Atmospheric Ion-induced Aerosol Nucleation |
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Authors: | J Curtius E R Lovejoy K D Froyd |
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Institution: | 1. Institut für Physik der Atmosph?re, Universit?t Mainz, Mainz, Germany 2. NOAA ESRL Chemical Sciences Division, Boulder, CO, USA 3. Cooperative Institute for Research in the Environmental Science, University of Colorado, Boulder, CO, USA
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Abstract: | Ion-induced nucleation has been suggested to be a potentially important mechanism for atmospheric aerosol formation. Ions
are formed in the background atmosphere by galactic cosmic rays. A possible connection between galactic cosmic rays and cloudiness
has been However, the predictions of current atmospheric nucleation models are highly uncertain because the models are usually
based on the liquid drop model that estimates cluster thermodynamics based on bulk properties (e.g., liquid drop density and
surface tension). Sulfuric acid (H2SO4) and water are assumed to be the most important nucleating agents in the free troposphere. Measurements of the molecular
thermodynamics for the growth and evaporation of cluster ions containing H2SO4 and H2O were performed using a temperature-controlled laminar flow reactor coupled to a linear quadrupole mass spectrometer as well
as a temperature-controlled ion trap mass spectrometer. The measurements were complemented by quantum chemical calculations
of the cluster ion structures. The analysis yielded a complete set of H2SO4 and H2O binding thermodynamics extending from molecular cluster ions to the bulk, based on experimental thermodynamics for the small
clusters. The data were incorporated into a kinetic aerosol model to yield quantitative predictions of the rate of ion-induced
nucleation for atmospheric conditions. The model predicts that the negative ion-H2SO4-H2O nucleation mechanism is an efficient source of new particles in the middle and upper troposphere. |
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Keywords: | ion-induced nucleation aerosol clusters ions particles atmosphere sulfuric acid |
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