AS3.16

AS3
Atmospheric surface science and ice nucleating particles 

Atmospheric aerosol-cloud-climate interactions (e.g. heterogeneous nucleation, particle oxidation and photosensitization, molecular composition-, phase-, acidity- and structure- changes, ...) are fundamental processes in the atmosphere. Despite the importance of these processes in energy transfer, cloud dynamics, precipitation formation, and hence in climate change, little is known about the molecular mechanism and the respective contribution of different structural and chemical surface properties of the atmospheric aerosols controlling these processes in the atmosphere. For Example, ice particles in the atmosphere, both in cirrus and mixed-phase clouds, contribute to the largest uncertainty in interpretations of the Earth’s changing energy budget. Their large variability in number, size, shape, and surface properties makes it difficult to understand and parameterize their microphysical and hence radiative properties.

Fundamental understanding of the cloud dynamics and aerosol properties, which play the major role in the climate system, will require the understanding of gas-, water-, and ice-aerosol surface interactions. To advance our knowledge about atmospheric processes, this session aims to bring together two research areas, namely (1) Atmospheric Surface Science (ASS) and (2) Ice Nucleating Particles (INP):
(1) ASS is concerned with the experimental and theoretical approaches investigating atmospheric interactions as well as ice nucleation processes “on the molecular level”. The goal is to fill the gap between the large-scale atmospheric processes and gas-, water-, and ice- interactions with atmospherically relevant mineral and biological surfaces.
(2) INP are concerned with the laboratory examination, on a fundamental level, trying to understand the nucleation processes and characterizing INP in the atmosphere.

Convener: Hinrich Grothe | Co-conveners: Ahmed Abdelmonem, Christian Rolf, Odran Sourdeval
Presentations
| Wed, 25 May, 13:20–14:50 (CEST)
 
Room 0.11/12

Presentations: Wed, 25 May | Room 0.11/12

Chairpersons: Hinrich Grothe, Ahmed Abdelmonem, Odran Sourdeval
13:20–13:25
|
EGU22-8189
|
ECS
|
Presentation form not yet defined
Maher Sahyoun, Kostas K. Tsigaridis, Tina Santl-Temkiv, and Ulas Im

Primary biological aerosol particles (PBAPs) are present globally, contributing to the total observed aerosol loads. Yet, PBAPs likely form a smaller fraction of the total aerosol budget compared to other types of particles such as dust. According to the IPCC AR5 report, the terrestrial emission flux of PBAPs is highly uncertain and was estimated within the range of 50-1000 Tg/yr. Burrows et al. (2009) estimated the global emissions of bacteria-containing particles to range between 0.4 to 1.8 Tg/yr, with a median of 0.74 Tg/yr. However, PBAPs comprise a large fraction of the submicron particles > 0.2 mm in the middle to the upper troposphere and they can be dispersed to distant locations and high altitudes from their source regionss. PBAPs have the potential to play a key role in cloud formation by acting as cloud condensation nuclei (CCN), and ice nucleating particles (INP) active at high sub-zero temperatures, potentially impacting the Earth’s hydrological cycle and climate.

Recent observations suggest that the PBAP concentrations have likely been underestimated in global modeling studies (summarized in Huang et al., 2021). For example, the fragmented biological particles and microbial exudates still cannot be detected with many commonly used techniques and, therefore they were not accounted for in the previous global modeling studies. Other recent studies presented a novel secondary biological aerosol production. Moreover, observations revealed that biological INPs from marine surfaces may be of higher imporatance than what has previously been considered in modeling studies. PBAPs' emission flux is therefore not yet well constrained, and the uncertainty in their emission estimation remains unresolved and requires deeper investigation. Consequently, the climatic impacts and feedbacks of PBAPs remain highly uncertain.

In this study, we build and integrate for the first time a new emission model for PBAPs in the GISS-E2.1 Earth system model in order to calculate the total emission flux of PBAPs from terrestrial and marine surfaces into the atmosphere and estimate their transport and sinks. In this model, we consider different types of PBAPs, i.e., bacteria and fungal spores. For bacteria we used the estimated flux-rates from Burrows et al. (2009) for different ecosystems. In a later step, we will update those values for each ecosystem using recent observations, especially over the marine areas and land ice. For fungal spores, we used the parameterization of Janssen et al. (2021).

We present preliminary results of the emission fluxes, burdens, concentrations, lifetime, and direct radiative forcing due to aerosol-radiation interactions of PBAPs and validate them using previous studies. For example, the lifetime of bacteria of size 1 micron is calculated to equal 3.5 days, which is comparable with the 3.4 days estimated by Burrows et al. (2009). 

 

References

Burrows, S. M. et al., ACP 2009, 9(23),9281, doi: https://doi.org/10.5194/acp-9-9281-2009.

Huang, S. et al., Environment International 2021, 146., doi: https://doi.org/10.1016/j.envint.2020.106197

Janssen et al., ACP 2021, 21(6), 4381., doi: https://doi.org/10.5194/acp-21-4381-2021

How to cite: Sahyoun, M., K. Tsigaridis, K., Santl-Temkiv, T., and Im, U.: Primary Biological Aerosol Particles in GISS-E2.1 Earth system model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8189, https://doi.org/10.5194/egusphere-egu22-8189, 2022.

13:25–13:30
|
EGU22-140
|
ECS
|
Highlight
|
On-site presentation
Hannah Frostenberg, André Welti, Mikael Sjöstrand, and Luisa Ickes

The aerosols that can act as ice nucleating particles (INPs) are of a large variety in both size and chemical composition. This leads to different temperatures at which INPs can nucleate ice. In recent years, the type and properties of INP species that initiate freezing at certain conditions have been investigated in more and more detail. If this growing knowledge is to be used in models, it implies that the models hold very detailed information about the aerosol species abundant in clouds. Especially for climate models, this is a difficult challenge.

