Investigations into the suspected airborne transmission of pathogens in healthcare environments have posed a challenge to researchers for more than a century. If carried by a favorable air flow, bioaerosol material may be distributed over large distances with potentially fatal results. So the objective of this study is to perform the characterization of culturable and non-culturable bacteria, and fungi, and identify health-significant and antibiotic-resistant microbes. The ambient bioaerosols samples were collected in the greater Doha area, Qatar, during the autumn, winter, and summer seasons. Bacterial and fungal concentration, size distribution, and diversity were investigated by culture studies coupled with biochemical assays and next-generation sequencing. A total of over 70 samples were collected and processed with the Coriolis micro–microbial air sampler in each season from 7 stations. There was a significant increase in the concentration of bacteria and fungus during and after the rain. These concentrations were much lower than those in most cities worldwide may be due to the arid climate feature. The average concentration of bacteria was higher than the fungus throughout the winter season. Identification of culturable bacteria was done by biochemical assays using API 20E kit and fungus identification was done by microscopic analysis. Over 484 microbial species were detected using 16SrRNA gene-based next-generation sequencing.  Biodiversity analysis shows that bacterial and fungal diversity was the same at all the stations regardless of the location which shows that the local factors don’t have much impact on the bacterial and fungal biodiversity. However, there was a difference in microbial diversity in the winter season as compared to the summer, spring, and transition seasons. A scan of health significant pathogens has been performed on the identified microbes’ data. Several health-significant bacterial and fungal species were identified in Qatar ambient air including staphylococci, legionellae, tuberculous and nontuberculous, bacterial spore formers Clostridium difficile and Bacillus anthracis, and fungi Aspergillus, Penicillium, and Cladosporium spp and Stachybotrys chartarum which are strongly associated with allergic respiratory disease, especially asthma. Despite emerging significant public health concerns of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in urban air, it has not received significant attention. On the other hand, current air pollution health studies rely heavily on PM mass concentration, without considering biological parameters such as ARGs or ARB. An identification of the antibiotic-resistant strains was carried out according to the WHO priority classification and several microbes including Acinetobacter baumannii (WHO Priority 1: CRITICAL), Enterococcus faecium, Staphylococcus aureus, Campylobacter coli and Streptococcus pneumonia  (Priority 2: HIGH) were found in the ambient air. 

How to cite: Rasool, K., Sajjad, B., Abdul Jabbar, K., Elmallah, S., and Siddique, A.: Microbial aerosol characteristics and health implications in the highly arid environment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-223, https://doi.org/10.5194/egusphere-egu23-223, 2023.

Whilst there is a consensus that aerosol particles and primary biological aerosol particles (PBAPs) play an important role in regulating the global climate, with aerosols-PBAPs research increasing lately in Brazil, information summarizing the available knowledge is limited. Here, we present a systematic review of research published during the last 35-years on aerosols-PBAPs in Brazil. A total of 212 studies encompassing 474 cases met the selection criteria. The Amazon rainforest was the most studied biome represented by 72% of cases, followed by the Atlantic Forest with 18%. Studies focusing on the Amazon rainforest mostly studied climate-related issues and aerosol physics, with less than 5% examining the biological identity of aerosols, whereas outside the Amazon rainforest this number reached 16%. In addition, more than half of the cases within Amazon (55%) were held at seven sampling sites only, but conclusions were mainly extrapolated to the entire biome. On the other hand, research beyond Amazon has mostly addressed temporal and biological characterization of PBAPs, and not only is it scattered, but also scarce. Regarding sampling effort, most cases (72%) have had less than 100 days of sampling, and 60% of them spanned less than half a year of study, confining research to one or two seasons at the most. Consequently, while research from different countries that conduce their studies within Brazil and scientific fields are focusing on the same area, inconsistences are slowing the progress of this research topic. We argue that scientists from different fields of research (e.g., biologists, physicists) and countries should work together to produce more detailed and complete assessments of aerosols-PBAPs in the country as a whole, particularly on regards to their biological identity, given their importance to global climate regulation.

