As a primary component of PM₁₀, ambient mineral dust particles have been linked to increased morbidity and health risks in urban environments. Dust particles also alter the Earth's radiation balance because of their absorbance and scattering properties. We employed absorption photometers to investigate the real-time concentration and light absorption of dust particles in central Los Angeles for three different periods. We adopted a novel method by utilizing a coarse particle virtual impactor that increases the concentration of coarse particles by around 20 times to eliminate the effects of light absorption of black carbon, which has a considerably higher light absorption and dominates the PM_2.5 light absorption. The concentrated coarse particles were collected on Teflon filters, and their chemical components were measured by the Inductively Coupled Plasma Mass Spectroscopy method. The light absorption of dust particles was determined by subtracting the measured values by aethalometers on two different lines: 1) the virtual impactor line and 2) the PM_2.5 line. The light absorption coefficient of the dust particles in central Los Angeles was estimated to be 2.7 1/Mm at 370 nm, while the corresponding value at 880 nm was 0.41 1/Mm. The estimated mineral dust mass concentration showed a similar trend with the reported coarse PM by the California air resource board. Finally, we determine the absorption Angstrom exponent (AAE) of dust particles in the area to be around 2.18 for the entire study period. Our findings affirm that this method can be used to analyze the mineral dust concentration in distinctive urban environments effectively.

How to cite: Sioutas, C., Tohidi, R., and Jalali farahani, V.: Measurement of the mineral dust concentration using an optical-based approach in central Los Angeles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-782, https://doi.org/10.5194/egusphere-egu22-782, 2022.

Isotope fractionation between the gas and aerosol phases is an important phenomenon in terms of studying atmospheric processes. Here, we studied seasonal variations in the stable carbon isotope ratio (δ¹³C) of total carbon (TC; δ¹³C_TC) and water-soluble organic carbon (WSOC; δ¹³C_WSOC) in fine aerosol particles (PM_2.5) as well as in the total carbon of the gas phase (TCgas; δ¹³C_TCgas) at a suburban site in Prague, Czech Republic, Central Europe. The most ¹³C enrichment was found in WSOC, followed by particulate TC, whereas the most ¹³C depletion was found in gaseous TC. The clear seasonal pattern for all δ¹³C values (with the highest values in winter and lowest in summer) provides evidence for the presence of different aerosol sources at the site during the year. Despite the different seasonal compositions of carbonaceous aerosols, the isotope differences (Δδ¹³C) between the analyzed bulk aerosol parts and phases were similar during the seasons. This shows that the fractionation of stable carbon isotopes is a predominantly physical process in which the chemical composition of individual compounds in bulk aerosols does not play a major role.

Acknowledgement: This conference contribution was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project No. LM2018122, by the ERDF project "ACTRIS-CZ RI" (No. CZ.02.1.01/0.0/0.0/16_013/0001315) and by the Japan Society for the Promotion of Science (JSPS) through Grant-in-Aid No. 24221001. We appreciate the financial support of JSPS fellowship to P. Vodička (P16760) in Japan.

Reference: Vodička, P., Kawamura, K., Schwarz, J., Ždímal, V.: Seasonal changes in stable carbon isotopic composition in the bulk aerosol and gas phases at a suburban site in Prague, Sci. Total Environ., 803, 149767, 2022. https://doi.org/10.1016/j.scitotenv.2021.149767.

How to cite: Vodička, P., Kawamura, K., Schwarz, J., and Ždímal, V.: Differences in stable carbon isotopic composition in the fine bulk aerosol and gas phases based on seasonally resolved data at a Prague site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1654, https://doi.org/10.5194/egusphere-egu22-1654, 2022.

Corresponding author: PhD student RV Chiritescu chiritescu.robert.valentin@gmail.com

Abstract:

Air pollution in general and urban air pollution in particular have significant influences on atmosphere composition and hence on climate, environment, and human health. Although ground-based measurements have been performed for some decades and many observational studies were reported, information on air quality in some areas in East Europe are sparsely distributed. Romania represents the largest country at the crossroads of Central, Southeastern and Eastern Europe, and experience rapid economic growth since 2000s. It has a terrain distributed relatively equally between mountains, hills, and plains, and various regional climates (from alpine climate, to cold or wet warm continental, to warm oceanic due to proximity of Black Sea, in Koeppen classification). Various levels of development generate more by-products, including air pollution, deteriorating therefore the air quality at regional levels. Meteorology and topography also may influence the air pollution.

The aim of present study was to comparatively assess the air pollution levels in 15 urban area spread out over Romania in 2019 and 2020, as the first pandemic year of COVID-19. The selected cities have different level of economic development, have various climate and topographic conditions, and they are expected to be impacted by manifold pollution sources. A special attention was paid to the evaluation of the impact of different levels of social restrictions that were taken in order to diminish the spread of SARS-CoV-2 virus.

Using the ground-based measurements from the Romanian National Air Quality Network, two observational data sets were constructed with particulate matter with an aerodynamic diameter below 10 μm (PM₁₀) and below 2.5 μm (PM_2.5) and with major gaseous air pollutants (CO, NO₂, SO₂, O₃) mass concentrations for 2019 and 2020. Air pollutants variations were statistical analyzed for each season for each site.

The largest contributor to the pollution was Bucharest, the most developed city. Lowest air pollution levels were measured during the lockdown period in spring, as main traffic and non-essential activities were severely restricted. The reductions of air pollution mass concentrations due to the imposed social restrictions were found to be urban area-dependent.

Outcomes of present research contribute to scientific knowledge regarding temporal and spatial variation of major air pollutants at the country scale, can help for identification of air pollution sources and in air quality modeling at urban scale.

Acknowledgment

The research leading to these results has received funding from the NO Grants 2014-2021, under Project contract no. 31/2020, EEA-RO-NO-2019-0423 project. Data regarding ground-based air pollutants and local meteorology were extracted from the public available Romanian National Air Quality Database, www.calitateaer.ro, last accessed in December 2021. BM was supported by the University of Bucharest, PhD research grant.

How to cite: Chiritescu, R. V., Mihalache, B., Dumitru, A., and Iorga, G.: Air pollution over Romania: a comparative study 2019 - 2020 using ground-based measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2205, https://doi.org/10.5194/egusphere-egu22-2205, 2022.

Abstract

Pollen levels in rapidly developing urban areas are of particular interest due to their negative impact on human health, being responsible for the increasing prevalence of seasonal allergic diseases. The objective of present work is to analyze the potential links through correlations or anti-correlations between variations of pollen concentrations and the major atmospheric pollutant concentrations PM₁₀, PM_2.5, NO_x, CO, VOCs, O₃, SO₂ and/or meteorological conditions. The research was carried out in the city of Bucharest, in the largest urban agglomeration (Bucharest-Ilfov) in Romania. The main allergenic plants in Bucharest are tress, grasses and weeds species, which pollinate from early spring to late summer-fall. Mass concentrations of air pollutants PM10, PM2.5, NOx, CO, VOCs, O3, SO2 were extracted from the Bucharest air quality database, monitoring belonging to the Bucharest Air Quality Monitoring Network. Hourly data were converted to daily means. Computations, graphs and statistical analysis were performed using R software with the Openair package [1]. The present study confirms the seasonal pattern of the main allergenic pollen in Bucharest area. Fluctuations between maximum and minimum values of the observed pollen concentration correspond to the bi-annual sequence of the flowering. The dominant presence of tree pollen particles is observed in spring, of grass pollen particles mainly in summer, and pollen particles from weeds appear in late summer and early autumn. Weather conditions significantly influence pollen concentration, with temperature, solar radiation and relative humidity being the most influencing factors. The positive correlation was observed between pollen and particulate matter PM10 and PM2.5, nitrogen oxides and volatile organic compounds [2].

Key words: allergenic pollen, meteorological parameters, urban air pollution

[1] D.C. Carslaw and K. Ropkins, Environ. Model. Softw. 27-28, 52-61 (2012).

[2] A.-M. Rosianu, P.M. Leru, S. Stefan, G. Iorga, L. Marmureanu, Rom.Rep.Phys. 2021, in press

Acknowledgements:

This work was supported by European Regional Development Fund through Competitiveness Operational Programme 2014–2020, Action 1.1.3 creating synergies with H2020 programme, project Support Center for European project management and European promotion, MYSMIS code 107874, ctr. no. 253/2.06.2020, Romanian National Core Program Contract No.18N/2019. AMR was supported by the University of Bucharest, PhD research grant. GI acknowledges the support from NO Grants 2014-2021, under Project EEA-RO-NO-2019-0423, contract no 31/01.09.2020. The authors gratefully acknowledge the efforts of AM Eftimie (chemist) and VF Anton, MD, members of the Allergology Research team of Colentina Clinical Hospital who helped in pollen collection and measurements and the National Air Quality Monitoring Network (NAQMN, www.calitateaer.ro) for free access to air pollutant database. Present research [2] was accepted for publication and is currently in press at Romanian Reports in Physics (http://www.rrp.infim.ro/IP/AP604.pdf).

How to cite: Ana-Maria, R., Poliana, L., Gabriela, I., and Luminita, M.: Study of atmospheric pollen and major air pollutant concentrations in relation with meteorological conditions in Bucharest, Romania, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3053, https://doi.org/10.5194/egusphere-egu22-3053, 2022.

Aqueous-phase chemistry of fog and cloud waters plays an important role in the formation and aging of secondary organic aerosols (e.g. Ervens et al.,2011; Herrmann et al., 2015). Transitions metal ions driving Fenton chemistry in aqueous aerosols are one of the main sources of OH radicals besides direct uptake from the gas-phase (Ervens et al., 2003). The most abundant transition metal in aqueous aerosols is iron released from natural sources like sea salt spray and mineral dust or anthropogenic emissions. The generation of OH radicals by Fenton chemistry might drive or inhibit atmospheric new particle formation in cloud and fog water, or above salt lakes (e.g. Kamilli et al., 2015; Daumit et al., 2016), thus, having a direct impact on the climate system.