In this study, we approach the problem of parameterizing heterogeneous ice nucleation from another angle: assuming well-diluted background aerosol, the probability of a specific INP concentration at the current temperature follows a log-normal distribution. We derived relative frequency distribution functions (RFDs) from measurements in marine environments (Welti et al., 2018). The number of INPs for the current temperature is being drawn from this RFD following its weighting. Thus, one randomly selected INP concentration is used from the range of all possible INP concentrations derived from observations at the given temperature. The advantage of our freezing parameterization is that it does not need any information about the chemical composition or size of the aerosols present in the cloud. It is valid for remote locations that are not close to a source of INPs, e.g. maritime or polar sites.

We implemented this new parameterization into the large-eddy simulation model MIMICA (Savre et al., 2014) and evaluated it for a mixed-phase Arctic cloud observed during the ASCOS expedition (Tjernström et al., 2014). For the Arctic there is large uncertainty about the types of INPs as well as their concentration, which is a challenge for modelling mixed phase clouds in this region. In our talk, we show that our new scheme does work well for the simulated case. We will present the performance of this new framework, as well as its sensitivity to RFD distribution variables and the model domain resolution. Additionally, we compare the new parameterization to “classic” heterogeneous nucleation schemes, such as a simple active sites parameterization.

Savre, J., Ekman, A. M. L., and Svensson, G. (2014), Technical note: Introduction to MIMICA, a large-eddy simulation solver for cloudy planetary boundary layers, J. Adv. Model. Earth Syst., 6, 630–649, doi:10.1002/ 2013MS000292.
Tjernström, M.; Leck, C., et al. (2014), The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design, Atmos. Chem. Phys., 14, 2823–2869.
Welti, A., Müller, K., Fleming, Z. L., and Stratmann, F. (2018), Concentration and variability of ice nuclei in the subtropical maritime boundary layer, Atmos. Chem. Phys., 18, 5307–5320.

How to cite: Frostenberg, H., Welti, A., Sjöstrand, M., and Ickes, L.: How can we make use of the observed variability of ice nucleating particle concentrations in models?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-140, https://doi.org/10.5194/egusphere-egu22-140, 2022.

13:30–13:35
|
EGU22-2777
|
ECS
|
On-site presentation
Yaqiong Hu, Ping Tian, Mengyu Huang, Kai Bi, Julia Schneider, Nsikanabasi S. Umo, Nikolas Ullmerich, Kristina Höhler, Xiaoqin Jing, Huiwen Xue, Deping Ding, Yongchun Liu, Thomas Leisner, and Ottmar Möhler

Ice-nucleating particles (INPs) are of great importance for regional weather and climate by altering the microphysical properties of clouds. Large uncertainties still exist for the sources, abundance and variability of INPs over the polluted North China Plain (NCP) due to limited observations in this region and the complex physical and chemical properties of aerosols from multiple sources. In this study, the concentrations of INPs in the immersion freezing mode at temperatures ranging from -5 ℃ to -30 ℃ were simultaneously measured for about one month in the Spring season. The measurements were carried out at a mountain site and a suburb site in Beijing representing clean and anthropogenic condition, respectively. Different concentrations and characteristics of INP are found for the two sites, which reflect the influence of different the air masses and INP sources. Consistent with previous studies in this region, dust particles are found to be the most abundant INPs during the Spring season, and the contribution from anthropogenic pollution aerosols was of minor importance. Most interestingly, the INP concentration at the mountain site was about one magnitude higher than at the suburban site at temperatures higher than -10 ℃, which is caused by the primary biological aerosol from the forests in the moutain area. Our results characterize the important role of these bioaerosols, which are also expected to have a strong impact on the glaciation of orographic clouds.

In addition, to extend the data set, we investigated the characteristics of INPs in other seasons, to further study and quantify seasonal cycles of INP concentrations and sources.

How to cite: Hu, Y., Tian, P., Huang, M., Bi, K., Schneider, J., Umo, N. S., Ullmerich, N., Höhler, K., Jing, X., Xue, H., Ding, D., Liu, Y., Leisner, T., and Möhler, O.: Characteristics of ice-nucleating particles in Beijing during Spring: a comparison study for the suburban and a nearby mountain area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2777, https://doi.org/10.5194/egusphere-egu22-2777, 2022.

13:35–13:40
|
EGU22-1647
|
ECS
|
On-site presentation
Baptiste Testa, Lukas Durdina, Jacinta Edebeli, Curdin Spirig, Julien Anet, and Zamin Kanji

Aircraft operate mainly in the upper troposphere/lower stratosphere — altitudes where the aerosol loading is rather low — emitting gases (mainly H2O and CO2) and soot particles (a result of the incomplete combustion of aviation fuel). At these altitudes, clouds composed of micrometric ice crystals (known as cirrus clouds) originate from the freezing of small liquid droplets and/or from the deposition of water vapor onto solid particles (called ice nucleating particles, INPs). Aircraft soot particles are thought to be efficient INPs for cirrus-cloud formation, therefore potentially disturbing the cirrus cloud coverage, resulting in a modified cloud radiative budget, hence affecting climate. To date, the ice-nucleating abilities (INAs) of aircraft soot have not been quantified partly because of the challenge to sample such particles behind a turbine engine.

