scholarly journals Pre-activation of aeosol particles by pore condensation and freezing

2016 ◽  
Author(s):  
Claudia Marcolli
Keyword(s):  
Relative Humidity ◽  
Volcanic Ash ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Ice Crystal ◽  
Pore Width ◽  
Pore Characteristics ◽  
Ice Growth ◽  
Pore Condensation

Abstract. Pre-activation denotes the capability of particles or materials to nucleate ice at lower relative humidities or higher temperatures compared to their intrinsic ice nucleation efficiency after having experienced an ice nucleation event or low temperature before. This review presumes a pore condensation and freezing (PCF) mechanism to analyze studies on pre-activation. Idealized trajectories of air parcels are used to discuss the pore characteristics needed for ice to persist in pores and to induce macroscopic ice-growth out of the pores. The pore width needed to keep pores filled with water decreases with decreasing relative humidity as described by the inverse Kelvin equation. Thus, narrow pores remain filled with ice well below ice saturation. However, the smaller the pore width, the larger the melting and freezing point depressions within the pores. Therefore, pre-activation by PCF is constrained by the melting of ice in narrow pores and the sublimation of ice from wide pores imposing severe restrictions on the temperature and relative humidity range of pre-activation for cylindrical pores. Ice is better protected in ink-bottle-shaped pores with a narrow opening leading to a large cavity. However, whether pre-activation is efficient also depends on the capability of ice to grow macroscopically, i.e. out of the pore. A strong effect of pre-activation is expected for swelling pores, because at low relative humidity (RH) their openings narrow and protect the ice within them against sublimation. At high relative humidities, they open up and the ice can grow to macrosopical size and form an ice crystal. Similarly, ice protected in pockets are perfectly sheltered against sublimation but needs the dissolution of the surrounding matrix to be effective. Pores partially filled with condensable material may also show pre-activation. In this case, complete filling occurs at lower RH than for empty pores and freezing shifts to lower temperatures. Pre-activation experiments confirm that materials susceptible to pre-activation are indeed porous. Pre-activation was observed for clay minerals like illite, kaolinite and montmorillonite with inherent porosity. The largest effect was observed for the swelling clay mineral montmorillonite. Some materials may acquire porosity depending on the formation and processing conditions. Particles of CaCO3, meteoritic material, and volcanic ash showed pre-activation for some samples or in some studies but not in other ones. Quartz and silver iodide were not susceptible to pre-activation. Atmospheric relevance of pre-activation by a PCF mechanism may not be generally given but depend on the atmospheric scenario. Lower-level cloud seeding by pre-activated particles released from high-level clouds crucially depends on the ability of pores to retain ice at the relative humidities and temperatures of the air masses they pass through. Porous particles that are recycled in wave clouds may show pre-activation with subsequent ice growth as soon as ice saturation is exceeded after having passed a first cloud event. Volcanic ash particles and meteoritic material likely influence ice cloud formation by pre-activation. Therefore, pre-activation needs to be considered when ice crystal number densities in clouds exceed the number of ice-nucleating particles measured at the cloud forming temperature.

scholarly journals Pre-activation of aerosol particles by ice preserved in pores

2017 ◽  
Vol 17 (3) ◽  
pp. 1595-1622 ◽  
Author(s):  
Claudia Marcolli
Keyword(s):  
Relative Humidity ◽  
Volcanic Ash ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Ice Crystal ◽  
Pore Width ◽  
Pore Characteristics ◽  
Ice Growth ◽  
Surrounding Matrix

