scholarly journals Homogeneous ice nucleation in aqueous ammonium sulfate aerosol particles

2001 ◽  
Vol 106 (D1) ◽  
pp. 1215-1226 ◽  
Author(s):  
J. Holly Chelf ◽  
Scot T. Martin
Keyword(s):  
Ammonium Sulfate ◽  
Aerosol Particles ◽  
Ice Nucleation ◽  
Sulfate Aerosol

scholarly journals Ice nucleation ability of ammonium sulfate aerosol particles internally mixed with secondary organics

2021 ◽  
Vol 21 (13) ◽  
pp. 10779-10798
Author(s):  
Barbara Bertozzi ◽  
Robert Wagner ◽  
Junwei Song ◽  
Kristina Höhler ◽  
Joschka Pfeifer ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ammonium Sulfate ◽  
Active Sites ◽  
Aerosol Particles ◽  
Particle Morphology ◽  
Organic Coating ◽  
Ice Nucleation ◽  
Cloud Models ◽  
Organic Particles ◽  
The Impact

Abstract. The abundance of aerosol particles and their ability to catalyze ice nucleation are key parameters to correctly understand and describe the aerosol indirect effect on the climate. Cirrus clouds strongly influence the Earth's radiative budget, but their effect is highly sensitive to their formation mechanism, which is still poorly understood. Sulfate and organics are among the most abundant aerosol components in the troposphere and have also been found in cirrus ice crystal residuals. Most of the studies on ice nucleation at cirrus cloud conditions looked at either purely inorganic or purely organic particles. However, particles in the atmosphere are mostly found as internal mixtures, the ice nucleation ability of which is not yet fully characterized. In this study, we investigated the ice nucleation ability of internally mixed particles composed of crystalline ammonium sulfate (AS) and secondary organic material (SOM) at temperatures between −50 and −65 ∘C. The SOM was generated from the ozonolysis of α-pinene. The experiments were conducted in a large cloud chamber, which also allowed us to simulate various aging processes that the particles may experience during their transport in the atmosphere, like cloud cycling and redistribution of the organic matter. We found that the ice nucleation ability of the mixed AS / SOM particles is strongly dependent on the particle morphology. Small organic mass fractions of 5 wt %–8 wt % condensed on the surface of AS crystals are sufficient to completely suppress the ice nucleation ability of the inorganic component, suggesting that the organic coating is evenly distributed on the surface of the seed particles. In this case, the ice nucleation onset increased from a saturation ratio with respect to ice Sice∼1.30 for the pure AS crystals to ≥1.45 for the SOM-coated AS crystals. However, if such SOM-coated AS crystals are subjected to the mentioned aging processes, they show an improved ice nucleation ability with the ice nucleation onset at Sice∼1.35. We suggest that the aging processes change the particle morphology. The organic matter might redistribute on the surface to form a partially engulfed structure, where the ice-nucleation-active sites of the AS crystals are no longer completely masked by the organic coating, or the morphology of the organic coating layer might transform from a compact to a porous structure. Our results underline the complexity in representing the ice nucleation ability of internally mixed particles in cloud models. They also demonstrate the need to further investigate the impact of atmospheric aging and cloud processing on the morphology and related ice nucleation ability of internally mixed particles.

scholarly journals Ice nucleation ability of Ammonium Sulfate aerosol particles internally mixed with Secondary Organics

2021 ◽  
Author(s):  
Barbara Bertozzi ◽  
Robert Wagner ◽  
Kristina Höhler ◽  
Joschka Pfeifer ◽  
Harald Saathoff ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ammonium Sulfate ◽  
Active Sites ◽  
Aerosol Particles ◽  
Particle Morphology ◽  
Organic Coating ◽  
Ice Nucleation ◽  
Shell Morphology ◽  
Cloud Models ◽  
The Impact