A first set of experiments has been carried out in a flow reactor investigating the influence of ferric and ferrous iron on new particle formation under dark and humid conditions (RH > 70%). α-Pinene was used as an organic precursor molecule for secondary organic aerosol (SOA) formation by dark ozonolysis. Droplets of FeSO₄, FeCl₃ and (NH₄)₂SO₄ (as control) were produced by nebulizing solutions of varying concentrations between 0.1 µM and 30 mM using a custom-built atomizer. Particle size distributions were measured using a scanning mobility particle size spectrometer (SMPS, Grimm Aerosoltechnik).

First results show a significant decrease in geometric mean diameter of the produced particle population with increasing FeCl₃ concentration. This effect neither occurs when nebulizing FeSO₄ nor (NH₄)₂SO₄. These results imply that Fe³⁺ might inhibit growth of SOA under dark conditions.

More data analysis is ongoing and further experiments are planned to better understand the influence of iron on aqueous-phase SOA.

References

Daumit, K. E., Carrasquillo, A. J., Sugrue, R. A., & Kroll, J. H. (2016). Effects of condensed-phase oxidants on secondary organic aerosol formation. The Journal of Physical Chemistry A, 120(9), 1386-1394.

Ervens, B., George, C., Williams, J. E., Buxton, G. V., Salmon, G. A., Bydder, M., ... & Herrmann, H. (2003). CAPRAM 2.4 (MODAC mechanism): An extended and condensed tropospheric aqueous phase mechanism and its application. Journal of Geophysical Research: Atmospheres, 108(D14).

 Ervens, B., Turpin, B. J., & Weber, R. J. (2011). Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies. Atmospheric Chemistry and Physics, 11(21), 11069-11102.

Herrmann, H., Schaefer, T., Tilgner, A., Styler, S. A., Weller, C., Teich, M., & Otto, T. (2015). Tropospheric aqueous-phase chemistry: kinetics, mechanisms, and its coupling to a changing gas phase. Chemical reviews, 115(10), 4259-4334.

Kamilli, K. A., Ofner, J., Lendl, B., Schmitt-Kopplin, P., & Held, A. (2015). New particle formation above a simulated salt lake in aerosol chamber experiments. Environmental Chemistry, 12(4), 489-503.

How to cite: Lüchtrath, S., Klemer, S., and Held, A.: Influence of ferrous and ferric ions in the aqueous phase on SOA formation in flow reactor experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3150, https://doi.org/10.5194/egusphere-egu22-3150, 2022.

Aromatic aldehydes are a major gas-phase constitutes of troposphere, which play a fundamental role in the chemistry of polluted regions. They can be directly emitted from vast variety of anthropogenic and biogenic sources. Apart from those, they could be also transformed in the atmosphere by photolysis and/or can get oxidized in presence of atmospheric oxidants such as radicals, yielding hydroxyaldehydes as the main final products. Even though the formation process takes place primarily in the atmospheric gas phase, the produced hydroxyaldehydes are considered as water-soluble compounds due to their Henry’s Law constants, and are therefore capable of undergoing efficient phase transfer to cloud droplets, fog, haze, rain, and deliquescent aerosols, commonly referred as atmospheric aqueous phase. Dissolved organic gases can additionally be oxidized in the aqueous phase, where they contribute to aerosol mass production during cloud evaporation event, forming aqueous-phase secondary organic aerosols (aqSOAs). The potential formation of SOAs in the aqueous phase was estimated by a model prediction, where net global production rate accounts for 10 Tg yr^-1 to 50 Tr yr^-1. Additionally, there is a lack of aqueous-phase kinetic data with atmospherically relevant radicals that could be used to achieve an accurate description and model prediction of multiphase tropospheric chemistry. Accordingly, in the present study the second-order rate constants for the oxidation reactions of glyceraldehyde, glycolaldehyde, and lactaldehyde with hydroxyl radicals (‧OH), sulfate radicals (SO₄‧^-), and nitrate radicals (NO₃‧) in the aqueous phase were determined. In case of glycolaldehyde, the subsequent radical-initiated second-order rate constants (k_2nd) at 298 K were obtained: k(‧OH) = (1.3 ± 0.1) × 10⁹ L mol^-1 s^-1, k(SO₄‧^‑) = (2.9 ± 0.2) × 10⁷ L mol^‑1 s^-1, and k(NO₃‧) = (3.9 ±1.1) × 10⁶ L mol^-1 s^-1, respectively. In addition, the temperature-dependencies of the rate constants were determined in ranges between 278 and 318 K. Through the obtained rate constants and their T-dependencies, the degradation of hydroxyaldehydes with atmospherically relevant radicals in the aqueous-phase can be currently assigned, by which the predictive capabilities of models could be reached. These findings reveal the importance of aqueous phase conversion of gaseous oxidation products, contributing to the budget of important tropospheric aqueous phase carbonyls, which are important for better understanding the formation pathway of in-cloud processed SOAs.

How to cite: Mekic, M., Schaefer, T., and Herrmann, H.: T-dependent oxidation of hydroxyaldehydes in the aqueous phase with atmospherically relevant radicals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3892, https://doi.org/10.5194/egusphere-egu22-3892, 2022.

Amines are important but poorly studied organic constituents in the marine atmosphere. There is strong evidence that within the marine boundary layer, the formation of new aerosol particles and the increase in particle mass is influenced by amines. However, very high uncertainties still exist with respect to: the sources, the further chemical reactions within the multiphase chemical system of the marine atmosphere, and the contribution to the marine aerosol mass. A deeper understanding of the amine-initialized formation of organic nitrogen in marine aerosol particles requires fundamental mechanistic modeling studies of the multiphase oxidation of amines.
Therefore, a detailed multiphase chemistry mechanism, the CAPRAM Amine module, has been developed to describe the oxidation of ammonia (NH₃), monomethylamine (MMA), dimethylamine (DMA) and trimethylamine (TMA) in the atmosphere. This mechanism is the first that considers the formation of the auto-oxidation products from DMA and TMA and their further oxidative fate in both the gas and aqueous-phase. Overall, the mechanism currently contains 541 reactions, thereof 232 gas-phase reactions 52 phase transfer reactions, and 257 aqueous-phase reactions.
In the present study, first simulations of an idealized marine environment were performed investigating the chemical processing of amines under cloud and non-cloud conditions. The simulations indicate that uptake is a main loss term for DMA whereas for TMA it is oxidation in the gas phase. This shows that models considering amine driven new particle formation have to consider both uptake and gas-phase oxidation. Interestingly, the chemical rates analyses revealed an unexpected important chemical conversion of amines during cloud conditions, where TMA, DMA and MMA are degraded into DMA, MMA and NH₃, respectively. This unexpected fate of amines can have implications for the current unknown high DMA concentrations in the marine boundary layer that cannot be explained by oceanic emission alone. Because of the importance of DMA and TMA for new particle formation, the uncovered processes have to be thus analyzed by laboratory studies in more detail.

How to cite: Hoffmann, E. H., Tilgner, A., and Herrmann, H.: Advanced modelling of the multiphase chemistry of methylamines with CAPRAM, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4416, https://doi.org/10.5194/egusphere-egu22-4416, 2022.

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 a strong dependence of attenuation when rapid relative humidity changes are present. Data collected in winter 2020/21 and in autumn 2021 suggests a probability of similar effects occurring during UAV measurements as thermodynamic parameters could change fast during such runs. The effect is caused by an apparatus’ design preventing humid air to reach the part of the filter used as a reference. The measurement device compares the wet part of the filter to the dry reference part and produces sharp excursions in the output signal. These effects can be limited by introducing a drying unit as a part of an inlet. The presented study was aimed to compare a drying unit utilising a silica gel (passive drying) and a heated part of an inlet (active drying).

How to cite: Florczyk, G. and Markowicz, K.: The silica gel dryer or the electrical heating. Which one is better to ameliorate humidity related anomalies using the MicroAeth AE-51?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4814, https://doi.org/10.5194/egusphere-egu22-4814, 2022.

How to cite: Topping, D., Crawford, I., Gallagher, M., Moss, M., Chan, M. N., Lee, H. B. M., Xing, S., Ng, T. H., and Tai, A.: Deep learning cluster techniques for large aerosol datasets , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4988, https://doi.org/10.5194/egusphere-egu22-4988, 2022.

Bioaerosols are particles originating from biological sources. Of these, primary bioaerosol particles (PBAP) are those directly emitted as entities, in parts or as agglomerates of particles such as bacteria, spores or pollen. In the atmosphere, PBAP are important players by acting as cloud condensation nuclei and ice nucleating particles (INP). Their relevance for cloud formation is especially important over pristine marine environments, where PBAP are emitted within sea spray aerosol (SSA) and are expected to contribute significantly to the abundance of INP. However, the emissions and sources of PBAP over oceans remain poorly understood.

Within this work, we performed a controlled sea spray experiment in the Baltic Sea using a novel single-particle fluorescence and scattering instrument, the Multiparameter Bioaerosol Spectrometer (MBS), in combination with bacterial analysis of aerosol and sea water communities. Using this setup, we successfully identified large PBAP (D > 0.8 µm) within SSA and estimated their emissions to be 1 s^-1m^-2. Moreover, 1 out of every 10⁴ particles (D > 0.8 µm) was classified as PBAP. The morphology of large fluorescent SSA showed a clear transition during the campaign. This change was most likely linked to changes in the seawater biogeochemical properties observed during the ship campaign. This change was also observed in changes of the bacterial population of the aerosol and seawater, as determined by the 16s rRNA analysis. The bacterial populations were significantly distinct from each other, implying a selective transfer of certain species from seawater to the atmosphere.

Our results will help to better constrain the emission of PBAP from marine sources to the atmosphere and will help to understand how biogeochemical processes within the sea water can influence particle properties of SSA (e.g. particle morphology).

The content of this work is currently in review at Environmental Science and Technology (ES&T).

How to cite: Freitas, G., Stolle, C., H. Kaye, P., Stanley, W., P.R. Herlemann, D., Salter, M., and Zieger, P.: Emission of Primary Bioaerosol Particles from Baltic Seawater, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5181, https://doi.org/10.5194/egusphere-egu22-5181, 2022.