Abstract. Pre-activation denotes the capability of particles or materials to nucleate ice at lower relative humidities or higher temperatures compared to their intrinsic ice nucleation efficiency after having experienced an ice nucleation event or low temperature before. This review presumes that ice preserved in pores is responsible for pre-activation and analyses pre-activation under this presumption. Idealized trajectories of air parcels are used to discuss the pore characteristics needed for ice to persist in pores and to induce macroscopic ice growth out of the pores. The pore width needed to keep pores filled with water decreases with decreasing relative humidity as described by the inverse Kelvin equation. Thus, narrow pores remain filled with ice well below ice saturation. However, the smaller the pore width, the larger the melting and freezing point depressions within the pores. Therefore, pre-activation due to pore ice is constrained by the melting of ice in narrow pores and the sublimation of ice from wide pores imposing restrictions on the temperature and relative humidity range of pre-activation for cylindrical pores. Ice is better protected in ink-bottle-shaped pores with a narrow opening leading to a large cavity. However, whether pre-activation is efficient also depends on the capability of ice to grow macroscopically, i.e. out of the pore. A strong effect of pre-activation is expected for swelling pores, because at low relative humidity (RH) their openings narrow and protect the ice within them against sublimation. At high relative humidities, they open up and the ice can grow to macroscopic size and form an ice crystal. Similarly, ice protected in pockets is perfectly sheltered against sublimation but needs the dissolution of the surrounding matrix to be effective. Pores partially filled with condensable material may also show pre-activation. In this case, complete filling occurs at lower RH than for empty pores and freezing shifts to lower temperatures.Pre-activation experiments confirm that materials susceptible to pre-activation are indeed porous. Pre-activation was observed for clay minerals like illite, kaolinite, and montmorillonite with inherent porosity. The largest effect was observed for the swelling clay mineral montmorillonite. Some materials may acquire porosity, depending on the formation and processing conditions. Particles of CaCO3, meteoritic material, and volcanic ash showed pre-activation for some samples or in some studies but not in other ones. Quartz and silver iodide were not susceptible to pre-activation.Atmospheric relevance of pre-activation by ice preserved in pores may not be generally given but depend on the atmospheric scenario. Lower-level cloud seeding by pre-activated particles released from high-level clouds crucially depends on the ability of pores to retain ice at the relative humidities and temperatures of the air masses they pass through. Porous particles that are recycled in wave clouds may show pre-activation with subsequent ice growth as soon as ice saturation is exceeded after having passed a first cloud event. Volcanic ash particles and meteoritic material likely influence ice cloud formation by pre-activation. Therefore, the possibility of pre-activation should be considered when ice crystal number densities in clouds exceed the number of ice-nucleating particles measured at the cloud forming temperature.

scholarly journals Ice nucleation properties of volcanic ash from Eyjafjallajökull

2011 ◽  
Vol 11 (6) ◽  
pp. 17201-17243 ◽  
Author(s):  
C. R. Hoyle ◽  
V. Pinti ◽  
A. Welti ◽  
B. Zobrist ◽  
C. Marcolli ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Model Calculations ◽  
Airborne Measurements ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Homogeneous Freezing

Abstract. The ice nucleation ability of volcanic ash particles collected close to the Icelandic volcano Eyjafjallajökull during its eruptions in April and May 2010 is investigated experimentally, in the immersion and deposition modes, and applied to atmospheric conditions by comparison with airborne measurements and microphysical model calculations. The number of ash particles which are active as ice nuclei (IN) is strongly temperature dependent, with a very small minority being active in the immersion mode at temperatures of 250–263 K. Average ash particles show only a moderate effect on ice nucleation, by inducing freezing at temperatures between 236 K and 240 K (i.e. approximately 3–4 K higher than temperatures required for homogeneous ice nucleation, measured with the same instrument). By scaling the results to aircraft and lidar measurements of the conditions in the ash plume days down wind of the eruption and by applying a simple microphysical model, it was found that the IN active in the immersion mode in the range 250–263 K generally occurred in atmospheric number densities at the lower end of those required to have an impact on ice cloud formation. However, 3–4 K above the homogeneous freezing point, immersion mode IN number densities a few days down wind of the eruption were sufficiently high to have a moderate influence on ice cloud formation. The efficiency of IN in the deposition mode was found to be poor except at very cold conditions (< 238 K), when they reach an efficiency similar to that of mineral dust with the onset of freezing at 10 % supersaturation with respect to ice, and with the frozen fraction nearing its maximum value at a supersaturation 20 %. In summary, these investigations suggest volcanic ash particles to have only moderate effects on atmospheric ice formation.

scholarly journals Ice nucleation properties of volcanic ash from Eyjafjallajökull

2011 ◽  
Vol 11 (18) ◽  
pp. 9911-9926 ◽  
Author(s):  
C. R. Hoyle ◽  
V. Pinti ◽  
A. Welti ◽  
B. Zobrist ◽  
C. Marcolli ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Model Calculations ◽  
Airborne Measurements ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Homogeneous Freezing

Abstract. The ice nucleation ability of volcanic ash particles collected close to the Icelandic volcano Eyjafjallajökull during its eruptions in April and May 2010 is investigated experimentally, in the immersion and deposition modes, and applied to atmospheric conditions by comparison with airborne measurements and microphysical model calculations. The number of ash particles which are active as ice nuclei (IN) is strongly temperature dependent, with a very small minority being active in the immersion mode at temperatures of 250–263 K. Average ash particles show only a moderate effect on ice nucleation, by inducing freezing at temperatures between 236 K and 240 K (i.e. approximately 3–4 K higher than temperatures required for homogeneous ice nucleation, measured with the same instrument). By scaling the results to aircraft and lidar measurements of the conditions in the ash plume days down wind of the eruption, and by applying a simple microphysical model, it was found that the IN active in the immersion mode in the range 250–263 K generally occurred in atmospheric number densities at the lower end of those required to have an impact on ice cloud formation. However, 3–4 K above the homogeneous freezing point, immersion mode IN number densities a few days down wind of the eruption were sufficiently high to have a moderate influence on ice cloud formation. The efficiency of IN in the deposition mode was found to be poor except at very cold conditions (<238 K), when they reach an efficiency similar to that of mineral dust with the onset of freezing at 10 % supersaturation with respect to ice, and with the frozen fraction nearing its maximum value at a supersaturation 20 %. In summary, these investigations suggest volcanic ash particles to have only moderate effects on atmospheric ice formation.