How to cite: Mantoani, M., Martins, J., Martins, L., Carotenuto, F., Šantl-Temkiv, T., Morris, C., Rodrigues, F., and Gonçalves, F.: 35-years of aerosols-PBAPs research in Brazil: the need to think outside the Amazonian box, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-414, https://doi.org/10.5194/egusphere-egu23-414, 2023.

Bioaerosols consist of a complex mixture of airborne microorganisms including fungi, bacteria, pollen, particulates and by-products of cells. While exposure to diverse microorganisms is essential for normal immune system development, bioaerosol inhalation has been associated with respiratory allergy and inflammation. Bioaerosol are ubiquitous, yet their composition within different environments is not well understood. Such information is essential for assessing exposure and associated health impacts. Here we focus on transport environments, namely railway stations (RSs), which pose a potential source of occupational and community exposure. 

Over 1200 passive dust samples were taken from 17 RSs across the UK from 03/2014-05/2015. GIS methods were used to provide information on population characteristics of the immediate surrounding area of the RSs. Together with information on RS layout and passenger numbers, this informed the selection of 250 samples, representing 9 RSs of varied geographical location, layout and footfall for further analysis. High throughput sequencing (HTS) with a metabarcoding approach targeting the ITS2 region was used to analyse the fungal composition of the sample subset. Such HTS techniques provide an opportunity to measure a wider range of microorganisms than traditional culture or microscopy techniques.

RS characteristics were varied and included indoor/enclosed and mostly outdoor layouts. Annual footfall varied from approximately 10-148 million.  The fungal composition of RS over time and relationships with different RS characteristics will be presented, identifying those driving any differences in composition.

How to cite: Marczylo, E., Macchiarulo, S., Isaac, J., Brookes, J., Crook, B., Anees-Hill, S., Hansell, A., and Douglas, P.: Assessing exposure to fungal bioaerosols in transport environments: Analysing fungal composition of passive dust samples collected in UK railway stations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14789, https://doi.org/10.5194/egusphere-egu23-14789, 2023.

Metabolically active microorganisms are increasingly acknowledged as actors of cloud chemical reactivity able to use organic compounds present in clouds (e.g. organic acids, aldhedydes) for their metabolism (Vaïtilingom et al., 2013). Uncharacterized biological activity may play a major role especially during the night, while during daytime the abiotic degradation of organic compounds would be driven and dominated by hydroxyl radical (•OH) chemistry (Vaïtilingom et al., 2011). To better understand and predict the impact of biological activity on atmospheric chemical reactivity, the metabolic pathways of the whole cloud microbiome and their modulations by environmental conditions (temperature, light, oxidants) must now be assessed.

The METACLOUD project addresses metabolic acclimatation of cloud microorganisms under two contrasted situations simulating a summer day (17°C, with solar light and presence of hydrogen peroxide) and a winter night (at 5°C, in the dark and without hydrogen peroxide). A focus is made on formaldehyde assimilations as this compound is a key intermediate both in cloud radical chemistry and in many C1 biological pathway, using fluxomics (LC-HRMS and IC-HRMS) on ¹³C-formaldehyde supplemented samples. Experiments were conducted in specially designed photobioreactors, either on (1) freshly sampled cloud water from the research station at the top of the puy de Dôme station (1465m asl, PUY, France) including naturally present microorganisms, or (2) an artificial consortium assembled from microbial strains isolated from cloud water sampled at PUY and resuspended in an artificial medium mimicking the composition of marine cloud water (major inorganic and organic compounds).

Metatranscriptomes and metabolomes indicate metabolic acclimations of the cloud microbiome to model summer/winter conditions, especially linked with fatty acid regulation and central metabolism (e.g. citrate cycle). First results with ¹³C-formaldehyde showed carbon incorporation from this molecule into several classes of metabolites (e.g. nucleotides, amino acids, central metabolites), illustrating the complex biological fate of this compound in the environment. The data will be used to implement biological activity on cloud chemistry models.

Vaïtilingom M. et al. (2011) Atmospheric chemistry of carboxylic acids: microbial implication versus photochemistry. Atmos. Chem. Phys. 11, 8721-8733. doi: 10.5194/acp-11-8721-2011.