In this work, we present a series of experiments conducted at the aircraft engine test cell of SR Technics at Zurich airport, aiming at quantifying the INAs of aircraft turbine soot particles. Exhaust from commercial turbofan engines was sampled using a traversable probe within 1.5 m downstream of the exhaust nozzle over a range over power levels from medium to high thrust. The exhaust sample was drawn through trace-heated lines and a series of driers into a stirred stainless steel tank, allowing the coagulation of the particles, similar to that thought to occur in the restricted volume between aircraft wingtip vortices. The stainless steel tank also acts as a reservoir for the rest of the ice nucleation experiment. The coagulated particles were then size-selected according to their electrical mobility diameters in all experiments and injected into a cloud chamber where they experienced cirrus-relevant temperature (T < -40 °C) and relative humidity (RHice > 100%) conditions, allowing them to form ice crystals. Together with the inline particle size and mass distribution measurements, the fraction of soot particles forming ice crystals at different RHice levels has been measured. A catalytic stripper operating at 350°C removing volatile material and sulfur was used upstream of the cloud chamber, helping to infer the effect of the mixing state on the soot INAs. In parallel, soot samples were collected for additional offline measurements. Microscopy and gas adsorption techniques were used to characterize the morphology of the soot particles (e.g., primary particle size, pore size distribution) as well as their surface properties (e.g., water affinity, organic/inorganic content) which are known to be critical parameters for the freezing mechanism of soot particles in the cirrus regime. Preliminary results show that samples after the conditioning with the catalytic stripper are more active INPs than the unstripped, suggesting that mixing state and organic/sulfur content could be important for determining the role of aircraft soot as INPs in the upper troposphere.

How to cite: Testa, B., Durdina, L., Edebeli, J., Spirig, C., Anet, J., and Kanji, Z.: Ice nucleating properties of aircraft turbine engine soot particles with respect to cirrus clouds formations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1647, https://doi.org/10.5194/egusphere-egu22-1647, 2022.

13:40–13:45
|
EGU22-10880
|
ECS
|
Virtual presentation
Soleil Worthy, Anand Kumar, Yu Xi, Jingwei Yun, Jessie Chen, Cuishan Xu, Victoria Irish, Pierre Amato, and Allan Bertram

EGU Abstract

 

A wide range of materials including mineral dust, soil dust, and bioaerosols have been shown to act as ice nuclei in the atmosphere. During atmospheric transport, these materials can become coated with inorganic and organic solutes which may impact their ability to nucleate ice. While a number of studies have investigated the impact of solutes at low concentrations on ice nucleation by mineral dusts, very few studies have examined their impact on non-mineral dust ice nuclei.

We studied the effect of dilute (NH4)2SO4 solutions (0.05 M) on immersion freezing of a variety of non-mineral dust ice nucleating substances including bacteria, fungi, sea ice diatom exudates, sea surface microlayer, and humic substances using the droplet freezing technique. We also studied the effect of (NH4)2SO4 on immersion freezing of mineral dust particles for comparison purposes. (NH4)2SO4 had no effect on the median freezing temperature of 9 of the 10 tested non-mineral dust materials. There was a small but statistically significant decrease in the median freezing temperature of the bacteria X. campestris (change in median freezing temperature  = -0.43 ± 0.19 °C) in the presence of (NH4)2SO4 compared to pure water. Conversely, (NH4)2SO4 increased the median freezing temperature of four different mineral dusts (potassium-rich feldspar, Arizona test dust, kaolinite, montmorillonite) by 3 °C to 9 °C and increased the ice nucleation active site density per gram of material by a factor of ~10 to ~30.

This significant difference in the response of mineral dust and non-mineral dust ice nucleating substances when exposed to (NH4)2SO4 suggests that they nucleate ice and/or interact with (NH4)2SO4 via different mechanisms. This difference suggests that the relative importance of mineral dust to non-mineral dust particles for ice nucleation in mixed-phase clouds could increase as these particles become coated with (NH4)2SO4 in the atmosphere. This difference also suggests that the addition of (NH4)2SO4 to atmospheric samples of unknown composition could be used as an indicator or assay for the presence of mineral dust ice nuclei.

How to cite: Worthy, S., Kumar, A., Xi, Y., Yun, J., Chen, J., Xu, C., Irish, V., Amato, P., and Bertram, A.: The effect of (NH4)2SO4 on the freezing properties of non-mineral dust ice nucleating substances of atmospheric relevance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10880, https://doi.org/10.5194/egusphere-egu22-10880, 2022.

13:45–13:50
|
EGU22-2413
|
ECS
|
Presentation form not yet defined
Barbara Bertozzi, Robert Wagner, Kristina Höhler, Harald Saathoff, Thomas Leisner, and Ottmar Möhler

Cirrus are high-level clouds composed uniquely of ice crystals. To correctly estimate their radiative contribution to the Earth’s energy budget, it is necessary to know their optical properties,  which in turn depend on the formation mechanism. Cirrus clouds can form either by homogeneous freezing of supercooled aqueous solution droplets or by heterogeneous freezing with the contribution of an ice nucleating particle (INP). Therefore, it is fundamental to understand which aerosol particles are present in the upper troposphere and contribute to initiate heterogeneous ice nucleation.

Sulphate particles are among the most abundant aerosol types in the upper troposphere, and their degree of neutralization with ammonia significantly varies with geographical location and altitude. According to the ammonium-to-sulphate ratio (ASR), three pure inorganic salts can form in the H2SO4/NH3/H2O system: ammonium bisulphate (NH4HSO4, ASR = 1), letovicite (NH4)3H(SO4)2, ASR = 1.5), and ammonium sulphate ((NH4)2SO4, ASR = 2). However, the transport, ageing and processing of atmospheric aerosols are more likely to lead to a variety of mixtures of the different salts than to particles with exact stoichiometry. The ice nucleation ability of aqueous sulphuric acid (ASR=0) and fully neutralized crystalline ammonium sulphate particles has been extensively investigated in the past. The low-temperature phase state and ice nucleation ability of partially neutralized particles, instead, has never been measured before.

