AS3.2 | Atmospheric organics: Sources, chemistry, and fate
Atmospheric organics: Sources, chemistry, and fate
Convener: Colette Heald | Co-conveners: Juliane Fry, Mikael Ehn, Jonathan Williams
Orals
| Mon, 15 Apr, 08:30–12:30 (CEST)
 
Room F2
Posters on site
| Attendance Mon, 15 Apr, 16:15–18:00 (CEST) | Display Mon, 15 Apr, 14:00–18:00
 
Hall X5
Orals |
Mon, 08:30
Posters on site
Mon, 16:15
Organic compounds play a key role in biosphere-atmosphere exchange, anthropogenic emissions, and the reactive chemistry responsible for ozone and particulate matter production. Coming from diverse sources and constituting thousands of individual compounds, with varying oxidation mechanisms, the organic composition of the troposphere is complex. With their wide range of lifetimes and volatilities, these species partition between gas and particle phases and make up a substantial fraction of fine particulate matter. Organics are also a major source of atmospheric reactivity, with implications for the oxidative capacity of the atmosphere. Some individual organic compounds are of interest due to their toxicity or use as specific source tracers. Because of organics’ role in secondary pollutant formation and reactivity, this chemistry is highly relevant to air quality from urban to remote regions. Finally, while global budgets of organic species are central to understanding tropospheric oxidative chemistry and aerosol budgets, they remain poorly constrained.

This session invites contributions about tropospheric organics on local, regional and global scales, from theoretical studies, laboratory experiments, field measurements, modeling studies, satellite studies, and including measurement technique development. The emphasis of this session is on gas-phase organics, including aerosol precursors and semi-volatile species.

Orals: Mon, 15 Apr | Room F2

Chairpersons: Colette Heald, Mikael Ehn
08:30–08:35
5-minute convener introduction
08:35–08:55
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EGU24-5216
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solicited
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On-site presentation
Understudied BVOC emissions in Europe and their potential atmospheric impacts 
Heidi Hellén, Toni Tykkä, Simon Schallhart, Steven Thomas, Wenche Aas, Robert Wegener, Thérèse Salameh, Kaisa Rissanen, Roseline Thakur, Mari Losoi, Lauri Laakso, Jukka Seppälä, Kaisa Kraft, Hannele Hakola, and Arnaud Praplan

Europe is one of the most studied areas related to biogenic volatile organic compound (BVOC) emissions. However, our knowledge of these atmospheric reactive compounds is still quite limited even there. Total hydroxyl radical (OH) reactivity studies indicate that half of the atmospheric reactive compounds are still unknown especially in the forested areas (Yang et al. 2016) and OH and ozone reactivity studies of our group have shown high fractions of reactivity from biogenic emissions (Praplan et al. 2020 and Thomas et al. 2023).

Globally, isoprene is the primary emitted BVOC. While boreal forests in Northern Europe are mainly considered as monoterpene emitters, Central Europe is expected to be dominated by isoprene (e.g. Messina et al. 2016). However, our results from a campaign at 17 stations over Europe in summer 2022 indicated that BVOC mixing ratios are highly variable and some areas also in Central Europe may be dominated by monoterpenes.

Sesquiterpenes and diterpenes have very high potential for secondary organic aerosol formation, but much less is known on their emissions and atmospheric concentrations. Our studies show that birches and spruces may be strong sesquiterpene emitters. We have also found that some urban trees in Montreal and wetlands in Lapland known as isoprene emitters may also release significant amounts of sesquiterpenes. Additionally, forest floor represents a potential source of sesquiterpenes.

Compared to terrestrial sources very little is known on the marine emissions of BVOCs. There are studies on dimethyl sulphide, but our recent results on an island in Baltic Sea suggest that other sulphuric compounds, like methanethiol, may be important too and could have strong impacts on SO2 production and therefore also on new particle and cloud formation. Furthermore, our recent campaign at the coast of Baltic Sea indicates that phytoplankton and macrophytes could be a source of isoprene and monoterpenes (Thakur et al., 2024 publication under prep).

Compounds classified as BVOCs (e.g. monoterpenes) can also be emitted from anthropogenic sources, such as construction sites (e.g. from wooden material), as well as cleaning and personal care products. Our studies in a street canyon in Helsinki in 2022 indicates that they strongly impact local atmospheric chemistry even in wintertime.

 

Messina, P., Lathière, J., Sindelarova, K., Vuichard, N., Granier, C., Ghattas, J., Cozic, A., and Hauglustaine, D. A.: Global biogenic volatile organic compound emissions in the ORCHIDEE and MEGAN models and sensitivity to key parameters, Atmos. Chem. Phys., 16, 14169–14202, https://doi.org/10.5194/acp-16-14169-2016, 2016

Praplan, A. P., Tykkä, T., Schallhart, S., Tarvainen, V., Bäck, J., and Hellén, H.: OH reactivity from the emissions of different tree species: investigating the missing reactivity in a boreal forest, Biogeosciences, 17, 4681–4705, https://doi.org/10.5194/bg-17-4681-2020, 2020.

Thomas, S. J., Tykkä, T., Hellén, H., Bianchi, F., and Praplan, A. P.: Undetected biogenic volatile organic compounds from Norway spruce drive total ozone reactivity measurements, Atmos. Chem. Phys., 23, 14627–14642, https://doi.org/10.5194/acp-23-14627-2023, 2023.

Yang, Y., Shao, M., Wang, X., Nölscher, A. C., Kessel, S., Guenther, A., and Williams, J.: Towards a quantitative understanding of total OH reactivity: A review, Atmos. Environ., 134, 147–161, https://doi.org/10.1016/j.atmosenv.2016.03.010, 2016.

How to cite: Hellén, H., Tykkä, T., Schallhart, S., Thomas, S., Aas, W., Wegener, R., Salameh, T., Rissanen, K., Thakur, R., Losoi, M., Laakso, L., Seppälä, J., Kraft, K., Hakola, H., and Praplan, A.: Understudied BVOC emissions in Europe and their potential atmospheric impacts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5216, https://doi.org/10.5194/egusphere-egu24-5216, 2024.

08:55–09:05
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EGU24-13774
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ECS
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On-site presentation
Changes in chiral monoterpenes during drought in a rainforest reveal distinct source mechanisms 
Joseph Byron, Juergen Kreuzwieser, Gemma Purser, Joost van Haren, S. Nemiah Ladd, Laura Meredith, Christiane Werner, and Jonathan Williams

Monoterpenes (C10H16) are emitted in large quantities by vegetation to the atmosphere (>100 TgC year−1), where they readily react with hydroxyl radicals and ozone to form new particles and, hence, clouds, affecting the Earth’s radiative budget and, thereby, climate change[1-3]. Although most monoterpenes exist in two chiral mirror-image forms termed enantiomers, these (+) and (−) forms are rarely distinguished in measurement or modelling studies[4-6]. Therefore, the individual formation pathways of monoterpene enantiomers in plants and their ecological functions are poorly understood. Here we present enantiomerically separated atmospheric monoterpene and isoprene data from an enclosed tropical rainforest ecosystem in the absence of ultraviolet light and atmospheric oxidation chemistry, during a four-month controlled drought and rewetting experiment, the Biosphere 2 Water, Air and Life Dynamics campaign (B2WALD) in 2019[7, 8]. The measurements were obtained with an on-line gas chromatograph-mass spectrometer over five time periods: pre-drought, early drought, severe drought, deep rewet and rain rewet.

Surprisingly, the emitted enantiomers showed distinct diel emission peaks, which responded differently to progressive drying. Isotopic labelling established that vegetation emitted mainly de novo-synthesized (−)-α-pinene, whereas (+)-α-pinene was emitted from storage pools. As drought progressed, the source of (−)-α-pinene emissions shifted to storage pools which would favour cloud formation since the peak concentration became more aligned with temperature. Pre-drought mixing ratios of both α-pinene enantiomers correlated better with other monoterpenes than with each other, indicating different enzymatic controls. These results show that enantiomeric distribution is key to understanding the underlying processes driving monoterpene emissions from forest ecosystems and predicting atmospheric feedbacks in response to climate change.

1. Jokinen, T., et al., Production of extremely low volatile organic compounds from biogenic emissions: Measured yields and atmospheric implications. Proceedings of the National Academy of Sciences, 2015. 112(23): p. 7123-7128.

2. Engelhart, G.J., et al., CCN activity and droplet growth kinetics of fresh and aged monoterpene secondary organic aerosol. Atmos. Chem. Phys., 2008. 8(14): p. 3937-3949.

3. Laothawornkitkul, J., et al., Biogenic volatile organic compounds in the Earth system. New Phytologist, 2009. 183(1): p. 27-51.

4. Yáñez-Serrano, A.M., et al., Monoterpene chemical speciation in a tropical rainforest:variation with season, height, and time of dayat the Amazon Tall Tower Observatory (ATTO). Atmos. Chem. Phys., 2018. 18(5): p. 3403-3418.

5. Jardine, K.J., et al., Monoterpene 'thermometer' of tropical forest-atmosphere response to climate warming. Plant Cell Environ, 2017. 40(3): p. 441-452.

6. Guenther, A., et al., The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2. 1): an extended and updated framework for modeling biogenic emissions. 2012.

7. Byron, J., et al., Chiral monoterpenes reveal forest emission mechanisms and drought responses. Nature, 2022. 609(7926): p. 307-312.

8. Werner, C., et al., Ecosystem fluxes during drought and recovery in an experimental forest. Science, 2021. 374(6574): p. 1514-1518.

 

How to cite: Byron, J., Kreuzwieser, J., Purser, G., van Haren, J., Ladd, S. N., Meredith, L., Werner, C., and Williams, J.: Changes in chiral monoterpenes during drought in a rainforest reveal distinct source mechanisms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13774, https://doi.org/10.5194/egusphere-egu24-13774, 2024.

09:05–09:15
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EGU24-3572
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ECS
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On-site presentation
Impact of deep convection on biogenic volatile organic compounds in the upper troposphere over the Amazon Rainforest 
Nidhi Tripathi, Achim Edtbauer, Nijing Wang, Akima Ringsdorf, Bianca Krumm, Thomas Klüpfel, Jos Lelieveld, and Jonathan Williams

Biogenic volatile organic compounds (BVOCs) play an essential role in tropospheric chemistry, forming secondary organic aerosol and influencing ambient ozone. Since particles produced from BVOCs may grow to form cloud condensation nuclei (CCN) and influence cloud properties, BVOCs also indirectly affect the global radiation budget. The terrestrial biosphere is a significant source of BVOCs, with the emissions from the tropical forests (mainly the Amazon) contributing about 80% to the global BVOC budgets. Our understanding of BVOC emissions and chemistry, particularly their role in particle formation over the Amazon rainforest, is incomplete. Therefore, a comprehensive suite of atmospheric instruments was used to measure BVOCs, particles and other trace gases over the Amazon rainforest using the High Altitude and Long-range Observation (HALO) aircraft from Dec 2022 to Jan 2023. The main focus of the field campaign was to investigate how tropical convection affects the atmospheric chemistry of BVOCs using measurements made from 300m to 15km altitude. The measurements of BVOCs were performed using PTR-ToF-MS and fast GC-MS.

 Isoprene was found to be the dominant BVOCs in the Amazon boundary layer. Interestingly, as a result of the regional strong convection, we observed elevated mixing ratios of isoprene (>1ppb), its oxidation products, and the sum of monoterpenes (MTs) in the upper troposphere (~10-12 km). This shows that despite the fast reaction rate of isoprene with OH (lifetime 1 hour) significant amounts can reach the outflow regions of the upper troposphere. The diel (24-hour) profile of isoprene mixing ratios, its oxidation products, and MTs in the upper troposphere were observed to change markedly with altitude. Near the surface (300m) BVOC emissions including isoprene varied with light and temperature peaking at circa 13:00 local time. However, between 10-12km, isoprene mixing ratios rose during the night and peaked before dawn and the onset of photochemical oxidation. This suggests that the nocturnal convection of residual isoprene is an effective vertical transport mechanism that primes the upper troposphere for particle production the following day. The boundary layer isoprene mixing ratios were also found to vary spatially with the strongest gradient found between the forested and deforested regions. The mean mixing ratios of isoprene (2.96 ±0.72 ppbv) and MTs (0.31±0.09 ppbv) in the forested regions were ~4 times higher than their values measured in the deforested regions. In both the boundary layer and outflow regions of the tropical Amazonian troposphere isoprene is a key player in the atmospheric chemistry. Preliminary results of the spatio-temporal variation and vertical profiles of other selected BVOCs will be presented.

How to cite: Tripathi, N., Edtbauer, A., Wang, N., Ringsdorf, A., Krumm, B., Klüpfel, T., Lelieveld, J., and Williams, J.: Impact of deep convection on biogenic volatile organic compounds in the upper troposphere over the Amazon Rainforest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3572, https://doi.org/10.5194/egusphere-egu24-3572, 2024.

09:15–09:25
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EGU24-1318
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ECS
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On-site presentation
Airborne flux measurements for validation of VOC emission inventories and source attribution 
Eva Y. Pfannerstill, Caleb Arata, Qindan Zhu, Benjamin C. Schulze, Roy Woods, Colin Harkins, Rebecca H. Schwantes, Brian C. McDonald, John H. Seinfeld, Anthony Bucholtz, Ronald C. Cohen, and Allen H. Goldstein

For accurate prediction and modelling of air quality and climate, it is necessary to understand the emissions of volatile organic compounds (VOCs) from the potpourri of sources that they are emitted from: traffic, industry, households, plants, agriculture, etc. In the past, efforts to understand the magnitude and composition of VOC emissions have often relied on indirect methods – either using bottom-up emission models, or inferring emissions top-down from concentration measurements via chemical transport models. Both approaches rely on a number of assumptions regarding chemical reactions and transport - and thus are subject to large uncertainties.

