Freezing behavior of single sulfuric acid aerosols suspended in a quadrupole trap

Carleton, Karen L.; Sonnenfroh, David M.; Rawlins, W. T.; Wyslouzil, Barbara E.; Arnold, Stephen

doi:10.1029/97jd00009

Cited by 27 publications

(25 citation statements)

References 37 publications

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“…This is in agreement with bulk and aerosol studies that had difficulty freezing aerosols of composition greater than 35 wt % H 2 SO 4 . 4,10,12,14 In general, it is seen that our data are in good agreement with the historic work. We will now discuss specific transitions that are relevant to atmospheric aerosols.…”

Section: Resultssupporting

confidence: 93%

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

2003

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We have investigated the H 2 SO 4 /H 2 O binary liquid/solid phase diagram using a highly sensitive differential scanning calorimeter (DSC) and infrared spectroscopy of thin films. In particular we have sought to investigate the region from pure ice to sulfuric acid tetrahydrate (SAT), including a detailed look at the sulfuric acid octahydrate (SAO). Our studies have found that there is a unique, repeatable IR spectrum for SAO. Our spectrum is not merely a combination of spectra of ice and sulfuric acid tetrahydrate (SAT), as has been previously suggested could be the case by Zhang et al. (Zhang, R.; Wooldridge, P. J.; Abbatt, J. P. D.; Molina, M. J. J. Phys. Chem. 1993, 97, 7351). From our thermal analysis experiments, we have identified the melting transition of SAO. We report for the first time in the literature the enthalpy of fusion of SAO. We have also determined from our studies using the energies of fusion of ice and the various hydrates of H 2 SO 4 that SAO is a major component of H 2 SO 4 solutions in the range 20-40 wt % when they freeze. Our results indicate that SAO could be present in solid or partially frozen polar stratospheric and upper tropospheric cloud particles. Finally, we make a comment based on our results regarding the stoichiometric composition of SAO.

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Section: Resultssupporting

confidence: 93%

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

2003

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“…This diagram shows that under those conditions the liquid phase cannot exist below the eutectic. However, metastable solutions of H 2 O and H 2 SO 4 , for example, are regularly observed in both the laboratory [e.g., Carleton et al , 1997] and the atmosphere [e.g., Sassen and Dodd , 1988]. The specific question of whether or not it is possible for a salt such as ammonium sulfate to undergo a phase transition from an anhydrous solid to a metastable solution has been a point of contention, with both sides represented in the literature [e.g., Imre et al , 1997; Martin , 1998; Tabazadeh and Toon , 1998].…”

Section: Resultsmentioning

confidence: 99%

Infrared spectroscopic study of the low‐temperature phase behavior of ammonium sulfate

2002

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[1] The low-temperature phase behavior of ammonium sulfate ((NH 4 ) 2 SO 4 ) films has been studied using Fourier transform infrared (FTIR) spectroscopy. While the deliquescence of ammonium sulfate aerosols is well characterized at temperatures above the eutectic of ice and anhydrous ammonium sulfate at 254 K, much less is known about the phase properties at lower temperatures. In the present study, experiments were performed over the temperature range from 166 to 235 K. The apparatus used for this work was a thin-film, high-vacuum apparatus in which the condensed phase is monitored via FTIR spectroscopy and water pressure is monitored with an MKS baratron.Results of experiments performed at low relative humidity (RH) confirm the presence of a ferroelectric phase of ammonium sulfate at temperatures less than 216 ± 8 K. Results of experiments performed as a function of increasing RH demonstrate that a phase transition from crystalline (NH 4 ) 2 SO 4 to a metastable aqueous solution (hereafter referred to as deliquescence) occurs at temperatures below the eutectic. Specifically, at temperatures >203 K we observed deliquescence near 88 ± 8% RH. These results are in satisfactory agreement with extrapolated results from experiments performed at temperatures above the eutectic, as well as theory. In experiments performed at temperatures between 166 and 203 K, we sometimes observed deliquescence and sometimes observed direct deposition of ice from the vapor phase, possibly indicating selective heterogeneous nucleation. Ice nucleation prevents the relative humidity from rising to the level needed for deliquescence, thus explaining the variability in our low-temperature results. Possible implications of this work for cirrus cloud formation are also presented.

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“…While there is field (David et al, 1998;Dye et al, 1992), laboratory (Anthony et al, 1995;Carleton et al, 1997;Koop et al, 1997b), and theoretical evidence that background sulfate aerosols often remain liquid down to very low temperatures, this is not always the case. Results from both the laboratory (Iraci et al, 1995;Koop et al, 1995;Middlebrook et al, 1993;Molina et al, 1993) and the field (Beyerle et al, 2001;Gobbi and Adriani, 1993;Larsen et al, 1995;Nagai et al, 1997;Rivière et al, 2000;Rosen et al, 1993;Sassen et al, 1994) suggest that sulfate aerosols could, even if only in small numbers, exist in a frozen state.…”

Section: European Geosciences Union 2003mentioning

confidence: 99%

Ice condensation on sulfuric acid tetrahydrate: Implications for polar stratospheric ice clouds

et al. 2003

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Abstract. The mechanism of ice nucleation to form Type 2 PSCs is important for controlling the ice particle size and hence the possible dehydration in the polar winter stratosphere. This paper probes heterogeneous ice nucleation on sulfuric acid tetrahydrate (SAT). Laboratory experiments were performed using a thin-film, high-vacuum apparatus in which the condensed phase is monitored via Fourier transform infrared spectroscopy and water pressure is monitored with the combination of an MKS baratron and an ionization gauge. Results show that SAT is an efficient ice nucleus with a critical ice saturation ratio of S * ice = 1.3 to 1.02 over the temperature range 169.8-194.5 K. This corresponds to a necessary supercooling of 0.1-1.3 K below the ice frost point. The laboratory data is used as input for a microphysical/photochemical model to probe the effect that this heterogeneous nucleation mechanism could have on Type 2 PSC formation and stratospheric dehydration. In the model simulations, even a very small number of SAT particles (e.g., 10 −3 cm −3 ) result in ice nucleation on SAT as the dominant mechanism for Type 2 PSC formation. As a result, Type 2 PSC formation is more widespread, leading to larger-scale dehydration. The characteristics of the clouds are controlled by the assumed number of SAT particles present, demonstrating that a proper treatment of SAT is critical for correctly modeling Type 2 PSC formation and stratospheric dehydration.

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Freezing behavior of single sulfuric acid aerosols suspended in a quadrupole trap

Cited by 27 publications

References 37 publications

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

The Search for Sulfuric Acid Octahydrate: Experimental Evidence

Infrared spectroscopic study of the low‐temperature phase behavior of ammonium sulfate

Ice condensation on sulfuric acid tetrahydrate: Implications for polar stratospheric ice clouds

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