Biogenic volatile organic compounds (BVOCs) are critical precursors of atmospheric secondary pollutants, posing challenges to urban air quality management and public health. Current methodologies for estimating BVOC emissions, largely based on plant functional types (PFTs), lack the spatial and taxonomic precision required for urban landscapes characterized by diverse and heterogeneous vegetation. This limitation introduces significant uncertainties, particularly in highly developed urban areas. To address this gap, this study proposes the development of a high-resolution tree species classification dataset by utilizing remote sensing, machine learning, or in situ data integration techniques. By integrating this dataset with existing emission models, the research aims to quantify the discrepancies between species-level and PFT-based BVOC emission estimates, with a specific focus on urban areas. The species-level data is observed to yield higher emission estimates, highlighting the importance of fine-scale classification for accurately capturing emission dynamics. Additionally, this study analyzes the spatial distribution of BVOCs across urban and peri-urban gradients and assesses the implications of BVOC emissions on the formation of ozone. The findings are expected to provide suggestions for urban vegetation management, supporting the design of evidence-based strategies to mitigate air pollution and enhance urban sustainability.

How to cite: Ma, L. and Ye, J.: Improving BVOC emission estimation with high-resolution tree species mapping in urban areas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16150, https://doi.org/10.5194/egusphere-egu25-16150, 2025.

Accurate representation of biogenic volatile organic compound (BVOC) emissions is critical for understanding their role in atmospheric chemistry and secondary organic aerosol (SOA) formation. In this study, we present an improved framework for modeling biogenic emissions, using the latest version of the Model of Emissions of Gases and Aerosols from Nature (MEGAN). We used domain-specific tree cover data, species distributions (retrieved from the Natural Resources Institute Finland website), and species-specific emission factors, and we recalculated isoprene emission factors tailored to the Finnish boreal region. These modifications were implemented in MEGAN and integrated into the WRF-CHIMERE chemistry transport model, enabling a more accurate simulation of biogenic emissions. We perform simulations over the summer period for the year 2017, 2018, and 2019.

These simulations reveal a significant reduction in bias for both isoprene emissions as well as concentrations when compared to observations at the Hyytiälä and Pallas stations. Additionally, we introduced a detailed canopy correction (sensitivity simulation) to account for the effects of forest canopy on the vertical and horizontal transport of BVOCs. These adjustments additionally reduced the bias in modeled isoprene concentrations when compared to observations. 

The enhanced representation of BVOC emissions and the effects of canopy on dispersion resulted in improvements in the modeled dynamics of SOA formation and transportation, emphasizing the importance of ecosystem-specific modifications in emission models and the inclusion of forest canopy correction in chemical transport models.

Our findings show that the vanilla versions of MEGAN version 3.2 without modification is insufficient to accurately represent isoprene emissions, at least in the European boreal forest ecosystem. High-resolution, domain-specific vegetation data are essential to capture the variability in tree cover, species distribution, and emission factors, ensuring the reliability of modeled biogenic emissions and their impacts on atmospheric chemistry.

How to cite: Bettineschi, M., Ciarelli, G., Cholakian, A., and Bianchi, F.: Improved isoprene emission estimates from MEGAN and comprehensive modeling of BVOCs driven aerosol dynamics in the Boreal forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4126, https://doi.org/10.5194/egusphere-egu25-4126, 2025.

Biogenic volatile organic compounds (BVOCs) play a significant role in the interactions between the biosphere and the atmosphere, but their impact in northern latitudes is difficult to quantify due to a lack of measurements and modeling studies.

We present here the findings from our latest field campaigns in a mountain birch forest near Abisko (Northern Sweden), where we used Proton Transfer Reaction–Time of Flight–Mass Spectrometry (PTR–TOF–MS) and the Eddy Covariance technique to measure the ecosystem-scale fluxes of BVOCs during 3 growing seasons (2021, 2022, and 2023), to understand the diel cycle of these emissions. Furthermore, our study aims to observe and model the impact of herbivore insect defoliation on the gas exchange of the forest, caused by a caterpillar outbreak during our 2023 campaign.

How to cite: Egea Guevara, A., Holst, T., Davie-Martin, C. L., Rieksta, J., Smart, A., Rinnan, R., and Seco, R.: VOC fluxes of a subarctic mountain birch forest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8208, https://doi.org/10.5194/egusphere-egu25-8208, 2025.

The concentration and fate of ozone in the troposphere is dependent on the ratio of volatile organic compounds (VOCs) and NOx gases emitted from both anthropogenic and biogenic sources. The biosphere emits over 1,000 Tg of VOCs annually, over half of which come from vegetation. The ‘fingerprint’ of chemical compounds emitted varies greatly both between and within vegetative species. This fingerprint is greatly influenced by the environmental conditions an individual plant is exposed to.  In a changing climate, rising atmospheric CO₂ concentration is expected to significantly change the quantity and variation of BVOC emissions from vegetation; and thus, the fate of tropospheric O₃ concentrations.