Airborne flux observations provide direct emission and deposition information at landscape scale with a resolution of a few km. We performed airborne eddy covariance measurements of a large range of VOCs on board a Twin Otter aircraft in Los Angeles and the agricultural San Joaquin Valley in California using PTR-ToF-MS. Combining these observations with a footprint model, we matched them with gridded inventories in space and time. The comparison with the inventories showed a good representation of typical traffic VOCs, but a significant underestimation of oxygenated VOCs (likely from volatile chemical products and cooking) and terpenoids by the inventories.

Using airborne flux footprints in combination with landcover information of the San Joaquin Valley, we disaggregated the observed VOC emissions by multivariate linear regression and attributed them to their sources. This way, we obtained typical VOC emission rates and composition for dairy farms, citrus crops, citrus processing facilities, oak forests, oil and gas wells, and urban areas.

How to cite: Pfannerstill, E. Y., Arata, C., Zhu, Q., Schulze, B. C., Woods, R., Harkins, C., Schwantes, R. H., McDonald, B. C., Seinfeld, J. H., Bucholtz, A., Cohen, R. C., and Goldstein, A. H.: Airborne flux measurements for validation of VOC emission inventories and source attribution , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1318, https://doi.org/10.5194/egusphere-egu24-1318, 2024.

09:25–09:35
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EGU24-11361
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On-site presentation
Humidity-dependent dry deposition of methacrolein to plant species 
Sergiy Medinets, Ben Langford, Chiara Di Marco, Massimo Vieno, and Eiko Nemitz

Volatile organic compounds (VOCs) together with nitrogen oxides contribute to the formation of ground-level ozone as well as PM2.5 pollution through secondary organic aerosol formation, with adverse effects on human health and environment. Researchers have mainly focused on quantifying VOC emissions from plant canopies and their controls, leading to improvements in atmospheric chemistry models (Jimenez et al., 2009). However, much less attention has been spent on quantifying dry deposition of primary and secondary VOCs to surfaces, with most models often using deposition rates extrapolated from SO2 (as a proxy of a water-soluble gas of limited reactivity) and O3 (as a proxy of an insoluble reactive gas), making uncertain assumptions on the relative behaviour of key VOCs (Wesely, 2007). To address this, we conducted the first systematic, measurement-based investigation into VOC dry deposition as part of the ‘Dry Deposition Processes of VOCs’ project funded by Natural Environment Research Council. The overarching aim of the study was to reduce uncertainty in atmospheric chemistry models by developing parameterisations for the dry deposition of VOCs. The preliminary results of our laboratory study on plant fumigation with methacrolein (MACR), among other selected VOCs, are presented here.

An automated dynamic gas-exchange chamber system was developed to expose test plants to specific VOCs at various concentrations under controlled conditions. Overall, six plant species (see below) were tested with each experiment lasting four days: one day to observe background emissions and three days with VOC fumigation at 20, 15 and 10 °C. Three levels of relative humidity (RH) were applied during day and night times, being fumigated with five concentrations of VOCs within each RH level. In total, eleven VOCs were selected for fumigation: water-insoluble (isoprene, benzene, toluene, xylene, a-pinene) and water-soluble (methanol, acetonitrile, acetaldehyde, acetone, acetic acid and MACR). VOCs were measured using a proton transfer reaction instrument equipped with time-of-flight mass spectrometer (PTR-Qi-TOF). Fluxes were calculated based on concentration difference between blank and measurement chambers and then normalized by the corresponding plant leaf area indices.

MACR appears to be ‘valuable’ VOC to study dry deposition as it is not typically emitted by plants but is an important first-order product of isoprene oxidation in the atmosphere. Nevertheless, minor MACR emissions have been reported, suggesting that oxidation may also take place within leaves (Fares et al., 2015).   

The deposition velocity of MACR was found to increase with RH, and larger deposition velocities were consistently observed during the daytime compared to the night. This diurnal dependence indicates either stomatal control or photochemical processes, or a combination of the two, were present under daylight conditions. However, this varied substantially across tested plants being ranked in the following order Pinus sylvestris > Hedera sp. > Picea glauca > Betula sp. > Tsuga heterophylla > Ilex aquifolium. At all times, MACR compensation points were found to be negligible (near zero) or even negative, suggesting minor or no impact on deposition rates.

These findings are enhancing our understanding of VOC deposition and will inform the development of new parameterizations for atmospheric chemistry models.

How to cite: Medinets, S., Langford, B., Di Marco, C., Vieno, M., and Nemitz, E.: Humidity-dependent dry deposition of methacrolein to plant species, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11361, https://doi.org/10.5194/egusphere-egu24-11361, 2024.

09:35–09:45
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EGU24-3892
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On-site presentation
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Atmospheric isoprene measurements reveal larger-than-expected Southern Ocean emissions 
Neil R.P. Harris, Valerio Ferracci, James Weber, Conor Bolas, Andrew Robinson, Fiona Tummon, Pablo Rodríguez-Ros, Pau Cortés-Greus, Andrea Baccarini, Roderick L Jones, Martí Galí, Rafel Simó, and Julia Schmale

Isoprene is a key trace component of the atmosphere emitted by vegetation and other organisms. It is highly reactive and can impact atmospheric composition and climate by affecting the greenhouse gases ozone and methane and secondary organic aerosol formation. Marine fluxes are poorly constrained due to the paucity of long-term measurements; this in turn limits our understanding of isoprene cycling in the ocean. Here we present the analysis of isoprene concentrations in the atmosphere measured across the Southern Ocean over 4 months in the summertime. Some of the highest concentrations (> 500 ppt) originated from the marginal ice zone (MIZ) in the Ross and Amundsen seas, indicating the MIZ is a significant source of isoprene at high latitudes. Using the global chemistry-climate model UKESM1 we show that current estimates of sea-to-air isoprene fluxes underestimate observed isoprene by a factor >20. A daytime source of isoprene is required to reconcile models with observations. The model presented here suggests such an increase in isoprene emissions would lead to >8% decrease in the hydroxyl radical in regions of the Southern Ocean, with implications for our understanding of atmospheric oxidation and composition in remote environments, often used as proxies for the pre-industrial atmosphere.

How to cite: Harris, N. R. P., Ferracci, V., Weber, J., Bolas, C., Robinson, A., Tummon, F., Rodríguez-Ros, P., Cortés-Greus, P., Baccarini, A., Jones, R. L., Galí, M., Simó, R., and Schmale, J.: Atmospheric isoprene measurements reveal larger-than-expected Southern Ocean emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3892, https://doi.org/10.5194/egusphere-egu24-3892, 2024.

09:45–09:55
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EGU24-11383
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On-site presentation
Biogenic sulfur compounds and their oxidation products in the spring-to-summer Arctic marine atmosphere 
Megan Willis, Cort Zang, Julia Asplund, Fredrik Mattsson, Paul Zieger, and Michael Tjernström

Gas-phase biogenic organosulfur compounds, and their oxidation products are important for the formation and growth of aerosol in the marine environment. During the spring-summer increase in marine biological activity in the northern hemisphere, dimethyl sulfide ((CH3)2S, DMS) and methanethiol (CH3SH, MeSH) are emitted from ocean and sea-ice environments. The emission or transport, and following oxidation, of organosulfur compounds to the Arctic marine environment impacts the available aerosol number and cloud condensation nuclei. Here, we examine organosulfur compound composition, atmospheric fate, and relationships to the aerosol population at the onset of sea-ice melt.

We present shipborne gas-phase measurements of reduced and oxidized organosulfur compounds made with a H­3O+/NH4+ reagent ion switching chemical ionization time-of-flight mass spectrometer as part of the Atmospheric Rivers and the onseT of sea ice MELT (ARTofMELT) campaign on IB Oden. Our measurements during ARTofMELT spanned from May 7th to June 15th of 2023 and took place over pack ice and the marginal ice zone between 78 and 81°N between the east coast of Greenland and the Svalbard archipelago (the Fram Strait). Non-DMS organosulfur species made a significant contribution to atmospheric sulfur during the campaign. MeSH was present at concentrations ~10% of DMS (10’s of pptv) during periods of elevated organosulfur compounds (DMS exceeding ~100 pptv) and was correlated with DMS (R2 > 0.8). Ambient temperatures ranged between -15 and 2°C, making the primary oxidation reaction between DMS and the hydroxyl radical the OH-addition pathway to produce dimethyl sulfoxide (DMSO). We observed DMSO in concentrations occasionally exceeding 150 pptv, and the chemical formula C2H6SO2 (likely dimethyl sulfone) at similar concentrations to DMSO. During low ozone periods (< 10 ppbv), the loss of DMS was potentially influenced by halogen chemistry resulting in an increased abundance of DMSO relative to DMS. We use our measurements to investigate organosulfur compound composition and loss pathways under a variety of atmospheric conditions.

How to cite: Willis, M., Zang, C., Asplund, J., Mattsson, F., Zieger, P., and Tjernström, M.: Biogenic sulfur compounds and their oxidation products in the spring-to-summer Arctic marine atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11383, https://doi.org/10.5194/egusphere-egu24-11383, 2024.

09:55–10:05
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EGU24-3112
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ECS
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On-site presentation
Atmospheric Gas Phase Formation Mechanism of Methanesulfonic Acid 
Jing Chen, Joseph R. Lane, Kelvin H. Bates, and Henrik G. Kjaergaard

The oxidation of dimethyl sulfide (DMS) leads to the formation of sulfuric acid (SA) and methane sulfonic acid (MSA), which has a great impact on atmospheric aerosol and cloud formation (Barnes, Hjorth et al. 2006). Despite the great importance, the formation mechanism of MSA from DMS has remained unclear for decades (Shen, Scholz et al. 2022).

           The reaction of DMS with OH radical forms methanesulfinic acid (MSIA), methane sulfenic acid (MSEA), methylation radical (CH3S) radical, and hydroperoxymethyl thioformate (HPMTF)(Berndt, Scholz et al. 2019, Shen, Scholz et al. 2022). Among them, the oxidation of the first three all undergoes either the CH3SO radical or the CH3SO2 radical as intermediates(Kukui, Borissenko et al. 2003, Berndt, Chen et al. 2020, Chen, Berndt et al. 2021).

           We theoretically investigated the atmospheric fate of the CH3SO and CH3SO2 radicals. The results suggest that CH3SO radical mainly reacts bimolecularly forming CH3SO2, and the CH3SO2 radical either decomposes forming SO2 or adds O2 forming the peroxy radical CH3S(O)2OO in the atmosphere. We show that the branching ratio of SO2 and CH3S(O)2OO formation from CH3SO2 is temperature sensitive, and the ratio of SO2 to CH3S(O)2OO decreases from about 99:1 to about 95:5 when reducing the temperature from 300 K to 260K. The peroxy radical CH3S(O)2OO can react bimolecularly forming the CH3SO3 intermediate, which can abstract an H from HO2 forming MSA. In addition, we show that MSA can also form directly via the reaction of MSIA and OH followed by O2 addition (Chen, Lane et al. 2023).

           Our study indicates that temperature may play a crucial role in explaining atmosphere MSA formation. SO2 is likely the dominant product from DMS + OH in the tropics and warm regions, while in the colder and polar regions, large amounts of MSA can be formed in the gas phase by DMS reacting with OH. Global modeling indicates that the proposed temperature-sensitive MSA formation mechanism leads to a substantial increase in the simulated global atmospheric MSA formation and burden (Chen, Lane et al. 2023).

How to cite: Chen, J., Lane, J. R., Bates, K. H., and Kjaergaard, H. G.: Atmospheric Gas Phase Formation Mechanism of Methanesulfonic Acid, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3112, https://doi.org/10.5194/egusphere-egu24-3112, 2024.

10:05–10:15
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EGU24-9501
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ECS
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On-site presentation
Volatile Organic Compounds shipping emissions observed in an industrial harbour of northern France  
Erwan Volent, Liselotte Tinel, Joel F. de Brito, Marina Jamar, and Stéphane Sauvage

Among the regulated sources of pollutants, shipping has a significant contribution to NOx and SO2 global emissions 1–3. The international maritime transport regulation was updated in 2020 lowering the sulphur content in marine fuel globally from 3.5% to a maximum of 0.5% (m/m). Specific Sulphur Emission Control Areas have been established where the emissions of sulphur are further restricted, such as the Channel, between France and the U.K. However, other pollutants such as Volatile Organic Compounds (VOC) or Particulate Matter (PM), are not regulated in terms of shipping emissions. VOCs are of particular importance in the atmospheric chemistry processes, especially because of their role in the formation of ozone and as precursors of secondary PM in the vicinity of densely populated coastal areas 4. This raises the question of which VOC are emitted by ships under these new emission standards, what their emission rates are and what their impact on air quality is? Only a few studies considered the speciation of VOC emitted by ships 5, yet those data are crucial for reliable gas-phase atmospheric chemistry modelling and correct impact assessment. Our study presents the analysis of a VOC dataset collected during an intensive one-month field campaign in the harbour of Dunkirk in northern France, the third largest French port. The observations were conducted on a site near ferry and cargo terminals and provided high temporal resolution measurements of VOCs, using a PTR-ToF-MS, alongside many other parameters (meteorology, particles, gases). Data analysis allowed the identification of more than 65 plumes from different ferries, based on a methodology that relies on favourable meteorological conditions, port office entries and tracers like SO2. Firstly, Emission Factors (EFs) have been calculated, providing an estimate of the relative amount of a pollutant emitted relative to CO2. For species like SO2 or CH4, our results were consistent with the EMEP emission inventory of 2021 (De Lauretis et al. 2021), however, some VOCs displayed large differences compared to ship exhaust determined EF within the EU/SCIPPER project 7. As an example, the median EF of benzene ions (C6H6.H+) was 27.87 mg/kg(fuel) versus 5.31 mg/kg(fuel) for SCIPPER, whereas toluene (C7H8.H+) was 23.37 mg/kg(fuel) versus 0.49 mg/kg(fuel) for exhaust measurement. Secondly, Positive Matrix Factorization has been applied to the dataset to investigate a shipping chemical profile of VOC that will allow us to calculate the contribution of shipping emission to the total VOC concentration in such harbour area.

