Unexpectedly acidic nanoparticles formed in dimethylamine–ammonia–sulfuric-acid nucleation experiments at CLOUD
Item
Title (Dublin Core)
Unexpectedly acidic nanoparticles formed in dimethylamine–ammonia–sulfuric-acid nucleation experiments at CLOUD
Description (Dublin Core)
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 NH<sub>3</sub> 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 SO<sub>2</sub> 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.
Creator (Dublin Core)
Lawler, Michael J.
Winkler, Paul M.
Kim, Jaeseok
Ahlm, Lars
Tröstl, Jasmin
Praplan, Arnaud P.
Schobesberger, Siegfried
Kürten, Andreas
Kirkby, Jasper
Bianchi, Federico
Duplissy, Jonathan
Hansel, Armin
Jokinen, Tuija
Keskinen, Helmi
Lehtipalo, Katrianne
Leiminger, Markus
Petäjä, Tuukka
Rissanen, Matti
Rondo, Linda
Simon, Mario
Sipilä, Mikko
Williamson, Christina
Wimmer, Daniela
Riipinen, Ilona
Virtanen, Annele
Smith, James N.
Date (Dublin Core)
2018-09-19
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-16-13601-2016
https://acp.copernicus.org/articles/16/13601/2016/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