Vaïtilingom M. et al. (2013) Potential impact of microbial activity on the oxidant capacity and organic carbon budget in clouds. Proc. Nat. Acad. Sci. USA 110, 559-564. doi: 10.1073/pnas.1205743110.

How to cite: Joly, M., Jarrige, D., Vyscocil, J., Rossi, F., Judon, C., Bringel, F., Muller, E. E. L., Vuilleumier, S., Nadalig, T., Portais, J.-C., Peyriga, L., Bellvert, F., Kulyk, H., Bianco, A., Deguillaume, L., Delort, A.-M., and Amato, P.: Exploring metabolic acclimation of the cloud microflora to contrasting summer day and winter night conditions using metatranscriptomics and fluxomics approaches, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6196, https://doi.org/10.5194/egusphere-egu23-6196, 2023.

Dicarboxylic acids are an essential component of tropospheric aerosols emitted directly or formed in chemical processes. The physiochemical properties and heterogeneous oxidation of aerosol particles containing maleic acid (MA) have been investigated using a mixed quantum and classical approach. The multiphase reactions of primary ozonide formation between the gas phase, the particle interface, and its bulk strongly influence the reaction mechanism and rate coefficients. Based on snapshots issued taken from molecular dynamics simulations, the mechanism of MA + O₃ reaction is investigated in three different environments using ab initio method and density functional theory. The interfacial water molecules enhance the initial reaction step of MA + O₃, with a larger rate constant at the air-water interface than in the gas phase. By assuming the Langmuir-Hinshelwood behavior and comparing it with the bulk, the ozonolysis of maleic acid mainly occurs in the bulk, and O₃ diffusion in the bulk may be the limiting process.

How to cite: Abouhaidar, R., Duflot, D., and Toubin, C.: Toward a molecular level understanding of heterogeneous processes at atmospheric aerosol surfaces: ozonolysis of maleic acid droplets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1123, https://doi.org/10.5194/egusphere-egu23-1123, 2023.

Oceans, through algae and phytoplankton activities, are the main source of iodine, including monohalogenated organic compounds as CH₃I [1].  There is missing knowledge about interactions between iodinated compounds and aerosols in the troposphere. In this context, this work investigates the adsorption of gaseous iodomethane (CH₃I) on model sea-salt aerosols at various humidities. The water coverage tends to stabilize CH₃I at the salt surface. The lifetime of CH₃I in the atmosphere (in gas phase or adsorbed on aerosols) may be altered by its reaction with gas phase radicals. The reaction of CH₃I with OH is thus investigated both in gas phase and in presence of water by means of quantum mechanical calculations.

References:

[1] Saiz-Lopez et al, Chem. Rev. 2012, 112, 1773–1804.

Acknowledgments:

I-SITE ULNE OVERSEE project (contract ANR-16-IDEX-004)

The CaPPA project (Chemical and Physical Properties of the Atmosphere) is funded by the French National Research Agency (ANR) through the PIA (Programme d’Investissement d’Avenir) under contract « ANR-11-LABX-0005-01 » and by the Regional Council « Hauts-de-France » and the « European Funds for Regional Economic Development » (FEDER)

How to cite: Toubin, C., Infuso, M., Louis, F., Taamalli, S., and Duflot, D.: Theoretical study of the adsorption of Methyl Iodide on model sea-salt surfaces, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4481, https://doi.org/10.5194/egusphere-egu23-4481, 2023.

