Electrodynamic balance measurements of thermodynamic, kinetic, and optical aerosol properties inaccessible to bulk methods

Steimer, Sarah S.; Krieger, Ulrich K.; Te, Yiea-Funk; Lienhard, Daniel M.; Huisman, Andrew J.; Luo, B. P.; Ammann, Markus; Peter, Thomas

doi:10.5194/amt-8-2397-2015

Cited by 46 publications

(72 citation statements)

References 39 publications

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“…The diffusion coefficients for this flow tube study are compared with D b,O 3 data inferred from the STXM-NEXAFS experiments 26 as well as D b,H 2 O determined from EDB measurements. 25 The values for all three techniques agree well at higher RH. While the diffusion coefficients determined for water via EDB and those for O 3 inferred from the STXM-NEXAFS measurements are also in agreement at low RH; values derived from G b in this study are consistently larger below 45% RH.…”

supporting

confidence: 68%

“…The shikimic acid bulk concentrations and film thicknesses were deduced from hygroscopicity measurements of levitated particles in an electrodynamic balance (EDB). 25 The calculated second-order rate coefficient is 1.7 Â 10 3 L mol À1 s À1 . Note that using concentration in mol L À1 instead of activity as a metric induces uncertainty in the reported rate coefficient.…”

Section: à3mentioning

confidence: 99%

“…We have previously shown that shikimic acid undergoes humidity-induced glass transition 25 and that changes in humidity are accompanied by changing degradation rates, as assessed by scanning transmission X-ray microscopy (STXM), combined with near edge X-ray absorption fine structure (NEXAFS) spectroscopy. 26 On the long timescales observable in the STXM-NEXAFS experiments, this behaviour was found to be most consistent with classic reaction-diffusion limited kinetics with shikimic acid being well-mixed and O 3 showing a pronounced concentration gradient.…”

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confidence: 99%

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Shikimic acid ozonolysis kinetics of the transition from liquid aqueous solution to highly viscous glass

Steimer

Berkemeier

Gilgen

et al. 2015

Phys. Chem. Chem. Phys.

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Ageing of particulate organic matter affects the composition and properties of atmospheric aerosol particles. Driven by temperature and humidity, the organic fraction can vary its physical state between liquid and amorphous solid, or rarely even crystalline. These transitions can influence the reaction kinetics due to limitations of mass transport in such (semi-) solid states, which in turn may influence the chemical ageing of particles containing such compounds. We have used coated wall flow tube experiments to investigate the reaction kinetics of the ozonolysis of shikimic acid, which serves as a proxy for oxygenated, water-soluble organic matter and can form a glass at room temperature. Particular attention was paid to how the presence of water influences the reaction, since it acts a plasticiser and thereby induces changes in the physical state. We analysed the results by means of a traditional resistor model, which assumes steady-state conditions. The ozonolysis rate of shikimic acid is strongly increased in the presence of water, a fact we attribute to the increased transport of O-3 and shikimic acid through the condensed phase at lower viscosities. The analysis using the resistor model suggests that the system undergoes both surface and bulk reaction. The second-order rate coefficient of the bulk reaction is 3.7 (+1.5/-3.2) x 10(3) L mol(-1) s(-1). At low humidity and long timescales, the resistor model fails to describe the measurements appropriately. The persistent O-3 uptake at very low humidity suggests contribution of a self-reaction of O-3 on the surface

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confidence: 68%

Section: à3mentioning

confidence: 99%

mentioning

confidence: 99%

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Shikimic acid ozonolysis kinetics of the transition from liquid aqueous solution to highly viscous glass

Steimer

Berkemeier

Gilgen

et al. 2015

Phys. Chem. Chem. Phys.

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“…In this study, two Mie resonance spectroscopy-based methods were used: (i) the particle is illuminated using a tunable diode laser (TDL) scanning a range of 765-781 nm. High-resolution Mie resonance spectra (Steimer et al, 2015b) are acquired at 90 • scattering angle for both transverse-electric (TE) and transverse-magnetic (TM) polarization. As the scattering by spherical droplets yields characteristic patterns of resonances, refractive index and radius can be determined simultaneously with an accuracy better than 0.005 in refractive index and a corresponding accuracy in size of ∼ 2×10 −3 µm.…”

