Contact efflorescence as a pathway for crystallization of atmospherically relevant particles

Published

December 29, 2015

Author(s)

Joshua A. Gordon, Ryan D. Davis, Margaret A. Tolbert, Shuichi B. Ushijimaa, Sara Lance

Abstract

Inadequate knowledge of the phase state of atmospheric particles represents a large source of uncertainty in global climate and atmospheric models. Efflorescence, the process of salt crystal nucleation from a supersaturated aqueous solution upon evaporation, can occur at a higher relative humidity in the presence of a solid particle. Currently, there is no comprehensive parameterization of heterogeneous nucleation. Here we present what may be the first observations of a previously unconsidered heterogeneous nucleation pathway that we have termed “contact efflorescence”, which describes efflorescence initiated by an externally located solid particle coming into contact with the surface of a supersaturated droplet. Contact efflorescence is shown to be a mechanism for crystal formation at high ambient RH. Soluble inorganic crystals were used to induce efflorescence of aqueous ammonium sulfate, sodium chloride, and ammonium nitrate droplets upon contact. Ammonium nitrate, which does not effloresce homogenously from an aqueous microdroplet, effloresced at 50% RH upon a single collision. Sodium chloride and ammonium sulfate were observed to crystallize close to their deliquescence points of 75% and 80% RH, respectively. The atmospheric implications of these observations are discussed. Using soluble inorganic crystalline salts as contact nuclei allowed for comparison of well-defined parameters such as lattice structure, solubility, and deliquescent properties. This study suggests that crystal lattice structure is only the dominant factor in heterogeneous nucleation for very small lattice mismatches, a result that can potentially be used to simplify parameterizations in atmospheric models that consider particle phase.

Citation

Proceedings of the National Academy of Sciences of the United States of America

Volume

112

Issue

52

Pub Type

Journals

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DOI Link

Keywords

heterogeneous nucleation, efflorescence, climate, atmospheric aerosol

Citation

Gordon, J. , Davis, R. , A., M. , B., S. and , S. (2015), Contact efflorescence as a pathway for crystallization of atmospherically relevant particles, Proceedings of the National Academy of Sciences of the United States of America, [online], https://doi.org/10.1073/pnas.1522860113 (Accessed April 19, 2024)