Aerosol Chemistry and Physics (General Session)

Aerosol particles are key components of the earth system important in radiative balance, human health, and other areas of key societal concern. Understanding their formation, evolution and impacts relies on developments from multiple disciplines covering both experimental laboratory work, field studies and numerical modelling. In this general session all topics of Aerosol Chemistry and Physics are covered. Contributions from aerosol laboratory, field, remote sensing and model studies are all highly encouraged.

As in previous years, this year the session will dedicate some of its time to focus on a hot topic which this year is on the use of statistical methods and machine learning across a range of scales in aerosol research: from studies designed to decipher source and/or process contributions to measured aerosol signatures through to the role of aerosols in climate projections. Regarding the latter, we will be presenting contributions related to the H2020 project FORCeS which aims at reducing the uncertainty related to aerosols in climate projections.

Why focus on such a broad scale of activities? The aerosol community has spent significant effort developing and deploying a range of instruments to capture the evolving chemical and physical properties of laboratory and ambient systems. This information in turn should be used to better constrain source and process contributions in mechanistic and/or impact driven models. As the resolving power of such instruments to provide us with a 'snapshot' of a chemical signature increases, through a given form of instrument response, so to must we evaluate the usefulness of a range of analytical methods to convert those signatures into information about source and process contributions. Likewise, as the complexity of information on aerosol evolution increases, we must consider alternative ways for improving such descriptions in large-scale impact driven models. As the availability of various machine learning and statistical packages increases, we are now able to start conducting such research. With this in mind, aside from general submissions on aerosol research, we encourage contributions from this emerging area of research.

Convener: Ilona Riipinen | Co-conveners: David Topping, Annele Virtanen
vPICO presentations
| Mon, 26 Apr, 09:00–12:30 (CEST), 13:30–15:00 (CEST)

vPICO presentations: Mon, 26 Apr

A stationary tropospheric sulphur cycle for Earth system models of intermediate complexit
Alexey V. Eliseev, Rustam D. Gizatullin, and Alexandr V. Timazhev
Lise Deschutter, Hervé Herbin, and Denis Petitprez

Spectrometers are powerful instruments to detect atmospheric aerosols, especially on satellites since they allow measurements at a global scale and over different spectral ranges with high spectral resolution. However, to fully exploit their capabilities and to link optical properties, chemical composition and mass concentration, it is essential to have reference optical properties of various particles and mainly the complex refractive indices (CRI). The CRI of a natural aerosol source can be determined from a real sample of it or applying the effective medium approximation using the CRI of the pure compounds present in the natural sample. But in that case, it is necessary to know the mass fraction of each individual compound and above all their CRI. Nevertheless, the literature and CRI databases provide only reflectance measurements on bulk materials or pressed pellets and over a limited wavelength range (Querry et al., 1987).

In the present work, dust from the Gobi desert is studied as it is the second most active dust source, after the Sahara desert, in terms of mass emissions (Querol et al., 2019). For that extinction spectra have been recorded for natural Gobi dust sample and for its major compounds (Illite, Calcite and Quartz). Particles as a powder in a vessel are generated thanks to a magnetic stirring and a flow of nitrogen (Hubert et al., 2017). The continuous flow of aerosols is directed into a 10-meters multipass cell fitted to a Fourier transform infrared spectrometer and a 1-meter singlepass cell within a UV-Visible spectrometer which cover a continuous spectral range from 650 cm-1 to 40000 cm-1. Moreover, at the exit of the spectrometers the size distribution is recorded by an aerodynamic particle sizer and a scanning mobility particle sizer which allow to measure size particles from 14 nm to 20 µm. An inversion algorithm is carried out using experimental extinction spectra and the size distribution as input data (Herbin et al., 2017). Applying the Mie theory and the single subtractive Kramers-Kröning integral, the real and the imaginary part of the CRI are retrieved at each wavelength with an optimal estimation method.

For the first time, CRI of Illite has been retrieved with a high spectral resolution (1 cm-1) and over a wide spectral range for suspended particles. For calcite and quartz particles, the crystalline phase has to be considered by introducing the ordinary and extraordinary indices. These pure compound sets of CRI will be used for testing effective medium approximation on Gobi dust for which effective CRI have been also retrieved.

How to cite: Deschutter, L., Herbin, H., and Petitprez, D.: Optical properties of Gobi dust and its pure compounds: experimental extinction spectra and complex refractive indices determination., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2115,, 2021.

Wei Huang, Haiyan Li, Nina Sarnela, Liine Heikkinen, Yee Jun Tham, Jyri Mikkilä, Steven J. Thomas, Neil M. Donahue, Markku Kulmala, and Federico Bianchi

The molecular composition and volatility of gaseous organic compounds were investigated during April–July 2019 at the Station for Measuring Ecosystem – Atmosphere Relations (SMEAR) II situated in a boreal forest in Hyytiälä, southern Finland. A Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus PTR-ToF; hereafter Vocus) was deployed to measure volatile organic compounds (VOC) and less oxygenated VOC (i.e., OVOC). In addition, a multi-scheme chemical ionization inlet coupled to an atmospheric pressure interface time-of-flight mass spectrometer (MION APi-ToF) was used to detect less oxygenated VOC (using Br as the reagent ion; hereafter MION-Br) and more oxygenated VOC (including highly oxygenated organic molecules, HOM; using NO3 as the reagent ion; hereafter MION-NO3). The comparison among different measurement techniques revealed that the highest elemental oxygen-to-carbon ratios (O:C) of organic compounds were observed by the MION-NO3 (0.9 ± 0.1, average ± 1 standard deviation), followed by the MION-Br (0.8 ± 0.1); and lowest by Vocus (0.2 ± 0.1). Diurnal patterns of the measured organic compounds were found to vary among different measurement techniques, even for compounds with the same molecular formula, suggesting contributions of different isomers detected by the different techniques and/or fragmentation from different parent compounds inside the instruments. Based on the complementary molecular information obtained from Vocus, MION-Br, and MION-NO3, a more complete picture of the bulk volatility of all measured organic compounds in this boreal forest was obtained. As expected, the VOC class was the most abundant (about 49.4 %), followed by intermediate-volatility organic compounds (IVOC, about 48.9 %). Although condensable organic compounds (low-volatility organic compounds, LVOC; extremely low-volatility organic compounds, ELVOC; and ultralow-volatility organic compounds, ULVOC) only comprised about 0.3 % of the total gaseous organic compounds, they play an important role in new particle formation as shown in previous studies in this boreal forest. Our study shows the full characterization of the gaseous organic compounds in the boreal forest and the advantages of combining Vocus and MION APi-ToF for measuring ambient organic compounds with different oxidation extent (from VOC to HOM). The results therefore provide a more comprehensive understanding of the molecular composition and volatility of atmospheric organic compounds as well as new insights in interpreting ambient measurements or testing/improving parameterizations in transport and climate models.

Wei Huang and Haiyan Li contributed equally to this work.

Correspondence to: Wei Huang ( and Federico Bianchi (

How to cite: Huang, W., Li, H., Sarnela, N., Heikkinen, L., Tham, Y. J., Mikkilä, J., Thomas, S. J., Donahue, N. M., Kulmala, M., and Bianchi, F.: Molecular composition and volatility of gaseous organic compounds in a boreal forest: from volatile organic compounds to highly oxygenated organic molecules, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2819,, 2021.

Harshita Pawar and Baerbel Sinha

November onwards, the poor air quality over north-west India is blamed on the large-scale paddy residue burning in Punjab and Haryana. However, the emission strength of this source remains poorly constrained due to the lack of ground-based measurements within the rural source regions. In this study, we report the particulate matter (PM) levels at Nadampur, a rural site in the Sangrur district of Punjab that witnesses rampant paddy residue burning, using the Airveda low-cost PM sensors from October to December 2019. The raw PM measurements from the sensor were corrected using the Random Forest machine learning algorithm. The daily average PM10 and PM2.5 mass concentration at Nadampur correlated well  (r > 0.7) with the daily sum of VIIRS fire counts. Agricultural activities, including paddy residue burning and harvesting operations, contributed less than 40% to the overall PM loading, even in the peak burning period at Nadampur. We show that the increased residential heating emissions in the winter season have a profound and currently neglected impact on ambient air quality. A dip in the daily average temperature by 1 ºC increased the daily emission of PM10 by 6.3 tonnes and that of PM2.5 by 5.8 tonnes. Overall, paddy harvest, local and regional paddy residue burning, residential heating emissions, ventilation, and wet scavenging could explain 79% of the variations in PM10 and 85% of the variations in PM2.5. Day to day variations in PM emissions from residential heating in response to the ambient temperature must be incorporated into emission inventories and models for accurate air quality forecasts.

How to cite: Pawar, H. and Sinha, B.: Day-to-day variations in paddy-residue burning and residential heating emissions control aerosol pollution peaks in rural north-west India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3289,, 2021.

Mahtab Majdzadeh, Craig Stroud, Christopher Sioris, Paul Makar, Ayodeji Akingunola, Chris McLinden, Xiaoyi Zhao, Michael Moran, Ihab Abboud, and Jack Chen

The photolysis module in Environment and Climate Change Canada’s on-line chemical transport model GEM-MACH (GEM: Global Environmental Multi-scale – MACH: Modelling Air quality and Chemistry) was improved by using the on-line chemical composition and size-resolved representation of atmospheric aerosols in GEM-MACH to calculate the attenuation of radiation in the photolysis module.

We coupled both the GEM-MACH aerosol module and the MESSy-JVAL (Modular Earth Sub-Model System) photolysis routine through the use of the on-line aerosol modeled data and a new Mie lookup table for the model-generated extinction efficiency, absorption and scattering cross sections of each aerosol. The new algorithm applies a lensing correction factor to the black carbon absorption efficiency (core-shell parametrization) and calculates the scattering and absorption optical depth and asymmetry factor of black carbon, sea-salt, dust and other internally mixed components.

In order to evaluate the effects of these modifications on the performance of the GEM-MACH model, a series of simulations with the updated version of MESSy-JVAL and wildfire emission inputs from the Canadian Forest Fire Emissions Prediction System (CFFEPS) were carried out, and the model aerosol optical depth (AOD) output was compared to the previous version of MESSy-JVAL, satellite data, ground-based measurements, and re-analysis products. The comparison of the updated version of MESSy-JVAL with the previous version showed significant improvements in the model performance with the implementation of the new photolysis module and adopting the online interactive aerosol concentrations in GEM-MACH.

How to cite: Majdzadeh, M., Stroud, C., Sioris, C., Makar, P., Akingunola, A., McLinden, C., Zhao, X., Moran, M., Abboud, I., and Chen, J.: Impact of Interactive Aerosol Feedbacks on Photolysis Rates and Air Quality for Urban and Industrial Areas in Canada using the GEM-MACH Air Quality Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3367,, 2021.

Fabian Mahrt, Yuanzhou Huang, Shaun Xu, Manabu Shiraiwa, Andreas Zuend, and Allan Bertram

Aerosol particles are ubiquitous in the atmosphere and play an important role for air quality and Earth’s climate. Primary organic aerosol (POA), secondary organic aerosol (SOA), and secondary inorganic aerosol (SIA) constitute a significant mass fraction of these particles. POA, SOA, and SIA can become internally mixed within the same particle though different processes such as coagulation, gas–particle partitioning. To predict the role of these internally mixed particles in climate and air quality information on their phase behaviour is needed, i.e. information on the number and type of phases present within these particles. As an example, a particle with a single homogeneous liquid phase can have different radiative properties, reaction rates, uptake kinetics, and potential to change cloud microphysical properties by activating into a cloud droplet, compared to a particle with multiple liquid or solid phases.

In the current study we used Nile red, a solvatochromic dye, and fluorescence microscopy in order to determine the phase behaviour of POA+SOA+SIA particles. Squalane was used as a proxy of POA, ammonium sulfate was used as SIA and 1 of 23 different oxidized organic molecules were used as proxies of SOA. We demonstrate that three liquid phases often coexist within individual particles. We find that the phase behaviour strongly depends on the oxygen-to-carbon ratio of the SOA proxies. Experiments with SOA generated by dark ozonolysis of α-pinene in an environmental chamber are consistent with these observations. We also used thermodynamic and kinetic modelling to investigate the atmospheric implications of our experimental results.

How to cite: Mahrt, F., Huang, Y., Xu, S., Shiraiwa, M., Zuend, A., and Bertram, A.: Coexistence of three liquid phases in atmospheric aerosol particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3694,, 2021.

Valentin Hanft, Ralph Kleinschek, Marvin Knapp, Astrid Müller, Matthias Frey, Hiroshi Tanimoto, Isamu Morino, Frank Hase, Philip Holzbeck, and André Butz

Validation opportunities for model data and satellite observations in the short-wave infra-red spectral range for climate monitoring are still sparse above the oceans. Klappenbach et al. (2015) and Knapp et al. (2020) developed a ship-borne setup of a Fourier-transform spectrometer (EM27/SUN FTS) for direct sunlight observations on mobile platforms such as ships or pick-ups. The housing withstands oceanic on-deck-conditions and is equipped with a custom-built fast solar tracker. Knapp et al. (2020) tested the system on a ship cruise from Vancouver, Canada to Singapore for a five-week period in 2019, during which the instrument performed reliably. The tracker provided a pointing precision of better than 0.05° for 79% of the time. The precision of atmospheric total column densities retrieved from the FTS direct sunlight spectra was found to be 0.24ppm for carbon dioxide (CO2), 1.1ppb for methane (CH4), and 0.75ppb for carbon monoxide (CO).

Our ultimate goal is to develop the setup towards autonomous operations on ships to routinely collect validation data for CO2, CH4, and CO column densities above the world's oceans. Therefore, we further improved on the FTS box. Most prominent is a simplification of the tracking algorithm from two-dimensional mapping to two one-dimensional functions, moving a 185° fisheye camera onto the tracking rotation stage, and a change to more reliable embedded computers. Those modifications allow for sun tracking down to a solar zenith angle of 75° and increase robustness against mechanical misalignments between tracker and camera. A test campaign was conducted in the vicinity of a local coal power plant in Mannheim, Germany by mounting the FTS box on a pick-up and driving a stop-and-go pattern perpendicular to the plume direction. To this purpose, a 24 V battery powering mode was implemented.