Atmospheric loading of black carbon aerosols influences air quality and visibility, and their mixing state and aerosol chemistry were sensitive to both emission scenarios and regional transport. In this study, the aerodynamic size-resolved mixing state of refractory black carbon aerosols (rBC) and elemental composition were investigated using a novel tandem system consisting of an aerodynamic aerosol classifier (AAC), a single particle soot photometer (SP2), and single-particle-aerosol mass spectrometry (SPA-MS) during the XXIV Olympic Winter Games (OWG) at an urban site in Beijing. We found that rBC-containing particles with an aerodynamic diameter (D_ae) of 300 nm were characterized by a rBC core with a count median diameter (CMD) of 108±4 nm that typically have regular morphology ( , higher relative coating thickness (RCT: mean ~1.8), and strong light absorption enhancement (E_abs: mean ~1.4). The rBC-containing particles with D_ae = 200 nm normally had irregular shapes and weak E_abs. Classification based on air mass clustering and air pollution level revealed that the coating thickness of rBC particles only exhibited unimodal patterns under clean air conditions but bimodal distributions under heavy pollution conditions, implying multiple origins of rBC particles, even during OWG periods. Furthermore, the chemical compositions of the rBC coating quantitatively determined by SPA-MS were used to estimate the possible origins of rBC with D_ae = 300 nm. Our results showed that rBC particles were primarily mixed with organics, nitrate, and sulfate during the XXIV OWG period. The organic components have a limited role in increasing rBC coatings under polluted conditions, while the alkali metal ions (K and Na) associated with traffic emissions and the secondary inorganic species favor the formation of thick coatings. Higher RH makes limited contributions to rBC mixed with sulfate and organics only (BCOC*_S) and pure BC. The relatively fresh BC could directly mix with organics and sulfate at low RH levels while evolving to mix with nitrate at high RH conditions. In addition to high concentrations of locally emitted precursors and high RH that tend to form thick coatings of nitrate-related rBC aerosols, secondary transport from the west and southwest also contributes to rBC aerosols mixed with nitrate with relatively thick coatings.

How to cite: Zhang, Y. and Pan, X.: Size–resolved mixing state of ambient refractory black carbon aerosols in Beijing during the XXIV Olympic Winter Games, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4752, https://doi.org/10.5194/egusphere-egu23-4752, 2023.

Kinetics of collision-sticking processes between vapor molecules and clusters of low volatile compounds govern the initial steps of atmospheric new particle formation. Conventional non-interacting hard-sphere models underestimate the collision rate by neglecting long-range attractive forces, and the commonly adopted assumption that every collision leads to the formation of a stable cluster (unit mass accommodation coefficient) is questionable for small clusters, especially at elevated temperatures. Here, we present a generally applicable analytical interacting hard-sphere model for evaluating collision rates between molecules and clusters, accounting for long-range attractive forces. In the model, the collision cross section is calculated based on an effective molecule-cluster potential, derived using Hamaker’s approach. Applied to collisions of sulfuric acid or dimethylamine with neutral bisulphate-dimethylammonium clusters composed of 1-32 dimers, our new model predicts collision rates 2-3 times higher than the non-interacting model for small clusters, while decaying asymptotically to the non-interacting limit as cluster size increases, in excellent agreement with a collision rate theory-atomistic molecular dynamics simulation approach. Additionally, we calculated sticking rates and mass accommodation coefficients (MAC) using atomistic molecular dynamics collision simulations. For sulfuric acid, unit MAC is observed for collisions with all cluster sizes at temperatures between 200 K and 400 K. For dimethylamine, we find that MACs decrease with increasing temperature and decreasing cluster size. At low temperatures, the unit MAC assumption is generally valid, but at elevated temperatures MACs can drop below 0.2 for small clusters.

How to cite: Reischl, B., Yang, H., Neefjes, I., Tikkanen, V., Kubečka, J., Kurtén, T., and Vehkamäki, H.: Collision-sticking rates of acid-base clusters in the gas phase determined from atomistic simulation and a novel analytical interacting hard-sphere model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6193, https://doi.org/10.5194/egusphere-egu23-6193, 2023.

Bioaerosols include bacteria that comprise about <1% of the total aerosol number concentration in the atmosphere. In current atmospheric models, bacteria are considered as not being metabolically active during their atmospheric residence time. This assumption is contradicting laboratory studies that have revealed that small organic compounds, such as formic and acetic acids, can be efficiently biodegraded by bacteria found in the atmosphere.

Formic and acetic acids are ubiquitous in the atmosphere, constituting main organic acids in the gas and aqueous phases. Their sources are usually dominated by direct emissions from biomass burning, fossil fuel combustion, vegetation, and soil, besides secondary production from gas and aqueous phase photochemistry. Their sinks are usually considered to be limited to wet and dry deposition, and oxidation by radicals (OH, NO₃).

