Temperature‐ and Humidity‐Dependent Phase States of Secondary Organic Aerosols

Petters, Sarah Suda; Kreidenweis, Sonia M.; Grieshop, Andrew P.; Ziemann, Paul J.; Petters, M. D.

doi:10.1029/2018gl080563

Cited by 70 publications

(113 citation statements)

References 74 publications

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“…Then, the T-dependence of viscosity is calculated using the Vogel-Tammann-Fulcher equation (Angell, 1991;Rothfuss and Petters, 2017;DeRieux et al, 2018;Li and Shiraiwa, 2018). Figure 1 shows the T-and RH-dependent viscosity of SOA particles with T g,org of (a) 240 K, (b) 270 K, and (c) 300 K. We chose these three T g,org values to represent different phase states of liquid, semi-solid, and glassy states, respectively, at T of 298 K under dry conditions and these values are within the range recently reported for monoterpene-derived SOA (Petters et al, 2019). The decrease of T leads to increase of viscosity, while the increase of RH leads to decrease of viscosity due to the plasticizing effect of water (Koop et al, 2011).…”

Section: Methodsmentioning

confidence: 69%

Timescales of Secondary Organic Aerosols to Reach Equilibrium at Various Temperatures and Relative Humidities

Liu¹,

Shiraiwa²

2019

Preprint

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<p><strong>Abstract.</strong> Secondary organic aerosols (SOA) account for a substantial fraction of air particulate matter and SOA formation is often modeled assuming rapid establishment of gas-particle equilibrium. Here, we estimate the characteristic timescale for SOA to achieve gas&#8722;particle equilibrium under a wide range of temperatures and relative humidities using a state-of-the-art kinetic flux model. Equilibration timescales were calculated by varying particle phase state, size, mass loadings, and volatility of organic compounds. Model simulations suggest that the equilibration timescale for semi-volatile compounds is on the order of seconds or minutes for most conditions in the planetary boundary layer, but it can be longer than one hour if particles adopt glassy or amorphous solid states with high glass transition temperature at low relative humidity. In the free troposphere with lower temperatures it can be longer than hours or days even at moderate or relatively high RH due to kinetic limitations of bulk diffusion in highly viscous particles. The timescale of partitioning of low-volatile compounds is shorter compared to semi-volatile compounds, as it is largely determined by condensation sink due to very slow re-evaporation. These results provide critical insights into thermodynamic or kinetic treatments of SOA partitioning for accurate predictions of gas- and particle-phase concentrations of semi-volatile compounds in regional and global chemical transport models.</p>

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Section: Methodsmentioning

confidence: 69%

Timescales of Secondary Organic Aerosols to Reach Equilibrium at Various Temperatures and Relative Humidities

Liu¹,

Shiraiwa²

2019

Preprint

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“…Future simulations on equilibration timescales should consider the effects of the immiscibility Liu et al, 2013) and the phase separation (Shiraiwa et al, 2013b;Pye et al, 2017;Fowler et al, 2018) as well as composition-dependent bulk diffusivity (O'Meara et al, 2016) and the evolution of the particle phase due to reactive uptake and condensed-phase chemistry (Hosny et al, 2016). Incorporation of the particle-phase formation of oligomers and other multifunctional high molar mass compounds can lead to a reduced bulk diffusivity (Pfrang et al, 2011;Hosny et al, 2016), which may prolong the equilibration timescales. Decomposition of highly oxidized molecules (e.g., organic hydroperoxides) in water may also affect gas-particle partitioning (Tong et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Timescales of secondary organic aerosols to reach equilibrium at various temperatures and relative humidities

Liu

Shiraiwa

2019

Atmos. Chem. Phys.

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Secondary organic aerosols (SOA) account for a substantial fraction of air particulate matter, and SOA formation is often modeled assuming rapid establishment of gas-particle equilibrium. Here, we estimate the characteristic timescale for SOA to achieve gas-particle equilibrium under a wide range of temperatures and relative humidities using a state-of-the-art kinetic flux model. Equilibration timescales were calculated by varying particle phase state, size, mass loadings, and volatility of organic compounds in open and closed systems. Model simulations suggest that the equilibration timescale for semi-volatile compounds is on the order of seconds or minutes for most conditions in the planetary boundary layer, but it can be longer than 1 h if particles adopt glassy or amorphous solid states with high glass transition temperatures at low relative humidity. In the free troposphere with lower temperatures, it can be longer than hours or days, even at moderate or relatively high relative humidities due to kinetic limitations of bulk diffusion in highly viscous particles. The timescale of partitioning of low-volatile compounds into highly viscous particles is shorter compared to semi-volatile compounds in the closed system, as it is largely determined by condensation sink due to very slow re-evaporation with relatively quick establishment of local equilibrium between the gas phase and the near-surface bulk. The dependence of equilibration timescales on both volatility and bulk diffusivity provides critical insights into thermodynamic or kinetic treatments of SOA partitioning for accurate predictions of gas-and particle-phase concentrations of semi-volatile compounds in regional and global chemical transport models.