We plan another deployment of the instrument on the Japanese research vessel Mirai in February 2021. The campaign is conducted in cooperation with the Japanese National Institute for Environmental Studies (NIES) in the western North Pacific. Such routine validation opportunities of atmospheric CO2, CH4, and CO column densities would be a valuable asset for global climate monitoring.



Knapp, M., Kleinschek, R., Hase, F., Agustí-Panareda, A., Inness, A., Barré, J., Landgraf, J., Borsdorff, T., Kinne, S., and Butz, A.: Ship-borne measurements of XCO2, XCH4, and XCO above the Pacific Ocean and comparison to CAMS atmospheric analyses andS5P/TROPOMI, Earth System Science Data Discussions, 2020, 1–20,,, 2020.

Klappenbach, F., Bertleff, M., Kostinek, J., Hase, F., Blumenstock, T., Agusti-Panareda, A., Razinger, M., and Butz, A.: Accurate mobileremote sensing of XCO2 and XCH4 latitudinal transects from aboard a research vessel, Atmospheric Measurement Techniques, 8,5023–5038,, 2015.

How to cite: Hanft, V., Kleinschek, R., Knapp, M., Müller, A., Frey, M., Tanimoto, H., Morino, I., Hase, F., Holzbeck, P., and Butz, A.: Towards An Automated Ship-Borne Fourier-Transform Spectrometer As a Validation Opportunity For Atmospheric CO2, CH4, And CO Column Densities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4030,, 2021.

Guangjie Zheng, Hang Su, Siwen Wang, Meinrat Andreae, Ulrich Pöschl, and Yafang Cheng

Aerosol acidity largely regulates the chemistry of atmospheric particles, and resolving the drivers of aerosol pH is key to understanding their environmental effects. We find that an individual buffering agent can adopt different buffer pH values in aerosols and that aerosol pH levels in populated continental regions are widely buffered by the conjugate acid-base pair NH4+/NH3 (ammonium/ammonia). We propose a multiphase buffer theory (Zheng et al., 2020, Science) to explain these large shifts of buffer pH, and we show that aerosol water content and mass concentration play a more important role in determining aerosol pH in ammonia-buffered regions than variations in particle chemical composition. Our results imply that aerosol pH and atmospheric multiphase chemistry are strongly affected by the pervasive human influence on ammonia emissions and the nitrogen cycle in the Anthropocene.


Zheng, G., Su, H.*, Wang, S., Andreae, M. O., Pöschl, U., and Cheng, Y.*: Multiphase buffer theory explains contrasts in atmospheric aerosol acidity, Science, 369, 1374-1377, 2020.

How to cite: Zheng, G., Su, H., Wang, S., Andreae, M., Pöschl, U., and Cheng, Y.: Multiphase buffer theory explains contrasts in atmospheric aerosol acidity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4936,, 2021.

Roman Bardakov, Joel Thornton, Ilona Riipinen, Radovan Krejci, and Annica Ekman

Transport of organic trace gases by deep convective clouds plays an important role for new particle formation (NPF) and particle growth in the upper atmosphere. Isoprene accounts for a major fraction of the global volatile organic vapor emissions and a significant fraction is emitted in the Amazon. We examined transport and chemical processing of isoprene and its oxidation products in a deep convective cloud over the Amazon using a box model. Trajectories of individual air parcels of the cloud derived from a large eddy simulation are used as input to the model. Our results show that there exist two main pathways for NPF from isoprene associated with deep convection. The first one is when the gas transport occurs through a cloud with low lightning activity and with efficient gas uptake of low-volatile oxidation products by ice particles. Some of the isoprene will reach the cloud outflow where it is further aged and produces low volatile species capable of forming and growing new particles. The second way is via transport through clouds with high lightning activity and with low gas uptake by ice. For this case, low volatile oxidation products will reach the immediate outflow in concentrations close to the values observed in the boundary layer. The efficiency of gas condensation on ice particles is still uncertain and further research in this direction is needed.

How to cite: Bardakov, R., Thornton, J., Riipinen, I., Krejci, R., and Ekman, A.: Transport of isoprene and its oxidation products by deep convective clouds in the Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5755,, 2021.

Arun Bs, Mukunda Gogoi, Prashant Hegde, and Suresh Babu

The rapid changes in the pattern of atmospheric warming over the Himalayas, along with severe degradation of Himalayan glaciers in recent years suggest the inevitability of accurate source characterization and quantification of the impact of aerosols on the Himalayan atmosphere and snow. In this regard, extensive study of the chemical compositions of aerosols at two distinct regions, Himansh (32.4N, 77.6E, ~ 4080 m a.s.l) and Lachung (27.4N, 88.4E, ~ 2700 m a.s.l), elucidates distinct signatures of the sources and types of aerosols prevailing over the western and eastern parts of Himalayas. The mass-mixing ratios of water-soluble (Na+, NH4+, K+, Ca2+, Mg2+, Cl-, SO42-, NO3-, MSA-, C2O42-), carbonaceous (EC, OC, WSOC) and selected elemental (Al, Fe, Cu, Cr, Ti) species depicted significant abundance of mineral dust aerosols (~ 67%), along with a significant contribution of carbonaceous aerosols (~ 9%) during summer to autumn (August-October) over the western Himalayan site. On the other hand, the eastern Himalayan site is found to be dominant of OC (~ 53% in winter) followed by SO42- (as high as 37% in spring) and EC (8-12%) during August to February. However, OC/EC and WSOC/OC ratios showed significantly higher values over both the sites (~ 12.5, and 0.56 at Himansh; ~ 5.7 and ~ 0.74 at Lachung) indicating the secondary formation of organic aerosols via chemical aging over both the sites. The enrichment factors estimated from the concentrations of trace elements over the western Himalayan site revealed the influence of anthropogenic source contribution from the regional hot-spots of Indo-Gangetic Plains, in addition to that of west Asia and the Middle East countries. On the other hand, the source apportionment of aerosols (based on positive matrix factorization - PMF model) over the eastern Himalayas demonstrated the biomass-burning aerosols (25.94%), secondary formation of aerosols via chemical aging (15.94%), vehicular and industrial emissions (20.54%), primary emission sources associated with mineral dust sources (22.28%) and aged secondary aerosols (15.31%) as the major sources of aerosols. Due to abundant anthropogenic source impacts at the eastern Himalayan site, the atmospheric forcing is most elevated in winter (13.4 ± 4.4 Wm-2), which is more than two times the average values seen at the western Himalayan region during the study period. The heavily polluted eastern part of the IGP is a potential anthropogenic source region contributing to the aerosol loading at the eastern Himalayas. These observations have far-reaching implications in view of the role of aerosols on regional radiative balance and their impact on snow/glacier coverage.

How to cite: Bs, A., Gogoi, M., Hegde, P., and Babu, S.: Contrasting signatures of the sources and types of aerosols in the western and eastern Himalayas: Radiative implications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5916,, 2021.

Ilias Fountoulakis, Kyriakoula Papachristopoulou, Emmanouil Proestakis, Antonis Gkikas, Panagiotis Ioannis Raptis, Nikolaos Siomos, Charalampos Kontoes, and Stelios Kazadzis

Aerosols play a key role in radiative transfer processes at the Earth’s atmosphere. The complex interactions between aerosols and solar radiation cannot be easily modeled, and thus, aerosols constitute a major uncertainty factor in radiative transfer simulations. Radiative effects of aerosols depend not only on their physical and chemical properties, but also on their distribution in the atmosphere. Despite the important role of the vertical distribution of aerosols in the atmosphere, default climatological profiles are commonly used in modeling studies. Uncertainties related with the use of default profiles have been roughly analyzed and discussed in the existing bibliography.

In the context of the present study we simulated the downwelling and upwelling irradiance, heating rates, and the actinic flux at different altitudes, from 0 to 8 km, in the atmosphere. Simulations were performed for four different European sites – where aerosol mixtures constitute from quite different aerosol species – using a default climatological aerosol extinction profile, and the seasonally and annually averaged extinction profiles for each site from the LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies (LIVAS). By comparing the results, the effect of using a more representative profile of the aerosol extinction coefficient for each of the sites, instead of a default climatological profile, was estimated. In addition to the aerosol profiles, climatological values of aerosol optical properties and water vapor from the AErosol RObotic NETwork (AERONET), the  version 2 Max-Planck-Institute Aerosol Climatologyand (MACv2), the Modis Dust AeroSol (MIDAS) climatology, and atmospheric and land-surface variables from the Copernicus Atmospheric Monitoring System (CAMS), were used as inputs to the libRadtran radiative transfer model. Spectra in the range 280 – 3000 nm were simulated for different solar zenith angles, and the integrals of the spectra, as well as the integrals in the ultraviolet and visible spectral regions were analyzed.

Results of the analyses are presented and discussed in order to study the sensitivity of the radiometric quantities simulated by the model to the used aerosol extinction profile, for each of the four sites. Differences between the products of the simulations when the used aerosol optical depth (AOD) comes from different sources (LIVAS, AERONET, MIDAS, CAMS) have been also investigated. 


This study was funded by the EuroGEO e-shape (grant agreement No 820852).

How to cite: Fountoulakis, I., Papachristopoulou, K., Proestakis, E., Gkikas, A., Raptis, P. I., Siomos, N., Kontoes, C., and Kazadzis, S.: Effect of aerosol vertical distribution on the transfer of solar radiation through the atmosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6111,, 2021.

LiuDongQing Yang, Xianfeng Wang, and Mikinori Kuwata Kuwata

Brown carbon (BrC) is an important candidate for the direct radiative effects of aerosol particles. It has been demonstrated that positive matrix factorization (PMF) is useful in analyzing Aerosol Mass Spectrometer (AMS) data for BrC source apportionment. However, fragmentation of molecular ions in AMS has been limiting its capability to categorize BrC sources. Soft-ionization mass spectrometric techniques are known to retain molecular information of chemical species. In this study, we applied atmospheric pressure chemical ionization mass spectrometry (APCI-MS) to identify the sources of water-soluble BrC. PM2.5 filter samples were collected at a site in Singapore during March-May of 2019. The extracted water-soluble organic matter (WSOM) was analyzed using APCI-MS, time-of-flight aerosol chemical speciation monitor (ToF-ACSM) and ultraviolet-visible spectrophotometer (UV-Vis). Five factor components were obtained by PMF analysis of the APCI-MS data. The PMF output and UV-Vis data were subsequently used to estimate the absorption Ångstrom exponents (AAE) of WSOM in each component. The estimated values of AAE ranged from 3.95 to 8.71. When comparing the factor contributions with simultaneously monitored gas and aerosol data, we found that the factor with the lowest value of AAE was likely emitted from a methane-rich combustion source, located east of the observation site. 

How to cite: Yang, L., Wang, X., and Kuwata, M. K.: Brown Carbon Sources in Singapore Identified by Factor Analysis of Atmospheric Pressure Chemical Ionization Mass Spectra, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7065,, 2021.

Peng Yao, Haiyan Ni, Norbertas Kairys, Lu Yang, Ru-Jin Huang, Harro A.J. Meijer, and Ulrike Dusek

Isotopic source apportionment is commonly used to gain insight into sources and atmospheric processing of carbonaceous aerosols. Since elemental carbon (EC) is chemically stable, it is possible to apportion the main sources of EC (coal/biomass burning and traffic emissions) using a dual 14C-13C isotope approach. However, dual-isotope source apportionment crucially relies on accurate knowledge of the 13C source signatures, which are seldom measured directly for EC. In this work, we present extensive measurements of organic carbon (OC) and EC 13C signatures for relevant sources in China. The EC 13C source signatures are provided first time using the optical split point in a thermal-optical analyzer to isolate EC, which can greatly reduce the influence of pyrolyzed organic carbon (pOC). A series of sensitivity studies (pOC/EC separation) were conducted to investigate the reliability of our method and its relation to other EC isolation methods. Meanwhile, we summarized and compared the literature 13C signatures in detail of raw source materials, total carbon (TC) and EC using a variety of thermal methods. Finally, we recommend composite EC 13C source signatures with uncertainties and detailed application conditions. There are two points worth noting. First, the traffic 13C signatures of raw materials and EC are separated into three groups according to geographical distribution. Second, the EC 13C signature of C4 plant combustion can be influenced greatly if pOC and EC are not well separated, so the thermal-optical method is necessary. Using these EC 13C source signatures in an exemplary dual-isotope source apportionment study shows improvement in precision. In addition, some interesting distinct and repeatable patterns were discovered in 13C source signatures of semi-volatile, low-volatile, and non-volatile primary OC fractions.

How to cite: Yao, P., Ni, H., Kairys, N., Yang, L., Huang, R.-J., A.J. Meijer, H., and Dusek, U.: 13C signatures of aerosol organic and elemental carbon from major combustion sources in China and worldwide, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15174,, 2021.

Adam Milsom, Adam Squires, Nicholas Terrill, Andrew Ward, and Christian Pfrang

Atmospheric aerosol hygroscopicity and reactivity play a significant role in determining aerosol fate, and are affected by composition and other physical properties. Organic aerosol emissions contain fatty acids, along with sugars such as fructose. As surfactants, fatty acids organise into a range of nanostructures (3-D molecular arrangements), dependent on water content and mixture composition. In this study, we were able to demonstrate (and quantify) that the chemical reactivity of this proxy is dependent on its 3-D molecular arrangement. Furthermore, we have determined the effect of each observed nanostructure on hygroscopicity by measuring the swelling of these nanostructures as a function of relative humidity. We did this by coating capillaries with a fatty acid/sugar as a mixture for an urban aerosol, and following structural changes with simultaneous Small-Angle X-ray Scattering (SAXS) and Raman microscopy, at a synchrotron X-ray source. SAXS measured the nano-structural parameters required to follow both the reaction kinetics (ozonolysis) and hygroscopic swelling of each nanostructure. Raman microscopy provided complementary kinetic information and supported these findings. We found that the molecular arrangement of surfactant material has an impact on both the chemical kinetics and hygroscopicity. This has implications for the persistence of particulate matter in the urban environment and surfactant material in the atmosphere.

