Exposure to PM2.5 is the leading environmental risk to healthin India, where the National Capital Territory of Delhi experiences annual mean concentrations of ~110 μg m-3. During the post-monsoon season, severe air pollution events are frequent, with extreme levels exceeding 1000 µg m−3. A large fraction of PM2.5 in Delhi is organic aerosol (OA) derived from a wide range of primary and secondary sources. Recent studies investigating the composition and sources of OA in Delhi using online aerosol mass spectrometry (AMS), followed by positive matrix factorisation have highlighted the dominance of primary sources over secondary production during the very polluted post monsoon period. These studies suggest the resolved traffic and burning-related sources were the largest contributors, however, significant oxidised organic aerosol is present across most of the year, and the dominant sources of this material cannot be resolved using this approach.
High-resolution mass spectrometry (HRMS) allows detailed investigation of the molecular complexity of OA composition. Previous studies have focussed on key tracers of specific OA sources such as biomass burning or biogenic volatile organic compound oxidation. However, targeted analysis reveals a biased and incomplete picture of the chemical composition which limits our ability to detect emerging pollutants. Here we harness recent advances in the analysis of complex environmental samples via non-target analysis (NTA), coupled with advanced suspect screening and a novel semi-quantification method to investigate the complex composition of OA within Old Delhi during the post-monsoon period of 2018. Using high time resolution filter sampling and an automated analysis workflow, the temporal evolution of the OA could be studied. Hierarchical cluster analysis of this high resolution data identified six separate OA factors. Two factors peaked at night and were dominated by primary oxidised traffic and wood combustion emissions. The other four factors peaked during the day and could be linked to different types of secondary organic aerosol that peak under different oxidative and meteorological conditions. These species showed different temporal profiles to the oxidised factors, MO-OOA and LO-OOA, measured using AMS, providing novel insights into the sources and factors that control local SOA production in Delhi. This offline NTA approach provides complementary information to the online AMS observations, while only requiring the deployment of a filter sampler to the observation location.
How to cite: Hamilton, J., Bryant, D., Rickard, A., Nelson, B., Drysdale, W., Hopkins, J., Lee, J., Cash, J., Langford, B., Nemitz, E., Shivani, S., and Gadi, R.: Understanding the sources and formation of organic aerosol in Delhi using non-target analysis , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8441, https://doi.org/10.5194/egusphere-egu25-8441, 2025.
Organic aerosol (OA) in the atmosphere can exist in liquid, semi-solid, or solid states, influenced by molecular properties and environmental conditions. However, regional and global models typically assume OA to be only in a liquid phase. Recent studies underscore that OA can present in a semi-solid or even solid state in low-temperature, dry environments. Under such conditions, increased viscosity can impede heterogeneous reaction rates by reducing diffusion. We develop a novel phase state scheme within the GEOS-Chem global model, enabling real-time simulation of OA phase states from various sources under diverse environmental conditions. Subsequently, we investigate the effects of OA phase states on heterogeneous chemical processes, including gas-particle partitioning, reactive uptake, and ice particle nucleation. Finally, our simulated OA concentrations are evaluated against global vertical profiles from aircraft observations. Our simulations indicate that on a global scale, viscosity is higher in polar regions compared to tropical regions and increases with altitude, with little to no liquid phase present above 500 hPa. Additionally, anthropogenic secondary OA (SOA) exhibits greater viscosity than biogenic SOA, hydrophobic primary OA (POA), and hydrophilic POA. The increased viscosity leads to slower gas-phase partitioning and uptake processes, thereby reducing near-source concentrations and increasing concentrations in remote areas. Considering solid-phase OA as heterogeneous ice nuclei enhances OA removal. Overall, our simulations demonstrate that incorporating phase state effect results in a reduction of OA concentrations, particularly for the more viscous SOA.
How to cite: Li, Y. and Heald, C.: Global impacts of organic aerosol phase state, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3242, https://doi.org/10.5194/egusphere-egu25-3242, 2025.
For several decades intense new particle formation (NPF) events have been observed by aircraft measurements in the upper tropical troposphere (UTT) (Brock et al. 1995, Weigel et al. 2011, Williamson et al. 2019). These events typically occur above 8 km altitude in the outflow of mesoscale convective systems. The resulting particles can grow further and be transported downwards where they enhance cloud condensation nuclei (CCN) levels over large geographic areas in the tropics. However, the chemical mechanism driving these events remained unclear, as no direct measurements of the involved low-volatility gaseous precursors were possible.
Here, we present in-situ aircraft observations taken on board the High Altitude LOng Range (HALO) aircraft (operated by the German Aerospace Center, DLR) over the Amazon rainforest with the goal of deciphering the chemical mechanism behind NPF in the UTT. The measurements were taken during the CAFE Brazil campaign in December 2022/January 2023, where HALO was stationed in Manaus, Brazil. The aircraft was equipped with a comprehensive suite of instruments measuring both gas- and particle-phase properties. To detect low volatility organic compounds, we operated a purpose-built nitrate Chemical Ionization Mass spectrometer (CIMS).
We show that isoprene nitrates drive new particle formation after sunrise in the upper tropospheric outflow of mesoscale convective systems (Curtius et al. 2024). Isoprene (C5H8) is carried from the boundary layer to high altitudes within deep convective cells, while NOx is produced in these cells via lightning. After sunrise, oxidation of isoprene by OH is initiated, as well as photolytic conversion of NO2 to NO, which leads to the formation of second generation isoprene nitrates. At the cold temperatures in the upper tropical troposphere (around -60 °C) these molecules have sufficiently low saturation vapour pressure to drive strong new particle formation events, leading to several tens of thousands of particles per cubic centimetre. We find that this process happens frequently over the Amazon at high altitude (>8 km) and might have far reaching consequences for tropical aerosol and CCN production.
We also compare our results with recent findings from the CLOUD experiment (Shen et al. 2024), which studied the capability of isoprene to nucleate at low temperature conditions and find good agreement between field and laboratory measurements.
References:
Brock C. A., et al. (1995), Science, 270, 1650-1653
Weigel, R, et al. (2011), Atmos. Chem. Phys., 11, 9983-10010
Williamson, C. J., et al. (2019). Nature, 574(7778), 399-403.
Curtius, J, et al. (2024). Nature, 636(8041), 124-130.
Shen, J, et al. (2024). Nature, 636(8041), 115-123.
How to cite: Heinritzi, M., Beck, L., Richter, S., Zauner-Wieczorek, M., Hernández Pardo, L., Klimach, T., Barmpounis, K., Tripathi, N., Ringsdorf, A., Holzbeck, P., Nussbaumer, C., Harder, H., Williams, J., Fischer, H., Pöhlker, C., Possner, A., Pöhlker, M., Pöschl, U., Lelieveld, J., and Curtius, J.: Isoprene nitrates drive new particle formation in Amazon’s upper troposphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16087, https://doi.org/10.5194/egusphere-egu25-16087, 2025.
Aerosols are present as complex organic-inorganic mixtures within our atmosphere, resulting in particles presenting phase separated morphology. Mixed organic-inorganic aerosols can be predominantly found in nascent sea spray aerosols (SSA). When these aerosols are exposed to supersaturated conditions (>100% RH), the water uptake ability of the aerosols vary based on the composition of the mixture. Previous studies have characterized phase separated systems through the determination of an average oxygen to carbon (O/C) ratio where liquid-liquid phase separation (LLPS) reaches its limit. The hygroscopicity of complex mixtures presenting LLPS was previously studied through the measurement of CCN activity within a 2-methylglutaric (2-MGA)/ammonium sulfate (AS) binary system and a 2-MGA/AS/sucrose ternary system; both studies correlated water-uptake abilities to O/C and surface tension. However, little is known about the influence of solubility of the third component on phase separation of a ternary mixture containing 2-MGA/AS. Additionally, the water-uptake properties of mixtures containing nitrogen containing compounds, such as amino acids, are not well defined. Amino acids are a major component of SSA and can contribute to aerosol hygroscopicity. Therefore, it is undetermined if O/C alone is an acceptable parameter for the estimation of solubility and hygroscopicity of complex amino acid mixtures. To improve our understanding of LLPS within aerosol mixtures and factors influencing its presence, three ternary systems were studied – a leucine system (2-MGA/AS/leucine), valine system (2-MGA/AS/valine), and proline system (2-MGA/AS/proline). For each system, the CCN activity of mixture compositions with varying O/C ratios and compositions was measured using a Cloud Condensation Nuclei Counter (CCNC) at 0.375% to 1.667% SS. For all mixtures, the single hygroscopic parameter κ was calculated. Experimental κ-results demonstrated increased hygroscopic activity as the amino acid became more soluble in the order of leucine<valine<proline. Experimental κ results were compared against four theoretical models; three of the theoretical models included were Köhler theory, O/C LLPS with surface tension (O/C LLPS-ST) and a newly developed model, X/C LLPS with surface tension (X/C LLPS-ST). For this study, a new parameter considering O/C and nitrogen to carbon (N/C) X/C, was introduced as a parameterization for solubility. The O/C LLPS-ST model was adapted to consider X/C for subsequent estimations of κ. A fourth theoretical model took a weighted average of the O/C LLPS-ST and X/C LLPS-ST models. The study provides an improved understanding of amino acid aerosol mixtures’ water uptake abilities through the introduction of a new parameter and model. As a result, the study is able to show varied N/C contribution to the system based on the structure of the amino acid as well as a method to improve current abilities to predict hygroscopicity of these complex, nitrogen-containing aerosol mixtures.
How to cite: Ferdousi-Rokib, N., Malek, K. A., Gohil, K., Pitta, K. R., Dutcher, D. D., Raymond, T. M., Freedman, M. A., and Asa-Awuku, A. A.: Influence of Salting Out and Organic Nitrogen on Mixed Amino Acid Aerosol Cloud-Nucleating Ability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2937, https://doi.org/10.5194/egusphere-egu25-2937, 2025.
Sesquiterpene emitted from nature is the main precursor for secondary organic aerosol (SOA) formation. β-caryophyllene (BCA) is the most common sesquiterpene. Autoxidation of BCA oxidation products may lead to the rapid formation of extremely low-volatile organic compounds (ELVOCs), and it could be one of the dominant SOA formation pathways. However, until now the BCA SOA formation mechanisms are missing an autoxidation pathway. In this work, we develop a semi-explicit peroxy radical autoxidation mechanism for the production of ELVOCs from the oxidation of BCA with two major oxidants (O3 and NO3) under dark conditions and couple it to the Master Chemical Mechanism (MCMv3.3.1). Here, SOA originating from BCA is simulated under varying environmental conditions (temperature, humidity, and NOx levels) reported in several BCA chamber experiments. Simulations are performed with the SSH-Aerosol model accounting for multiphase chemistry, ELVOC nucleation, and condensation/evaporation. Our mechanism demonstrates a very good agreement between the modeled and observed SOA mass concentrations and size distribution.
