Hygroscopicity of nanoparticles produced from homogeneous nucleation in the CLOUD experiments

  • Sulfuric acid, amines and oxidized organics have been found to be important compounds in the nucleation and initial growth of atmospheric particles. Because of the challenges involved in determining the chemical composition of objects with very small mass, however, the properties of the freshly nucleated particles and the detailed pathways of their formation processes are still not clear. In this study, we focus on a challenging size range, i.e. particles that have grown to diameters of 10 and 15nm following nucleation, and measure their water uptake. Water uptake constrains their chemical composition. We use a nanometer-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) at subsaturated conditions (ca. 90% relative humidity at 293 K) to measure the hygroscopicity of particles during the seventh Cosmics Leaving OUtdoor Droplets (CLOUD7) experiments performed at CERN in 2012. In CLOUD7, the hygroscopicity of nucleated nanoparticles was measured in the presence of sulfuric acid, sulfuric acid-dimethylamine, and sulfuric acid-organics derived from α-pinene oxidation. The hygroscopicity parameter Κ decreased with increasing particle size indicating decreasing acidity of particles. No clear effect of the sulfuric acid monomer concentrations on the hygroscopicities of 10nm particles produced from sulfuric acid and dimethylamine was observed, whereas the hygroscopicity of 15nm particles sharply decreased with decreasing sulfuric acid monomer concentrations. In 20 particular, when the concentrations of sulfuric acid was 5.1 x 106 molecules cm exp -3 in the gas phase, and the dimethylamine mixing ratio was 11.8 ppt, the measured Κ of 15nm particles was 0.3 ± 0.01 close to the value reported for dimethylamine sulfate (DMAS) (Κ DMAS ~ 0.28). Furthermore, the difference in Κ between sulfuric acid and sulfuric acid-dimethylamine experiments increased with increasing particle size. The Κ values of particles in the presence of sulfuric acid and organics were much smaller than those of particles in the presence of sulfuric acid and dimethylamine. This suggests that the organics produced from α-pinene ozonolysis play a significant role in particle growth already at 10nm sizes.

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Author:Jaeseok Kim, Lars Ahlm, Taina Yli-Juuti, Michael Joseph Lawler, Helmi Keskinen, Jasmin Tröstl, Siegfried SchobesbergerORCiDGND, Jonathan DuplissyORCiD, Antonio AmorimORCiD, Federico BianchiORCiDGND, Neil McPherson DonahueORCiDGND, Richard C. FlaganORCiD, Jani Hakala, Martin HeinritziORCiDGND, Tuija Jokinen, Christoph Andreas KürtenORCiDGND, Ari Laaksonen, Katrianne LehtipaloORCiDGND, Pasi Miettinen, Tuukka Petäjä, Matti P. RissanenORCiD, Linda Rondo, Kamalika Sengupta, Mario SimonORCiD, Antonio Tomé, Christina Williamson, Daniela WimmerORCiDGND, Paul M. WinklerORCiD, Sebastian Ehrhart, Penglin Ye, Jasper KirkbyORCiD, Joachim CurtiusORCiD, Markku KulmalaORCiDGND, Kari E. J. Lehtinen, James N. Smith, Ilona RiipinenORCiD, Annele Virtanen
Parent Title (English):Atmospheric chemistry and physics / Discussions
Publisher:European Geosciences Union
Place of publication:Katlenburg-Lindau
Document Type:Article
Date of Publication (online):2015/07/20
Date of first Publication:2015/07/20
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2016/06/17
Page Number:31
First Page:19803
Last Page:19833
© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License.
Institutes:Geowissenschaften / Geographie / Geowissenschaften
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Licence (German):License LogoCreative Commons - Namensnennung 3.0