Aerosol chemical composition is an important driver for hygroscopic growth and hence cloud activation. A major fraction of the aerosol consists of inorganic components, for which thermodynamic equilibrium models are commonly used to describe the chemical composition, including total water uptake.
However, these thermodynamics are relatively computationally expensive calculations, minimising the Gibbs free energy of the total system. Consequently, faster computations are desirable, which can be facilitated using machine learning techniques.

In this study, we apply neuronal networks, being trained on the output of an equilibrium thermodynamics model (ISORROPIA 2), to represent both the chemical composition and associated aerosol water uptake. We investigate the quality of the trained network against independent data from the equilibrium model and find a good agreement of the trained network model against the original data. Furthermore, we also test the applicability of the trained model in a parameter space outside of the trained data set to analyse whether the trained network is able to properly represent the physico-chemical system, and hence a suitable replacement of the equilibrium model by a neuronal network is appropriate.

How to cite: Tost, H. and Spichtinger, P. and the BINARY Team: Aerosol Thermodynamics using Machine Learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5208, https://doi.org/10.5194/egusphere-egu22-5208, 2022.

Vehicle cabins are confined spaces where air quality can easily be reduced or improved by a combination of: ventilation settings, cabin air filter and route choice. By regulating the indoor-outdoor exchange rate using the vehicle's ventilation system or by opening and closing windows, occupants have the ability to self-control their exposure to both indoor and outdoor pollutants. Another important intervention to improve within-vehicle exposure to air pollution is to apply and regularly change the correct cabin air filters. Standard pollen cabin filters typically reduce small particles (i.e. fine particulate matter (PM_2.5)) from entering the vehicle's interior, effectively capturing pollen, dust, mould spores and debris, while activated carbon filters can additionally absorb some gases such as nitrogen dioxide (NO₂).

This study evaluated the impact of standard pollen and activated charcoal cabin filters on PM_2.5 and NO₂ exposure inside 10 vehicle cabins during real-world operation in Birmingham, UK. We examined five gasoline, two diesel, two hybrid and one electric vehicle on a consistent driving route on weekdays between 11:00-13:00, where PM_2.5 and NO₂ levels were measured simultaneously inside and outside of the cabin using two cross-calibrated optical particle sizer and chemiluminescent analysers respectively.

Using the appropriate ventilation settings in-cabin PM_2.5 were significantly (p< 0.05) reduced by up to 80±8.2% relative to the on-road levels. This reduction was similar for both standard pollen and activated carbon filters. No significant reductions of in-cabin NO₂ relative to the on-road NO₂ levels were found with the use of new standard pollen filters, with reductions ranging from 5.8±3.9 to 12.6±4.6%. Using new activated carbon filters, we found significant (p< 0.05) reductions of within-vehicle NO₂ concentrations relative to those measured on-road (reductions ranging from 86.1±4.7 to 94.3±3.2%). The reduction achieved remained significant when fresh air was coming into the cabin but under different fan power (medium, full) highlighting to importance of the new activated carbon filter in reducing within-vehicle NO₂ exposure. Three of the ten cars were also tested again after three months (or after 2,800-3,400 km) of the initial implementation of the new charcoal filter and the within-vehicle cabin NO₂ reductions remained almost equivalent to the initial performance (81.5±3.4 – 90.7±1.1%). In Europe 56% of the population use cars as their main transportation mean on the daily basis, therefore, employing the appropriate cabin filter can significantly reduce PM_2.5 and NO₂ levels. These exposure reductions and the resulting health benefits may be greater amongst professional drivers.

How to cite: Matthaios, V., Rooney, D., Cowell, N., Harrison, R., Koutrakis, P., and Bloss, W.: PM2.5 and NO2 exposure in different vehicle cabins with standard pollen and activated carbon filters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5501, https://doi.org/10.5194/egusphere-egu22-5501, 2022.

Although Sahara and Middle East were identified as the main sources of mineral dust in Cyprus, their chemical composition significantly differ, the latter (Middle East) being loaded not only with crustal elements but also with species from anthropogenic sources such as ammonium sulfate and carbonaceous species which made the PM mass the highest among all PM clusters and highlighting a complex dust-pollution aerosol mixture over this region.

Preliminary source apportionment results indicate a predominance of Regionally-processed factor (mainly secondary in nature) contributing alone more than 30% at the urban sites and up to 60% at the regional background station; industrial and power plant emissions from eastern Europe and Turkey being responsible for this high loading in secondary aerosol. Among the identified sources, traffic and biomass burning are mainly emitted locally (within cities) (85 and 70%, respectively). Surprisingly for a region that is strongly impact by desert dust, the share of local and regional sources was almost equal for dust (44 and 56%, respectively).

This project has received funding from the European Union’s Horizon 2020 EMME-CARE project (grant agreement N^o 856612) and the Cyprus Research and Innovation Foundation AQ-SERVE project (RIF INTEGRATED/0916/0016).

References

1. Lelieveld, J. et al. Global air pollution crossroads over the Mediterranean. Science (80-. ). 298, 794–799 (2002).

2. Lelieveld, J. et al. Loss of life expectancy from air pollution compared to other risk factors: A worldwide perspective. Cardiovasc. Res. 116, 1910–1917 (2020).

3.Paatero, P. Least squares formulation of robust non-negative factor analysis. Chemom. Intell. Lab. Syst. 37, 23–35 (1997).

4. Lenschow, P. et al. Some ideas about the sources of PM10. Atmos. Environ. 35, S23--S33 (2001).

How to cite: Bimenyimana, E., Sciare, J., Mihalopoulos, N., Oikonomou, K., Iakovides, M., Pikridas, M., Savvides, C., and Vasiliadou, E.: Characterization of PM sources in Cyprus and link with their geographical origin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5524, https://doi.org/10.5194/egusphere-egu22-5524, 2022.

The aqueous phase that serves as a reaction medium in the atmosphere, is existing in the form of clouds, fogs, rain, and particulate matter consisting of either an aqueous solution containing pollutants or a film of water surrounding. Light-induced reactions facilitate the aqueous phase photochemical reactions. It is believed that light absorbing compounds such as photosensitizers in the atmospheric have a potential influence on the atmospheric aging, growth and formation of secondary organic aerosol (SOA). However, the kinetics, products, and mechanisms of the photosensitized reactions are still poorly understood. This study was aimed to investigate the photosensitized reactions of methyl vinyl ketone (MVK), methacrolein (MACR), and methacrylic acid (MCA by excited 2-IC (imidazole-2-carboxaldehyde) in the aqueous phase. Laser flash excitation-laser long-path absorption and ultra-performance liquid chromatography coupled with high-resolution electrospray ionization spectrometry were used to investigate their kinetics and reaction product(s), respectively. The second-order reaction constants of excited imidazole-2-carboxaldehyde (2-IC) with MVK: k = (1.0 ± 0.1) × 10⁹ L mol⁻¹ s⁻¹ at pH 4 – 5 and 9, with MACR: k = (1.4 ± 0.4) × 10⁹ and k = (1.5 ± 0.1) × 10⁹ L mol⁻¹ s⁻¹ at pH 4 – 5 and 9, and with MCA: k= (1.4 ± 0.4) × 10⁹ and (1.1 ± 0.4) × 10⁸ L mol⁻¹ s⁻¹ at pH 4 – 5 and 9 were determined. Products related with the [2+2] cycloaddition of monomer and dimer of MVK to the excited carbonyl of 2-IC were observed. Similarly, a comparative study of the reaction between 3,4-dimethoxybenzaldehyde (DMB) as a photosensitizer and MVK were performed, and the second-order reaction constants with MVK: k = (1.5 ± 0.1) × 10⁹ L mol⁻¹ s⁻¹ at pH 9, with MACR: k = (1.1 ± 0.1) × 10⁹ and k = (2.8 ± 0.5) × 10⁹ L mol⁻¹ s⁻¹ at pH 2 and 9, and with MCA: k= (1.4 ± 0.4) × 10⁹ at pH 9 were obtained. This study has shown that cycloaddition of α, β-unsaturated carbonyl compounds to the excited triplet state of 2-IC or DMB potentially produced high molecular weight molecules in the atmosphere, which will provide potential insight to alleviate the discrepancy between measured and modelled results.

How to cite: Aregahegn, K. Z., Felber, T., Schaefer, T., and Herrmann, H.: Kinetics and Mechanisms of Aqueous-Phase Photosensitized Reactions of Imidazole-2-carboxaldehyde and 3,4-Dimethoxybenzaldehyde with α, β-Unsaturated Carbonyl Compounds, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5616, https://doi.org/10.5194/egusphere-egu22-5616, 2022.

Airports and air traffic can be major sources of ultrafine particles (UFP), next to other anthropogenic and natural sources. UFP are in the size range of 100 nm or less and can be either liquid or solid. When airborne, UFP can have multiple effects on climate, weather and air quality i.e. when impacting cloud formation as condensation nuclei, altering chemical processes in the atmosphere, or being aspirated or taken up.

This project investigates to what extent a large airport and the respective near-ground air traffic contribute to the overall atmospheric UFP mixture. Furthermore, we aim to elucidate the conditions that favour the accumulation of these UFP due to atmospheric transport into adjacent urban areas.

Therefore, we designed and established two monitoring stations around Munich Airport on a North-South axis. Both stations are equipped for continuously measuring UFP by means of a mobility particle size spectrometer (MPSS, 8...800 nm) and a total condensation particle counter (CPC, 8...3000 nm). The setup is completed by meteorological measurements (wind speed and direction, precipitation, solar radiation, humidity, pressure and temperature) which are crucial parameters for exploring transport and mixing of detected UFP in the lowermost atmosphere in exchange with the Earth’s surface and the multiple particle sources in the urban environment.

Officially launched in May 2021, we will present first results showing diurnal and weekly time series of UFP measurements and how they are connected to atmospheric conditions, wind speed and direction in particular as well as airport operation and other emission sectors in the surroundings.

