increased hygroscopicity of arizona test Dust seeds by secondary organic aerosol coating from α-pinene ozonolysis

Helmi Keskinen, Aki-Matti Kortelainen, Jaatinen, Pasi Yli-Pirilä, Jorma Joutsensaari, -Qing Hao, Pasi Miettinen, Douglas Worsnop, James Smith
2014 unpublished
Keskinen, h., Kortelainen, a.-m., Jaatinen, a., Yli-Pirilä, P., Joutsensaari, J., romakkaniemi, s., hao, l. Q., torvela, t., miettinen, P., virtanen, a., Worsnop, D. r., laaksonen, a. & smith, J. n. 2014: increased hygroscopicity of arizona test Dust seeds by secondary organic aerosol coating from α-pinene ozonolysis. Boreal Env. Res. 19 (suppl. B): 182-190. Organic compounds can enhance the hygroscopic properties of insoluble dust particles and thereby affect their cloud condensation nuclei
more » ... densation nuclei activity in the atmosphere. In this study, Arizona Test Dust (ATD) particles were exposed to oxidized organic vapors from the ozonolysis of α-pinene in a laboratory chamber. The particle size-dependent morphology, inorganic and organic composition and hygroscopic properties were studied. The dust consisted of particles with a range of morphologies from spherical to geometrical, with a size range from 50 nm to 1 µm. Exposure to oxidized organics resulted in a separate mode of secondary organic aerosol (SOA) particles with size ranging below 100 nm and a well-mixed ATD + SOA mode at larger sizes. The O:C mole ratio for the organics produced from α-pinene ozonolysis was stable at 0.4 ± 0.05 in all experiments. The results showed that the hygroscopicities of the ATD particles with a diameter of 100-150 nm were enhanced by a factor of four with the addition of SOA, corresponding to a particulate organic volume fraction of ~0.6 and an average k of 0.09.
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