This study uses a coupled deployment of a Total Ozone Reactivity System (TORS) and Proton-Transfer-Reaction Mass-Spectrometer (PTR-MS)

At BIFoR FACE (Birmingham Institute for Forest Research Free Air Carbon Dioxide Enrichment) under both ambient and elevated CO₂ to assess the impact of rising CO₂ on both BVOC emissions and ozone chemistry. Our results show a clear diurnal trend with key ozone reactive BVOCs and ozone reactivity. Interestingly, our study showed a variation in morning and afternoon activity, with isoprene and monoterpene emissions predominantly in the afternoon, with a variation of both BVOC emission and ozone reactivity profile seen in the mornings.

How to cite: Dunn, L., Acton, J., Sommariva, R., Lehman, J., and Bloss, W.: Coupling Measurements of Biogenic Volatile Organic Compounds and Ozone Reactivity in the Field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21187, https://doi.org/10.5194/egusphere-egu25-21187, 2025.

Snow can serve as both a source and a sink for atmospheric volatile organic compounds (VOCs), as well as a surface for their oxidation. However, the influence of snow on the distribution and fate of VOCs at the surface level remains largely unclear. To address this, we conducted a field campaign in a suburban site of Northeast China, from January to March 2024. VOCs were collected using sorbent cartridges at three different heights (i.e., 2.2 m above snow, at snow surface, and 0.1 m below snow surface), over five daily time intervals, including 7:00 to 10:00, 10:00 to 13:00, 13:00 to 16:00, 16:00 to 19:00, and 19:00 to 7:00 the following day. A total of 48 VOCs, out of 89 in the standards, were detected and quantified due to their relatively low concentrations. These included 16 alkanes, 3 alkenes, 14 aromatics, and 15 halogenated hydrocarbons, measured using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Alkanes and aromatics were the most abundant VOC species, exhibiting a diurnal pattern with lower concentrations during the day and higher concentrations at night. The vertical profiles of VOCs indicated that snow could serve as a source for certain species, such as monoterpenes, and as a sink for others, such as aromatics. The corresponding emission rates and deposition velocities were calculated. The findings from this study enhance the understanding of snow-atmosphere interactions and provide critical insights into the role of snow in influencing surface-level VOC distributions and their associated atmospheric processes.

How to cite: Yang, Y., Li, X., Zhao, W., Wang, T., Chen, Q., and Ye, J.: Source and sink of volatile organic compounds over snow surface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15473, https://doi.org/10.5194/egusphere-egu25-15473, 2025.

Atmospheric volatile organic compounds (VOCs) influence air quality and climate by participating in chemical reactions that convert them into low-volatility species. These species can contribute to the formation of new particles or condense onto existing aerosol mass. In the presence of NO_x, VOC reactions also lead to the production of ground-level ozone. Despite their significance, measurements of VOCs in remote regions such as the Arctic remain scarce, leaving critical gaps in our understanding of their sources, sinks, and chemistry in these pristine environments.

To address this, we conducted field measurements of atmospheric VOCs at the Villum Research Station in northern Greenland from 20 July to 15 August 2024 using proton transfer reaction mass spectrometry (PTR-MS). By employing a high-resolution instrument (PTR-ToF MS 8000; Ionicon Analytik GmbH, Innsbruck, Austria), we identified a broader range of atmospheric VOCs compared to earlier studies at the same site that used a lower-resolution instrument.

In this study, we focus on the concentration levels, chemical family compositions, and source characteristics of VOCs using the positive matrix factorization (PMF) model. We further analyze variations in VOC levels based on back-trajectory data, providing insights into the transport and transformation of these compounds in the Arctic atmosphere. Our findings have important implications for understanding VOC-related atmospheric chemistry in remote regions and their role in Arctic air quality and climate processes.

How to cite: Kumar, V., Christoffersen, C., Bossi, R., and Skov, H.: Characterization of Volatile Organic Compounds in the Arctic Atmosphere: Insights from High-Resolution Measurements of VOCs at Villum Research Station, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18770, https://doi.org/10.5194/egusphere-egu25-18770, 2025.

Organic solvents play an important role in industry,  but as the world progresses towards net-zero, their synthesis and end-of-life have become critical areas of research. Most traditional solvents are toxic, petrochemically derived and contribute significantly to chemical waste. Additionally, they have significant impact on air quality because of their role as volatile organic compounds (VOCs), able to fuel atmospheric cycles that generate ozone (O₃) and other harmful gases.¹ While VOC emissions from many sectors are decreasing, emissions from solvents are on the rise.² Notable research efforts focus on developing “green” solvents that are sustainable, renewable, and less toxic but little is known about their air impact.

This research focuses on a promising solvent, ethyl lactate, a bioderived ester from glucose, relevant in various industries. The work addresses the air quality research gap by studying its atmospheric behaviour including its lifetime, photochemical ozone creation potential, and gas-phase breakdown routes.