This project is funded by the Bavarian State Ministry of the Environment and Consumer Protection (TLK01U-76519).

How to cite: Seidler, J., Friedrich, M., and Nölscher, A.: Variability of Airborne Ultrafine Particles in Number and Size at two Urban Monitoring Stations within Close Proximity to Munich Airport, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6122, https://doi.org/10.5194/egusphere-egu22-6122, 2022.

La Paz and El Alto are two high-altitude (above 3000 m.a.s.l) Bolivian cities that form part of one of the largest metropolitan areas in the country with a population of around 1.8 million people. Air quality in this conurbation is strongly influenced by both regional and local anthropogenic and natural pollution sources that have not yet been studied in this region. Moreover, despite being contiguous cities, the drastic change in altitude and topography between them leads to different production, dynamics and transport of particulate matter (PM). The need for a characterization of the pollutant sources in these sites lies not only in the importance of regulating the emissions to protect public health, but also in the observed significant impact that these pollutant sources could have on the surrounding Bolivian glaciers. PM₁₀ was collected onto 24-h filters at two background stations located in La Paz and El Alto between April 2016 and June 2017. The US-EPA Positive Matrix Factorization (PMF v.5.0) receptor model was applied for apportioning the sources that affect air quality in the two cities. This is the first source apportionment study in South America that incorporates a large set of organic markers (such as levoglucosan, PAH's, Hopanes and Alkanes) together with inorganic species. The multisite PMF allowed to resolve 11 main sources. The largest annual contribution to PM₁₀ came from 2 major sources: The ensemble of vehicular emissions, responsible for 30.3% of the measured mass (gasoline-like-powered vehicles: 16.0%; diesel-like-powered vehicles: 7.8%; non-exhaust emissions: 3.8%; Lubricant oil: 2.7%) and Mineral Dust contributing 29.7% to the total PM₁₀ mass. Other 21.9% was attributed to factors associated to secondary aerosols (NO₃-rich: 6.6%; SO₄-rich: 9.8%; MSA-rich: 5.5%). Agriculture-related smoke from biomass burning originated in the lowlands in the country and neighbouring countries contributed to 7.6% of the total PM₁₀ mass annually, this contribution doubled at the end of the biomass burning season. Primary biogenic emissions, on their side, were responsible for 6.3% of the measured PM₁₀ mass. Finally, it was possible to identify a profile related to open waste burning happening between the months of May and August. Despite the fact that this source contributed with only 4.6% to the total PM₁₀ mass, it constitutes the second-largest source of PAHs, compounds potentially hazardous for health. Running a multisite-PMF at these two high altitude sites, not only provided more robustness to the model, but also led to the dissociation of the found traffic profile into two separate vehicular sources, one for diesel and one for gasoline-powered vehicles. This study demonstrates that PM₁₀ concentrations in this Bolivian region are mostly impacted by a limited number of local sources, which is different to what is observed in many European urban areas. We conclude that traffic emissions and biomass burning are the main sources to target in order to improve air quality in both cities. Our results highlight the need for dedicated studies of air pollution in high altitude regions of South America and can serve as the start of such investigations.

How to cite: Mardoñez, V., Uzu, G., Andrade, M., Borlaza, L. J. S., Pandolfi, M., Weber, S., Moreno, I., Jaffrezo, J.-L., Besombes, J.-L., Alastuey, A., Perez, N., Močnik, G., and Laj, P.: Sources of particulate air pollution in two high-altitude Bolivian cities: La Paz and El Alto, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6183, https://doi.org/10.5194/egusphere-egu22-6183, 2022.

Atmospheric aerosols are of significant importance in climate change and health research and are essential to consider in air quality and climate modeling. Quebec is the second-largest province in Canada by population and much of the population lives in urban areas. Limitation of public activities, public transportation as well as some suspended operations of educational institutions and many commercial establishments in Quebec while severe lockdown policy was implemented, had strong repercussions on the pollutant concentration level. By analyzing a combination of air pollutants observational data (e.g. CO, SO2, PM10, O3, and NO2), this study attempts to investigate the impact of lockdown due to the COVID-19 pandemic on the pollution level of the local urban environment. Since meteorology can play an important role in air quality, the variation in diverse meteorological factors (e.g. temperature, humidity, wind, pressure, and sunlight) is evaluated as well. By separating long-term trends, seasonal signals, and meteorological contributions concerning climatology, this study estimates the relative contributions of human activities to changes in particulate concentrations. We herein discuss the implications of these results on air quality and climate modeling.

How to cite: Ashraf, S., Pausata, F. S. R., Leroyer, S., and Munoz-Alpizar, R.: Changes in Aerosols in an Urban Cold Climate During and Before the COVID-19 Outbreak, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6642, https://doi.org/10.5194/egusphere-egu22-6642, 2022.

The monitoring of airborne pollen concentrations has become of a crucial importance over the past decades, as the number of allergy sufferers is continuously increasing and the symptoms becoming more severe due to pollution and climate change.  The historical method usually used to identify pollen species present in the air and quantify them is manual with limitations such as a delay in pollen information availability and a high operational cost.

Here, we introduce a new automated solution aimed at identifying pollen grains and evaluating their concentrations based on their light scattering properties. More specifically, we introduce a low-cost and real-time optical pollen sensor named Beenose, which performs measurements at multiple scattering angles. We present an analysis of the data obtained in laboratory and the first results of the validation campaign in comparison with the historical method. Laboratory measurements were first conducted by inserting aerosols including carbonaceous particles, droplets, and different pollen species into the instrument. The collected data were then pre-processed to extract reference speciation indexes, which were used to train classification algorithms and to perform pollen identification outdoor. The results are promising and demonstrate the ability to correctly recognise some pollen species and to differentiate them from carbonaceous and droplets. In particular, among 24 species of interest, 9 are classified with an accuracy above 80%. Additionally, the total airborne pollen concentrations recorded by Beenose and the historical method are consistent. Finally, we discuss the remaining challenges to achieve a robust monitoring of the concentrations per specie and how to improve the identification of the pollen species having a similar optical behaviour.

How to cite: El azari, H., Renard, J.-B., Bleza, E.-R., Lauthier, J., and Richard, J.: Towards an automated monitoring solution of pollen concentrations using light scattering properties , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7467, https://doi.org/10.5194/egusphere-egu22-7467, 2022.

To predict the composition of the atmosphere in the context of understanding global climate change, knowledge about the formation of new aerosol particles and their growth is increasingly important. Nanometer-sized aerosol particles are initially formed by nucleation and then grow under the influence of organic molecules. Especially the small particle embryos form a unique chemical environment at the nanoscale, as they could influence chemical reactions due to their size-dependent physical properties. For example, smaller particles have higher internal pressure (Laplace pressure), which could influence reaction rates and equilibrium status in pressure-dependent reactions. In general, bond-forming chemical reactions should be favored at higher pressure, so they gain importance in small particles. Therefore, particle size-dependent chemical reactions could play a crucial role in the life cycle of atmospheric aerosols. Here we present results on Diels-Alder reactions with suitable dienes and dienophiles in nano-aerosol particles, which represent a pressure-sensitive chemical system. N-methylmaleimide as a dienophile in the particle phase and cyclopentadiene as a diene in the gas phase were chosen for their reactivity, volatility, and detectability. We study the growth and behavior of the aerosol particles and the product formation. The analysis is performed with Scanning Mobility Particle Sizer Systems (SMPS) and a GC-MS system with thermal desorption.

How to cite: Klink, D. and Hoffmann, T.: Diels-Alder-Reactions in nanometer aerosol particles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7474, https://doi.org/10.5194/egusphere-egu22-7474, 2022.

A series of experiments of NO₃ radical initiated oxidation of monoterpenes (C₁₀H₁₆) were conducted using an oxidation flow reactor (Go:PAM) combined with an iodide high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS). This study characterized the major organonitrate products from NO₃ radical initiated oxidation of Δ‑3-Carene with various levels of oxidation, i.e. by increasing the concentration of NO₃. C₁₀ monomers (products with 10 carbons) are generally the dominant products of Δ‑3-carene (e.g. C₁₀H₁₅NO₇ and C₁₀H₁₇NO₅); but where higher oxidant levels enhance fragmentation. In comparison to α-pinene, the  Δ‑3-carene oxidation has a higher propensity to create low volatile species, i.e. promote aerosol formation, mechanistically explained by difference in alkoxy radical (RO) bond scissions. A kinetic model (using FACSIMILE) was developed to simulate the formation of dominant products. The mechanism was based on analogue systems within the Master Chemical Mechanism (MCM) and recently available literature. The fate of RO₂ under different chemical regimes was also investigated by comparing model runs and the experimental results.

How to cite: Li, L., Mark Salvador, C., Priestley, M., Tsiligiannis, E., and Hallquist, M.: NO3 radical initiated oxidation products of Δ-3-carene: Characterization and mechanism of formation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7512, https://doi.org/10.5194/egusphere-egu22-7512, 2022.

Regardless of decades of convincing epidemiological evidence, large uncertainty remains regarding the physical and chemical characteristics of aerosols, as well as the toxicity mechanisms upon exposure to human health.
Oxidative potential (OP) is defined as the capability of particles to catalytically produce reactive oxygen species (ROS) with subsequent depletion of anti-oxidants, naturally present in the human lung. OP has been widely suggested as a measure of the potential toxicity of aerosols, but suitable instruments, especially for continuous field deployment are lacking. Due to the circumstance that ROS (i.e. inorganic and organic peroxides and radicals) are highly reactive, they are therefore short-lived. Thus, classical offline analysis, where aerosol particles are typically collected on a filter for 24h or longer prior to analysis, may lead to an underestimation of the oxidative potential.
Therefore, we developed an online instrument that can continuously measure particle oxidative potential with immediately sampling of particles, and 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 and thus toxicity of aerosol particles.
In this work, we present the overall design and operation of the OOPAAI (Campbell et al., 2019, Anal. Chem.). Recent improvements are also discussed where we further developed the OOPAAI into a field-deployable instrument with an improved continuous flow cell for fluorescence detection, a particle to liquid sampler with a higher efficiency and optimizations of the chemical reaction system to ensure that the ascorbic acid assay is stable and buffered at pH 6.8. These technical developments of the OOPAAI improved its detection limit, operational stability and physiological relevance.
A range of laboratory flow tube studies were conducted to identify the OP of secondary organic aerosols (SOA) from naphthalene and beta-pinene and metal particles (Fe and Cu). A range of synergistic and antagonistic effects was observed when the OP of mixtures of metal and SOA particles was quantified.
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 oxidising aerosol properties and their potential effect on human health. Moreover, in lab-based experiments the OOPAAI helps to gain better understanding of fundamental interaction between different aerosol types like organic aerosols and transition metals and their influence on OP and hence their potential toxicity.

