Seeded Crystal Growth of Internally Mixed Organic-Inorganic Aerosols: Impact of Organic Phase State.

Atmospheric aerosols are complex with both inorganic and organic components. The soluble inorganics can transition between aqueous and crystalline phases through efflorescence and deliquescence. This study focuses on the efflorescence of (NH)SO/organic particles by seeded crystal growth through contact with a crystal of (NH)SO.

Immersion and Contact Efflorescence Induced by Mineral Dust Particles.

The phase state of inorganic salt aerosols impacts their properties, including the ability to undergo hygroscopic growth, catalyze heterogeneous reactions, and act as cloud condensation nuclei. Here, we report the first observation of contact efflorescence by mineral dust aerosol. The efflorescence of aqueous ammonium sulfate ((NH)SO) and sodium chloride (NaCl) droplets by contact with three types of mineral dust particles (illite, montmorillonite, and NX illite), were examined using an optical levitation chamber.

Contact efflorescence as a pathway for crystallization of atmospherically relevant particles.

Inadequate knowledge of the phase state of atmospheric particles represents a source of uncertainty in global climate and air quality models. Hygroscopic aqueous inorganic particles are often assumed to remain liquid throughout their atmospheric lifetime or only (re)crystallize at low relative humidity (RH) due to the kinetic limitations of efflorescence (salt crystal nucleation and growth from an aqueous solution). Here we present experimental observations of a previously unexplored 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 metastable aqueous microdroplet.