How to cite: Milsom, A., Squires, A., Terrill, N., Ward, A., and Pfrang, C.: The hygroscopicity and reactivity of fatty acid atmospheric aerosol proxies are affected by nanostructure , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7326,, 2021.

Battist Utinger

Many large-scale epidemiological studies have shown a close correlation between adverse human health effects and ambient PM2.5 exposure. A report by the World Health Organisation estimates that 1 out of 8 deaths globally are linked to air pollution. Even though various epidemiological studies underline this argument, the chemical components and physical properties of particulate matter that leads to the observed health effects remains highly uncertain.

            Aerosol oxidative potential defined as the capability of particles to produce reactive oxygen species (ROS) with subsequent depletion of anti-oxidants, naturally present in the human lung, has been widely suggested as measure of their potential toxicity. Due to the fact that ROS (i.e. inorganic and organic peroxides and radicals) are highly reactive, they are therefore short-lived. Subsequently, classical offline analysis, where aerosol particles are typically collected on a filter for 24h, may lead to an underestimation of the oxidative potential.

            Therefore, we developed an online instrument that can continuously measure particle oxidative potential with a high time resolution (10 minutes). We further developed an online instrument described in Wragg et al. (2016) and implemented a physiologically relevant assay to assess aerosol oxidative potential, based on the chemistry of ascorbic acid (Campbell et al. (2019)). Ascorbic acid (AA) is a prevalent naturally occurring anti-oxidant present in the lung and can therefore be used as a proxy to measure the oxidative potential of aerosol. 

            In this work, we further developed the AA online assay based on Campbell et al. (2019), implementing more physiologically relevant chemical conditions such as pH7 and we improved components of the instrument to increase its detection limit. With the current instrument AA oxidation can be quantified via two different spectroscopic methods: one based on fluorescence as described in Campbell et al. (2019) and a newly developed UV-absorption detection system using a liquid waveguide capillary cell (LWCC) which is a very sensitive long pathway (100cm) absorption cell.

            For the fluorescence approach, a limit of detection (LOD) of 0.22 µg/m3 was determined for copper (Campbell et al. (2019)). In comparison, the current detection limit for the UV-absorption based setup is an order of magnitude lower (0.02 µg Cu/m3). This LOD is close to observations of copper concentrations at urban European locations, which are in the range of 0.001-0.009 µg/m3. Using both detection methods, we gain an improved understanding of the oxidation process, because the absorbance method measures AA depletion whereas in the fluorescence method the formation of the AA oxidation product dehydroascorbic is quantified. The online ascorbic acid assay as described will be applied in lab experiments (i.e. flow tubes or smog chamber) as well as for field measurements.

With the improvements of having a more physiological relevant assay and an improved detection method, this instrument is capable of providing a real-time and more realistic estimation of the oxidizing aerosol properties and their potential effect on human health compared to traditional offline methods.




Wragg, F. P. H. et al. (2016), Atmospheric Measurement
         Techniques, 9(10), pp. 4891–4900.

 Campbell, S. J. et al. (2019), Analytical Chemistry, 91, 20, 13088-13095.

How to cite: Utinger, B.: Developing a High Time-Resolution Online Instrument to Quantify Aerosol Oxidative Potential via Ascorbic Acid Oxidation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7482,, 2021.

Florian Ungeheuer, Diana Rose, Dominik van Pinxteren, Florian Ditas, Stefan Jacobi, and Alexander L. Vogel

We present the results from a chemical characterization study of ultrafine particles (UFP), collected nearby Frankfurt International Airport where particle size distribution measurements showed high number concentrations for particles with a diameter <50 nm. Aluminium filter samples were collected at an air quality monitoring station in a distance of 4 km to Frankfurt airport, using the 13-stage cascade impactor Nano-MOUDI (MSP Model-115). The chemical characterization of the ultrafine particles in the size range of 0.010-0.018 μm, 0.018-0.032 μm and 0.032-0.056 μm was accomplished by the development of an optimized filter extraction method. An UHPLC method for chromatographic separation of homologous series of hydrophobic and high molecular weight organic compounds, followed by heated electrospray ionization (ESI) and mass analysis using an Orbitrap high-resolution mass spectrometer was developed. Using a non-target screening, ~200 compounds were detected in the positive ionization mode after filtering, in order to ensure high quality of the obtained data. We determined the molecular formula of positively charged adducts ([M+H]+; [M+Na]+), and for each impaction stage we present molecular fingerprints (Molecular weight vs Retention time, Kroll-diagram, Van-Krevelen-diagram, Kendrick mass defect plot) in order to visualize the complex chemical composition. The negative ionization mode led only to the detection of a few compounds (<20) for which reason the particle characterization focuses on the positive ionization mode. We found that the majority of detected compounds belong to homologous series of two different kinds of organic esters, which are base stocks of aircraft lubrication oils. In reference to five different jet engine lubrication oils of various manufacturers, we identified the corresponding lubricant base stocks and their additives in the ultrafine particles by the use of matching retention time, exact mass and MS/MS fragmentation pattern of single organic molecules. As the relevance of the chemical composition of UFP regarding human health is depending on the mass contribution of each compound we strived for quantification of the jet engine oil compounds. This was achieved by standard addition of purchased original standards to the native sample extracts. Two amines serving as stabilizers, one organophosphate used as an anti-wear agent/metal deactivator and two ester base stocks were quantified. Quantification of the two homologous ester series was carried out using one ester compound and cross-calibration. The quantitative determination is burdened by the uncertainty regarding sampling artefacts in the Nano-MOUDI. Therefore we characterized the cascade impactor in a lab experiment using the ester standard. Particle size distribution measurements conducted parallel to the filter sampling enables the determination of jet engine oil contribution to the UFP mass. Results indicate that aircraft emissions strongly influence the mass balance of 0.010-0.018 μm particles. This contribution decreases for bigger sized particles (0.018-0.056 μm) as presumably more sources get involved. The hereby-introduced method allows the qualitative and quantitative assignment of aircraft emissions towards the chemical composition and total mass of airport related ultrafine particles.

How to cite: Ungeheuer, F., Rose, D., van Pinxteren, D., Ditas, F., Jacobi, S., and Vogel, A. L.: Qualitative and Quantitative Characterization of Airport-related Ultrafine Particles using Liquid Chromatography – High-Resolution Mass Spectrometry (UHPLC/HRMS), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7777,, 2021.

Spiro Jorga, Kalliopi Florou, Christos Kaltsonoudis, John Kodros, Christina Vasilakopoulou, Athanasios Nenes, and Spyros Pandis

Biomass burning including residential heating, agricultural fires, prescribed burning, and wildfires is a major source of gaseous and particulate pollutants in the atmosphere. Although, important changes in the size distributions and the chemical composition of the biomass burning aerosol during daytime chemistry have been observed, the corresponding changes at nighttime or in winter where photochemistry is slow, have received relatively little attention. In this study, we tested the hypothesis that nightime chemistry in biomass burning plumes can be rapid in urban areas using a dual smog chamber system.


Ambient urban air during winter nighttime periods with high concentrations of ambient biomass burning organic aerosol is used as the starting point. Ozone was added in the perturbed chamber to simulate mixing with background air (and subsequent NO3 production and aging) while the second chamber was used as a reference. Following the injection of ozone rapid organic aerosol (OA) formation was observed in all experiments leading to increases of the OA concentration by 20-70%. The oxygen to carbon ratio of the OA increased by 50% on average and the mass spectra of the produced OA was quite similar to that of the oxidized OA mass spectra reported during winter in urban areas. Good correlation was also observed with the produced mass spectra from nocturnal aging of laboratory biomass burning emissions showing the strong contribution of biomass burning emissions in the SOA formation during cold nights with high biomass burning activities. Concentrations of NO3 radicals as high as 25 ppt were measured in the perturbed chamber with an accompanying production of 0.2-1.2 μg m-3 of organic nitrate. These results strongly indicate that the OA in biomass burning plumes can evolve rapidly even during wintertime periods with low photochemical activity.

How to cite: Jorga, S., Florou, K., Kaltsonoudis, C., Kodros, J., Vasilakopoulou, C., Nenes, A., and Pandis, S.: Night-time chemistry of biomass burning plumes in urban areas: A dual mobile chamber study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8469,, 2021.

Sonia Afsana, Yuzo Miyazaki, Eri Tachibana, Dhananjay Kumar Deshmukh, Kimitaka Kawamura, and Michihiro Mochida

Organic aerosol (OA), a major component of atmospheric aerosol, is considered to be one of the key players in atmospheric radiative balance and climate change. Chromophoric OA, termed as brown carbon (BrC), is a component that can absorb solar radiation in the ultraviolet and short-wavelength visible regions and is composed of a wide range of poorly characterized compounds. Whereas light absorption properties were analyzed to characterize chromophoric OA, fluorescent properties also provide information on them. In this study, the fluorescence property of solvent extractable organics in submicron aerosol particles collected in a forest in the cool-temperate zone of northern Japan, was characterized.

Aerosol samples were collected on quartz filters (cut-off diameter: ≤0.95 micrometer) in Tomakomai Experimental Forest of Hokkaido University. Organic aerosol components in the samples were extracted and fractionated on the basis of their polarity by the combination of solvent extraction and solid-phase extraction methods. Water-soluble organic matter (WSOM) and water-insoluble organic matter (WISOM) were extracted sequentially by using multiple solvents. Two fractions, humic-like substance (HULIS) and highly-polar water-soluble organic matter (HP-WSOM), were fractionated from WSOM by solid phase extraction. The excitation−emission matrices (EEMs) were measured using a fluorescence spectrometer, and the fluorescence property of the extracts was characterized by the classification of EEM profiles using a Parallel Factor (PARAFAC) model.

From the PARAFAC analysis, five types of fluorescent components were identified for each of WSOM and WISOM fractions. A fluorescence component with the characteristics reported to be associated with (HULIS) accounted for large fractions of the fluorescence from WSOM and WISOM (mean: 68% and 84%, respectively). The relative contribution of the fluorescent components for WSOM shows a clear seasonal variation of the characteristics of WSOM. Furthermore, from each of HULIS and HP-WSOM fractions, five types of fluorescent components were identified. Fluorescence components with the characteristics of protein-like compounds identified in previous EEM studies accounted for a large fraction of the fluorescence from HP-WSOM (mean: 53%), whereas the contribution of protein-like compounds was smaller in the case of the HULIS fraction (mean: 23%).

How to cite: Afsana, S., Miyazaki, Y., Tachibana, E., Deshmukh, D. K., Kawamura, K., and Mochida, M.: Fluorescence property of solvent extractable organic aerosol in a cold-temperate forest area of Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16217,, 2021.

Pradeep Attri, Siddhartha Sarkar, and Devleena Mani

An improved air quality around the globe and over India has been witnessed during the Covid-19 pandemic lockdown. Using surface observations of particulate matter and chemical species data and products from the MERRA-2 reanalysis Ångstrom exponent (α) and aerosol optical depth (AOD), this study documents the changes in atmospheric chemistry over the Indian subcontinent as a result of nationwide lockdown. Two major cities are selected in five Indian regions to cover a large spatial domain. A general shift from fine to coarse particle size, predominantly of dust type, in all regions is observed, which implies a lowered residence time of aerosol in the atmosphere during decreased anthropogenic emissions. For the studied period, Thiruvananthapuram is the cleanest city with marine origin aerosols and an average PM2.5 concentration of 7.69±2.40µg/m3 in the last phase of nationwide lockdown. Over Delhi and Ahmedabad, industrial and vehicular emission play important role in influencing the air quality. The diurnal variation of O3 and NO2 and their interdependency on each other vary over space and time, with the sharp nighttime O3 peak observed in the southern region for each lockdown phase. Biomass burning type aerosols decrease over the eastern region. In lockdown, NO2 also shows a significant correlation with population density (R2 = 0.75; p < 0.05), suggesting human mobility (and accordingly vehicular emissions) as the major contributor to NO2 concentration in the atmosphere. The results of present study did not find any relationship between the ambient concentrations of pollutants to the cumulative increase in COVID-19 cases. However, there is a significant relationship with O3 concentrations, and in turn with NO2, which can be associated with respiratory ailments.

How to cite: Attri, P., Sarkar, S., and Mani, D.: Classification and transformation of aerosols over selected Indian cities during reduced emissions under COVID-19 lockdown, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8677,, 2021.

Magdalena Vallon, Linyu Gao, Junwei Song, Feng Jiang, and Harald Saathoff

The chemical composition of aerosols, in both gas and particle phase, is an important factor regarding their properties influencing air quality, weather, climate, and human health. Organic compounds are a major fraction of atmospheric aerosols and their composition depends on chemical processing by atmospheric oxidants and photochemical reactions. These processes are complex due to the abundance of potential reactions and rarely studied over a wider range of atmospheric temperatures. To achieve a better understanding of three different photochemical processes relevant for the atmosphere as well as the capabilities to investigate such processes in our simulation chamber we studied three different organic aerosol systems between 213 K and 293 K in the AIDA simulation chamber at the Karlsruhe Institute of Technology.  With the first system we studied the direct photolysis of 2,3-pentanedion which is a typical carbonyl compound emitted by the food industry but also by trees. In the second system we studied the depletion of pinic and pinonic acid by radicals formed through photolysis of an iron oxalate complex, which acts as the photosensitizer in this system, all present in aqueous aerosol particles. Furthermore, we studied the photolysis of a nitrogen heterocycle in aerosol particles, which can form in the atmosphere by the reaction of dicarbonyls and shows strong absorption in the visible [1].

Photochemical reactions were studied using a new LED light-source simulating solar radiation in the UV and visible. The organic aerosols were generated by nebulizing aqueous solutions containing the aerosol components.  The aerosols were analysed by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), a proton transfer mass spectrometer (CHARON-PTRMS) and a high–resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-HR-ToF-CIMS).  The latter two allow to study the composition of gas phase and particle phase separately.

In this presentation, we will discuss the changes that these organic compounds undergo in gas and particle phase, during photochemical aging at temperatures between 213 and 293 K.


[1] C. J. Kampf, A. Filippi, C. Zuth, T. Hoffmann and T. Opatz, Secondary brown carbon formation via the dicarbonyl imine pathway: nitrogen heterocycle formation and synergistic effects, Phys. Chem. Chem. Phys, 2016, 18, 18353

How to cite: Vallon, M., Gao, L., Song, J., Jiang, F., and Saathoff, H.: Direct and indirect photochemical aging of organic aerosol components as a function of temperature, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8722,, 2021.

