Impact of Organic Coating on Optical Growth of Ammonium Sulfate Particles

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• 作者：Carly B. Robinson ; Gregory P. Schill ; Kyle J. Zarzana ; Margaret A. Tolbert
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：December 3, 2013
• 年：2013
• 卷：47
• 期：23
• 页码：13339-13346
• 全文大小：361K
• 年卷期：v.47,no.23(December 3, 2013)
• ISSN：1520-5851

文摘

Light extinction by particles in Earth鈥檚 atmosphere is strongly dependent on particle size, chemical composition, hygroscopic growth properties, and particle mixing state. Here, the influence of an organic coating on particle optical growth was studied. The particle optical growth factor, fRH_ext, was measured using cavity ring-down aerosol extinction spectroscopy at 532 nm. The particles were composed of ammonium sulfate (AS), 1,2,6-hexanetriol, and mixed particles containing a wet or dry ammonium sulfate core and a 1,2,6-hexanetriol coating. Dry, coated particles were generated by atomization followed by drying. Wet, coated particles were formed via liquid鈥搇iquid phase separation (LLPS). LLPS was achieved by deliquescing and then drying the particles to a relative humidity (RH) between the phase separation RH and the efflorescence RH. For the LLPS particles, the fRH_ext at each RH was between the fRH_ext of ammonium sulfate and that of 1,2,6-hexanetriol. In contrast, for the mixed dry, coated particles, the fRH_ext was the same as 1,2,6-hexanetriol particles. At room temperature, the water uptake properties of AS coated with 1,2,6-hexanetriol are largely dictated by the phase of the AS. Thus, the total water uptake depends on the RH history of the particle and the resulting phase of AS.