Section: Setupmentioning

confidence: 99%

Diffusivity measurements of volatile organics in levitated viscous aerosol particles

et al. 2017

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Abstract. Field measurements indicating that atmospheric secondary organic aerosol (SOA) particles can be present in a highly viscous, glassy state have spurred numerous studies addressing low diffusivities of water in glassy aerosols. The focus of these studies is on kinetic limitations of hygroscopic growth and the plasticizing effect of water. In contrast, much less is known about diffusion limitations of organic molecules and oxidants in viscous matrices. These may affect atmospheric chemistry and gas-particle partitioning of complex mixtures with constituents of different volatility. In this study, we quantify the diffusivity of a volatile organic in a viscous matrix. Evaporation of single particles generated from an aqueous solution of sucrose and small amounts of volatile tetraethylene glycol (PEG-4) is investigated in an electrodynamic balance at controlled relative humidity (RH) and temperature. The evaporative loss of PEG-4 as determined by Mie resonance spectroscopy is used in conjunction with a radially resolved diffusion model to retrieve translational diffusion coefficients of PEG-4. Comparison of the experimentally derived diffusivities with viscosity estimates for the ternary system reveals a breakdown of the Stokes-Einstein relationship, which has often been invoked to infer diffusivity from viscosity. The evaporation of PEG-4 shows pronounced RH and temperature dependencies and is severely depressed for RH 30 %, corresponding to diffusivities < 10 −14 cm 2 s −1 at temperatures < 15 • C. The temperature dependence is strong, suggesting a diffusion activation energy of about 300 kJ mol −1 . We conclude that atmospheric volatile organic compounds can be subject to severe diffusion limitations in viscous organic aerosol particles. This may enable an important long-range transport mechanism for organic material, including pollutant molecules such as polycyclic aromatic hydrocarbons (PAHs).

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“…Only a few studies have measured the diffusion of water in glassy model systems for atmospherically relevant relative humidities at room temperature and even fewer studies at lower temperatures (Zobrist et al, 2011;Tong et al, 2011;Bones et al, 2012;Price et al, 2014;Lienhard et al, 2014;Steimer et al, 2015). Estimations of the influence of slow water diffusivity on homogeneous and heterogeneous ice nucleation as well as on multi-phase chemistry have been extrapolated from sucrose properties as a model system towards different types of SOA (Berkemeier et al, 2014;Arangio et al, 2015).…”

mentioning

confidence: 99%

Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation?

Lienhard

Huisman

Krieger³

et al. 2015

Atmos. Chem. Phys.

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Abstract. New measurements of water diffusion in secondary organic aerosol (SOA) material produced by oxidation of α-pinene and in a number of organic/inorganic model mixtures (3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), levoglucosan, levoglucosan/NH 4 HSO 4 , raffinose) are presented. These indicate that water diffusion coefficients are determined by several properties of the aerosol substance and cannot be inferred from the glass transition temperature or bouncing properties. Our results suggest that water diffusion in SOA particles is faster than often assumed and imposes no significant kinetic limitation on water uptake and release at temperatures above 220 K. The fast diffusion of water suggests that heterogeneous ice nucleation on a glassy core is very unlikely in these systems. At temperatures below 220 K, model simulations of SOA particles suggest that heterogeneous ice nucleation may occur in the immersion mode on glassy cores which remain embedded in a liquid shell when experiencing fast updraft velocities. The particles absorb significant quantities of water during these updrafts which plasticize their outer layers such that these layers equilibrate readily with the gas phase humidity before the homogeneous ice nucleation threshold is reached. Glass formation is thus unlikely to restrict homogeneous ice nucleation. Only under most extreme conditions near the very high tropical tropopause may the homogeneous ice nucleation rate coefficient be reduced as a consequence of slow condensed-phase water diffusion. Since the differences between the behavior limited or non limited by diffusion are small even at the very high tropical tropopause, condensed-phase water diffusivity is unlikely to have significant consequences on the direct climatic effects of SOA particles under tropospheric conditions.

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Electrodynamic balance measurements of thermodynamic, kinetic, and optical aerosol properties inaccessible to bulk methods

Cited by 46 publications

References 39 publications

Shikimic acid ozonolysis kinetics of the transition from liquid aqueous solution to highly viscous glass

Shikimic acid ozonolysis kinetics of the transition from liquid aqueous solution to highly viscous glass

Diffusivity measurements of volatile organics in levitated viscous aerosol particles

Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation?

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