Rebounding hygroscopic inorganic aerosol particles: Liquids, gels, and hydrates

Abstract

Particle rebound was studied for ten atmospherically relevant inorganics. Experiments were conducted with submicron particles in aerosol form to a relative humidity (RH) of <5% followed by progressive exposure to RH up to 95% for 2 s. At low RH, particles of MgCl 2 , NaCl, NH 4 Cl, KCl, (NH 4) 2 SO 4 , and Na 2 SO 4 crystallized. As RH increased, these particles completed the transition from rebounding to adhering close to their deliquescence RH (DRH). The onset of decreased rebound, however, was below the DRH. Rebound curves for particles of MgCl 2 , NH 4 NO 3 , MgSO 4 , and NaNO 3 had different features than explained by water adsorption and deliquescence. Particles of MgCl 2 had rebound curves characterized by two domains, corresponding to its two hydrates. At low RH, particles of MgSO 4 and NaNO 3 did not crystallize but rebound occurred, suggesting a glassy or high-viscosity though noncrystalline state. Gel formation for MgSO 4 can increase viscosity, affecting rebound behavior. Particles of NH 4 NO 3 adhered even to <5% RH, suggesting a low-viscosity state even to low RH. Particles of NH 4 HSO 4 were investigated as a special case by exposure to 5 ppm ammonia at 10% and 90% RH. At low RH, these particles still had sufficient molecular diffusivity to maintain active heterogeneous chemistry, although with some kinetic limitations. The different behaviors between nitrates and sulfates suggest different roles of heterogeneous chemistry in regions affected by NO x compared to SO 2 emissions. The results of this study could have implications for the use of different wet and dry seed particles in chamber experiments.

Mutual promotion between aerosol particle liquid water and particulate nitrate enhancement leads to severe nitrate-dominated particulate matter pollution and low visibility

“…A weather station (Met One Instruments Inc., USA) was used to measure meteorological parameters (ambient RH, temperature, wind speed, wind direction), and detailed aerosol particle physical and chemical properties were recorded using a suite of state-of-the-art instrumentation. The hygroscopic growth factor (HGF) of submicrometer aerosol particles was measured using a hygroscopicity tandem differential mobility analyzer (H-TDMA, TROPOS, Germany; Wu et al, 2011;Massling et al, 2011;Wang et al, 2018;Wu et al, 2016;Liu et al, 1978), and data retrieval followed the TDMA inv method in Gysel et al (2009). The hygroscopicity parameter (κ) was estimated using the κ-Köhler approach (Petters and Kreidenweis, 2007;Köhler, 1936).…”

Solid Ammonium Nitrate Aerosols as Efficient Ice Nucleating Particles at Cirrus Temperatures

“…In contrast to other atmospherically relevant inorganic components like sea salt and ammonium sulfate ((NH 4 ) 2 SO 4 , AS), aqueous AN particles show a strong tendency to remain in the supersaturated liquid state even at a very low relative humidity with respect to liquid water (RH w ). Whereas aqueous sea salt and AS particles show efflorescence in the range of about 35% to 45% RH w for temperatures between 298 and 238 K (Cziczo & Abbatt, 1999; Koop, Kapilashrami, et al, 2000), the homogeneous crystallization of AN from aqueous AN solution droplets does not even occur at RH w close to 0%, both at room temperature and at a temperature as low as 238 K (Cziczo & Abbatt, 2000; Li et al, 2017; Lightstone et al, 2000; Schlenker & Martin, 2005). Regarding the impact of AN particles on cloud formation and, specifically, on the formation of high‐altitude cirrus clouds involving the nucleation of ice particles, a predominance of the liquid state would only favor cirrus formation via the homogeneous freezing of the aqueous AN solution droplets at elevated humidity levels (Cziczo & Abbatt, 2001; Koop, Luo, et al, 2000; Tabazadeh & Toon, 1998).…”

Physical state of 2-methylbutane-1,2,3,4-tetraol in pure and internally mixed aerosols

“…Aerosol particles have been identified as a key factor for answering what drives our climate and, in particular, what is the anthropogenic contribution to climate change (Carslaw et al, 2013;Gordon et al, 2016;IPCC, 2013;Seinfeld et al, 2016). Aerosol particles influence our climate (i) directly through scattering and reflection as well as absorption of sunlight and of infrared radiation emitted from the earth's surface and (ii) indirectly by acting as nuclei for water and ice cloud formation (Andreae, 1997;Haywood and Boucher, 2000;Lohmann and Feichter, 2005;Pöschl, 2005). These direct and indirect effects are governed by the particles' chemical and physical properties such as their chemical composition and phase state, both of which affect important aerosol processes such as gas-particle partitioning, the rate of surface or bulk chemical reactions, water uptake kinetics, their light-scattering properties, and their ability to act as cloud condensation nuclei or ice nuclei (Baustian et al, 2013;Berkemeier et al, 2013Berkemeier et al, , 2014Kidd et al, 2014;Kuwata and Martin, 2012;Martin, 2000;Moise et al, 2015;Perraud et al, 2012;Saukko et al, 2012b;Schill et al, 2014;Shiraiwa et al, 2012;Zarzana et al, 2012).…”