1. Corbett, J. J. et al. Environ. Sci. Technol. 41, 8512–8518 (2007).

2. Faber, J., Hanayama, S., Zhang, S. & Pereda, P. Fourth IMO GHG Study 2020 Executive-Summary. (2020).

3. Merk, O. Shipping Emissions in Ports. vol. 2014/2 (2014).

4. Fang, H. et al. Journal of Geophysical Research: Atmospheres 127, e2022JD037301 (2022).

5. Xiao, Q. et al. Atmos. Chem. Phys. 18, 9527–9545 (2018).

6. De Lauretis, R., Ntziachristos, L. & Trozzi, C. Air pollutant emission inventory guidebook 2019, update 2021. (2021).

7. Timonen, H. et al. Ship on-board emissions characterisation. (2022).

How to cite: Volent, E., Tinel, L., F. de Brito, J., Jamar, M., and Sauvage, S.: Volatile Organic Compounds shipping emissions observed in an industrial harbour of northern France , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9501, https://doi.org/10.5194/egusphere-egu24-9501, 2024.

Coffee break
Chairpersons: Juliane Fry, Jonathan Williams
10:45–11:05
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EGU24-2952
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solicited
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On-site presentation
Biogenic VOC Multiphase Chemistry – From Cloud Scavenging to New Particle Formation   
Joel Thornton

Development of a molecular-level understanding of the processes governing the evolution of organic aerosol mass has been a long running challenge. I will present new insights into the potential for biogenic volatile organic compounds (BVOC) to form new particles and contribute to organic aerosol formation. Specifically, I will illustrate the coupled roles of organic peroxy radical chemistry and shallow and deep convective clouds in transporting or processing BVOC and their oxidations products that impact aerosol particle formation and growth on scales that are typically unresolved in global scale chemical transport models. The fate of organic peroxy radicals from BVOC depends upon NOx, with natural and anthropogenic sources, as well as temperature and therefore changes substantially with both altitude and region. Deep convection efficiently transports BVOC to the upper troposphere with significant decreases in temperature and, over land substantial NOx from lightning and from co-transport of polluted boundary layer air. The fates of BVOC-derived organic peroxy radicals in the upper troposphere will therefore occur in conditions rarely probed experimentally, with implications for the formation of low volatility products. In addition, during transport through shallow or deep convective clouds, soluble BVOC oxidation products commonly considered important precursors to secondary organic aerosol (SOA) will partition and potentially react in the cloud water. Thus, the common occurrence of both shallow cumulus and deep convective clouds is a large but poorly represented lever on biogenic SOA formation. 

I will show results from studies of the above processes using a hierarchy of models, including parcel models run along trajectories from Large Eddy Simulation (LES) models of deep convective clouds, LES models of cumulus-topped boundary layers with online multi-phase chemistry, and global chemical transport simulations with online chemistry and implications for new particle formation and organic aerosol mass budgets. Chemical mechanisms are informed by recent laboratory studies of organic peroxy radicals, such as autoxidation, accretion product formation from cross-reactions, and organic nitrate formation, as well as the aqueous chemistry of isoprene-derived epoxy diols. Comparisons of these models to observations reveal the importance of scattered cumulus clouds to the fate of isoprene epoxy diols and thus its SOA formation potential, the role of lightning and soil NOx in new particle formation from BVOC oxidation in the upper-tropospheric outflow of deep convective clouds, and the potential for isoprene oxidation at high NO and low temperature to serve as a key source of low volatility organics that drive new particle formation in deep convective outflow.

How to cite: Thornton, J.: Biogenic VOC Multiphase Chemistry – From Cloud Scavenging to New Particle Formation  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2952, https://doi.org/10.5194/egusphere-egu24-2952, 2024.

11:05–11:15
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EGU24-20198
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On-site presentation
Significance of hydrogen abstraction in the formation of highly oxygenated organic molecules in the OH oxidation of monoterpenes 
Defeng Zhao, Hongru Shen, Hao Luo, Vereecken Luc, Sungah Kang, Pullinen Iida, Hendrik Fuchs, Mattias Hallquist, Andreas Wahner, Astrid Kiendler-Scharr, and Thomas Mentel

Secondary organic aerosol (SOA), formed by oxidation of volatile organic compounds, significantly influence air quality and climate. Biogenic highly oxygenated organic molecules (HOM), particularly those formed from monoterpenes, play a key role in SOA formation and growth. As the most important daytime oxidant, hydroxyl radical (OH•) initiated HOM from monoterpenes is believed to be mainly formed via OH addition channel. However, for α-pinene and limonene, we found that the contribution of hydrogen abstraction channel by OH contribute a significantly to HOM formation. We will present our observations and theoretical calculations, showing the role of hydrogen-abstraction and alkoxy radicals for fast autoxidation leading to HOM formation. We also provide formation mechanisms of and yields of HOM, suggesting the non-negligible contribution of the hydrogen abstraction channel to ambient SOA, particularly in OH-rich areas.

How to cite: Zhao, D., Shen, H., Luo, H., Luc, V., Kang, S., Iida, P., Fuchs, H., Hallquist, M., Wahner, A., Kiendler-Scharr, A., and Mentel, T.: Significance of hydrogen abstraction in the formation of highly oxygenated organic molecules in the OH oxidation of monoterpenes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20198, https://doi.org/10.5194/egusphere-egu24-20198, 2024.

11:15–11:25
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EGU24-7707
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ECS
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On-site presentation
Formation and temperature dependence of Highly Oxygenated Organic Molecules from ∆3-carene ozonolysis 
Yuanyuan Luo, Ditte Thomsen, Emil Mark Iversen, Pontus Roldin, Jane Tygesen Skønager, Linjie Li, Michael Priestley, Henrik B. Pedersen, Mattias Hallquist, Merete Bilde, Marianne Glasius, and Mikael Ehn

Monoterpenes, comprising 15% of global biogenic volatile organic compound emissions, play a pivotal role in atmospheric chemistry. ∆3-carene, the second most prevalent monoterpene, has been identified as a significant source of secondary organic aerosol (SOA) upon oxidation, potentially surpassing α-pinene under similar conditions. Despite its importance, research has predominantly focused on α-pinene , leaving gaps in our understanding of ∆3-carene's oxidation pathways, particularly its capacity to form highly oxygenated organic molecules (HOM).

To address this knowledge gap, we conducted an investigation into HOM formation during the ozonolysis of ∆3-carene using atmospheric simulation chambers. Employing a chemical ionization atmospheric pressure interface time-of-flight mass spectrometer with nitrate as the reagent ion (NO3-CIMS), we measured HOM resulting from ∆3-carene ozonolysis. Additionally, we explored the impact of temperature and relative humidity on HOM composition and distribution across various conditions (0, 10, and 20 ºC, and humidity levels below 15% and around 80%).

Our analysis revealed diverse HOM monomers and dimers from ∆3-carene ozonolysis. Predominant HOM monomers included C10H14,16O9 and C9H12,14O9, while the largest dimers comprised C19H30O6,10,11 and C20H32O7,9,11. Significantly, HOM monomers with 9 or more oxygen atoms and all dimers irreversibly condensed onto particles, while those with 6-8 oxygen atoms behaved as semi-volatile organic species, maintaining notable gas-phase concentrations. Intriguingly, ∆3-carene ozonolysis produced higher HOM concentrations than α-pinene, suggesting distinct formation pathways for these two monoterpenes. Furthermore, we observed a substantial decrease in HOM concentrations at lower temperatures, consistent with previous studies on α-pinene ozonolysis. Despite similar main HOM species at temperatures of 20, 10, and 0 ℃, the ratio of HOM dimers to monomers increased from 0.78 to 1.51 as temperatures decreased. This temperature-dependent variation underscores the complexity of ∆3-carene's atmospheric processing, revealing nuanced behaviors of HOM under different environmental conditions.

In conclusion, this study provides valuable insights into the HOM formation pathways of ∆3-carene, shedding light on its unique atmospheric chemistry. The observed differences in HOM concentrations and temperature-dependent behaviors highlight the need for a more comprehensive understanding of various monoterpenes, moving beyond the well-studied α-pinene. These findings contribute to the broader knowledge of biogenic volatile organic compounds and their impact on atmospheric processes.

How to cite: Luo, Y., Thomsen, D., Iversen, E. M., Roldin, P., Skønager, J. T., Li, L., Priestley, M., Pedersen, H. B., Hallquist, M., Bilde, M., Glasius, M., and Ehn, M.: Formation and temperature dependence of Highly Oxygenated Organic Molecules from ∆3-carene ozonolysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7707, https://doi.org/10.5194/egusphere-egu24-7707, 2024.

11:25–11:35
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EGU24-9952
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On-site presentation
Towards understanding aromatic SOA by studying the molecular level oxidations mechanisms of xylene isomers 
Siddharth Iyer, Avinash Kumar, Shawon Barua, Jian Zhao, Anni Savolainen, Prasenjit Seal, Lukas Pichelstorfer, Pontus Roldin, Mikael Ehn, and Matti Rissanen

Aromatic compounds like xylene contribute significantly to the formation of tropospheric secondary organic aerosol (SOA) that have strong implications on health and on climate. The sources of this class of molecules are primarily anthropogenic, but biogenic sources of aromatics can be significant too. To form SOA, the volatile xylene needs to oxidize into low volatility aerosol precursors with multiple oxygen containing polar functional groups called highly oxygenated organic molecules (HOMs). It does this through the autoxidation mechanism, which is a sequential process involving peroxy radicals where each intra-molecular reaction step such as an H-atom shift is followed quickly by O2 addition. While laboratory measurements using the sensitive chemical ionization mass spectrometer (CIMS) instrument indicate rapid conversion of xylene to HOM, this is unsupported by established oxidation mechanisms. This is due to the assumed stability of the crucial bicyclic peroxy radical (BPR), an intermediate that is intrinsic to aromatic oxidation in general. Recently, we showed that the BPR associated with toluene oxidation can be unstable, and its decomposition is pivotal to the subsequent autoxidation mechanism that leads to HOM. [1]

 

Through investigating the autoxidation mechanisms of xylene in this work, we establish the importance of aromatic derived BPR decomposition to the formation of SOA. We combine theoretical modelling with sub-second HOM measurements using CIMS to develop the Aerosol Dynamics gas- and particle-phase chemistry model for laboratory CHAMber (ADCHAM) code [2] for xylene that is robust at reproducing the SOA mass yields we measure from our chamber experiments. We also show that the underlying autoxidation mechanisms are remarkably similar for many of the atmospherically dominant monocyclic aromatics, which opens the remarkable prospect of significantly improved model predictions of aromatic SOA even in the absence of theoretical and experimental data.

[1] Iyer, S., Kumar, A., Savolainen, A. et al. Molecular rearrangement of bicyclic peroxy radicals is a key route to aerosol from aromatics. Nat. Commun. 14, 4984 (2023). https://doi.org/10.1038/s41467-023-40675-2

[2] Roldin, P., Eriksson, A.C., Nordin, E.Z., Hermansson, E., Mogensen, D., Rusanen, A., Boy, M., Swietlicki, E., Svenningsson, B., Zelenyuk, A. and Pagels, J., 2014. Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas-and particle-phase chemistry kinetic multilayer model ADCHAM. Atmospheric Chemistry and Physics, 14(15), pp.7953-7993.

How to cite: Iyer, S., Kumar, A., Barua, S., Zhao, J., Savolainen, A., Seal, P., Pichelstorfer, L., Roldin, P., Ehn, M., and Rissanen, M.: Towards understanding aromatic SOA by studying the molecular level oxidations mechanisms of xylene isomers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9952, https://doi.org/10.5194/egusphere-egu24-9952, 2024.

11:35–11:45
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EGU24-7733
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On-site presentation
The atmospheric fate of cashmeran from musk-smelling volatile chemical products (VCPs) in chamber, indoor, and outdoor environments 
Nadine Borduas-Dedekind, Ayomide Akande, and Clémence Depp

Synthetic musk compounds, like cashmeran, are a group of semi-volatile organic compounds commonly used as fragrances in perfumes. In addition to being potential indoor pollutants, they are also regarded as emerging outdoor pollutants, known at volatile chemical products (VCPs). Cashmeran is a bicyclic synthetic musk compound, and a major component of a commercial perfume for men. Here, we aim to better predict the atmospheric fate of cashmeran indoors and outdoors using a Vocus proton transfer time-of-flight mass spectrometer.