Abstract. The abundance of aerosol particles and their ability to catalyze ice nucleation are key parameters to correctly understand and describe the aerosol indirect effect on the climate. Cirrus clouds strongly influence the Earth's radiative budget, but their effect is highly sensitive to their formation mechanism, which is still poorly understood. Sulfate and organics are among the most abundant aerosol components in the troposphere and have also been found in cirrus ice crystal residuals. Most of the studies on ice nucleation at cirrus cloud conditions looked at either purely inorganic or purely organic particles. However, particles in the atmosphere are mostly found as internal mixtures, the ice nucleation ability of which is not yet fully characterized. In this study, we investigated the ice nucleation ability of internally mixed particles composed of crystalline ammonium sulfate (AS) and secondary organic material (SOM) at temperatures between −50 °C and −65 °C. The SOM was generated from the ozonolysis of α-pinene. The experiments were conducted in a large cloud chamber, which also allowed to simulate various aging processes that the particles may experience during their transport in the atmosphere, like cloud cycling and redistribution of the organic matter. We found that the ice nucleation ability of the mixed AS/SOM particles is strongly dependent on the particle morphology. If the organic matter is evenly distributed around the AS crystals in a core-shell morphology, small organic mass fractions of 5–8 wt% are sufficient to completely mask the heterogeneous ice nucleation ability of the inorganic core. In this case, the ice nucleation onset increased from a saturation ratio with respect to ice Sice ~ 1.30 for the pure AS crystals to ≥ 1.45 for the SOM-coated AS crystals. However, if such SOM-coated AS crystals are subjected to the mentioned aging processes, they show an improved ice nucleation ability with the ice nucleation onset at Sice ~ 1.35. We suggest that the aging processes change the particle morphology. The organic matter might redistribute on the surface to form a partially engulfed structure, where the ice-active sites of the AS crystals are no longer completely masked by the organic coating, or the morphology of the organic coating layer might transform from a compact to a porous structure. Our results underline the complexity to represent the ice nucleation ability of internally mixed particles in cloud models. They also demonstrate the need to further investigate the impact of atmospheric aging and cloud processing on the morphology and related ice nucleation ability of internally mixed particles.

scholarly journals A novel tandem differential mobility analyzer with organic vapor treatment of aerosol particles

2001 ◽  
Vol 1 (1) ◽  
pp. 51-60 ◽  
Author(s):  
J. Joutsensaari ◽  
P. Vaattovaara ◽  
M. Vesterinen ◽  
K. Hämeri ◽  
A. Laaksonen
Keyword(s):  
Water Vapor ◽  
Sodium Chloride ◽  
Citric Acid ◽  
Ammonium Sulfate ◽  
Adipic Acid ◽  
Aerosol Particles ◽  
Ethanol Vapor ◽  
Differential Mobility Analyzer ◽  
Differential Mobility ◽  
Organic Vapor

Abstract. A novel method to characterize the organic composition of aerosol particles has been developed. The method is based on organic vapor interaction with aerosol particles and it has been named an Organic Tandem Differential Mobility Analyzer (OTDMA). The OTDMA method has been tested for inorganic (sodium chloride and ammonium sulfate) and organic (citric acid and adipic acid) particles. Growth curves of the particles have been measured in ethanol vapor and as a comparison in water vapor as a function of saturation ratio. Measurements in water vapor show that sodium chloride and ammonium sulfate as well as citric acid particles grow at water saturation ratios (S) of 0.8 and above, whereas adipic acid particles do not grow at S <  0.96. For sodium chloride and ammonium sulfate particles, a deliquescence point is observed at S = 0.75 and S = 0.79, respectively. Citric acid particles grow monotonously with increasing saturation ratios already at low saturation ratios and no clear deliquescence point is found. For sodium chloride and ammonium sulfate particles, no growth can be seen in ethanol vapor at saturation ratios below 0.93. In contrast, for adipic acid particles, the deliquescence takes place at around S = 0.95 in the ethanol vapor. The recrystallization of adipic acid takes place at S < 0.4. Citric acid particles grow in ethanol vapor similarly as in water vapor; the particles grow monotonously with increasing saturation ratios and no stepwise deliquescence is observed. The results show that the working principles of the OTDMA are operational for single-component aerosols. Furthermore, the results indicate that the OTDMA method may prove useful in determining whether aerosol particles contain organic substances, especially if the OTDMA is operated in parallel with a hygroscopicity TDMA, as the growth of many substances is different in ethanol and water vapors.

