Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches

Leibniz-Institute for Tropospheric Research, Leipzig, Germany
ATMOSPHERIC CHEMISTRY AND PHYSICS (Impact Factor: 5.05). 01/2008; 9(12). DOI: 10.5194/acp-9-3999-2009
Source: DOAJ


We examine the hygroscopic properties of secondary organic aerosol particles generated through the reaction of alpha-pinene and ozone using a continuous flow reaction chamber. The water activity versus composition relationship is calculated from measurements of growth factors at relative humidities up to 99.6% and from measurements of cloud condensation nuclei activity. The observed relationships are complex, suggesting highly non-ideal behavior for aerosol water contents at relative humidities less than 98%. We present two models that may explain the observed water activity-composition relationship equally well. The first model assumes that the aerosol is a pseudo binary mixture of infinitely water soluble compounds and sparingly soluble compounds that gradually enter the solution as dilution increases. The second model is used to compute the Gibbs free energy of the aerosol-water mixture and shows that the aerosol behaves similarly to what can be expected for single compounds that contain a certain fraction of oxygenated and non-polar functional groups.

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    • ") . Previous work [ Petters et al . , 2009 ] suggests that the observed κ HGF < κ CCN discrepancy is caused either by a strongly composition - dependent activity coefficient of water or by a mixture of infinitely water - soluble compounds and sparingly soluble compounds that dissolve in solution at RH > 90% . Our present work suggests that κ HGF < κ CCN because of adsorption - d"
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    ABSTRACT: Aerosol climate effects are intimately tied to interactions with water. Here we combine hygroscopicity measurements with direct observations about the phase of secondary organic aerosol (SOA) particles to show that water uptake by slightly oxygenated SOA is an adsorption-dominated process under subsaturated conditions, where low solubility inhibits water uptake until the humidity is high enough for dissolution to occur. This reconciles reported discrepancies in previous hygroscopicity closure studies. We demonstrate that the difference in SOA hygroscopic behavior in sub- and supersaturated conditions can lead to an effect up to about 30% in the direct aerosol forcing – highlighting the need to implement correct descriptions of these processes in atmospheric models. Obtaining closure across the water saturation point is therefore a critical issue for accurate climate modeling.
    03/2015; 42(8). DOI:10.1002/2015GL063142
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    • "Several previous studies have compared the κ values derived from the methods employing hygroscopicity tandem differential mobility analyzer (h-TDMA) and cloud condensation nuclei (CCN) [Juranyi et al., 2009; Petters et al., 2009; Wex et al., 2009; Good et al., 2010; Henning et al., 2010; Massoli et al., 2010; Snider et al., 2010; Stratmann et al., 2010]. It has been suggested that the HGF derived κ values are lower than those derived from the CCN method, possibly attributable to gradual dissolution of aerosol components when the aerosol solution becomes more diluted at high RH [Petters et al., 2009; Wex et al., 2009; Good et al., 2010]. In addition, the relationship between κ values (hygroscopicity) and the oxidation state of organic aerosols from the aerosol mass spectrometer data has been evaluated, showing that κ (hygroscopicity) increases with the oxidation level of organic aerosols [Massoli et al., 2010; Sorooshian et al., 2010; Duplissy et al., 2011]. "
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    ABSTRACT: The hygroscopic growth factor (HGF) and cloud condensation nuclei (CCN) activity are measured for surrogates that mimic atmospherically relevant oligomers, including glyoxal trimer dihydrate, methyl glyoxal trimer dihydrate, sucrose, methyl glyoxal mixtures with sulfuric acid and glycolic acid, and 2,4-hexandienal mixtures with sulfuric acid and glycolic acid. For the single-component aerosols, the measured HGF ranges from 1.3 to 1.4 at a relative humidity of 90%, and the hygroscopicity parameter (κ) is in the range of 0.06 to 0.19 on the basis of the measured CCN activity and 0.13 to 0.22 on the basis of the measured HGF, compared to the calculated values of 0.08 to 0.16. Large differences exist in the κ values derived using the measured HGF and CCN data for the multi-component aerosols. Our results reveal that, in contrast to the oxidation process, oligomerization decreases particle hygroscopicity and CCN activity and provide guidance for analyzing the organic species in ambient aerosols.
    09/2014; 41(18). DOI:10.1002/2014GL061040
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    • "McMurry et al., 1996). It is important to know the hygroscopic behaviour of aerosol particles as this will determine how they interact with clouds (King et al., 2009; Petters et al., 2009a). This paper presents measurements of the physical and chemical properties of aerosol during July 2007 as part of COPS. "
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    ABSTRACT: The Convective and Orographically-induced Precipitation Study (COPS) campaign was conducted during the summer of 2007. A suite of instruments housed at the top of the Hornisgrinde Mountain (1156 m) in the Black Forest region of south-west Germany provided datasets that allow an investigation into the physical, chemical and hygroscopic properties of the aerosol particles sampled during COPS. Organic mass loadings were found to dominate the aerosol composition for the majority of the project, exceeding 8 µg m−3 during a period of high pressure, high temperature, and low wind speed. The ratio of organic:sulphate sub-micron mass concentration exceeds 10:1 during the same time period. Back trajectories show air from this time-frame passing slowly over the local forest and not passing over any local anthropogenic sources. Occasional peaks in nitrate mass loadings were associated with changes in the typical wind direction from south-westerly to north-westerly where air had passed over the Stuttgart region. Size distribution data shows a dominant accumulation-mode when the measurement site was free from precipitation events. A sharp increase in ultrafine particle number concentration was seen during most days commencing around noon. The apparent growth of these particles is associated with an increase in organic mass loading, suggesting condensational growth. For the most part, with the exception of the high pressure period, the aerosol properties recorded during COPS were comparable to previous studies of continental aerosol properties. Copyright © 2011 Royal Meteorological Society
    Quarterly Journal of the Royal Meteorological Society 01/2011; 137(S1):252 - 266. DOI:10.1002/qj.727 · 3.25 Impact Factor
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