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., Campbell, S. J., Barth, A., Gfeller, B., Bukowiecki, N., and Kalberer, M.: Oxidative Potential of Transition Metals and Secondary Organic Aerosols using an Online Oxidative Potential Ascorbic Acid Instrument (OOPAAI) to Quantify Aerosol Toxicity , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8206, https://doi.org/10.5194/egusphere-egu22-8206, 2022.

Large-scale forest fires often occur in Indonesia and affect air quality and human health. The effect of forest fire on air quality quantified by rising PM₁₀ concentration on Indonesia Meteorological, Climatological and Geophysical Agency (BMKG) observation network. A few PM₁₀ observation networks and uneven distribution in Indonesia make it difficult to present spatial ground-level PM₁₀.  The aim of this study was to estimate ground-level PM₁₀ in Indonesia and present the spatial distribution of ground-level PM₁₀ using machine learning. Support Vector Regression (SVR) techniques were used to estimate the PM₁₀ content from heterogeneous data sources, including ground measurements provided by BMKG, numerical model data, and hotspot retrieved from NASA/LANCE – FIRMS for satellite imagery. RMSE and MSE were used to evaluate the estimation result. We also present the modeling framework on the forecast of the CAMS Copernicus model in Indonesia. The performance of various input parameter configurations of SVR for estimating the ground-level PM₁₀ as indicated by low prediction errors.

How to cite: Permana, D. S., Fajariana, Y., Aprilina, K., Nuryanto, D. E., Linarka, U. A., Panjaitan, A., Riama, N. F., Sopaheluwakan, A., Munggaran, M. R., and Karnawati, D.: Spatial Ground-Level Particulate Matter (PM10) in Indonesia using Machine Learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8225, https://doi.org/10.5194/egusphere-egu22-8225, 2022.

Atmospheric pollution is a significant cause of oxidative stress in the human pulmonary system. (1–3) Fine particulate matter (PM_2.5) has been linked to adverse health effects due to the size and composition of particulates. Gas-phase chemical species, such as ozone, have also been considered as significant pollutants posing threat to human health.(3-4) However, other reactive gas-phase species, such as peroxides, have hardly been examined.

The epithelial lining fluid (ELF) is a large interface between the atmosphere and human body.(5) Transition metals enter the ELF through inhalation of PM_2.5 and play a key role in the potential occurrence of health effects. In the presence of transition metals, peroxides such as hydrogen peroxide (H₂O₂) are converted into the highly reactive OH radical through Fenton chemistry. Due to its high reactivity, the OH radical is most likely to cause oxidative stress and Fenton chemistry is probably an important OH source in the lung.(6) High levels in both, peroxide and transition metal concentrations in the ELF, could thus have adverse health outcomes.

We investigate the role of the most abundant atmospheric peroxide, H₂O₂, in the formation of reactive oxygen species (ROS: H₂O₂, OH, O₂^-, HO₂)(5) in the human body using a kinetic multilayer model. We find that, besides ambient concentrations, transport to and from lung cells and the circulatory system affects H₂O₂ levels in the ELF and, accordingly, exhaled breath condensate (EBC). The model predicts levels of H₂O₂ in EBC, lung cellular space, and blood, in agreement with the literature. The H₂O₂ concentration in the ELF, where measurements cannot be conducted easily, can be inferred from the model and used to estimate air pollution-induced ROS production in the human body. We present scenarios of atmospherically relevant conditions of H₂O₂ and PM_2.5 pollution in urban and rural areas and simulate the effect of co-inhalation of H₂O₂ and PM_2.5 on ROS production in the ELF. We discuss the hypothesis whether accumulation of H₂O₂, either by inhalation or in-body transport, may be a prerequisite for PM_2.5 toxicity

1. R. A. Silva, et al., The effect of future ambient air pollution on human premature mortality to 2100 using output from the ACCMIP model ensemble. Atmos. Chem. Phys. 16, 9847–9862 (2016).

2. H. Zhao, et al., Effects of atmospheric transport and trade on air pollution mortality in China. Atmos. Chem. Phys. 17, 10367–10381 (2017).

3. H. J. Forman, C. E. Finch, A critical review of assays for hazardous components of air pollution. Free Radic. Biol. Med. 117, 202–217 (2018).

4. P. S. J. Lakey, et al., Chemical exposure-response relationship between air pollutants and reactive oxygen species in the human respiratory tract. Sci. Rep. 6, 1–6 (2016).

5. H. Sies, Oxidative stress: A concept in redox biology and medicine. Redox Biol. 4, 180–183 (2015).

6. S. Lelieveld, et al., Hydroxyl Radical Production by Air Pollutants in Epithelial Lining Fluid Governed by Interconversion and Scavenging of Reactive Oxygen Species. Environ. Sci. Technol. 55, 14069-14079 (2021).

How to cite: Dovrou, E., Lelieveld, S., Mishra, A., Pöschl, U., and Berkemeier, T.: The influence of atmospheric and cellular H2O2 on ROS concentrations and OH radical production in the lung, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8379, https://doi.org/10.5194/egusphere-egu22-8379, 2022.

Organic aerosols (OAs) have a significant effect on Earth’s climate due to their radiation scattering properties and potential to be cloud condensation nuclei. OAs occur naturally from biological processes and biomass burning, but anthropogenic sources such as fossil fuel burning, residential biomass burning and pollution add to the presence of organic compounds in the atmosphere.

In this work we present data from a sampling campaign aimed at investigating the concentrations of nanoplastics and organics on the snow surface in remote Alpine areas. Surface snow samples from 13 locations in the Swiss and French Alps were collected in August 2021 during reconnaissance for an expedition in June 2022. The samples were taken from glaciers at altitudes between 1880 and 3550 m and as far as possible away from areas trafficked by mountaineers. The sampling was performed by mountaineers acting as citizen scientists, and analysis of blank purity proved that well-trained citizens can be a good recourse for high-quality sample access, especially in difficult-to-access mountain locations.

Upon arrival at Utrecht University, the snow samples were filtered through a 1 μm PTFE filter before being analyzed using Thermal Desorption - Proton Transfer Reaction - Mass Spectrometry (TD-PTR-MS). This method analyzes semi- and non-volatile organic compounds in the snow samples, which includes unique tracers for biomass burning (e.g. vanillic acid and levoglucosan), biogenic organic aerosols (e.g. pinonic acid) and nanoplastic pollution (e.g. polypropylene, polyethylene terephthalate, polyethylene, polystyrene, polypropylene carbonate, and polyvinyl chloride). Further processing will reveal the total organic carbon content, presence of nanoplastics of different polymer types, and the oxidative state of the carbon in the samples.

How to cite: Notø, H., Materić, D., Gill, A. J., Milner, R., and Holzinger, R.: Chemical Analysis of Organic Aerosol Particles and Nanoplastics Deposited on Alpine Glaciers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8494, https://doi.org/10.5194/egusphere-egu22-8494, 2022.

Airborne particles affect air quality, weather and climate. The continuing urbanization is expected to expose a growing fraction of the world’s population to still increasing levels of anthropogenic emissions of airborne particles and precursors of secondary aerosols. These anthropogenically emitted particles are dominated in number by ultrafine particles (UFP; diameter less than 100 nm), which therefore are common in urban air. Their size and chemical composition determine whether the particles impose a risk to human health or the environment. Thus, in-depth knowledge about airborne UFPs' sources and atmospheric fate is essential for environmental risk assessment. A detailed chemical analysis of UFPs aids to better understand environmental processes in the atmosphere and possible effects on human health.

Despite the need of learning more about the origin, behaviour, mobility, fate, and toxicity of UFPs, attempts to analyze their chemical composition in the atmosphere are still rare. Considering their low mass, partial volatility and dynamic character, it is still a great challenge to separate, catch and analyze UFPs in the atmosphere.

Impactors are important tools to separate and collect environmental particles from the air with the aim of analyzing their chemical composition. Herein, we report our evaluation of commercially available and frequently deployed cascade impactors for their applicability of sampling airborne UFPs. We tested the following criteria: (1) A precise size separation or cut‑off in the ultrafine range to enable size-dependent chemical analysis, (2) The collection of the greatest as possible particle mass (high sampling volume) while minimizing evaporation losses of semi-volatile fractions (small pressure drop). Therefore, different impactors were connected in line between a customizable particle generation source, a flow reactor for dilution, mixing and ageing, and a mobility particle size spectrometer (MPSS). So far, our results indicate a significant variability among impactors of the same model and highlight the difficulty of combining all these requirements in one device. However, after careful physical characterization, we developed a strategy to optimize the particle sampling for atmospheric UFPs chemical composition analysis.

This project is financed by the Bavarian Ministry of the Environment and Consumer Protection.

How to cite: Eckenberger, E., Das, A., Gawlitta, N., Kernchen, S., Orasche, J., Schnelle-Kreis, J., Sklorz, M., Jakobi, G., Zimmermann, R., and Nölscher, A. C.: Catch me if you can: Evaluating sampling methods for airborne ultrafine particles’ composition analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8803, https://doi.org/10.5194/egusphere-egu22-8803, 2022.