scholarly journals The Role of Contact Angle and Pore Width on Pore Condensation and Freezing

2019 ◽  
Author(s):  
Robert O. David ◽  
Jonas Fahrni ◽  
Claudia Marcolli ◽  
Fabian Mahrt ◽  
Dominik Brühwiler ◽  
...  
Keyword(s):  
Contact Angle ◽  
Active Sites ◽  
Water Saturation ◽  
Capillary Condensation ◽  
Contact Angles ◽  
Ice Nucleation ◽  
Pore Width ◽  
Kelvin Effect ◽  
Pore Condensation

Abstract. It has recently been shown that pore condensation and freezing (PCF) is a mechanism responsible for ice formation under cirrus cloud conditions. PCF is defined as the condensation of liquid water in narrow capillaries below water saturation due to the Kelvin effect, followed by either heterogeneous or homogeneous nucleation depending on the temperature regime and presence of an ice nucleating active site. By using sol-gel synthesized silica with well-defined pore diameters, morphology and distinct chemical surface-functionalization, the role of the water-silica contact angle and pore width on PCF is investigated. We find that contact angle and pore width play an important role in determining the relative humidity required for capillary condensation as predicted by the Kelvin effect and subsequent ice nucleation at cirrus temperatures. For the pore diameters and contact angles covered in this study, 2.2–9.2 nm and 15–78°, respectively, our results reveal that the contact angle plays an important role in predicting the humidity required for pore filling while the pore diameter determines the ability of pore water to freeze. For T > 235 K and below water saturation, pore diameters and contact angles were not able to predict the freezing ability of the particles suggesting an absence of active sites, thus ice nucleation did not proceed via a PCF mechanism. Rather, the ice nucleating ability of the particles depended solely on chemical functionalization. Therefore, parameterizations for the ice nucleating abilities of particles at cirrus conditions should differ from parameterizations at mixed-phase clouds conditions. Our results support PCF as the atmospherically relevant ice nucleation mechanism below water saturation when porous surfaces are encountered in the troposphere.

scholarly journals On the ice nucleation spectrum

2011 ◽  
Vol 11 (11) ◽  
pp. 29601-29646 ◽  
Author(s):  
D. Barahona
Keyword(s):  
Surface Composition ◽  
Ice Nucleation ◽  
Atmospheric Modeling ◽  
Cloud Formation ◽  
Volume Distribution ◽  
Ice Crystal ◽  
Ice Nuclei ◽  
New Formulation ◽  
Homogeneous Freezing ◽  
Heterogeneous Ice Nucleation

Abstract. This work presents a novel formulation of the ice nucleation spectrum, i.e. the function relating the ice crystal concentration to cloud formation conditions and aerosol properties. The new formulation relies on a statistical view of the ice nucleation process and explicitly accounts for the dependency of the ice crystal concentration on temperature, supersaturation, cooling rate, and particle size, and, in the case of heterogeneous ice nucleation, on the distributions of particle area and surface composition. The new formulation is used to generate ice nucleation parameterizations for the homogeneous freezing of cloud droplets and the heterogeneous deposition ice nucleation on dust and soot ice nuclei. For homogeneous freezing, it was found that by increasing the dispersion in the droplet volume distribution the fraction of supercooled droplets in the population increases. For heterogeneous ice nucleation it was found that ice nucleation on efficient ice nuclei (IN) shows features consistent with the singular hypothesis (characterized by a lack of temporal dependency of the ice nucleation spectrum) whereas less efficient IN tend to display stochastic behavior. Analysis of empirical nucleation spectra suggested that inferring the aerosol heterogeneous ice nucleation properties from measurements of the onset supersaturation and temperature may carry significant error as the variability in ice nucleation properties within the aerosol population is not accounted for. This work provides a simple and rigorous ice nucleation framework were theoretical predictions, laboratory measurements and field campaign data can be reconciled, and that is suitable for application in atmospheric modeling studies.

scholarly journals High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

2008 ◽  
Vol 5 (3) ◽  
pp. 865-873 ◽  
Author(s):  
K. Junge ◽  
B. D. Swanson
Keyword(s):  
High Resolution ◽  
Sea Ice ◽  
Freezing Point ◽  
Free Fall ◽  
Ice Nucleation ◽  
Survival Strategies ◽  
Cloud Formation ◽  
Ice Formation ◽  
Bacterial Cells ◽  
Antarctic Sea Ice