In this contribution, we present new AIDA cloud chamber experiments on the crystallization, deliquescence, and ice nucleation ability of partially neutralized particles in the H2SO4/NH3/H2O system (1<ASR<2) at temperatures between -60 and -40°C. Particles with various ASR were generated i) from bulk solutions with pre-defined composition and ii) from the in situ neutralization of aqueous sulphuric acid aerosol particles. The latter experiments aimed at simulating the gradual neutralization process that acidic solution droplets may experience in the upper troposphere. A comprehensive characterization of the low-temperature phase state of the particles as a function of relative humidity was obtained by combining FTIR spectra, laser light scattering and depolarisation measurements, as well as water uptake experiments in a continuous flow diffusion chamber (CFDC). We measured the ice nucleation ability with expansion cooling experiments in the AIDA cloud simulation chamber and with two CFDCs.

Our results show that in the cirrus cloud temperature range, the phase state and ice nucleation ability of particles in the H2SO4/NH3/H2O system depend on their degree of neutralization. In particular, we measured an increased ice nucleation ability with increasing degree of neutralization. Quantifying the abundance and neutralization degree of ammoniated sulphate particles in the upper troposphere may thus be critical to correctly represent their direct and indirect effect on climate.

How to cite: Bertozzi, B., Wagner, R., Höhler, K., Saathoff, H., Leisner, T., and Möhler, O.: Crystallization, deliquescence, and ice nucleation ability of ammoniated sulphate particles in the cirrus cloud temperature range, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2413, https://doi.org/10.5194/egusphere-egu22-2413, 2022.

13:50–13:55
|
EGU22-2082
|
Presentation form not yet defined
Brian Durham, Christian Pfrang, and Aliakbar Hassanpouryouzband

For fourteen days in November the world’s attention turned to the rise in atmospheric GHG levels, on this occasion with a special focus on methane (Nature 25 August 2021).  Methane had previously been the subject of a study on gas hydrate formation and, while noting the relevance of this property to climate change modelling, the authors in that case wrote: `Curiously, gas hydrates seem to defy intuition about hydrophobic compounds, as the concentration of a nonpolar gas in the solid hydrate lattice is more than two orders of magnitude higher than the solubility of such a gas in liquid water’ (Walsh et al 2008 `Microsecond Simulations of Spontaneous Methane Hydrate Nucleation and Growth' ). 

The term `non-polar’ applies to the gases of Earth’s atmosphere - so does the same concentration paradox apply to the inclusion of each of these species in atmospheric ice? For CO2, curves published by the University of Lille quantify hydrate formation across a range of partial pressures, and are projected to a zero pressure origin, thereby embracing the partial pressure of the gas in Earth atmosphere (Chazallon and Pirim (2018) `Selectivity and CO2 capture efficiency in CO2-N2 clathrate hydrates investigated by in-situ Raman spectroscopy', Figs 4A and 4B).  Moreover, in the presence of ice phase at -12°C our own results have shown that, from a CO2+N2 mixture, more than 90% of CO2 goes into the ice/hydrate phase, which is three times higher that at 10°C (Hassanpouryouzband et al 2019 `Geological CO2 capture and storage with flue gas hydrate formation in frozen and unfrozen sediments').

We simulate hydrate formation in the Earth's atmosphere using laboratory apparatus designed to quantify the depletion of GHGs (including water vapour) from a chilled airstream at atmospheric pressure across a range of temperatures, followed by analysis of the condensate. 

How to cite: Durham, B., Pfrang, C., and Hassanpouryouzband, A.: Laboratory simulation of gas hydrate formation at ice surfaces in Earth atmosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2082, https://doi.org/10.5194/egusphere-egu22-2082, 2022.

13:55–14:00
|
EGU22-1606
|
ECS
|
On-site presentation
Pia Bogert, Johannes Graf, Larissa Lacher, Kristina Höhler, Elke Ludewig, and Ottmar Möhler

In mixed-phase clouds, primary ice formation occurs only in the presence of ice-nucleating particles (INPs) [Vali et al., 2015], which are a very rare subset of the aerosols in the atmosphere. INPs are an important part of the earth climate system, as they can initiate the formation of precipitation [Mülmenstädt et al., 2015] and have an influence on the cloud radiative properties [Murray et. al, 2021]. In the last decades, different INP measurements have been performed within the atmospheric boundary layer at mixed-phase clouds conditions [Kanji et. al, 2017]. INP measurements in the free troposphere are challenging, as they can only be conducted by aircraft-based measurements or at high altitude mountain stations. However, it is important to study long-term INP concentrations at different altitudes and geographical locations to get a better understanding of the presence of INPs in the atmosphere.

The Sonnblick Observatory (SBO) in the Austrian Alps is located at an altitude of 3106 m above sea level and is an ideal location to investigate the INP concentration in the free troposphere, as the measured INPs are directly relevant for ice formation. Since August 2019, we continuously measure the INP concentration at the SBO via filter collection and offline analysis with INSEKT (Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology) [Schneider et. al, 2020]. The analysis of the sampled aerosols gives us the temperature dependent number concentration of INPs at temperatures above -25°C with a time resolution of one week. In order to receive a better insight into short-term fluctuations, we performed additional measurements with the online INP measurement PINE (Portable Ice Nucleation Experiment) [Möhler et al., 2021], since the end of July 2021. PINE has a time resolution of 5 – 6 min and usually measures at a constant temperature of ~ -23°C. In addition, INP activity screenings in the range from -15°C to -30°C are performed in regular intervals and during interesting meteorological periods such as Saharan dust events. The overlap in temperature ranges of INSEKT and PINE enables a comparison between the two measuring instruments.