Using the Vocus, we show that cashmeran was the dominant musk in a commercial perfume among other musk compounds like galaxolide, astratone, and rosamusk. Next, we measured the rate constant of cashmeran (C14H22O) with ozone for the first time under different experimental conditions to probe its ozonolysis mechanism. In the absence of O2, we calculated a rate constant of (2.78 ± 0.31) x 10-19 cm3mol-1s-1 at (293 ± 1) K and observed the formation of C14H22O2 as the key oxidation production. The ozonolysis reaction in the absence of O2 did not generate SOA. In the presence of O2, preliminary results show the rate constant to be 5.00 x 10-18 cm3mol-1s-1 at 293 K and the ozonolysis reaction formed SOA with a mass yield of 121 µg m-3. The rate constant observed in the presence of O2 indicate the importance of key carbon-radical chemistry and impact of partitioning sinks in understanding the fate of this molecule in the atmosphere. We hypothesize that the slow oxidation of cashmeran with ozone makes loss to partitioning to aerosols a competitive sink in determining its fate.

Furthermore, we investigated how partitioning sinks might be competitive to gas-phase oxidation for the fate of cashmeran from a commercial perfume in an office environment. We show that partitioning to cotton is the major sink, suggesting this molecule can be easily transported outdoors by humans and their clothing.

We further tested this hypothesis during THE CIX urban field campaign in Toronto, Canada in July-August 2023. We detected cashmeran outdoors throughout the campaign up to 10 ppt. As expected from a fragrant VCP, cashmeran peaked during the week only and in the morning. Based on our findings, we conclude that musk compounds, like cashmeran, are long-lived SVOCs capable of impacting urban air quality.

How to cite: Borduas-Dedekind, N., Akande, A., and Depp, C.: The atmospheric fate of cashmeran from musk-smelling volatile chemical products (VCPs) in chamber, indoor, and outdoor environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7733, https://doi.org/10.5194/egusphere-egu24-7733, 2024.

11:45–11:55
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EGU24-8748
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On-site presentation
Reversing the particulate-phase organosulfate chronology: Direct organosulfur compound synthesis in the gas-phase by SO3 + acid reactions 
Matti Rissanen, Siddharth Iyer, Shawon Barua, Emin Besic, Prasenjit Seal, and Avinash Kumar

Organosulfates (OS) are a major constituent of atmospheric secondary organic aerosol (SOA). In lack of apparent gas-phase compounds directly contributing to the particulate bound OS, their synthesis has been thought of taking place by acid-catalyzed reactions in the condensed phase, mainly initiated by H2SO4. The most well-known sulfur bearing molecules are the isoprene epoxydiol derived organosulfates (Riva et al., 2019). In 2015 Mackenzie et al., showed that under very dry condition SO3 can react to form sulfuric anhydrides by carboxylic acid + SO3 reactions (Mackenzie et al., 2015). More recently, several theoretical papers have reported a more general gas-phase source by SO3 reactions with a multitude of atmospheric acids. The potential importance of this newly found chemistry was highlighted by observations of gas-phase SO3 in urban Beijing at concentrations similar to H2SO4 (Yao et al., 2020), strongly implying that SO3 reactions are occurring in urban atmospheres.

In the present work we have performed a joint experimental-theoretical characterization of acid + SO3 reactions utilizing flow reactor setups coupled to nitrate (NO3-) chemical ionization mass spectrometry (CIMS) detection combined with supporting quantum chemical computations and master equation simulations. The studied reactions included mono- and dicarboxylic acids, and the strong acids most associated with atmospheric new particle formation events (i.e., H2SO4 and HIO3; Sipilä et al., 2016; Kerminen et al., 2018). Intriguingly, all acids were found to react rapidly with SO3 even with rate coefficients approaching the collision limit and were found to result in analogous acid sulfuric anhydride products. These sulfuric anhydrides provide a path for OS partitioning from gas to particle (i.e., “backwards” in considering the common particulate-phase synthesis route). Furthermore, the subsequent particulate-phase hydrolysis of the formed organic sulfuric anhydrides is a potential source of the small acids into the nanoparticles that would not be expected to partition significantly otherwise. The formed sulfuric anhydrides, especially the disulfuric acid and iodic acid sulfate, are likely to have similar, if not better, properties at initiating NPF as their parent compounds have.

References:

Kerminen, V.-M. et al., Atmospheric new particle formation and growth: review of field observations, Environ. Res. Lett. 2018, 13, 103003.

Mackenzie, R. et al., Gas Phase Observation and Microwave Spectroscopic Characterization of Formic Sulfuric Anhydride, Science 2015, 349, 58−61.

Riva, M. et al., Increasing Isoprene Epoxydiol-to-Inorganic Sulfate Aerosol Ratio Results in Extensive Conversion of Inorganic Sulfate to Organosulfur Forms: Implications for Aerosol Physicochemical Properties, Environ. Sci. Technol. 2019, 53, 8682-8694.

Sipilä, M. et al., Molecular-scale evidence of aerosol particle formation via sequential addition of HIO3, Nature 2016, 537, 532-534.

Yao, L. et al., Unprecedented ambient sulfur trioxide (SO3) detection: Possible formation mechanism and atmospheric implications, Environ. Sci. Technol. Lett. 2020, 7, 809-818.

How to cite: Rissanen, M., Iyer, S., Barua, S., Besic, E., Seal, P., and Kumar, A.: Reversing the particulate-phase organosulfate chronology: Direct organosulfur compound synthesis in the gas-phase by SO3 + acid reactions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8748, https://doi.org/10.5194/egusphere-egu24-8748, 2024.

11:55–12:05
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EGU24-18908
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ECS
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On-site presentation
Integrated model-measurement approaches to chamber SOA studies 
Hannah Kenagy, Colette Heald, Nadia Tahsini, Matthew Goss, and Jesse Kroll

Many of the quantitative descriptions of secondary organic aerosol (SOA) formation in regional and global models are derived from environmental chamber experiments, an experimental approach commonly used to assess multi-phase product distributions from atmospheric oxidation pathways.  As such, model accuracy for predicting aerosol abundance hinges on our ability to represent atmospheric conditions in chambers.  Here, we develop a new experimental approach that leverages both global modeling and detailed mechanisms to design chamber SOA experiments that capture atmospheric chemical environments for two key branching points in VOC oxidation: atmospheric oxidant balances and atmospheric RO2 chemistry. Using isoprene as a model system for multi-generation SOA production, we focus first on competition between oxidation by OH and Cl.  Global modeling indicates that multi-oxidant, multi-generation oxidation outcompetes single-oxidant, multi-generation oxidation in this system; we design and perform a series of chamber experiments to measure multi-phase product distributions from multi-oxidant, multi-generation isoprene oxidation.  Second, we develop a framework for quantitatively describing atmospheric RO2 chemistry and show that no previous experimental approaches to studying SOA formation have accessed the relevant atmospheric RO2 chemistry.  Leveraging multi-scale modeling, we design and perform a series of chamber experiments to measure isoprene SOA production under a range of atmospheric RO2 fate distributions.

How to cite: Kenagy, H., Heald, C., Tahsini, N., Goss, M., and Kroll, J.: Integrated model-measurement approaches to chamber SOA studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18908, https://doi.org/10.5194/egusphere-egu24-18908, 2024.

12:05–12:15
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EGU24-16619
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On-site presentation
Role played by Organic Nitrates in the Production of Secondary Organic Aerosol in a megacity 
Eleonora Aruffo, Junfeng Wang, Daniel J. Jacob, Jianhuai Ye, Xinlei Ge, and Piero Di Carlo

Secondary Organic Aerosol (SOA) production and chemical composition play a crucial role in the urban air pollution. Here, we used observations from two summer campaigns in Beijing in 2017 and 2023 to show that nighttime production of NOz (NOy - NOx) is particularly enhanced in specific conditions and that can play a significant role for SOA the next day. The observations showed nocturnal peaks of NOz of about 40 ppb, correlated with very high NO and NO2. We employed the Framework for 0-D Atmospheric Modeling (F0AM) model, based on the Master Chemical Mechanism (MCM), running simulations to investigate the organic nitrates (ONs) speciation, and founding that during the night the alkyl nitrates is the most abundant ONs, produced by oxidation of volatile organic compounds (VOCs) by the nitrate radical (NO3). Finally, we used the Framework for 0-D Atmospheric Modeling- Washington Aerosol Module (F0AM-WAM) model, which couple the gas phase chemistry with the SIMPOL representation for the particle phase, to correlate the nocturnal ONs peaks, that we suggested to be mainly in gas phase, to the diurnal particle growth events registered in Beijing.

How to cite: Aruffo, E., Wang, J., Jacob, D. J., Ye, J., Ge, X., and Di Carlo, P.: Role played by Organic Nitrates in the Production of Secondary Organic Aerosol in a megacity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16619, https://doi.org/10.5194/egusphere-egu24-16619, 2024.

12:15–12:25
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EGU24-13530
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ECS
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On-site presentation
Aircraft measurements of PAN (CH3C(O)OONO2) and PAA (CH3C(O)OOH) in the tropical atmosphere 
Carolina Nelson, Simone T. Andersen, and John N. Crowley
The two trace gases peroxyacetyl nitrate (PAN, CH3C(O)OONO2) and peracetic acid (PAA, CH3C(O)OOH) are products of reactions of the acetylperoxy radical with NO2 and HO2, respectively. They are formed during the oxidation of anthropogenic and biogenic VOCs and in biomass burning. PAN represents an important source of NOx in remote regions, while PAA is an indicator of the fate of peroxy radicals. To date, there have been very few simultaneous measurements of PAN and PAA. In this study, we present airborne measurements of PAN and PAA using a chemical ionization mass spectrometer (CIMS) in the clean troposphere above the Amazon rainforest in the framework of the CAFE Brazil measurement campaign. The absolute and relative abundances of PAN and PAA are analysed using data obtained during 20 flights performed during December 2022 until the end of January 2023.

How to cite: Nelson, C., Andersen, S. T., and Crowley, J. N.: Aircraft measurements of PAN (CH3C(O)OONO2) and PAA (CH3C(O)OOH) in the tropical atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13530, https://doi.org/10.5194/egusphere-egu24-13530, 2024.

12:25–12:30
Discussion

Posters on site: Mon, 15 Apr, 16:15–18:00 | Hall X5

Display time: Mon, 15 Apr, 14:00–Mon, 15 Apr, 18:00
Chairpersons: Jonathan Williams, Mikael Ehn, Juliane Fry
Biogenic VOC emissions
X5.94
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EGU24-10015
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ECS
Is green waste fertilization in agriculture an important source of VOC?  A field study based on  PTR-Qi-TOF-MS and eddy covariance 
Yang Liu, Pauline Buysse, Benjamin Loubet, Florence Lafouge, Anais Feron, Jérémie Depuydt, Florent Levavasseur, and Raluca Ciuraru

Agriculture is a potentially large yet poorly characterized source of volatile organic compounds (VOCs). Crops are the largest and most well-known source of VOCs from agriculture. Agricultural management practices, and especially organic fertilization is an especially unknown source of VOCs. A 3-week field campaign was conducted in September 2023 in Saclay, France, 30 km southwest of Paris. We investigated VOC fluxes over a mustard and moha field (cover crops) by eddy covariance using a PTR-Qi-TOF-MS. Green waste was applied during the second week of measurements.

We detected over a hundred VOCs with fluxes 3 times above the detection limit, and found that: 1) Oxygenated VOCs and monoterpenes are the most emitted compound groups. 2) High fluxes of methanol, ethanol, acetone, and acetaldehyde were detected after organic fertilizer spread. 3) A relatively strong sesquiterpene emission was observed after fertilization and was not previously reported. Our results provide new insights into VOC emissions from cover crops and green waste application.    

How to cite: Liu, Y., Buysse, P., Loubet, B., Lafouge, F., Feron, A., Depuydt, J., Levavasseur, F., and Ciuraru, R.: Is green waste fertilization in agriculture an important source of VOC?  A field study based on  PTR-Qi-TOF-MS and eddy covariance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10015, https://doi.org/10.5194/egusphere-egu24-10015, 2024.

X5.95
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EGU24-7764
Impact of meteorological conditions on BVOC emission rate from Eastern Mediterranean vegetation under drought  
Eran Tas, Qian Li, Efraim Lewinsohn, Einat Bar, and Maor Gabay

Biogenic volatile organic compounds (BVOCs) exert a significant influence on photochemical air pollution and climate change, with their emissions strongly affected by meteorological conditions. However, the effect of drought on BVOC emissions is not well-characterized, limiting the predictive power of this feedback on climate change and air quality. This study focused on two main objectives: i) test our hypothesis that under severe drought conditions, BVOC emissions will be more sensitive to instantaneous intraday variations in meteorological parameters than to the absolute values of those parameters; ii) test the impact of a plant under drought stress receiving a small amount of precipitation on BVOC emission rate, and the manner in which the emission rate is influenced by meteorological parameters. 