How to cite: Shi, Y., Couvidat, F., and Kata-Sartelet, K.: Modeling the role of extremely low-volatile organic compounds in β-caryophyllene secondary organic aerosol formation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5620, https://doi.org/10.5194/egusphere-egu25-5620, 2025.
The formation, degradation, and physical properties of organic aerosol (OA) constituents strongly depend on multiphase chemical kinetics. Gas-phase oxidation of OA precursors has been extensively investigated in recent decades. However, laboratory kinetic data on the aqueous-phase oxidation of the organics are scarce. As a result, the aging of organics in cloud droplets and deliquescent aerosols is commonly simplified in model simulations. In studies that aim to characterize the constituents and the phase state of organics specifically, this limitation may be overcome by introducing reactions based on structure-activity relationships (SAR). In models with sophisticated gas-phase oxidation and partitioning schemes, organics of various sizes and oxidation states are present in the condensed phase. Thus, an oxidation mechanism for hundreds of species needs to be constructed. However, manual mechanism development is time-consuming and error-prone. The use of new or updated SAR methods may lead to different dominant reaction routes, further increasing the required time investment. Alternatively, various SAR methods can be combined in a code framework in order to automatically generate self-contained mechanisms for a given list of compounds, within seconds. Updates of the SARs can be implemented in the underlying code framework.
In this study, we construct and apply a mechanism generator for the application in global model simulations. It focuses on the chemical processing in aqueous media such as cloud droplets and deliquescent aerosols. The generator is developed in conjunction with the MESSy model. As a result, the output of the generator is fined-tuned to be used with the MESSy submodels. However, mechanisms can be generated without MESSy by user input of molecule structures. This feature is intended to simplify the wide range application of the generator results. Molecular structure input is given by SMILES strings and output can be generated in either SMILES or InChI-Key format. Currently, the generator is restricted to a predefined set of input molecule types. This is due to the limitations of the available SARs. The generator considers the following reaction types: 1) OH-oxidation 2) photolysis 3) hydrolysis of nitrates and 4) peroxy-radical reactions. Minor reaction pathways are neglected to minimize the effect of the new chemistry on model performance.
An aqueous-phase mechanism for the most water-soluble organics has been generated and used to simulate aerosol and cloud chemistry within MESSy. Test simulations with the expanded aqueous-phase mechanism revealed a change in the distribution of aerosol constituents. The results suggest that in aerosols larger organics are efficiently degraded and the average molecular size of organics is smaller. However, the change in aerosol mass by outgassing of organics is less pronounced than expected. The mechanism generator does not construct phase-partitioning "reactions" as the respective constants are missing. Thus, in the generated mechanism solely compounds that have a predefined partitioning may outgas. Consequently, future developments will focus on the estimation of partitioning constants upon generation of a novel molecule. In general, the range of application of the generator may be extended for further reactions.
How to cite: Wieser, F. and Taraborrelli, D.: Mechanism generation for aqueous-phase oxidation of organics: development and application for global model simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9174, https://doi.org/10.5194/egusphere-egu25-9174, 2025.
Oxygenated organic molecules (OOMs) are critical intermediates connecting the oxidation of volatile organic compounds (VOCs) and the formation of secondary organic aerosol (SOA). However, directly measuring these intermediate vapors presents significant challenges, particularly in megacity areas, due to their exceedingly low concentrations and complex compositional diversity. Since 2018, we have been monitoring OOMs at the SORPES station in Nanjing, eastern China, using a nitrate-CI-APi-ToF. To manage and simplify the complex mass spectra, we employed both binPMF and sub-range binPMF techniques prior to peak fitting, successfully identifying over 2,000 distinct OOM molecules with high accuracy. We also developed a framework to identify probable precursors of the detected OOMs. Our findings indicate that the oxidation of anthropogenic VOCs primarily drives OOM formation across most seasons, contributing approximately 40% each from aromatic compounds and aliphatic hydrocarbons, mainly alkanes. During summer, however, the oxidation of biogenic VOCs significantly contributes OOM production. The irreversible condensation of these OOMs substantially contributes to the growth of newly formed particles and the generation of SOA, particularly under warmer season and highly polluted conditions.
How to cite: Nie, W., Liu, Y., Yan, C., and Ding, A.: Oxygenated organic molecules (OOMs) in the megacities of east China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9506, https://doi.org/10.5194/egusphere-egu25-9506, 2025.
Particulate matter (PM) is a major climate-forcing agent and significantly impacts air quality. To grasp how environmental policies and climate change impact atmospheric aerosols, long-term measurements are vital, especially for organic aerosol (OA) and black carbon (BC). OA represents a large portion of aerosol mass, while BC has the strongest direct radiative forcing effect. State-of-the-art equipment like the Aerosol Chemical Speciation Monitor (ACSM) and the Multi-Angle Absorption Photometer (MAAP) help to identify OA and BC sources, respectively. Since 2012, an ACSM and a MAAP have operated at the ACTRIS-TROPOS research station in Melpitz, Germany, enabling a decade-long study of aerosol composition and OA sources for PM1 from September 2012 to August 2022.
To analyse these trends, a rolling Positive Matrix Factorization (PMF) approach was applied and implemented in SoFi Pro software (Datalystica Ltd., Villigen, Switzerland). The Melpitz station's strategic location allows for the study of particle composition changes typical of both Western and Eastern Europe (Spindler et al., 2010). This improves our understanding of emissions and the effects of air quality regulations on PM1 chemical species in these regions. The results reveal high PM1 mass concentrations were associated with eastern air masses across all meteorological seasons. However, the relative contributions of individual chemical components varied depending on the season and the origin of the air mass. Expanding on Atabakhsh et al. (2023) work, which analyzed a 12-month dataset, this study identified five OA factors: three associated with primary organic sources—hydrocarbon-like OA (HOA), biomass burning OA (BBOA), and coal combustion OA (CCOA)—and two oxygenated OA factors—more-oxidized OOA (MO-OOA) and less-oxidized OOA (LO-OOA). Trend analysis using a pre-whitening method (Collaud Coen et al., 2020) revealed a statistically significant annual decrease of -4.59% y-1 in total PM1 mass over the decade, driven by decreases in nitrate (-1.10% y-1) and equivalent BC (eBC) (-1.3% y-1) concentrations. However, HOA showed a minor decline (-0.25% y-1) under eastern air masses, BBOA increased by +0.94% y-1 during summer, and CCOA showed a modest increase (+0.27% y-1) in western air masses. The OOA factors showed declining trends in eastern air masses (-1.52% and -1.09% y-1), indicating improvements in the emissions of secondary aerosol precursors.
This study provides a comprehensive analysis of seasonal variability, source apportionment, and trends of PM1 components in Central Europe. It highlights differences in air masses from Eastern and Western Europe, providing insights into regional air quality regulations and sources of atmospheric aerosols.
References:
Atabakhsh, S., et al. (2023) Atmospheric Chem. Phys., 842.
Collaud Coen, et al. (2020) Atmos. Meas. Tech., 178.
Spindler, G., et al. (2010) Atmos. Environ., 44, 164-173
How to cite: Atabakhsh, S., Poulain, L., Bigi, A., Collaud Coen, M., Pöhlker, M., and Herrmann, H.: Decadal Trends in Atmospheric Aerosols: Insights into PM1 Composition, Seasonal Variability, and Source Apportionment in Central Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11592, https://doi.org/10.5194/egusphere-egu25-11592, 2025.
Per- and polyfluoroalkyl substances (PFAS), often referred to as "forever chemicals", are a class of man-made, extremely stable chemicals, which are widely used in industrial and commercial applications. Exposure to some PFAS is now known to be detrimental to human health. By virtue of PFAS long residence times, they are widely detected in the environment, including remote locations such as the Arctics, where the origin of the PFAS is poorly understood. It has been suggested that PFAS may be transported through contaminated waters, leading to accumulation in coastal areas, where they can be aerosolised via sea spray, thereby extending their geographical distribution far beyond their original source regions. The aim of this work is to investigate, for the first time, whether "forever chemicals" could be transported to areas considered to be pristine, far from coastal sites. This study was performed at the Amazonian Tall Tower Observatory (ATTO), a unique remote site situated in the middle of the Amazon rainforest, where a restricted PFAS, perfluorooctanoic acid (PFOA), was observed with concentrations reaching up to 2 pg/m3. A clear trend of increasing concentration with sampling height was observed and air masses from the south over Manaus had the highest concentrations. Atmospheric lifetime estimations, removal mechanisms supported by measurements at two heights (320 and 42 m above the rainforest), and concentration spikes indicated a long-range transport of PFOA to pristine Amazon rainforest. Potential sources, including industrial activities in urban areas, were explored, and historical fire management practices considered. This research presents the first measurements of PFAS in the atmosphere of Amazon rainforest. Remarkably, even in this remote natural environment, appreciable levels of PFAS can be detected. This study provides valuable insights into the long-range transport of the anthropogenic "forever chemical" into a remote natural ecosystem and should raise awareness of potential environmental implications.
How to cite: Kourtchev, I., Sebben, B. G., Brill, S., Barbosa, C. G. G., Weber, B., Ferreira, R. R., D'Oliveira, F. A. F., Dias-Junior, C. Q., Popoola, O. A. M., Williams, J., Pöhlker, C., and Godoi, R. H. M.: Occurrence of a “forever chemical” in the atmosphere above pristine Amazon Forest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10922, https://doi.org/10.5194/egusphere-egu25-10922, 2025.
Alpha-pinene is one of the most studied precursor molecules for new particle formation (NPF). It was shown that RO2 radicals formed by α-pinene ozonolysis can undergo autoxidation to rapidly form highly oxygenated molecules (HOMs) (Bianchi et al, 2019). These HOMs are hypothesized to often contain hydroperoxide (C-O-O-H) functionalization. As the functionalization of molecules influences their vapor pressure, it is an important factor when modeling the formation and growth of new aerosol particles (Stolzenburg et al, 2022).
Authentic standards of α-pinene derived HOMs are sparse. While some research groups have achieved the synthesis of HOM-dimers (see, e.g., Kenseth et al, 2023), monomeric HOM compounds with the significant hydroperoxide functionalization are still not available commercially (Mettke et al, 2022). There is an urgent need to investigate the detection of these compounds in the widely used chemical ionization mass spectrometers, as their charging efficiencies remain largely unknown (Alage et al, 2024).
In this work, we report the synthesis of two α-pinene derived molecules containing hydroperoxy-acid (C(O)-O-O-H) groups, verified by H- and C-NMR techniques. We characterized the synthesized standards using an Orbitrap mass spectrometer with electrospray ionization and NO3- based chemical ionization at atmospheric pressure. We demonstrate that both ionization methods result in much higher signals of the corresponding carboxylic acids. This indicates a rapid destruction of the hydroperoxy acids during the ionization process.