Hamid Omidvarborna and Prashant Kumar

The majority of people spend most of their time indoors, where they are exposed to indoor air pollutants. Indoor air pollution is ranked among the top ten largest global burden of a disease risk factor as well as the top five environmental public health risks, which could result in mortality and morbidity worldwide. The spent time in indoor environments has been recently elevated due to coronavirus disease 2019 (COVID-19) outbreak when the public are advised to stay in their place for longer hours per day to protect lives. This opens an opportunity to low-cost air pollution sensors in the real-time Spatio-temporal mapping of IAQ and monitors their concentration/exposure levels indoors. However, the optimum selection of low-cost sensors (LCSs) for certain indoor application is challenging due to diversity in the air pollution sensing device technologies. Making affordable sensing units composed of individual sensors capable of measuring indoor environmental parameters and pollutant concentration for indoor applications requires a diverse scientific and engineering knowledge, which is not yet established. The study aims to gather all these methodologies and technologies in one place, where it allows transforming typical homes into smart homes by specifically focusing on IAQ. This approach addresses the following questions: 1) which and what sensors are suitable for indoor networked application by considering their specifications and limitation, 2) where to deploy sensors to better capture Spatio-temporal mapping of indoor air pollutants, while the operation is optimum, 3) how to treat the collected data from the sensor network and make them ready for the subsequent analysis and 4) how to feed data to prediction models, and which models are best suited for indoors.

How to cite: Omidvarborna, H. and Kumar, P.: How low-cost air pollution sensors could make homes smarter?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9113,, 2021.

Petra Pokorná, Naděžda Zíková, Radek Lhotka, Petr Vodička, Jean-Eudes Petit, Saliou Mbengue, Adéla Holubová Šmejkalová, Jakub Ondráček, Jaroslav Schwarz, and Vladimír Ždímal

This work aims to assess the summer PM1 based on particle size distribution, density and origin. An intensive sampling campaign was conducted in July 2019 at the National Atmospheric Observatory Košetice (NAOK) in the Czech Republic.

5-min integrals of particle number concentration (PNC) and particle number size distribution (PNSD) data were recorded by a Scanning Mobility Particle Sizer (size range 10 – 800 nm, SMPS, IFT TROPOS, Leipzig, with CPC 3772, TSI USA) and size-resolved PM chemical composition was measured by a Compact Time of Flight Aerosol Mass Spectrometer (C-ToF-AMS, Aerodyne, USA). 1-min PM1 black carbon (BC) concentrations by aethalometer (AE33, Magee Scientific, USA) and 4-h PM2.5 organic and elemental carbon (OC/EC) concentrations (Sunset Laboratory Inc., USA) were measured.  Also 12-h PM1 samples by a sequential Leckel LVS-3 (Sven Leckel Ingenieurbüro, Germany) for a subsequent chemical analysis (water-soluble ions, monosaccharides, anhydrides, and saccharides) were collected. Additionally, 10-min average SO2, NO2, NOx and CO concentrations along with the values of meteorological parameters were recorded. To determine the origin of non-refractory PM1 (NR-PM1) species (Org, NO3-, SO42-, NH4+) the back trajectories describing the air mass origin were clustered using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model [1]. Last, but not least, the multi-time factor analysis model [2] with modifications was applied on combined dataset (on-line and off-line measurements) to refine the analysis results with respect to the organic aerosol factors as well as organic aerosol sources and their origin.

The campaigns was characterized by prevailing westerly winds with average wind speed of 3.0±1.5 m s-1, average temperature of 18.5±4.7 °C and negligible precipitation. The average PM1 (NR-PM1 and eBC) measured concentration was 8.5±3.5 µg m-3 (12h PM1 10.1±6.4 µg m-3). Based on the PNC predominated particles in the size range 25 – 80 nm (N25 – 50 and N50 – 80), also called the Aitken mode, typical for rural background stations and originates from the aging of the particles generated during new particle formation events [3]. NR-PM1 was composed primarily by organics (58%) and sulphate (22%) in the accumulation mode (Org mode diameter 300 nm and SO42- mode diameter 385 nm) with average particle density ~ 1.4 g m-3. This result in combination with the cluster analysis points to the regional origin of the particles from southeast (Austria-Hungary-Slovakia). Six Org factors (primary organic aerosol (POA) – fungal origin, biomass burning organic aerosol (BBOA) – related secondary aerosol (SA), semivolatile aerosol – nitrate-rich, secondary organic aerosol (SOA) – oxalate-rich, semivolatile aerosol – microbial origin, primary traffic and biomass organic aerosol (OA)) based on combined data were resolved by multi-time factor analysis model. Modelling of combined dataset provided insides into processes involved in SOA formation and sources.


[1] Rolph, G., et al., (2017) Environ. Modell. Software 95, 210–228.

[2] Zhou, L., et al., (2004) Atmos. Environ. 38, 4909–4920.

[3] Costabile, F., et al., (2009) Atmos. Chem. Phys. 9, 3163–3195.


This work was supported by the GACR under grant P209/19/06110Y and by the MEYS of the Czech Republic under grant ACTRIS-CZ LM2018122 and ACTRIS-CZ RI (CZ.02.1.01/0.0/0.0/16_013/0001315).

How to cite: Pokorná, P., Zíková, N., Lhotka, R., Vodička, P., Petit, J.-E., Mbengue, S., Holubová Šmejkalová, A., Ondráček, J., Schwarz, J., and Ždímal, V.: Summer PM1 measured at a rural background site in Central Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10166,, 2021.

Georgios Gkatzelis, Jessica Gilman, Steven Brown, Henk Eskes, Rita Gomes, Anne Lange, Brian McDonald, Jeff Peischl, Andreas Petzold, Chelsea Thompson, and Astrid Kiendler-Scharr

The coronavirus-19 (COVID-19) pandemic led to government interventions to limit the spread of the disease that are unprecedented in the last decades. Stay at home orders and other measures led to sudden decreases in atmospheric emissions, most visibly from the transportation sector. We present a review of the current knowledge and understanding of the influence of these emission reductions on atmospheric pollutants concentration and notably air quality with a focus on NO2, PM2.5, and O3 based on more than 200 papers utilizing observations from ground-based and satellite remote sensing instruments. We use the government stringency index as an indicator for the severity of lockdown measures and show how key air pollutants change as the stringency index increases. Changes in NO2 and PM2.5 mass concentration are well-studied globally. The observed decrease of NO2 with increasing stringency index is in general agreement with emission inventories that account for the lockdown. Due to the important influence of atmospheric chemistry on O3 and PM2.5 concentrations, their responses may not be linear with respect to primary pollutants. At most sites, we found O3 increased, whereas PM2.5 decreased slightly, with increasing stringency index. Changes in the PM2.5 composition are found to be understudied and not well-quantified so far. We highlight future research needs for utilizing the emerging data sets covering a full seasonal cycle as a preview of a future state of the atmosphere in a world with targeted permanent reductions of emissions. Finally, we emphasize the need to account for the effects of meteorology, long-term trends, and atmospheric chemistry when determining the lockdown effects on pollutant concentrations, especially on PM2.5.

How to cite: Gkatzelis, G., Gilman, J., Brown, S., Eskes, H., Gomes, R., Lange, A., McDonald, B., Peischl, J., Petzold, A., Thompson, C., and Kiendler-Scharr, A.: The Global Impacts of COVID-19 Lockdowns on Short-Lived Climate Forcers: Highlights from a Critical Review, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10636,, 2021.

Aleksei Poliukhov, Blinov Denis, Chubarova Natalia, and Shatunova Marina

Our report provides an examination of aerosol climatologies and their impact on the weather forecast accuracy. We used non-hydrostatiс mesoscale COSMO-Ru model with Tanre (Tanre et al., 1984), Tegen (Tegen et al., 1997), MACv2 (Kinne S, 2019) and CAMS (Flemming, et al., 2017) aerosol climatologies for the central months of the season for the territory of Eurasia in 2017. We estimated the forecast accuracy for the surface air temperature, the temperature at 850 hPa and 500 hPa. It is found that the change in the calculation of surface air temperature over land can reach one degree when using Tegen and MACv2 compared to Tanre. Changes don’t exceed 0.4 degrees at altitudes of 850 and 500 hPa. Also, we presented the comparison results for total radiation with measurements on the Meteorological Observatory of Moscow State University and Tiksi (Russia), Eilat (Israel) and Lindenberg (Germany) Observatories. It is shown that when using aerosol climatology, the deviation of calculations from the measurement data does not exceed 25 W/m2 (Poliukhov et al., 2019).


The reported study was funded by RFBR, project number 19-35-90129.


Flemming, J., Benedetti, A., Inness, A., Engelen, R. J., Jones, L., Huijnen, V., ... & Peuch, V. H. (2017). The CAMS interim reanalysis of carbon monoxide, ozone and aerosol for 2003–2015, Atmospheric Chemistry and Physics, 17 (3), 1945 - 1983.

Kinne S. (2019), The MACv2 aerosol climatology, Tellus B: Chemical and Physical Meteorology. 71(1), 1-21.

Poliukhov, A. A., Chubarova, N. E., Blinov, D. V., Tarasova, T. A., Makshtas, A. P., & Muskatel, H. (2019). Radiation Effects of Different Types of Aerosol in Eurasia According to Observations and Model Calculations. Russian Meteorology and Hydrology, 44(9), 579-587.

Tanre D., Geleyn J. F., Slingo J. (1984), First results of the introduction of an advanced aerosol-radiation interaction in the ECMWF low-resolution global model, Aerosols and their climatic, 133-177.

Tegen I. et al. (1997), Contribution of different aerosol species to the global aerosol extinction optical thickness: Estimates from model results, Journal of Geophysical Research: Atmospheres. 102(20), 23895-23915.

How to cite: Poliukhov, A., Denis, B., Natalia, C., and Marina, S.: Assessment of the influence of aerosol climatology on the forecast of the air temperature., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10667,, 2021.

Christos Kaltsonoudis, Kalliopi Florou, John Kodros, Spiro Jorga, Christina Vasilakopoulou, Charalampia Baliaka, Andreas Aktypis, Athanasios Nenes, and Spyros Pandis

Τhe composition of wintertime urban air in Patras, Greece was investigated during early 2020 focusing on the role of biomass burning. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a Proton Transfer-Reaction Mass Spectrometer (PTR-MS) were deployed. Additionally continuous measurements of the aerosol size distribution from 10 nm to 10 μm were performed, as well as measurements of the size-resolved aerosol composition using a Micro-Orifice Uniform-Deposit Impactor, black carbon (BC) concentrations using an SP2, aerosol absorption, brown carbon concentrations, and reactive oxygen species (ROS). A number of low-cost sensors for particles and vapors was also deployed in the city.

               The PM2.5 concentration peaked during the early evening reaching up to 150 µg m-3. PM1 aerosol (23 µg m-3 on average) was mainly composed of organics (69%) with the rest being BC (11%), sulphate (10%), nitrate (5%), ammonium (4%) and chloride (1%). Positive Matrix Factorization (PMF) of the measurements of the AMS indicated that biomass burning due to residential heating was the dominant source of PM1 during the campaign accounting for 53% of the total OA with the rest being the oxygenated organic aerosol (ΟΟΑ) at 25%, the cooking OA (COA) at 12% and the traffic related hydrocarbon-like OA (HOA) at 10%.

               The biomass burning contribution was also evident in several volatile organic compounds (VOCs) detected by the PTR-MS. Biogenic species such as isoprene and the monoterpenes showed clear relation to wood burning, while most of the aromatic compounds were related both to traffic and wood burning. The latter was also true for other gas species measured such as CO, NOx etc. Biomass burning was also a major contributor to the ROS measured as well as the brown carbon.

How to cite: Kaltsonoudis, C., Florou, K., Kodros, J., Jorga, S., Vasilakopoulou, C., Baliaka, C., Aktypis, A., Nenes, A., and Pandis, S.: Contribution of residential wood burning to wintertime air pollution in an urban area, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10670,, 2021.

Sophie Bogler, Nadine Borduas-Dedekind, Imad el Haddad, David Bell, and Kaspar Dällenbach

Singlet oxygen (1O2) is a reactive oxygen species that has recently gained attention as a competitive oxidant in the atmosphere. This excited state of molecular oxygen is formed by indirect photochemistry in the presence of chromophoric dissolved organic matter (DOM) as sensitizers, molecular oxygen and sunlight. The produced highly reactive intermediate 1O2 is then capable of oxidizing and degrading many organic atmospheric components, thereby affecting their lifetime in the atmosphere. Despite this influence on atmospheric fate, the spatiotemporal distribution of 1O2 in particular matter (PM) is currently unknown. We hypothesized that brown carbon in biomass burning organic aerosols emitted during winter in Switzerland would lead to higher 1O2 steady-state concentrations in PM compared to summer. Therefore, to advance atmospheric 1O2 research, we investigated the 1O2 sensitizing ability of organic aerosols sampled on 24-hour PM10 filters. Specifically, these filters were collected throughout 2013 in Frauenfeld and San Vittore in Switzerland, characterized as urban background and rural traffic measurement stations, respectively. We extracted the water-soluble organic components and quantified 1O2 steady state concentrations as well as 1O2 quantum yield. The quantum yield enhances the data intercomparison as this value shows the normalization of 1O2 production as a function of the rate of absorbance of the organic aerosols. In our ongoing efforts of expanding the spatiotemporal scale of our measurements, our results from Frauenfeld so far show a range between 0.38 – 6.05 · 10-13 M for 1O2 steady state concentrations and quantum yields up to 2.1± 0.5%. In preliminary experiments, samples from the rural site San Vittore show similar values, with potentially higher values during periods of significant biomass burning contributions. The values underline 1O2’spotential importance for atmospheric processing, e.g. comparing to Manfrin et al. (ES&T, 2019)1 who reported 1O2 steady state concentrations of 3 ± 1 · 10-14 M from secondary organic aerosols extracts. More importantly, the filter extracts analyzed thus far show a strong seasonal trend, with increased 1O2 values and higher variability in winter as compared to summer. This result corroborates the hypothesis that there is more chromophoric DOM present in winter, due to a higher fraction of brown carbon emitted e.g. in biomass burning for residential heating. To extend this analysis, we are currently correlating the results for 1O2 with molecular markers based on mass spectrometry data available from previous filter analysis provided by Daellenbach et al., (ACP, 2017)2. Finding these correlations will enable the prediction of 1O2 sensitizing abilities of organic material present in the aerosols both qualitatively and quantitatively. In all, our work will help constrain the seasonal relevance of 1O2 photochemistry in the atmosphere.