To explore the potential role of biodegradation as an additional sink of formic and acetic acids, we implemented their biodegradation in cloud droplets in a detailed atmospheric multiphase chemistry model. As opposed to aqueous phase chemical reactions that occur in all droplets, biodegradation only occurs in a small fraction of droplets (~0.1%) taking into account the small number concentration of bacteria cells in the atmosphere.

We perform model sensitivity studies to identify atmospheric conditions (e.g., pH, cloud droplet size, processing time), under which biodegradation represents a significant sink of the two acids. Our model results show that the concentration of formic and acetic acids may be overestimated by up to 5% (~20 ppt) and 3% (~8 ppt), respectively if biodegradation is not included. The net formation or loss rates are predicted to be reduced by up to 20%. These contributions exceed by far the number concentration of bacteria-containing droplets, which implies that the acids evaporate from bacteria-free droplets and are efficiently taken up and biodegraded in the small portion of droplets. We show that the assumption of an average biodegradation rate in all droplets leads to an overestimate of the biodegradation rate, particularly at pH > 5. Generally, the highest importance of biodegradation is identified for large droplets and at pH ~5, which may be considered representative for remote locations. The results are highly sensitive to the pH value, as it not only increases the partitioning of the acids to the aqueous phase (effective Henry’s law constant) but also the rate constants of the OH reactions which compete with the biodegradation as acid sinks.

We conclude that current atmospheric chemistry models may be incomplete to assess the loss of organics in the atmospheric multiphase system as biodegradation might be a significant loss of formic and acetic acids and possibly of related organics.

How to cite: Nuñez Lopez, L., Amato, P., and Ervens, B.: Biodegradation of formic and acetic acids is a significant atmospheric sink, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6582, https://doi.org/10.5194/egusphere-egu23-6582, 2023.

Sugar like substances are usually small but important part of organic aerosol being often tracers for individual aerosol sources. Twelve hours samples (day and night) collected during winter and summer campaigns at three Central European rural background sites were utilized to characterize PM_2.5 aerosol using complex set of analytical methods. Here we report concentrations of sugars, sugar like alcohols and sugar anhydrides.

PM_2.5 samplings were performed during February–March and July–August 2021 at three sites, National Atmospheric Observatory Košetice – CZ (NAOK, N 49°35′, E 15°05′; 534 m a.s.l.), Frýdlant – CZ (N 50°94′, E 15°07′; 366 m a.s.l.) and Melpitz –DE (N 51°32', E 12°56'; 86 m a.s.l.). Each site was equipped with high volume Digitel sampler using sampling flow rate 500 l/min. Cut parts of the filter were extracted with ultrapure water and the extracts were analysed using HPAE-PAD analysis and Thermo Scientific 5000+ system for sugar-like substances using a method based on Iinuma et al. 2009.

The concentrations of sugar like substances were dominated by levoglucosan in winter at all sites, with 0.32±0.29 µg/m³ at Košetice, 0.21±0.13 µg/m³ at Frýdlant, and 0.15±0.13 µg/m³ at Melpitz. Mannosan/levoglucosan median ratio was the highest at Košetice (0.23) and lowest at Frýdlant (0.18).

The summer concentrations of sugar like substances were more evenly distributed in several major substances with concentrations one order lower in comparison to concentrations of levoglucosan in winter. The concentrations of individual sugars, sugar alcohols and sugar anhydrides were relatively evenly distributed, but some differences between the sites were found. The average sums of sugars were the highest of all categories at all sites, but while the sugar alcohols were the second highest in Melpitz, the content of sugar anhydrides was at the second place at Frýdlant and Košetice in summer.

Acknowledgements:

This work was supported within a German-Czech cooperation in the TRACE project funded by the GACR under grant 20-08304J and by DFG under grant 431895563, also by the MEYS of the Czech Republic under grants ACTRIS-CZ LM2018122 and ACTRIS-CZ RI (CZ.02.1 .01 / 0.0 / 0.0 / 16_013 / 0001315), and European Union's Horizon 2020 research and innovation program ACTRIS IMP (871115).