To achieve these objectives, this work employs methods such as Pulsed Laser Photolysis–Laser Induced Fluorescence for direct OH decay kinetics, UV-vis. spectroscopy for absorption cross-sections and calculating photolysis rate coefficients, and relative rate OH kinetics experiments carried out at an Atmospheric Simulation Chamber (ESC-Q-UAIC facility, CERNESIM centre, Romania).

Relative rate kinetic studies in the atmospheric chamber estimated the k_OH(296K)for ethyl lactate as (2.8 ± 0.5) x 10^-12 cm³ molecule⁻¹ s⁻¹. Using a mean tropospheric [OH]³, the lifetime with respect to OH was estimated to be 4 days. Other preliminary experiments have revealed small UV absorption cross-sections (310 – 350 nm). Further investigations are ongoing to refine and improve on these results and so determine air quality impacts.

Keywords: green, volatile organic compound emissions, air quality impact

The atmospheric chamber results presented in this work is part of a Transnational access project that is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRAIA-2020-1, ATMO-ACCESS Grant Agreement number: 101008004.

References

1            M. E. Jenkin, R. Valorso, B. Aumont, A. R. Rickard and T. J. Wallington, Atmos. Chem. Phys., 2018, 18, 9297–9328.

2            A. C. Lewis, J. R. Hopkins, D. C. Carslaw, J. F. Hamilton, B. S. Nelson, G. Stewart, J. Dernie, N. Passant and T. Murrells, Philos Trans A Math Phys Eng Sci, 2020, 378, 20190328.

3            J. Lelieveld, S. Gromov, A. Pozzer and D. Taraborrelli, Atmospheric Chemistry and Physics, 2016, 16, 12477–12493.

How to cite: Raymond, S. U., D'Souza Metcalf, J., Roman, C., Arsene, C., Olariu, R., Sneddon, H., Bejan, I., and Dillon, T.: Air Quality Impact of a “Green” Solvent – Ethyl Lactate , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6459, https://doi.org/10.5194/egusphere-egu25-6459, 2025.

Solvents have long been recognized as one of the principal sources of waste from the chemical industry, particularly from fine chemical manufacturing.^1,2 While neoteric solvents with minimal atmospheric impact such as supercritical fluids and ionic liquids show promise for some applications, most processes remain dependent on organic solvents. As a result, the last two decades have seen a rapid increase in the development and deployment of bio-derived and biodegradable “green” solvents.³ Design processes for such solvents pay close attention to solvent performance, human and environmental toxicity, and process-scale safety, however the impact of new “green” solvents on the chemistry of the atmosphere remains largely unexplored. As increasingly strict  regulation brings traditional sources of VOC emissions under control solvents have emerged as the largest anthropogenic source of non-methane VOCs.⁴ It is therefore crucial that we expand our understanding of the atmospheric ramifications of this growing and diversifying class of emissions.

This work is a collaboration between green materials chemists and atmospheric scientists. Our interdisciplinary approach to solvent selection and development involves rigorous experimental and in silico testing of both solvent performance and environmental impact as VOCs. Herin we will discuss the atmospheric chemistry of the bio-derived solvent Cyrene (dihydrolevoglucosenone, C₆H₈O₃). Our investigation into this unique, bicyclic multifunctional oxygenate covers its two primary atmospheric breakdown routes. Chamber experiments to determine OH kinetics and aerosol yields, quasi-gas-phase measurement of UV cross sections and fast flow investigations into photolysis quantum yields. Results will be presented in the context of Structure-Activity Relationship (SAR) calculations and other predictive tools, with impacts assessed via estimations of atmospheric lifetime and photochemical ozone creation potential. 

The chamber experiments carried out as part of this work are part of a Transnational access project that is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRAIA-2020-1, ATMO-ACCESS Grant Agreement number: 101008004

(1)          Constable, D. J. C.; Dunn, P. J.; Hayler, J. D.; Humphrey, G. R.; Leazer, Jr., J. L.; Linderman, R. J.; Lorenz, K.; Manley, J.; Pearlman, B. A.; Wells, A.; Zaks, A.; Zhang, T. Y. Key Green Chemistry Research Areas—a Perspective from Pharmaceutical Manufacturers. Green Chem 2007, 9 (5), 411–420. https://doi.org/10.1039/B703488C.

(2)          Bryan, M. C.; Dunn, P. J.; Entwistle, D.; Gallou, F.; Koenig, S. G.; Hayler, J. D.; Hickey, M. R.; Hughes, S.; Kopach, M. E.; Moine, G.; Richardson, P.; Roschangar, F.; Steven, A.; Weiberth, F. J. Key Green Chemistry Research Areas from a Pharmaceutical Manufacturers’ Perspective Revisited. Green Chem. 2018, 20 (22), 5082–5103. https://doi.org/10.1039/C8GC01276H.

(3)          Jordan, A.; Hall, C. G. J.; Thorp, L. R.; Sneddon, H. F. Replacement of Less-Preferred Dipolar Aprotic and Ethereal Solvents in Synthetic Organic Chemistry with More Sustainable Alternatives. Chem. Rev. 2022, 122 (6), 6749–6794. https://doi.org/10.1021/acs.chemrev.1c00672.