Our results imply that HOMs formed via the autoxidation of α-pinene might often not be correctly quantified with different mass spectrometric techniques. As especially the chemical ionization using NO3- is widely used in atmospheric studies related to NPF, this could result in huge discrepancies when atmospheric process rates (such as nucleation and growth rates of newly formed particles) are derived from gas-phase measurements.
References:
Alage, S. et al (2024), Atmos. Meas. Techn., 17(15), 4709-4724, https://doi.org/10.5194/amt-17-4709-2024
Bianchi, F. et al (2019), Chem. Rev., 119(6), 3472–3509, https://doi.org/10.1021/acs.chemrev.8b00395
Kenseth, C. M. et al (2023), Science, 382(6672), 787-792, https://doi.org/10.1126/science.adi0857
Mettke, P. et al (2022), Atmosphere, 13(4), 507, https://doi.org/10.3390/atmos13040507
Stolzenburg, D. et al (2022), J. Aerosol Sci., 166, 106063, https://doi.org/10.1016/j.jaerosci.2022.106063
How to cite: Tischberger, M., Kaiser, M., Grothe, H., Lair, M., Opacak, M., Schachamayr, D., and Stolzenburg, D.: Insufficient mass spectrometric detection of synthesized hydroperoxy acids from α-pinene ozonolysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12699, https://doi.org/10.5194/egusphere-egu25-12699, 2025.
Organic aerosols constitute up to 90% of submicron aerosol mass, playing a crucial role in influencing the Earth’s radiative forcing by absorbing and scattering incoming solar radiation, as well as acting as cloud condensation nuclei. To unravel the complexity of organic aerosol (OA) chemical composition, recent analytical advances, such as high-resolution mass spectrometry and the development of non-target screening (NTS) workflows, have been applied to present-day atmospheric aerosol samples. However, for a better understanding on how human activities have influenced OA chemistry, it is essential to unravel its changes between the pre-industrial and industrial periods.
In this study, we present the first application of a novel NTS method to an ice core from the Belukha glacier (Russian Federation), covering the period from 1800 to 1980 CE. A total of 398 molecules were identified, mainly secondary organic aerosol tracers (SOA), such as mono- and di-carboxylic acids. Since the 1950s, we observed a shift in the atmospheric aerosol composition, characterized by the appearance of organic molecules—such as nitrogen-containing compounds—that result from increased atmospheric reactions with anthropogenic NOx or direct emissions. Additionally, we recorded a significant increase in the oxygen-to-carbon ratio (+3%) and the average carbon oxidation state (+18%) of the detected compounds compared to the pre-industrial period, suggesting an increased oxidative capacity of the atmosphere, associated with enhanced tropospheric ozone concentrations.
This work demonstrates the potential of NTS ice-core studies for extending the reconstruction of OA chemical composition prior to the advent of direct instrumental monitoring, providing valuable contributions to the atmospheric aerosol community.
How to cite: Burgay, F., Salionov, D., Singer, T., Eichler, A., Brutsch, S., Jenk, T., Vogel, A., Papina, T., Bjelic, S., and Schwikowski, M.: Non-target screening ice-core analysis reveals changes in the atmospheric organic aerosol composition between the pre-industrial and industrial periods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11510, https://doi.org/10.5194/egusphere-egu25-11510, 2025.
Oxygenated organic molecules (OOMs) formed from oxidation of anthropogenic and volatile organic compounds VOCs are essential ingredients for atmospheric new particle formation (NPF) and secondary organic aerosol formation. There is a large variety of OOM compounds, but currently, for the vast majority of OOMs, their molecular structures and formation pathways are largely unknown. Here, we made detailed chemical analysis of gas- and aerosol-phase OOMs produced from a-pinene ozonolysis, using a high-resolution time-of-flight chemical ionization mass spectrometer (HrTOF-CIMS) attached to the filter inlet for gas and aerosol (FIGAERO), as well as an ultrahigh-performance liquid chromatography-electrospray ionization Orbitrap mass spectrometer (UPLC/(-)ESI-Orbitrap MS). Based on LC and MS/MS fragmentation ions, we identified isomer molecular structures and chemical formation pathways. For C19H30O5, one isomer forms in the particle phase via aldol condensation, whereas another isomer forms via esterification. Two isomers of C16H26O6 form via decarboxylation from different C17H26O8 isomers. Thus, our experimental results with detailed chemical speciation show that OOM NPF precursors also form in the particle phase. Currently, parameterizations for the growth of newly formed particles are based on the gas-to-particle conversion of low-volatility OOMs formed in the gas phase. Our study demonstrates that particle-phase formation pathways of OOMs should also be considered for the growth of new particles in the atmosphere.
How to cite: Vasudevan-Geetha, V., Tiszenkel, L., Russo, R., Bryant, D., and Lee, S.-H.: Oxygenated Organic Molecules in Newly Formed Biogenic Particles: Molecular Structures and Formation Pathways, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13005, https://doi.org/10.5194/egusphere-egu25-13005, 2025.
This study explores how the evolution of aerosol size distribution and chemical composition, driven by exposure to biogenic volatile organic compounds (BVOCs), influences cloud microphysics over the boreal forests of Southern Finland. Aerosol properties were derived from eight years of particle number size distribution (PNSD) and chemical composition measurements collected at the SMEAR II station. These data were categorized based on the time air masses spent traversing forested regions (Time Over Land, ToL), calculated using 97-hour HYSPLIT back trajectories. ToL was divided into 5-hour bins, and the median PNSD and aerosol composition for each bin were used to drive simulations with the PseudoAdiabatic bin-micRophySics University of Exeter Cloud parcel model (PARSEC).
The boreal forest emits biogenic volatile organic compounds (BVOCs) into the atmosphere, where these compounds undergo various oxidation processes. These reactions influence the growth and composition of atmospheric particles, ultimately contributing to the formation of secondary organic aerosols (SOA). Our simulation results show that with longer ToL, aerosols exhibit increased particle size and higher organic mass fractions. These changes significantly affect simulated cloud droplet activation and subsequent microphysical processes. PARSEC simulations revealed that the fraction of activated particles—cloud droplets relative to total aerosols—increases with both ToL and updraft velocity. However, for high ToL conditions (>3 days), the maximum supersaturation plateaus, particularly at stronger updraft velocities (>1 m/s), even as the activated fraction continues to increase. Moreover, once ToL exceeds one day, the albedo of clouds stabilizes rapidly, underscoring the importance of the initial 30-hour period in modulating the local climate.
While these observations provide insights into the coupling of aerosols and cloud properties, additional complexities remain. For instance, the impact of cloud droplet collisions, coalescence, and entrainment on cloud microphysics along ToL trajectories will be further discussed, highlighting their role in shaping cloud lifetime and albedo feedbacks.
By focusing on clean-sector air masses to minimize anthropogenic influences, this work underscores the critical interplay between BVOC-driven aerosol evolution and cloud microphysics. These findings emphasize the need to account for dynamic aerosol changes over boreal forests in climate models, particularly under conditions where BVOCs drive efficient SOA formation. Expanding our understanding of these interactions is essential for accurately representing the contribution of boreal forest ecosystems to local and regional climate systems.
How to cite: Faivre, L., Tunved, P., Krejci, R., Bowen, P., Petäjä, T., Khadir, T., Partridge, D. G., and Heikkinen, L.: Sensitivity of Cloud Microphysics to BVOC-Induced Aerosol Growth Over Boreal Forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18823, https://doi.org/10.5194/egusphere-egu25-18823, 2025.
Introduction
Fine particulate matter (PM2.5) has a major impact on the climate1 and can affect human health.2 Though the major fraction of submicron PM is from organic compounds,3 their sources or organic precursor vapours, their atmospheric oxidation mechanisms and cross-reactions with inorganic trace gases remain unknown and are the focus of ongoing research. Volatile organic compounds of biogenic and anthropogenic origin can be oxidised in the atmosphere.4 The oxidation leads to a higher functionality, which reduces the volatility of the products, hence gas-to-particle conversion contributes to the formation of secondary organic aerosol (SOA) particles.2
Methods
From August 2021 to August 2022, we sampled PM2.5 glass fiber filters with a high-volume sampler for 12 hours at a rural background monitoring station. We measured the sample extracts in full scan MS with data dependent tandem mass spectrometry on a high-resolution hybrid quadrupole-Orbitrap mass spectrometer (Q Exactive Focus). Analytes were ionized with a heated electrospray ionisation source. For separation we used a ultra-high-performance liquid chromatography (Vanquish Flex) on a reversed phase column. To identify known and unknown compounds we used non-target analysis (Compound Discoverer 3.3), implementing fragmentation spectra search with mzCloud and the aerosolomics database. Hierarchical cluster analysis (HCA) and concentration-weighted trajectories (CWT) supports the interpretation of the results.
Results
The HCA groups the 6,080 detected compounds into two main clusters. Based on the chemical composition we interpret the compounds therein as of biogenic and anthropogenic origin. Sample clustering shows a clear seasonal cycle of the SOA mass and its chemical composition. During summer the SOA is dominated by biogenic compounds indicating a strong local influence of the vegetation. Anthropogenic compounds are relatively enriched during colder conditions with strong transport of air pollution during singular events. CWT show the air mass origins of these pollution events and allow for an interpretation of potential sources such as coal-fired power plants in eastern Germany and eastern Europe during stable, warm and dry weather conditions in Europe.
Our top-down approach could be valuable for understanding the variability and complexity of SOA processes and origins, helping to estimate anthropogenic influences on SOA formation, and thus for validating the anthropogenic aerosol forcing in Earth system models.
Literature
- 1. Shrivastava, M. et al. Recent advances in understanding secondary organic aerosol: Implications for global climate forcing. Rev. Geophys. 55, 509–559 (2017).
- 2. Fan, W. et al. A review of secondary organic aerosols formation focusing on organosulfates and organic nitrates. Journal of Hazardous Materials 430, 128406 (2022).
- 3. Jimenez, J. L. et al. Evolution of Organic Aerosols in the Atmosphere. Science 326, 1525–1529 (2009).
- 4. Atkinson, R. & Arey, J. Atmospheric Degradation of Volatile Organic Compounds. Chem. Rev. 103, 4605–4638 (2003).
How to cite: Thoma, M., Bachmeier, F., Knauf, K., David, J., Simon, M., and Vogel, A. L.: Seasonal analysis of organic aerosol composition resolves anthropogenic and biogenic sources at a rural background station in central Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15702, https://doi.org/10.5194/egusphere-egu25-15702, 2025.
The effective saturation vapor concentration (Log C*eff) of a molecule represents an important variable that governs the ability of molecule to nucleate new particles and partition into pre-existing aerosols. Thus, the saturation vapor concentration affects the chemical composition and the mass yields of ambient aerosol, ultimately affecting air pollution and climate.1 The determination of saturation vapor concentration is straight forward for small molecules, and those readily synthesized. However, the oxidation of volatile organic compounds creates a complex mixture of molecules, which is not easily separated to determine their saturation vapor concentration. Furthermore, SOA can often be mixed with other particles, containing species such as inorganic salts (e.g., ammonium sulfate) or mineral dust, impacting the non-ideality of the aerosols.
