This session welcomes submissions on ambient observations, chamber and modelling studies of OA, which contribute to a deeper understanding of their origins (such as secondary OA formation or biomass burning), analysis of the molecular composition (e.g. targeted analysis of organic pollutants), investigation of physico-chemical properties, exploration of atmospheric transformation reactions (for example aging or brown carbon formation), and examination of gas-to-particle partitioning of organic molecules.
Orals: Mon, 4 May, 16:15–08:35 | Room F2
Secondary formation of OA in polluted urban environments involves diverse precursors and complex pathways. When the severity and frequency of heatwaves are expected to rise, little is about the heatwave impacts on the OA formation in such polluted environments. Here we deployed a long time-of-flight aerosol mass spectrometer (LTOF-AMS) to measure the real-time chemical composition of submicron aerosols along with advanced time-of-flight chemical ionization mass spectrometers (TOF-CIMS) to detect gaseous and particulate oxidation products in Beijing in recent years. Six process-level secondary OA (SOA) factors are resolved and unique molecular tracers for each of the six processes are identified. The six SOA factors can be explained by intensified photochemical and heterogeneous reactions with higher volatile organic compounds emissions and oxidant level, increased aerosol surface, stronger aerosol acidity, and higher ammonia concentration etc. The six-factor SOA seperation provides a machanistic understanding of the net enhancement of SOA during heatwave events, which have been observed in many places worldwide in summer. We further applied machine learning methods to identify the key drivers of the SOA enhancement and used the simulated key parameters from the GEOS-Chem model to perturb the SOA formation during the heatwave episode under clean air actions and climate change scenarios. Our results suggest that the SOA enhancement due to heatwave will be increasingly important in the future. This study underscores the urgency of validating temperature responses of organic aerosol in chemical transport models to facilitate air quality management in a warming world.
How to cite: Chen, Q., Zheng, Y., Koenig, T. K., Miao, R., Cheng, X., Zhang, Q., Wang, H., and Ge, Y.: Sources of organic aerosol in polluted urban environments and the heatwave impacts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17292, https://doi.org/10.5194/egusphere-egu26-17292, 2026.
Knowledge of the molecular characteristics of organic aerosols is essential for evaluating their atmospheric processes and associated environmental and health effects. However, little is known regarding the molecular characteristics of organic aerosols in coal resource-based cities. Herein, the molecular characteristics of water-soluble organic matter (WSOM) in wintertime PM2.5 during haze and heavy haze days in a typical coal resource-based city (Taiyuan, China) were analyzed using Fourier-transform ion cyclotron resonance mass spectrometry. A total of 5106 CcHhOoNnSs formulas were assigned, with m/z values predominantly concentrated in the range of 150–400 Da. The proportion of CHOS is higher than that in other cities, and a series of C7H6(CH2)0–8O5S formulas exhibited high intensities, most of which could be traced to coal combustion sources. The relative abundance of sulfur-containing organic molecules increased significantly on heavy haze days compared to haze days (30.4% vs. 25.0%) and was much higher than that observed in other cities. Additionally, CHO, CHON, and CHOS formulas consistently exhibited higher oxygen content on heavy haze days, likely due to atmospheric oxidation processes. Moreover, oxygen addition, methylation, and carboxylic acid reactions were identified as the primary possible pathways driving the transformation of primary organic aerosol into secondary organic aerosol under both haze and heavy haze conditions. Meanwhile, a total of 263 organophosphorus (OP) formulas were identified, which were predominantly distributed within the 180–550 Da range. 41.9% of assigned OP formulas contain −OPO3 or −RPO3 groups, and most OP formulas were oxidation-available with high environmental stability. Correlation analyses indicated that urban atmospheric OP may be emitted from biological sources. These results highlight the significant and distinct roles of both sulfur- and phosphorus-containing compounds in the complex atmospheric chemistry of coal resource-based urban environments.
How to cite: Guo, Z., Zhang, C., Liu, F., Zhang, G., Wang, J., and Bi, X.: Molecular characteristics of water-soluble organic aerosols in a coal resource-based city revealed by FT-ICR MS: a significant role of sulfur- and phosphorus-containing compounds, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7888, https://doi.org/10.5194/egusphere-egu26-7888, 2026.
Aromatic hydrocarbon secondary organic aerosols (SOAs) derived from anthropogenic sources are a typical class of secondary organic aerosols that significantly impact global climate and human health. The composition and physicochemical properties of atmospheric aerosols are notably influenced by varying oxidation conditions during the day and night. Currently, the molecular composition and formation mechanism of SOAs generated from benzene under diurnal oxidation conditions remain unclear. This study focuses on the molecular composition and chemical formation mechanism of secondary organic aerosols (SOAs) derived from benzene. We utilized the SAPHIR smog chamber to simulate diurnal oxidation experiments of benzene. The molecular composition evolution of benzene SOAs was characterized in real-time online using an Extractive Electrospray Ionization Chemical Ionization Mass Spectrometer (EESI-CIMS). We compared the differences in SOA composition under different oxidation conditions during the day and night, identified key characteristic products, and ultimately proposed relevant mechanisms for SOA formation. This research not only enhances our understanding of the chemical formation mechanisms of SOAs but also provides a scientific basis for air pollution control and climate change assessment.
How to cite: Luo, H., Shen, H., Wu, R., He, Q., Zorn, S. R., Fuchs, H., Mentel, T. F., and Zhao, D.: Molecular Composition and Formation Mechanism of Benzene SOA under Diurnal Oxidation Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4155, https://doi.org/10.5194/egusphere-egu26-4155, 2026.
New particle formation (NPF) proceeds efficiently in polluted urban areas, where oxygenated organic compounds are crucial for early particle growth. Their contribution to NPF depends on volatility distribution, described by the volatility basis set (VBS). Urban volatile organic compound (VOC) emissions have shifted significantly due to regulations and changing consumer habits. Volatile chemical products (VCPs) from cleaning agents, personal care products, and coatings, now rival or exceed combustion sources as primary urban VOC emitters. Though many VCP constituents are secondary organic aerosol (SOA) precursors, their oxidation pathways and NPF contributions remain poorly understood. Recent research highlights that assessing NPF potential requires knowing the full volatility range, including moderately oxygenated molecules (MOMs).
We investigate the full oxidation chain of selected VCP emissions, from VOC precursors to MOMs to highly oxygenated molecules (HOMs) and resulting particle yields. Oxidation occurs in a newly developed flow reactor designed to minimize wall losses and enable steady-state conditions. We employ multi-pressure chemical ionization mass spectrometry with an ultra-high-resolution Orbitrap mass spectrometer. By switching between low-pressure (<1 mbar) ionization for VOC detection using the internal fluoranthene (C16H10) ion source and two different atmospheric-pressure ionization schemes for MOMs (uronium, CH5N2O+) and HOMs (nitrate, NO3-), we capture the VBS across the full volatility range. New particle yields are quantified using a scanning mobility particle sizer (SMPS) and their chemical composition is evaluated using nanoelectromechanical sensors with Fourier transformation infrared spectroscopy (NEMS-FTIR).
We access household cleaning products as potential VCPs emitters. Method performance and consistency are evaluated using limonene oxidation as a reference system for NPF-relevant oxidation chemistry. The obtained VBS distributions can be compared to limonene ozonolysis, under the assumption that charging efficiencies might be well-related to compound volatility. This comparison enables an estimation of the relative NPF potential of different VCP emitters. We find significant variety in the NPF potential among cleaning products of different suppliers. While lemon-scented products resemble limonene (a major ingredient of these products) spectra, we can clearly demonstrate that the complex mixtures present in the cleaning products can enhance the NPF potential of certain products. Altogether, our results demonstrate that multi-pressure chemical ionization provides a powerful approach to link molecular composition, volatility, and NPF potential for emerging urban organic sources. Beyond advancing mechanistic understanding of urban aerosol formation, this framework enables identification of key VOC precursors in e.g. source apportionment approaches. In addition, our first results from different cleaning products show that through product reformulation new opportunities arise to mitigate air quality impacts associated with VCP emissions.
How to cite: Verma, R., Tischberger, M., Ellmauer, M., Grothe, H., and stolzenburg, D.: Volatile chemical products as potential emerging drivers of urban new particle formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14377, https://doi.org/10.5194/egusphere-egu26-14377, 2026.
Nanoparticle growth is a critical process determining whether newly formed nanoparticles can survive to cloud condensation nuclei (CCN) and haze sizes, thereby influencing climate and air quality. The growth is primarily driven by the condensation of low-volatility organic vapors. Therefore, comprehensive and accurate understanding of organic-driven particle growth processes is crucial for accurately assessing their environmental, climatic, and health impacts, and for developing targeted mitigation strategies. Three-dimensional models are essential tools for elucidating regional-scale particle evolution mechanisms. However, existing 3D atmospheric models fail to characterize the formation and condensation of low-volatility organics driving particle growth, which hinders accurate simulation and mechanistic understanding of growth processes.
Here, we develop an advanced 3D numerical modeling framework for organic gas-phase oxidation and particle growth by implementing the integrated two-dimensional volatility basis set (I2D-VBS) and a kinetic gas-particle partitioning model in WRF-Chem. This model accurately simulates organic oxidation products across the full volatility range and their condensation-driven nanoparticle growth processes. The model effectively reproduces process-level particle growth observed at different sites and seasons across China, reducing growth rate errors from orders of magnitude to reasonable ranges and significantly enhancing simulations of particle number size distributions.
Based on the improved model, we conduct a comprehensive analysis of organic-driven particle growth in China and identify the primary organic sources driving particle growth. Results show that particle growth rates in China are predominantly contributed by oxidation products of intermediate/semi-volatile organic compounds (I/SVOCs), accounting for >65% in winter and >59% in summer across key regions including Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta. Anthropogenic VOCs (AVOCs) rank second in contribution, though the contribution from biogenic VOCs (BVOCs) may exceed that from AVOCs in some southeastern regions during summer. Among precursor categories, aromatics and aliphatics are the most important, followed by oxygenated aromatics. Finally, we further elucidate the impacts of organic condensation-driven growth on particle and CCN number concentrations. This study fills critical knowledge gaps regarding particle growth mechanisms and their environmental impacts in China.
How to cite: Li, Z., Zhao, B., He, Y., Shen, J., Yin, D., and Wang, S.: Elucidating Mechanisms of Organic-Driven Nanoparticle Growth in China through Advanced Modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19850, https://doi.org/10.5194/egusphere-egu26-19850, 2026.
The southern African region, particularly the Atlantic coast of Namibia, is an ideal natural laboratory influenced by contrasting aerosol sources that represent endmembers of aerosol formation processes, including aged marine aerosols, mineral dust resuspension, and long-range transported biomass-burning aerosols (BBA), with only moderate local anthropogenic influence. This setting enables direct linkage between aerosol chemical composition and optical properties under near-pristine conditions, thereby improving the representation and projection of aerosol–radiation and aerosol–cloud interactions and associated climate feedbacks in close proximity to the highly sensitive southeastern Atlantic stratocumulus deck, one of the major regulators of planetary albedo.
