Exploring an approximation for the homogeneous freezing temperature of water  droplets

Kuan-Ting, O; Wood, Robert

doi:10.5194/acp-16-7239-2016

Cited by 10 publications

(6 citation statements)

References 48 publications

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“…Restricting the freezing curve analysis to the 5 %-95 % frozen droplet fraction, as is now being done by some groups to exclude anomalously early and late freezing droplets, is not recommended. The ice activity of individual particles is very much a diverse spectrum, resulting in some droplets in a freezing array containing more rare ice-active INPs that induce freezing at warmer temperatures (Augustin-Bauditz et al, 2016;Conen et al, 2011;O'Sullivan et al, 2015;Petters and Wright, 2015;Pummer et al, 2012Pummer et al, , 2015. This can occur even in experiments on "pure" single-particle-type samples such as Snomax bacterial and illite NX mineral particles (Beydoun et al, 2016(Beydoun et al, , 2017.…”

Section: Recommendations For Droplet Freezing Methods and Analysis Promentioning

confidence: 99%

“…DFTs are utilized for both homogeneous and heterogeneous ice nucleation experiments (Hiranuma et al, 2015;Murray et al, 2010Murray et al, , 2012Vali and Stansbury, 1966;Wilson et al, 2015;Zobrist et al, 2008). Homogeneous freezing can sometimes present a challenge for DFTs as it is difficult to avoid interference from unintended heterogeneous freezing (Hader et al, 2014;O'Sullivan et al, 2015;Whale et al, 2015). There are a number of variables within DFT setups that can influence the apparent homogeneous freezing temperature of pure water droplets that determines the background temperature spectrum and sets the lower temperature limit for assessing heterogeneous ice nucleation.…”

Section: Introductionmentioning

confidence: 99%

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Cleaning up our water: reducing interferences from nonhomogeneous freezing of “pure” water in droplet freezing assays of ice-nucleating particles

et al. 2018

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Abstract. Droplet freezing techniques (DFTs) have been used for half a century to measure the concentration of ice-nucleating particles (INPs) in the atmosphere and determine their freezing properties to understand the effects of INPs on mixed-phase clouds. The ice nucleation community has recently adopted droplet freezing assays as a commonplace experimental approach. These droplet freezing experiments are often limited by contamination that causes nonhomogeneous freezing of the “pure” water used to generate the droplets in the heterogeneous freezing temperature regime that is being measured. Interference from the early freezing of water is often overlooked and not fully reported, or measurements are restricted to analyzing the more ice-active INPs that freeze well above the temperature of the background water. However, this avoidance is not viable for analyzing the freezing behavior of less active INPs in the atmosphere that still have potentially important effects on cold-cloud microphysics. In this work we review a number of recent droplet freezing techniques that show great promise in reducing these interferences, and we report our own extensive series of measurements using similar methodologies. By characterizing the performance of different substrates on which the droplets are placed and of different pure water generation techniques, we recommend best practices to reduce these interferences. We tested different substrates, water sources, droplet matrixes, and droplet sizes to provide deeper insight into what methodologies are best suited for DFTs. Approaches for analyzing droplet freezing temperature spectra and accounting and correcting for the background “pure” water control spectrum are also presented. Finally, we propose experimental and data analysis procedures for future homogeneous and heterogeneous ice nucleation studies to promote a more uniform and reliable methodology that facilitates the ready intercomparison of ice-nucleating particles measured by DFTs.

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Section: Recommendations For Droplet Freezing Methods and Analysis Promentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cleaning up our water: reducing interferences from nonhomogeneous freezing of “pure” water in droplet freezing assays of ice-nucleating particles

et al. 2018

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“…The use of Piko PCR trays allows for a range of sample volumes between 5 -60 µL to be measured on FINC. Theoretically, freezing rates of water droplets are dependent on the volume of the droplet; smaller droplets freeze at lower temperatures (O and Wood, 2016). Classical nucleation theory approximates interfacial tension between ice and water, activation energy of the phase transfer, and size of clusters and embryos (Ickes et al, 2015 µL, respectively, across one to five replicates (Table S2; Fig.…”

Section: Non-homogeneous Freezing In Fincmentioning

confidence: 99%

Development of the drop Freezing Ice Nuclei Counter (FINC), intercomparison of droplet freezing techniques, and use of soluble lignin as an atmospheric ice nucleation standard