Our results show that there are significant seasonal variations in the INP concentration. Especially during the summer time, strong diurnal variations in the INP concentration were observed, which could be explained by the influence of convectively lifted air from the boundary layer during the day. Correlations of the measured INP concentrations to meteorological parameters, aerosol properties and boundary layer stability will be discussed. In addition, we will present a case study of a dust event, which shows a sudden, strong increase in the INP concentration.

How to cite: Bogert, P., Graf, J., Lacher, L., Höhler, K., Ludewig, E., and Möhler, O.: A two-year record of INP concentration measurements at the Sonnblick Observatory (3106 m): Insight into seasonal variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1606, https://doi.org/10.5194/egusphere-egu22-1606, 2022.

14:00–14:05
|
EGU22-10216
|
ECS
|
On-site presentation
Elise Wilbourn, Larissa Lacher, Mauro Mazzola, Ottmar Möhler, and Naruki Hiranuma

Although the coverage of ice-nucleating particle (INP) measurements grows more comprehensively distributed by the year, studies measuring comprehensive aerosol properties often focus extensively on one or two sites at most, and methodology between studies even within the same lab is rarely the same as methods are refined and study aims differ. This inconsistency in part contributes to a sizeable uncertainty in effective radiative forcing estimation in regard to aerosol cloud interactions. To complement our insufficient knowledge of aerosol properties, we compiled and assessed a multitude of aerosol measurements from four sites: Graciosa Island to represent a predominantly marine site (data from autumn 2020), central Oklahoma to represent a mid-latitude terrestrial site (data from autumn 2019), and Utqiagvik, Alaska (data from autumn 2021) and Ny-Ålesund, Svalbard (data from autumn 2019 and 2020) to represent Arctic sites in different longitudes.

Here we report both total aerosol concentration as well as information related to two distinct aerosol concentrations: INPs and cloud concentration nuclei (CCN). INPs were measured using a single online and two offline methods, while CCN and total aerosol concentrations were measured with the same methods and similar instrumentation. This dataset can allow a broad-level comparison of several contrasting sites which would be expected to have vastly different INP and CCN activated fractions and total concentrations due to the variety in aerosol sources around the globe. Our spatial variation analysis indicates the aerosol concentrations vary by up to two orders of magnitude between sites (approximately 101 to 103 particles per cubic centimeter), while INP and CCN concentrations measured by two comparable methods vary by an order of magnitude (approximately 101 to 102 INPs per liter, and approximately 101 to 102 CCN per cubic centimeter) and INPs show much less variation than the ranges reported by previous studies. This small range may be due to similarities in INP composition, even as total aerosol population composition varies. For instance, INPs at all sites include a population of dust aerosols (either locally sourced or long-range transported). On the other hand, the total aerosol sources are more divergent between sites, especially between continental and marine-dominant sites where the greatest differentiation is seen. As well, previous studies have focused on a yearly average rather than a single season, which may also lead to greater variation. There is also variation in the heat-sensitivity of the INP samples, with continental samples from Graciosa Island showing the least heat sensitivity. Carefully comparing a large dataset containing a variety of aerosol property information including INP and CCN concentrations will allow us to determine patterns in the global distribution of aerosols that will be important as future climate models are developed.

How to cite: Wilbourn, E., Lacher, L., Mazzola, M., Möhler, O., and Hiranuma, N.: A multi-site comparison of aerosol properties, including ice-nucleating particles, measured during autumn field campaigns with online and offline techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10216, https://doi.org/10.5194/egusphere-egu22-10216, 2022.

14:05–14:10
|
EGU22-4323
|
ECS
|
On-site presentation
Corina Wieber, Sigurd Agerskov Madsen, Mads Rosenhøj Jeppesen, Frederik Voldbirk, Peter Melvad, Andrey Chuhutin, Leendert Vergeynst, Lorenz Meire, Kai Finster, Claus Melvad, and Tina Šantl-Temkiv

The properties and formation of clouds are one of the largest sources of uncertainties in climate models. Hereby, ice nucleating particles (INPs) play a major role since they directly affect the ice formation in clouds. To better characterize the impact of INPs, measuring devices are necessary to reliably determine the freezing temperatures of various aerosols.

We have developed a new ice nucleation assay, AU-Micro-INC, to measure the freezing temperatures with high accuracy. 96-well and 384-well plates can be inserted into a gallium matrix which ensures good thermal contact to the underlying cooling system. A Peltier element in combination with a vapor chamber provide a homogeneous cooling of the system. The freezing temperatures are measured with an infrared thermal camera with high precision.

The setup is validated using well-studied samples such as Snomax® and Illite NX. Further, the new setup is applied to sea water, sea surface microlayer, and sea ice samples previously collected in Kobbefjord and Nuup Kangerluaand in proximity of Nuuk, Greenland and preliminary data will be shown. 

How to cite: Wieber, C., Madsen, S. A., Jeppesen, M. R., Voldbirk, F., Melvad, P., Chuhutin, A., Vergeynst, L., Meire, L., Finster, K., Melvad, C., and Šantl-Temkiv, T.: The new ice nucleation assay AU-Micro-INC, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4323, https://doi.org/10.5194/egusphere-egu22-4323, 2022.