Although organic matter (OM) typically accounts for only a minor fraction of aerosol mass, it demonstrates a disproportional contribution to optical properties, hygroscopicity and cloud-formation, especially in a dust-dominated environment. Here, we present a comprehensive characterization of OM with respect to its sources, molecular composition, aging processes, and relationships with aerosol optical properties. Organic aerosol (OA) was extracted from daily particulate matter (PM10) samples collected during a month-long field campaign at Gobabeb, Namibia, and analyzed using high-resolution mass spectrometry (HRMS), complemented by inorganic ion analysis, organic and elemental carbon quantification, and multivariate statistical methods. These approaches were used to distinguish three dominant aerosol regimes: dust-dominated, BBA-influenced, and marine-dominated periods.
Organic molecules associated with BBA events exhibited elevated O/C ratios and double-bond equivalent (DBE) values, consistent with enhanced light absorption in the UV–visible range. These molecular features show strong correlations with bulk aerosol extinction and scattering coefficients, highlighting the optical relevance of OM despite its limited mass contribution. To better constrain the contribution of dust-derived OM, laboratory resuspension experiments were conducted using local soils. Comparison of OM extracted from parent soils and resuspended aerosols revealed substantial compositional differences, indicating selective transfer of specific organic components into the aerosol phase. This selectivity allowed identification of soil-derived OM fractions that systematically contribute to atmospheric aerosols and their optical properties.
Finally, we applied a novel formula-difference approach to the HRMS data to resolve aerosol aging processes across the different aerosol regimes. By comparing molecular transformation patterns, we explored period-specific aging pathways reflected in characteristic gains and losses of functional groups and molecular connectivity. These chemical fingerprints indicate periods with higher influence of oxidation, condensation and aromatisation of OM, which provides additional insights into the fate of organic matter in mixed aerosol systems and its role in modifying aerosol optical properties during atmospheric aging.
How to cite: Zherebker, A., Baldo, C., Formenti, P., and Giorio, C. and the Aerofog team: Organic matter in dust-dominated aerosols over Namibia influenced by biomass burning and marine emissions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10531, https://doi.org/10.5194/egusphere-egu26-10531, 2026.
Per and polyfluoroalkyl substances (PFAS), a class of toxic compounds often referred to as “forever chemicals”, are increasingly detected in the atmosphere. Aerosolisation from contaminated aqueous reservoirs has been proposed as a pathway for atmospheric PFAS, drawing analogy to sea-spray processes and supported by their elevated concentrations reported near sewage treatment facilities (Kizhakkethil et al., 2025). However, aerosolisation and particle formation in anthropogenically impacted waters differ fundamentally from marine systems, and the physico chemical controls governing PFAS aerosolisation outside the marine context remain poorly understood.
The aim of this work was to investigate the effect of PFAS molecular properties, including carbon chain length and functional groups, on aerosolisation from contaminated aqueous solutions. Experiments were conducted in the Chamber for Aerosol Modelling and Bio-aerosol Research (ChAMBRe), Italy. Twenty five PFAS, covering short, medium and long chain perfluoroalkyl carboxylic acids, perfluoroalkane sulfonates, fluorotelomer sulfonates and emerging alternatives representative of wastewater impacted environments were investigated. The role of bioaerosol seed particles commonly present in such environments was also assessed, as they could act as sinks or carriers for highly surface active PFAS and thereby influence their aerosol phase distribution.
Aerosol mass size distributions revealed a strong dependence on molecular structure, indicating compound-specific particle-phase behaviour. The presence of biological particles did not systematically alter PFAS size-resolved distributions, suggesting that the studied PFAS exhibited limited interaction with bioaerosols and remained predominantly in the submicron size range under the investigated conditions, which may favour their atmospheric persistence and long-range transport.
Overall, these findings indicate that primary aerosol formation from contaminated aqueous systems represents a chemically selective pathway for introducing PFAS into the organic aerosol, with size-resolved characteristics governed primarily by molecular properties and aerosol formation processes.
Reference: Kizhakkethil, J. P., Shi, Z., Bogush, A., and Kourtchev, I.: Measurement report: Per- and polyfluoroalkyl substances (PFAS) in particulate matter (PM10) from activated sludge aeration, Atmos. Chem. Phys., 25, 5947–5958, https://doi.org/10.5194/acp-25-5947-2025, 2025.
How to cite: Kourtchev, I., Coupe, S., Pandamkulangara Kizhakkethil, J., Gatta, E., Massabò, D., Prati, P., Vernocchi, V., and Mazzei, F.: Effect of per and polyfluoroalkyl substances (PFAS) molecular properties on aerosolisation and size resolved distributions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1761, https://doi.org/10.5194/egusphere-egu26-1761, 2026.
Tropical forests are essential ecosystems for the global aerosol population [1]. The mechanisms behind new particle formation (NPF) in the Amazon have long remained elusive, with traditional “banana” events being rarely observed. Recent studies show that forest emissions of volatile organic compounds (VOCs) that are subsequently oxidized produce particles that can serve as Cloud Condensation Nuclei (CCN), which are critical for the tropical hydrological cycle. Several studies showed that new particle formation can occur at high altitudes (12-14 Km) [2]. Nanoparticles are also produced by different mechanisms at the canopy level, following oxidation by VOCs and downdrafts [3]. Another study showed that Quiet New Particle Formation also occurs in Amazonia and can be responsible for a significant fraction of the aerosol population [4]. These studies show a wide diversity of processes that produce nanoparticles, which adds to the population of primary biological particle emissions [1]. Ground-based long-term measurements were conducted at the Amazon Tall Tower Experiment (ATTO), integrating over 10 years of wet-season size-distribution measurements. Intensive aircraft campaigns conducted during the CAFÉ-Brazil experiment have identified the mechanisms underlying high-altitude particle production. We have also studied the role that deep convection and strong precipitation events play in modulating the particle population at the forest canopy level.
Of particular interest is the strong interaction between the plant metabolism and the climate they control, since aerosol particles influence the radiation balance, carbon cycling, and precipitation patterns. These natural wet-season processes compete with the dry-season biomass burning emissions, which strongly alter the particle population.
In this presentation, we will discuss the complex picture of particle production and development in Amazonia. This study sheds light on a previously unknown process of nucleation and growth occurring frequently in the Amazonian BL, distinct from the known intense particle bursts and growth associated with downdrafts.
[1] P. Artaxo, et al. Tellus Series B 24.1 (2022): 24–163.
[2] J. Curtius et al., Nature, 636 (2024) 124–130.
[3] L. A. T. Machado, et al., Atmos. Chem. Phys., 21.23 (2021) 18065–18086.
[4] B. B. Meller, et al., EGUsphere, 2025-4581 (2025).
How to cite: Artaxo, P., Meller, B., Rizzo, L., Machado, L., Valiati, R., and Pöhlker, C.: New particle formation in the Amazonian atmosphere and the role of organic compounds, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5958, https://doi.org/10.5194/egusphere-egu26-5958, 2026.
Atmospheric organic aerosol (OA) contains a mixture of molecules from various sources, both primary and secondary, and with different levels of atmospheric aging and propensity for particle-phase reactions. This highlights the need for detailed characterization of OA composition to better understand its sources, atmospheric transformation, and resulting physicochemical properties. This characterization is also preferably conducted in real-time, to capture both sudden changes of airmasses as well as fast reactions within the particles. We performed an intercomparison at our field station in Hyytiälä in the Finnish boreal forest where we deployed four different mass spectrometers able to measure aerosol composition in real-time. The instruments included an Aerosol Chemical Speciation Monitor (ACSM) as the reference instrument as well as three chemical ionization mass spectrometers (CIMS): a Vaporization Inlet for Aerosols coupled with a nitrate CIMS (VIA-NO3-CIMS), an Extractive Electrospray Ionization TOF (EESI-TOF), and a Filter Inlet for Gases and AEROsols coupled with an iodide CIMS (FIGAERO-I-CIMS). We also performed a follow-up chamber study to complement some missing comparisons due to instrumental problems during the field campaign.
CIMS has become a key tool for probing gas-phase composition, and studies have demonstrated how different reagent ions are able to detect distinct molecule types. In addition, using different methods for transferring aerosol-phase molecules into the gas-phase for detection by CIMS will most likely also result in differences in detected molecules. This study aimed to evaluate differences in instrument sensitivity for different types of OA and assess the fraction of OA that could be measured with these state-of-the-art methods deployed together.
The campaign in Hyytiälä (Sept 2-25, 2024) provided several interesting results. The foremost finding was a very high correlation between that the organics measured by the ACSM and the VIA–NO3-CIMS (R2 = 0.90) and FIGAERO-I-CIMS (R2 = 0.88). Consequently, also the VIA and the FIGAERO correlated extremely well, which was unexpected given that iodide and nitrate CIMS instruments tend to show very few common signals in typical gas-phase measurements. Sulfate measured by the VIA–NO3-CIMS agreed almost perfectly with ACSM measurements (R2 = 0.97), further validating that the instrument was working well throughout the campaign. Due to technical issues, however, the EESI-TOF did not provide enough data during the Hyytiälä campaign, and therefore we instead compared the VIA and EESI instruments with an AMS during a later chamber campaign using different types of aerosol precursors. This data is currently being analyzed in more detail, but at least for monoterpene-derived OA, also the EESI shows good correlation with the VIA, though with a higher sensitivity for less-oxygenated molecules while the VIA had higher sensitivity for the most oxygenated compounds. I will present more in-depth comparison results at the conference, including key differences between the methods, but our comparison indicates that all three aerosol CIMS instruments are able to detect a large fraction of the OA, at least in regions dominated by biogenic secondary OA.
How to cite: Ehn, M., Mickwitz, V., Li, Y., Qi, L., Zhang, J., Alton, M., Canagaratna, M., Graeffe, F., Nissinen, A., Pusfitasari, E., Schobesberger, S., and Zhao, J.: Comparison of mass spectrometric approaches for real-time characterization of organic aerosol, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16379, https://doi.org/10.5194/egusphere-egu26-16379, 2026.
Orals: Tue, 5 May, 08:30–10:15 | Room F2
New particle formation occurs broadly via two processes. First, small clusters can be stabilized by a reaction between constituents, such as proton transfer in acid-base clusters like sulfuric acid and ammonia. Second, constituents can simply be sufficiently sticky to remain clustered until more constituents arrive to make the cluster grow. This is classical nucleation and it depends on high vapor saturation ratios (supersaturation). It can occur for argon under the right conditions, but in the atmosphere nucleation involving organics is most interesting. Organics add the feature that they are an incredibly rich mixture of constituents, generally highly oxygenated, each with many oxygenated functional groups. We can describe this rich mixture in terms of volatility using the volatility basis set (VBS), and it has been established that nucleation appears to be second order with respect to the concentration of the least volatile class in the VBS, the so-called Ultra Low Volatility Organic Compounds (ULVOCs). Here we present an analysis of the overall volatility distribution to determine the fraction of ULVOCs that govern nucleation in both neutral and ion-induced nucleation. This depends on overall saturation ratios as well as the overall volatility distribution. The framework successfully describes the temperature and concentration dependence of both neutral and ion-induced nucleation for the canonical alpha-pinene + ozone system measured at the CERN CLOUD experiment between 223 and 298 K. Ultimately there are two competing effects: volatility drops as temperature drops, increasing saturation ratios, but the peroxy radical autoxidation chemistry that creates the highly functionalized ULVOCs accelerates as temperature increases, increasing saturation ratios in the opposite sense. Both theory and observations show a minimum in nucleation rates between 263 and 278 K, with higher rates to either side.
How to cite: Donahue, N. M.: Nucleation and the Volatility Basis Set, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21813, https://doi.org/10.5194/egusphere-egu26-21813, 2026.