To address these objectives we employed: i) proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) to quantify the mixing ratios of a suite of soluble and insoluble VOCs (including isoprene, monoterpenes, sesquiterpenes, acetone, acetaldehyde, methanol, ethanol, formaldehyde, formic acid, acetic acid, 1,3-butadiene, dimethyl sulfide (DMS), and H2S) under severe drought conditions in a natural Eastern Mediterranean forest in autumn 2016 ; and ii) branch-enclosure sampling measurements in Ramat Hanadiv Eastern Mediterranean Nature Park, both under natural drought and after irrigation, for six selected branches of Phillyrea latifolia, the highest BVOC emitter in this park, during September–October 2020.

Notably, both independent analyses revealed that instantaneous changes in meteorological conditions, especially in relative humidity (RH), can serve as a better proxy for drought-related changes in BVOC emission rate than the absolute values of meteorological parameters. However, after irrigation (equivalent to 5.5–7 mm precipitation), the correlation of the detected BVOC emission rate with the instantaneous changes in RH became significantly more moderate, or even reversed. Our findings highlight that under drought, the instantaneous changes in RH, and to a lesser extent in temperature (T), are the best proxy for the emission rate of monoterpenes (MTs) and sesquiterpenes (SQTs), whereas under moderate drought conditions, T or RH serves as the best proxy for MT and SQT emission rate, respectively. In addition, the detected emission rates of MTs and SQTs increased by 150% and 545%, respectively, after the small amount of irrigation. The findings further highlight the importance of analyzing the effect of meteorological conditions on BVOC emissions under drought conditions on a daily—or shorter—timescale, and support biogenic emission sources for 1,3-butadiene.

How to cite: Tas, E., Li, Q., Lewinsohn, E., Bar, E., and Gabay, M.: Impact of meteorological conditions on BVOC emission rate from Eastern Mediterranean vegetation under drought , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7764, https://doi.org/10.5194/egusphere-egu24-7764, 2024.

X5.96
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EGU24-8639
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ECS
Emissions of biogenic volatiles from the coastal waters of Gulf of Finland, Baltic Sea.
(withdrawn)
Roseline Thakur, Maija Peltola, Amy Forsbacka, Kurt Spence, Heidi Hellén, Toni Tykkä, Joanna Norkko, Alf Norkko, Markku Kulmala, and Mikael Ehn
X5.97
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EGU24-18536
Exploring rice biomass burning and its chemical transformations in the Valencia Region 
Esther Borràs, Rubén Soler, Teresa Vera, Tatiana Gómez, Mila Ródenas, Enrique Mantilla, Eduardo Yubero, Javier Crespo, and Amalia Muñoz

Rice is one of the most widely cultivated cereals in the world. In Europe, rice cultivation is limited to Mediterranean countries, where geographical characteristics for rice production can be found. Spain is the second largest European producer. There are some regions in Spain, being Levante (Valencia) the most important one, with a long cultural, social, and gastronomic tradition associated with rice production. Valencian Community annually produce more than 60 kt of straw, a large part of which will follow a burning process of elimination due to sanitary reasons. The practice of burning it in the field produces harmful effects on the environment and human health.

The burning of rice straw, a common practice in many agricultural regions, continues to be a significant source of air emissions. causing frequent acute pollution episodes and exceedances of regulatory limits. However, there is a notable lack of knowledge about the nature of the emissions and their potential health hazards, as well as their contribution to secondary pollution and in particular to photochemical processes. Within this context, emissions and their chemical transformation were studied from 27/09/2023 to 02/11/2023 in the Valencia Region near a smoke-affected area. Using advanced analytical techniques, including gas chromatography, and particle analysis, a detailed evaluation of the components emitted during the burning of rice straw has been carried out. Various analytical instruments were used to characterize both the optical properties and chemical composition of the particle phase (aethalometers, nephelometer, PM low-cost sensors and PM10 and PM2.5 filters for offline analysis) and the gas phase (optical equipment, monitors, Tenax, DNPH and C18 cartridges, and high-resolution state-of-the-art spectrometers: PTR-MS), which allowed a detailed examination of the chemical composition, aging and transformation of the emissions.

The results reveal a diversity of gaseous pollutants, including nitrogen oxides (NOx), sulfur dioxide (SO2) and volatile organic compounds (VOCs), whose concentrations and compositions vary significantly depending on combustion conditions.In addition, an exhaustive characterization of the aerosols and particles generated has been carried out, highlighting the presence of fine particulate matter with potential impact on air quality and human health. The preliminary results show high values ​​of VOCs, PM10, PM2.5 and PM1 in the populated areas near the burned plots. These emissions also caused elevated ozone values up to 120 µg m-3 ​​in interior areas of the region, previously associated with high PM values.

These findings offer a deeper understanding of the complexity of emissions from rice straw burning and provide a solid foundation for future mitigation strategies and the development of environmental policies in affected regions.

 

This work is part of a project that is supported by ATMOBE  PID2022-1423660B-100 funded by MCIN/AEI/ 10.13039/501100011033 and,  by “ERDF A way of making Europe” and by PROMETEO (EVER project) CIPROM/20200/37

How to cite: Borràs, E., Soler, R., Vera, T., Gómez, T., Ródenas, M., Mantilla, E., Yubero, E., Crespo, J., and Muñoz, A.: Exploring rice biomass burning and its chemical transformations in the Valencia Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18536, https://doi.org/10.5194/egusphere-egu24-18536, 2024.

X5.98
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EGU24-160
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ECS
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Study of formaldehyde (HCHO) columns abundance from OMI satellite data in two agricultural regions in the south of Mexico 
Cristina Alejandra Mendoza Rodriguez, Claudia Ines Rivera Cardenas, and Carlos Crispin Espinosa Ponce

HCHO is one of the most abundant carbonyl compounds in the troposphere. At global scale, HCHO is mainly produced from the oxidation of volatile organic compounds (VOC) which come from biogenic (predominantly isoprene) emissions, biomass burning, and anthropogenic emissions. HCHO is produced in high amounts when both isoprene and nitrogen oxides (NOx, NO + NO2) are present. In order to determine the driver factors and the principal months of enhancement of HCHO over the Oaxaca and the Chiapas regions, important rain-fed maize agricultural areas located in the south of Mexico, HCHO columns from the Ozone Monitoring Instrument (OMI) were used in conjunction with isoprene emissions, NOx  emissions from biomass burning (NOx_bb), and NOx emissions from soils with their different sources (biomes: NOx_bio, fertilization and manure: NOx_fer, deposition of N: NOx_dep, pulses: NOx_pul, and total: NOx_tot) from January 2005 to December 2016. Based on scatterplots, Spearman rank correlations, and multiple regression models, we determined that isoprene and NOx_bb were important drivers of HCHO abundance in the Oaxaca region, especially in April and May. In the Chiapas region, important drivers were isoprene, NOx_bb, and NOx_fer, mainly from April to August. With the estimated regression coefficients, the contribution (in %) of the relevant emission fluxes for each region were calculated in order to know which source was the predominant one in the exacerbation of modeled HCHO (HCHOMOD). In the Oaxaca region, isoprene predominates over NOx_bb. In the Chiapas region, the emissions of NOx were more importantthan isoprene. NOx_bb and NOx_fer were enhanced principally due to the agricultural activity taking place in the Oaxaca and the Chiapas regions. Thus, this work demonstrates the impact of agricultural activity on HCHO columns observed by the OMI instrument.

How to cite: Mendoza Rodriguez, C. A., Rivera Cardenas, C. I., and Espinosa Ponce, C. C.: Study of formaldehyde (HCHO) columns abundance from OMI satellite data in two agricultural regions in the south of Mexico, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-160, https://doi.org/10.5194/egusphere-egu24-160, 2024.

X5.99
|
EGU24-7417
|
ECS
Investigating vertical gradients of trace gases and aerosol at the Amazon Tall Tower Observatory (ATTO) using MAX-DOAS measurements 
Sebastian Donner, Bianca Lauster, Steffen Ziegler, Paulo Artaxo, Steffen Beirle, Christian Gurk, Mark Lamneck, and Thomas Wagner

Multi-AXis (MAX)-Differential Optical Absorption Spectroscopy (DOAS) measurements use trace gas absorptions in spectra of scattered sun light recorded under different elevation angles to retrieve vertical profiles of trace gas concentrations and aerosol extinctions in the lower troposphere as well as the corresponding total tropospheric vertical column densities (VCDs). A major advantage of this kind of measurements is the possibility to observe multiple trace gases e.g., formaldehyde (HCHO), glyoxal (CHOCHO) and nitrogen dioxide (NO2), for the same air mass simultaneously with one instrument. A first MAX-DOAS instrument was installed at the Amazon Tall Tower Observatory (ATTO) at an altitude of 80 m above ground in October 2017. Since March 2019, a second instrument is operational at an altitude of 298 m. Besides the individual profile retrievals for both instruments, this measurement strategy allows the identification of (small scale) vertical gradients of trace gas and aerosol abundances by directly comparing the VCDs and concentrations (at instrument altitude) measured by both instruments. Such (small scale) vertical gradients provide important insights into the chemical processing of the different species. Located in a pristine rain forest region in the central Amazon Basin about 150 km north-east of Manaus, the ATTO site offers a rare possibility to study the chemical processing of tropospheric trace gases far from major anthropogenic emission sources. 

In the presented study, a general overview of the trace gas and aerosol results covering several years is provided. Thereby, a specific focus is put on the HCHO and glyoxal results including the annual variations of their abundances in the course of the characteristic alternation between wet and dry seasons. Based on the ratio of their abundances, our measurements indicate that different precursor compositions of both species prevail in the different seasons, whereby in the wet season the relative amount of precursors favouring the formation of glyoxal, e.g. monoterpenes, appears to be larger than in the dry season. In addition, (small scale) vertical gradients in the altitude range between both instruments are presented. Our results suggest that HCHO is mostly formed in the lowest 200 m above the canopy, while glyoxal is already degraded in this altitude range. Together with their characteristic profile shapes, these findings indicate different chemical processing (production and degradation) of HCHO and glyoxal, despite similar sources of their precursors.   

How to cite: Donner, S., Lauster, B., Ziegler, S., Artaxo, P., Beirle, S., Gurk, C., Lamneck, M., and Wagner, T.: Investigating vertical gradients of trace gases and aerosol at the Amazon Tall Tower Observatory (ATTO) using MAX-DOAS measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7417, https://doi.org/10.5194/egusphere-egu24-7417, 2024.

X5.100
|
EGU24-14533
|
ECS
Box-Modelling of O3 and its sensitivity towards VOCs and NOx in Mexico City under altered emission conditions
(withdrawn)
Tanzina Akther, Bernhard Rappenglueck, Beth Nelson, Alfred Mayhew, Armando Retama, and Olivia Rivera-Hernández
Anthropogenic sources
X5.101
|
EGU24-7218
|
ECS
Gaseous Nitrophenols sources and their contribution to HONO formation in an urban area 
Morshad Ahmed, Bernhard Rappenglueck, Lucksagoon Ganranoo, and Purnendu K Dasgupta

Nitrophenols (NPs) are compounds that comprise of hydroxyl (-OH) and nitro (-NO2) functional groups attached to at least one aromatic ring. NPs have significant impacts on human health, climate, and atmospheric chemistry. Despite numerous measurements of particulate NPs, little is still known about their gaseous atmospheric sources, chemistry, and fate. In this study, four gaseous NPs - 2,4-dinitrophenol (2,4-DNP), 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), and 2-Methyl-4-nitrophenol (2-Me-4-NP) were continuously monitored during late spring in an urban area of Houston, Texas. Among the four NPs, 4-NP showed the highest abundance, followed by 2-Me-4-NP, 2-NP, and 2,4-DNP, with average concentrations of 0.47 ± 0.12 ppt, 0.41 ± 0.16 ppt, and 0.27 ± 0.09 ppt, respectively. Utilizing the Positive Matrix Factorization (PMF) model, seven sources: industrial NPs, secondary formation, phenol sources, acetonitrile source, natural gas/crude oil, traffic, and petrochemical industries/oil refineries were identified with NPs’ contributions to each factor of 83.3%, 6.6%, 3.3%, 3.2%, 2.0%, 0.9%, and 0.7%, respectively. A zero-dimensional Atmospheric Chemistry (AtChem2) box model was used to simulate the observed 2-NP and 2,4-DNP. The model revealed a 50.0% and 70.0% contribution from JNO2, aligning with measured 2-NP and 2,4-DNP, respectively. This resulted in a nitrous acid (HONO) production of 7.5 ± 2.5 ppt/h between 06:00 and 18:00 Central Standard Time (CST) from both NPs. An extrapolation including other known NPs suggests a maximum HONO formation of 13.8 ppt/h, still magnitudes lower than other known HONO formation processes. Nevertheless, it represents a non-negligible fraction and should be considered in areas with substantial primary NPs emissions, and the corresponding reaction mechanisms should be included in any such model. Combining PMF analysis with a photochemical box model provides identification of NPs sources and their atmospheric impact on HONO formation, offering policymakers insights for implementing effective control measures.

How to cite: Ahmed, M., Rappenglueck, B., Ganranoo, L., and Dasgupta, P. K.: Gaseous Nitrophenols sources and their contribution to HONO formation in an urban area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7218, https://doi.org/10.5194/egusphere-egu24-7218, 2024.