Miller¹,

Brennan²,

Mignani³

et al. 2020

Preprint

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Abstract. Aerosol-cloud interactions, including the ice nucleation of supercooled liquid water droplets caused by ice nucleating particles (INPs) and macromolecules (INMs), are a source of uncertainty in predicting future climate. Because of INPs' and INMs' spatial and temporal heterogeneity in source, number, and composition, predicting their concentration and distribution is a challenge, requiring apt analytical instrumentation. Here, we present the development of our drop Freezing Ice Nucleation Counter (FINC), a droplet freezing technique (DFT), for the quantification of INP and INM concentrations in the immersion freezing mode. FINC's design builds upon previous DFTs and uses an ethanol bath to cool sample aliquots while detecting freezing using a camera. Specifically, FINC uses 288 sample wells of 5–60 µL volume, has a limit of detection of −25.37 &pm; 0.15 ˚C with 5 µL, and has an instrument temperature uncertainty of &pm; 0.5 ˚C. We further conducted freezing control experiments to quantify the non-homogeneous behavior of our developed DFT, including the consideration of eight different sources of contamination. As part of the validation of FINC, an intercomparison campaign was conducted using an NX-illite suspension and an ambient aerosol sample with two other drop-freezing instruments: ETH's DRoplet Ice Nuclei Counter Zurich (DRINCZ) and University of Basel’s LED-based ice nucleation detection apparatus (LINDA). We also tabulated an exhaustive list of peer-reviewed DFTs, to which we added our characterized and validated FINC. In addition, we propose herein the use of a water-soluble biopolymer, lignin, as a suitable ice nucleating standard. An ideal INM standard should be inexpensive, accessible, reproducible, unaffected by sample preparation, and consistent across techniques. First, we show that commercial lignin has a consistent ice nucleating activity across product batches. Second, we demonstrate that aqueous lignin solutions exhibit good solution stability over time. Third, we compare its freezing temperature across different drop-freezing instruments, including on DRINCZ, LINDA, and on the Weizmann Institute's Supercooled Droplets Observation on a Microarray (WISDOM) and determine an empirical fit parameter for future drop freezing validations. With these findings, we aim to show that lignin can be used as a good immersion freezing standard in future technique intercomparisons in the field of atmospheric ice nucleation.

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“…Thus we can approximate that S c,LL ≈ S c,0 . Unfortunately equating S c,IL to the configurational entropy of bulk ice (which can be deduced from geometrical arguments; Pauling, 1935) would violate the requirement that D → 0 at thermodynamic equilibrium. To estimate S c,IL we assume instead that water molecules in the IL regions should be displaced from their equilibrium position (essentially "diffusing" into the LL regions) to be incorporated into the ice lattice.…”

Section: Diffusion Within the Particle-liquid Interfacementioning

confidence: 99%

On the thermodynamic and kinetic aspects of immersion ice nucleation

Barahona

2018

Atmos. Chem. Phys.

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Abstract. Heterogeneous ice nucleation initiated by particles immersed within droplets is likely the main pathway of ice formation in the atmosphere. Theoretical models commonly used to describe this process assume that it mimics ice formation from the vapor, neglecting interactions unique to the liquid phase. This work introduces a new approach that accounts for such interactions by linking the ability of particles to promote ice formation to the modification of the properties of water near the particle–liquid interface. It is shown that the same mechanism that lowers the thermodynamic barrier for ice nucleation also tends to decrease the mobility of water molecules, hence the ice–liquid interfacial flux. Heterogeneous ice nucleation in the liquid phase is thus determined by the competition between thermodynamic and kinetic constraints to the formation and propagation of ice. At the limit, ice nucleation may be mediated by kinetic factors instead of the nucleation work. This new ice nucleation regime is termed spinodal ice nucleation. The comparison of predicted nucleation rates against published data suggests that some materials of atmospheric relevance may nucleate ice in this regime.

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Exploring an approximation for the homogeneous freezing temperature of water droplets

Cited by 10 publications

References 48 publications

Cleaning up our water: reducing interferences from nonhomogeneous freezing of “pure” water in droplet freezing assays of ice-nucleating particles

Cleaning up our water: reducing interferences from nonhomogeneous freezing of “pure” water in droplet freezing assays of ice-nucleating particles

Development of the drop Freezing Ice Nuclei Counter (FINC), intercomparison of droplet freezing techniques, and use of soluble lignin as an atmospheric ice nucleation standard

On the thermodynamic and kinetic aspects of immersion ice nucleation

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