(4)          Lewis, A. C.; Hopkins, J. R.; Carslaw, D. C.; Hamilton, J. F.; Nelson, B. S.; Stewart, G.; Dernie, J.; Passant, N.; Murrells, T. An Increasing Role for Solvent Emissions and Implications for Future Measurements of Volatile Organic Compounds. Philos. Trans. R. Soc. Math. Phys. Eng. Sci. 2020, 378 (2183), 20190328. https://doi.org/10.1098/rsta.2019.0328.

How to cite: D'Souza Metcalf, J., Winkless, R., Roman, C., Raymond, S., Arsene, C., Olariu, R., Sherwood, J., Bejan, I., and Dillon, T.: The Air Quality Impacts of the Bio-Based Solvent Cyrene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4097, https://doi.org/10.5194/egusphere-egu25-4097, 2025.

This study aims to evaluate the reliability of volatile organic compound (VOC) detection and identification in complex coastal terrains in Central Chile. In this zone, frequent complaints by residents prompted a new National Ambient Air Quality Standard for benzene in 2023, set at 0.9 ppbv (nmol mol^-1). The monitoring site is located in Concón City, near an oil refinery where we combine a Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR–TOF–MS), a Gas Chromatograph coupled with a Flame Ionization Detector (GC-FID) and meteorological observations.  

We utilized a PTR-TOF-MS (Ionicon Analytik GmbH) to assign monoisotopic masses to specific VOCs. The mass resolution (m/Δm full width at half maximum) was typically ~1000 for benzene (toluene) at m/z 79.054 (93.070). To measure the PTR’s sensitivity, we calibrated the instrument by a multipoint calibration, ranging from 0.5 to 8 ppbv, using a self-made dilution system, ultra-high-purity nitrogen and gas mixture of 8 VOCs (Apel-Riemer Environmental, Inc.). The sensitivity and limit of detection (LoD) for benzene (toluene) determined at a measurement frequency of 1 Hz was 38 cps ppbv^-1 (30 cps ppbv^-1) and 0.20 ppbv (0.30 ppbv).

Our initial PTR measurements in the zone indicated the worst air quality conditions occurred early in the morning due to unfavorable ventilation. Therefore, we will use the parallel measurements of the PTR and the GC (from Jan to Sep 2025) to evaluate the instrument responses during short and intense VOC spikes, considering the rapid meteorological changes such as wind speed and direction and the evolution of the marine boundary layer height (estimated with a ceilometer). In addition, we will use the intercomparison data to assess the fragmentation among other interferences.

How to cite: Seguel, R., Zárate, N., Opazo, C., Castillo, L., Céspedes, F., Quezada, R., Alvarado, G., and Muñoz, R.: Volatile organic compound measurements in an urban coastal environment impacted by oil refinery emissions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13021, https://doi.org/10.5194/egusphere-egu25-13021, 2025.

A twenty-year (2004–2023) trend analysis of marine background air was conducted to explore potential changes in non-methane hydrocarbons (NMHCs) emissions and atmospheric oxidation capacity using the Propylene Equivalent (Propy-Equiv) concentration. The focus was on C₂-C₆ NMHCs including alkanes, aromatics, acetylene, and isoprene, as those were most frequently found in the air samples. During wintertime, least impacted by photochemical impacts, a clear increase in n-pentane was observed from 2004 to 2023 (2.07 ± 2.26 % year^-1) (statistically significant). Ethane (-3.82 ± 8.65 % year^-1) and n-butane (-1.35 ± 15.62 % year^-1) decreased from 2004 to 2008, but this was not statistically significant, but a statistically significant increase was then observed until 2023 (ethane: 1.05 ± 0.51 % year^-1; n-butane: 1.09 ± 1.26 % year^-1). Iso-pentane decreased (-4.25 ± 1.91 % year^-1) steadily from 2004 to 2011 (statistically significant), then remained constant but with increased variability until 2023 (0.28 ± 2.49 % year^-1). Propane increased (5.51 ± 23 1.35 % year^-1) from 2004 to 2014 (statistically significant) and decreased thereafter until 2023 (-3.63 ± 3.91 % year^-1). Acetylene (-1.67 ± 0.51 % year^-1), benzene (-2.43 ± 0.14 % year^-1), and i-butane (-0.58 ± 25 0.25 % year^-1) showed a steady decreasing (statistically significant) trend from 2004 to 2023. The increasing ethane trend for the last 15 years is due to global oil and natural gas extraction, especially in the US, which began in mid-2009. Improvements in gasoline technologies are causing the decline of acetylene and benzene trends. The slower than expected decreasing trend of acetylene mixing ratio might have been offset by the impact of biomass burning emissions. Other NMHCs show varying trends indicating the merge of different emission sources and strengths in separate time periods. During the summertime, 80–90% Propy-Equiv concentration is due to isoprene, with a statistically significant increasing trend (0.45 ppbC/year) between 2004 and 2023. This increase is largely due to rising temperatures (1.58 ± 0.14 ◦C) leading to increased isoprene emissions (20 ± 1.6%).