X5.102
|
EGU24-8625
Evidences for the influence from key chemical structures of per- and polyfluoroalkyl substances on their environmental behaviors 
Yulong Yan, Yiru Zhuang, Jing Wu, Bingqi Dong, Fan Wang, Yu Bo, and Lin Peng

In recent years, perfluoroalkyl and polyfluoroalkyl substances (PFASs) have received widespread attention from the international community due to their persistence, long range atmospheric transport (LRAT), bioaccumulation and toxic. This study carried out the atmospheric and precipitation observation in Beijing for nearly one year, and firstly simultaneously observed the pollution characteristics of ultra short-chain, short-chain, long-chain PFASs and their main isomers, focusing on their gas-particle partitioning mechanism and dry and wet deposition characteristics. The results showed that the total concentration of PFASs was 3,415±2,932 pg m-3, of which ultra short-chain PFASs accounted for the highest proportion (55%), followed by short chains (41%) and long chains (3.9%). The proportion of short-chain PFASs was greater than that of long-chain PFASs which may be because short-chains have been produced and consumed as substitutes for long-chain PFASs. After deducting PFASs in the aqueous phase of particulate matter, the gas-particle partitioning coefficients (-7.04 m3 μg to -5.49 m3 μg) were about 3–4 units smaller than the previous results (-2.77 m3 μg to -1.51 m3 μg), which could more accurately reflect the phase partitioning characteristics between the gas phase and the hydrophobic phase of particulate matter. All PFASs and their main isomers were more distributed in the gas phase, followed by the aqueous phase of particulate matter and the hydrophobic phase of particulate matter. Dry deposition was dominant in the atmospheric deposition of each PFAS and isomer, but the relative contribution of dry deposition was significantly different. It was found that the gas-particle partitioning coefficient can be influenced by key chemical structures such as carbon chain length, functional group type, and isomer structure. Furthermore, the gas-particle partitioning can influence the dry and wet deposition of PFASs. Specifically, PFASs with longer carbon chains, carboxylic acid functional group or branched chain structures had larger gas-particle partitioning coefficients and can be more distributed in the hydrophobic phase of particulate matter, and their relative contributions of dry deposition were smaller.

How to cite: Yan, Y., Zhuang, Y., Wu, J., Dong, B., Wang, F., Bo, Y., and Peng, L.: Evidences for the influence from key chemical structures of per- and polyfluoroalkyl substances on their environmental behaviors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8625, https://doi.org/10.5194/egusphere-egu24-8625, 2024.

Measurement techniques
X5.103
|
EGU24-16754
Towards a complete picture of organics in the atmosphere with a filter-based CIMS approach 
Anna Franck, Henning Finkenzeller, Jyri Mikkilä, and Tuija Jokinen

Chemical Ionization Mass Spectrometry (CIMS) is an effective technique for accurate and sensitive detection of atmospheric organic compounds relevant to atmospheric chemistry and aerosol particle formation. Several types of mass spectrometers have been developed and used widely by the atmospheric community for online measurements. One of the limitations of the online technique is its size and weight and therefore, challenges in measuring in remote locations.

To facilitate measurements of organic vapours, a filter desorption unit was developed that can be easily mounted to APi-ToF (Tofwerk AG) or Orbitrap (ThermoFisher) mass spectrometers. Tenax-coated filters, which maximize the retention of organic vapours, are used for the collection of ambient air. Then, the collected filter deposit is thermally desorbed while the temperature rises to 200 C in three minutes. In the next step Multi-scheme chemical ionization inlet, MION2 (Karsa Ltd.), is used for chemical ionization with X-ray and preparation of the analyte to the detection in the mass spectrometer without further chromatographic separation. The whole process takes less than five minutes.

This new method has already been tested on various groups of compounds, including organics, and will be extended to more species in the near future.

In conclusion, the new filter-based approach in combination with the excellent detection limits of MION2, expands the use of CIMS instruments and opens possibilities for sampling in remote locations as well as on new platforms, such as drones.

How to cite: Franck, A., Finkenzeller, H., Mikkilä, J., and Jokinen, T.: Towards a complete picture of organics in the atmosphere with a filter-based CIMS approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16754, https://doi.org/10.5194/egusphere-egu24-16754, 2024.

X5.104
|
EGU24-15356
Multiphysical description of atmospheric pressure interface chemical ionization in MION2 & Eisele type inlets 
Henning Finkenzeller, Jyri Mikkilä, Paxton Juuti, Cecilia Righi, Nina Sarnela, and Juha Kangasluoma

The inlets of chemical ionisation mass spectrometers are fundamental instrument components in chemical ionisation mass spectrometry (CIMS). However, the sample gas and reagent ion trajectories are often understood only in a general and qualitative manner. Here we evaluate two common atmospheric pressure chemical ionisation inlets (MION2 and Eisele type inlet) with 3D physico-chemical models regarding the reagent ion and sample gas trajectories and evaluate their efficiencies of reagent ion production, reagent ion delivery from the ion source volume into the ion-molecule mixing region, and the interaction between reagent ions and target molecules. The models are validated by laboratory measurements and quantitatively reproduce observed sensitivities to tuning parameters, including ion currents and changes in mass spectra. The study elucidates how the different transport and chemical processes proceed within the studied inlets, how space charge is already relevant at concentrations of as low as 107 cm-3, and compares the two investigated models. The models provide insights into how to operate the inlets and will help in the development of future inlets that further enhance the capability of CIMS.

How to cite: Finkenzeller, H., Mikkilä, J., Juuti, P., Righi, C., Sarnela, N., and Kangasluoma, J.: Multiphysical description of atmospheric pressure interface chemical ionization in MION2 & Eisele type inlets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15356, https://doi.org/10.5194/egusphere-egu24-15356, 2024.

X5.105
|
EGU24-4712
A Bipolar Multi-Reagent Chemical Ionization Mass Spectrometer for Versatile Measurements of Gas and Particle Phase Organics 
Manjula Canagaratna, Harald Stark, Leah Williams, Mitch Alton, Taekyu Joo, Felipe Lopez-Hilfiker, Anita Avery, Veronika Pospisilova, Drew Gentner, and Andrew Lambe

Organic species in the atmosphere originate from a wide range of sources and processes. While real time chemical ionization mass spectrometry (CIMS) has improved our capability to characterize individual organic species in the atmosphere, the selectivity of CIMS reagent ions can limit the range of species that can be measured.  In this work the need to detect a broader range of species with a single CIMS instrument is addressed. A fast-switching bipolar time-of-flight CIMS that switches between four different reagent ions, including positive and negative ions, is demonstrated.  The performance and utility of this instrument is demonstrated by measurements obtained on board a ship in Antarctica during the PolarChange field campaign and from New York City during the AEROMMA campaign.  During both campaigns the instrument cycled through iodide (I-), benzene (C6H6+), and acetone dimer ((C3H6O)2H+) reagent ions at a 2 second data acquisition rate per cycle.  In the case of PolarChange, this combination of ions enabled simultaneous detection of trends in primary marine biological emissions such as dimethyl sulfide, nucleating species such as ammonia and methyl amine, and acids, such as nitric acid.  During AEROMMA, the fast bipolar switching capability enabled Eddy Correlation measurements of primary biogenic and urban emissions (i.e. monoterpenes and aromatics), secondary products of atmospheric oxidation (i.e. highly oxidized organics and organic nitrates), and reduced nitrogen species.  Preliminary results from this dataset, including positive matrix analyses of the combined multi-reagent ion datasets, are discussed.  Simultaneous gas and aerosol composition measurements obtained by coupling this mass spectrometer with aerosol inlets are also described.

How to cite: Canagaratna, M., Stark, H., Williams, L., Alton, M., Joo, T., Lopez-Hilfiker, F., Avery, A., Pospisilova, V., Gentner, D., and Lambe, A.: A Bipolar Multi-Reagent Chemical Ionization Mass Spectrometer for Versatile Measurements of Gas and Particle Phase Organics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4712, https://doi.org/10.5194/egusphere-egu24-4712, 2024.

X5.106
|
EGU24-6457
|
ECS
PAHs and levoglucosan in particulate matter sources apportionment through GC-C-IRMS and GC-MS 
Davide Di Rosa, Fabio Marzaioli, Maria Di Rosa, Salvatore Di Rosa, and Mauro Rubino

Air pollution is a leading cause of human health problems. Among various dangerous substances that may be found in atmosphere, Particulate Matter (PM) is one of the main concerns , since small size particles (<10 μm Ø) can easily enter the lungs and convey pollutants like heavy metals, dioxins, nitrogen oxides, etc.


EU directive 2008/50/CE of May 21st  2008 defines objectives for environmental air quality designed to avoid, prevent or reduce harmful effects on human health and the environment as a whole. The directive fines EU countries in which PM atmospheric concentration (in particular PM 10 and PM 2.5) and pollutants concentrations transported by the PM overcome certain limits, but those fines are applied only if the PM has anthropogenic origins ; therefore, it is essential to be able to perform PM sources apportionment.

 

For this purpose, in collaboration with the region Campania environmental agency (ARPAC), we are developing analytical methods for:

• Extraction and purification of some Polycyclic Aromatic Hydrocarbons ( PAHs ) from quartz filters (which are the physical supports where PM is collected during sampling). These molecules derive from incomplete combustion of organic matter (included fuels) and are present in PM emission of both anthropogenic and non anthropogenic sources.
• Extraction, purification, and derivatization of levoglucosan from quartz filters. Levoglucosan is a molecule deriving from the combustion of biomasses containing cellulose and hemicellulose and it is present in PM emission of both anthropogenic and non anthropogenic sources , like chimneys emissions and forest fires.
• The determination of isotopic ratio of carbon stable isotopes (δ 13C ) using isotopic ratio mass spectrometry coupled with gas chromatography GC-C-IRMS of PAHs and levoglucosan, which carbon isotopic fingerprint is dependent on the origin of these molecules.
• Target molecules identification by GC-MS.
• Quantitative analysis of PAHs on PM using GC MS method (US EPA 8270 E).
• Quantitative analysis of levoglucosan using Ionic Chromatography coupled with a Pulsed Amperometric Detector (IC-PAD).


ARPAC is collecting samples of PM 10 and PM 2.5 in different sites, both urban and rural, usinig both low volume (2.3 m3/h for 24h on 47mm Ø quartz filters) and high volume (100 L/min for 24h on 102mm Ø quartz filters) sampling methods. ARPAC will also provide PM samples collected at the main PM sources to get more accurate data about PAHs and levoglucosan isotopic fingerprint in their atmospheric emissions.


The attribution of these substances to anthropogenic sources and their quantification can provide essential information about the origins of the collected PM and, in case of PM limits exceeding, when it is possible, regional authorities of Campania could use the information collected to take steps to lower PM level.

How to cite: Di Rosa, D., Marzaioli, F., Di Rosa, M., Di Rosa, S., and Rubino, M.: PAHs and levoglucosan in particulate matter sources apportionment through GC-C-IRMS and GC-MS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6457, https://doi.org/10.5194/egusphere-egu24-6457, 2024.

Oxidation mechanisms
X5.107
|
EGU24-204
|
ECS
Elucidating Isoprene Oxidation: Pathways to Highly Oxygenated Molecules formation 
Liwen Yang, Wei Nie, Chao Yan, and Mikael Ehn

Isoprene is globally recognized as the preeminent biogenic volatile organic compounds (BVOCs) and is the most extensively researched species among volatile organic compounds (VOCs). Nevertheless, prevailing global and regional atmospheric models inadequately represent its molecular-level oxidation process. The predominate explicit chemical mechanisms, such as Master Chemical Mechanism (MCM) and CalTech isoprene mechanism, underestimate the complexities of isoprene oxidation, particularly the formation of Highly Oxygenated Molecules (HOMs) — a vital process from VOC to secondary organic aerosol (SOA). Here, we address a critical gap in the understanding of isoprene oxidation mechanism within existing models, especially the formation of fragmentation products and HOM-level oxidation products. The updated model integrates the influence of multigenerational OH-initiated oxidation and photolysis processes, thereby enriching the dynamics of free radical cycling. Our updated model was validated against previous molecular-level chamber experiments, demonstrating an enhanced ability to simulate the radical cycle and HOM formation, thus more accurately reflecting SOA formation.

How to cite: Yang, L., Nie, W., Yan, C., and Ehn, M.: Elucidating Isoprene Oxidation: Pathways to Highly Oxygenated Molecules formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-204, https://doi.org/10.5194/egusphere-egu24-204, 2024.

X5.108
|
EGU24-8261
Significant missing OH reactivity in the tropical marine boundary layer 
Lisa Whalley, Samuel Seldon, Graham Boustead, Rachel Lade, Dwayne Heard, Katie Read, Anna Callaghan, Shalini Punjabi, James Lee, Lucy Carpenter, and Luis Neves

It has recently been highlighted that observed OH reactivity (kOH) in the remote marine boundary layer cannot be fully explained by the measured or modelled speciated VOCs [1]. Understanding the identity and magnitude of the species that contribute to OH reactivity (and influence the concentration of OH) in the tropical marine boundary layer is particularly important however, as approximately 25 % of the total tropospheric methane removal, driven by the reaction with OH, occurs in this region [2].  Ground-based observations of kOH and comparisons with calculated or modelled kOH from individually measured VOCs and inorganics offers the opportunity to investigate diel trends and variabilities driven by changing air-masses, which can provide a valuable insight into the identity and impact of any missing kOH. We made the first observations of kOH at the Cape Verde Atmospheric Observatory in the remote tropical marine boundary layer in February 2023. The observed kOH ranged from 1.5 s-1 to 2.5 s-1 with the highest reactivity recorded when long-range transport of Saharan air-masses reached the observatory. The calculated kOH from the different inorganic and VOC species measured during the campaign did not capture the total kOH observed and even when the contribution from model-generated species (determined from a detailed 0D box model utilising the Master Chemical Mechanism) were considered, missing reactivity on the order of 0.2 – 0.5 s-1 remained, consistent with the levels of missing kOH previously determined in the marine boundary layer during the ATom aircraft campaign [1]. The diel profile highlighted that missing kOH was greatest during the night and morning and was at its lowest during the afternoon. Missing kOH correlated well with the OH reactivity contribution from species such as alkenes, CO and DMS, but was anti-correlated with the carbonyl reactivity suggesting the nature of the missing reactivity could be related to an unknown or unmeasured primary emission rather than a secondary species formed during the day via OH oxidation. Through modelling studies, we will present the impact that different missing primary emissions have on modelled OH concentrations and on the production of secondary oxygenated VOCs.

