A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles

Zardini, Alessandro; Sjögren, S.; Marcolli, Claudia; Krieger, Ulrich K.; Gysel, M.; Weingärtner, E.; Baltensperger, Urs; Peter, Thomas

doi:10.5194/acp-8-5589-2008

Cited by 158 publications

(162 citation statements)

References 52 publications

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“…1) shows a sharp transition at the deliquescence point of AS, indicating that the amount of AS dissolved in the organic-rich phase is minuscule and does not lead to a noticeable water uptake prior to deliquescence. Note that this behavior can be quite different for systems containing highly oxidized organic compounds, such as citric acid, 67 and will also depend on the ratio of organic/inorganic portions.…”

Section: Discussionmentioning

confidence: 99%

Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology

Shiraiwa

Zuend

Bertram

et al. 2013

Phys. Chem. Chem. Phys.

246

268

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Atmospheric aerosols, comprising organic compounds and inorganic salts, play a key role in air quality and climate. Mounting evidence exists that these particles frequently exhibit phase separation into predominantly organic and aqueous electrolyte-rich phases. As well, the presence of amorphous semi-solid or glassy particle phases has been established. Using the canonical system of ammonium sulfate mixed with organics from the ozone oxidation of a-pinene, we illustrate theoretically the interplay of physical state, non-ideality, and particle morphology affecting aerosol mass concentration and the characteristic timescale of gas-particle mass transfer. Phase separation can significantly affect overall particle mass and chemical composition. Semi-solid or glassy phases can kinetically inhibit the partitioning of semivolatile components and hygroscopic growth, in contrast to the traditional assumption that organic compounds exist in quasi-instantaneous gas-particle equilibrium. These effects have significant implications for the interpretation of laboratory data and the development of improved atmospheric air quality and climate models.

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Section: Discussionmentioning

confidence: 99%

Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology

Shiraiwa

Zuend

Bertram

et al. 2013

Phys. Chem. Chem. Phys.

246

268

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“…These ranges are at the high end or above ERH observed for other dicarboxylic acid/AS/H 2 O systems: e.g. Parsons et al (2004) and Zardini et al (2008) report ERH for malonic acid/AS, glutaric acid/AS, and citric acid/AS particles consistently below 40 %. A possible explanation for the high ERH values observed in this study might be an increase of the ion activity coefficients due to the energetically disadvantageous interactions between the ions of AS and the C6 and C7 dicarboxylic acids, enhancing the probability for the formation of stable AS crystal nuclei at higher RH as compared to mixtures with the more hydrophilic malonic (C3 dicarboxylic acid), glutaric (C5 dicarboxylic acid) and citric acids.…”

Section: Phase Diagrams Of C6/as/h 2 O and C7/as/h 2 O Systemsmentioning

confidence: 99%

Liquid-liquid phase separation and morphology of internally mixed dicarboxylic acids/ammonium sulfate/water particles

et al. 2012

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Abstract. Knowledge of the physical state and morphology of internally mixed organic/inorganic aerosol particles is still largely uncertain. To obtain more detailed information on liquid-liquid phase separation (LLPS) and morphology of the particles, we investigated complex mixtures of atmospherically relevant dicarboxylic acids containing 5, 6, and 7 carbon atoms (C5, C6 and C7) having oxygen-to-carbon atomic ratios (O:C) of 0.80, 0.67, and 0.57, respectively, mixed with ammonium sulfate (AS). With micrometer-sized particles of C5/AS/H 2 O, C6/AS/H 2 O and C7/AS/H 2 O as model systems deposited on a hydrophobically coated substrate, laboratory experiments were conducted for various organic-to-inorganic dry mass ratios (OIR) using optical microscopy and Raman spectroscopy. When exposed to cycles of relative humidity (RH), each system showed significantly different phase transitions. While the C5/AS/H 2 O particles showed no LLPS with OIR = 2:1, 1:1 and 1:4 down to 20 % RH, the C6/AS/H 2 O and C7/AS/H 2 O particles exhibit LLPS upon drying at RH 50 to 85 % and ∼90 %, respectively, via spinodal decomposition, growth of a second phase from the particle surface or nucleation-and-growth mechanisms depending on the OIR. This suggests that LLPS commonly occurs within the range of O:C < 0.7 in tropospheric organic/inorganic aerosols. To support the comparison and interpretation of the experimentally observed phase transitions, thermodynamic equilibrium calculations were performed with the AIOMFAC model. For the C7/AS/H 2 O and C6/AS/H 2 O systems, the calculated phase diagrams agree well with the observations while for the C5/AS/H 2 O system LLPS is predicted by the model at RH below 60 % and higher AS concentration, but was not observed in the experiments.Both core-shell structures and partially engulfed structures were observed for the investigated particles, suggesting that such morphologies might also exist in tropospheric aerosols.

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“…For a hygroscopicity tandem differential mobility analyser (HTDMA), which has a typical residence time of 20-25 s (Zardini et al, 2008) and e s increase of ∼ 90 % from an initial value < 10 %, Figs. 3 and 5 show that equilibration is attained even when sampling relatively large (∼ 1 × 10 −5 m) particles containing components of relatively low diffusivity (self-diffusion coefficients ∼ 1 × 10 −25 m 2 s −1 ).…”

Section: Discussionmentioning

confidence: 99%

The rate of equilibration of viscous aerosol particles

2016

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Abstract. The proximity of atmospheric aerosol particles to equilibrium with their surrounding condensable vapours can substantially impact their transformations, fate and impacts and is the subject of vibrant research activity. In this study we first compare equilibration timescales estimated by three different models for diffusion through aerosol particles to assess any sensitivity to choice of model framework. Equilibration times for diffusion coefficients with varying dependencies on composition are compared for the first time. We show that even under large changes in the saturation ratio of a semivolatile component (e s ) of 1-90 % predicted equilibration timescales are in agreement, including when diffusion coefficients vary with composition. For condensing water and a diffusion coefficient dependent on composition, a plasticising effect is observed, leading to a decreased estimated equilibration time with increasing final e s . Above 60 % final e s maximum equilibration times of around 1 s are estimated for comparatively large particles (10 µm) containing a relatively low diffusivity component (1 × 10 −25 m 2 s −1 in pure form). This, as well as other results here, questions whether particlephase diffusion through water-soluble particles can limit hygroscopic growth in the ambient atmosphere. In the second part of this study, we explore sensitivities associated with the use of particle radius measurements to infer diffusion coefficient dependencies on composition using a diffusion model. Given quantified similarities between models used in this study, our results confirm considerations that must be taken into account when designing such experiments. Although quantitative agreement of equilibration timescales between models is found, further work is necessary to determine their suitability for assessing atmospheric impacts, such as their inclusion in polydisperse aerosol simulations.

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A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles

Cited by 158 publications

References 52 publications

Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology

Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology

Liquid-liquid phase separation and morphology of internally mixed dicarboxylic acids/ammonium sulfate/water particles

The rate of equilibration of viscous aerosol particles

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