Organic aerosol (OA) is a major component of tropospheric submicron aerosols, influencing air pollution, human health, and climate change. Primary and secondary OA (POA and SOA) exhibit distinct physicochemical properties that lead to different health and climate impacts. Current chemical transport models (CTMs), however, have difficulties not only in capturing OA concentrations, especially in polluted regions, but also in reproducing the fraction of POA and SOA. Here, we develop an OA simulation framework for full-volatility-range organic precursors, with a particular focus on improving OA formation from semivolatile and low-volatility organic compounds (S/LVOC) and intermediate-volatility organic compounds (IVOC), based on the atmospheric chemical transport model GEOS-Chem. Cooperating with a newly developed bottom-up global anthropogenic emission inventory, MEIC-global-FVOC, the improved OA scheme shows a good model performance when evaluated against a comprehensive dataset of worldwide measurements for OC, POA, and SOA, driven by increased POA formation from S/LVOC and SOA formation from IVOC. The model indicates that several populated regions in Asia, Africa, America, and Europe suffer from high OA exposure with annual mean over 5 μg m-3, highlighting the importance of controlling OA pollution. In East Asia, South Asia, the northern part of Africa, and Europe, anthropogenic SOA and POA are the largest two contributors to OA pollution, suggesting the need for reducing residential combustion that contributes over half of anthropogenic S/LVOC and IVOC emissions. For other regions, most of OA is from natural sources, which may be easily affected by extreme events (e.g., wildfires) and the warming climate. The estimated global OA burden in 2018 is 2.50 Tg, with a fraction of 75% from SOA. The SOA burden is higher than previous estimates, resulting from increased formation of S/LVOC and IVOC, highlighting that the role of SOA should be given more attention in assessing aerosol climate impact. The estimation of OA burden is sensitive to pyrogenic emission estimates and wet deposition parameterization, which need more constraints in future studies.
How to cite: Miao, R., Xu, R., Huang, S., Xiao, S., Wang, H., Zheng, Y., Liu, S., Li, J., Geng, G., Shrivastava, M., Haddad, I. E., Karydis, V. A., Tsimpidi, A. P., Zhang, Q., and Chen, Q.: Global budgets of atmospheric primary and secondary organic aerosols based on the simulation for full-volatility-range organic precursors, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11007, https://doi.org/10.5194/egusphere-egu26-11007, 2026.
Recent studies have shown that evaporation rates of secondary organic aerosol (SOA) particles may be slower than expected (Vaden et al. 2011; Berkemeier et al. 2020) and that growth rates of ambient SOA nanoparticles show surprisingly little dependency on condensable vapors in the gas phase (Kulmala et al., 2022). A large fraction of SOA may exist in oligomerized form, which might alter their condensation and evaporation. Additionally, SOA can be highly viscous, which leads to kinetic limitations in evaporation, slowing of particle-phase chemistry, and non-equilibrium partitioning. The effects of composition, oligomerization, and slow diffusion are inherently coupled, as high concentrations of low-volatility compounds or products of accretion reactions can cause high viscosity.
We use a kinetic multi-layer model to estimate the kinetic limitations affecting SOA formation and fate in laboratory experiments and the ambient atmosphere. The model explicitly considers gas- and particle-phase chemistry, kinetic gas-particle partitioning, and composition-dependent bulk diffusivity. We re-analyze data from laboratory chamber experiments with mixtures of terpenes as SOA precursors (Berkemeier et al. 2020) as well as published field and laboratory chamber data of nanoparticle growth (Stolzenburg et al., 2025) to find pronounced effects of multiphase chemistry and particle phase state under these conditions. Especially the partitioning of semi and low-volatile organic compounds (SVOC/LVOC) is strongly affected by these processes in the model, while the partitioning of extremely- and ultra-low volatility organic compounds (ELVOC/ULVOC) is less affected. We discuss the possible effect of growth limitation through bulk accommodation in models that follow monolayer adsorption schemes versus models that allow the “burying” of surface-adsorbed molecules through multi-layer adsorption.
The model predicts that, during particle evaporation, particles may be radially heterogeneous with respect to composition and diffusivity: higher volatility chemical species evaporate more quickly than oligomers or lower volatility species, leaving behind a near-surface layer crust of more viscous material that presents a barrier for further evaporation. The results highlight gaps in our knowledge about the physical and chemical properties of SOA and their interactions.
References
Berkemeier, T., Takeuchi, M., Eris, G., Ng, N. L. Atmos. Chem. Phys. 20, 15513-15535 (2020).
Kulmala, M., Cai, R., Stolzenburg, D., et al. Environ. Sci.: Atmos. 2, 352-361 (2022).
Stolzenburg, D., Sarnela, N., Bianchi, F. et al. npj Clim Atmos Sci 8, 75 (2025).
Vaden, T. D., Imre, D., Beranek, J., et al. P. Natl. Sci. Acad. USA 108, 2190–2195 (2011).
How to cite: Berkemeier, T., Kang, H. G., Zhang, Z., Radecka, M., Takeuchi, M., Ng, N. L., and Pöschl, U.: Interplay of phase state and multiphase chemistry in nanoparticle growth and evaporation of secondary organic aerosol, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19660, https://doi.org/10.5194/egusphere-egu26-19660, 2026.
Biogenic secondary organic aerosols (BSOA) are formed from oxidation of biogenic volatile organic compounds (BVOC). They are the main contributor to the global SOA fluxes with the values still remaining highly uncertain. The formation mechanism of BSOA has been studied extensively, however few studies up to date have been conducted at elevated relative humidity (85-95%) and in the presence of different aqueous inorganic seeds. These conditions are more realistic e.g., under night-time conditions or in coastal or tropical regions. As two typical and abundant BVOC, we focus on the SOA formation from isoprene and α-pinene. Experiments are conducted inside the AIDA aerosol and cloud simulation chamber under various humidities and the presence of different seed aerosols at atmospherically relevant conditions. During the campaign, NaCl, NH4NO3 or (NH4)2SO4 seed aerosol particles are introduced into the chamber, followed by the oxidation of isoprene or α-pinene. Formation and aging of oxidation products are measured in the gas and condensed phase in the dark and with simulated solar radiation.
Our results show that the SOA mass production is enhanced under higher relative humidities. High-resolution aerosol mass spectrometry data show a higher oxidation state of SOA formed under higher humidities, suggesting further oxidation of SOA products within the condensed phase. Further molecular analysis on the particle phase oxidation products with FIGAERO-CIMS suggests that the increased oxidation state can mainly be explained by the production of HOMs and low-molecular weight dicarboxylic acids during the aging process, especially under illumination. Our observations indicate the critical influence of relative humidity and pre-existing seed aerosol composition on different secondary organic aerosol formation mechanisms, particularly through potential aqueous-phase reaction pathways.
How to cite: Fu, J., Kroese, W., Novák, L., Ou, H., Holzinger, R., Saathoff, H., and Dusek, U.: Formation and aging of biogenic secondary organic aerosol in aqueous aerosol particles containing reactive nitrogen , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21608, https://doi.org/10.5194/egusphere-egu26-21608, 2026.
An important property of the compounds comprising organic aerosol is volatility, typically described in terms of saturation vapor pressure or saturation concentration (measured in µg/m3). The volatility of aerosol constituents can be estimated based on their molecular formula using different parametrizations or measured experimentally by using a chemical ionization mass spectrometer (CIMS) coupled to a filter inlet for gases and aerosols (FIGAERO). In this technique, aerosol sample is collected semi-online and evaporated via gradually heated nitrogen flow desorbing organic constituents to be measured by CIMS. From the temperature at which detected chemical species reach their maximum signal, it is possible to determine the respective compositions’ volatility.
In 2024, the FIGAERO-CIMS was deployed at the CHANEL (household chemicals amplifying urban aerosol pollution) measurement campaign at the SAPHIR chamber at Jülich Research Centre, Germany. During the campaign, complex reactive mixtures representing urban air scenarios were injected into the chamber, and exposed to both day- and night-time oxidation via opening or closing the roof to natural sunlight. We developed a multi-peak fitting algorithm to fully fit each composition’s thermogram (signal vs. desorption temperature), resulting in multiple nominal saturation concentrations per detected composition. We interpret these as combinations of simple volatility-driven desorption and decomposition (typically at higher temperatures) of larger compounds, such as accretion products.
We tracked the chemical composition and volatility of secondary organic aerosol throughout its formation and subsequent aging in the chamber over several hours. The chemical composition measured by FIGAERO-CIMS was compared with other co-located online mass spectrometric techniques, e.g., CIMS following online aerosol evaporation by a heated sheath flow (WALL-E). Our initial results show how aerosol volatilities typically decreased with age, as more oxygen was incorporated. Further, night-time conditions resulted in both increased organonitrate formation and lower product volatility relative to day-time conditions.
How to cite: Nissinen, A., Buchholz, A., Pullinen, I., Pusfitasari, E. D., Liu, L., Perrier, S., Riva, M., Roska, M., Yang, B., Bates, K. H., Coggon, M. M., Fry, J. L., Pfannerstill, E. Y., Rohrer, F., Stockwell, C., Tillmann, R., Khare, P., Bell, D., Gkatzelis, G. I., and Schobesberger, S. and the SAPHIR CHANEL: Organic aerosol volatility and its drivers in realistic urban air replicas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16772, https://doi.org/10.5194/egusphere-egu26-16772, 2026.
Considerable progress has been made in recent years in our understanding of the diffusivity of various species in viscous aqueous organic aerosol. However, little is known about ion diffusivity in such matrices. Here, we use experimental evaporation rates of volatile ammonium nitrate in a levitated, viscous proxy organic aerosol droplet to deduce the diffusivities of the nitrate and ammonium ions. We compare the ion diffusivities with those of semi-volatile maleic and malonic acid in the same proxy organic aerosol droplet. In addition, we measured viscosity of the proxies. Our finding indicates significantly slower diffusion of the ions compared to those of the organic acids, although the viscosity of the mixed solutions is comparable. Overall, the effective diffusivity of the ions seems to follow the Stokes-Einstein relationship, whereas the small organic acids diffuse faster than predicted. These findings have implications for the gas-particle portioning of ammonium nitrate which may be stronger limited by kinetic mass transfer than previously thought.
How to cite: Krieger, U., Klein, L., Luo, B., Bilde, M., and Peter, T.: Nitrate- and ammonium ion vs. dicarboxylic acid diffusivity in viscous organic aerosol particles: implications for gas-particle partitioning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3908, https://doi.org/10.5194/egusphere-egu26-3908, 2026.
Biomass burning is a major contributor to the global burden of secondary organic aerosol (SOA), with significant impacts on air quality, public health, and the Earth’s radiation balance. Observations from laboratory experiments and field campaigns increasingly show that intermediate-volatility organic compounds (IVOCs) emitted from wood combustion dominate SOA formation, potentially accounting for more than half of biomass-burning SOA (1,2). However, IVOC emissions and their atmospheric evolution remain highly uncertain and are often substantially underestimated in global chemistry–climate models, limiting our ability to accurately simulate organic aerosol distributions and trends. In this study, we quantify the sensitivity of biomass-burning SOA formation to key assumptions related to IVOC emissions, oxidation chemistry, and volatility distributions. We implement recent literature-based developments into ORACLE, the organic aerosol chemistry submodule of the EMAC global chemistry–climate model. ORACLE represents primary and secondary organic aerosol using a volatility basis set (VBS) framework, accounting for gas–particle partitioning, chemical aging through multigenerational oxidation, and changes in volatility and molecular mass during atmospheric processing (3). This framework enables a process-based evaluation of how uncertainties in emissions and chemistry propagate to global SOA burdens.
