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Open AccessArticle

Temperature-Dependent Diffusion of H2SO4 in Air at Atmospherically Relevant Conditions: Laboratory Measurements Using Laminar Flow Technique

1
Finnish Meteorological Institute, Erik Palménin aukio 1, P.O. Box 503, FIN-00100 Helsinki, Finland
2
Laboratory of Aerosols Chemistry and Physics, Institute of Chemical Process Fundamentals Academy of Sciences of the Czech Republic, Rozvojova 135, CZ-165 02 Prague 6, Czech Republic
3
Department of Physical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 8, CZ-128 43 Prague, Czech Republic
4
Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
5
Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2 A, P.O. Box 64, FIN-00014 Helsinki, Finland
6
Department of Environmental Science and Analytical Chemistry (ACES) and Bolin Centre for Climate Research, Stockholm University, SE-10691 Stockholm, Sweden
7
Department of Multiphase Reactors, Institute of Chemical Process Fundamentals Academy of Sciences of the Czech Republic, Rozvojova 135, CZ-165 02 Prague 6, Czech Republic
*
Author to whom correspondence should be addressed.
Atmosphere 2017, 8(7), 132; https://doi.org/10.3390/atmos8070132
Received: 5 June 2017 / Revised: 17 July 2017 / Accepted: 19 July 2017 / Published: 22 July 2017
(This article belongs to the Special Issue Morphology and Internal Mixing of Atmospheric Particles)
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Abstract

We report flow tube measurements of the effective sulfuric acid diffusion coefficient at ranges of different relative humidities (from ∼4 to 70%), temperatures (278, 288 and 298 K) and initial H2SO4 concentrations (from 1 × 106 to 1 × 108 molecules·cm−3). The measurements were carried out under laminar flow of humidified air containing trace amounts of impurities such as amines (few ppt), thus representing typical conditions met in Earth’s continental boundary layer. The diffusion coefficients were calculated from the sulfuric acid wall loss rate coefficients that were obtained by measuring H2SO4 concentration continuously at seven different positions along the flow tube with a chemical ionization mass spectrometer (CIMS). The wall loss rate coefficients and laminar flow conditions were verified with additional computational fluid dynamics (CFD) model FLUENT simulations. The determined effective sulfuric acid diffusion coefficients decreased with increasing relative humidity, as also seen in previous experiments, and had a rather strong power dependence with respect to temperature, around ∝ T5.6, which is in disagreement with the expected temperature dependence of ∼T1.75 for pure vapours. Further clustering kinetics simulations using quantum chemical data showed that the effective diffusion coefficient is lowered by the increased diffusion volume of H2SO4 molecules via a temperature-dependent attachment of base impurities like amines. Thus, the measurements and simulations suggest that in the atmosphere the attachment of sulfuric acid molecules with base molecules can lead to a lower than expected effective sulfuric acid diffusion coefficient with a higher than expected temperature dependence. View Full-Text
Keywords: diffusion coefficient; sulfuric acid; laminar flow tube; CFD; amines; clustering kinetics simulations diffusion coefficient; sulfuric acid; laminar flow tube; CFD; amines; clustering kinetics simulations
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Brus, D.; Škrabalová, L.; Herrmann, E.; Olenius, T.; Trávničková, T.; Makkonen, U.; Merikanto, J. Temperature-Dependent Diffusion of H2SO4 in Air at Atmospherically Relevant Conditions: Laboratory Measurements Using Laminar Flow Technique. Atmosphere 2017, 8, 132.

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