References:

• Iinuma, G. Engling, H. Puxbaum, H. Herrmann, A highly resolved anion-exchange chromatographic method for determination of saccharidic tracers for biomass combustion and primary bio-particles in atmospheric aerosol, Atmos. Environ., 43 (2009), pp. 1367-1371, 10.1016/j.atmosenv.2008.11.020

How to cite: Schwarz, J., Lhotka, R., Pokorná, P., Vodička, P., Zíková, N., Ondráček, J., Arora, S., Poulain, L., Herrmann, H., and Ždímal, V.: Sugar like compounds in PM2.5 at three rural background sites in Central Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7123, https://doi.org/10.5194/egusphere-egu23-7123, 2023.

Iodine chemistry is implicated in atmospheric chemistry and can lead to the formation of several oxides such as HOI, I₂, IO, OIO, and finally I₂O₅ or HIO₃, which may nucleate as nanoparticles relevant for cloud formation in remote environments (Saiz-Lopez et al., 2012, Finkenzeller et al., 2022). These oxides can be formed through reaction with oxidants or other halogen compounds in the gas phase or the particle phase. Most of the iodide oxidation processes have been suggested to be enhanced at interfaces, similar to those involving other halogen species, either due to the surface propensity of intermediates (Artiglia et al., 2017) or the iodine species itself (Moreno and Beaza-Romero, 2019). However, no data are available about the surface concentration of iodine species other than iodide. After two decades of research into the surface propensity of iodide and bromide, the picture emerges that their surface propensity is not as extreme as initially thought (Jungwirth and Tobias, 2002; Ghosal et al., 2005; Olivieri et al., 2018).

Liquid jet X-ray photoelectron spectroscopy (XPS) experiments have been carried out at the SIM beamline at the Swiss Light Source. Acquisition of kinetic energy dependent (thus at different probing depth) I3d, I4d core level and valence level spectra has been done for iodide, iodate and iodic acid. This allows to retrieve the surface propensity of these iodine species at the aqueous solution – air interface. HIO₃, HOI and iodide surface propensity has also been investigated by Ab Initio Molecular Dynamics computation at the revPBE-D3/DZVP-SR level using CP2K software (Khüne et al., 2020).

• Artiglia et al., Nat. Commun., 8, 700 (2017).
• Finkenzeller et al., Nat. Chem. (2022).
• Ghosal et al., Science, 307, 563 (2005).
• Jungwirth and D. Tobias, J. Phys. Chem. B, 106, 25, 6361 (2002).
• D. Kühne et al., J. Chem. Phys., 152, 194103 (2020).
• Moreno and M. T. Baeza-Romero, 21, 19835 (2019).
• Olivieri et al., J. Phys, Chem. B, 122, 2, 910 (2018).
• Saiz-Lopez et al., Chem. Rev., 112, 1773 (2012).

How to cite: Roose, A., Iezzi, L., Boucly, A., Yang, H., Krack, M., Ammann, M., and Artiglia, L.: Surface propensity of atmospheric iodine oxides: AIMD and LJ-XPS investigation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8213, https://doi.org/10.5194/egusphere-egu23-8213, 2023.

Nucleation of clusters from the gas phase is a widely encountered phenomenon, e.g. regional air quality and global climate are both directly impacted by particle formation from atmospheric trace gases [1]. Still, the underlying out-of-equilibrium dynamics of this process are not well understood. The classical view of nucleation assumes isothermal conditions where the nucleating clusters are in thermal equilibrium with their surroundings. However, as in all first-order phase transitions, latent heat is released, potentially heating the clusters and suppressing the nucleation. The question of how the released energy affects cluster temperatures during nucleation as well as the growth rate remains controversial.

To investigate the nonisothermal dynamics and energetics of homogeneous nucleation, we have performed molecular dynamics (MD) simulations of a supersaturated Lennard-Jones (LJ) vapor in the presence of thermalizing carrier gas. In addition, a previous study of homogeneous nucleation of carbon dioxide in argon carrier gas [2] was revisited for temperature analysis of the growing CO₂  clusters. The results obtained from these simulations are compared against kinetic modeling of isothermal nucleation and the classical nonisothermal theory by Feder et al. [3], which also predicts the existence of cool subcritical clusters, and has been quite controversial.

