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 15 nm following nucleation, and measure their water uptake. Water uptake is useful information for indirectly obtaining chemical composition of aerosol particles. 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) campaign 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 concentration on the hygroscopicity of 10 nm particles produced from sulfuric acid and dimethylamine was observed, whereas the hygroscopicity of 15 nm particles sharply decreased with decreasing sulfuric acid concentrations. In particular, when the concentration of sulfuric acid was 5.1 × 106 molecules cm−3 in the gas phase, and the dimethylamine mixing ratio was 11.8 ppt, the measured κ of 15 nm particles was 0.31 ± 0.01: close to the value reported for dimethylaminium sulfate (DMAS) (κDMAS ∼ 0.28). Furthermore, the difference in κ between sulfuric acid and sulfuric acid–imethylamine 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 even at 10 nm sizes.

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Author:Jaeseok Kim, Lars Ahlm, Taina Yli-Juuti, Michael Joseph Lawler, Helmi Keskinen, Jasmin Tröstl, Siegfried Schobesberger, Jonathan DuplissyORCiD, Antonio Amorim, Federico Bianchi, Neil McPherson Donahue, Richard C. Flagan, Jani Hakala, Martin Heinritzi, Tuija Jokinen, Andreas Kürten, Ari Laaksonen, Katrianne Lehtipalo, Pasi Miettinen, Tuukka Petäjä, Matti P. Rissanen, Linda Rondo, Kamalika Sengupta, Mario Simon, Antonio Tomé, Christina Williamson, Daniela Wimmer, Paul M. Winkler, Sebastian Ehrhart, Penglin Ye, Jasper Kirkby, Joachim CurtiusORCiD, Urs BaltenspergerORCiDGND, Markku Kulmala, Kari E. J. Lehtinen, James N. Smith, Ilona Riipinen, 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):2016/01/18
Date of first Publication:2016/01/18
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2016/05/02
Page Number:12
First Page:293
Last Page:304
© Author(s) 2016. CC 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