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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 11 Jan 2019

Research article | 11 Jan 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Measurement Techniques (AMT).

External and Internal CCN Mixtures: Controlled Laboratory Studies of Varying Mixing States

Diep Vu1,2,a, Shaokai Gao1,b, Tyler Berte1,2, Mary Kacarab1,2,c, Qi Yao4, Kambiz Vafai3, and Akua Asa-Awuku1,2,4 Diep Vu et al.
  • 1Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA
  • 2Bourns College of Engineering, Center for Environmental Rese arch and Technology (CE-CERT), Riverside, CA 92507, USA
  • 3Department of Mechanical Eng ineering, Bourns College of Engi neering, University of California, Riverside, CA 92521, USA
  • 4Department of Chemical and Biomolecular Engineering, A. Jame s Clark School of Engineering, University of Maryland, College Park, MD 20742
  • acurrently at: Ford Motor Company, Research & Innovation Center Dearborn, MI 48124, USA
  • bcurrently at: Phillip 66 Research Center, Research and Development, Bartlesville, OK 74004, USA
  • ccurrently at: Georgia Insittute of Technology, Atlanta, GA 30309, USA

Abstract. Particle mixing states modify CCN activity. A method of cloud condensation nuclei (CCN) data analysis for multicomponent mixtures of varying mixing states and its relationship to activation curves consisting of one or more activation points is presented. Simplified two component systems of varying solubility were generated under internal, external, and transitional mixing conditions. κ-Köhler theory predictions were calculated for different organic and inorganic mixtures and compared to experimentally derived kappa values and respective mixing states. This work employs novel experimental methods to provide information on the shifts in CCN activation data due to external to internal particle mixing from controlled laboratory sources. Results show that activation curves consisting of single and double activation points are consistent with internal and external mixtures, respectively. In addition, the height of the plateau at the activation points are reflective of the externally mixed concentration in the mixture. The presence of a plateau indicates that CCN activation curves consisting of multiple inflection points are externally mixed aerosols of varying water-uptake properties. The plateau disappears when mixing is promoted in the flow tube. At the end of the flow tube experiment, the aerosol are internally mixed and the CCN activated fraction data can be fit with a single sigmoidal curve. The technique to mimic external to internally mixed aerosol is applied to non-hygroscopic carbonaceous aerosol with organic and inorganic components. To our knowledge, this work is the first to show controlled CCN activation of mixed non-hygroscopic black carbon with hygroscopic material as the aerosol population transitions from external to internally mixed. Results confirm that CCN activation analysis methods are robust and may be used to infer the mixing state of complex aerosol compositions of unknown origin.

Diep Vu et al.
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Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Diep Vu et al.
Diep Vu et al.
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Publications Copernicus
Short summary
Aerosol-cloud interactions contribute the greatest uncertainty to cloud formation. Aerosol composition is complex and can change quickly in the atmosphere. In this work, we recreate changes in aerosol mixing state with a novel flow tube apparatus and technique and report the subsequent changes on cloud condensation nuclei (CCN) activation. Here, we are the first to verify changes in CCN mixing state with controlled laboratory studies for inorganic and carbonaceous aerosol.
Aerosol-cloud interactions contribute the greatest uncertainty to cloud formation. Aerosol...