TY  - JOUR
A1  - Lawler, Michael Joseph
A1  - Winkler, Paul M.
A1  - Kim, Jaeseok
A1  - Ahlm, Lars
A1  - Tröstl, Jasmin
A1  - Praplan, Arnaud Patrick
A1  - Schobesberger, Siegfried
A1  - Kürten, Christoph Andreas
A1  - Kirkby, Jasper
A1  - Bianchi, Federico
A1  - Duplissy, Jonathan
A1  - Hansel, Armin
A1  - Jokinen, Tuija
A1  - Keskinen, Helmi
A1  - Lehtipalo, Katrianne
A1  - Lehtipalo, Katrianne
A1  - Leiminger, Markus
A1  - Petäjä, Tuukka
A1  - Rissanen, Matti P.
A1  - Rondo, Linda
A1  - Simon, Mario
A1  - Sipilä, Mikko
A1  - Williamson, Christina
A1  - Wimmer, Daniela
A1  - Riipinen, Ilona
A1  - Virtanen, Annele
A1  - Smith, James N.
T1  - Unexpectedly acidic nanoparticles formed in dimethylamine-ammonia-sulfuric acid nucleation experiments at CLOUD
T2  - Atmospheric chemistry and physics. Discussion
N2  - 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 physico-chemical 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 that suggests a change to a mixed-phase state as the particles grew beyond this size. The reasons for the very acidic composition remain uncertain, but a possible 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.
Y1  - 2016
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/42014
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-420144
UR  - http://www.atmos-chem-phys.net/16/13601/2016
SN  - 1680-7375
SN  - 1680-7367
N1  - © Author(s) 2016. CC-BY 3.0 License.
VL  - 16
SP  - 1
EP  - 35
PB  - European Geosciences Union
CY  - Katlenburg-Lindau
ER  -