A thermal denuder coupled to a scanning mobility particle sizer (TD-SMPS) has been employed to determine the saturation vapor concentration of single component systems.2 However, the lack of chemical resolution prevents its applicability to determine the saturation vapor concentration of more complex organic mixtures such SOA.3 Consequently, considerably uncertainties still exists regarding the saturation vapor concentration of ambient SOA components. To address this issue, here we deployed an extractive electrospray ionization mass spectrometer (EESI-MS) coupled with a TD-SMPS (hence TD-SMPS+EESI) to provide molecular formula separation of complex mixtures together with their saturation vapor concentrations.4 We performed measurements on a complex mixture of known species (PEG-300) to demonstrate the ability to extract the saturation vapor concentration. We have generated SOAs derived from the ozonolysis of α-pinene in an atmospheric simulation chamber to extract their C*eff’s under three conditions: without seeds present, with ammonium sulfate seeds, and with a mixed iron/ammonium sulfate seeds. The presence of seed modulates the extracted C*eff values from SOA samples, suggesting there are non-ideal interactions between the underlying seed. Further, the presence of iron in the seed significantly exacerbates these non-ideal interactions, which indicates that knowing the underlying seed composition is important for understanding C*eff.
References:
(1) Ciarelli, G.; Haddad, I. E.; Bruns, E.; Aksoyoglu, S.; Möhler, O.; Baltensperger, U.; Prévôt, A. S. H. Constraining a hybrid volatility basis-set model for aging of wood-burning emissions using smog chamber experiments: A box-model study based on the VBS scheme of the CAMx model (v5.40). Geosci. Model Dev. 2017, 10 (6), 2303-2320. DOI: 10.5194/gmd-10-2303-2017.
(2) Kostenidou, E.; Karnezi, E.; Kolodziejczyk, A.; Szmigielski, R.; Pandis, S. N. Physical and Chemical Properties of 3-Methyl-1,2,3-butanetricarboxylic Acid (MBTCA) Aerosol. Environmental Science & Technology 2018, 52 (3), 1150-1155. DOI: 10.1021/acs.est.7b04348.
(3) Cappa, C. D.; Wilson, K. R. Multi-generation gas-phase oxidation, equilibrium partitioning, and the formation and evolution of secondary organic aerosol. Atmos. Chem. Phys. 2012, 12 (20), 9505-9528. DOI: 10.5194/acp-12-9505-2012.
(4) Bell, D. M.; Zhang, J.; Top, J.; Bogler, S.; Surdu, M.; Slowik, J. G.; Prevot, A. S. H.; El Haddad, I. Sensitivity Constraints of Extractive Electrospray for a Model System and Secondary Organic Aerosol. Analytical Chemistry 2023, 95 (37), 13788-13795. DOI: 10.1021/acs.analchem.3c00441.
How to cite: Bell, D., Garner, N., Top, J., Zhang, J., Salteri, F., Prevot, A., Kolozsvari, K., Ault, A., Lüchtrath, S., Ammann, M., and El Haddad, I.: Volatility of molecular components of aPinene SOA modulated by inorganic seed composition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17649, https://doi.org/10.5194/egusphere-egu25-17649, 2025.
Limonene is an abundant and highly reactive monoterpene that forms secondary organic aerosol (SOA) in the atmosphere. Limonene SOA from emerging anthropogenic sources, e.g., volatile chemical products, can deteriorate air quality in developed cities, yet the impacts may vary depending on its chemical properties. During the CHANEL campaign, atmospheric oxidation of limonene was simulated in the 270 m3 SAPHIR chamber to study the influence of reaction conditions and timescales on the molecular-level chemical composition of SOA. Different combinations of hydroxyl (OH.), nitrate (NO3.) and ozone (O3) oxidants were used in medium NOx for investigating day- and night-time oxidation conditions with each experiment spanning 10 – 12 hours. The SOA was transmitted from the chamber directly to an Ionicon CHARON-FUSION time-of-flight mass spectrometer that was operated in both H3O+ and ammonium (NH4+) modes with a periodic ion-switching measurement protocol. A positive matrix factorization approach was implemented via Source Finder (SoFi) to constrain the relative prominence of organic species in aerosol composition at different stages of each experiment. SOA evolved over several hours, yet with oxygenated species (CxHyOz) constituting 70 – 80% of the mass spectra that were dominated by compounds containing 5 – 10 carbon and 2 – 6 oxygen atoms. For daytime oxidation (OH+O3), C9H14O4 and C9H14O5 species were highly prominent in SOA formed immediately after the first precursor injection. The C9-species group also dominated peak SOA concentrations during night-time conditions. These were followed by O5 and O6-containing species that dominated the daytime tests after 4 – 5 hours of initial injection. After 7 – 8 hours, the molecular distribution looked considerably similar to that of SOA formed in O3-only oxidation tests with delayed appearance of C8H12O5 and C8H14O5 species that were likely multigenerational oxidation products. These observations suggest that properties of limonene SOA may continue to evolve over several hours following emissions and could influence their environmental impacts.
How to cite: Khare, P. and the CHANEL team: Detailed Molecular Characterization of Limonene Secondary Organic Aerosol Under Varying Oxidation Conditions and Reaction Timescales at the SAPHIR Chamber during CHANEL campaign, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20142, https://doi.org/10.5194/egusphere-egu25-20142, 2025.
Secondary organic aerosols (SOA) can affect global climate change and air quality. Explaining the formation of highly oxygenated organic molecules (HOM) is important due to their vital role in SOA formation. α-pinene as the most abundant monoterpene can react rapidly with oxidants (e.g. OH radicals and O3) and peroxy radicals (RO2) undergo fast unimolecular reactions to form HOM. For the reaction with the important daytime hydroxyl radical, previous studies (Shen et al., 2022; Luo et al., 2023) have shown that the H-abstraction pathway, which initially appears to be a minor reaction channel (~10%), contributes significantly to the HOM formation during the early stages of monoterpene oxidation reactions. However, the importance of the H-abstraction channel under different environmentally relevant conditions is unknown.
Our study focused on the OH oxidation reactions of a-pinene under different NOx and OH exposure conditions. The experiments were conducted in the Jülich Saphir STAR (Stirred atmospheric tank Reactor) chamber. The photolysis of hydrogen peroxide was used as OH source to ensure pure OH radical reactions without interference of ozone reactions. A multi-scheme chemical ionization inlet (MION) was coupled to an APi-Long-TOF-MS to characterize HOM. An increased mass fraction of H-abstraction pathway-related HOM (C10H15Ox and C10H15NOx) were observed among all HOM containing 10 C-atoms, with 0.7% at NO levels of ~0 ppb, 6% at 0.03 ppb NO, 22% at 1.0 ppb NO, and 31% at 2.2 ppb NO. Time series of these H-abstraction related HOM show a fast increase within the first minute after initiating reactions, which corresponds to direct formation from H-abstraction instead of secondary oxidation of accumulated pinonaldehyde. This could be explained by accelerated formation of alkoxy radicals promoted by RO2 radicals and NO reactions. Similar results were observed under OH exposure ranging from 1×106 to 1.3×107 molecule cm-3. Our study here shows the importance of the H-abstraction channel for the formation of HOM from OH oxidation of a-pinene, further emphasizing the role of NOx.
Luo, H., Vereecken, L., Shen, H., Kang, S., Pullinen, I., Hallquist, M., Fuchs, H., Wahner, A., Kiendler-Scharr, A., Mentel, T. F., and Zhao, D.: Formation of highly oxygenated organic molecules from the oxidation of limonene by OH radical: significant contribution of H-abstraction pathway, Atmospheric Chemistry and Physics, 23, 7297-7319, 10.5194/acp-23-7297-2023, 2023.
Shen, H. A.-O., Vereecken, L. A.-O. X., Kang, S. A.-O., Pullinen, I. A.-O., Fuchs, H. A.-O., Zhao, D. A.-O., and Mentel, T. A.-O.: Unexpected significance of a minor reaction pathway in daytime formation of biogenic highly oxygenated organic compounds, 2022.
How to cite: Wang, H., Shen, H., Baker, Y., Wu, R., Kang, S., Zanders, A., Zhao, D., Zorn, S. R., and Mentel, T. F.: Understanding the Importance of the H-Abstraction Channel in HOM Formation from OH Oxidation of α-pinene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13516, https://doi.org/10.5194/egusphere-egu25-13516, 2025.
The goal of the CAINA project is to investigate multiple aspects of aerosol-cloud interactions under high concentrations of reactive nitrogen. The CAINA project is a consortium project (7 PhD students) that combines in-situ and remote sensing observations of aerosols and clouds with high-resolution modeling to study the formation of CCN, cloud chemistry, and aerosol effects on clouds under high reactive nitrogen concentrations. This is chemical regime is starting to emerge in many regions on the globe following the strong reduction of SO2 emissions and consequently particulate sulfate concentrations. The presentation will give a short overview of the whole CAINA project and focus mainly on the results from 2 campaigns that were conducted at the AIDA cloud chamber to study the formation of aqueous SOA (AqSOA) under high reactive nitrogen concentrations.
The CAINA-AIDA campaigns are among the first experiments that investigate the influence of inorganic compounds on AqSOA formation under atmospherically relevant conditions, as opposed to more common bulk solution and flow-tube experiments. Seed aerosol consisting of inorganic salts (NaCl, NH4NO3, (NH4)2SO4) were nebulized as aqueous solution into the 84.5 m3 AIDA chamber at 90% RH. Subsequently, secondary organic aerosol (SOA) was generated from various precursors (a-pinene, limonene, isoprene) to study aqSOA formation for several hours under dark and irradiated conditions, followed by a cloud activation of ~ 8 min. The chemical composition of the organic gas and particle phase were characterized by high-resolution mass spectrometry, using both Iodide-CIMS and PTR-MS based techniques.
First results show that SOA mass yields are strongly enhanced at 90% RH compared to dry conditions, e.g. for a factor of more than 3 for the a-pinene experiments. This coincides with changes in chemical mass spectra, which are drastic for isoprene and more moderate for a-pinene. In the case of a-pinene, considerably higher concentrations of dicarboxylic acids and water-soluble oxidation products, such as DTAA, can be observed at 90% compared to dry conditions. At 90% RH the chemical composition of the SOA depends more strongly on the type of inorganic seed particle than at dry conditions. Particularly, nitrogen containing compounds as well as oxalic and malonic acid concentrations are clearly enhanced in NH4NO3 containing solutions compared to NaCl. A control experiment using NaCl seeds, where NH3 and NOx were added in the gas phase, gives a first indication that some of these compounds are preferentially formed in the liquid phase, but others in the gas phase with subsequent partitioning into the liquid phase. The effects of UV illumination and subsequent cloud activation on SOA composition will be also be presented.
