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Published in

European Geosciences Union, Atmospheric Chemistry and Physics, 12(20), p. 7359-7372, 2020

DOI: 10.5194/acp-20-7359-2020

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Enhanced growth rate of atmospheric particles from sulfuric acid

Journal article published in 2020 by Dominik Stolzenburg ORCID, Mario Simon ORCID, Ananth Ranjithkumar, Andreas Kürten, Katrianne Lehtipalo ORCID, Hamish Gordon ORCID, Sebastian Ehrhart ORCID, Lukas Pichelstorfer, Tuomo Nieminen ORCID, Xu-Cheng He ORCID, Sophia Brilke ORCID, Mao Xiao, António Amorim, Rima Baalbaki ORCID, Henning Finkenzeller ORCID and other authors.
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Abstract. In the present-day atmosphere, sulfuric acid is the most important vapour for aerosol particle formation and initial growth. However, the growth rates of nanoparticles (<10 nm) from sulfuric acid remain poorly measured. Therefore, the effect of stabilizing bases, the contribution of ions and the impact of attractive forces on molecular collisions are under debate. Here, we present precise growth rate measurements of uncharged sulfuric acid particles from 1.8 to 10 nm, performed under atmospheric conditions in the CERN (European Organization for Nuclear Research) CLOUD chamber. Our results show that the evaporation of sulfuric acid particles above 2 nm is negligible, and growth proceeds kinetically even at low ammonia concentrations. The experimental growth rates exceed the hard-sphere kinetic limit for the condensation of sulfuric acid. We demonstrate that this results from van der Waals forces between the vapour molecules and particles and disentangle it from charge–dipole interactions. The magnitude of the enhancement depends on the assumed particle hydration and collision kinetics but is increasingly important at smaller sizes, resulting in a steep rise in the observed growth rates with decreasing size. Including the experimental results in a global model, we find that the enhanced growth rate of sulfuric acid particles increases the predicted particle number concentrations in the upper free troposphere by more than 50 %.