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“…Saha et al (2017) applied an evaporation kinetic model (Lee et al, 2011) based on the VBS approach to extract the C * distributions, and the effects of enthalpy of vaporization (△Hvap) and accommodation coefficient (α) are considered, resulting in the estimated Tg,org of 313 K. This study retrieved α ~0.5, which is consistent with recent observations (Krechmer et al, 2017;Liu et al, 2019). In summary, Tg,org during the SOAS campaign span the range of 313 -330 K. et al, 2019), which may be due to substantial formation of organosulfates and other oligomers (Lin et al, 2012;Hu et al, 2015;Riva et al, 2019).The predicted Tg,org of IEPOX-SOA is higher than previously reported Tg,org of 263 -293 K for monoterpenederived (α-pinene, △ 3 -carene, myrcene, limonene and ocimene) SOA (Petters et al, 2019).…”

Section: Southern Oxidant and Aerosol Study (Soas)mentioning

confidence: 76%

“…The predicted ambient viscosity is compared with the experimental observed viscosity of SOA formed from isoprene (Song et al, 2015), α-pinene (Abramson et al, 2013;Renbaum-Wolff et al, 2013;Kidd et al, 2014;Pajunoja et al, 2014;Zhang et al, 2015;Grayson et al, 2016;Petters et al, 2019), toluene (Song et al, 2016a) and diesel fuel (Song et al, 2019). The majority of experimental values are well bounded by the predicted viscosity of OOA, represented by the pink shaded area.…”

Section: Tgorg At 11 Global Sitesmentioning

confidence: 96%

“…Predicted viscosity of (a) HOA, COA and BBOA and (b) LO-OOA, MO-OOA, IEPOX SOA and Isoprene OA in different locations at 298 K as a function of RH. Experimentally measured viscosity of laboratory-generated SOA formed from isoprene (Song et al, 2015), α-pinene (Abramson et al, 2013;Renbaum-Wolff et al, 2013;Kidd et al, 2014;Pajunoja et al, 2014;Bateman et al, 2015;Zhang et al, 2015;Grayson et al, 2016;Petters et al, 2019), toluene (Song et al, 2016), and diesel fuel (Song et al, 2019) are also shown. Predicted viscosity of IEPOX-derived OS mixtures (solid blue line) is from Riva et al (2019).…”

Section: Author Contributionmentioning

confidence: 97%

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Predictions of the glass transition temperature and viscosity of organic aerosols by volatility distributions

Liu¹,

Day²,

Stark³

et al. 2020

Preprint

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Abstract. Volatility and viscosity are important properties of organic aerosols (OA), affecting aerosol processes such as formation, evolution and partitioning of OA. Volatility distributions of ambient OA particles have often been measured, while viscosity measurements are scarce. We have previously developed a method to estimate glass transition temperature (Tg) of an organic compound containing carbon, hydrogen, and oxygen. Based on analysis of over 2300 organic compounds including oxygenated organic compounds as well as nitrogen- and sulfur-containing organic compounds, we extend this method to include nitrogen- and sulfur-containing compounds based on elemental composition. In addition, parameterizations are developed to predict Tg as a function of volatility and the atomic oxygen-to-carbon ratio based on a negative correlation between Tg and volatility. The prediction method of Tg and viscosity is applied to ambient observations of volatility distributions at eleven field sites. The predicted Tg varies mainly from 290 K to 339 K and the predicted viscosities are consistent with the results of ambient particle phase state measurements in the southeastern US and the Amazonian rain forest. Reducing the uncertainties in measured volatility distributions would be helpful to improve predictions of viscosity especially at low relative humidity. We also predict the Tg of OA components identified via positive matrix factorization of aerosol mass spectrometer data. The predicted viscosity of oxidized OA is consistent with previously reported viscosity of SOA derived from α-pinene, toluene, isoprene epoxydiol (IEPOX), and of diesel fuel. Comparison of the predicted viscosity based on the observed volatility distributions with the viscosity simulated by a chemical transport model implies that missing low volatility compounds in a global model can lead to underestimation of OA viscosity at some sites. The relation between volatility and viscosity can be applied in the molecular corridor or volatility basis set approaches to improve OA simulations in chemical transport models by consideration of effects of particle viscosity in OA formation and evolution.

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Temperature‐ and Humidity‐Dependent Phase States of Secondary Organic Aerosols

Cited by 70 publications

References 74 publications

Timescales of Secondary Organic Aerosols to Reach Equilibrium at Various Temperatures and Relative Humidities

Timescales of Secondary Organic Aerosols to Reach Equilibrium at Various Temperatures and Relative Humidities

Timescales of secondary organic aerosols to reach equilibrium at various temperatures and relative humidities

Predictions of the glass transition temperature and viscosity of organic aerosols by volatility distributions

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