[1] Thames, A.B., et al., Missing OH reactivity in the global marine boundary layer, Atmospheric Chemistry and Physics, 2020, 20, 4013-4029.

[2] Bloss, W.J., et al., The oxidative capacity of the troposphere: Coupling of field measurements of OH and a global chemistry transport model. Faraday Discussions, 2005. 130: p. 425-436.

How to cite: Whalley, L., Seldon, S., Boustead, G., Lade, R., Heard, D., Read, K., Callaghan, A., Punjabi, S., Lee, J., Carpenter, L., and Neves, L.: Significant missing OH reactivity in the tropical marine boundary layer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8261, https://doi.org/10.5194/egusphere-egu24-8261, 2024.

X5.109
|
EGU24-16019
|
ECS
|
Ether and ester formation from peroxy radical recombination 
Lauri Franzon, Theo Kurtén, Bernard Aumont, Marie Camredon, and Richard Valorso
In a recent combined experimental and computational investigation (Peräkylä et al, JACS 145,35 7780–7790, 2023) of the Peroxy Radical Recombination (RO2 + RO2) products of α-pinene, we discovered a previously unknown product channel, in which the expected attachment of the two alkoxy radical (RO) intermediates into a peroxide accretion product (ROOR) is preceded by a rapid decomposition of one of the intermediate RO into an acyl-centered radical, resulting in the formation of a smaller but more stable ester accretion product R’(O)COR. In the presented work, the atmospheric implications of this new reaction channel have been explored further using a modified version of the GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere, Aumont et al, ACP 5, 2497–2517, 2005) to generate a large representative sample of RO2 + RO2 reactive pairs from the atmospheric oxidation of n-Decane, Toluene, the seven most common Monoterpene molecules) and one Sesquiterpene along with all the known decomposition channels of the intermediate RO formed in the reactions. The reaction rates of these decomposition channels are then compared to previous theoretical work on the product branching from RO2 + RO2 reactions (Hasan et al. JPCA, 124, 8305–8320, 2020 & 127, 1686–1696, 2023; Franzon JPCA 127, 5956–5966, 2023) to determine for which systems these RO decompositions might be competitive.

The generated chemical data is discussed in terms of the atmospheric formation of low-volatility organic molecules. Data is presented on the most important RO decomposition reactions for ether and ester accretion product formation, on vapour pressure trends of the various products, and on new accretion product-inhibiting reaction channels that at best produce two closed-shell molecules with the same carbon count as the reactant RO2.

Since our work is exploratory, and as the calculation of reaction rates rests on many assumptions, no certain conclusions can be drawn from our calculated product branching ratios. However, the present work provides valuable new insights on the formation of low-volatility organics in the atmosphere, and raises many open questions worthy of detailed studies of their own. We hope our results will be of great general interest to the atmospheric chemistry and physics community.

How to cite: Franzon, L., Kurtén, T., Aumont, B., Camredon, M., and Valorso, R.: Ether and ester formation from peroxy radical recombination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16019, https://doi.org/10.5194/egusphere-egu24-16019, 2024.

X5.110
|
EGU24-18564
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ECS
|
Computational study of cresol autoxidation: Initial steps in secondary organic aerosol formation 
Aliisa Ojala and Siddharth Iyer

Aromatic compounds, especially BTEX-compounds (benzene, toluene, ethylbenzene and xylene) and their derivatives can have an impact on the climate and human health through secondary organic aerosol (SOA) formation. They primarily originate from anthropogenic sources, such as vehicle emissions, industrial processes and solvent evaporation. These volatile organic compunds (VOCs) in the atmosphere can autoxidize, which is a sequential process of intramolecular reactions of peroxy radicals (molecules with R-O-O· structure) followed quickly by O2 additions. This leads to low-volatility products with multiple oxygen-containing functional groups, called highly oxygenated organic molecules (HOMs).[1] These molecules can condense irreversibly to form and grow SOA, which have an impact on the climate through the scattering and absorption of sunlight and acting as seeds for cloud formation.

The oxidation process for aromatics is initiated by OH-radicals, which leads quickly to bicyclic peroxy radical (BPR) intermediates in significant yields. BPRs retain the initial 6-membered ring, but add an additional endoperoxide bridge, consisting of two oxygen atoms, that connects to carbon atoms on both sides of the initiating OH-addition site. BPRs are sterically hindered, and their autoxidation is therefore slow, preferring to undergo bimolecular reactions with e.g. NO in polluted environments. Recently, a unimolecular pathway for ring-opening of BPRs was reported, leading to HOM formation in even sub-second timescales[2]. This opens up a pathway for aromatics to lead to SOA, even in non-polluted environments.

In this work, the autoxidation of cresols is studied. The cresol pathway is a major source of overall SOA for BTEX-compounds, as it is expected to account for up to 40% of toluene-related SOA formation[3]. ωB97XD/aug-cc-pVTZ-level of theory is used for geometry optimization with single point energy calculations done at ROHF-ROCCSD(T)-F12a/cc-pVDZ-F12-level. A thorough conformer sampling is done at a lower level of theory, and multi-conformer transition state theory (MC-TST) is used for rate calculations with Eckart-tunneling correction. For cresols, the OH-addition can happen at six different sites with different yields, leading to different chemistry. Preliminary results for ortho-cresol suggest that sites 3, 1 and 2 relative to the methyl group have the highest yields in descending order. Slow ring breakage is seen for the two highest yield addition sites, whereas fast ring breakage is seen for the BPR formed from 2-position addition. This is compatible with previous results for the ring-breaking of other substituted aromatic compounds[2]. The results of this study shed light on the SOA formation processes in the atmosphere. This will improve current models of SOA formation, which are known to have inconsistencies[1].

[1] Nault et al. Secondary organic aerosols from anthropogenic volatile organic compounds contribute substantially to air pollution mortality. Atmospheric Chemistry and Physics, 2021.
[2] Iyer et al. Molecular rearrangement of bicyclic peroxy radicals is a key route to aerosol from aromatics. Nature communications, 2023.
[3] Schwantes et al. Formation of highly oxygenated low-volatility products from cresol oxidation. Atmospheric Chemistry and Physics, 17(5):3453–3474, 2017.

How to cite: Ojala, A. and Iyer, S.: Computational study of cresol autoxidation: Initial steps in secondary organic aerosol formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18564, https://doi.org/10.5194/egusphere-egu24-18564, 2024.

X5.111
|
EGU24-7967
|
ECS
Elucidating formation of highly oxygenated organic molecules (HOMs) from α-pinene ozonolysis with isotopic labelling 
Melissa Meder, Frans Graeffe, Jingyi Luo, Yuanyuan Luo, Jonathan Varelas, Otso Peräkylä, Theo Kurtén, Matti Rissanen, Franz Geiger, Regan Thomson, and Mikael Ehn

Upon oxidation, some volatile organic compounds (VOCs) have been shown to go through a rapid process called autoxidation forming highly oxygenated organic molecules (HOMs). The exact autoxidation pathway taken affects the formation rates and the properties of the HOMs, however, a comprehensive step-by-step mechanism of HOM formation has not been described for any system of atmospheric relevance. In the autoxidation process, peroxy radical (RO2) intermediates undergo intramolecular hydrogen abstractions (H-shifts) followed by oxygen (O2) additions. This process can be monitored using chemical ionisation mass spectrometry and selective deuteration, where the precursor molecule has had the hydrogen atoms (1H) of a specific carbon replaced with deuterium atoms (2H). In this work, we studied the initial formation pathways of HOMs in reactions of the monoterpene α-pinene with ozone. We had access to all separately deuterated carbon positions in α-pinene that have hydrogens, i.e. we had in total eight different selectively deuterated α-pinenes. We were able to determine which of the deuterated precursors were prone to losing D during the (aut)oxidation process, which helped us understand the pathways leading to HOM formation.

How to cite: Meder, M., Graeffe, F., Luo, J., Luo, Y., Varelas, J., Peräkylä, O., Kurtén, T., Rissanen, M., Geiger, F., Thomson, R., and Ehn, M.: Elucidating formation of highly oxygenated organic molecules (HOMs) from α-pinene ozonolysis with isotopic labelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7967, https://doi.org/10.5194/egusphere-egu24-7967, 2024.

X5.112
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EGU24-8394
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ECS
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On the potential use of highly oxygenated organic molecules (HOM) as indicators for ozone formation sensitivity 
Jiangyi Zhang, Jian Zhao, Yuanyuan Luo, Valter Mickwitz, Douglas Worsnop, and Mikael Ehn

Ozone (O3), an important and ubiquitous trace gas, protects lives from harm of solar ultraviolet (UV) radiation in the stratosphere but is toxic to living organisms in the troposphere. Additionally, tropospheric O3 is a key oxidant, and source of other oxidants (e.g., OH and NO3 radicals) for various volatile organic compounds (VOC). Recently, highly oxygenated organic molecules (HOM) were identified as a new compound group formed from oxidation of many VOC, making up a significant source of secondary organic aerosol (SOA). The pathways forming HOM from VOC involve autoxidation of peroxy radicals (RO2), formed ubiquitously in many VOC oxidation reactions. The main sink for RO2 is bimolecular reactions with other radicals, HO2, NO or other RO2, and this largely determines the structure of the end products. Organic nitrates form solely from RO2 + NO reactions while accretion products (“dimers”) solely from RO2 + RO2 reactions. The RO2 + NO reaction also converts NO into NO2, making it a net source for O3 through NO2 photolysis.

There is a highly nonlinear relationship between O3, NOx, and VOC. Understanding the O3 formation sensitivity to changes in VOC and NOx is crucial for making optimal mitigation policies to control O3 concentrations. However, determining the specific O3 formation regimes (either VOC- or NOx-limited) remains challenging in diverse environmental conditions. In this work we assessed whether HOM measurements can function as a real-time indicator for the O3 formation sensitivity based on the hypothesis that HOM compositions can describe the relative importance of NO as a terminator for RO2. Given the fast formation and short lifetimes of the low-volatile HOM (timescale of minutes), they describe the instantaneous chemical regime of the atmosphere. In this work, we conducted a series of monoterpene oxidation experiments in our chamber while varying the concentrations of NOx and VOC under different NO2 photolysis rates. We also measured the relative concentrations of HOM of different types (dimers, nitrate-containing monomers, and non-nitrate monomers) and used ratios between these to estimate the O3 formation sensitivity. We find that for this simple system, the O3 sensitivity could be described very well based on the HOM measurements. Future work will focus on determining to what extent this approach can be applied in more complex atmospheric environments. 

How to cite: Zhang, J., Zhao, J., Luo, Y., Mickwitz, V., Worsnop, D., and Ehn, M.: On the potential use of highly oxygenated organic molecules (HOM) as indicators for ozone formation sensitivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8394, https://doi.org/10.5194/egusphere-egu24-8394, 2024.

X5.113
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EGU24-9218
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ECS
Atmospheric Oxidation of Imidazole by Hydroxyl Radicals: Fate of Peroxyl Radical Products 
Thomas Golin Almeida, Carles Martí, Theo Kurtén, Judit Zádor, and Sommer L. Johansen

In recent years, imidazole and its derivatives have received attention due to their role as components of brown carbon in atmospheric aerosol particles. These compounds absorb solar radiation in the UV-visible range, altering the aerosol optical properties, and acting as photosensitizers, prompting accelerated aerosol particle growth. Although atmospheric imidazoles are thought to be mainly produced in the particle-phase (e.g. via reaction of glyoxal with amines), these compounds were recently observed also in the gas-phase. Studies investigating the fate of imidazole in the gas-phase explored the initial steps of its oxidation by OH radical, identifying the major outcome to be the formation of an OH-addition product. However, this product is an alkyl (C-centered) radical, and its fate following reaction with O2 is still unexplored. In this work, we employed computational methods to investigate the reaction channels available to the first-generation peroxyl radicals produced from the reaction of imidazole with OH radical and O2. The unimolecular reaction pathways were explored with the automated reaction search and kinetics code KinBot. Product distributions under a range of temperatures and NOx concentrations were subsequently obtained by assembling and solving a master equation. Our findings predict that under most conditions considered, the formation of two major closed-shell products is expected: the cyclic diimine 4H-imidazole-4-ol, and the ring-opened species N,N’-diformylformamidine (FMF). The relative yields of these two products is, however, sensitive to NOx levels. While both compounds may be produced under pristine conditions (low NOx), the yield of FMF is predicted to be above 95 % under more polluted conditions (high NOx). These compounds may be further oxidized in the gas-phase, or they may partition into aerosol particles to participate in aqueous-phase reactions.