14:10–14:15
|
EGU22-11105
|
On-site presentation
Peter Alpert, Anthony Boucly, Yang Shuo, Huanyu Yang, Kevin Kilchhofer, Zhaochu Luo, Celestino Padeste, Simone Finizio, Markus Ammann, and Benjamin Watts

Precipitation is mostly formed via the ice phase in mixed phase clouds, and ice clouds are very relevant for Earths’ climate. Freezing or prevention of freezing is common to everyday life, e.g. for food and drug storage, icing and de-icing, etc. However, the ice nucleation process is not well understood, since it occurs on the size scale of clusters of molecules and time scales of molecular fluctuations. In this study, we have taken a step toward nanoscale observation of particles that nucleate ice by developing a new ice nucleation instrument, referred as the INXcell, which couples an ice nucleation environmental cell to the scanning transmission X-ray microscope (STXM) at the Swiss Light Source. We employ near-edge X-ray absorption fine-structure spectroscopy (NEXAFS) to map in situ chemical composition of ice nucleating particles with 35 × 35 nm2 spatial resolution. The main technical challenge was control of temperature, T, and thus relative humidity, RH, while maintaining X-ray transparency. In the INXcell, X-rays are focused onto a sample through a temperature-controlled aperture, which was modified to host a jet of nitrogen cooled down to 170 K. The cold jet impinges on the back surface of a sample exposed to water vapor to control sample temperature and thus RH. We used our unique spectroscopic and ice nucleation capability and investigated the heterogeneous freezing ability of ferrihydrite particles with and without coatings of citric acid. Ferrihydrite is an amorphous or poorly crystalline iron oxyhydroxide abundant in mineral dust and is difficult to identify with conventional XRD analysis. We confirmed that ferrihydrite could nucleate ice via immersion freezing and deposition ice nucleation, depending on whether or not the particles first take up water, respectively. When coating ferrihydrite with citric acid, mimicking organic coatings that aerosol particles obtain throughout their atmospheric lifetime, we observed a reduction in the efficiency to nucleate ice following freezing point depression. Spectroscopic identification of the coated ferrihydrite structure emplyed the iron and carbon X-ray absorption L-edges and K-edge, respectively. We also investigated feldspar particles coated with xanthan gum, a surrogate for a highly ice active mineral with a highly viscous organic coating. We observed that deposition ice nucleation occurred only below the RH dependent glass transition of xanthan gum. Using a newly developed stochastic freezing model (SFM) based on solution water activity, we reproduced average conditions and data scatter of the RH and T at which ice formed. Additionally, we ran our model with atmospheric idealized air parcel trajectories and found overall that deposition ice nucleation was the dominant heterogeneous freezing mechanism. Homogeneous ice nucleation subsequent to water uptake out-performed immersion freezing.

How to cite: Alpert, P., Boucly, A., Shuo, Y., Yang, H., Kilchhofer, K., Luo, Z., Padeste, C., Finizio, S., Ammann, M., and Watts, B.: Ice Nucleation Imaged In Situ with X-ray Spectro-Microscopy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11105, https://doi.org/10.5194/egusphere-egu22-11105, 2022.

14:15–14:20
|
EGU22-12220
|
ECS
|
On-site presentation
Florian Reyzek, Paul Bieber, Teresa M. Seifried, Nadine Bothen, Ralph Schwidetzky, Ulrich Pöschl, Konrad Meister, Misha Bonn, Janine Fröhlich-Nowoisky, and Hinrich Grothe

Various biological aerosol particles such as certain pollen, fungi, and bacteria are known as ice-nucleating particles with high onset freezing temperatures. It came as a surprise when Pummer et al. (2012) found that solubilized macromolecules were responsible for the ice nucleation activity of tree pollen, rather than the grains themselves. More recently, ice-nucleating macromolecules (INMs) have also been found on other tree tissues (Felgitsch et al., 2018, Seifried et al., 2020). In general, INMs are present in much greater numbers than the micrometer sized pollen grains and thus the emission of INMs from the biosphere might play a more important role than previously thought (Bieber et al., 2020, Burkart et al., 2021, Seifried et al., 2020, 2021).

So far, the chemical composition and structure of INMs remains largely unknown. To shine light on this, we extracted INMs from birch pollen with water and conducted various treatments, purification, and freezing experiments. For example, we detected ice nucleation activity after filtration through a 10 kDa cutoff filter. However, the concentration after 10 kDa filtration was comparatively lower than after 30 kDa or 50 kDa filtration suggesting that the INMs consist of agglomerates.

To concentrate the INMs we used ice affinity purification followed by treatment with acetone to precipitate proteins. We found high ice nucleation activity of this material, suggesting that the INM is an ice nucleating protein. Subsequently, size exclusion chromatography was used to isolate the INMs, leading us to a sample with high concentrations of INMs. Finally, the identification of INMs from trees will be the basis of understanding the mechanism of ice nucleation under atmospheric conditions.

 

References

Bieber, P.; Seifried, T.M.; Burkart, J.; Gratzl, J.; Kasper-Giebl, A.; Schmale, D.G., III; and Grothe, H. A Drone-Based Bioaerosol Sampling System to Monitor Ice Nucleation Particles in the Lower Atmosphere. Remote Sens., 12, 552. https://doi.org/10.3390/rs12030552, 2020.

Burkart, J., Gratzl, J., Seifried, T. M., Bieber, P., and Grothe, H.: Isolation of subpollen particles (SPPs) of birch: SPPs are potential carriers of ice nucleating macromolecules, Biogeosciences, 18, 5751–5765, https://doi.org/10.5194/bg-18-5751-2021, 2021.