We perform a comprehensive suite of global sensitivity simulations for the period 2012–2016, corresponding to the most recent fully published GFED biomass-burning emission inventory and providing broad observational coverage for model evaluation. The sensitivity experiments address three major sources of uncertainty. First, we investigate alternative IVOC emission scaling approaches, including scaling IVOC emissions relative to emitted organic carbon (OC), as commonly assumed in global models (4), and scaling relative to volatile organic compound (VOC) emissions (5,2). These methods reflect differing assumptions about the relationship between IVOCs and primary combustion emissions and lead to substantially different global IVOC source strengths. Second, we assess uncertainties in SOA formation efficiency and chemical processing. This includes exploring reported ranges in aerosol mass yields under different NOx regimes (2), as recent experiments indicate that NOx strongly modulates SOA formation from biomass-burning IVOCs. In addition, we examine the sensitivity of modelled SOA to uncertainties in the OH reaction rate of IVOCs, which controls their atmospheric lifetime and spatial distribution. Third, we evaluate the influence of alternative volatility distribution of the IVOC oxidation products across VBS bins. Previous studies propose contrasting assumptions regarding whether the dominant SOA yield is associated with lower- or higher-volatility oxidation products (4,5), which leads to implications for SOA formation, transport, and lifetime.
By systematically disentangling the influence of IVOC emissions, chemical processing, and volatility assumptions, this work aims to identify parameterizations that are both physically representative of diverse biomass-burning conditions and computationally feasible for global applications. The results provide new constraints on biomass-burning SOA formation and support ongoing efforts to improve organic aerosol representation in global chemistry–climate models, thereby reducing long-standing discrepancies between simulated and observed SOA burdens.
References
(1) Bruns et al., 2016; doi: 10.1038/srep27881
(2) Li et al., 2024; doi: 10.1093/nsr/nwae014
(3) Tsimpidi et al., 2016; doi: 10.5194/acp-16-8939-2016
(4) Ciarelli et al., 2017; doi: 10.5194/gmd-10-2303-2017
(5) Tilmes et al., 2019; doi: 10.1029/2019MS001827
How to cite: Scholz, S. M. C., Khare, P., Gkatzelis, G. I., Chen, Q., Karydis, V. A., and Tsimpidi, A. P.: Improving global simulations of biomass-burning SOA through IVOC-focused sensitivity studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14197, https://doi.org/10.5194/egusphere-egu26-14197, 2026.
Wildfire smoke strongly affects air quality, human health, climate, and the Earth system. During atmospheric aging, wildfire aerosol particles undergo complex chemical and microphysical transformations that modify their optical properties, radiative effects, and cloud-forming ability. Of particular interest are organic surface coatings, which can enhance light absorption through lensing effects and increase particle hygroscopicity.
Here, we present single-particle mass spectrometry measurements from a boreal forest wildfire smoke experiment, resolving the coexistence of hydrophilic compounds and hydrophobic polycyclic aromatic hydrocarbons (brown carbon) within individual particles. We show that glyoxal and methylglyoxal are directly emitted during combustion, contributing to the initial hygroscopicity of freshly emitted particles. During photochemical aging, rapid oxalate formation is observed, accompanied by a moderate increase in hygroscopicity, while PAH signals decrease on a slower timescale. The decay rates of individual PAHs are similar but show a clear dependence on relative humidity, indicating that PAH degradation is controlled by viscosity-dependent radical diffusion into the particles. In contrast, highly oxidized products form on much shorter timescales, suggesting that these reactions are largely confined to the particle surface. At elevated relative humidity, surface oxidation continues, whereas it rapidly ceases under dry conditions. These observations highlight the central role of relative humidity in controlling the microphysical properties, optical effects, and cloud activation potential of aged wildfire smoke.
How to cite: Zimmermann, R., Rosewig, I. E., Kalamašņikovs, A., Hakkim, H., Ihalainen, M., Hartikainen, A., Somero, M., Yli-Pirilä, P., Sippulä, O., Peltokorpi, S., Buchholz, A., Liqing, H., Virtanen, A., Vakkari, V., Walte, A., and Passig, J.: The role of relative humidity for the formation of oxidized shells on aged wildfire particles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18015, https://doi.org/10.5194/egusphere-egu26-18015, 2026.
Key-words: Carbonaceous aerosol, WSOC, Molecular-level characterization, radiative-forcing, Semi-arid region
Carbonaceous aerosols are a major component of atmospheric fine particulate matter and play a crucial role in climate forcing due to their light-absorbing properties. Their influence on wintertime radiative forcing is particularly pronounced, while the source-specific absorption and molecular properties remain poorly understood in semi-arid regions1. To address this knowledge gap, we conducted a 24-hr three-week PM2.5 winter campaign in a semi-arid urban region of northwestern India. We performed measurement of BC concentration using multi-wavelength AE-33, filter-based elemental carbon-organic carbon (EC–OC) analysis, water-soluble organic carbon (WSOC) quantification and brown carbon (BrC) optical characterization, and molecular characterization of isolated HULIS fractions (HULIS-A at pH=2 and HULIS-N at pH=7) using UHPLC-ESI-ToF-MS.
eBC remained consistently elevated, with most daily mean values above 15 µg/m3 and episodic peaks exceeding 26 µg/m3, indicating sustained wintertime loading. Fossil-fuel derived BC (BCff) dominated throughout the day, with early-morning (12.61 µg/m3) and evening (15.52 µg/m3) peaks, 2.84–15.52 µg/m3, while biomass-burning BC (BCbb) showed characteristic morning and late-evening enhancements of 8–11 µg/m3, consistent with residential biomass or wood burning in colder periods. Further, we observed WSOC/OC ratio of 0.75–0.80 with average WSOC levels of 35 µg/m3. A strong near-UV absorption, with SUV254 (MAC254 ≈ 5.0–5.2 m2/g) and MAC254 > 5 m2/g, along with a high AAE (4.04) confirmed the presence of strongly light-absorbing BrC from biomass-burning precursors and secondary processing2,3.
The molecular characterization of HULIS showed that CHO- and CHON-rich ions were present not only in the semi-volatile oxygenated organic aerosol (SVOOA) domain but also in regions associated with biomass-burning organic aerosol (BBOA). This indicates the simultaneous presence of both primary BB products and secondarily aged organics. HULIS-A exhibited stronger near-UV absorption, confirming its dominant contribution to wintertime chromophores. In DBE–NC space, HULIS-A displayed a much broader distribution compared to HULIS-N, extending into regions characteristic of unsaturated aromatics, phenolic and nitro-aromatic BrC precursors, and cata-PAH-like structures, all of which are known carriers of strong near-UV absorption.
Together, the optical measurements (MAC spectra, UV–Vis absorption) and high-resolution molecular analysis indicate that wintertime WSOC at this semi-arid site is strongly enriched in both primary BBOA-linked chromophores and secondary OOA-derived oxygenated species. Among these, HULIS-A emerges as the principal carrier of light-absorbing organic matter, driving enhanced shortwave absorption during winter.
References:
(1) Laskin, A.; Laskin, J.; Nizkorodov, S. A. Chemistry of Atmospheric Brown Carbon. Chem. Rev. 2015, 115 (10), 4335–4382. https://doi.org/10.1021/cr5006167.
(2) Weishaar, J. L.; Aiken, G. R.; Bergamaschi, B. A.; Fram, M. S.; Fujii, R.; Mopper, K. Evaluation of Specific Ultraviolet Absorbance as an Indicator of the Chemical Composition and Reactivity of Dissolved Organic Carbon. Environ. Sci. Technol. 2003, 37 (20), 4702–4708. https://doi.org/10.1021/es030360x.
(3) Hecobian, A.; Zhang, X.; Zheng, M.; Frank, N.; Edgerton, E. S.; Weber, R. J. Water-Soluble Organic Aerosol Material and the Light-Absorption Characteristics of Aqueous Extracts Measured over the Southeastern United States. Atmospheric Chem. Phys. 2010, 10 (13), 5965–5977. https://doi.org/10.5194/acp-10-5965-2010.
How to cite: Gupta, A., Shrivastava, A., and Bhattu, D.: Wintertime Molecular and Optical Properties of Carbonaceous Aerosols in a Semi-Arid Environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2513, https://doi.org/10.5194/egusphere-egu26-2513, 2026.
It has been predicted that boreal forest and peatland fires will increase in the future as the climate warms. It is important for climate models that the optical properties of the aerosols emitted during these fires are well described. Laboratory experiments were carried out to study biomass burning (BB) aerosol emissions and their photochemical and dark aging to investigate (1) the emission factors of BrC (and BC) from different combustion processes, (2) chemical and optical properties of the emissions and (3) how different atmospheric aging conditions affect these properties. The experiments were performed at the ILMARI-facility of the UEF (www.uef.fi/ilmari) in November–December 2023. Details of the experiments were presented by Mukherjee et al. (2025) who also presented absorption properties of water-soluble and methanol-soluble organic carbon (WSOC and MSOC, respectively) analyzed from filter samples. In the present work we will present the optical properties of BB emissions from burning peat and dry and moist boreal forest floor surface (BFS) samples at high time resolution. Light scattering coefficient was measured with a 3-wl nephelometer, absorption with a 7-wl Aethalometer and a 3-wl photoacoustic spectrometer, and particle number size distributions (PNSD) with an SMPS. A Mie code was used for calculating scattering and absorption coefficients from the PNSDs by varying real and imaginary refractive indices (nr and ni, respectively), until the measured and modeled scattering and absorption agree within 1%. The flaming BB emissions were dark with single-scattering albedo (SSA) varying between 0.25 and 0.6. The darkest aerosols with SSA ≈ 0.30 ± 0.05 were measured from flaming dry BFS and the highest SSA > 0.95 from aged peat fires. Fitting lines with the nr vs SSA show that the real refractive indices can be estimated from a logarithmic function nr(450) = 0.191ln(SSA) + 1.792, r2 = 0.402; nr(525) = 0.218ln(SSA) + 1.773, r2 = 0.524; nr(635) = 0.295ln(SSA) + 1.862, r2 = 0.734 and the imaginary refractive indices from polynomials: ni(450) = -4.50SSA3 + 10.35SSA2 - 8.05SSA + 2.17, r2 = 0.97; ni(525) = -2.91SSA3 + 6.79SSA2 - 5.40SSA + 1.51, r2 = 0.98; ni (635) = -1.65SSA3 + 3.85SSA2 - 3.16SSA + 0.96, r2 = 0.98. The next steps are to calculate the mass absorption cross sections (MAC) of BC and BrC by combining the optical data with the soot particle aerosol mass spectrometer (SP-AMS) data and the absorption coeffcients and refractive indices of WSOC measured with an online UV-IR spectrometer connected to a liquid-waveguide capillary cell (LWCC) and a particle-into-liquid sampler (PILS).