Fine particulate matter or PM_2.5 varies greatly in space and time depending on the profile of its emission sources, geographical terrain, and meteorological conditions. While the spatiotemporal variability of PM_2.5 over larger regions has been well studied, in this study we focus particularly on the neighborhood-scale spatial variations of PM_2.5 within the megacity of Delhi by exploiting hourly observations from 23 ground-based stations within the city for the post-monsoon and winter period. First, we derive the difference between the PM_2.5 concentrations at most polluted and least polluted stations and find their correlation against the average PM_2.5 in the city at both hourly and daily timescales. We find significant correlations between the maximum difference and average concentration for all three months. The differences between stations are generally higher in November and December as compared to October for the same average PM_2.5 concentrations. Overall, the most frequent maximum difference between stations is found to be 75 µgm-3 at hourly scale and 100 µgm-3 at daily scale. There are several instances of maximum difference of PM_2.5 concentrations between stations exceeding 300µgm-3, which highlights the disparity between the neighborhoods. Second, we found that, on average, the maximum and minimum difference in PM_2.5 occur at 2am (176 µgm^-3) and 3pm (37 µgm^-3) for October, 6am (400 µgm^-3) and 6pm (45 µgm^-3) for November and 6pm (200 µgm^-3) and 7am (104 µgm^-3) for December respectively. We hypothesize that the low difference across stations in the afternoons in October and November is due to increased boundary layer mixing at this time of the day. This concentration parity across neighborhoods is not achieved in the afternoons of December due to relatively low boundary layer height even during daytime. To confirm this, we performed WRF model simulations at 1km spatial resolution over Delhi for the three-month period to derive station-specific boundary layer height. Third, we calculated hourly concentration gradients (in µgm^-3 per km) between each station by dividing the difference between their concentrations by their physical distance. We found the highest concentration gradient for each day along with its vector (direction) and time of the day when it occurs. We finally identified the most persistent vector along which PM_2.5 concentrations change most quickly. Our results highlight the tremendous air pollution disparity between neighborhoods in the megacity of Delhi and stress the need for more granular, neighborhood-scale air quality early warning systems to protect public health.

How to cite: Taksibi, F. and Ansari, T.: Understanding neighborhood scale variability of fine particulate matter in megacity Delhi during post-monsoon and winter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9142, https://doi.org/10.5194/egusphere-egu22-9142, 2022.

The ionization caused by Cosmic Rays (CR) in the atmosphere can influence the growth of aerosols that will modify the density of cloud-condensation nuclei (CCN). In fact, the flux of CR in the atmosphere has been reported to correlate with cloud and aerosol properties. Several mechanisms have been proposed and tested to explain this effect, leading to the conclusion that the induced effects were minor. Still, these studies did not completely disprove the link between CR and clouds (i.e., climate). Since then, different mechanisms that could be relevant to aerosol growth have been proposed. One of them is the diffusion-charging mechanism by which aerosols acquire charges by diffusion of atmospheric ions onto their surface.  Charging and aerosol coagulation can influence each other and impact the particle charge and size distributions in the atmosphere. Previous works have developed approaches to explicitly solve all the equations governing charge and size distribution in particles. However, since aerosols can acquire a large number of charges, the number of equations to solve would be immense and very computationally expensive. Fortunately, other approaches have also been developed that allow diffusion charging to be implemented more efficiently. In this work, we use for the very first time a global chemistry transport model (GEOS-Chem) to implement the effects of diffusion charging from CR on the microphysical development of aerosols following those approaches. We compare the variations of CCN concentrations between the solar maximum and the solar minimum (i.e., different atmospheric ionization scenarios) to test the sensitivity of the effect. Results indicate that the influence of diffusion charging can be relevant under several atmospheric conditions. In such cases, the change in the concentrations of CCN between the solar maximum (high cosmic-ray flux) and the solar minimum (low cosmic-ray flux) is found to be larger than 1%, which may become relevant for cloud formation. 

How to cite: Riádigos, I., Marais, E., Pierce, J., and Pérez Muñuzuri, V.: The impact of charged aerosols on cloud-condensation nuclei formation with GEOS-Chem, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9439, https://doi.org/10.5194/egusphere-egu22-9439, 2022.

Air pollution is responsible for a major part of environmental-related health impacts on humans. Aerosol particles in the inhalable size range account for the largest contribution. To improve air quality with targeted measures, it is necessary to precisely identify and minimise the emission sources of airborne particles. Data with high temporal resolution on the size fractionated chemical composition is of great value in this context, as it allows conclusions to be drawn about the emission sources of the particles.

Conventionally conducted filter samplings with subsequent chemical analysis of the collected aerosol particles usually cannot provide high time resolution, as the analytical methods used so far require a minimum amount of sample material.

Here, the development of a measurement approach that analyses aerosol particles using Total Reflection X-ray Fluorescence (TXRF) is presented. TXRF analysis is based on the reflection of a shallow incident X-ray beam on a reflective sample carrier loaded with aerosol particles. A high detection sensitivity for elements of high atomic numbers with a minimum sample quantity required characterises this method.

Particle collection is conducted by means of an impactor optimised for the measurement geometry of the TXRF spectrometer. Aerosol size fractions are deposited directly on the TXRF sample carrier for subsequent analysis. TXRF analysis can be performed by a compact tabletop device, which is also portable for use in the field directly after particle collection.

The coupling of a commercially available cascade impactor with a TXRF spectrometer has shown a high potential of this method. We further improve this by developing a cascade impactor specifically optimised for a TXRF spectrometer, in order to achieve the lowest possible detection limits. In our contribution, we present first TXRF analysis results of particles collected from outdoor air in Berlin using a prototype cascade impactor and outline the advantages as well as the challenges of this analytical approach.

How to cite: Crazzolara, C., Waldschläger, U., and Held, A.: Preliminary results of metal content analysis in the outdoor air of Berlin using an impactor prototype optimised for TXRF analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9567, https://doi.org/10.5194/egusphere-egu22-9567, 2022.

The atmospheric lifetime of a common fatty acid cooking emission, oleic acid, is longer than what is predicted by laboratory experiments. This could impact on the cloud condensation nucleus (CCN) ability of an aerosol via oleic acid’s role as a surfactant. Oleic acid can self-organise into a range of viscous phases which we showed can have a significant impact on its rate of reaction with the common atmospheric oxidant, ozone. We established this using a number of synchrotron X-ray and neutron experiments which probed this self-organised proxy system from the nanometre to the micrometre scale as levitated particles and coated films. We supported our findings with kinetic multi-layer modelling of these results to demonstrate that the atmospheric lifetime of oleic acid could increase by an order of days upon viscous self-organised phase formation.  There are implications not only for cloud formation and the climate, but more persistent viscous organic material could contribute to the protection of harmful compounds found co-existing with fatty acids in aerosol samples.

How to cite: Milsom, A., Squires, A., and Pfrang, C.: The impact of viscous self-organised phase formation on the lifetime of a fatty acid aerosol proxy: nanometre films to micrometre particles, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9959, https://doi.org/10.5194/egusphere-egu22-9959, 2022.

Various natural and anthropogenic activities generate atmospheric sulfur and carbon aerosol which in turn has an adverse effect on human health, climate change and visibility [1], [2]. Man-made sources of aerosol include power plants, vehicular traffic, domestic heating, biomass burning and other industrial emissions. The stable isotope ratio analysis of bulk aerosol material provides valuable information on the origin of its constituents but a combination of stable isotope and radiocarbon techniques allows for an even greater level of differentiation [3].

The aim of this work was to employ stable carbon and sulfur isotope ratio analysis together with radiocarbon data in apportionment of aerosol sources. The collection of aerosol PM₁ samples was performed in Vilnius, Lithuania during a period of 5 months. Stable isotope δ³⁴S and δ¹³C values were measured with a stable isotope mass spectrometer and ¹⁴C measurements were done using a single stage accelerator mass spectrometer. Simple isotope mixing equations were applied to stable isotope and radiocarbon data to distinguish inputs of biomass, traffic and coal sources of carbonaceous aerosol. By comparing calculated source fractions to δ³⁴S values we find that biomass and coal combustion were dominant sulfur aerosol pollutants. In addition, average contributions of coal and fossil combustion, biogenic, soil emissions to sulfate aerosol were evaluated. Finally, the preceding results together with total carbon and sulfate concentrations were related to HYSPLIT air mass back trajectory plots. Such an approach allows for a comprehensive description of sulfur and carbon aerosol pollution sources.

[1]          C. A. Pope and D. W. Dockery, "Health effects of fine particulate air pollution: Lines that connect", J. Air Waste Manag. Assoc., t. 56, nr. 6, 2006.

[2]          C. Tomasi, C. Lanconelli, M. Mazzola and A. Lupi, "Aerosol and Climate Change: Direct and Indirect Aerosol Effects on Climate", Atmospheric Aerosols, 2016.

[3]          I. Garbarienė et al., "Origin identification of carbonaceous aerosol particles by carbon isotope ratio analysis", Aerosol Air Qual. Res., 2016.

How to cite: Bučinskas, L., Garbarienė, I., Šapolaitė, J., Ežerinskis, Ž., and Garbaras, A.: A dual stable isotope and radiocarbon approach for apportionment of aerosol sources, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10010, https://doi.org/10.5194/egusphere-egu22-10010, 2022.

Fossil fuel emissions contribute huge amount of carbonaceous aerosols into the air which plays an important role in the climate change. The carbonaceous aerosol especially organic carbon (OC) and elemental carbon (EC) affect radiative forcing of the Earth. Therefore, the present study was carried out at an unexplored urban site in Saharsa district of Bihar state in India. The aerosol samples were collected during monsoon period (June-September 2019) to study day and night time variation of OC, EC and water soluble organic carbon (WSOC). The average concentration of EC during day time was noticed as 6.8 µg/m³ while during night time as 8.5 µg/m³. The average concentration of OC during day time was noticed as 9.1 µg/m³ while during night time as 13.7 µg/m³. On an average the night time concentrations of OC and EC were almost 25% higher than their day time concentrations. . The concentration of fine particulate matter was found to be higher during the night time as compared to the day time. OC/EC ratios were relatively lower than the standard value considered for biomass burning as a sources which suggested that the sources were mostly of fossil fuel burning type, probably thermal power plant and automobile exhaust. The average ratio during day time and night time was noticed to be 1.45 and 1.65 suggesting the dominance of EC which also indicated fossil fuel burning, the major source of carbonaceous aerosol at the site. The average WSOC/OC ratio was found to be same during both day and night time due to the formation of secondary organic aerosols. The average concentration of total carbonaceous aerosols accounted for about 24% of the total fine particulates during day time and about 18% of the total fine particulates during night time indicating more prominent carbon emission activity during day time.