How to cite: Dusek, U., Fu, J., Saathoff, H., Kroese, W., Holzinger, R., Fry, J., and Ou, H. and the the CAINA team: Aerosol Cloud Interactions in a Nitrogen-dominated Atmosphere (CAINA) – first highlights from AIDA cloud chamber studies , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16078, https://doi.org/10.5194/egusphere-egu25-16078, 2025.
Biomass burning organic aerosols (BBOA) are a major contributor to organic aerosols in the atmosphere. Viscosity is an important property of BBOA, as it influences many of the processes it is involved in in the atmosphere; this includes but is not limited to particle growth rates, reaction and mixing rates, and cloud condensation nucleation. As BBOA is transported through the troposphere, it undergoes photochemical aging due to reactions with atmospheric oxidants such as OH and O3. Recently it has been shown that the viscosities of some aerosols can be enhanced through atmospheric aging processes. However, research on the influence of atmospheric aging on BBOA is still limited.We used a Potential Aerosol Mass oxidative flow reactor (185 nm mode) to expose BBOA to high concentrations of OH and O3, simulating the equivalent of 1 to 8 days in the troposphere. We measured the viscosity of the photochemically aged BBOA with the poke-flow viscometry technique, and found that aging increased the viscosity of BBOA. After 1 day of aging, the viscosity of BBOA increased by several orders of magnitude. However, further aging up to 8 days saw a less dramatic increase in viscosity, with no noticeable increase between 5 days and 8 days. We also measured the carbon oxidation state of the BBOA with high-resolution aerosol mass spectrometry, and the trend in increasing oxidation state reflected the trend in viscosity. This suggests that the most dramatic changes in the physicochemical properties of BBOA occur within the first days or hours of aging, after which oxidation becomes a less significant aging mechanism. These results have implications for how the aging and eventual fate of BBOA should be treated in models.
How to cite: Gerrebos, N., Browning, L., Nikkho, S., Zaks, J., Wu, C., and Bertram, A.: Photochemical Aging Enhances the Viscosity of Biomass Burning Organic Aerosol, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14134, https://doi.org/10.5194/egusphere-egu25-14134, 2025.
Posters on site: Fri, 2 May, 08:30–10:15 | Hall X5
This study investigates the composition, sources, and transformation processes of organic aerosols (OA) in Xitun, a near-industrial urban area in Taichung City, Taiwan, during a field measurement campaign in November 2023. Using a real-time Aerosol Mass Spectrometer (AMS) combined with Positive Matrix Factorization analysis, five organic aerosol components are identified: hydrocarbon-like OA (HOA), aged hydrocarbon-like OA (aged-HOA), semi-volatile oxygenated OA (SV-OOA), low-volatility oxygenated OA (LV-OOA), and background species. Oxygenated OA (OOA), primarily comprising secondary organic aerosol (SOA) formed through the oxidation of gas-phase precursors, accounted for 43–60% of the total OA mass, while HOA and aged-HOA, mainly derived from primary organic aerosol (POA) emitted by traffic and industrial sources, contributed approximately 30% of the total OA mass. To simulate OA evolution, a two-box model is developed, incorporating physical processes, including advection and entrainment, which are characterized using CO concentration simulations. The results align closely with those from the Community Multiscale Air Quality (CMAQ) model. With the physical processes well-constrained, the chemical processes are added to the model to quantify the chemical production and loss of selected volatile organic compounds (VOCs) and the formation of semi-volatile organic compounds (SVOCs) species, distinguishing between anthropogenic and biogenic VOC sources contributing to SOA formation. The oxidation rates of OA will be further determined through model simulations constrained by AMS observations. This study offers valuable insights into the sources, oxidation processes, and evolution of organic aerosols, providing a basis for comprehensive modeling approaches and enhancing our understanding of their impacts on air quality and human health.
How to cite: Chen, F., Hung, H.-M., Tsai, P.-W., and Chou, C. C.-K.: Integrating Observations and Model Simulations to Uncover Chemical and Physical Drivers of Organic Aerosol Composition in Urban Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4424, https://doi.org/10.5194/egusphere-egu25-4424, 2025.
Atmospheric organic aerosol contains unique information about the origin, reaction regimes and the atmospheric conditions of the air mass that is sampled. Extracting the maximum amount of information from every sample can be a challenging task. Traditional targeted analysis of a few selected compounds is not up to the task. Therefore, untargeted analysis is becoming increasingly popular for analyzing complex atmospheric aerosol samples.
This poster presents an in-house developed specialized software that allows to analyze full-scan / AIF MS measurements that were previously too complex for direct human interpretation. In contrast to traditional measurements, this mode provides the maximum amount of information about the sample without any unnecessary restrictions, allowing to create digital databases of complete organic aerosol samples. With continuous improvement of the analysis program, this allows to utilize data of samples that were measured today to be used in the future for other projects and to be analyzed with different methods and programs. The custom software can convert such full-scan / AIF LC-UHRMS data into a human readable format and visualize the data in a comprehensive way. Utilizing this approach allows to capture the maximum amount of data in a single measurement reducing both manual labor and device utilization.
How to cite: Karbach, N., Breuninger, A., Vogel, A., and Hoffmann, T.: Application example of a novel untargeted LC-UHRMS processing approach for the analysis of organic aerosols, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19908, https://doi.org/10.5194/egusphere-egu25-19908, 2025.
This study investigates the fluorescent properties of the water-soluble organic aerosol (WSOC) in PM2.5 and PM10 from the city of Karlsruhe, Germany. Major fluorescent components were identified by excitation–emission matrix spectroscopy with parallel factor analysis in this study. The lower humification index (HIX) value of PM2.5 and PM10 (0.72 ± 0.13, 0.77 ± 0.06), together with lower biological index (BIX) value of PM2.5 and PM10 (0.85 ± 0.07, 0.84 ± 0.06) and fluorescence index (FI) value of PM2.5 and PM10 (1.34 ± 0.16, 1.32 ± 0.06) showed that fluorescent source of WSOC influenced by the primary aerosol’s emissions (such as vehicles emission and heating) and natural dust (such as road and building contributions). The fluorescent components identified of the water-soluble organic aerosol show that Component 1 (Ex < 240/Ex = 323 nm, Em = 408 nm) and Component 2 (Ex = 248/362 nm, Em = 469 nm) can be identified as Highly oxygenated humic-like substance (HULIS) components. Component 3 (Ex <240 nm, Em = 363 nm) is associated with biomass burning with less-oxygenated HULIS component and Component 4 (Ex = 242/269 nm, Em = 311 nm) is substances from multiple sources of mixtures. Relative contribution of Highly oxygenated HULIS components (Component 1 & Component 2) in heating period (52.7%) is lower than in non-heating period (67.6%); Biomass burning with less-oxygenated HULIS component (Component 3) had the highest contribution (41%) in winter and the phenol- and naphthalene-like component (Component 4) had lower contributions and in different periods.
How to cite: Wang, X. and Norra, S.: Chemical composition and source identification of fluorescent components in water-soluble organic carbon in the city of Karlsruhe, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5118, https://doi.org/10.5194/egusphere-egu25-5118, 2025.
Vaporization enthalpy (ΔHv) is an essential thermodynamic parameter that governs the phase transitions of organic compounds, linking their volatility to their temperature-dependent gas–particle partitioning. Secondary organic aerosol (SOA) was produced by the photooxidation of aromatic volatile organic compounds (VOCs) using a newly developed Teflon flow reactor. SOA volatility was assessed using a thermodenuder and parametrized using a kinetic mass transfer model. This study examined the effects of aging on the SOA volatility, chemical composition, and mass yield volatility. Variations in the ΔHv values of SOA driven from different aromatic VOCs were linked to the chemical structure of their aromatic precursors. Elevated hydroxyl exposures increased the oxygen to carbon ratio of SOA, while ΔHv remained relatively consistent, likely due to fragmentation offsetting the effects of increased oxidation. SOA yields were influenced by the degree of alkyl substitution and the chain length of alkyl substituents in the aromatic VOCs.
How to cite: Lim, H.-J., Park, J.-H., Lim, J., Ullah, A., and Kim, S.: Volatility and Atomic Ratio of Aromatic Secondary Organic Aerosol: Effects of Aging and Alkyl Substituents, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5301, https://doi.org/10.5194/egusphere-egu25-5301, 2025.
From October 2024 to October 2025, the Gliwice Radiocarbon Laboratory is carrying out a project titled “High-resolution, seasonal studies of carbon sources in atmospheric dust using the radiocarbon method” (project number 2024/08/X/ST10/00655) funded by the National Science Centre (NCN).
The aim of the pilot study is to analyse radiocarbon concentration in atmospheric dust samples collected in Gliwice with weekly (autumn-winter) and two-week (spring-summer) resolution. Based on the results, we want to determine the seasonal contribution of different carbon emission sources.
Air pollution has a very negative impact on the human cardiorespiratory system including reducing resistance to bacterial or viral infections [1]. Particulate matter is a major contributor to overall air pollution. It consists of solid and liquid particles suspended in the atmosphere. Particularly dangerous are PM10, PM2.5 and PM1, which refers to particles smaller than 10 μm, 2.5 μm and 1 μm in diameter, respectively.
Gliwice (50°17′37.1′′ N 18°40′54.9′′ E) is located in southern Poland, within the Silesian Voivodeship in the industrial region of Upper Silesian conurbation. Upper Silesia is a densely populated and highly industrialized region of Poland. However, due to the high levels of air pollution, the Silesian region has the shortest life expectancy, as well as the highest rates of premature births and genetic birth defects in Poland [2].
Radiocarbon (14C) is one of three isotopes of carbon. It is the only one that undergoes radioactive decay (with a half-life of 5730 years), so its concentration in organic matter is closely related to its decay time. Burning fuels releases two types of carbon into the air: modern carbon (from burning biomass) and fossil carbon (from burning fossil fuels). Fossil fuels were formed from organic matter millions of years ago, so the concentration of radiocarbon in them is much lower than in biomass.
One of the methods used to determine the concentration of 14C is Accelerator Mass Spectrometry (AMS). Accelerator mass spectrometry is a highly sensitive method for counting carbon atoms and may be precise method of identifying carbon sources in atmospheric PM [3].
[1] M. Urrutia-Pereira, C. A. Mello-da-Silva, and D. Solé, COVID-19 and air pollution: A dangerous association?, Allergologia et Immunopathologia, vol. 48, no. 5, pp. 496–499, 2020, doi: 10.1016/j.aller.2020.05.004.
[2] E. Brągoszewska and A. Mainka, Impact of Different Air Pollutants (PM10, PM2.5, NO2, and Bacterial Aerosols) on COVID-19 Cases in Gliwice, Southern Poland, IJERPH, vol. 19, no. 21, p. 14181, 2022, doi: 10.3390/ijerph192114181.
