Mass-based hygroscopicity parameter interaction model and measurement of atmospheric aerosol water uptake

Abstract

Abstract. In this study we derive and apply a mass-based hygroscopicity parameter interaction model for efficient description of concentration-dependent water uptake by atmospheric aerosol particles with complex chemical composition. The model approach builds on the single hygroscopicity parameter model of Petters and Kreidenweis (2007). We introduce an observable mass-based hygroscopicity parameter κ m which can be deconvoluted into a dilute hygroscopicity parameter (κ 0 m ) and additional self-and cross-interaction parameters describing non-ideal solution behavior and concentration dependencies of single-and multi-component systems.For reference aerosol samples of sodium chloride and ammonium sulfate, the κ m -interaction model (KIM) captures the experimentally observed concentration and humidity dependence of the hygroscopicity parameter and is in good agreement with an accurate reference model based on the Pitzer ion-interaction approach (Aerosol Inorganic Model, AIM). Experimental results for pure organic particles (malonic acid, levoglucosan) and for mixed organic-inorganic particles (malonic acid -ammonium sulfate) are also well reproduced by KIM, taking into account apparent or equilibrium solubilities for stepwise or gradual deliquescence and efflorescence transitions.The mixed organic-inorganic particles as well as atmospheric aerosol samples exhibit three distinctly different regimes of hygroscopicity: (I) a quasi-eutonic deliquescence & efflorescence regime at low-humidity where substances are just partly dissolved and exist also in a non-dissolved phase, (II) a gradual deliquescence & efflorescence regime at intermediate humidity where different solutes undergo gradual dissolution or solidification in the aqueous phase; and (III) a dilute regime at high humidity where the solutes are fully dissolved approaching their dilute hygroscopicity.For atmospheric aerosol samples collected from boreal rural air and from pristine tropical rainforest air (secondary organic aerosol) we present first mass-based measurements of water uptake over a wide range of relative humidity (1-99.4 %) obtained with a new filter-based differential hygroscopicity analyzer (FDHA) technique. For these samples the concentration dependence of κ m can be described by a simple KIM model equation based on observable mass growth factors and a total of only six fit parameters summarizing the combined effects of the dilute hygroscopicity parameters, self-and cross-interaction parameters, and solubilities of all involved chemical components. One of the fit parameters represents κ 0 m and can be used to predict critical dry diameters for the activation of cloud condensation nuclei (CCN) as a function of water vapor supersaturation according to Köhler theory. For sodium chloride and ammonium sulfate reference particles as well as for pristine rainforest aerosols consisting mostly of secondary organic matter, we obtained good agreement between the KIM predictions and measurement data of CCN activation.The application of KIM and mass-based me...

Comparing parameterized versus measured microphysical properties of tropical convective cloud bases during the ACRIDICON–CHUVA campaign

“…This implies that the particles were not completely dried in the intake of the probe, and thus prevents a quantitative assessment of κ based on the PCASP and N CCN (S). A possible reason for this behavior in measurements over the Amazon is that the effective hygroscopicity parameters describing water uptake at subsaturated conditions can be substantially lower than at supersaturated conditions (Mikhailov et al, 2013). The analysis of this effect on the ASD measurements from PCASP and UHSAS below cloud base requires considerable efforts, which are beyond the scope of this paper.…”

Hygroscopicity of organic surrogate compounds from biomass burning and their effect on the efflorescence of ammonium sulfate in mixed aerosol particles

“…This increase in viscosity might impede the crystallization of AS in the mixed systems on the timescale of the experiment. Mass transfer limitation effects on the deliquescence or efflorescence process of crystalline organic particles and the water uptake or evaporation have been investigated in several experimental studies (Peng et al, 2001;Choi and Chan, 2002;Sjogren et al, 2007;Zardini et al, 2008;Ciobanu et al, 2010;Smith et al, 2012;Mikhailov et al, 2013;Hodas et al, 2015). Mass transfer limitations may impact the outcome of experiments significantly if the characteristic timescales for equilibration are similar to or larger than the residence time of particles in the experimental setup.…”

CCN activity and organic hygroscopicity of aerosols downwind of an urban region in central Amazonia: seasonal and diel variations and impact of anthropogenic emissions

“…Hygroscopicity also describes particle growth under subsaturated conditions and can be derived from the particle growth factor (GF). However, particles sometime exhibit larger κ values for droplet activation (derived from CCN measurements under supersaturated conditions) than for particle growth (derived from particle GF under subsaturated conditions; e.g., Duplissy et al, 2008;Good et al, 2010;Mikhailov et al, 2013;Pajunoja et al, 2015;Wex et al, 2009). In this paper, "hygroscopicity" represents κ associated with droplet activation derived from CCN measurements unless noted otherwise.…”

“…There have been several studies of aerosol hygroscopicity in the Amazon basin over the past 20 years Mikhailov et al, 2013;Pöhlker et al, 2016;Rissler et al, 2006;Roberts et al, 2001;Vestin et al, 2007;Whitehead et al, 2016;Zhou et al, 2002). Gunthe et al (2009) performed size-resolved CCN measurements during the wet season in February and March 2008 as part of the AMAZE-08 campaign (Martin et al, 2010a).…”