Felgitsch, L., Baloh, P., Burkart, J., Mayr, M., Momken, M. E., Seifried, T. M., Winkler, P., Schmale III, D. G., and Grothe, H.: Birch leaves and branches as a source of ice-nucleating macromolecules, Atmos. Chem. Phys., 18, 16063–16079, https://doi.org/10.5194/acp-18-16063-2018, 2018.

Pummer, B. G., Bauer, H., Bernardi, J., Bleicher, S., and Grothe, H.: Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Atmos. Chem. Phys., 12, 2541–2550, https://doi.org/10.5194/acp-12-2541-2012, 2012.

Seifried, T. M., Bieber, P., Felgitsch, L., Vlasich, J., Reyzek, F., Schmale III, D. G., and Grothe, H.: Surfaces of silver birch (Betula pendula) are sources of biological ice nuclei: in vivo and in situ investigations, Biogeosciences, 17, 5655–5667, https://doi.org/10.5194/bg-17-5655-2020, 2020.

Seifried, T.M.; Bieber, P.; Kunert, A.T.; Schmale, D.G., III; Whitmore, K.; Fröhlich-Nowoisky, J.; and Grothe, H. Ice Nucleation Activity of Alpine Bioaerosol Emitted in Vicinity of a Birch Forest. Atmosphere, 12, 779. https://doi.org/10.3390/atmos12060779, 2021.

How to cite: Reyzek, F., Bieber, P., Seifried, T. M., Bothen, N., Schwidetzky, R., Pöschl, U., Meister, K., Bonn, M., Fröhlich-Nowoisky, J., and Grothe, H.: Are proteinaceous agglomerates responsible for ice nucleation activity of birch pollen?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12220, https://doi.org/10.5194/egusphere-egu22-12220, 2022.

14:20–14:25
|
EGU22-12404
|
On-site presentation
Julia Burkart, Jürgen Gratzl, Teresa Seifried, Paul Bieber, and Hinrich Grothe

Within the last years pollen grains have gained increasing attention due to their cloud-forming potential. Especially the discovery that ice nucleating macromolecules (INMs) or subpollen particles (SPPs) obtained from pollen grains are able to initiate freezing has stirred up interest in pollen. INMs or SPPs are much smaller and potentially more numerous than pollen grains and could significantly affect cloud formation in the atmosphere.

However, INMs and SPPs are not clearly distinguished. This has motivated the present study, which focuses on birch pollen and investigates the relationship between pollen grains, INMs and SPPs. According to the usage of the term SPPs in the medical fields, we define SPPs as the starch granules contained in pollen grains. We show that these insoluble SPPs are only obtained when fresh pollen grains are used to generate aqueous extracts from pollen. Due to the limited seasonal availability of fresh pollen grains almost all studies have been conducted with commercial pollen grains. To enable the investigation of the SPPs we develop an alternative extraction method to generate large quantities of SPPs from commercial pollen grains. We show that INM are not bonded to SPPs (i.e. can be washed off with water). Further, we find that purified SPP are not ice nucleation active: after several times of washing SPPs with ultrapure water the ice nucleation activity completely disappears. To our knowledge, this is the first study to investigate the ice nucleation activity of isolated SPPs.

To study the chemical nature of the INMs, we use fluorescence spectroscopy. Fluorescence excitation-emission maps indicate a strong signal in the protein range (maximum around λex = 280 nm and λem = 330 nm) with all ice nucleation active samples. In contrast, with purified SPP the protein signal is lost. We also quantify the protein concentration with the Bradford assay. The protein concentration ranges from 77.4 μg mL-1 (Highly concentrated INM) to below 2.5 μg mL-1 (purified SPP). Moreover, we investigate the connection between proteins and ice nucleation activity by treating the ice nucleation active samples with subtilisin A and urea to unfold and digest the proteins.  After this treatment the ice nucleation activity clearly diminished. The results indicate a linkage between ice nucleation activity and protein concentration. The missing piece of the puzzle could be a glycoprotein, which exhibits carboxylate functionalities, can bind water in tertiary structures and displays degeneration and unfolding of its secondary structure due to heat treatment or reaction with enzymes. Even though purified SPPs are not ice nucleation active they could act as carriers of INMs and distribute those in the atmosphere.

Reference of the study: Burkart, J., Gratzl, J., Seifried, T. M., Bieber, P., and Grothe, H.: Isolation of subpollen particles (SPPs) of birch: SPPs are potential carriers of ice nucleating macromolecules, Biogeosciences, 18, 5751–5765, https://doi.org/10.5194/bg-18-5751-2021, 2021. 

How to cite: Burkart, J., Gratzl, J., Seifried, T., Bieber, P., and Grothe, H.: Isolation of subpollen particles (SPPs) of birch: SPPs are potential carriers of ice nucleating macromolecules, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12404, https://doi.org/10.5194/egusphere-egu22-12404, 2022.