scholarly journals Simulating the influence of primary biological aerosol particles on clouds by heterogeneous ice nucleation

2018 ◽  
Vol 18 (20) ◽  
pp. 15437-15450 ◽  
Author(s):  
Matthias Hummel ◽  
Corinna Hoose ◽  
Bernhard Pummer ◽  
Caroline Schaupp ◽  
Janine Fröhlich-Nowoisky ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Aerosol Particles ◽  
Fungal Spores ◽  
Ice Nucleation ◽  
Ice Crystals ◽  
Atmospheric Measurements ◽  
Cloud Ice ◽  
Biological Aerosol Particles ◽  
Ice Phase ◽  
Heterogeneous Ice Nucleation

Abstract. Primary ice formation, which is an important process for mixed-phase clouds with an impact on their lifetime, radiative balance, and hence the climate, strongly depends on the availability of ice-nucleating particles (INPs). Supercooled droplets within these clouds remain liquid until an INP immersed in or colliding with the droplet reaches its activation temperature. Only a few aerosol particles are acting as INPs and the freezing efficiency varies among them. Thus, the fraction of supercooled water in the cloud depends on the specific properties and concentrations of the INPs. Primary biological aerosol particles (PBAPs) have been identified as very efficient INPs at high subzero temperatures, but their very low atmospheric concentrations make it difficult to quantify their impact on clouds. Here we use the regional atmospheric model COSMO–ART to simulate the heterogeneous ice nucleation by PBAPs during a 1-week case study on a domain covering Europe. We focus on three highly ice-nucleation-active PBAP species, Pseudomonas syringae bacteria cells and spores from the fungi Cladosporium sp. and Mortierella alpina. PBAP emissions are parameterized in order to represent the entirety of bacteria and fungal spores in the atmosphere. Thus, only parts of the simulated PBAPs are assumed to act as INPs. The ice nucleation parameterizations are specific for the three selected species and are based on a deterministic approach. The PBAP concentrations simulated in this study are within the range of previously reported results from other modeling studies and atmospheric measurements. Two regimes of PBAP INP concentrations are identified: a temperature-limited and a PBAP-limited regime, which occur at temperatures above and below a maximal concentration at around −10 ∘C, respectively. In an ensemble of control and disturbed simulations, the change in the average ice crystal concentration by biological INPs is not statistically significant, suggesting that PBAPs have no significant influence on the average state of the cloud ice phase. However, if the cloud top temperature is below −15 ∘C, PBAP can influence the cloud ice phase and produce ice crystals in the absence of other INPs. Nevertheless, the number of produced ice crystals is very low and it has no influence on the modeled number of cloud droplets and hence the cloud structure.

scholarly journals Cloud history can change water–ice–surface interactions of oxide mineral aerosols: a case study on silica

2020 ◽  
Vol 20 (2) ◽  
pp. 1075-1087 ◽  
Author(s):  
Ahmed Abdelmonem ◽  
Sanduni Ratnayake ◽  
Jonathan D. Toner ◽  
Johannes Lützenkirchen
Keyword(s):  
Surface Properties ◽  
Second Harmonic ◽  
Aerosol Particles ◽  
Water Structure ◽  
Cloud Droplet ◽  
Ice Nucleation ◽  
Nonlinear Spectroscopy ◽  
Atmospheric Conditions ◽  
Mineral Aerosols ◽  
Interfacial Water Structure