1. Manfrin, A. et al. Reactive Oxygen Species Production from Secondary Organic Aerosols: The Importance of Singlet Oxygen. Environmental Science & Technology 53, 8553–8562 (2019).
2. Daellenbach, K. R. et al. Long-term chemical analysis and organic aerosol source apportionment at nine sites in central Europe: source identification and uncertainty assessment. Atmospheric Chemistry and Physics 17, 13265–13282 (2017).

How to cite: Bogler, S., Borduas-Dedekind, N., el Haddad, I., Bell, D., and Dällenbach, K.: How quality and quantity of brown carbon influence singlet oxygen production in aqueous organic aerosols, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10743,, 2021.

Ramiro Checa-Garcia, Didier Didier Hauglustaine, Yves Balkanski, and Paola Formenti

Glyoxal (GL) and methylglyoxal (MGL) are the smallest di-carbonyls present in the atmosphere. They hydrate easily, a process that is followed by an oligomerisation. As a consequence, it is considered that they participate actively in the formation of secondary organic aerosols (SOA) and therefore, they are being introduced in the current climate models with interactive chemistry to assess their importance on atmospheric chemistry. In our study we present the introduction of glyoxal in the INCA global model. A new closed set of gas-phase  reactions is analysed first with a box model. Then the simulated global distribution of glyoxal by the global climate model is compared with satellite observations. We show that the oxidation of volatile organic compounds and acetylene, together with the photolysis of more complex di-carbonyls allows us to reproduce well glyoxal seasonal cycle in the tropics but it requires an additional sink in several northern hemispheric regions. Additional sensitivity studies are being conducted by introducing  GL and MGL interactions with dust and SOA according to new uptake  coefficients obtained by dedicated experiments in the CESAM instrument (Chamber of Experimental Simulation of Atmospheric Multiphases). The effects of these heterogeneous chemistry processes will be quantified in the light of the new chamber measurements  and also evaluated in terms of optical properties of aged dust aerosol  and the changes in direct radiative effects  of the involved aerosol species.

How to cite: Checa-Garcia, R., Didier Hauglustaine, D., Balkanski, Y., and Formenti, P.: Impact of heterogeneous chemistry on the distribution of Glyoxal and Methylglyoxal in the troposphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10780,, 2021.

feng jiang, Harald Saathoff, junwei song, linyu gao, magdalena vallon, thomas leisner, and stefan norra

Brown carbon (BrC) aerosol has significant climatic impact due to its ability to absorb solar radiation in the near-ultraviolet and visible spectral range. However, chromophores responsible for light absorption in atmospheric aerosol particles are not well understood in urban areas. Therefore, optical properties and chromophore composition of brown carbon were characterized during March 2020 in downtown Karlsruhe, a city of 300000 inhabitants in southwest Germany.

In this study, total non-refractory particle mass was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-MS; hereafter AMS). Furthermore, Aerosol particles were collected on filters and analyzed in the laboratory. Filter samples were extracted by methanol and the corresponding solutions were analyzed by excitation-emission spectroscopy (AquaLog), resulting in characteristic light absorption and fluorescence spectra. Furthermore, filters were analyzed by a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-HR-TOF-CIMS; hereafter CIMS) employing iodide ions, which results in the molecular composition of oxygenated organic aerosol compounds.

Our results show that the average light absorption and mass absorption efficiency of brown carbon at 365 nm were (2.8±1.9) Mm-1 and (1.1±0.2) m2 g-1 respectively. Parallel factor (PARAFAC) analysis allowed for identification of four types of fluorescence in methanol-soluble organic compounds. HULIS-like compounds contributed 47%, road dust-like compounds 19%, biomass burning-like compounds 25%, and protein-like compounds 9%. Positive matrix factorization (PMF) analysis of organic detected by AMS led to five characteristic organic compound classes. Of these five classes, the biomass burning organic aerosol showed a correlation coefficient of r2=0.7 with the biomass burning like factor from the fluorescence analysis. Oxygenated organic aerosol components had potentially lower fluorescence intensity and mass absorption coefficiency. Furthermore, five nitroaromatic compounds were identified by CIMS (C7H7O3N, C7H7O4N, C6H5O5N, C6H5O4N, and C6H5O3N) which contributed 0.2%-0.9% to total organic mass, but can explain 3%-6% of the absorption at 365 nm.

How to cite: jiang, F., Saathoff, H., song, J., gao, L., vallon, M., leisner, T., and norra, S.: Chemical characteristics and optical properties of brown carbon aerosol in Karlsruhe during winter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10899,, 2021.

Yijuan Zhang

China, with rapid urbanization and industrialization, has experienced severe air quality deterioration in recent decades. To release heavy air pollution in China, Chinese government implement the Clean Air Action Plan initiated in 2013. Fine particles (PM2.5) concentrations have shown significant declines over the nationwide, which attribute to mitigating anthropogenic emission of primary PM2.5, and precursor gases of nitrogen oxides (NOx), sulfur dioxide (SO2), and carbon monoxide (CO). However, surface ozone concentrations have unexpectedly increased during the implementation of 2013 to 2019. China has an average trend of 1.9 ppbv a-1 in same period, measured by ambient monitoring station of China’s Ministry of Environment and Ecology (China MEE). Notably, surface ozone has faster increased trend in megacity clusters, with 3.3 ppbv a-1 inBeijing-Tianjin-Hebei, 1.6 ppbv a-1 in Yangtze River Delta, 1.1 ppbv a-1 in Pearl River Delta. At shorter temporal scale, the lockdown during outbreak of COVID-19, in which human activities dramatically decreased with reduction of industry and transport emission, witnessed exceeding 30% increase of maximum daily 8h average (MDA8) O3, in major cities (e.g., Shanghai, Hangzhou, Hefei etc.). The investigated results suggested simultaneous controlling concentration of PM2.5 and ozone should coordinate inner physical and chemical processes. In this study, the weather Research and Forecasting with Chemistry was applied to reproduce the following two pathways: (1) The response of surface ozone to modification of photolysis by changed radiation budgets induced by scattering and absorbing aerosols; (2) The further impacts of altered atmospheric oxidizing capacity on surface ozone and aerosols concentrations. This study can provide reasonable advice to air pollution control strategies in Chinese megacity clusters.

How to cite: Zhang, Y.: The response of surface ozone to current mitigation strategies for reducing air pollution in Chinese megacity clusters, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14102,, 2021.

Haiyan Ni, Ru-Jin Huang, and Ulrike Dusek

To mitigate haze pollution in China, a better understanding of the sources of carbonaceous aerosols is required due to the complexity in multiple emissions and atmospheric processes. Here we combined the analysis of radiocarbon and the stable isotope 13C to investigate the sources and formation of carbonaceous aerosols collected in two Chinese megacities (Beijing and Xi’an) during severe haze events of “red alarm” level from December 2016 to January 2017. The haze periods with daily PM2.5 concentrations as high as ~400 µg m-3 were compared to subsequent clean periods (i.e., PM2.5 < median concentrations during the winter 2016/2017), with PM2.5 concentrationsbelow 100 µg m-3 in Xi’an and below 20 µg m-3 in Beijing. In Xi’an, liquid fossil fuel combustion was the dominant source of elemental carbon (EC; 44%–57%), followed by biomass burning (25%–29%) and coal combustion (17%–29%). In Beijing, coal combustion contributed 45%–61% of EC and biomass burning (17%–24%) and liquid fossil fuel combustion (22%–33%) contributed less. Non-fossil sources contributed 51%–56% of organic carbon (OC) in Xi’an and fossil sources contributed 63%–69% of OC in Beijing. Secondary OC (SOC) was largely contributed by non-fossil sources in Xi’an (56 ± 6%) and by fossil sources in Beijing (75 ± 10%), especially during haze periods. The fossil vs. non-fossil contributions to OC and EC did not change drastically during haze events in both Xi’an and Beijing. However, compared to clean periods, the contribution of coal combustion to EC during haze periods increased in Xi’an and decreased in Beijing. During clean periods, primary OC from biomass burning and fossil sources constituted ~70% of OC in Xi’an and ~53% of OC in Beijing. From clean to haze periods, the contribution of SOC to total OC increased in Xi’an, but decreased in Beijing, suggesting that contribution of secondary organic aerosol formation to increased OC during haze periods was more efficient in Xi’an than in Beijing. In Beijing, the high SOC fraction in total OC during clean periods was mainly due to elevated contribution from non-fossil SOC. In Xi’an, a slight day-night difference was observed during the clean period, with enhanced fossil contributions to OC and EC during the day. This day-night difference was negligible during severe haze periods, likely due to enhanced accumulation of pollutants under stagnant weather conditions.

How to cite: Ni, H., Huang, R.-J., and Dusek, U.: Dual-carbon isotopic characterization of carbonaceous aerosol reveals different primary and secondary sources in Beijing and Xi’an during severe haze events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12901,, 2021.

Ruichen Zhou, Yange Deng, Bhagawati Kunwar, Qingcai Chen, Jing Chen, Lujie Ren, Petr Vodicka, Dhananjay Deshmukh, Pingqing Fu, Kimitaka Kawamura, and Michihiro Mochida

Atmospheric aerosol affects the Earth’s radiation budget by directly scattering and absorbing solar radiation and indirectly acting as cloud condensation nuclei. Both of the effects are responsible for the uncertainties in the prediction of global climate change. A better understanding of the hygroscopicity of the organic aerosol is important because it is poorly characterized to date. In this study, the hygroscopicity of humic-like substances (HULIS), a ubiquitous mixture of water-soluble organic matter, isolated from aerosol samples collected in Beijing in different seasons, was measured using a hygroscopicity tandem differential mobility analyzer (HTDMA). The hygroscopicity parameter of the isolated HULIS fraction (κHULIS) was in the range of 0.03–0.13 (mean: 0.06). Considering the possible influence from small amounts of inorganic salts, the hygroscopicity parameter of pure organic HULIS (κ*HULIS) was found to be slightly lower (0–0.11, mean: 0.04). The κHULIS showed a seasonal variation; the values were highest in summer (0.08), followed by spring (0.06), autumn (0.06), and winter (0.04). The κ*HULIS showed a similar seasonal variation, with the highest and lowest values in summer (0.07) and autumn (0.01), respectively. Both κHULIS and κ*HULIS were correlated positively with the O/C ratio of the HULIS. Comparison of the hygroscopicity parameter values with factors from positive matrix factorization (PMF) analysis of the mass spectra of the HULIS fractions showed that κHULIS correlated positively with more-oxidized oxygenated organic aerosol (MO-OOA) and less-oxidized OOA (LO-OOA), and correlated negatively with cooking-like OA (COA) and biomass burning OA (BBOA). The relationship between the hygroscopicity parameter and sources was further explored based on a multi-liner regression analysis. The variation in the hygroscopicity of HULIS and its connection to sources provide an insight into the contribution of organics to aerosol hygroscopicity, toward a better understanding of its link to climate.

How to cite: Zhou, R., Deng, Y., Kunwar, B., Chen, Q., Chen, J., Ren, L., Vodicka, P., Deshmukh, D., Fu, P., Kawamura, K., and Mochida, M.: Hygroscopicity of HULIS in urban aerosol and its relationship with sources, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11439,, 2021.

Irini Tsiodra, Kalliopi Tavernaraki, Aikaterini Bougiatioti, Georgios Grivas, Maria Apostolaki, Despina Paraskevopoulou, Alexandra Gogou, Konstantinos Parinos, Maria Tsagkaraki, Pavlos Zarmpas, Athanasios Nenes, and Nikolaos Mihalopoulos

Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants with proven mutagenic and carcinogenic potential that originate from incomplete combustion, and partition to fine particulate matter. Nitro-PAHs & oxy-PAHs are oxidation products of PAHs with increased toxicity compared to their parent members and may reveal useful information about the aging and oxidation processes of PAHs.

In this study, we investigate the seasonal profiles of 31 PAHs and select oxidized forms such as nitro PAHs & quinones in Athens, Greece to understand their sources, levels, toxicity and impacts. PAHs levels were found to be significantly higher during winter, particularly during intense pollution episodes, compared to the other seasons. Chemical markers linked to biomass burning (BB) emissions are found to correlate well with the total amount of PAHs (ΣPAHs) during wintertime, strongly indicating that BB emissions are a significant source of PAHs. Positive Matrix Factorization (PMF) analysis showed that more than 50% of ΣPAHs originate from BB emissions and that a “factor” (composed of a specific mixture of PAHs) characterizes biomass burning emissions – and can potentially be used as a tracer. Analysis of the PMF series suggests that BB aerosol is much more carcinogenic than the effects of gasoline and diesel combustion combined. Finally, the exposure impact during winter is 9 times higher compared with the other seasons.


This work has been funded by the European Research Council, CoG-2016 project PyroTRACH (726165) H2020-EU.1.1. – Excellent. We also acknowledge support by the “PANhellenic infrastructure for Atmospheric Composition and climatE change” (MIS 5021516) implemented under the Action “Reinforcement of the Research and Innovation Infrastructure ”, funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).


How to cite: Tsiodra, I., Tavernaraki, K., Bougiatioti, A., Grivas, G., Apostolaki, M., Paraskevopoulou, D., Gogou, A., Parinos, K., Tsagkaraki, M., Zarmpas, P., Nenes, A., and Mihalopoulos, N.: Year-long variability of polycyclic aromatic hydrocarbons (PAHs) and their contribution to winter intense pollution events in the urban environment of Athens, Greece , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11550,, 2021.