How to cite: Rappenglück, B., Ahmed, M., and Ahmad, M.: Analysis of twenty years (2004–2023) observation of non-methane hydrocarbons in a subtropical coastal environment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20718, https://doi.org/10.5194/egusphere-egu25-20718, 2025.

Volatile organic compounds (VOCs) released into the atmosphere by natural and anthropogenic sources play a key role in atmospheric processes. They can react with atmospheric oxidants leading to secondary organic aerosols and tropospheric ozone, with effects on air pollution, human health and climate.

The Po Valley, located in the North of Italy is a densely populated area influenced by intense agricultural, industrial and urban-related activities, suffering among the worst air pollution in Europe. Although efforts aimed at characterizing the chemical and physical processes influencing aerosols and other atmospheric pollutants have been conducted over the last decades, very little is known about the precursor organic chemical species emitted in this region.

Volatile organic compounds in the mass range 0-400 amu were measured for three weeks in October 2023 at a rural site in Schivenoglia (MN), in central Po Valley, using a Vocus CI-ToF (chemical ionization time of flight) 2R mass spectrometer (Tofwerk, Switzerland). During the measuring campaign, the site was influenced by contrasting meteorological conditions, warm and colder temperatures as well as biomass burning events and the application of manure to fertilize the fields. Over 1000 peaks, corresponding to volatile molecules and their possible fragments were detected in the measured mass spectra. Among the detected peaks, about 500 were tentatively associated to a chemical identity. The concentrations of the identified species are discussed in function of their variability with time, meteorological conditions, and emission sources, in order to elucidate the atmospheric processes influencing VOC concentrations in the Po valley.

How to cite: Zannoni, N., D'Angelo, L., Cavaliere, A., Paglione, M., David, J., Simon, M., Vogel, A., and Marinoni, A.: Identifying volatile organic compounds at a rural site in the Italian Po Valley, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17927, https://doi.org/10.5194/egusphere-egu25-17927, 2025.

Atmospheric formaldehyde (HCHO) plays a critical role in atmospheric radical budgets and secondary formation of ozone and particulate matter. However, HCHO is known to be significantly underestimated by regional air quality models, which indicates an incomplete understanding of HCHO origins and limits our comprehension of its atmospheric roles and implications. In this study, we revealed that direct emissions of HCHO from wintertime residential coal combustion in north China has been significantly underestimated in current emission inventories, based on field measurements. We observed high values of HCHO (up to 9.4 ppbv) at a typical rural site in Qingdao, north China, which exhibited a diurnal variation pattern with a double-peak distribution in the morning and late afternoon. During the morning peak period, HCHO showed a stronger correlation with SO₂ and NO, while HCHO strongly correlated with CO, NO₂ and biomass burning indicators (levoglucosan, K⁺, Cl^-) during the late afternoon peak period. The diurnal variation of HCHO aligns well with the combustion activities of residents, which are dominated by coal combustion in the morning and biomass burning in the evening, implying the potentially significant contributions of residential combustion emissions to ambient HCHO. We then conducted source apportionment using the Positive Matrix Factorization (PMF) method and confirmed the significant contributions of residential biomass burning and residential coal combustion to observed HCHO. Using the Minimum R Squared (MRS) method, we further calculated the HCHO emission ratios from the two combustion-related sources. We further calculated HCHO emission from residential combustion sectors in widely used emission inventories, such as EDGER, MEIC, MIX and REAS. However, HCHO emissions from residential combustion sectors exhibit large discrepancies among these emission inventories, with the maximum estimate provided by MEIC and the minimum estimate by EDGAR. When we calculated HCHO emissions from residential coal combustion sector and residential biomass burning sector separately, HCHO emissions from residential biomass burning sector were well estimated, while HCHO emissions from residential coal combustion sector were significantly underestimated by an order of magnitude. Using current emission inventory, HCHO was significantly underestimated by CMAQ modeling compared with field measurements. After updating the HCHO emissions from residential coal combustion based on field results, modeled HCHO concentrations significantly increased (over 100%), which further enhanced the atmospheric oxidation capacity and secondary organic formation. Our findings highlight the necessity to revisiting the HCHO emission from residential coal combustion sector in current emission inventory, especially in north China.

How to cite: Zhao, M., Li, L., Shen, H., and Xue, L.: Underestimated Formaldehyde Emission from Residential Coal Combustion in North China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10238, https://doi.org/10.5194/egusphere-egu25-10238, 2025.