Reference
Mukherjee, A. et al.: Brown carbon emissions from laboratory combustion of Eurasian arctic-boreal and South African savanna biomass, Atmos. Chem. Phys., 25, 16747–16774, 2025
Acknowledgement
This work was supported by the Research Council of Finland via the project “Black and Brown Carbon in the Atmosphere and the Cryosphere” (BBrCAC) (decision number 341271)
How to cite: Virkkula, A., Li, D., Barreira, L., Hartikainen, A., Somero, M., Kokkola, T., Mukherjee, A., Karhu, J., and Sippula, O.: Single-scattering albedo and iterated refractive indices of fresh and aged black and brown carbon particles emitted from burning peat and boreal forest floor surface in chamber experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15338, https://doi.org/10.5194/egusphere-egu26-15338, 2026.
Posters on site: Tue, 5 May, 16:15–18:00 | Hall X5
This study investigates how biogenic volatile organic compound (BVOC) emissions from boreal forests shape aerosol evolution and subsequent cloud formation, with a focus on the vertical pathway of air parcels and repeated cloud processing. Using long-term aerosol observations from SMEAR II (Finland), we characterize how aerosol size distribution and chemical composition evolve during atmospheric transport and aging. These observations are used to drive simulations with the PseudoAdiabatic bin-micRophySics University of Exeter Cloud parcel model (PARSEC) to assess impacts on cloud droplet activation, supersaturation, and cloud albedo.
We examine how forest emissions influence aerosol growth, composition, cloud condensation nuclei efficiency, and, therefore, cloud microphysics. Particular focus is placed on the role of vertical transport and precipitation processing in shaping aerosol–cloud interactions. The long-term observations reveal that the longer aerosols spend over forests, the more they grow and change in composition. Our simulation results then show that these changes in BVOC-driven aerosol properties impact droplet activation, cloud formation, and cloud microphysic highlighting how BVOC-emission and aerosol aging impact cloud responses.
These findings emphasise the need to represent not only surface emissions but also the full atmospheric processing pathway of aerosols in climate models, especially when assessing the climatic role of forested regions. This study will lead to a comparison between Tropical and Boreal ecosystems impact on aerosol aging and the difference in cloud responses.
How to cite: Faivre, L., Krejci, R., Tunved, P., Khadir, T., Bowen, P., Partridge, D., and Heikkinen, L.: The Journey from Forest Emissions to Clouds: Aerosol aging impact on cloud microphysics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19949, https://doi.org/10.5194/egusphere-egu26-19949, 2026.
Keywords: Source Apportionment, SOA, Biomass Burning, PMF, Aerosol Composition, Haze
This study investigates seasonal evolution of aerosol physicochemical properties and source influences in the upwind region of Delhi-NCR using a suite of state-of-the-art instruments deployed at Sonipat, Haryana, India (28.9° N, 77.1° E). Continuous measurements of non-refractory PM₂.₅ using a Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) and black carbon (BC) using an Aethalometer (AE-31) were conducted during the peak stubble-burning and Diwali period (25 Oct 2023 to 15 Nov 2023), a time characterized by strong episodic pollution events and regional transport influence. The observational period captured three contrasting regimes: (i) an initial non-haze phase (mean PM₂.₅: 218±90 ug/m3), (ii) an intense haze episode linked to crop-residue burning and meteorological stagnation (haze1: 507±217 ug/m3), followed by a rain-driven dilution event (non-haze2: 166 ±70 ug/m3), and (iii) a a subsequent Diwali-driven haze event (haze2: 311±140 ug/m3). Across all conditions, non-refractory PM₂.₅ was dominated by organic aerosols (OA: 66.9%), with secondary inorganic species such as nitrate (NO3−: 8.4%), sulfate (SO42−:4.7%), ammonium (NH4+:6.6%), and chloride (Cl−:2.3%), contributing modest fractions. Positive Matrix Factorization (PMF) and Multilinear Engine (ME-2) analysis resolved five distinct OA sources: traffic-related hydrocarbon-like OA (HOA), biomass-burning OA (BBOA), solid fuel combustion OA (SFC-OA), two oxygenated OA components, less oxidized OA (LOOA) and more oxidized OA (MOOA) comprising 37.8% of total OA, indicative of extensive aging during transport. Among primary sources, SFC-OA (23%) and BBOA (11.2%) were most enhanced during pollution episodes, consistent with emissions from wood burning and post-harvest crop-residue fires. Aethalometer-derived BC source apportionment showed a relative decline in fossil–fuel BC during both haze phases, highlighting the strong episodic influence of biomass-burning plumes. Meteorological analysis indicates that the extreme haze1 event was amplified by a pronounced reduction in boundary-layer height and aerosol–radiation feedback, which suppressed vertical mixing and reinforced pollutant accumulation. Aerosols during haze1 exhibited high oxidation states and enhanced aging, pointing to prolonged atmospheric processing and regional transport from source regions upwind of Delhi–NCR. These findings provide a process-level understanding of aerosol evolution during high-pollution periods, illustrating the combined roles of emission variability, atmospheric aging, and meteorological feedback in shaping air quality over the Indo-Gangetic Plain.
How to cite: Singh, V., Ganguly, D., Rathore, J., Gani, S., and Dey, S.: Insights into Aerosol Composition, Source Signatures, Chemical Aging, and Transport Dynamics in Delhi–NCR from High-Resolution In-Situ Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-937, https://doi.org/10.5194/egusphere-egu26-937, 2026.
Understanding the interactions between PM2.5 and its gaseous precursors in agricultural environments is essential for designing effective air quality control strategies. In this study, long-term observations were carried out at eight agricultural monitoring sites across South Korea to investigate the relationships among PM2.5, its major precursor gases (NH3, NO2, and SO2), and meteorological factors. Both concentration-based metrics and loading-rate approaches, which incorporate wind-driven transport, were applied for comparative analysis. The concentration-based analysis yielded generally weak and unstable correlations, largely attributable to atmospheric dispersion and dilution effects. In contrast, loading rates exhibited consistently strong and statistically significant associations among PM2.5 and precursor gases (R ≥ 0.816, p < 0.001), indicating their enhanced capability to represent emission–transport interactions. Clear seasonal and diurnal variations were observed for all pollutants, with summer showing distinctly different daily patterns compared to other seasons. Notably, loading-rate maxima systematically lagged behind meteorological peaks by approximately two hours. Ammonia displayed an earlier and more pronounced diurnal signal than other precursors, primarily driven by temperature-dependent volatilization associated with soil–air temperature gradients. Principal component analysis revealed that PM2.5 loading rates were closely aligned with SO2 and NO2, whereas NH3 formed a separate structure, reflecting its different emission timing. Multiple linear regression further identified SO2 as the dominant contributor to PM2.5 formation, followed by NO2, while NH3 exhibited a negative relationship due to its temporal offset from PM2.5 peaks. Overall, this study demonstrates that loading-rate-based analysis provides a more robust framework for elucidating PM2.5–precursor interactions in agricultural regions and offers improved scientific support for developing targeted mitigation strategies.
Acknowledgments
"This research was supported by Particulate Matter Management Specialized Graduate Program through the Korea Environmental Industry & Technology Institute(KEITI) funded by the Ministry of Environment(MOE)"
How to cite: Baek, J., Bae, S.-H., and Joo, H.: Correlation analysis between precursor gases and fine particles in agricultural area, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3629, https://doi.org/10.5194/egusphere-egu26-3629, 2026.
Oligomeric esters, including ”dimer esters” (molecular weight 300-450 Da), are one of the components of secondary organic aerosol (SOA) and account for around 0.5-1.5 % of ambient SOA mass. Esters are low-volatile (LVOCs) or extremely low-volatile organic compounds (ELVOCs), built from derivatives of terpenoic acids. They are primarily concentrated in the particle phase.[1, 2] Oxidation via ozonolysis of monoterpenes (C10H16) at night is known as the primary source of esters in the atmosphere.[3] Additionally, esters play a crucial role in Cloud Condensation Nuclei (CCN) and have a significant impact on particle formation and growth. On the other hand, many compounds are not fully characterised or unreported, and an accurate surrogate standard has yet to be proposed.
Our research is focused on ester formation via ozonolysis and OH*-oxidation of α- and β-pinene in laboratory and ambient SOA. The aim is to identify and describe dimer esters in both analysed environments, with an emphasis on previously unknown substances. Also, the C19H30O6 ester will be studied as a surrogate standard. Laboratory-derived and ambient aerosol samples were collected from the aerosol chamber at the Leibniz Institute for Tropospheric Research in Leipzig (TROPOS) and during field campaigns at two forest sites in Poland: Kampinos National Park and Borecka Forest. Water was used as the solvent for the extraction of the aerosol sample. All analyses were performed using an ultra-high-performance liquid chromatograph coupled with a mass spectrometer (UHPLC-MS), with an ElectroSpray Ionisation (ESI) source and Quadrupole Time-of-Flight (QToF) detector.
Overall, during qualitative analysis, 39 esters were identified in laboratory-derived aerosol samples. For all compounds, chemical formulas were matched or established. For some compounds, new structures were predicted. Despite the complex nature of environmental aerosol, quantitative analysis (performed on 15 substances) reveals traces of esters in ambient SOA, where ester C19H28O7 was the most abundant, with a concentration of approximately 0.5 ng×m-3. However, larger amounts of different esters were detected in laboratory-derived SOA. Experiments in a laboratory environment have shown that C16H30O11, C15H30O10 and C19H28O7 are the most common, with amounts reaching 0.7 µg×m-3. Concentrations were established by using a calibration curve based on C19H30O6, providing results that matched well with the expected ester quantities in the SOA.
References:
[1] K. Kristensen et al., Environ. Sci. Technol. Lett., 2016, 3, 280−285
[2] C.M. Kenseth et al., Environ. Sci. Technol., 202054, 12829−12839
[3] C.M. Kenseth et al., Science, 2023, 382, 787-792
How to cite: Jaworucki, P., Błaziak, A., and Michalak, M.: Qualitative and quantitative analysis of terpene-derived esters in laboratory-generated and ambient secondary organic aerosol (SOA), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10305, https://doi.org/10.5194/egusphere-egu26-10305, 2026.
The high abundance of ultrafine particles (PM0.1) in the atmosphere not only implies significant interaction with the already critical climate system, but is also associated with severe health risks. The chemical composition of ultrafine particles is not only decisive for their specific health effects but also carries information on the dominant sources of these particles. However, chemical composition analysis techniques of sub-100 nm particles are currently either complex or high-cost, limiting their applicability to large-scale environmental source attribution.
Nanoelectromechanical sensors coupled to a Fourier transform infrared spectrometer, short NEMS-FTIR, is a promising tool for large-scale chemical characterization of ultrafine aerosol particles. It provides a high sensitivity down to few picograms of sample coupled with easy-to-use sampling directly onto the sensor, and subsequent high throughput analysis at a centralized facility equipped with the IR-spectrometer.
However, a fundamental step towards the quantification of the chemical composition of ultrafine aerosol samples and related source attribution is the calibration of the sampling system with known functional-group abundance such that IR signals can be translated into quantitative chemical composition data. Here we show the characterization of NEMS for the usage in the sub-100 nm range, enabling the quantification of functional group abundances in ultrafine aerosol samples.
Using particle number measurements in a simple transmission experiment we show that the size-dependent particle collection efficiency of the NEMS-chips is in the order of around 50% in the sub-100 nm range. The collected ultrafine mass on the filters is verified through ion chromatography and then used to obtain functional group-specific calibration coefficients translating infrared absorbance units into abundance of functional groups. We find detection limits e.g., well below 1 ng of collected ammonium sulfate.