Abstract. Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for ice formation in Arctic clouds (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium – which for artificial seawater was –42.2±0.3°C. Our results suggest that immersion freezing of these marine psychro-active bacteria and viruses would not be important for heterogeneous ice nucleation processes in polar clouds or to the formation of sea ice. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

scholarly journals In vitro uses of biological cryoprotectants

2002 ◽  
Vol 357 (1423) ◽  
pp. 945-951 ◽  
Author(s):  
Peter J. Lillford ◽  
Chris B. Holt
Keyword(s):  
Crystal Growth ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Active Species ◽  
Osmotic Regulation ◽  
Ice Crystal ◽  
Freezing Point Depression ◽  
Commercial Use ◽  
Crystal Growth Inhibition

Ice can be anything from a highly destructive agent in agriculture to a useful building material. Established industries are based on the known rules of physics and chemistry which allow some control of amounts of ice or ice crystal geometry. However, organisms have much more subtle requirements to maintain their delicate internal structure if they are to survive freezing. As a result they have selected specific molecules for freezing–point depression, osmotic regulation, ice nucleation and crystal growth inhibition. All these active species may have potential commercial use once they are identified, understood and produced at economic scales. We examine the progress made so far in extending biological subtlety into commercial processes, and look for prospects for further innovation.

High-Pressure Freezing to Study Structure and Function of the Host Parasite Interface

2000 ◽  
Vol 6 (S2) ◽  
pp. 682-683
Author(s):  
K. Mendgen
Keyword(s):  
High Pressure ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Plant Leaves ◽  
Pressure Application ◽  
Pressure Impact ◽  
And Function ◽  
Host Parasite

The high-pressure freezing instrument exposes a sample to a pressure of 2100 bar, which lowers the freezing point and, as a result, reduces the rate of ice nucleation and ice-crystal growth. The reduced critical cooling rate allows adequate freezing of samples up to 0,3 mm in thickness without using cryoprotectants. Before pressure application, the sample is sandwiched between specimen holders. To optimize heat conductivity and to avoid damage by the high pressure impact, the free space inside the specimen holders and within the sample has to be filled with liquid. This means that plant leaves need to be infiltrated to remove gas from the intercellular space. We have used water, 3-8% methanol in water, 1-hexadecene or heptane as infiltration medium. Subsequently, samples were freeze substituted in unhydrous acetone with 2% Os04 for 24 h at -90°C. Samples were slowly warmed up to 4°C and embedded in Unicryl, or warmed up to room temperature and embedded in epoxide resin.

scholarly journals High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

2007 ◽  
Vol 4 (6) ◽  
pp. 4261-4282 ◽  
Author(s):  
K. Junge ◽  
B. D. Swanson
Keyword(s):  
High Resolution ◽  
Sea Ice ◽  
Freezing Point ◽  
Free Fall ◽  
Ice Nucleation ◽  
Survival Strategies ◽  
Cloud Formation ◽  
The Arctic ◽  
Bacterial Cells ◽  
Antarctic Sea Ice

Abstract. Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for cloud formation in the Arctic (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium – which for artificial seawater was −42.2±0.3°C. Our results indicated that these marine psychro-active bacteria and viruses are not important for heterogeneous ice nucleation processes in sea ice or polar clouds. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

scholarly journals Technical note: Fundamental aspects of ice nucleation via pore condensation and freezing including Laplace pressure and growth into macroscopic ice

2020 ◽  
Vol 20 (5) ◽  
pp. 3209-3230 ◽  
Author(s):  
Claudia Marcolli
Keyword(s):  
Negative Pressure ◽  
Active Sites ◽  
Water Saturation ◽  
Particle Surface ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Ice Crystal ◽  
Spherical Cap ◽  
Pore Opening ◽  
Pore Condensation

Abstract. Pore condensation and freezing (PCF) is an ice nucleation mechanism that explains ice formation at low ice supersaturation. It assumes that liquid water condenses in pores of solid aerosol particles below water saturation, as described by the Kelvin equation, followed by homogeneous ice nucleation when temperatures are below about 235 K or immersion freezing at higher temperatures, in case the pores contain active sites that induce ice nucleation. Porewater is under tension (negative pressure) below water saturation as described by the Young–Laplace equation. This negative pressure affects the ice nucleation rates and the stability of the pore ice. Here, pressure-dependent parameterizations of classical nucleation theory are developed to quantify the increase in homogeneous ice nucleation rates as a function of tension and to assess the critical diameter of pores that is required to accommodate ice at negative pressures. Growth of ice out of the pore into a macroscopic ice crystal requires ice supersaturation. This supersaturation as a function of the pore opening width is derived, assuming that the ice phase first grows as a spherical cap on top of the pore opening before it starts to expand laterally on the particle surface into a macroscopic ice crystal.

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