Glyoxal (CHOCHO) serves as a critical marker for the oxidation capacities of volatile organic compounds (VOCs) and acts as a precursor to secondary organic aerosols. Nonetheless, the sources and chemical reaction pathways of glyoxal have not been updated, which results in global simulations underestimating the observed concentrations of glyoxal. We have enhanced the representation of glyoxal sources and sinks through laboratory experiments, a comprehensive MCM chemical scheme, and diverse observational data. Within the GEOS-Chem chemical transport model, the revised glyoxal parameterizations reduced the model's underestimation from 80% (72%~85%) to 17% (5%~32%), compared with TROPOMI satellite retrievals. This advancement is attributed to the increased glyoxal yield from isoprene photooxidation (from 5% to 15%) and the incorporation of a glyoxal source over the marine boundary layer (78 Tg/yr). Following the inclusion of the marine source, the global burden of glyoxal augmented by a factor of 1.4, signifying enhanced oxidation over the remote ocean. This investigation elucidates an improved global budget of glyoxal, underscoring the necessity to refine the photochemical processes of biogenic OVOCs and to address the oxidation states of OVOCs in remote oceanic regions.

How to cite: Zhang, A., Fu, T.-M., Wang, Y., Xiong, E., and Li, Y.: Revisiting the global atmospheric glyoxal budget: updates in secondary production pathways and evaluations against satellite observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2587, https://doi.org/10.5194/egusphere-egu25-2587, 2025.

Recent studies show the important role of isoprene in new particle formation (NPF) in the outflow of convective clouds. The oxidation of isoprene combined with low temperatures and low condensation sink yields organic vapours with very low volatility, promoting nucleation (Bardakov et al. 2024, Shen et al. 2024).

This study focuses on the transport of isoprene from low altitudes to the upper troposphere, by convective updrafts. In-cloud isoprene concentration is affected by microphysical mechanisms (uptake by cloud droplets, mixing) and chemical reactions (e.g., OH oxidation). Previous observational and modeling studies have highlighted the survivability of isoprene during transport overnight  due to its high volatility (Bardakov et al. 2024, Murphy et al., 2015). If oxidation can occur inside the convective cloud during the diurnal updraft, further chemical reactions could take place, altering the volatility of the organic vapours present. This would affect the uptake and therefore change the availability of precursors reaching the outflow. NOx, formed during convection due to lightning, could react with isoprene oxidation products to form isoprene nitrates.

We designed a one-month experimental campaign using the smog chamber and the rotating wetted-wall flow reactor (WFR) at PSI. The experimental set up is shown in Figure 1. The isoprene oxidation products are formed in the chamber in the presence of UV lights after the injection of isoprene and HONO (produces OH and NOx) . We varied the oxidation times (OH exposure levels) in the chamber in order to produce first- and second- generation oxidation products (case 1 and 2, respectively). Then, the chamber is used as a reservoir of vapours with the lights off. The vapours are continuously injected into the WFR for 5 hours. In addition, water is injected into the WFR, where due to rotation a microfilm on the inner wall is created. Cases 1 and 2 are carried out either in the absence of light around the WFR (only aqueous uptake), or in the presence of UVB lights, leading to simultaneous aqueous uptake and photochemistry. Another aspect of the experiment is to study the temperature dependence of the aqueous uptake of isoprene oxidation products. The experiment is carried out at 20°C as well as at 5°C in the absence of the light.

Multiple online instruments are deployed in the experiments: two mass spectrometers, Vocus 2R PTR-TOF-MS (proton-transfer-reaction time-of-flight mass spectrometry) and Vocus AIM (Adduct Ionization Mechanism), as well as gas monitors (O3, NO, NO2, NOx) and an SMPS (Scanning mobility particle sizer). 

Figure 1. Schematic of the experimental set-up.

The preliminary analysis shows the dominant presence of MVK/MACR, C4H6O, and isoprene hydroxy nitrates, C5H9NO4 (Figure 2). We will characterize the uptake and chemistry behaviours of the organic vapours under different conditions.

Figure 2. Time series of organic vapours measured with the VOCUS 2R PTR for case 1 at 20°C. Purple shading area indicates chamber measurements.

Grant Agreement number: 101008004.
Grant number: 101073026.

Bardakov, R. et al., (2024) Geophys. Res. Letters, 51
Murphy, B. N. et al., (2015) J. Geophys. Res. Atmos.,120
Shen et al., (2024) Nature, 636

How to cite: Chassaing, A., Riipinen, I., Bardakov, R., Mohr, C., Salteri, F., El Haddad, I., and Huang, W.: Cloud processing of isoprene in the presence of NOx, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19882, https://doi.org/10.5194/egusphere-egu25-19882, 2025.

Biogenic volatile organic compounds (BVOCs) play a crucial role in urban air quality by contributing to ground-level ozone (O₃) and secondary organic aerosol (SOA) formation. While forests help mitigate air pollution, BVOC emissions can interact with anthropogenic pollutants, exacerbating air pollution. These emissions are influenced by seasonality and urbanization, affecting both their rates and chemical compositions [1]. In the Metropolitan Area of São Paulo (MASP), the Atlantic Forest provides a valuable opportunity to study these interactions, but current research is limited [2].