The knowledge of the resulting calibration curves of individual organic and inorganic compounds will enable chemical composition analysis, which we showcase here with selected ambient air measurements from two very different environments: Vienna, Austria and the highly-polluted station in Sonipat, India, close to New Delhi. The long-term goal focuses on the application of functional group analysis on a bigger amount of ambient air samples covering a broad temporal range, which ultimately enables source apportionment through Positive Matrix Factorization.
How to cite: Czermak, B., Luhmann, N., Hiesberger, J., Riedelberger, T., Kasper-Giebl, A., Lafleur, J., and Stolzenburg, D.: Quantifying functional group abundances of ultrafine aerosol particles with a NEMS-FTIR system for source attribution studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10572, https://doi.org/10.5194/egusphere-egu26-10572, 2026.
Secondary organic aerosols (SOA), produced via the oxidation of gaseous precursor compounds in the atmosphere, contribute a substantial fraction of atmospheric airborne particles and affect both air quality and climate. Global aerosol-climate models often suffer from very simplified representations of atmospheric SOA formation or missing formation pathways, typically leading to underestimated SOA particle numbers and mass contributions in comparison to observational data. Here, we use the aerosol microphysics submodel MADE3 as part of the global chemistry-climate model EMAC and implement an improved scheme for SOA formation. While MADE3 in its previous version did not account for new particle formation from organic precursors, we included the nucleation parametrization for SOA particles from monoterpene precursors described in Riccobono et al. (2014), which depends on the concentration of sulfuric acid and oxidized organic molecules. Additionally, we consider isoprene as biogenic SOA precursor for the condensation on pre-existing particles, which has been neglected in the previous model version. In addition to biogenic precursors, we also consider anthropogenic precursors for SOA formation, e.g. benzene, toluene, and xylenes from anthropogenic activities like the combustion of fossil fuels. Particle nucleation from these anthropogenic precursors is parametrized similarly to the Riccobono et al. (2014) scheme. We show the effect on particle numbers and SOA mass fractions when using the new SOA scheme and evaluate our simulation results against various observational data sets. When the nucleation parameterization for monoterpene precursors is activated, the total near-surface number concentrations can increase regionally by up to one order of magnitude. With the new SOA scheme, the underestimation of particle numbers and SOA mass fractions in the lower troposphere is reduced and results show an improved agreement with observations.
References:
Francesco Riccobono et al., Oxidation Products of Biogenic Emissions Contribute to Nucleation of Atmospheric Particles. Science 344, 717 721 (2014). DOI: 10.1126/science.1243527
How to cite: Beer, C., Hendricks, J., Righi, M., Carslaw, K., and Grosvenor, D.: Simulating secondary organic aerosol formation in a global aerosol-climate model , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10635, https://doi.org/10.5194/egusphere-egu26-10635, 2026.
We conducted aircraft-based aerosol composition measurements in the upper troposphere (UT) over the Amazonian rainforest using the HALO research aircraft during the CAFE-Brazil (Chemistry of the Atmosphere – Field Experiment in Brazil) mission. In December 2022 and January 2023, a compact time-of-flight aerosol mass spectrometer (C-ToF-AMS; Schulz et al., 2018) was operated on 22 flights (including test and ferry flights) at altitudes up to 14 km. The measurements show that organic compounds dominate the aerosol composition in the tropical UT, with a significant contribution from organic nitrates. Organic nitrates can form during secondary organic aerosol (SOA) production via reactions of volatile organic carbon (VOC) precursors (e.g., isoprene) with OH and/or O3 in the presence of NOx. NOx is observed to be abundant in the tropical UT (NO up to 300 pptv; Nussbaumer et al., 2024) with a major source of frequent lightning activity in convective thunderstorms, and the low temperatures aloft appear to favor organic nitrate formation (Curtius et al., 2024).
To distinguish inorganic from organic particulate nitrate, we use the NO2+ (m/z 46) and NO+ (m/z 30) ion ratio in the C-ToF-AMS mass spectra, which has been shown to indicate the presence of organic nitrates (e.g., Day et al., 2022). Inorganic ammonium nitrate, used for calibration, exhibits a markedly higher NO2+/NO+ ratio than organic nitrates. Our data show that in the UT, as sampled here at altitudes above 10 km, nitrate is predominately present as ammonium nitrate in the extratropics (> 23° N), whereas in the tropics (< 23° N), nitrate occurs mainly as organic nitrate. The ferry flights between Germany and Brazil clearly capture this transition when entering and leaving the tropical region.
Organic nitrates have also been identified as a key component in new particle formation from isoprene in the UT over the Amazon (Curtius et al., 2024; Shen et al., 2024; Russell et al., 2025). As the C-ToF-AMS detects particles larger than about 50 nm, our observations indicate that organic nitrates are essential not only for new particle formation but also for the subsequent particle growth in the tropical UT. They therefore represent a major source of cloud condensation nuclei for the middle and lower troposphere in tropical regions.
Curtius, J., et al.: Isoprene nitrates drive new particle formation in Amazon’s upper troposphere, Nature, 636, 124-130, 2024.
Day, D. A., et al.: A systematic re-evaluation of methods for quantification of bulk particle-phase organic nitrates using real-time aerosol mass spectrometry, Atmos. Meas. Tech., 15, 459–483, 2022.
Nussbaumer, C., et al.: Ozone Formation Sensitivity to Precursors and Lightning in the Tropical Troposphere Based on Airborne Observations, J. Geophys. Res., 129, e2024JD041168, 2024.
Russell, D. M., et al.: Isoprene chemistry under upper-tropospheric conditions, Nature Comm., 16, 8555, 2025.
Schulz, C., et al.: Aircraft-based observations of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX-SOA) in the tropical upper troposphere over the Amazon region, Atmos. Chem. Phys., 18, 14979-15001, 2018.
Shen, J., et al.: New particle formation from isoprene under upper-tropospheric conditions, Nature, 636, 115-123, 2024.
How to cite: Schneider, J., Kaiser, K., Joppe, P., Hartmann, A., and Cheng, Y.: Organic nitrates in upper tropospheric aerosol: Results from airborne measurements over the Amazon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11668, https://doi.org/10.5194/egusphere-egu26-11668, 2026.
Oxidation flow reactors (OFRs) are widely used in atmospheric chemistry research to investigate the oxidation of volatile organic compounds (VOCs) and the formation of secondary organic aerosol (SOA). By generating highly oxidizing environments, OFRs enable simulation of hours to days of atmospheric photochemical aging within minutes of real time. Traditionally, oxidants are produced via ozone photolysis using low-pressure mercury discharge lamps. While effective, these lamps present several drawbacks, such as mercury-related environmental, health, and disposal concerns, inefficient, non-directional radiation, significant heat generation, and limited operational lifetime.
Here, we present a novel OFR design employing UVC light-emitting diodes (LEDs) as the photolysis source. Four modules, each equipped with 12 LEDs emitting at 265 nm (Violumas, VC12X1C48LC-265), are mounted around a quartz glass tube with a conical stainless steel inlet and outlet. The minimized radiative heat input from UVC LEDs enables a larger reactor design with an internal volume of 20.5 L (glass tube: length = 40 cm, diameter = 20 cm) by reducing buoyancy-driven convection. Thereby, laminar flow conditions with a typical residence time of ~ 4 minutes (adjustable via input flows) can be achieved, and wall interactions are minimized. Humidified air (RH = 30 %), ozone, and the sample of interest are introduced into the OFR, where ozone photolysis generates OH radicals, confirmed through toluene oxidation experiments. Particle size distributions and ozone concentrations are monitored at the outlet, where particles are also collected on filters. Transmission efficiency was characterized using PSL particles (100, 300, 460 nm) and two CPCs, showing > 80 % transmission, with UVC irradiation and heat generation having no measurable impact.
A movable core-sampling tube is coupled to a multi-scheme chemical ionization (MION2) Orbitrap mass spectrometer, enabling ultra-high-resolution measurements of oxygenated molecules. Experiments on α-pinene and limonene ozonolysis, as well as VOCs from cleaning products and bitumen, demonstrate the versatility of the setup for studying the simulated atmospheric oxidation and new particle formation (NPF) potential of these substances - critical for understanding urban emissions of growing relevance.
With higher efficiency, directional light output, superior thermal management, extended operational lifetime, and enhanced usability compared to conventional mercury lamps, UVC LEDs represent a significant advancement toward safer, more sustainable, and more controllable OFR technology for atmospheric chemistry applications.
How to cite: Tischberger, M., Verma, R., Papp, E., Grothe, H., and Stolzenburg, D.: Advancing oxidation flow reactor technology: Simulating atmospheric oxidation with UVC LEDs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14388, https://doi.org/10.5194/egusphere-egu26-14388, 2026.
Sugar acids such as gluconic, glucuronic, and galacturonic acids are emitted directly by biomass burning, vegetation, and microbiota, and are formed through the oxidation of sugars and sugar alcohols. These compounds are commonly found in atmospheric particulate matter (PM), particularly in biomass burning and biogenic secondary organic aerosols. Hydroxyl radical (OH) is a major daytime atmospheric oxidant, formed by photolysis of ozone (gas phase) and by Fenton or Fenton-like reactions in water-containing particles, thereby dominating the oxidative capacity of the atmosphere.
Due to their extremely low volatilities and high water solubility, the aqueous reaction with the OH radicals inside the different hydrometeors can contribute to the transformation and removal of saccharides. As such, aqueous OH radicals' reaction with polyols influences particle aging, secondary oxidation processes, and changes in aerosol chemical and optical properties relevant to regional climate.
The values of bimolecular reaction rate coefficients (kOH, M-1s-1) for the atmospherically abundant, water-soluble organic compounds (WSOCs) are needed to estimate their atmospheric lifetimes and develop kinetic predictive models, particularly structure-activity relationships (SARs). Kinetic SARs are widely used in atmospheric chemistry to predict kOHaq for the atmospheric-abundant water-soluble organics; they are also frequently embedded in atmospheric models and automated mechanism generators. At the same time, the number of kOH values for many (poly)functional, highly polar organic compounds found in the atmospheric multiphase system remains limited.
In this work, kOH values for gluconic, glucuronic, and galacturonic acids were systematically measured at temperatures using a laser flash photolysis-laser long-path spectroscopy. Measurements were conducted over a temperature range 278 to 318K under acidic (pH=2) and neutral (pH=7) conditions. The kOH values were determined at five reactant concentrations, ranging from 5.0×10-5 to 2.0×10-4 M, using potassium thiocyanate (KSCN, 2×10-5M), as a kinetic reference compound. The resulting kOH values ranged from 108 to 109 M-1 s-1, consistent with available literature data for similar polyols. All three sugar acids exhibit a clear temperature dependence of the measured kOH values, following Arrhenius behavior.
Arrhenius analysis yielded activation energies (EA, kJ mol-1), pre-exponential factors (A, M-1 s-1), activation enthalpies (∆H‡, kJ mol-1), activation entropies (∆S‡, J K-1 mol-1), and Gibbs free energies of activation (∆G‡, kJ mol-1). These results provide mechanistic insights into the OH reaction with sugar acids. Lastly, the performances of different kinetic SARs for highly oxygenated WSOCs were evaluated using the newly acquired data.
How to cite: Nguyen, V., Schaefer, T., Witkowski, B., Gierczak, T., and Herrmann, H.: Aqueous OH kinetics of sugar acids: new rate coefficients and atmospheric lifetimes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18839, https://doi.org/10.5194/egusphere-egu26-18839, 2026.
