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Unexpectedly acidic nanoparticles formed in dimethylamine–ammonia–sulfuric-acid nucleation experiments at CLOUD

  • New particle formation driven by acid–base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10–30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models, which predict a higher dimethylaminium fraction when NH3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : acid ratios lower than 1 : 1. The lowest base fractions were found in particles below 15 nm VMD, with a strong size-dependent composition gradient. The reasons for the very acidic composition remain uncertain, but a plausible explanation is that the particles did not reach thermodynamic equilibrium with respect to the bases due to rapid heterogeneous conversion of SO2 to sulfate. These results indicate that sulfuric acid does not require stabilization by ammonium or dimethylaminium as acid–base pairs in particles as small as 10 nm.

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Author:Michael Joseph Lawler, Paul M. WinklerORCiD, Jaeseok Kim, Lars Ahlm, Jasmin Tröstl, Arnaud Patrick Praplan, Siegfried SchobesbergerORCiDGND, Christoph Andreas KürtenORCiDGND, Jasper KirkbyORCiD, Federico BianchiORCiDGND, Jonathan DuplissyORCiD, Armin HanselORCiD, Tuija Jokinen, Helmi Keskinen, Katrianne LehtipaloORCiDGND, Markus Leiminger, Tuukka Petäjä, Matti P. RissanenORCiD, Linda Rondo, Mario SimonORCiD, Mikko SipiläORCiD, Christina Williamson, Daniela WimmerORCiDGND, Ilona RiipinenORCiD, Annele Virtanen, James N. Smith
URN:urn:nbn:de:hebis:30:3-420159
URL:http://www.atmos-chem-phys.net/16/13601/2016
DOI:https://doi.org/10.5194/acp-16-13601-2016
ISSN:1680-7324
ISSN:1680-7316
Parent Title (English):Atmospheric chemistry and physics
Publisher:European Geosciences Union
Place of publication:Katlenburg-Lindau
Contributor(s):J. Liggio
Document Type:Article
Language:English
Date of Publication (online):2016/11/14
Date of first Publication:2016/11/03
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2016/11/14
Volume:16
Issue:21
Page Number:18
First Page:13601
Last Page:13618
Note:
© Author(s) 2016. CC Attribution 3.0 License.
HeBIS-PPN:424007886
Institutes:Geowissenschaften / Geographie / Geowissenschaften
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 3.0