Charalampia Baliaka, Christos Kaltsonoudis, Kalliopi Florou, Spiro Jorga, Christina Vasilakopoulou, John Kodros, Andreas Aktypis, Angeliki Matrali, Despina Paraskevopoulou, Mauro Masiol, Spyros Pandis, and Athanasios Nenes

Atmospheric brown carbon (BrC) is a highly uncertain, but potentially important contributor to light absorption in the atmosphere. Laboratory and field studies have shown that BrC can be produced from multiple sources, including primary emissions from fossil fuel combustion and biomass burning (BB), as well as secondary formation through a number of reaction pathways. It is currently thought that the dominant source of atmospheric BrC is primary emissions from BB, but relatively few studies demonstrate this in environments with complex source profiles.

A field campaign was conducted during a month-long wintertime period in 2020 on the campus of the University of Peloponnese in the southwest of Patras, Greece which represents an urban site. During this time, ambient filter samples (a total of 35 filters) were collected from which the water-soluble BrC was determined using a semi-automated system similar to Hecobian et al. (2010),  where absorption was measured over a 1 m path length. To measure the BrC, a UV-Vis Spectrophotometer was coupled to a Liquid Waveguide Capillary Cell and the light absorption intensity was recorded at 365 and 700 nm. The latter was used as a reference wavelength. We found that the average BrC absorption in Patras at a wavelength of 365 nm was 8.5 ± 3.9 Mm-1 suggesting that there was significant BrC in the organic aerosol during this period. Attribution of sources of BrC was done using simultaneous chemical composition data observations (primarily organic carbon, black carbon, and nitrate) combined with Positive Matrix Factorization analysis. This analysis showed that in addition to the important role of biomass burning (a contribution of about 20%) and other combustion emissions (also close to 20%), oxidized organic aerosol (approximately 40%) is also a significant contributor to BrC in the study area.


Hecobian, A., Zhang, X., Zheng, M., Frank, N., Edgerton, E.S., Weber, R.J., 2010. Water-soluble organic aerosol material and the light-absorption characteristics of aqueous extracts measured over the Southeastern United States. Atmos. Chem. Phys. 10, 5965–5977.


How to cite: Baliaka, C., Kaltsonoudis, C., Florou, K., Jorga, S., Vasilakopoulou, C., Kodros, J., Aktypis, A., Matrali, A., Paraskevopoulou, D., Masiol, M., Pandis, S., and Nenes, A.: Sources of water-soluble Brown Carbon at a South-Eastern European Site, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11903,, 2021.

Tuuli Lehmusjärvi, Roseline Thakur, Lisa Beck, Mikko Sipilä, and Tuija Jokinen

In the high Arctic, the climate is warming faster than in the lower latitudes due to the Arctic amplification. Sea ice is melting and permafrost is thawing, and the scarce vegetation of the Arctic is changing rapidly. All these varying conditions will have an impact on possible emission sources of aerosol precursor gases, thus affecting the New Particle Formation (NPF) in the Arctic atmosphere, of which we still know very little. It is important to study the NPF events, which parameters affect the aerosol phase and how these newly formed aerosols can grow into cloud condensation nuclei sizes. Only then, it is possible to understand how climate change is affecting the aerosol population, clouds and regional climate of the pristine Arctic. The role of the precursor gases like Sulphuric Acid (SA), Iodic Acid (IA), Methane Sulphonic Acid (MSA) and Highly Oxygenated organic Molecules (HOM) in NPF in boreal and urban environments has been explored to a great extent. However, the role of these precursor gases in NPF events in remote locations - devoid of pollution sources and the vegetation - is still ambiguous. Therefore, it is crucial to conduct long-term measurements to study the composition and concentrations of aerosol precursors molecules, nanoparticles and air ions in remote and climatically fragile place like Ny-Ålesund in the Arctic. This research location is not only a natural pristine laboratory to understand the atmospheric processes but also acts as a climate mirror reflecting the most drastic changes happening in the atmosphere and cryosphere. In this study, we aim to enhance the understanding of the role of aerosol precursor gases in new particle formation in Ny-Ålesund, Svalbard.

            We have studied aerosol particle formation now for almost three years in the Ny-Ålesund research village in Svalbard (78° 55' 24.7368'' N, 11° 54' 35.6220'' E.) with the Neutral cluster and Air Ion Spectrometer (NAIS) measuring ~1-40 nm particles and ions. We have conducted measurements with a Chemical Ionization Atmospheric Pressure interface Time Of Flight (CI-APi-TOF) mass spectrometer to understand the chemical composition of organic precursors vapours and abundance of inorganic aerosol precursor gases such as SA, MSA and IA. Additionally,  we have studied the emission and composition of volatile organic compounds on the site during summer-time.

            In this study, we report the time series concentrations of the most common aerosol precursor gases like SA, MSA, IA and HOM from the period 28.6.-25.7.2019, which are responsible for the initiation and/or growth of particles. The variability in the concentrations of these vapours is compared between NPF event and non-event days. The study explores also the role of meteorological parameters like wind speed, wind direction, temperature and humidity on NPF processes.

How to cite: Lehmusjärvi, T., Thakur, R., Beck, L., Sipilä, M., and Jokinen, T.: Studies of the connection between condensable trace gases and aerosol particles in Svalbard, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12528,, 2021.

Lunch break
Hector Navarro-Barboza, Vincenzo Obiso, Rubén Sousse, Marco Pandolfi, Carlos Pérez García-Pando, and Oriol Jorba

Atmospheric aerosols have a significant influence on the climate system. On average, aerosols cool the atmosphere directly by scattering solar radiation and indirectly through aerosol–cloud interactions. However, some aerosol components are capable of absorbing visible solar radiation and warming the lower atmosphere. The most prevalent types of absorbing aerosols are black carbon (BC) and mineral dust. Most organic aerosols (OA) can be characterized as "white" because they efficiently scatter visible radiation. Recently, analyses from laboratory and field experiments have provided strong evidence for the existence of some OA with light absorbing properties. In recent scientific literature, the term "brown carbon" (BrC) has emerged to describe this type of OA, characterized by an absorption spectrum that smoothly increases from visible to UV wavelengths. Main sources of primary BrC are biomass burning and residential coal combustion, but recent studies have postulated the existence of various secondary sources of BrC resulting from multi-phase reactions of volatile organic compunds exposed to nitrogen oxides and ammonia.

In this work, we combine different evaluation strategies to constrain the absoprtion of organic aerosols simulated by the Multiscale Online Nonhydrostatic Atmosphere Chemistry (MONARCH) model. The validation of the model focuses mostly on the concentrations and optical properties of BC, OA and BrC. In-situ surface measurements of PM chemical composition (both off-line and on-line) and optical properties (multi-wavelengths scattering and absorption) provided by IDAEA-CSIC and columnar integrated optical properties (optical depth, single scattering albedo and asymmetry factor) derived from the Aerosol Robotic Network (AERONET) are used. We discuss different sensitivity runs at the regional and global scale perturbing (i) the OA/BrC fraction of biomass burning and biofuel emissions, (ii) the refractive index of OA and BrC aerosol components, and (iii) the aging rates of photobleaching and browning processes.

How to cite: Navarro-Barboza, H., Obiso, V., Sousse, R., Pandolfi, M., Pérez García-Pando, C., and Jorba, O.: Constraining the absorbing fraction of organic aerosol in an atmospheric chemistry model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12747,, 2021.

Paap Koemets, Sander Mirme, Kuno Kooser, and Heikki Junninen

The Highly Oxidized Molecule Ion Spectrometer (HOMIS) is a novel instrument for measuring the total concentration of highly oxidized molecules (HOM-s) (Bianchi et al., 2019) at atmospheric pressure. The device combines a chemical ionization charger with a multi-channel differential mobility analyzer. The chemical ionization charger is based on the principles outlined by Eisele and Tanner (1993). The charger is attached to a parallel differential mobility analyzer identical to the ones used in the Neutral cluster and Air Ion Spectrometer (NAIS, Mirme 2011), but with modified sample and sheath air flow rates to improve the mobility resolution of the device. The complete mobility distribution in the range from 3.2 to 0.056 cm2/V/s is measured simultaneously by 25 electrometers. The range captures the charger ions, monomers, dimers, trimers but also extends far towards larger particles to possibly detect larger HOM-s that have not been measured with existing instrumentation. The maximum time resolution of the device is 1 second allowing it to detect rapid changes in the sample. The device has been designed to be easy to use, require little maintenance and work reliably in various environments during long term measurements.

First results of the prototype were acquired from laboratory experiments and ambient measurements. Experiments were conducted at the Laboratory of Environmental Physics, University of Tartu. The sample was drawn from a reaction chamber where alpha-pinene and ozone were introduced. Initial results show a good response when concentrations of alpha-pinene and ozone were changed. 

Ambient measurements were conducted at the SMEAR Estonia measurement station in a hemiboreal forest for 10 days in the spring and two months in the winter of 2020. The HOMIS measurements were performed together with a CI-APi-TOF (Jokinen et al., 2012).



Bianchi, F., Kurtén, T., Riva, M., Mohr, C., Rissanen, M. P., Roldin, P., Berndt, T., Crounse, J. D., Wennberg, P. O., Mentel, T. F., Wildt, J., Junninen, H., Jokinen, T., Kulmala, M., Worsnop, D. R., Thornton, J. A., Donahue, N., Kjaergaard, H. G. and Ehn, M. (2019), “Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol”, Chemical Reviews, 119, 6, 3472–3509

Eisele, F. L., Tanner D. J. (1993), “Measurement of the gas phase concentration of H2SO4 and methane sulfonic acid and estimates of H2SO4 production and loss in the atmosphere”, JGR: Atmospheres, 98, 9001-9010

Jokinen T., Sipilä M., Junninen H., Ehn M., Lönn G., Hakala J., Petäjä T., Mauldin III R. L., Kulmala M., and Worsnop D. R. (2012), “Atmospheric sulphuric acid and neutral cluster measurements using CI-APi-TOF”, Atmospheric Chemistry and Physics, 12, 4117–4125

Mirme, S. (2011), “Development of nanometer aerosol measurement technology”, Doctoral thesis, University of Tartu

How to cite: Koemets, P., Mirme, S., Kooser, K., and Junninen, H.: Newly developed instrumentation for measuring highly oxidized molecules at atmospheric pressure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12911,, 2021.

Erik Hans Hoffmann, Tao Li, Andreas Tilgner, Yan Wang, and Hartmut Herrmann

Mercury is a neurotoxic element emitted predominantly in its less-reactive form as gaseous elemental mercury (GEM) into the atmosphere by various natural and anthropogenic processes. Once emitted it undergoes chemical processing in the atmospheric gas and aqueous phase. There, GEM is oxidised into gaseous oxidised mercury (GOM), which partitions into aerosol particles residing there as particulate bounded mercury (PBM) due to its much higher solubility. The faster deposition of GOM and PBM compared to GEM is of special environmental importance, because they can be converted into more toxic organic mercury in aquatic environments and then take serious place in the food web. Thus, it is crucial for models to understand the transformation of GEM into GOM and PBM and vice versa. To date, numerous gas-phase chemistry simulations were performed, but reveal missing oxidation and reduction processes. However, only few models exist that investigate the multiphase mercury chemistry in a detailed manner.

Therefore, a comprehensive multiphase mercury chemistry mechanism, the CAPRAM HG module 1.0 (CAPRAM-HG1.0), has been developed. The CAPRAM-HG1.0 includes 74 gas-phase reactions, 22 phase transfers and 77 aqueous-phase reactions. It was coupled to the multiphase chemistry mechanism MCMv3.2/CAPRAM4.0 and the extended CAPRAM halogen module 3.0 (CAPRAM-HM3.0) for investigations of multiphase Hg redox under Chinese polluted conditions. Simulations were performed for summer conditions in 2014 using the air parcel model SPACCIM to investigate the performance of the model to simulate typical concentrations and patterns of GEM, GOM and PBM.

Under non-cloud conditions, model results reveal good coincides with concentrations and patterns for GEM, GOM and PBM measured in China. However, the simulations also show that there are still high uncertainties in atmospheric mercury chemistry. Especially, the complexation with HULIS within aerosol particles needs evaluation as the simulations indicate this process as key process driving concentrations and patterns of both GOM and PBM. Further, the present study demonstrates the need of a better understanding of continental concentrations of reactive halogen species and particle bounded halides as well as their link to the multiphase chemistry and atmospheric cycling of mercury.

How to cite: Hoffmann, E. H., Li, T., Tilgner, A., Wang, Y., and Herrmann, H.: Towards an advanced description and modelling of the atmospheric multiphase chemistry of mercury: CAPRAM HG module 1.0, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13061,, 2021.

Grzegorz Florczyk, Katarzyna Nurowska, Agata Han, Michał Chiliński, and Krzysztof Markowicz

Relative humidity and rates of its change are relevant parameters in atmospheric sciences. Observations of output data of AE-51 aethalometer operating in ACS1000 humidity chamber reveal strong dependence of attenuation on rapid relative humidity changes. Data collected in winter 2020/21 suggests a probability of similar effect occurring during UAV measurements as thermodynamic parameters could change fast during such runs. Two AE-51 devices were connected in the WET and DRY ACS1000 humidity chamber's channels. During periodic relative humidity oscillations, incident negative peaks of equivalent black carbon mass concentration coincide with high negative derivatives of relative humidity. In most extreme cases values of -1000 ng/m3 equivalent black carbon mass concentration were recorded in parallel with relative humidity derivative of -1.5 %/min. These correlations seem to play an important role in atmospheric measurements as vertical profiles of aerosol parameters such as attenuation are collected using UAV runs during which relative humidity varies significantly. Our goal is to propose a correction method to minimise these anomalies.

How to cite: Florczyk, G., Nurowska, K., Han, A., Chiliński, M., and Markowicz, K.: Should black carbon concentration from aethalometer measurements onboard of UAVs be additionally corrected? - What is the impact of rapid relative humidity changes on our measurements?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13398,, 2021.