This study assessed BVOC emissions from four native Atlantic Forest species —Alchornea sidifolia (AS), Casearia sylvestris (CS), Guarea macrophylla (GM), and Machaerium nyctitans (MN) —across two forest reserves exposed to different pollution levels. Sampling was conducted at the less polluted Morro Grande Forest Reserve (RMG) and the more urbanized Matão-IAG Forest during the dry (August–September 2023) and rainy (January–February 2024) seasons.

Six replicates per species were analyzed. Branches were cut and placed in water to prevent embolism, and BVOCs were collected using a dynamic enclosure system for 1h. Volatiles were trapped on Tenax cartridges, desorbed using thermal desorption, and analyzed via gas chromatography-mass spectrometry. Ozone formation potential (OFP) and SOA formation potential (SOAP) were calculated using emission rates (ER, µg g⁻¹ h⁻¹), Maximum Incremental Reactivity (MIR), and Fractional Aerosol Coefficients (FACs).

Among the species studied, no isoprene emitters were identified. Sesquiterpenes (SQTs) dominated the emissions. During the dry season at RMG, CS presented the highest OFP (23.44 µg g⁻¹ h⁻¹), driven by elevated SQT emissions. MN ranked second (4.89 µg g⁻¹ h⁻¹) due to high 3-hexen-1-ol emissions, followed by GM (2.91 µg g⁻¹ h⁻¹) and AS (1.96 µg g⁻¹ h⁻¹). At Matão-IAG, CS remained the top contributor but with reduced OFP. AS rose to second place (2.40 µg g⁻¹ h⁻¹), surpassing GM (2.05 µg g⁻¹ h⁻¹). During the rainy season, CS still led (3.26 µg g⁻¹ h⁻¹) at RMG, followed by GM (2.10 µg g⁻¹ h⁻¹), AS (1.65 µg g⁻¹ h⁻¹), and MN (1.50 µg g⁻¹ h⁻¹). Similar trends were observed at Matão-IAG, with CS (2.74 µg g⁻¹ h⁻¹) leading, followed by AS (2.23 µg g⁻¹ h⁻¹), GM (1.99 µg g⁻¹h⁻¹), and MN (0.51 µg g⁻¹ h⁻¹). SOAP trends mirrored OFP. CS consistently had the highest SOAP, particularly at RMG during the dry season (213.30 µg g⁻¹ h⁻¹). GM (19.98 µg g⁻¹ h⁻¹) and AS (17.93 µg g⁻¹ h⁻¹) followed while MN had minimal contributions (1.89 µg g⁻¹ h⁻¹). At Matão-IAG, AS surpassed GM during the rainy season (18.93 vs. 15.63 µg g⁻¹ h⁻¹). Overall, OFP and SOAP exhibited site- and season-dependent variations, declining during the rainy season. CS, as the highest emitter, warrants careful consideration in reforestation planning.

Keywords: BVOCs, São Paulo, Atlantic Forest

Acknowledgements: Funded by Biomasp+ Project - FAPESP (20/07141-2) and, conducted at the Laboratory of Plant-Atmosphere Interaction (LABIAP), Environmental Research Institute of São Paulo.

References
[1] dos Santos et al. 2022. Science of the Total Environment, 824, 153728.
[2] Anselmo-Moreira et al. 2025. Urban Forestry & Urban Greening, 104, 128645.

How to cite: de Souza, S. R., Ruiz Brandão da Costa, B., Anselmo-Moreira, F., do Nascimento, A., Martins Catharino, E. L., Menezes Ferreira Rodrigues, P., Ferreira Martins, T., Staudt, M., Mazzei, K., Furlan, C. M., Rocco, M., Borbon, A., and Fornaro, A.: Ozone and Secondary Organic Aerosol Formation Potential from Native Tree Species in Atlantic Forest Remnants of Southeastern Brazil under Anthropogenic Influence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11696, https://doi.org/10.5194/egusphere-egu25-11696, 2025.

Organic compounds are vital to atmospheric chemistry, with clouds playing a key role in their formation and transformation. Di-carboxylic organic anions, such as oxalate, act as tracers for aqueous-phase chemical processes. This study presents summer measurements of three organic acids (formic, acetic, oxalic), inorganic anions, and cations in cloud water, aerosol, and cloud droplet residual samples obtained 2018-2024 from the summit of Whiteface Mountain (WFM), a forested site in the Adirondack Mountains of northern New York State. Contributions of these acids to dissolved organic carbon (DOC), ion balance, and acidity are assessed in both cloud and aerosol samples. The current study builds on prior studies linking oxalate-to-DOC ratios with ozone concentrations, from which inferences have been made about biogenic volatile organic carbon (BVOC) contributions to secondary organic aerosol (SOA) formation, and we present new insights based on comparisons between cloud water and aerosol phases. We further expand upon the findings of Lawrence et al. (2023), which showed that more than half of the cloud water samples at WFM exhibit excess ammonium (i.e. exceeding sulfate plus nitrate concentrations) in recent years, by evaluating the relationship between excess ammonium and organic acids in both the cloud and aerosol phases.  These findings provide new insights into multi-phase chemistry and SOA formation processes at a remote forested site downwind of many natural and anthropogenic sources, and a site frequently influenced by wildfire smoke.

