A thermodynamic description for the hygroscopic growth of atmospheric aerosol particles

Abstract

The phase state of atmospheric particulate is important to atmospheric processes, and aerosol radiative forcing remains a large uncertainty in climate predictions. That said, precise atmospheric phase behavior is difficult to quantify and observations have shown that "precondensation" of water below predicted saturation values can occur. We propose a revised approach to understanding the transition from solid soluble particles to liquid droplets, typically described as cloud condensation nucleation -a process that is traditionally captured by Köhler theory, which describes a modified equilibrium saturation vapor pressure due to (i) mixing entropy (Raoult's law) and (ii) droplet geometry (Kelvin effect). Given that observations of precondensation are not predicted by Köhler theory, we devise a more complete model that includes interfacial forces giving rise to predeliquescence, i.e., the formation of a brine layer wetting a salt particle at relative humidities well below the deliquescence point.

Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

“…Papers describing the PINCii instrument and the initial results of its first field deployment and ambient measurements are currently in preparation (see also Sect. 4.1.4; Castarède et al, 2019;Brasseur et al, 2018;Wu et al, 2018).…”

“…An important implication of such findings is that common atmospheric surfactants, such as VOCs, can promote and/or hinder water uptake, changing the hydrophilicity of atmospheric nanoparticles. Additional, laboratory investigations focused on how soluble salts may nucleate ice and whether or not at below-eutectic temperatures sea salts might act as ice-nucleating particles rather than deliquesce as CCN (Kong et al, 2018;Wagner et al, 2018;Castarède and Thomson, 2018). All of these processes may affect cloud evolution and lifetime and thereby impact fundamental environmental processes like the water cycle and radiative balance.…”

“…During HyICE2018 data for instrument intercomparison were also collected using multiple existing INP measurement platforms (PINC, FRIDGE, SPIN, etc.). Campaign data analysis by all involved research groups is currently ongoing (Castarède et al, 2019;Brasseur et al, 2018;Wu et al, 2018). 4.1.5 Boundary layer stability in the Arctic (loop B → E in Fig.…”

Humidity effects on the detection of soluble and insoluble nanoparticles in butanol operated condensation particle counters

“…Hence the structural rearrangment for particles below 5 nm is not as pronounced as for larger ones. This decrease in size for particles > 5 nm is a Normalized Mean Diameter [ ] d p = 4.5 nm d p = 6.0 nm d p = 8.0 nm d p = 10.0 nm d p = 11.0 nm result of solvation on the surface of the NaCl particle caused by the presence of water vapor and thereby a wet surface accrues (Castarède and Thomson, 2018). Due to this dissociation process and the resulting liquid surface the particle attracts more polar vapor molecules.…”

“…Since the flow carrying the monodisperse aerosol and the flow of humid air are joined together in front of the CPC inlet, the increase of cut-off diameters could be a result of the increased attraction of charged NaCl particles to the water vapor under sub-saturated conditions. Thereby the N a + and Cl − ions get separated and form a solvent cage around themselves (Castarède and Thomson, 2018). This reduces the tendency of ions to aggregate (Loudon, 2009).…”