Keywords: Carbonaceous Aerosol, Organic Carbon, Elemental Carbon, WSOC, Total Carbonaceous Aerosols.

How to cite: Roy, A.: Atmospheric Abundance Of EC, OC And WSOC During Day And Night Time At An Urban Site Of Bihar State (INDIA), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10103, https://doi.org/10.5194/egusphere-egu22-10103, 2022.

The importance of bio-aerosols across the earth system has been known for some time. With the unfortunate situation arising from the COVID19 pandemic, attention has turned to appropriate detection technologies that could be used to better understand the contribution of aerosols generated from the lung in various settings. In this project, the wideband Integrated Bioaerosol Sensor (WIBS-NEO) was deployed in a zero-background clinical environment which permitted the aerosols measured to be directly ascribed to specific vocalisations undertaken. The fluorescent signatures of expelled aerosol from a variety of human participants were captured during individual speech and language therapy activities (speaking, humming, sustained phonation, fricatives, projection, and tongue trills). In this presentation we present the varying fluorescent signatures and particle morphologies.

Furthermore, millions across the UK have now adopted face coverings into their day to day lives with one of the most widely adopted and commonplace being the disposable surgical face mask. Yet, questions still remain as to what types of vocalisations produce the most aerosols and the efficacy of the face mask in reducing transmission. To supplement this, measurements with the WIBS-NEO were conducted where participants did not wear a mask, and then subsequently repeated wearing a surgical mask. The fluorescent intensity, concentration (cm³), size (um), and asphericity were then compared for each activity with and without a mask.

WIBS-NEO information:

https://www.dropletmeasurement.com/product/wideband-integrated-bioaerosol-sensor/

Example paper using the WIBS:

E.Toprak and M. Schnaiter, Atmos. Chem. Phys., 2013, 13, 225–243.

How to cite: Moss, M., Topping, D., Reid, J., Harrison, J., Archer, J., Szczepanska, A., Bzdek, B., Saccente-Kennedy, B., Epstein, R., Costello, D., Calder, J., and Shah, P.: Fluorescent Characteristics of respiratory aerosol generated by a variety of speech and therapy activities., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10175, https://doi.org/10.5194/egusphere-egu22-10175, 2022.

Fine particulate matter (PM) affects visibility, climate, and public health. Biomass burning (BB) in the forms of residential wood burning, wildfires, and prescribed burning is a major source of primary and secondary organic matter (OM, an important fraction fine PM), and brown and black carbon (BrC and BC). The contribution of BB to the atmospheric fine PM is only expected to increase in the foreseeable future. Recent studies have highlighted the enhancement in the biomass burning organic aerosol (bbOA) concentrations with aging and reported on the chemical composition of the secondary biomass burning organic aerosol (bbSOA) formed under different conditions. However, the chemical processing of the primary biomass burning organic aerosol (bbPOA) with aging is not well characterized. This chemical processing can potentially alter the chemical composition of bbOA drastically and render its identification and quantification in the atmosphere difficult.

             We used aerosol mass spectrometry (AMS) and Fourier transform infrared spectroscopy (FTIR) as two complementary methods to quantify the bbPOA aging in this study. AMS measures the bulk composition of OM with a relatively high temporal resolution but provides limited parent compound information due to the extensive fragmentation. FTIR, carried out on PTFE filter samples, provides detailed information about the functional group composition of the OM and certain bbOA makers at the expense of a relatively low temporal resolution. In a series of aging experiments at the Center for Studies of Air Qualities and Climate Change (C-STACC), primary emissions from wood and pellet stoves were injected into an environmental simulation chamber. Primary emissions were aged using hydroxyl and nitrate radicals simulating the atmospheric day-time and night-time oxidation.  A high-resolution time-of-flight (HR-TOF) AMS was used to identify the composition of non-refractory PM₁. PM₁ was also collected on PTFE filters before and after aging for the off-line FTIR analysis.

                AMS and FTIR agreed well in terms of the measured bbOA mass concentrations, elemental ratios, and the evolution of biomass burning tracers. We developed a procedure to quantify the bbPOA aging using AMS and FTIR. Using AMS, we found that up to 17 % of the bbPOA mass underwent some form of transformation with aging. This transformation was more intense under day-time conditions. FTIR detected a more extensive oxidation (up to two times that of AMS), suggesting a substantial processing of bbPOA, and revealing the limitations of AMS to capture bbPOA aging due to the extensive fragmentation. Different bbOA-related ion fragments were observed to decay at different rates under different conditions (e.g., oxidants and relative humidity). These different decay rates can potentially be used to identify the extent of bbPOA aging in the atmosphere. The bbSOA formed during the daytime oxidation was dominated by acid contributions, resembling certain atmospheric biomass burning samples. The unique, acid-dominated FTIR spectrum of bbSOA can potentially be used as another indicator of the aged bbOA in the atmosphere.

How to cite: Takahama, S., Yazdani, A., Kodros, J., Paglione, M., Masiol, M., Squizzato, S., Florou, K., Kaltsonoudis, C., Jorga, S., Pandis, S., and Nenes, A.: Chemical evolution of primary and secondary biomass burning aerosols during daytime and nighttime, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10738, https://doi.org/10.5194/egusphere-egu22-10738, 2022.

Atmospheric aerosols are an important part of Earth’s climate system. Further, they have great influence on air quality and human health. Secondary organic aerosols (SOA) generated from the oxidation of volatile biogenic precursors are an important contributor to the global aerosol budget. Therefore, understanding new particle formation and their subsequent growth is critical for our ability to predict the atmospheric aerosol composition and global climate change.

The coupling of a chemical ionization source with an Orbitrap mass spectrometer provides soft ionization and a high mass resolution for the on-line measurements of laboratory-generated SOA. Through heating of the aerosol, it is possible to measure both the gas phase and the vaporized particle phase. We use this technique to compare the chemical composition of particles produced from the oxidation of -pinene and -carene. Although exhibiting a very similar chemical structure, they differ greatly in their resulting SOA, in terms of particle size and number concentration when oxidized with ozone in smog-chamber experiments.  

These differences lie in their abilities to form characteristic SOA precursors, which depending on their chemical structure, promote either new particle formation or the growth of existing ones. The extremely low volatile organic compounds (ELVOCs) required for these processes are generally believed to be formed by gas phase chemistry. However, newly formed particles provide a unique nanoscale chemical environment that affects chemical reactions in the condensed phase and heterogeneous reactions on their surface, making them a potential source of ELVOCs as well. The increasing pressure inside the particles with decreasing diameter (Laplace pressure) favors bond-forming reactions. The lower viscosity in nanometer-sized particles further promotes reactions within the particle and increases reactivity at the particle surface such as heterogeneous oxidation. We show the particle size-dependent heterogeneous oxidation in a model system and ongoing work on other size-dependent reactions.

How to cite: Douverne, M., Böckmann, M., Thomsen, D., Riva, M., Perrier, S., George, C., Glasius, M., and Hoffmann, T.: Characterization of organic aerosols by online CI-Orbitrap MS: Laboratory studies of biogenic SOA formation and size-dependent aerosol chemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11038, https://doi.org/10.5194/egusphere-egu22-11038, 2022.

Mineral dust is amongst the largest contributors to the global aerosol mass load and dominates climate effects over large areas of the Earth. Dust undergoes heterogeneous chemical reactions during transport that increase its hygroscopicity, while altering its optical properties, and the associated radiative forcing. The rates of heterogeneous chemical reactions on the dust surface that form coatings of sulfate, nitrate, chloride, or organics depend strongly on the dust mineralogical composition. For example, the uptake of sulfur dioxide by calcite exceeds by at least an order of magnitude uptake by quartz, feldspar and hematite. Dust composition also affects the partitioning of semi-volatile inorganic compounds, altering their burden and radiative forcing.

In this work, we perform an analysis of the treatment of nitric acid heterogeneous chemistry on mineral dust in atmospheric models. We have implemented aerosol nitrate formation on coarse particles in the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (MONARCH) and we have performed sensitivity experiments with parametrizations of varying complexity. First-order uptake reactions with/without dependence on relative humidity are compared against approaches based on thermodynamic equilibrium assumptions, that range from just considering the effect of dust mineralogy upon aerosol pH to including the formation of subproducts from the gas-mineral interaction. The sensitivity to the mineral dust treatment (i.e., minerological composition) in each approach is discussed. The different implementations are evaluated against observations and compared with literature results.

Our preliminary findings highlight the important role that mineralogy plays in mineral dust chemistry, and the relevance that thermodynamic assumptions have when simulating the complex evolution of mineral dust in the atmosphere. This work aims to set a benchmark for future sensitivity studies to factors affecting dust heterogeneous chemistry, such as the explicit representation of regional variations in the mineralogical composition of dust.

How to cite: Soussé Villa, R., Jorba Casellas, O., and Pérez García-Pando, C.: Modelling nitric acid uptake by mineral dust using parameterizations of different complexity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11622, https://doi.org/10.5194/egusphere-egu22-11622, 2022.

Over the last few decades, Greater Cairo Megacity has experienced rapid population growth and expansion of its industrial activity. Hosting more than 20 million people, Cairo is considered one of the most polluted megacities in the world. Concentration levels of fine particulate matter (PM_2.5) are several times higher than those recommended by the World Health Organization (WHO). Although actions have been designed recently to improve air quality in the framework of a “Pollution Management and Environmental Health program” (PMEH) supported by the World Bank, observational studies assessing the main sources leading to this PM pollution are missing, making difficult to implement and monitor the efficiency of local mitigation strategies.