Abstract. Mineral aerosol particles nucleate ice, and many insights have been obtained on water freezing as a function of mineral surface properties such as charge or morphology. Previous studies have mainly focused on pristine samples despite the fact that aerosol particles age under natural atmospheric conditions. For example, an aerosol-containing cloud droplet can go through freeze–melt or evaporation–condensation cycles that change the surface structure, the ionic strength, and pH. Variations in the surface properties of ice-nucleating particles in the atmosphere have been largely overlooked. Here, we use an environmental cell in conjunction with nonlinear spectroscopy (second-harmonic generation) to study the effect of freeze–melt processes on the aqueous chemistry at silica surfaces at low pH. We found that successive freeze–melt cycles disrupt the dissolution equilibrium, substantially changing the surface properties and giving rise to marked variations in the interfacial water structure and the ice nucleation ability of the surface. The degree of order of water molecules, next to the surface, at any temperature during cooling decreases and then increases again with sample aging. Along the aging process, the water ordering–cooling dependence and ice nucleation ability improve continuously.

scholarly journals Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

2019 ◽  
Author(s):  
Nsikanabasi Silas Umo ◽  
Robert Wagner ◽  
Romy Ullrich ◽  
Alexei Kiselev ◽  
Harald Saathoff ◽  
...  
Keyword(s):  
Fly Ash ◽  
Significant Role ◽  
Coal Fly Ash ◽  
Aerosol Particles ◽  
Ice Nucleation ◽  
Temperature Cycling ◽  
Cloud Formation ◽  
Ice Formation ◽  
Nucleation Activity ◽  
Ice Nucleation Activity

Abstract. Ice-nucleating particles (INPs), which are precursors for ice formation in clouds, can alter the microphysical and optical properties of clouds, hence, impacting the cloud lifetimes and hydrological cycles. However, the mechanisms with which these INPs nucleate ice when exposed to different atmospheric conditions are still unclear for some particles. Recently, some INPs with pores or permanent surface defects of regular or irregular geometries have been reported to initiate ice formation at cirrus temperatures via the liquid phase in a two-step process, involving the condensation and freezing of supercooled water inside these pores. This mechanism has therefore been labelled as pore condensation and freezing (PCF). The PCF mechanism allows formation and stabilization of ice germs in the particle without the formation of macroscopic ice. Coal fly ash (CFA) aerosol particles are known to nucleate ice in the immersion freezing mode and may play a significant role in cloud formation. In our current ice nucleation experiments with CFA particles, which we conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) aerosol and cloud simulation chamber at the Karlsruhe Institute of Technology, Germany, we partly observed a strong increase in the ice-active fraction for experiments performed at temperatures just below the homogeneous freezing of pure water, which could be related to the PCF mechanism. To further investigate the potential of CFA particles undergoing PCF mechanism, we performed a series of temperature-cycling experiments in AIDA. The temperature-cycling experiments involve exposing CFA particles to lower temperatures (down to ~ 228 K), then warming them up to higher temperatures (238 K–273 K) before investigating their ice nucleation properties. For the first time, we report the enhancement of the ice nucleation activity of the CFA particles for temperatures up to 263 K, from which we conclude that it is most likely due to the PCF mechanism. This indicates that ice germs formed in the CFA particles’ pores during cooling remains in the pores during the warming and induces ice crystallization as soon as the pre-activated particles experience ice-supersaturated conditions at warmer temperatures; hence, showing an enhancement in their ice-nucleating ability compared to the scenario where the CFA particles are directly probed at warmer temperatures without temporary cooling. The enhancement in the ice nucleation ability showed a positive correlation with the specific surface area and porosity of the particles. On the one hand, the PCF mechanism could be the prevalent nucleation mode for intrinsic ice formation at cirrus temperatures rather than the previously acclaimed deposition mode. On the other, the PCF mechanism can also play a significant role in mixed-phase cloud formation in a case where the CFA particles are injected from higher altitudes and then transported to lower altitudes after being exposed to lower temperatures.

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