[3] G. Zhang, J. Liu, J. Li, P. Li, N. Wei, and B. Xu, Radiocarbon isotope technique as apowerful tool in tracking anthropogenic emissions of carbonaceous air pollutants and greenhouse gases: A review, Fundamental Research, vol. 1, no. 3, pp. 306–316, 2021, doi: 10.1016/j.fmre.2021.03.007.
How to cite: Ustrzycka, A., Piotrowska, N., Jędrzejowski, M., Kłusek, M., and Mainka, A.: High-resolution, seasonal studies of carbon sources in atmospheric dust in Gliwice, using the radiocarbon method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5677, https://doi.org/10.5194/egusphere-egu25-5677, 2025.
New particle formation (NPF) is the largest source of atmospheric aerosols with respect to their number and has a large impact on the global climate and human health. During this process, low-volatility vapors form stable molecular clusters, which subsequently grow through the condensation of additional molecules. Inorganic acids such as sulfuric acid or iodic acid are often the main drivers of clustering. While organic molecules contribute significantly to the growth processes, it remains unclear at what stage they start to contribute to NPF, i.e., the exact clustering routes of organic or organic-inorganic mixtures are unknown. This is in part due to the fact that current state-of-the-art mass spectroscopic methods only provide compositional information and not information on the actual structure of the molecular clusters or the functionalization of the growing nanoparticles. However, ultimately, the interaction between functional groups defines the properties of the molecular clusters [1].
Here, we use matrix isolation Fourier transform infrared spectroscopy (MI-FTIR) as a new tool to investigate the formation of molecular clusters. It was previously demonstrated [2,3] that MI-FTIR is a reliable tool for studying small molecular clusters' structure. In the present work, we investigate organic precursor vapors, their oxidation products, and newly formed clusters as stabilized in inert noble-gas matrices. Due to cryogenic temperatures, rotational transitions are suppressed, making the identification of the cluster constituents and the molecular structure of the cluster easier compared to conventional gas-phase FTIR.
The current study focuses on NPF involving α-pinene, a monoterpene that is recognized to be rapidly convertible to extremely low volatile organic compounds (ELVOC). Spectra of α-pinene and first-order oxidation products from α-pinene, such as pinic and pinonic acid, isolated in noble gas matrices are presented. The infrared absorption bands are compared to calculations based on density functional theory (DFT), as specific bands can be associated with the presence of multimers in the matrix. This gives insights into potential cluster formation pathways and can be used to benchmark the most widely used DFT approaches with experimental data. Altogether, we demonstrate that our MI-FTIR setup provides a new approach to NPF studies, complementing mass spectrometry-based measurements.
References:
[1]: Stolzenburg, D. et al. Atmospheric nanoparticle growth. Rev. Mod. Phys. 95, 045002 (2023).
[2]: Köck, E.-M. et al. Alpha-Carbonic Acid Revisited: Carbonic Acid Monomethyl Ester as a Solid and its Conformational Isomerism in the Gas Phase Chem. Eur. J. 26, 285 (2020).
[3]: Dinu, D. F. et al. Increase of Radiative Forcing through Midinfrared Absorption by Stable CO 2 Dimers? J. Phys. Chem. A 126, 2966–2975 (2022).
How to cite: Enders, V., Dinu, D. F., Grothe, H., Podewitz, M., Tischberger, M., and Stolzenburg, D.: Freezing atmospheric organic nucleation: A matrix isolation study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9109, https://doi.org/10.5194/egusphere-egu25-9109, 2025.
Atmospheric PM10 and benzo(a)pyrene (BaP) concentrations in Manlleu (NE Spain) have remained high from 2008–2023, frequently exceeding EU limit/target values, and reaching BaP levels up to six times higher than urban averages in Spain. Furthermore, PM speciation campaigns were carried out in 2013, 2014-2015, 2016-2017 and 2021-2022. Chemical mass closure for autumn-winter showed a consistent PM10 composition for the different PM speciation campaigns, comprising 46–53% organic matter (OM), 18–26% secondary inorganic aerosol (SIA), 13–23% mineral matter (MM), and 5-9% elemental carbon (EC). Trend analysis revealed very light decrease and constant concentrations for PM10 and BaP, respectively over the study period, emphasizing the need for compliance with current and forthcoming EU air quality directives, the last aiming to halve PM10 limit values. Source apportionment of samples of the sporadic campaigns identified biomass burning (BB, 17.5 µg m-3, 48%) and MM and industry (16.3 µg m-3, 44%) as the main autumn-winter PM10 contributors, with high SIA concentrations attributed to several factors, including high ammonia (NH3) emissions. Local topography and meteorological conditions contribute to aggravate PM10 pollution. While metal concentrations have decreased since 2013, suggesting reduced industrial emissions, persistently high OM and EC concentrations indicate ongoing issues with BB emissions from domestic, commercial, and agricultural sources. Online analysis of black carbon (BC) and non-refractory PM1 components during winter 2016–2017 confirmed domestic and commercial BB as the primary sources of the BB contributions. These findings highlight the need of the implementation of more effective measures in reducing BB and agricultural/farming NH3 emissions. This study highlights the relevance of these issues for similar towns, the probable unremitting problem over the last decade, and the necessity of enhanced monitoring in small cities and policy actions to meet air quality standards under the new EU directive.
How to cite: Canals-Angerri, A., Via, M., Lara, R., Alastuey, A., Minguillón, M. C., Pandolfi, M., van Drooge, B. L., and Querol, X.: Causes of the unremitting high ambient levels of PM10 in a suburban background site in NE Spain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10433, https://doi.org/10.5194/egusphere-egu25-10433, 2025.
Formaldehyde, a short-lived species, is used as an indicator of secondary organic aerosol (SOA) formation due to its involvement in the chemical reactions that produce SOA. While formaldehyde is emitted during fires, observed concentrations in regions like the Amazon are often too high to be explained solely by combustion, suggesting additional sources. Previous research has shown that during the 2010 fire season in the Amazon, SOA was found to account for 52% of total organic aerosol (OA) emissions, highlighting the importance of SOA in the region's aerosol budget.
In this study, we extend this previous work by analyzing satellite observations of formaldehyde, aerosol optical depth (AOD), and single scattering albedo (SSA) across multiple years. We examine whether higher formaldehyde concentrations, indicative of more active SOA formation, continue to correlate with higher AOD and SSA, suggesting increased SOA mass and the presence of non-absorbing aerosols.
Also, we investigate whether these relationships hold in other regions, such as Southern Africa, where SOA contributions to OA emissions were found to be lower. Additionally, we explore the temporal variability of the formaldehyde-AOD-SSA correlation, assessing whether these associations are consistent across different fire seasons and years. This analysis aims to uncover potential temporal trends in SOA formation dynamics and better understand the regional and inter-annual variability of these relationships.
How to cite: Román de Miguel, F., Schutgens, N., and Zhong, Q.: Formaldehyde as a SOA Indicator: Regional and Temporal Variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13194, https://doi.org/10.5194/egusphere-egu25-13194, 2025.
Secondary organic aerosol (SOA), formed by oxidation of volatile organic compounds and gas-particle partitioning, account for a large proportion of atmospheric submicron aerosol mass, and hence have a significant impact on clouds and global climate. The impact depends on the concentration and the cloud condensation nuclei (CCN) activity of SOA. CCN activity of SOA is determined by its particle size and hygroscopicity parameter (κ) characterizing the properties of different chemical composition. Despite a number of chamber studies on SOA formation and its CCN activity, few studies have simulated particle size and chemical composition of SOA and thus CCN concentration based on explicit chemical mechanism. To bridge this gap, in this study we used the box model PyCHAM to explicitly simulate the α-pinene ozonolysis reaction in an atmospheric reaction chamber, and compared the simulated SOA mass and number concentrations, chemical composition, particle size distribution, κ and CCN concentration with experimental measurements. In general, the simulation underestimated SOA mass concentration and overestimated oxygen-to-carbon (O:C) and hydrogen-to-carbon (H:C), indicating the potential role of particle-phase reactions in SOA formation. The simulated SOA number concentration, particle nucleation and subsequent growth agreed well with measurement, whereas the geometric mean diameter was slightly overestimated, which partly due to the simplified microphysical processes like coagulation in the model. Moreover, the simulated κ and CCN concentration were also in consistent with measurements. This study reveals the key chemical processes that may influence SOA formation, as well as the importance of considering detailed chemical composition and particle size distribution for CCN simulations based on the explicit chemical mechanism.
How to cite: Song, Z., Zhang, C., Shen, H., Mentel, T., and Zhao, D.: Explicit simulation of chemical composition, size distribution and cloud condensation nuclei of the secondary organic aerosol from α-pinene oxidation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14850, https://doi.org/10.5194/egusphere-egu25-14850, 2025.
Cooking, one of key human activities, has been known to contribute significantly to ambient aerosol in both the indoor and outdoor settings. In certain urban environments, cooking Organic Aerosol (OA) have been documented to drive outstanding smog events. On the other hand, more research is necessary on induced health effects by such aerosol. A controlled, cooking and grilling experiment was performed in June 2024 in an effort to physically and chemically characterize cooking aerosol and derive estimations on their oxidative potential. Along the way, the response of the Aerosol Chemical Speciation Monitor (ACSM) to direct cooking emissions was assessed, while reference single source mass spectra were acquired, to be used as an important aid for constraining algorithms performing source apportionment of ambient aerosol. Various cooking conditions (gas vs charcoal grill, frying pan) were tested on different types of food (vegetables, steaks, burgers, chicken, fish, fries, etc). The experimental setup included an ACSM, a 7-wavelength filter-based absorption photometer (AE-33 aethalometer), a Scanning Mobility Particle Sizer (SMPS) providing number size distributions and filter sampling of PM2.5 aerosol to perform off line detailed composition analysis and oxidative potential estimates.
Acquired OA mass spectra presented similarities, being dominated by prominent signals at m/z = 41, 43, 55 and 57, linked to the fragmentation of alkyls and specifically the CnH2n+1 and CnH2n-1 ion series. All cooking spectra acquired, share the common feature of an m/z = 55 over m/z = 57 contribution ratio (i.e. f55/f57) well above unity. The contribution of significant signal at m/z = 60, a typical tracer of the fragmentation of levoglucosan, related to the pyrolysis of cellulose was evident in the mass spectra of charcoal grilled food. Interestingly non negligible, nevertheless low contributions at m/z = 60, were also found for food cooked on a gas burner grill. Grilling vegetables yields pronounced contributions at higher m/z values (e.g. for m/z =67, 69, and 71). The largest contribution at m/z = 44 in the mass spectrum, was observed when sampling aerosol from burning the residual fat from a heated pan.
