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The hygroscopic properties of aerosol formed by oxidation of three monoterpenes, limonene -pinene, and -pinene, were measured using a tandem differential mobility annalyzer (TDMA). The experiments were performed in the European Photoreactor (EUPHORE) in Valencia, Spain. The experiments included ozonolysis and photooxidation with and without ammonium sulfate seed aerosol. Pure organic particles, formed by oxidation of the terpenes in the absence of the seed aerosal, proved to be slightly hygroscopic. The hgroscopic growth factor (G) was close to 1.10 at relative humidity 84% + 1%, which is often observed as the G of the less hygroscopic mode of atmospheric aerosol in field measurements. In the experiments with ammonium sulfate seed aerosol G decreased from approximately 1.5 before the start of terpene oxidation to approximately 1.1 as the oxidation products condensed on the particles. G was not proportional to the organic layer thickness but decreased with increasing organic volume fraction. Our analysis shows that in the internally mixed particles, ammonium sulfate and the organic products take up water independently of one another.

Additional information

Authors: VIRKULA A, Environment Institute, JRC Ispra (IT);VAN DINGENEN R, Environment Institute, JRC Ispra (IT);RAES F, Environment Institute, JRC Ispra (IT);HJORTH J, Environment Institute, JRC Ispra (IT)
Bibliographic Reference: Article: Journal of Geophysical Research, 1998
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