Prediction of cloud condensation nuclei activity for organic compounds using functional group contribution methods

Abstract

Abstract.A wealth of recent laboratory and field experiments demonstrate that organic aerosol composition evolves with time in the atmosphere, leading to changes in the influence of the organic fraction to cloud condensation nuclei (CCN) spectra. There is a need for tools that can realistically represent the evolution of CCN activity to better predict indirect effects of organic aerosol on clouds and climate. This work describes a model to predict the CCN activity of organic compounds from functional group composition. Following previous methods in the literature, we test the ability of semi-empirical group contribution methods in Köh-ler theory to predict the effective hygroscopicity parameter, kappa. However, in our approach we also account for liquidliquid phase boundaries to simulate phase-limited activation behavior. Model evaluation against a selected database of published laboratory measurements demonstrates that kappa can be predicted within a factor of 2. Simulation of homologous series is used to identify the relative effectiveness of different functional groups in increasing the CCN activity of weakly functionalized organic compounds. Hydroxyl, carboxyl, aldehyde, hydroperoxide, carbonyl, and ether moieties promote CCN activity while methylene and nitrate moieties inhibit CCN activity. The model can be incorporated into scale-bridging test beds such as the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to evaluate the evolution of kappa for a complex mix of organic compounds and to develop suitable parameterizations of CCN evolution for larger-scale models.

Establishing the impact of model surfactants on cloud condensation nuclei activity of sea spray aerosol mimics

“…additionally investigated binary salt + nonionic surfactant mixtures and observed that the CCN activation efficiency was, in some cases, actually suppressed relative to ideal mixing. Similarly, Prisle et al (2010) observed that the CCN activation efficiency of binary NaCl + ionic surfactant mixtures was reasonably well described assuming the surfactants to be fully soluble with no impact on surface tension. In this work we will clarify why such highly surface-active species can have, and in the case of fatty acids do have, little impact CCN activation efficiency.…”

“…There have also been direct single particle surface tension measurements for aerosols at sub-saturated humidities . However, it has been suggested that the effects of surface tension lowering on cloud droplet activation are offset by depletion of solutes from the bulk solution as they partition to the surface of microscopic droplets having high surface-area-to-volume ratios (Prisle et al, 2010;Asa-Awuku et al, 2009;Sorjamaa et al, 2004).…”

Microphysical explanation of the RH‐dependent water affinity of biogenic organic aerosol and its importance for climate

“…Optical microscopy images of supermicron samples of MT-and IP-derived SOA show that the RH-dependent phase behavior of these two SOA types is different (Figure 1 and Table S1). For the MT-SOA a single organic-rich phase was observed at <95% RH, but at~95% RH, liquid-liquid phase separation occurred to form two phases: an organic-rich and a water-rich phase (Figure 1b) [Song et al, 2012;Krieger et al, 2012;You et al, 2014;Renbaum-Wolff et al, 2016;Petters et al, 2016]. For IP-SOA, one single phase was observed over the entire RH range (Figure 1a).…”

Water uptake by fresh Indonesian peat burning particles is limited by water-soluble organic matter

“…For instance, chemical characteristics of water-soluble organic matter (WSOM) have been intensively investigated, revealing that WSOM predominantly consists of levoglucosan-like species, carboxylic acids, aldehydes, ketones, aliphatic alcohols, and polyacids (Decesari et al, 2000;Peng et al, 2001;Suzuki et al, 2001;MayolBracero et al, 2002;Chan et al, 2005;Psichoudaki and Pandis, 2013). Recently, the important roles of functional groups in water uptake properties were also investigated by both theoretical and experimental approaches (Suda et al, 2014;Petters et al, 2016).…”

“…The complexity in chemical composition inhibits understanding their water uptake properties at molecular levels (Asa-Awuku et al, 2008;Psichoudaki and Pandis, 2013;Riipinen et al, 2015). To overcome this difficulty, classification of organic compounds using multiple solvents Polidori et al, 2008;Chen et al, 2016), liquid-liquid extraction using 1-octanol and water (Kuwata and Lee, 2017), and solid-phase extraction (Asa-Awuku et al, 2008) has been conducted. Functional-group analysis of segregated organic matter has also been demonstrated as a strong tool to characterize complex mixture of organic compounds (Chen et al, 2016).…”