Acknowledgement: This work is supported by the European Union's Horizon Europe research and innovation programme under the Marie Skłodowska-Curie Postdoctoral Fellowship Programme, SMASH co-funded under the grant agreement No. 101081355. The SMASH project is co-funded by the Republic of Slovenia and the European Union from the European Regional Development Fund.
How to cite: Stavroulas, I., Yus-Diez, J., Via, M., Glojek, K., Drinovec, L., Manousakas, M. I., Prévôt, A., and Močnik, G.: Characterization of cooking aerosol through an ensemble of measurements targeting chemical composition, physical properties and oxidative potential., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17091, https://doi.org/10.5194/egusphere-egu25-17091, 2025.
Numerous studies have identified airports as key sources of ultrafine particles (UFPs – aerodynamic diameter <100 nm) [1] [2] [3] [4], yet the chemical composition and formation mechanisms of these particles remain poorly understood. In a previous study we characterized the organic chemical composition of aviation-related UFPs by non-targeted screening and identified jet engine oils as a significant contributor [5]. Besides quantifying the mass contribution of jet oils to ambient UFPs originating from Frankfurt International Airport, we were able to show the new-particle formation ability of jet engine oils by laboratory based thermodenuder-experiments, using a common synthetic lubrication oil [6].
Here, we show the spatial distribution of jet engine oil emissions emerging from Frankfurt Airport, which is the largest airport in Germany. We conducted a quantitative analysis of two different types of synthetic esters which are used as base stock in jet engine oils to monitor their prevalence in the region. Hence, we collected particles with diameters <100 nm at five different locations around the airport with varying distances to the airport grounds. We sampled UFPs on aluminium-filters using multiple 13-stage cascade impactor systems (Nano-MOUDI) in the direct vicinity of the airport runways and up to a distance of 20 km. Collection took place in summer and winter periods to observe a possible seasonal variability and at three stations in parallel to monitor the simultaneous spatial extent and wind direction dependence. In parallel to filter sampling, the particle size distribution was monitored to determine the size-resolved total particle mass. Quantitative characterization of UFPs in the size ranges 10–18 nm, 18–32 nm, 32–56 nm and 56-100 nm was performed by external calibration applying liquid chromatography (UHPLC) separation, followed by heated electrospray ionization (HESI) and mass analysis using a high-resolution Orbitrap mass spectrometer (HRMS). The two homologous ester series of pentaerythritol- (C25-40H44-74O8) and trimethylolpropane (C26-36H48-68O6) esters were quantified by external calibration using one ester compound (C29H52O8). Since different types of Nano-MOUDI samplers (NanoMOUDI Model 115; NanoMOUDI-II 122R & 125R) were in use, we compared their sampling efficiency for each stage in order to make later corrections. Over a period of two weeks, we collected parallel filter samples at the same station and compared the collected engine oil mass accordingly. Results indicate that aircraft engine oils are detectable across the full UFP size range, with the highest concentrations observed at airport grounds in the 32-56 nm particle size fraction. Sulfate concentrations show a similar picture regarding the size distribution. To accurately account for these variations in size fractions, it is crucial to consider the differing collection efficiencies as these can vary significantly depending on the sampler model and design.
[1] Habre, R., et al. (2018) Environ. Int., 118, 48–59.
[2] Fushimi, A., et al. (2019) Atmos. Chem. Phys., 19, 6389–6399.
[3] Stacey, B., (2019) Atmos. Environ., 198, 463–477.
[4] Rivas, I., et al. (2020) Environ. Int., 135, 105345.
[5] Ungeheuer, F., et al. (2021) Atmos. Chem. Phys., 21, 3763–3775.
[6] Ungeheuer, F., et al. (2022) Commun Earth Environ 3, 319.
How to cite: Ungeheuer, F., van Pinxteren, D., and L. Vogel, A.: Distribution of jet engine oil emissions in the urban surroundings of Germany's largest airport, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17234, https://doi.org/10.5194/egusphere-egu25-17234, 2025.
New particle formation (NPF) contributes to about half of all cloud condensation nuclei worldwide (Gordon et al. 2017) and plays a critical role in understanding anthropogenic climate change (IPCC, 2021). A keymechanism driving atmospheric NPF is acid-base nucleation, primarily involving anthropogenic sulfuric acid and ammonia (Kirkby, 2023). Nonetheless, oxygenated organic molecules (OOM), produced from oxidation of terpenes like alpha-pinene (Kirkby et al. 2016) or – in the upper troposphere – isoprene (Shen et al. 2024), can drive rapid particle nucleation in the complete absence of sulfuric acid, a process known as pure biogenic nucleation.
Shen et al. (2024) found that that the addition of trace amounts of sulfuric acid to isoprene-driven NPF enhanced the nucleation rates up to 100-fold. However, so far, a synergistic effect of sulfuric acid with alpha-pinene OOM (AP-OOM) has not been reported.
This study focuses on measurements from the CERN CLOUD chamber, examining NPF from alpha-pinene in the presence of trace sulfuric acid concentrations ranging from 104 to 106 cm−3, levels that are commonlyfound in pristine regions. Experiments were conducted at -10°C and +5°C, typical of the cool boundary layer of boreal forest regions, and in the absence of any base vapors such as ammonia or amines.
Gas-phase concentrations were monitored using various CI-Time-Of-Flight mass spectrometers (Nitrate-CIMS, Fusion PTR, STOF PTR-MS, FIGAERO), while naturally charged nucleating clusters were analyzed using an APi-TOF. Aerosol particle distributions were characterized with an array of particle measurement instruments (scanning PSM, CPC, NAIS, nSMPS, lSMPS, DMA-Train). Nucleation and growth rates were determined under varying concentrations of alpha-pinene OOMs and sulfuric acid.
This study presents nucleation and growth rates from AP-OOM in the presence of trace sulfuric acid and compares the rates with those from pure AP-OOM and pure sulfuric acid, respectively.
Gordon, H. et al. (2017) Causes and importance of new particle formation in the present-day and preindustrial atmospheres. J. Geophys. Res. Atmos. 122, 8739-8760.
IPCC (2021) Climate Change 2021 – The Physical Science Basis: Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press.
Kirkby, J. et al. (2016) Ion-induced nucleation of pure biogenic particles. Nature 533, 521-526.
Kirkby, J. et al. (2023) Atmospheric new particle formation from the CERN CLOUD experiment. Nature Geoscience 16, 948-957.
Shen, J. et al. (2024) "New particle formation from isoprene under upper-tropospheric conditions." Nature 636.8041, 115-123.
How to cite: Sommer, E., Almeida, J., Simon, M., Caudillo-Plath, L., Yu, W., Junninen, H., Zheng, Z., Judmaier, B., Shen, J., Dada, L., and Kirkby, J. and the CLOUD Collaboration: New particle formation from alpha pinene and trace sulfuric acid in the CERN CLOUD chamber, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19500, https://doi.org/10.5194/egusphere-egu25-19500, 2025.
Each year Delhi experiences extremely poor air quality in the post-monsoon season due to large scale stubble burning in the upwind states of Punjab and Haryana, excessive firecracker uses during the Diwali festival, and unfavorable meteorological conditions such as shallow inversions over emission sources. Numerous studies have reported severe haze episodes in Delhi, often linking them to long-range transport of biomass burning aerosols from these upwind regions. In the present study, we investigate the variability in chemical composition of non-refractory PM2.5 using a Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) and black carbon (BC) aerosols using an Aethalometer AE31 at an upwind side of Delhi-NCR in Sonipat, Haryana (28.9° N, 77.1° E) during the stubble burning period and Diwali time (25 Oct 2023 to 15 Nov 2023). We quantified the mass concentrations of biomass burning tracer species, such as levoglucosan, mannosan, and potassium (K+), along with other chemical constituents. The daily average concentrations of levoglucosan, mannosan and K+ in NR-PM2.5 were 1.28 ± 1.27, 0.02 ± 0.01 and 5.38±4.57 μg m−3, respectively. Preliminary analysis indicates higher concentration of biomass burning tracers, carbonaceous aerosols, and secondary inorganic aerosols during nighttime as compared to daytime. The daily average mass concentrations of Organics are 108±48.5 and 70.2±49.7 μg m−3, and BC are 18.8±86.0 μg m−3 and 24.0±10.2 μg m−3 during biomass burning and Diwali festival period, respectively. Additionally, we are conducting source apportionment analysis using models such as Positive Matrix Factorization (PMF) to identify various sources contributing to PM2.5 concentrations over the region. More results with greater details will be presented.
How to cite: Singh, V., Ganguly, D., Rathore, J., Dey, S., and Gani, S.: Chemical Characterization and source apportionment of PM2.5 over an upwind site of Delhi during Biomass Burning and Diwali Festival period , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-853, https://doi.org/10.5194/egusphere-egu25-853, 2025.
The partitioning of organic vapors between the gas and the condensed phase is a crucial process influencing the formation of organic aerosol (OA). Investigating the key factors affecting partitioning is quite challenging because of the disparate range and variability of atmospheric conditions (temperature, relative humidity, precursors etc.). Therefore, the combination of chamber experiments and chemical box models allows for investigating a specific OA formation via gas-aerosol partitioning under controlled experimental conditions. On this basis, we have developed a novel multiphase chemical box model, the so-called MESSy DWARF, to simulate chamber experiments. MESSy DWARF is part of the MESSy (Modular Earth Submodel System) modeling framework. This allows the box model to utilize the full range of process parameterizations available in MESSy, which originally have been designed for global atmospheric chemistry simulations.
Here, we present a MESSy DWARF application to simulate a chamber experiment for studying gas-to-particle partitioning of organic molecules under humid conditions. The kinetic partitioning scheme is based on the Schwartz mass transfer coefficient and is governed by the liquid water content (LWC) and water solubility. Losses of organic vapors to the walls have been included. To assess the kinetic partitioning of the model, we selected an experiment of alpha-pinene photooxidation with the presence of ammonium sulfate seeds at 50 % relative humidity. This experiment was conducted in SAPHIR-STAR, an indoor continuous glass tank chamber at Forschungszentrum Jülich. The model simulations emphasize the significance of LWC for organic aerosol concentration. Thus, the model has been expanded to include capabilities for estimating LWC from aerosol number counts and inorganic mass concentrations and the wet radius. LWC is calculated as the difference between the average wet and dry volumes of the particles. The volume of dry particles is estimated by use of either densities or grow factors of solute components.
The analysis of the model results indicates a correlation between NO-levels and water solubility of alpha-pinene oxidation products. As the level of NO decreases, the reaction pathways of the organic peroxy radicals shift towards the production of species bearing carboxyl and hydro(pero)xyl functional groups. The enhanced production of water-soluble products is consistent with the observed increase in organic mass at low NO. The preliminary success in simulating the multiphase chamber experiment indicates the potential for further model applications.