14:25–14:30
|
EGU22-13322
|
ECS
|
Presentation form not yet defined
Paul Bieber, Teresa M. Seifried, Florian Reyzek, Nadine Borduas-Dedekind, and Hinrich Grothe

Certain biological macromolecules can play a unique role in heterogeneous ice nucleation, triggering freezing of atmospheric cloud droplets at high sub-zero temperatures (Pummer et al., 2012). Some ice nucleating proteins (INPs) of procaryotic organisms (e.g. Pseudomonas syringae) have been identified as highly efficient ice nuclei, but the isolation and identification of INPs from eucaryotic cells (e.g. pollen or fungal spores) remains challenging due to the increasing complexity of the samples’ matrices (Burkart et al., 2021, Seifried et al., 2020). To analyze INPs from birch pollen extracts, we applied a top-down workflow, including ice-shell purification, size exclusion chromatography and gel electrophoresis as separation techniques followed by fluorescence spectroscopy, infrared spectroscopy and mass spectrometry for characterization and the Vienna Optical Droplet Crystallization Analyzer (VODCA) for determining the ice nucleation activity (Felgitsch et al., 2018). We found several proteins as possible contributors to the freezing activity of birch pollen at around -16°C. However, the exact sequence of the INP and the molecular mechanism behind the ice nucleation remains elusive. To address this knowledge gap, we are currently focusing on a broader bottom-up approach which illuminates the ice nucleation mechanism of proteins in general. Specific peptides can be synthesized in-vitro and the ice nucleation activity of pure synthetic substances will be analyzed by using the drop Freezing Ice Nuclei Counter (FINC) (Miller et al., 2021). Exchanging or modifying single amino acids will allow to determine the mechanisms behind the nucleation and to draw a picture of sequences that indicate possible INPs in various organisms. Such a method can provide a basis for the investigations of INPs across the borders of genera and species and can help building fundamental understanding behind biologically induced ice nucleation at high sub-zero temperatures in the atmosphere.

References

Burkart, J., Gratzl, J., Seifried, T. M., Bieber, P., and Grothe, H.: Isolation of subpollen particles (SPPs) of birch: SPPs are potential carriers of ice nucleating macromolecules, Biogeosciences, 18, 5751–5765, https://doi.org/10.5194/bg-18-5751-2021, 2021.

Felgitsch, L., Baloh, P., Burkart, J., Mayr, M., Momken, M. E., Seifried, T. M., Winkler, P., Schmale III, D. G., and Grothe, H.: Birch leaves and branches as a source of ice-nucleating macromolecules, Atmos. Chem. Phys., 18, 16063–16079, https://doi.org/10.5194/acp-18-16063-2018, 2018

Miller, A. J., Brennan, K. P., Mignani, C., Wieder, J., David, R. O., and Borduas-Dedekind, N.: 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, Atmos. Meas. Tech., 14, 3131–3151, https://doi.org/10.5194/amt-14-3131-2021, 2021.

Pummer, B. G., Bauer, H., Bernardi, J., Bleicher, S., and Grothe, H.: Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Atmos. Chem. Phys., 12, 2541–2550, https://doi.org/10.5194/acp-12-2541-2012, 2012.

Seifried, T. M., Bieber, P., Felgitsch, L., Vlasich, J., Reyzek, F., Schmale III, D. G., and Grothe, H.: Surfaces of silver birch (Betula pendula) are sources of biological ice nuclei: in vivo and in situ investigations, Biogeosciences, 17, 5655–5667, https://doi.org/10.5194/bg-17-5655-2020, 2020.

How to cite: Bieber, P., Seifried, T. M., Reyzek, F., Borduas-Dedekind, N., and Grothe, H.: The atmospheric ice nucleation behavior of biological macromolecules: how top-down and bottom-up approaches help disentangle the role of proteins, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13322, https://doi.org/10.5194/egusphere-egu22-13322, 2022.

14:30–14:40
|
EGU22-13565
|
ECS
|
solicited
|
Presentation form not yet defined
Larissa Lacher, Karl Froyd, Gannet Hallar, Ian McCubbin, Justin Jacquot, Carmen Dameto de Espana, Xiaoli Shen, Gregory Schill, Darin Baker, Thomas Leisner, Ottmar Möhler, and Dan Cziczo

The presence of ice in mixed-phase clouds has a vital impact on their radiative properties, lifetime, and  ability to precipitate. Ice crystal formation is initially induced by a rare subset of ambient aerosol  particles called ice-nucleating particles (INPs). Despite the importance of INPs on aerosol-cloud interactions and century-long research efforts, the knowledge about their nature and atmospheric  abundance still needs improvement. Recent instrument developments allow more automated and  continuous INP measurements with a high time resolution, to gain a better understanding of the natural variability of INPs in different locations, and to investigate the identity and source regions of them. 

Here we present long-term observations of INPs at Storm Peak Laboratory (SPL) located in the Rocky Mountains of Colorado. SPL is at an altitude of 3200 m a.s.l. within the lower free troposphere, and in winter it is a location where mixed-phase clouds frequently occur. Therefore, the present aerosol particles are directly relevant for ice formation in such clouds. The ongoing INP measurements started in October 2021, and are conducted with the Portable Ice Nucleation Experiment (PINE) at conditions resembling the formation of mixed-phase clouds at temperatures between -22°C and -32°C. Results on the short-term and inter-seasonal variability will be presented, with a focus on parallel measurements of aerosol particle properties and meteorology. During the winter months of January and February 2022, we characterized the size of the INPs by selecting ice crystal residuals downstream of PINE using a pumped-counterflow virtual impactor and a novel optical particle counter. As this setup operates continuously, it is capable to investigate INP properties for longer time periods and to improve sampling statistics. In the future, it will be used with other diagnostic instruments, such as a single particle mass spectrometer, giving insights into the size and chemical composition of INPs, and thus allows to have a direct measure of the nature of INPs in ambient air.

How to cite: Lacher, L., Froyd, K., Hallar, G., McCubbin, I., Jacquot, J., Dameto de Espana, C., Shen, X., Schill, G., Baker, D., Leisner, T., Möhler, O., and Cziczo, D.: Measurements of ice-nucleating particle concentration and size at Storm Peak Laboratory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13565, https://doi.org/10.5194/egusphere-egu22-13565, 2022.

14:40–14:50