Open biomass burning across different regions of the world is a major source of gaseous and fine-mode particulate species emitted into the atmosphere. Post-monsoon crop residue fires of North-West (N-W) India continues to have significant contribution to global burned area estimates (GloCAB product – Hall et al., 2024) and air quality impact in downwind urban cities of Indo-Gangetic Plain (IGP) including megacity Delhi. Yet, detailed in-situ observations of the fire smoke’s evolution and emission characteristics near the source are lacking and largely remain uncertain. We conducted STUB-BURN (Stubble Burning emissions study) measurements characterizing speciated fine particulate matter and related gaseous species via a mobile research platform in rural Punjab from 27 Oct to 18 Nov 2023. We observed rapid oxidation of OA with more than half dominated by oxygenated form of OA even in near-source field sampling conditions. By combining organics, metals, and black carbon (BC) in source apportionment technique, roughly ~ 50% is attributed to ongoing crop residue burning. Further, varying contribution of primary and aged OA factors were found in identified nine individual plume events. However, the dilution corrected enhancement ratio of OA w.r.t CO shows no net increase or decrease in mass enhancement with increasing O:C values as an indicator of ageing. Emission factors (EFs) of 17 species are calculated and their variability with global averages used in global fire emission estimates for this region are highlighted. Broadly, obtained EFs under open field scale combustion conditions for major species are up to three-fold lower than average estimates from widely used fire emission inventories. Overall, this study reinforces the need to account for fire characteristics that govern subsequent emissions to represent regional contributions more accurately within global emission estimates.
How to cite: Pandey, A., Singh, V., Ali, U., Faisal, M., Kumar, A., Goel, V., Hao, Y., Mor, S., Ravindra, K., Daellenbach, K., Prevot, A., and Kumar, M.: Near-source emission profiling of post-monsoon crop residue fires in N-W India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-971, https://doi.org/10.5194/egusphere-egu26-971, 2026.
Isoprene (ISO) is a key atmospheric biogenic volatile organic compound (BVOC) due to its high emissions and reactivity. While OH radical-initiated oxidation is the main ISO degradation pathway, ISO ozonolysis is also a non-negligible pathway. Moreover, ISO ozonolysis produces OH radicals, further enhancing ISO oxidation under low actinic flux conditions. More importantly, the stabilized Criegee intermediate (sCIs) generated from the ozonolysis of ISO is an underappreciated yet crucial atmospheric oxidant. It can undergo oxidation reactions similar to those of OH radicals and produce low-volatility organic acids and other carbonyl compounds, which act as precursors to secondary organic aerosols (SOA). Recently, monomers of CIs have been detected in SOA from tropical rainforests, suggesting that CIs can directly participate in SOA formation through 1,2-insertion reactions. In this work, we developed a new technique based on atmospheric pressure interface chemical ionization mass spectrometry (CI-API-CIMS) to conduct in-situ measurements of sCIs after chemical derivatization. The CI-API-CIMS was field tested in summer 2025 at a forest site in Chengdu, China. VOCs and particulate organic matter were concurrently measured by a PTR-MS and an HR-ToF-AMS. Observations revealed that suspected sCIs fragments were highly correlated with gaseous sCIs and organic acids. These observations were consistent with our existing understanding of sCIs, providing supporting evidence for the mechanism by which sCIs directly participate in SOA formation. A 0-D box model was also developed to verify these findings.
How to cite: Zheng, J.: Field observations of isoprene ozonolysis contributing to SOA formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6104, https://doi.org/10.5194/egusphere-egu26-6104, 2026.
Intermediate and semivolatile organic compounds (IVOC and SVOC) play a pivotal role in atmospheric secondary organic aerosol (SOA) formation, contributing substantially to fine particulate matter that impacts air quality, climate, and human health. Anthropogenic IVOC, such as hydrocarbons from diesel vehicle emissions, undergo rapid oxidation to yield low-volatility products that partition into aerosols. Similarly, also biogenic IVOC and SVOC like sesquiterpenes emitted from plants enhance SOA yields in forested regions. Quantifying their contributions to SOA formation remains challenging due to detection limitations, underscoring the need for advanced analytical methods.
To elucidate the atmospheric fate of IVOC and SVOC, we herein combine a dynamic volatility separation technique with a novel flow-reactor for rapid photochemical oxidation and two FUSION PTR-TOF instruments (IONICON Analytik, Austria) for characterizing gas-phase and condensed organic compounds.
The gas-phase volatility separation technique was recently introduced by Morris et al. (2024). This method utilizes the well studied absorption processes of low volatiles onto polymer tubing to separate volatility classes. Hence, via dynamic addition and removal of absorbing polymer tubing, a defined fraction of SVOC and IVOC can be efficiently removed from complex mixtures as present in ambient air. We further improved this method by using an actively cooled conductive PTFE inlet as a volatility separator. Hence, the volatility cutoff to organic precursors can be precisely adjusted by temperature without the need to switch between different types of polymer.
To study the SOA formation potential with and without IVOC and SVOC, this optimized volatility separator is periodically added prior to injection of ambient air into the novel IONICON Laminar-flow Oxidation reactor (ILOx) for rapid photochemical ageing. ILOx’s design allows for transmitting particles, IVOC and even SVOC with lowermost losses. All wetted surfaces are passivated, providing best response times, even for reduced volatility gas-phase organics.
The ambient air pre and post ILOx is analyzed by two FUSION PTR-TOF, one equipped with a CHARON particle inlet, and a SMPS system (Grimm Aerosol Technik, Germany). For gas-phase measurements, the instruments cover the volatility range from VOC to SVOC and offer limits of detection in the range of 100 ppqV. With the CHARON particle inlet also condensed organics are detected on a molecular composition level at highest analytical precision and lowermost limits of detection (~20 pg/m³).
In this presentation we will highlight the capabilities of this new method with an example of a morning rush-hour event in Innsbruck, Austria. Hydrocarbons and aromatic hydrocarbons emitted by vehicles are significantly elevated. Most of these traffic related volatile organics can be classified as volatile and only approximately 13% can be attributed to IVOC and SVOC. Our method allows us to precisely quantify the contribution of this relatively small fraction to the potential SOA formation, revealing an overproportional impact on the SOA yield.
Morris et al.: Absorption of volatile organic compounds (VOCs) by polymer tubing: implications for indoor air and use as a simple gas-phase volatility separation technique, Atmos. Meas. Tech., 17, 1545–1559, https://doi.org/10.5194/amt-17-1545-2024, 2024.
How to cite: Müller, M., Reinecke, T., Leiminger, M., and Graus, M.: Quantifying the influence of IVOC and SVOC on ambient SOA formation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9852, https://doi.org/10.5194/egusphere-egu26-9852, 2026.
Carbonaceous aerosols from biomass burning emissions are major contributors to atmospheric particulate matter and play a critical role in air quality, climate, and human health. Stable carbon isotopic composition (δ¹³C) provides a powerful tool for identifying emission sources and evaluating the influence of atmospheric processing on source signatures. This study applies δ¹³C analysis of three-step OC to assess the impact of photochemical aging on biomass burning aerosol isotopic characteristics.
Aerosol samples (PM1) from the combustion of twenty different biomass fuels were collected during the biomass burning experiment. Of the twenty biomass burning samples, six were selected for photochemical aging experiments based on their organic carbon mass, which exceeded the minimum detection and precision requirements for δ¹³C analysis across all three thermal OC fractions. Samples with lower carbon mass were excluded from aging to avoid increased analytical uncertainty associated with low signal-to-noise ratios. The isotopic composition of total carbon and organic carbon before and after aging experiment will be presented.
The isotopic composition of aerosol particles produced during uncontrolled combustion exhibit a broad distribution across biomass species. The average δ13CTC of PM1 of hardwood emissions is –26.9 ± 1.3 ‰and PM1 from softwood burning is –25.2 ± 0.1 ‰. The provided dataset also reveals distinct patterns in isotopic fractionation and carbon emissions across different biomass fuels under controlled combustion conditions. The observed fractionation factor ε (‰) varies significantly among different biomass burning species. The average fractionation factor for all biomass species is 0.0 ±1.0 ‰ The measured δ¹³Coc of aged samples indicates isotopic fractionation of organic carbon induced by photochemical aging. OH-aged samples showed no significant isotopic shifts relative to un-aged samples, although minor variations in total carbon mass were observed at higher temperature fractions, likely related to filter loading heterogeneity. In contrast, UV-aged samples exhibited systematic depletion in ¹³C across three temperature steps (200 °C, 350 °C, and 650 °C). The 350 °C fraction generally displayed the highest δ¹³C values among UV-aged samples, indicating distinct isotopic fractionation during photochemical processing. For example, δ¹³COC values for wood pellet emissions changed from −25.6 ‰, −25.7 ‰, and −25.4 ‰ in un-aged samples to −25.3 ‰, −25.1 ‰, and −25.0 ‰ after UV aging at 200 °C, 350 °C, and 650 °C, respectively.
Photochemical aging (particularly UV exposure) reveals systematic modifications to biomass burning isotopic signatures. These findings support the use of stable carbon isotopes for robust source apportionment of carbonaceous aerosols and for interpreting atmospheric observations influenced by photochemical aging.
How to cite: Habib, D. N., Garbaras, A., Dusek, U., Meijer, H., and Masalaite, A.: Tracing Photochemical Aging in Biomass Burning Aerosols Using Stable Carbon Isotopes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11220, https://doi.org/10.5194/egusphere-egu26-11220, 2026.
Brown carbon (BrC) remains one of the most uncertain components in the aerosol–radiation interactions due to the uncertainties in its different sources, secondary formation pathways, chemical aging, and optical properties. In this study, we investigate the global contribution of the different primary and secondary BrC sources to the aerosol absorption for the year 2018 with the Multiscale Online Nonhydrostatic AtmospheRe CHemistry (MONARCH) chemistry-transport model at global scale. All significant primary and secondary BrC formation pathways have been implemented in MONARCH. Primary BrC emissions include particulate organic aerosol from biomass burning (BB), biofuel (BF), fossil fuel (FF), and shipping (SH) sources. BB emissions are generated online following Liu et al. (2013) and Saleh et al. (2014), while BF, FF, and SH emissions are sourced from the Global Emission Modeling System (GEMS) inventory (https://gems.pku.edu.cn). Primary BrC undergoes photochemical bleaching through oxidation by OH radicals. Secondary BrC formation is represented through the oxidation of aromatic and terpene volatile organic compounds by OH and NO₃ radicals, allowing for both daytime and nighttime darkening processes, with yields dependent on simulated NOₓ conditions. Secondary BrC is further aged through ozonolysis and OH oxidation. For the BrC absorption aerosol optical depth (AAOD) calculation, the species-specific imaginary refractive indices are assigned to account for the differences in absorptivity. Model results are evaluated against the GHOST dataset, which provides harmonized global observations of aerosol optical properties derived from AERONET. Observed AAOD at 440 nm is partitioned into BrC and black carbon contributions following Bahadur et al. (2012). Our results confirm the dominant role of BB in BrC absorption near source regions, while highlighting the significance of secondary BrC formation in urban and polluted environments. The simulations also demonstrate the importance of the hygroscopicity in the BrC absorption calculations, emphasizing its relevance for accurately representing the aerosol radiative effects in modelling studies.