Roseline Thakur, Lubna Dada, Lisa Beck, Tommy Chan, Juha Sulo, Marjan Marbouti, Xu-Cheng He, Janne Lampilahti, Markus Lampimäki, Lauriane L.J Quéléver, Yee Jun Tham, Nina Sarnela, Katrianne Lehtipalo, Markku Kulmala, Mikko Sipilä, and Tuija Jokinen

Aerosols can originate from different sources and undergo various formation pathways. New Particle formation (NPF) events occur when precursor vapors nucleate and vapors with low volatility condense on the critical nuclei enabling them to grow to cloud condensation nuclei (CCN) relevant sizes. As CCN, these aerosols affect the occurrence of clouds and their lifetime on local, regional and global level.  Many studies have investigated new particle formation events from various sites ranging from urban areas, boreal forests to pristine locations; however, there is still a dearth of studies investigating coastal new particle formation, which is a complex phenomenon due to the dynamic and ever-changing atmospheric conditions at the coast.  A comprehensive study of particle number distributions and aerosol forming precursor vapors was carried out in a coastal capital city of Finland, Helsinki, during the summer of 2019. The experimental setup comprising of a nitrate-based chemical ionization atmospheric pressure interface time of flight mass spectrometer (CI-APi-TOF), a neutral cluster-air ion spectrometer (NAIS) and a particle size magnifier (PSM) were housed in and around the SMEAR III station in Kumpula Science campus. SMEAR III is a unique site situated in a semi-urban yet coastal location. The period of experiment coincided with the cyanobacterial bloom in the coastal areas of Finland and in the Baltic Sea region. Our study recorded several regional NPF and aerosol burst events during this period. High concentrations of sulfuric acid was found to be associated with the regional NPF events whereas increasing iodic acid concentrations was mostly associated with the initiation of burst events. The sources of sulfuric acid and iodic acid has been carefully evaluated in this study.


How to cite: Thakur, R., Dada, L., Beck, L., Chan, T., Sulo, J., Marbouti, M., He, X.-C., Lampilahti, J., Lampimäki, M., Quéléver, L. L. J., Tham, Y. J., Sarnela, N., Lehtipalo, K., Kulmala, M., Sipilä, M., and Jokinen, T.: Observations of New Particle Formation events during summertime in Helsinki, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13408,, 2021.

Katarzyna Nurowska, Grzegorz Florczyk, Agata Han, Michał Chiliński, and Krzysztof Markowicz

In this study the OPC-N3 low-cost particle matter counter was used to determine the hygroscopic properties of the aerosol. The work shows the first results of aerosol hygroscopicity conducted in Poland. The study was performed during Spring 2020 (lock-down period) and Winter 2020/2021. The research was conducted in the Geophysics Institute at the University of Warsaw, close to the city center. 

Two OPC-N3 sensors were connected to the outlet from two legs of the Aerosol Conditioning System ACS1000. In one of them, low relative humidity was kept at the level of 20%, and in the other, the relative humidity was changed in the range of 50-90% in cycles.

The calculation of growth factor was done by dividing the PM1 measured from wet pipe by PM1 measured in the dry channel. The hygroscopicity parameter κ was calculated from κ-Köhler theory, showing a fluctuation of the κ parameter which depends on aerosol type.

The variability of κ during Spring was ranging from values of 0.075 up to 0.437 (growth factor range 1.294 – 2.625).  The observed κ for Winter oscillates between 0.018 - 0.077 (growth factor range 1.057 – 1.246). The values of hygroscopicity of aerosol in winter are smaller than the ones corresponding to Spring, in line with respect to previous literature reports.

The study shows possibility to use OPC-N3 for calculation of the hygroscopic properties of the aerosol, however it means that the measurements of PM done by OPC-N3 can be biased by high relative humidity.

How to cite: Nurowska, K., Florczyk, G., Han, A., Chiliński, M., and Markowicz, K.: Determination of hygroscopic aerosol growth based on the OPC-N3 counter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13430,, 2021.

Laurynas Bučinskas and Andrius Garbaras

Stable isotope analysis is important tool in investigation of SO2 and sulfate particulate matter chemical processes and provides valuable information on their transport, natural and anthropogenic pollution sources. Around half of atmospheric SO2 is oxidized to sulfate which can then form on existing aerosols or even nucleate to produce new particles [1], [2]. Physical and chemical processes cause fractionation of sulfur isotope ratios which helps us to differentiate between different sulfur sources.

The aim of this work was to examine δ34S distribution in atmospheric sulfate aerosol particles and to characterize their sources while applying stable isotope mass spectrometry methods. For this task, the dependence between measurements of atmospheric sulfate aerosol δ34S and particulate sulfate concentration was found. The sample collection was performed in Vilnius, Lithuania from 5 March until 6 May, during the year 2020. By comparing the aerosol sulfate concentrations to air monitoring data it was found that their values change accordingly to the background particulate matter concentrations in Vilnius, however changes in atmospheric SO2 concentrations produced little effect. Subsequently, relationship between δ34S values and aerosol sulfate concentrations was plotted which revealed two possible major sources of sulfate aerosol pollution. These results were then related to atmospheric air parcel trajectory models which were applied to help characterize the pollution sources and their effect on measured δ34S values.

The results of this work showed that during the sampling period atmospheric sulfate aerosol δ34S values ranged from 6,1 ‰ to 12,6 ‰. Additionally, it was determined that local pollution sources are represented by lower values of δ34S whereas long range source δ34S values are higher. Finally, two probable dominant sources of atmospheric sulfate aerosol pollution were found.


[1]  C. Tomasi, A. Lupi, „Primary and Secondary Sources of Atmospheric Aerosol“, Atmospheric Aerosols, 2016.

[2]  M. Chin, D. J. Jacob, G. M. Gardner, M. S. Foreman-Fowler, P. A. Spiro, D. L. Savoie, „A global three-dimensional model of tropospheric sulfate“, J. Geophys. Res. Atmos., 1996.

How to cite: Bučinskas, L. and Garbaras, A.: Stable sulfur isotope analysis of aerosol in Vilnius, Lithuania, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14702,, 2021.

Ulrike Dusek, Agne Masalaite, Harro Meijer, Peng Yao, Rupert Holzinger, and Vidmantas Remeikis

The stable carbon isotope 13C has the potential to give insights into sources and processing of organic aerosol. However, the use for source apportionment has been somewhat limited, because the 13C source signatures vary and show some overlap. 13C/12C ratios are usually reported as δ13C indicating a permil deviation from the international reference standard Vienna Pee Dee Belemnite (V-PDB).

We use a method to measure δ13C  in OC desorbed from filter samples at three different temperature steps: 200 °C, 350°C and 650°C (Zenker et al.,2020). The results give a rough indication of aerosol volatility, as more volatile compounds usually desorb at lower temperatures.

We demonstrate with an extensive source study that in Lithuania and likely other Eastern European regions, the main anthropogenic primary sources for organic carbon (OC) have distinct isotopic signatures. δ13C  values of vehicular emissions show the most negative values around - 29 ‰, emissions from combustion of the most common wood types are more enriched with values around -26 to -27 ‰, and coal burning is around -25‰. For source samples d13C values at the three desorption temperature steps usually do not differ more than 1 ‰.

For ambient aerosol samples, the differences in δ13C values at different desorption temperatures are usually larger. This indicates varying source contribution or different chemical processes leading to the different volatility fractions. Combined isotopic and chemical analysis showed that in winter was a clear distinction in source contribution between the less refractory OC and the more refractory OC. We were able to identify fossil fuel burning as predominant source of the less refractory OC in the small particle size range (D< 0.18 μm), and biomass burning as predominant source of the more refractory OC in the larger size range (0.32< D<1 μm).

At all three sites, OC had more negative δ13C values in summer than in winter which can be explained by the contribution of biomass/coal burning sources in winter. At the urban site δ13C of OC did not change much with increasing desorption temperature in winter, which is typical for primary sources. In the summer δ13C of OC was clearly more negative for lower desorption temperatures at all three sites. This is likely due to the influence of secondary organic aerosol formation in summer, which should have depleted (more negative) isotopic signature and contributes strongly to the more volatile fraction.

A higher fraction of more refractory OC in summer compared to winter-time suggests active photochemical processing of the primary organic aerosol as an important process at all three sites. During a pollution episode transporting aged pollution from Poland and southern Europe to the otherwise clean forest site, a potential isotopic signature for photochemical aging was identified.

How to cite: Dusek, U., Masalaite, A., Meijer, H., Yao, P., Holzinger, R., and Remeikis, V.: Seasonal changes of sources, processes, and volatility of organic aerosol at urban, coastal and forest sites in Eastern Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14936,, 2021.

Athanasios Nenes, Andrea M. Arangio, Pourya Shahpoury, and Ewa Dabek-Zlotorzynska

Aerosol acidity and liquid water content (LWC) affect aerosol concentration and composition as well as the fate of the precursor compounds ammonia (NH3) and nitric acid (HNO3) [1,2]. Together with temperature, aerosol acidity and LWC determine the gas-particle partitioning of such precursors. In warm seasons, high aerosol acidity and low LWC promote the partitioning of NH3 to particulate phase as ammonium, while at the same time drive aerosol nitrate to the gas phase as HNO3. In cold seasons, the opposite effect can be observed. Given that the dry deposition rate of gaseous NH3 and HNO3 is up to 10 times faster than the particle phase, the conditions that favour the partitioning of these species to the gas phase also determine the dry deposition rates of reduced and oxidized nitrogen. This process has consequences for the accumulation of aerosols in the boundary layer, as well as the transport and deposition flux of nitrogen species[2].


In the present work, we explore the seasonal variation of aerosol acidity and liquid water content and their estimated effect on nitrogen dry deposition velocity using data collected over three years in Toronto, Canada, from January 2016 to December 2018. Aerosol acidity, in terms of H+ concentration, has large inter- and intra-seasonal variability, ranging between 5 and almost 3 orders of magnitude, respectively. By applying the framework developed in Nenes et al. 2020 [1], aerosol formation during winter is sensitive to HNO3 levels (pH range

~3 and ~6, LWC range ~0.4 and ~ 35.0 μg m-3), whereas in summer it tends to be insensitive to both NH3 and HNO3 (pH range ~1.4 and ~ 4, LWC range ~0.04 and ~10.0 μg m-3) This insensitive regime indicates that emissions of other precursors such as SOx and organic aerosol are major sources of aerosol variability in summer. In terms of nitrogen dry deposition, the seasonal variation experiences two regimes: in winter, the deposition is fast for NH3 and slow for HNO3, whereas in summer, both deposition of NH3 and HNO3 are fast.


In conclusion, the analysis of ambient aerosol data using aerosol pH and liquid water content suggest that in Toronto, emission controls of NOx in winter and of SOx in summer would be most beneficial for air quality.


[1] Nenes A., Pandis S., Weber R.J., Russell A., ACP, 20, 3249–3258, 2020

[2] Nenes A., Pandis S., Kanakidou M., Russell A., Song S., Vasilakos P., Weber R.J., ACPD, 20, 266, 2020

How to cite: Nenes, A., Arangio, A. M., Shahpoury, P., and Dabek-Zlotorzynska, E.: Seasonal aerosol acidity and liquid water content: impact on aerosol concentration and nitrogen deposition fluxes in a urban Canadian environment., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14953,, 2021.

Maria Ángeles Burgos Simón, Elisabeth Andrews, Gloria Titos, Angela Benedetti, Huisheng Bian, Virginie Buchard, Gabriele Curci, Zak Kipling, Alf Kirkevåg, Harri Kokkola, Anton Laakso, Julie Letertre-Danczak, Marianne Tronstad Lund, Hitoshi Matsui, Gunnar Myhre, Cynthia Randles, Michael Schulz, Twan van Noije, Kai Zhang, and Paul Zieger

The particle hygroscopic growth impacts the optical properties of aerosols and, in turn, affects the aerosol-radiation interaction and calculation of the Earth’s radiative balance. The dependence of particle light scattering on relative humidity (RH) can be described by the scattering enhancement factor f(RH), defined as the ratio between the particle light scattering coefficient at a given RH divided by its dry value.

The first effort of the AeroCom Phase III – INSITU experiment was to develop an observational dataset of scattering enhancement values at 26 sites to study the uptake of water by atmospheric aerosols, and evaluate f(RH) globally (Burgos et al., 2019). Model outputs from 10 Earth System Models (CAM, CAM-ATRAS, CAM-Oslo, GEOS-Chem, GEOS-GOCART, MERRAero, TM5, OsloCTM3, IFS-AER, and ECMWF) were then evaluated against this in-situ dataset. Building on these results, we investigate f(RH) in the context of other aerosol optical and chemical properties, making use of the same 10 Earth System Models (ESMs) and in-situ measurements as in Burgos et al. (2020) and Titos et al. (2021).

Given the difficulties of deploying and maintaining instrumentation for long-term, accurate and comprehensive f(RH) observations, it is desirable to find an observational proxy for f(RH). This observation-based proxy would also need to be reproduced in modelling space. Our aim here is to evaluate how ESMs currently represent the relationship between f(RH), scattering Ångström exponent (SAE), and single scattering albedo (SSA). This work helps to identify current challenges in modelling water-uptake by aerosols and their impact on aerosol optical properties within Earth system models.

We start by analyzing the behavior of SSA with RH, finding the expected increase with RH for all site types and models. Then, we analyze the three variables together (f(RH)-SSA-SAE relationship). Results show that hygroscopic particles tend to be bigger and scatter more than non-hygroscopic small particles, though variability within models is noticeable. This relationship can be further studied by relating SAE to model chemistry, by selecting those grid points dominated by a single chemical component (mass mixing ratios > 90%). Finally, we analyze model performance at three specific sites representing different aerosol types: Arctic, marine and rural. At these sites, the model data can be exactly temporally and spatially collocated with the observations, which should help to identify the models which exhibit better agreement with measurements and for which aerosol type.


Burgos, M.A. et al.: A global view on the effect of water uptake on aerosol particle light scattering. Sci Data 6, 157., 2019.

Burgos, M.A. et al.: A global model–measurement evaluation of particle light scattering coefficients at elevated relative humidity, Atmos. Chem. Phys., 20, 10231–10258,, 2020.

Titos, G. et al.: A global study of hygroscopicity-driven light scattering enhancement in the context of other in-situ aerosol optical properties, Atmos. Chem. Phys. Discuss. [preprint],, in review, 2020.