For the studied systems, we find that nucleation rates are suppressed by two orders of magnitude at most, despite substantial release of latent heat. Our analyses further reveal that while the temperatures of the entire cluster size populations are indeed elevated, the temperatures of the specific clusters driving the nucleation flux evolve from cold to hot when growing from subcritical to supercritical sizes. This resolves the apparent contradiction between elevated cluster temperatures and minor nonisothermal corrections to the nucleation rate, both often reported in literature, and is in excellent agreement with the theory of Feder et al. Our findings provide unprecedented insight into realistic nucleation events and allow us to directly assess earlier theoretical considerations of nonisothermal nucleation.

References

[1] M. Kulmala et al., Direct observations of atmospheric aerosol nucleation. Science 339, 943–946 (2013).

[2] R. Halonen et al., Homogeneous nucleation of carbon dioxide in supersonic nozzles II: Molecular dynamics simulations and properties of nucleating clusters. Phys. Chem. Chem. Phys. 23, 4517–4529 (2021).

[3] J. Feder, K. C. Russell, J. Lothe, G. M. Pound, Homogeneous nucleation and growth of droplets in vapours. Adv. Phys. 15, 111–178 (1966).

How to cite: Tikkanen, V., Reischl, B., Vehkamäki, H., and Halonen, R.: The cluster who came in from the cold: Nonisothermal nucleation in the gas phase is driven by cool subcritical clusters, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12521, https://doi.org/10.5194/egusphere-egu23-12521, 2023.

Next generation sequencing technologies have revolutionized the field of environmental science. Widely used short-read sequencing enables accurate microbial identification but is often slow, requires large centralised equipment, and does not allow to distinguish highly homologous genomic regions, making the taxonomic classification and genome assembly of closely-related species complicated. Those challenges may be resolved by the implementation of real-time long-read sequencing technologies such as Nanopore sequencing. Nanopore sequencing is a rapid technology that can be employed in situ through portable devices. The long sequencing reads can further improve precision of species identification in mixed microbial communities, and can provide more detailed characterisations of individual microorganisms. Despite its promising application to other environmental samples, nanopore sequencing has not yet been implemented to study bioaerosols and detect pathogens in air samples.

Here, we used nanopore sequencing to analyse the environmental DNA extracted from air samples collected in Barcelona, Spain, as an example of a highly urbanised area. As the total amount of DNA found in the air is significantly lower compared to other typical environmental material such as soil or water, we first optimised DNA extraction in combination with the newest nanopore rapid sequencing protocols to achieve a highly accurate genome assembly-based description of the air microbiome. We identified the presence of potentially pathogenic organisms, and annotated the genome assemblies with respect to phenotypic read-outs such as increased virulence and antimicrobial resistance.  We hereby compared the air microbiome assessed through a variety of air sampling methods, including high-volume air samplers, liquid impingers, and standard air filtering approaches. We further assessed if our optimized DNA extraction methods introduced a bias into the described microbiome composition by including positive controls. 

We were able to demonstrate that it is possible to identify airborne pathogens even when the amount of DNA is low, by leveraging cutting-edge nanopore sequencing technology without requiring cultivation or amplification. This method has the potential to enhance and speed up the surveillance of airborne diseases such as pneumonia, measles, and COVID-19. In upcoming research, we plan to utilise this framework to study the microorganisms present in the air in different settings in order to detect the potential emergence of antimicrobial resistance or highly virulent pathogens in real-time.

How to cite: Pozdniakova, S., Reska, T., Cañas, L., Borràs, S., Rodó, X., and Urban, L.: Monitoring airborne pathogens by nanopore sequencing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17161, https://doi.org/10.5194/egusphere-egu23-17161, 2023.