How to cite: Do, D. H., Kerkweg, A., and Taraborrelli, D.: Modelling aerosol chamber experiments with kinetic gas-to-particle partitioning of organic molecules under humid conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9180, https://doi.org/10.5194/egusphere-egu25-9180, 2025.
Organic peroxides are health-relevant organic components in secondary organic aerosols (SOA), which is also a major compound class substantially contributing to SOA mass. However, their molecular identification and characterization in SOA is highly challenging and uncertain. Ozonolysis of alkenes is known to produce reactive intermediates ─ stabilized Criegee intermediates, and their subsequent bimolecular reactions with various carboxylic acids can form α-acyloxyalkyl hydroperoxides (AAHPs), which is considered a major class of organic peroxides in SOA. Here we use this knowledge to synthesize a number of atmospherically relevant AAHPs through liquid-phase ozonolysis from either α-pinene or 3-carene in the presence of ten different carboxylic acids. These AAHPs with diverse structures are identified individually by liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS). AAHPs were previously thought to decompose quickly in aqueous environment such as cloud droplets, but we demonstrate here that AAHPs hydrolysis rates are highly compound-dependent with rate constants differing by 2 orders of magnitude. Some synthesized AAHPs were further identified via targeted analysis in monoterpene SOA samples collected from laboratory flowtube experiments.
Another focus of this study is to expand the molecular identification ability of organic peroxides in SOA, which goes beyond peroxide standards. Iodide is known to selectively react with peroxides, and their kinetics are fundamentally determined by the structures of individual peroxides. We extrapolate this knowledge and develop a novel analytical strategy for molecular characterization of organic peroxides in SOA via iodometry kinetic experiments using LC-HRMS. Through non-targeted analysis, more than 300 organic peroxides are identified in α-pinene SOA with unprecedented accuracy of their chemical formula. Their reactivity with iodide is highly compound-dependent and can vary 4 orders of magnitude. Our study improves the molecular-level identification and understanding of organic peroxides in SOA, offering numerous opportunities for further investigation into their formation chemistry, atmospheric transformation, and health impact.
How to cite: Li, K., Zheng, Z., Resch, J., and Kalberer, M.: Synthesis and Characterization of Organic Peroxides from Monoterpene-derived Secondary Organic Aerosol, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11178, https://doi.org/10.5194/egusphere-egu25-11178, 2025.
Nitrogen-containing compounds constitute up to 77% of the molecular species in organic aerosols (OA), contributing approximately 40% to the total OA mass. Despite this significant abundance, research on characterizing organic nitrogen (ON) in particulate matter with an aerodynamic diameter of 2.5 micrometers or less (PM2.5) has predominantly focused on water-soluble ON (WSON) or specific subgroups due to the complexity of ON and challenges in identifying its diverse sources. Beyond its abundance, ON plays an essential role in new particle formation, secondary organic aerosol (SOA) formation, and serves as a major atmospheric source of reactive nitrogen, potentially disrupting the global nitrogen cycle.
This study aimed to investigate the spatial distribution and source apportionment of ON in PM2.5 across four sites in Northeast Asia. PM2.5 samples were collected daily for one month in the fall of 2023 from Ulaanbaatar (Mongolia), Beijing (China), Seoul, and Seosan (South Korea). ON concentrations were measured using a simultaneous ON and inorganic nitrogen (IN) detection system, consisting of a thermal aerosol carbon analyzer and a chemiluminescence NOx analyzer (Yu et al., 2021). The average concentrations were 0.35 ± 0.17 μgN/m³ in Ulaanbaatar, 0.22 ± 0.12 μgN/m³ in Beijing, 0.20 ± 0.08 μgN/m³ in Seoul, and 0.28 ± 0.10 μgN/m³ in Seosan, corresponding to 39 ± 15%, 21 ± 15%, 23 ± 12%, and 23 ± 11% of total aerosol nitrogen in PM2.5, respectively. The correlation analysis of water-soluble organic carbon (WSOC) and water-insoluble organic carbon (WISOC) in PM2.5 with ON showed that in Ulaanbaatar ON correlated well only with WISOC, in Seoul only with WSOC, and in Beijing and Seosan with both WSOC and WISOC. The correlation analysis between IN and ON revealed the strongest relationship in Beijing, followed by Seoul, Seosan, and Ulaanbaatar. Since IN generally originates from secondary formation, the strong ON-IN correlation suggests that they may largely share common formation pathways or precursors, or that IN indirectly facilitates ON formation by providing reactive precursors through photochemical processes. Overall, it can be inferred that primary emissions, such as coal combustion, are the main source of ON in Ulaanbaatar, resulting in water-insoluble, lipid-like characteristics. In Seoul, ON likely originates from a combination of primary emissions and secondary formation. In Beijing, secondary formation, particularly IN-associated chemical reactions, appears to be the dominant source. In Seosan, primary emissions, particularly those linked to WSOC, such as biomass burning, are the primary contributors.
Acknowledgement
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).
References
Yu, X., Li, Q., Ge, Y., Li, Y., Liao, K., & Huang, X. H. (2021). Environmental Science & Technology, 55(17), 11579–11589.
How to cite: Kim, J. Y., Yu, X., Yu, J. Z., Kim, Y. P., and Lee, J. Y.: Spatial distribution and Source Apportionment of Organic Nitrogen in PM2.5 over Northeast Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14487, https://doi.org/10.5194/egusphere-egu25-14487, 2025.
Secondary organic aerosol (SOA) plays a significant role in air quality, climate, and human health. SOA produced from the oxidation of biogenic volatile organic compounds (VOCs) in the presence of reactive nitrogen species constitutes a major fraction of ambient organic aerosol. This study investigates the nonlinear effects of mixed biogenic VOC systems, including monoterpenes and sesquiterpenes, on the yield, chemical composition, and volatility of SOA. Smog chamber experiments show that SOA yields for mixtures are reduced compared to single-component systems, likely due to interactions among C10 and C15 RO2 radicals. High-resolution mass spectrometry identifies unique chemical species specific to the mixed-component system, while volatility analysis reveals that sesquiterpene-derived compounds and monoterpene-sesquiterpene cross-reaction products dominate. Model simulations using the Master Chemical Mechanism reveal substantial discrepancies between predicted and experimentally observed SOA yields and volatility. These findings highlight the complexity of SOA formation from VOC mixtures, emphasizing the need to incorporate nonlinear precursor interactions into atmospheric chemistry and air quality models.
How to cite: Ye, J., Li, Y., Qin, Y., Gu, Y., Hu, X., Wang, Y., and Cai, B.: Nonlinear Formation of Secondary Organic Aerosol from Biogenic VOC Mixtures, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15491, https://doi.org/10.5194/egusphere-egu25-15491, 2025.
Aromatic compounds account for a significant proportion of anthropogenic volatile organic compounds emissions, and their atmospheric ageing is a key driver of the formation and growth of organic aerosols. In this study, the benzene oxidation scheme extracted from the Master Chemical Mechanism (MCM) 3.3.1 was revised and improved by the implementation of several new oxidation pathways, including multigeneration oxidation, peroxy radical rearrangement, formation of di-bridged species and autoxidation. These updates lead to the formation of various compounds that can partition into organic and aqueous aerosol phases. Comparisons to chamber experiments of benzene and phenol oxidation show that the addition of these pathways provides a better representation of the formation (aerosol mass yields) and chemical composition of secondary organic aerosols.
While near-explicit schemes provide greater details, their computational complexity makes them difficult to directly implement in chemistry-transport models. To address this, the near-explicit scheme of benzene is reduced using the GENerator of Reduced Organic Aerosol Mechanisms (GENOA) algorithm under representative atmospheric conditions. Using reduction strategies and evaluation criteria, GENOA trains and reduces the SOA mechanism under atmospheric conditions commonly encountered over Europe. The trained benzene SOA mechanism preserves the main characteristic of the near-explicit mechanism (e.g., chemical pathways, molecular structures of crucial compounds, the effect of non-ideality and hydrophilic/hydrophobic partitioning of aerosols), with a size (in terms of reaction and species numbers) that is manageable for three-dimensional aerosol modelling (e.g., regional chemical transport models).
How to cite: Le Bayon, A., Wang, Z., Lannuque, V., Couvidat, F., Ciuraru, R., and Sartelet, K.: Molecular representation of benzene SOA for 3D modelling , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17378, https://doi.org/10.5194/egusphere-egu25-17378, 2025.
Aerosol particles significantly impact Earth’s climate, air quality, and human health. Secondary Organic aerosols (SOA) present a major fraction of the particulate mass in the troposphere. Due to the involved processes ranging from molecular to particle scales, SOA remains a complex topic with a continuing need of method and instrument development.
Proton-transfer-reaction mass spectrometry (PTR-MS) is a well established technique for the characterization of SOA and its precursors. More advanced instruments like the recently introduced FUSION PTR-TOF feature positive selective reagent ions like H3O+ for quantitative measurements of the widest range of organic compounds or NH4+ for soft adduct ionization that enables the detection of highly oxidized compounds. Complemented by NO+ and O2+ ionization mode, this instrument covers the detection of the vast majority of organic and inorganic compounds. However, the measurement of certain inorganic compounds like SO2, H2SO4, other small inorganic acids and organic acids still poses a challenge utilizing only positive reagent ions.
To close this gap, the FUSION PTR-TOF was upgraded with bipolar electronics, enabling operation in negative ion mode using negative reagent ions such as CO3- which provides enhanced selectivity for acids and volatile inorganic compounds, including SO2, HNO3, H2SO4, and halogenated compounds.
In this work we focus on limonene, a monoterpene emitted by plants and widely used in consumer products. It is of particular interest due to its high aerosol yield and structural features like endocyclic and exocyclic double bonds, which influence its oxidation pathways. To study limonene oxidation and its contribution to SOA formation on a molecular level, a laminar flow oxidation reactor was set up. This reactor allows for a controlled oxidation of limonene with oxidants like OH or ozone with residence times of up to 15 min that is sufficient for SOA formation. Limonene and its volatile oxidation products were monitored in real-time with a FUSION PTR-TOF and the particle phase was measured with a CHARON particle inlet for a direct detection of SOA constituents. Based on these measurements we will highlight the benefits and limitations of complementary ionization modes of the new Bipolar FUSION PTR-TOF. CO3- proves to be highly selective to the formed acids and effectively captures products like pinonic acid with virtually no fragmentation significantly simplifying data interpretation. Sequentially ionizing with H3O+, NH4+, NO+, and CO3- primary reagent ion modes allows for capturing the complete picture of the formation process from precursor to SOA.
How to cite: Leiminger, M. S., Klinger, A., Beckmann, H., Graus, M., Reinecke, T., and Müller, M.: Bipolar FUSION PTR-TOF Mass Spectrometer: Advantages of Multiple Reagent Ions to Characterize Oxidation and Secondary Organic Aerosol Formation , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19513, https://doi.org/10.5194/egusphere-egu25-19513, 2025.