How to cite: Methymaki, G., Navarro-Barboza, H., Bowdalo, D., Mouchel-Vallon, C., Obiso, V., Pandolfi, M., Petetin, H., Shen, G., and Jorba, O.: The role of primary and secondary brown carbon in carbonaceous aerosol absorption: a global modelling study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12105, https://doi.org/10.5194/egusphere-egu26-12105, 2026.
Secondary organic aerosols (SOA) and their precursor vapors comprise a major fraction of atmospheric particulate matter, yet the molecular pathways linking precursor oxidation, new particle formation (NPF), condensation, and particle growth remain insufficiently constrained in complex urban environments. We will investigate these processes during a spring 2026 field measurements campaign in Helsinki, Finland, deploying a new Orbion 120 platform with multi-pressure chemical ionization to obtain high time-resolution, molecular-level measurements of key nucleation- and growth-relevant species.
The instrument will operate with two complementary reagent-ionization schemes: isotopically labelled nitrate chemical ionization to target highly oxygenated organic molecules (HOMs) and strong acids, and uronium chemical ionization to target atmospheric bases and high-proton-affinity species that can stabilize acidic clusters and influence early particle growth. This dual-chemistry approach is designed to resolve co-variations between strong acids/HOMs and basic species under rapidly evolving springtime urban conditions, and to probe transformation processes (e.g., functionalization/aging and brown-carbon-relevant chemistry) alongside gas-to-particle partitioning prior to and during NPF events.
We will describe the field setup and operating strategy (inlet configuration, switching scheme, and overall analytical method design) and report the first campaign-derived observations, focusing on event-non-event contrasts and molecular fingerprints associated with NPF in spring-time Helsinki. These measurements aim to provide new ambient constraints on the coupled roles of oxidized organics/strong acids and atmospheric bases in urban springtime particle formation, supporting improved mechanistic understanding and model representation of SOA and NPF.
How to cite: Shcherbinin, A., Finkenzeller, H., Jost, H., Holm, S., and Kangasluoma, J.: Molecular-level constraints on springtime urban new particle formation in Helsinki using Multi-Pressure Chemical Ionization Mass Spectrometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18670, https://doi.org/10.5194/egusphere-egu26-18670, 2026.
Wildfires are a major source of atmospheric organic aerosol (OA), emitting primary organic aerosol (POA) and volatile organic compounds that oxidize to form secondary organic aerosol (SOA). This oxidation also produces formaldehyde (HCHO), which is additionally emitted directly from fires alongside nitrogen dioxide (NO₂). Both HCHO and NO2 are detectable from space, offering the potential to observationally constrain organic aerosol formation during biomass burning. However, this potential remains poorly quantified.
Here, we evaluate whether satellite observations of HCHO and NO₂ can be used to estimate POA and SOA from biomass burning events. We compare simulations from four models with satellite measurements from OMI (HCHO, NO₂) and POLDER (AOD). All models reproduce correctly the observed spatial patterns of HCHO, NO2 and AOD, but they overestimate trace gas concentrations and slightly underestimate AOD. Despite differences in magnitude, models and observations show linear relationships between HCHO and AOD.
Building on these observed relationships, we develop a satellite-based methodology to estimate POA and SOA with minimal use of model assumptions. The observed HCHO-AOD correlation is combined with satellite-derived mass extinction coefficient to relate observed AOD to organic aerosol. In addition, the relationship between NO2 and POA fraction, derived from in-situ measurements, is used to separate the two types of organic aerosols. Together, these relationships allow the estimation of POA and SOA from HCHO and NO2 observations, and sensitivity analysis shows that the method is robust. Application to the Amazon and African savanna indicates that observation-based POA formation is 3.82 and 5.53 times higher, respectively, than modeled values, while SOA formation is higher by factors of 2.4 and 3.5, suggesting model underestimation of organic aerosol production from biomass burning.
How to cite: Román de Miguel, F., Croft, B., Gonçalves, M., Marangio, F., Pierce, J., Tsimpidi, A., van Noije, T., Vella, R., and Schutgens, N.: Estimation of secondary organic aerosol from biomass burning using observations of formaldehyde, NO2 and AOD, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19190, https://doi.org/10.5194/egusphere-egu26-19190, 2026.
Nitrogen-containing organic compounds (NOCs) represent key light-absorbing components of atmospheric PM2.5, yet the sources and formation mechanisms of nitrophenolic species remain unclear. Thirty-six PM2.5 samples collected during winter and summer from Yangon and Mandalay, Myanmar, were analyzed using UHPLC-Orbitrap MS. A total of 562-1318 organic compounds (average 1064) were identified in the ESI- mode, with NOCs accounting for 14-21% of molecular numbers and 13-35% of total concentrations.
Nitrophenolic compounds, defined by O/N ≥ 3 and AI > 0.5, were mainly distributed in zones C, F, and G of the Van Krevelen diagram and dominated the aromatic NOC fraction. Two ubiquitous nitrophenols—nitrocatechol (C6H5NO4) and dimethylnitrocatechol (C8H9NO4)—were detected in all samples and exhibited strong positive correlations, suggesting similar sources and transformation pathways. Their relative abundances showed distinct humidity dependence, with C6H5NO4 favored under dry conditions (RH < 50%) and C8H9NO4 under humid conditions (RH > 60%).
These findings highlight the significant role of nitrophenolic compounds in brown carbon formation and secondary processes in tropical aerosols, providing key mechanistic insights for subsequent modeling of their humidity-dependent formation pathways.
How to cite: Zhang, N., Liu, Z., Feng, J., Ma, Y., Ge, X., Wang, J., Carlo, P. D., and Aruffo, E.: Mechanisms of nitrogen-containing organic matter production in atmospheric aerosols in typical megacities in Myanmar: Coastal and Inland Cities of Yangon and Mandalay as an Example, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19929, https://doi.org/10.5194/egusphere-egu26-19929, 2026.
Online chemical characterization of atmospheric particles is often challenged by thermal decomposition, fragmentation, wall losses, ionization selectivity, and rapid changes in particle concentration and composition. To resolve these current limitations, we developed the Wall-Free Particle Evaporator (WALL-E) coupled to a chemical ionization mass spectrometer - model Vocus B4 (Bansal et al., 2025). WALL-E enables continuous evaporation of particles to detectable vapors using flash evaporation utilizing a mixture of heated sheath flow as well as a compact thermal desorption region, aiming to preserve fast atmospheric variability while reducing artefacts and decomposition linked to surface interactions by minimizing residence time (Gao et al., 2025). In this work, we present the first ambient field deployment of the WALL-E - Vocus B4 chemical ionization mass spectrometer equipped with an Aim reactor (Riva et al., 2024). Field measurements were conducted from mid-September to mid-October 2025 at the AIRPARIF background supersite named Paris 1er – Les Halles in France.
Figure 1: Temporal evolution of the some of the trace gases
The campaign provides a real-world test of WALL-E performance under highly variable urban conditions. The resulting particle-phase molecular time series captures short-timescale variability alongside sustained background changes. To further identify the main aerosol sources, we applied matrix factorization to the WALL-E–Vocus B4 dataset to resolve distinct composition modes with characteristic temporal signatures. A key outcome is the prominent role of cooking-related emissions, which emerge as a robust factor with clear diurnal structure (enhanced during meal-time periods) and diagnostic molecular features in the particle-phase spectra. The analysis also separates recurring daily patterns from more persistent background/regional influences. Overall, this work provides a compact, interpretable description of urban particle-phase variability in central Paris based directly on online molecular composition.
This work was supported by the CLOUD-DOC project (Grant Agreement No. 101073026) under HORIZON-MSCA-2021-DN-01. This work was also supported by the European Research Council (ERC) under the European Union’s Horizon Europe research and innovation program through the Starting Grant CHANEL (Grant Agreement No. 101076276).
- Bansal, P., et al. “Comprehensive airborne molecular contamination monitoring with single-digit parts-per-trillion sensitivity.” Journal of Micro/Nanopatterning, Materials, and Metrology 24(4), 044003 (30 December 2025). https://doi.org/10.1117/1.JMM.24.4.044003.
- Gao, L., Zgheib, I., Stergiou, E., Carstens, C., Sari Doré, F., Dupanloup, M., Bourgain, F., Perrier, S., and Riva, M.: Characterization of the newly designed wall-free particle evaporator (WALL-E) for online measurements of atmospheric particles, Atmos. Meas. Tech., 18, 5087–5101, https://doi.org/10.5194/amt-18-5087-2025, 2025.
- Riva, M., Pospisilova, V., Frege, C., Perrier, S., Bansal, P., Jorga, S., Sturm, P., Thornton, J. A., Rohner, U., and Lopez-Hilfiker, F.: Evaluation of a reduced-pressure chemical ion reactor utilizing adduct ionization for the detection of gaseous organic and inorganic species, Atmos. Meas. Tech., 17, 5887–5901, https://doi.org/10.5194/ , amt-17-5887-2024, 2024.
How to cite: Zgheib, I., Roska, M., Gaie-Levrel, F., Gauvin, L., Rabort, M., Perrier, S., Rohner, U., Gkatzelis, G., Lopez-Hilfiker, F., and Riva, M.: Organic aerosol source characterization in Paris using an online chemical ionization mass spectrometer , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21018, https://doi.org/10.5194/egusphere-egu26-21018, 2026.
The concentrations of peroxides and carbonyl compounds in the gas and aerosol phases were observed over urban Beijing in summer and winter 2022. Peroxide multiphase reactions were identified as dominant pathways for sulfate formation in fine particles (PM2.5), and carbonyl compound multiphase transformation significantly contributed to secondary organic aerosol (SOA) formation, with the oxidative pathway dominating (> 80%) over the non-oxidative pathway. We develop the parameterization formulas for SOA formation from carbonyl compounds, showing that the rising atmospheric H2O2 level in Beijing significantly increased SOA formation rate via carbonyl compound multiphase reactions both in summer and winter in recent years. The mechanisms by which multiphase transformation of peroxides and carbonyl compounds promote secondary aerosol formation are suggested.
How to cite: Chen, Z. and Dai, Y.: Aerosol Formation by Multiphase Reactions of Peroxide and Carbonyl Compounds over Beijing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21483, https://doi.org/10.5194/egusphere-egu26-21483, 2026.
Water-soluble organic matter (WSOM) is a major component of atmospheric aerosols, yet most constituents remain insufficiently characterized and their seasonal evolution is not well understood. In this study, WSOM extracted from fine particulate matter (PM2.5) collected across four seasons in suburban Chongqing was analyzed using ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Carboxylic-rich alicyclic and aliphatic compounds emerged as key contributors to the seasonal evolution of WSOM. Seasonal relationships linking the combustion enthalpy of WSOM to the nominal oxidation state of carbon were established, with WSOM in autumn and winter exhibiting broader energy-content distributions. Six distinct molecular evolution pathways were identified during polluted conditions, with methylation/demethylation and hydrogenation/dehydrogenation accounting for about 75% of transformations, whereas sulfation/desulfation emerged as the most thermodynamically active process. These findings provide molecular-level insight into the seasonal evolution of WSOM in humid suburban PM2.5, offering a scientific basis for suburban air pollution control.
How to cite: Yang, N. and Fu, P.: Seasonal Evolution of Atmospheric Water-Soluble Organic Matter in Humid Suburban PM2.5, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22339, https://doi.org/10.5194/egusphere-egu26-22339, 2026.