Acetamide is not only released into the atmosphere from natural sources, but its large-scale industrial use also results in its atmospheric emission. The main atmospheric sink of acetamide is its oxidation, however, other atmospheric fates are also plausible. In wet deposition, acetamide can be captured by ice grains through adsorption. Thus, we investigated the adsorption of acetamide at the surface of crystalline (I_h) and low density amorphous (LDA) ices by performing a set of grand canonical Monte Carlo simulations at the tropospheric temperature of 200 K. Besides calculating the adsorption isotherms, we also characterised the energetics of the adsorption and the orientational preferences of the first layer molecules. We demonstrated that at low enough surface concentrations, the adsorbed acetamide molecules prefer to lay parallel with the ice surface. With increasing surface coverage, acetamide molecules preferentially stay perpendicular to the surface, pointing by the CH₃ group straight away from the ice phase, typically forming 2 H-bonds with each other and 2 with the surface waters. Finally, after the appearance of outer layer acetamide molecules, first layer molecules prefer to form 3 H-bonds with their acetamide neighbours and only 1 with the surface waters.

As acetamide has been detected in a relatively large amount in space as well, we extended our study by performing grand canonical Monte Carlo simulations at 50 and 100 K on LDA ice, which are more characteristic of typical domains of the interstellar medium. We found that the relative importance of the acetamide–acetamide H-bonds with respect to the acetamide–water ones increases with decreasing temperature. As a result of it, the saturated monolayer, which is stable in a broad range of chemical potentials at 200 K, shrinks with decreasing temperature, and, eventually, vanishes at 50 K, while multilayer adsorption becomes more and more pronounced at the lower temperatures. Furthermore, our results suggest that non-negligible acetamide adsorption might occur on LDA surfaces at low enough temperature (i.e., 50 K and below), thus, the interstellar formation of peptide chains through acetamide molecules might well be a plausible process in the cold domains of the interstellar medium; however, it is rather unlikely in the higher temperature domains.

How to cite: Jedlovszky, P., Balbisi, M., Horvath, R., and Szori, M.: Computer simulation investigation of the adsorption of acetamide under atmospheric and interstellar conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7108, https://doi.org/10.5194/egusphere-egu23-7108, 2023.

Existence of viable human pathogens in air above the planetary boundary layer (PBL) susceptible of reaching far-distance regions has never been demonstrated. Now ten aircraft monitoring surveys conducted over Japan in 2014 confirm the existence of a vast diversity of microbial species between 1000-3000 m a.s.l. being dispersed through wind currents for distances up to 2000 Km. Use of atmospheric particle dispersion models and LIDAR data has enabled us to confirm that under very predominant wintertime atmospheric conditions, aerosolised particles are uplifted by seasonal strong winds from areas in NE China, travel near 2000 Km away from their source well above the PBL and subside over Japan in less than 2 days. The area in NE China is covered with vast amounts of frozen decaying organic material originating from massive cereal croplands. Characterisation of microbial species attached to those particles shows dominance of known human pathogens typically originating from sewage, pesticides, fertilisers or agricultural debris from decaying organic matter. A majority of fungal taxa (over 90% concentration at times) and/or bacterial taxa (up to 67%) found therein are known for their potential adverse effects on human health. Noticeably, for bacteria less of a 30% of the taxa appearing could be identified to the species level and an additional 30% at most only at the family level. Similar numbers for fungi appear. Over 390 different fungal genera and over 340 bacterial genera showed up in flight samples comprised in the 10 aircraft transects, showing a great resemblance between flight and surface origin. Overall diversity is similar in high-altitudes and the surface when entrainment of air develops. In our study, microbial viability has also been observed as well as transport of antimicrobial resistance genes (ARG) in the cultured flight bacteria. The former constitutes one of the first evidences of very far distant transport of ARG and adds to the current known mechanisms for ARG propagation.

How to cite: Rodó, X., Pozdniakova, S., Curcoll, R., Fontal, A., Matsuki, A., Tanimoto, H., Armengol, M. P., Pey, I., Vila, J., Muñoz, L., Cañas, L., Morguí, J.-A., and Borràs, S.: Rich microbial diversity in tropospheric samples above the planetary boundary layer confirms long-distance transport of potential human pathogens, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15891, https://doi.org/10.5194/egusphere-egu23-15891, 2023.