How to cite: Golin Almeida, T., Martí, C., Kurtén, T., Zádor, J., and Johansen, S. L.: Atmospheric Oxidation of Imidazole by Hydroxyl Radicals: Fate of Peroxyl Radical Products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9218, https://doi.org/10.5194/egusphere-egu24-9218, 2024.

X5.114
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EGU24-9054
How aromatic carbonyls autoxidize in the atmosphere? 
Prasenjit Seal, Shawon Barua, Avinash Kumar, Siddharth Iyer, and Matti Rissanen

Aromatic carbonyls, emitted either directly in the atmosphere or secondarily formed through hydrocarbon oxidations, represent one of the key members in the family of volatile organic compounds (VOCs). They are common constituents of natural and polluted atmospheres, and their gas-phase oxidation yields highly oxygenated organic molecules (HOM), which are key to the formation of atmospheric aerosol. Although, there are investigations in explaining the autoxidation chemistry of aliphatic carbonyls (Barua et al., 2023; Castañeda et al., 2012, Wang et al., 2015), insights underpinning the molecular level mechanism for the aromatic carbonyl autoxidation, on the other hand, have remained scarce (Iuga et al., 2008). The present work is an attempt to start filling this gap.

Herein, we conducted a combined theoretical-experimental analyses in atmospheric conditions for the OH radical initiated autoxidation of aromatic carbonyls, namely, benzaldehyde (PhCHO), acetophenone (PhCOCH3), and phenylethanal (PhCH2CHO). The energetics of the species in the proposed mechanism were obtained using high-level quantum chemical calculations. Subsequently, master equation simulations and multiconformer transition state theory (MC-TST) were used to estimate the rate coefficients and branching ratios for the autoxidation pathways.

A nitrate-based time-of-flight chemical ionization mass spectrometer (nitrate-CIMS) was used to detect the products in these oxidation reactions. Chemical ionization was achieved by supplying synthetic air (sheath flow) containing nitric acid (HNO3) under exposure to X-rays. This produces nitrate (NO3−) ions which are mixed with the sample flow and ionizes HOMs as NO3− adducts. The precursors are mixed in a quartz flow tube reactor where the oxidant OH is produced in-situ by the ozonolysis reaction of tetramethylethylene (TME).

The study indicates that autoxidation in aromatic carbonyls proceeds via a bicyclic peroxy radical (BPR) intermediate similar to that observed in case of toluene autoxidation (Iyer et al., 2023). The mechanism involves opening of the BPR ring to produce ring-broken intermediates having high excess energy. These nascent intermediates can then lead to several autoxidation pathways resulting in the HOM formation. Our flow reactor measurements for PhCHO oxidation at variable reaction times show the ample formation of HOM monomers and dimers, well in-line with the proposed mechanism. 

 

REFERENCES

Barua, S. et al. (2023). Atmos. Chem. Phys., 23, 10517–10532.

Castañeda, R. et al. (2012). J. Mex. Chem. Soc., 56, 316–324.

Iuga, C. et al. (2008). Chem. Phys. Chem., 9, 1453–1459.

Iyer, S. et al. (2023). Nat. Commun., 14, 4984.

Wang, S. et al. (2015). Proc. Combust. Inst., 35, 473–480.

How to cite: Seal, P., Barua, S., Kumar, A., Iyer, S., and Rissanen, M.: How aromatic carbonyls autoxidize in the atmosphere?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9054, https://doi.org/10.5194/egusphere-egu24-9054, 2024.

SOA formation
X5.115
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EGU24-6109
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ECS
Characterization of semi-volatile organic species in the particulate and gaseous phases in São Paulo, Brazil, and in the vicinity of Paris, France 
Olatunde Murana, Sebastien Dusanter, Marina Jamar, Samara Carbone, Lucas Chiari, Adalgiza Fornaro, Agnes Borbon, Christopher Cantrell, Manuela Cirtog, Vincent Michoud, Véronique Riffault, and Joel F. de Brito

Semi-volatile organic compounds (SVOCs) exist in both gaseous and particulate phases in the atmosphere, and are important intermediate species for the formation of secondary organic aerosols. In this study, both phases of SVOCs are studied in the vicinity of Paris, France, and within São Paulo, Brazil aiming to better understand the coupling between anthropogenic and biogenic emissions in distinct urban settings. Both regions are representative of strong anthropogenic and biogenic sources of pollutants. These areas were within the scope of the ACROSS (Atmospheric Chemistry of the Suburban Forest) and BIOMASP+ (Biogenic emissions, chemistry, and impacts in the Metropolitan Area of São Paulo) projects, respectively. The ACROSS campaign took place from June to July 2022 and data analyzed here were acquired at the Rambouillet (RMB) forested site, about 50 km southwest of Paris. BIOMASP+ conducted intensive observations in April and May 2023, and data were collected at the Institute of Astronomy, Geophysics, and Atmospheric Sciences (Matão-IAG) urban site, within the University of São Paulo campus. Continuous measurements of ambient organics through a CHemical Analysis of aeRosols ON-line (CHARON) inlet coupled to a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) were carried out at both sites, as well as complementary variables such as aerosol chemical composition, regulated pollutants, and meteorological parameters, among others.

The concentration of submicron bulk organic aerosol was comparable at both sites during ACROSS and BIOMASP+, reaching 5.0 µg/m3 and 7.3 µg/m3 for RMB and Matão-IAG, respectively. These are higher than typical 1-year averages observed at urban sites in Europe (3-4 µg/m3) [1] and previous observations near Matão-IAG in October 2012 (4.8 µg/m3) [2]. Biogenic VOCs showed distinct concentrations and temporal variabilities between sites with isoprene levels of 0.51 ppb vs 0.26 ppb of monoterpene in Brazil and Paris (0.35 ppb of isoprene vs 0.23 ppb of monoterpene) thus potentially leading to important differences in the subsequent secondary organic aerosol formation. Additionally, toluene, an anthropogenic marker, was higher at Matão-IAG (1.52 ppb) compared to RMB (0.25 ppb). This study will focus on SVOCs according to their mass spectra and temporal evolution and will compare the field observations to chamber experiments of biogenic and anthropogenic secondary organic aerosol formation. Those observations shall aid in understanding secondary formation processes and improve air quality modelling, as well as efficient pollution mitigation strategies in two contrasting large urbanized areas.

Keywords: SVOC, Sao Paulo, Paris, SOA, CHARON-PTR-ToF-MS

Acknowledgments: This work is funded and supported by Labex CaPPA, CPER ECRIN, ANR, and INSU LEFE-CHAT within the framework of BIOMASP and ACROSS projects. O. Murana’s field campaign in Brazil was supported by the Graduate Program “Science for a Changing Planet”, funded by the Program “Investissements d’avenir” (I-SITE ULNE / ANR-16-IDEX-0004 ULNE).

References

[1] Chen, G. et al., Environment International, vol. 166, p. 107325, 2022

[2] Almeida, G. P. et al., Atmos. Chem. Phys., vol. 14, no. 14, pp. 7559-7572, 2014

How to cite: Murana, O., Dusanter, S., Jamar, M., Carbone, S., Chiari, L., Fornaro, A., Borbon, A., Cantrell, C., Cirtog, M., Michoud, V., Riffault, V., and F. de Brito, J.: Characterization of semi-volatile organic species in the particulate and gaseous phases in São Paulo, Brazil, and in the vicinity of Paris, France, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6109, https://doi.org/10.5194/egusphere-egu24-6109, 2024.

X5.116
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EGU24-4669
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ECS
Biogenic particle formation over the southeastern Qinghai-Tibet Plateau is increasingly influenced by anthropogenic emissions 
Yuliang Liu

Aerosols formed on the Qinghai-Tibet Plateau, also known as the world's third pole, are more likely to enter the free troposphere due to its high altitude. This has far-reaching effects on radiative forcing and global climate. The southeastern Qinghai-Tibet Plateau, adjacent to the Himalayas, is commonly regarded as a pristine area that can offer insight into aerosol formation under pre-industrial conditions, free from the influence of human activities. Here we present observations taken at a representative site in southeast Tibet, a region covered by alpine forests and grasslands. The average aerosol particle nucleation rate (J1.7) is 2.5 cm-3s-1, exceeding the kinetic limit of sulfuric acid (SA) nucleation in most cases due to the low SA concentrations (with a mean of 2.5×105 cm-3). The critical role of highly oxygenated organic molecules (HOMs) in in-situ aerosol production is then to be found. Ultra-low and extremely low volatile HOMs dominate particles' nucleation and initial growth, respectively. Furthermore, these organic vapors come from the atmospheric oxidation of biogenic precursors, mainly monoterpenes with some contributions from sesquiterpenes and diterpenes. Surprisingly, over half of the ultra- and extremely-low volatile HOMs are organic nitrates, mainly formed through RO2 + NO terminations or NO3-initiated oxidations. These findings suggest that anthropogenic emissions influence the chemistry that drives biogenic new particle formation in the southeastern Qinghai-Tibet Plateau. As human activity increases, this region is transitioning from a pre-industrial to a post-industrial environment. The potential impact of this process on aerosol production and climate should be given more consideration.

How to cite: Liu, Y.: Biogenic particle formation over the southeastern Qinghai-Tibet Plateau is increasingly influenced by anthropogenic emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4669, https://doi.org/10.5194/egusphere-egu24-4669, 2024.

X5.117
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EGU24-9137
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ECS
Changes in atmospheric aerosols from reduced BVOC precursors in future deforestation scenarios 
Ryan Vella, Matthew Forrest, Alexandra Tsimpidi, Andrea Pozzer, Thomas Hickler, Jos Lelieveld, and Holger Tost

Biogenic volatile organic compounds (BVOC) are emitted in large quantities from the terrestrial biosphere and play a significant role in major atmospheric processes. Such emissions account for 90\% of the total volatile organic compound (VOC) emissions and exert a significant influence on the atmosphere's oxidation capacity. The oxidation of BVOCs yields intermediate species with lower vapour pressures, resulting in organic condensation and the formation of secondary organic aerosols (SOA). SOA directly affect the radiation budget through scattering and absorption, as well as indirectly by modifying cloud formation and distribution. It has been shown that changes in atmospheric states due to SOA contribute to feedbacks with vegetation, exerting a significant impact on global BVOC budgets. Despite their contribution to the uncertainty surrounding the impact of carbonaceous aerosols on future climate forcings, BVOC-climate feedbacks are often neglected in modelling studies. In this work, we use the chemistry-climate model EMAC coupled with the dynamic global vegetation model (DGVM) LPJ-GUESS, enabling interactive calculations of BVOC emission fluxes that respond to changes in atmospheric and vegetation states. We employ deforestation scenarios using different projections for pasture land to disturb the natural potential vegetation simulated in LPJ-GUESS. Utilising a sophisticated description of secondary organic aerosols, the direct relation of atmospheric particles originating from interactive isoprene and terpene fluxes with the atmospheric state can be analysed. Consequently, we use state-of-the-art process descriptions in EMAC to study the impacts of biogenic SOA on global radiation budgets and clouds, shedding light on potential future changes in the atmosphere resulting from perturbations in the biosphere.

How to cite: Vella, R., Forrest, M., Tsimpidi, A., Pozzer, A., Hickler, T., Lelieveld, J., and Tost, H.: Changes in atmospheric aerosols from reduced BVOC precursors in future deforestation scenarios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9137, https://doi.org/10.5194/egusphere-egu24-9137, 2024.

X5.118
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EGU24-15717
Modelling the influence of biogenic SOA precursor volatility on aerosol forcing 
Muhammed Irfan, Thomas Kühn, Taina Yli-Juuti, Anton Laakso, Eemeli Holopainen, Douglas R. Worsnop, Annele Virtanen, and Harri Kokkola

Secondary organic aerosol (SOA) plays a significant role in atmospheric processes, influencing particulate matter, air quality, and global climate. The volatility basis set (VBS) framework facilitates simulating the large number of SOA species by grouping SOA precursors based on volatility, thus reducing computational challenges. However, volatilities of SOA forming vapors are inadequately constrained in global climate models, causing uncertainties in predicted aerosol mass loads and climate effects. Using a process-scale particle growth model and a global climate model, we analyse the sensitivity of simulated cloud condensation nuclei (CCN) and SOA mass concentrations to the volatility distribution of SOA precursor gases from monoterpenes emitted by boreal trees. Our findings reveal that uncertainties in the volatilities of condensing organic vapors significantly affect particle growth rates and CCN survival in the process-scale model. Global model simulations show less sensitivity in CCN and cloud droplet number concentration (CDNC). A one order of magnitude shifts in volatility results in a 13% increase or a 9% decrease in SOA mass concentration over the boreal region. Furthermore, the study compares a finely resolved 9-bin VBS setup and a coarser 3-bin VBS setup, highlighting the importance of accurately representing saturation concentration values for volatility bins, especially in global models with reduced bin numbers. In addition, the study found that the radiative forcing attributed to changes in SOA is notably more sensitive to the volatility distribution of semi-volatile compounds than low-volatile compounds. This underscores the need for improved representations of semi-volatile compounds in global scale models to accurately predict aerosol loads and subsequent climate effects.

How to cite: Irfan, M., Kühn, T., Yli-Juuti, T., Laakso, A., Holopainen, E., R. Worsnop, D., Virtanen, A., and Kokkola, H.: Modelling the influence of biogenic SOA precursor volatility on aerosol forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15717, https://doi.org/10.5194/egusphere-egu24-15717, 2024.