How to cite: Tripathy, A., Lawrence, C., Lombardo, S., Casson, P., Patel, R., Hammond, L., DeMarle, K., Brandt, R., McKim, S., Schlemmer, J., Schwab, J., Khwaja, H., Hussain, M., Yerger, L., Snyder, P., Kelting, D., May, W., and Lance, S.: Cloud-Aerosol Chemistry Observations at Whiteface Mountain: Organic Acids and the Growing Importance of Ammonium, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7373, https://doi.org/10.5194/egusphere-egu25-7373, 2025.

In recent decades, the proliferation of megacities in developed regions has been paralleled by rapid urbanization across the globe, particularly in developing nations. This trend has led to an increasing number of individuals residing in urban areas, where they face significant air pollution challenges stemming from vehicles and cooking emissions.

It is widely recognized that these sources emit substantial quantities of volatile, semi-volatile, and intermediate-volatility organic compounds (VOCs, SVOCs, and IVOCs), which contribute to considerable secondary organic aerosol (SOA) production. Notable SOA formation has been documented in multiple urban settings, resulting in the generation of carcinogens linked to severe health issues such as lung cancer. Once VOCs are released into the ambient atmosphere, they undergo oxidation, partition between gas and particle phases, and ultimately integrate into primary and secondary organic aerosols (POAs and SOAs), thereby introducing uncertainties into health risk assessments.

Recently, volatile chemical products (VCPs) have emerged as significant unconventional contributors to SOA, particularly as traditional emissions, such as those from vehicle exhausts, are mitigated. A large portion of VCP emissions aligns with urban air quality measurements, both indoors and outdoors. In the U.S., VCPs now represent an increasing share of VOC emissions in urban centers and remain largely unregulated concerning their SOA formation. A comprehensive mass balance indicates that VCPs—including pesticides, coatings, printing inks, adhesives, cleaning products, and personal care items—account for approximately half of fossil fuel VOC emissions in industrialized cities. Furthermore, studies have highlighted that human exposure to carbonaceous aerosols, previously dominated by transportation-related sources, is now shifting towards emissions from VCPs.

In this study, chamber experiments were conducted for various VOC precursors during both daytime and nighttime under different conditions, including a range of NOx levels (low, medium, and high) and the impact of biogenic factors on aerosol yields and composition. Additionally, a low NOx future scenario was explored, assuming reductions in emissions from incomplete combustion alongside a continued rise in global urban population density.

To investigate the oxidation reactions occurring during these experiments, a multi-scheme chemical ionization inlet (MION2, Karsa Inc.) paired with an Orbitrap mass spectrometer (Exploris 240, ThermoFisher) was utilized in the atmospheric simulation chamber. Both nitrate (NO3-) and ethylenediamine (EDA+) reagent ions were employed to ionize the oxidation products, forming corresponding adduct ions.

The oxidation processes yielded a diverse array of highly oxygenated organic molecules (HOM), which are recognized precursors for SOA formation. The various conditions explored in this study enhance our understanding of how gas-phase oxidation influences SOA generation in both polluted and non-polluted urban environments.

How to cite: Farhoudian, S., Asgher, R., Barua, S., Kumar, A., and Rissanen, M.: Urban emissions fate towards secondary aerosol formation; a chamber study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20688, https://doi.org/10.5194/egusphere-egu25-20688, 2025.

Fatty acid ethyl esters (FAEEs) are a class of aroma chemicals that occur naturally in numerous plants and are known for their fruity odour. They are commonly added to food items, cosmetics, scented air fresheners, and cleaners to provide flavour or fragrance, to enhance sweetness perception, or to intensify other aromas. Additionally, they are potentially suitable as solvents and advanced biofuels and could help reduce dependence on fossil fuels.

FAEEs are therefore widely used in both indoor and outdoor environments. If the side chain is short, FAEEs are highly volatile and prone to be present in the ambient air. Especially in indoor environments with poor ventilation, cumulative human exposure can be substantial. In the gas phase, the main loss processes of FAEEs are likely the reactions with OH radicals and photolysis. Rate coefficients and photolysis parameters for these processes determine the atmospheric lifetime of the FAEEs and the degree to which indoor-outdoor-exchange is possible, as well as the production rate of potentially harmful secondary products. However, detailed knowledge of the degradation mechanisms and kinetics is scarce for many FAEEs.

Here, we report experimental data on the OH radical reactions and photolytic properties of ethyl butyrate and several branched derivatives (ethyl 2-methylbutyrate, ethyl isovalerate, isopropyl butyrate). Results are discussed in terms of their potential impact on air quality both indoors and out.

How to cite: Löher, F., Carslaw, N., and Dillon, T. J.: Gas-phase Experiments on the Reactivity and Fate of Short-Chain Fatty Acid Ethyl Ester Derivatives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10519, https://doi.org/10.5194/egusphere-egu25-10519, 2025.