，使用连接到扫描迁移率粒度仪的圆柱形连续流式热梯度CCN计数器。初始SOA浓度范围为2 ~ 30 μ g (-3)， CCN活性与单萜SOA相似，1.5%过饱和时活化直径为35 nm， 0.6%过饱和时活化直径为72 nm。在一些实验中，随着SOA的化学老化，CCN活性略有改善，并且在SOA生产过程中不显著依赖于NOx的水平。测定的活化直径对应于吸湿性参数kappa值为0.12，类似于单萜烯SOA的kappa值为0.1 +/- 0.04。从SOA的过滤样品中提取的水溶性碳的分析表明，它的kappa为0.2-0.3，意味着平均摩尔质量在90和150g mol（-1）之间（假设相对于水的表面张力分别降低0和5%）。这些发现与已知的异戊二烯氧化产物一致。通过阈值液滴生长分析，确定异戊二烯SOA的CCN活化动力学与纯硫酸铵气溶胶相似。
This work explores the cloud condensation nuclei (CCN) activity of isoprene secondary organic aerosol (SOA), likely a significant source of global organic particulate matter and CCN, produced from the oxidation with OH from HONO/HOOH photolysis in a temperature-controlled SOA chamber. CCN concentrations, activation diameter, and droplet growth kinetic information were monitored as a function of supersaturation (from 0.3% to 1.5%) for several hours using a cylindrical continuous-flow streamwise thermal gradient CCN counter connected to a scanning mobility particle sizer. The initial SOA concentrations ranged from 2 to 30 mu g m(-3) and presented CCN activity similar to monoterpene SOA with an activation diameter of 35 nm for 1.5% supersaturation and 72 nm for 0.6% supersaturation. The CCN activity improved slightly in some experiments as the SOA aged chemically and did not depend significantly on the level of NOx during the SOA production. The measured activation diameters correspond to a hygroscopicity parameter kappa value of 0.12, similar to kappa values of 0.1 +/- 0.04 reported for monoterpene SOA. Analysis of the water-soluble carbon extracted from filter samples of the SOA suggest that it has a kappa of 0.2-0.3 implying an average molar mass between 90 and 150 g mol(-1) (assuming a zero and 5% surface tension reduction with respect to water, respectively). These findings are consistent with known oxidation products of isoprene. Using threshold droplet growth analysis, the CCN activation kinetics of isoprene SOA was determined to be similar to pure ammonium sulfate aerosol.