How to cite: Burgos Simón, M. Á., Andrews, E., Titos, G., Benedetti, A., Bian, H., Buchard, V., Curci, G., Kipling, Z., Kirkevåg, A., Kokkola, H., Laakso, A., Letertre-Danczak, J., Lund, M. T., Matsui, H., Myhre, G., Randles, C., Schulz, M., van Noije, T., Zhang, K., and Zieger, P.: First global assessment of modelled aerosol hygroscopicity in the context of other aerosol optical properties, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15340,, 2021.

Sara Marie Blichner, Moa Kristina Sporre, and Terje Koren Berntsen

Cloud-aerosol interactions are responsible for much of the uncertainty in forcing estimates from pre-industrial times and thus also climate sensitivity and future projections. Maybe the most important factor in this is our lack of knowledge about pre-industrial aerosols, their sources and their ability to act as cloud condensation nuclei (CCN). The number of CCN is highly dependent on secondary aerosol formation and in particular how much of this secondary aerosol mass that goes to new particle formation (NPF) and early particle growth, versus growing already large particles even larger. 
Earth system models which seek to model this, face a challenge because we need to represent processes at a very fine scale (nanometers) to a sufficient accuracy, while simultaneously keeping computational costs low. A common approach is to use log-normal modes to represent the sizedistribution, while more computationally expensive sectional schemes are considered closer to first principles. 

In this study, we investigate the effect of a newly developed scheme for early particle growth on the effective radiative forcing from cloud-aerosol interactions (ERFaci)  in the Norwegian Earth System Model v2 (NorESMv2). The new scheme, referred to as OsloAeroSec, presented in  Blichner et al. (2020), combines a sectional scheme for the growth of the smallest particles (5 - 39.6 nm), with the original semi-modal aerosol scheme which would simply parameterize the growth up to the smallest mode with Lehtinen et al. (2007). This was shown to to improve the representation of CCN relevant particle concentrations, when compared to measurement data.  

We find that ERFaci is weakened by approximately 10 % with the new scheme (from -1.29  to -1.16 Wm-2). The weakening originates from OsloAeroSec (the new scheme) reducing particle formation in regions with high aerosol concentrations while increasing it in very pristine regions. We find, perhaps surprisingly, that an important factor for the overall forcing, is that  NPF inhibits aerosol activation into cloud droplets in high-aerosol-concentration regions, while the opposite is true in pristine regions. 
This is because the NPF particles act as a condensation sink, and if they cannot activate directly themselves, they may reduce the growth of the larger particles which would otherwise activate. 
Furthermore, we find that the increase in particle hygroscopicity with present day emissions of sulphate pre-cursors, decreases the size of the activated particles, and thus makes NPF particles more relevant for cloud droplet activation. 


Lehtinen, Kari E. J., Miikka Dal Maso, Markku Kulmala, and Veli-Matti Kerminen. “Estimating Nucleation Rates from Apparent Particle Formation Rates and Vice Versa: Revised Formulation of the Kerminen–Kulmala Equation.” Journal of Aerosol Science (2007):

Blichner, Sara M., Moa K. Sporre, Risto Makkonen, and Terje K. Berntsen. “Implementing a sectional scheme for early aerosol growth from new particle formation in the Norwegian Earth System Model v2: comparison to observations and climate impacts.” Geoscientific Model Development Discussions (2020):

How to cite: Blichner, S. M., Sporre, M. K., and Berntsen, T. K.: Reduced effective radiative forcing from cloud-aerosol interactions with improved modelling of early aerosol growth in an Earth System Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15397,, 2021.

Liang Wen, Thomas Schaefer, and Hartmut Herrmann

Dicarboxylic acids (DCAs) are widely distributed in atmospheric aerosols and cloud droplets and are mainly formed by the oxidation of volatile organic compounds (VOCs). For example, glutaric acid and adipic acid are two kinds of the DCAs that can be oxidized by hydroxyl radical (‧OH) reactions in the aqueous phase of aerosols and droplets. In the present study, the temperature- and pH-dependent rate constants of the aqueous OH radical reactions of the two DCAs were investigated by a laser flash photolysis-long path absorption setup using the competition kinetics method. Based on speciation calculations, the OH radical reaction rate constants of the fully protonated (H2A), deprotonated (HA-) and fully deprotonated (A2-) forms of the two DCAs were determined. The following Arrhenius expressions for the T-dependency of the OH radical reaction of glutaric acid, k(T, H2A) = (3.9 ± 0.1) × 1010 × exp[(-1270 ± 200 K)/T], k(T, HA-) = (2.3 ± 0.1) × 1011 × exp[(-1660 ± 190 K)/T], k(T, A2-) = (1.4 ± 0.1) × 1011 × exp[(-1400 ± 170 K)/T] and adipic acid, k(T, H2A) = (7.5 ± 0.2) × 1010 × exp[(-1210 ± 170 K)/T], k(T, HA-) = (9.5 ± 0.3) × 1010 × exp[(-1200 ± 200 K)/T], k(T, A2-) = (8.7 ± 0.2) × 1010 × exp[(-1100 ± 170 K)/T] (in unit of L mol-1 s-1) were derived.

The energy barriers of the H-atom abstractions were simulated by the Density Functional Theory calculations run with the GAUSSIAN package using the M06-2X method and the basis set m062x/6-311++g(3df,2p). The results showed that the energy barriers were lower at the Cβ-atoms and are higher at the Cα-atoms of the two DCAs, clearly suggesting that the H-atom abstractions occurred predominately at the Cβ-atoms. In addition, the ionizations can enhance the electrostatic effects of the carboxyl groups, significantly reducing the energy barriers, leading to the order of OH radical reactivity as  <  < . This study intends to better characterize the losing processes of glutaric acid and adipic acid in atmospheres.

How to cite: Wen, L., Schaefer, T., and Herrmann, H.: Reaction kinetics of OH radicals with glutaric acid and adipic acid in the aqueous phase, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15624,, 2021.

Ilona Riipinen, Annica Ekman, Matthew Salter, and Karoliina Pulkkinen and the The FORCeS consortium

Together with imminent climate action, building a sustainable future for the humanity requires striving for healthier environments. Atmospheric aerosol particles (also referred to as particulate matter, PM) play a key role in defining the air that the future generations will breathe but also the climates they live in, PM being an important short-lived climate forcer but also a key component of air quality and global environmental health hazard. The contribution of aerosol particles has been a key uncertainty in estimates of the Earth’s radiative forcing since the establishment of the Intergovernmental Panel for Climate Change (IPCC) and still remains as the single largest quoted source of uncertainty in the anthropogenic climate forcing during the industrial period. In the latest assessment by the IPCC, the radiative forcing by aerosol particles has been estimated to be -0.45 W m-2 (between -0.95 and 0.05 W m-2) for aerosol-radiation interactions (RFari) and -0.45 W m-2 (between -1.25 and 0 W m-2) for aerosol-cloud interactions (RFaci). Recent reviews indicate no significant reduction in the uncertainty. The large range of possible aerosol forcing values has serious consequences for climate projections and therefore developing strategies for reaching Paris agreement targets. It is currently not possible to say if a reduction in aerosol emissions due to air pollution mitigation and a phase-out of aerosol emissions will result in a noticeable increase in global mean temperature  or in a negligible climate effect. We will discuss the components and reasons of this uncertainty, focusing on those that are important for aerosol-cloud interactions. We will identify critical bottlenecks in 1) scientific understanding of fundamental aerosol and cloud microphysical processes; 2) method development for improving the understanding of aerosol, cloud, and aerosol-cloud processes as well as their representation in Earth System Models (ESMs); and 3) knowledge transfer within and between the relevant research communities. We will argue for key actions to overcome these bottlenecks, giving examples of good practices for breaking new ground in this long-standing problem that continues to intrigue the atmospheric and climate science communities. Besides enhancing the scientific understanding of the Earth system within the realm of natural science based on multiple lines of evidence, and developing novel (e.g. machine learning –based) methodologies for analyzing existing observational data and model output, we call for additional perspectives from social science and humanities on the communication and knowledge transfer practices within atmospheric and climate research. Making the relevant knowledge transfer pathways and processes transparent is urgently needed to enable systematic determination of the actions required to maximally utilize the existing knowledge, and to ensure effective implementation of new results that may help to narrow down the uncertainty associated with aerosols in climate projections. Improved understanding of the role of aerosols in the climate system will result in enhanced credibility of ESMs and hence also tighter constraints for policies aiming for simultaneous climate neutrality and zero pollution targets.

How to cite: Riipinen, I., Ekman, A., Salter, M., and Pulkkinen, K. and the The FORCeS consortium: Is there hope for reducing the uncertainty associated with aerosols in climate projections? , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15717,, 2021.

Noel Baker, Michel Anciaux, Philippe Demoulin, Didier Fussen, Didier Pieroux, and Sylvain Ranvier

Led by the Belgian Institute for Space Aeronomy, the ESA-backed mission PICASSO (PICo-Satellite for Atmospheric and Space Science Observations) successfully launched its gold-plated satellite on an Arianespace Vega rocket in September 2020. PICASSO is a 3U CubeSat mission in collaboration with VTT Technical Research Center of Finland Ltd, AAC Clyde Space Ltd. (UK), and the CSL (Centre Spatial de Liège), Belgium. The commissioning of the two onboard scientific instruments is currently ongoing; once they are operational, PICASSO will be capable of providing scientific measurements of the Earth’s atmosphere. VISION, proposed by BISA and developed by VTT, will retrieve vertical profiles of ozone and temperature by observing the Earth's atmospheric limb during orbital Sun occultation; and SLP, developed by BISA, will measure in situ plasma density and electron temperature together with the spacecraft potential.

Serving as a groundbreaking proof-of-concept, the PICASSO mission has taught valuable lessons about the advantages of CubeSat technology as well as its many complexities and challenges. These lessons learned, along with preliminary measurements from the two instruments, will be presented and discussed.

How to cite: Baker, N., Anciaux, M., Demoulin, P., Fussen, D., Pieroux, D., and Ranvier, S.: PICASSO: The Golden CubeSat, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15865,, 2021.

Despina Paraskevopoulou, George Grivas, Aikaterini Bougiatioti, Iasonas Stavroulas, Maria Tsagkaraki, Eleni Liakakou, Athanasios Nenes, and Nikolaos Mihalopoulos

PM-induced oxidative stress has been proposed as a primary mechanism in cardiovascular and respiratory diseases, as well as premature death. Consequently, a variety of in vitro and in vivo assays have been developed in order to estimate the oxidative potential of ambient PM (Particulate matter), including the acellular assay of DTT (dithiothreitol), which is used in the present study. Athens, Greece is representative of air masses arriving over Eastern Mediterranean, highlighting the effect of long-range aerosol transportation and intense local emissions, such as wood burning for domestic heating purposes during the coldest period of the year. 

Most studies of aerosol oxidative potential (OP) cover a short period of time, while in this study the OP was measured during two years (2016-2018), in parallel with other PM chemical components, in order to identify the sources of aerosol OP. Fine aerosol fraction (PM2.5, diameter < 2.5 μm) was collected, using quartz fibre filters and low-volume samplers, in the centre of Athens city.

An innovative semi-automated system was used for the determination of PM water soluble oxidative potential, following the approach of Fang et al. (2015). Concurrent estimation of inorganic and organic aerosol components’ concentrations was accomplished through Ion chromatography, Aerosol Chemical Speciation Monitor, Aethalometer and OC/EC analyser. Additionally, the samples were further analyzed by Inductively coupled plasma mass spectrometry for major and trace water-soluble metal concentrations. Principal component analysis and Positive Matrix Factorization are applied to identify the sources of fine aerosol at the studied site in Athens, and determine the contribution of each source to aerosol OP, on a seasonal basis

As expected, OP presented higher values during wintertime, when wood burning appeared to be the dominant source of aerosol. These results agree with previous studies, indicating that the combustion is the major source of water-soluble OP, both as primary and secondary emission (Paraskevopulou et al. 2019). Whereas during summer, the current study reveals, for the first time, the significant impact of water-soluble metals in aerosol toxicity during the warmest period of the year, over the studied area. The aforementioned combination of various PM chemical parameters leads to a scarce identification of various aerosol OP sources on a temporal basis, in the area of Eastern Mediterranean.

How to cite: Paraskevopoulou, D., Grivas, G., Bougiatioti, A., Stavroulas, I., Tsagkaraki, M., Liakakou, E., Nenes, A., and Mihalopoulos, N.: PM-induced oxidative potential: Two years measurements and source apportionment, on a seasonal basis, in Athens, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15961,, 2021.

Alexei Kiselev, Corina Wieber, Ahmed Eid Zoheir Amer, and Kersten Rabe

The plant pathogenic bacteria Pseudomonas syringae are capable of inducing ice nucleation at low supercooling due to the presence of INA proteins on the outer cell membrane. Moreover, P. Syringae was shown to survive long-range transport in cold airmasses and redeposition to the earth’s surface with rain and snow. Thus, the life cycle of P. syringae is tightly coupled to the water cycle in the Earth's ecosystem. Understanding the survival mechanism of P. Syringae exposed to atmospheric cloud conditions is a prerequisite for characterization of bacteria as atmospheric ice nucleating particles, describing its dissemination paths and potential role in the spread of plant-pathogenic disease.

In this contribution we report on the viability study of ice nucleating active bacteria in freezing cloud droplets. To investigate the bacterial viability, water droplets containing several bacterial cells with low and high concentration of INA proteins are levitated in an electrodynamic balance (EDB) and cooled down to a temperature of -25°C. After freezing, the droplets are extracted from the EDB and the survival probability of the bacteria is determined by colony counting. A fluorescence stain and a high-speed video camera were used to visualize individual bacteria in the levitated droplets and to study their behavior during freezing.

The results have shown that the survival of bacteria depends on the freezing dynamics of bacteria-containing droplets (growth rate of ice in supercooled water). The P. syringae bacteria with high concentration of INA proteins are capable of inducing freezing at low supercooling and thus inhibit the growth rate of ice crystals, resulting in higher chance to survive the freezing. If high supercooling is achieved, the ice growth rate immediately after nucleation is very high and the survival probability is dramatically reduced.

How to cite: Kiselev, A., Wieber, C., Zoheir Amer, A. E., and Rabe, K.: Viability study of ice nucleating active bacteria (Pseudomonas Syringae) in freezing cloud droplets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16092,, 2021.