posted on 2018-05-02, 00:00authored byMuhammad
Bilal Altaf, Dabrina D. Dutcher, Timothy M. Raymond, Miriam Arak Freedman
Cloud
condensation nuclei (CCN) activation is sensitive to the
size, composition, and morphology of aerosol particles of <200
nm. By controlling the particle morphology of internally mixed samples
(i.e., homogeneous versus phase separated), we have probed the effect
of morphology on CCN activity using model organic aerosol systems,
where ammonium sulfate was mixed with either pimelic acid or succinic
acid in a 50:50 mixture by weight. Surprisingly, for systems of the
same composition but distinct morphology, we observe a noticeable
impact on CCN activity. Specifically, a phase-separated morphology
results in activation diameters close to that of ammonium sulfate,
while a homogeneous morphology yields an activation diameter in between
the pure inorganic and organic components. Our results suggest that
morphology-resolved CCN data may be an important parameter to consider
in cloud microphysics models to improve predictions of CCN activity
of complex organic aerosols. For laboratory CCN studies, it is important
to control or account for atomized solution drying rates, which have
been shown to affect morphology and ultimately CCN activity.