The aim of our study is to investigate atmospheric concentrations levels, temporal variability, as well as major sources, and atmospheric aging of PM in Cairo megacity with a focus on the submicron aerosol fraction (PM₁) to better assess human-made activities with lower interference from natural (dust) emissions. A comprehensive suite of on-line and off-line instruments has been set-up to monitor PM₁ chemical composition and reactive trace gases (i.e. Volatile Organic Compounds) as a part of the POLCAIR campaign that took place during winter 2019-2020, at an urban background site in Greater Cairo. Chemical composition of PM₁ and source apportionment analysis via Positive Matrix Factorization (PMF) on both Q-ACSM (Aerosol Chemical Speciation Monitor, Aerodyne, US) organic mass spectra and co-located filter samples, attributed exceptionally high concentrations of compounds to traffic emissions and diverse combustion sources with pronounced diurnal variability. Two severe pollution episodes were recorded, with hourly mean PM₁ concentrations reaching values as high as 300 μg/m³ and lasting for 2 consecutive days favored by low dispersion conditions. Pollutant variability is directly associated with the meteorological conditions, including wind patterns and air mass origins. This helps in recognizing emission hot spots of major anthropogenic PM₁ sources. Additionally, the effects of the relative humidity and the role of heterogeneous oxidation reaction mechanisms was investigated. Finally, the multi-variable analyses performed, helped us to better investigate the complex urban atmospheric chemistry in Cairo megacity and to highlight the dynamics of Secondary Organic Aerosol formation.

How to cite: Christodoulou, A., Stavroulas, I., Bourtsoukidis, E., Pikridas, M., Bezantakos, S., Hassan, S., El-Nazer, M., Wheida, A., Wahab, M., Boraiy, M., Borbon, A., Afif, C., Sauvage, S., and Sciare, J.: Sources and atmospheric aging processes of submicron aerosols in Cairo Megacity., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12038, https://doi.org/10.5194/egusphere-egu22-12038, 2022.

In urban areas, secondary organic aerosol (SOA) generated from anthropogenic volatile organic compounds (AVOC) like toluene can contribute largely to the aerosol particle formation. However, it is still unclear how the temperature and gas species affect toluene SOA formation and optical properties. Therefore, we simulated toluene SOA formation in Aerosol Interaction and Dynamics in the Atmosphere (AIDA) chamber under the temperatures of 253-313K and with the addition of different gas species (NO₂, SO₂, and NH₃).

In all experiments, toluene SOA bulk was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-MS). Toluene and less oxygenated organic aerosol were measured with Proton Transfer Reaction Mass Spectrometry (PTR-MS) coupled with a particle inlet (CHemical Analysis of aeRosol ON-line Proton, CHARON). Furthermore, aerosol particles were collected on filters and analyzed in the laboratory. On the one hand, filter particles were extracted by pure methanol and the extracted solution was measured by AquaLog, which can investigate light absorption and fluorescence. Meanwhile, light absorption was measured with two Aethalometers (AE33 and MA200) and three-wavelength photoacoustic (PAS). On the other hand, 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), which investigate the molecular composition of oxygenated organic aerosol compounds. We will discuss the mass absorption efficiency, chromophore variations of toluene SOA in different conditions, and the absorption contribution from specific organic molecules will be studied as well.

How to cite: Jiang, F., Saathoff, H., Song, J., Gao, L., Gong, Y., Linke, C., Thomas, L., and Norra, S.: Effect of temperature and gas species on toluene secondary organic aerosol: light absorption, chromophores, and chemical compositions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12727, https://doi.org/10.5194/egusphere-egu22-12727, 2022.

The molecular composition of atmospheric particulate matter in the urban environment appears as extremely complex, and it remains a grand challenge to identify its sources and formation pathways. In this study, we applied a novel nontarget analysis to HPLC/(−)ESI-HRMS measurements of yearlong PM_2.5 filter samples from Beijing, and represent all detected compounds in comprehensive molecular fingerprints. Additionally, we used a hierarchical clustering analysis (HCA) for complexity reduction of the large dataset. The Van Krevelen-diagram indicate that the major compound clusters exhibit a unique molecular pattern. We found that organic aerosol (OA) in Beijing during summer features a higher degree of oxidation and a higher proportion of organosulfates (OSs) in comparison to OA during wintertime, which exhibits a high contribution from (nitro-)aromatic compounds. OSs appeared with a high intensity in summer-haze conditions, indicating the importance of anthropogenic enhancement of secondary OA in summer Beijing. We estimated the quantitative contribution of the main compound clusters to total OA based on calibrations using surrogate standards. With this approach, we are able to explain a small fraction of the OA monitored by the Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM). However, we observe a strong correlation between the sum of the quantified clusters and OA measured by the ToF-ACSM, indicating that the identified clusters represent the major variability of OA seasonal cycles. This study highlights the potential of using nontarget screening in combination with HCA for gaining a better understanding of the molecular composition and the origin of OA in the urban environment.

How to cite: Ma, J., Ungeheuer, F., Zheng, F., Du, W., Wang, Y., Cai, J., Zhou, Y., Yan, C., Liu, Y., Kulmala, M., Daellenbach, K., and Vogel, A.: Nontarget screening exhibits a seasonal cycle of PM2.5 organic aerosol composition in Beijing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12735, https://doi.org/10.5194/egusphere-egu22-12735, 2022.

The concentration of nitrogen oxides (NOx) and their reservoir species, the organonitrates (ON), impacts on the secondary organic aerosol (SOA) production. To estimate the effect of different NOx levels on SOA, we carried out a series of laboratory experiments at the Harvard Environmental Chamber (HEC) investigating the production and partitioning of total organonitrates from α-pinene photo-oxidation in a NOx range varying between 1 ppb and 24 ppb. We measured not only the aerosol mass concentration by using a Scanning Mobility Particle Sizer (SMPS) and composition by an on-line aerosol mass spectrometry (AMS), but also the gas phase and particle-phase organonitrates (gON and pON, respectively) by a thermal dissociation laser-induced fluorescence (TDLIF). In our experimental conditions, we found the presence of crossover point of 6 ppb of NOx between clean and polluted conditions that affect the SOA production: in fact, the SOA yield for 1 to 6 ppb NO_x increased, and for >6 ppb NO_x steadily dropped. The ON partitioning ratio (pON/(pON+gON)) has been estimated, identifying that also this ratio is strongly affected by the NOx concentrations; in fact, it decreased from 0.27 to 0.13 as the NO_x increased from <1 to 24 ppb. 

How to cite: Aruffo, E., Wang, J., Ye, J., Ohno, P., Qin, Y., Stewart, M., McKinney, K., Di Carlo, P., and Martin, S. T.: Impact of NOx in SOA and organonitrates production, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12952, https://doi.org/10.5194/egusphere-egu22-12952, 2022.

Air pollution from fine particulate matter (PM_2.5) is a major environmental health risk associated with morbidity and excess mortality. In Europe, despite the multiple efforts for minimizing air pollution levels, it exceeds the recommended WHO guideline limits in many regions. Since observational data of air pollutant concentrations are spatially incomplete, regional air quality modeling is used to simulate ambient pollutants levels. However, air quality models are not always accurate and many sources of uncertainties are being involved. For example, input data e.g. from emission inventories can play a crucial role in the simulated concentration of air pollutants. Also, several studies have shown that organic aerosols are very prone to model biases and are usually underestimated by the models. This is because organic aerosols are mostly composed of secondary organic aerosols that are formed through chemical reactions in the air, from pathways which are not fully known and are not all included in models. Here, we use the Weather Research and Forecasting model, coupled with chemistry (WRF-CHEM) for simulating the annual mean concentration of PM_2.5 and the organic components over Europe. The EDGARv.5 global emission inventory is used as the basic input data for the anthropogenic emissions, and is also combined with the newly updated CAMS-REG-v4-Ref2 emission inventory for the VOCs emissions that originate from residential wood combustion. The latter is used as a complementary source of data for VOCs which are precursors of secondary organic aerosols and are often not well documented in emission inventories. However, CAMS-REG-v4-Ref2 was constructed from updated and harmonized emission factors for residential combustion, thus giving a better representation of these emissions over Europe. This work investigates the role of emission inventories in the simulation of PM_2.5 and organic aerosols and aims to quantify their impact on health assessments. We particularly focus on organic aerosols since these are considered more toxic and hazardous to human health than other inorganic fine particles.

How to cite: Paisi, N., Kushta, J., Van Der Gon, H. D., Violaris, A., and Lelieveld, J.: The role of emission inventories and chemical mechanisms on simulating PM2.5 and organic aerosols with WRF-CHEM, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13518, https://doi.org/10.5194/egusphere-egu22-13518, 2022.

The measurement of air pollutants is essential for decision-making in order to improve air quality and reduce human health risks. Low-cost sensor (LCS) technologies offer a unique opportunity to expand measurements of key air pollutants, but end users need to consider the capability of a measurement device in relation to the questions being asked of the data. End-users must a priori identify the data requirements and design quantifiable and transparent criteria by which to assess the measurement data. Having a reliable estimate of the measurement uncertainty is thus key to assessing and openly communicating the fitness for purpose of a particular measurement technique for a particular task. Despite their limitations (expensive and time-consuming), and as long as the uncertainties of the reference instrument are stationary and well-characterized, the best way up to now to characterize the LCS error structure is through colocation studies. Despite the complexity of colocation studies, global performance metrics (R2, RMSE, MAE, etc.) are often deemed convenient when assessing the performance and suitability of LCS. However, these simple metrics are limited and sometimes misleading, restricting our understanding of the error structure and therefore the information content of the measurements. In this work we used a selection of instruments -LCSs and reference- to investigate the nature of common air pollution measurement errors and the effect over traditional metrics and other -potentially more insightful- empirical approaches to transparently assess measurement uncertainty, discussing the implications of this on the end-use of LCS.

How to cite: Diez, S., Edwards, P., and Lacy, S.: What is the impact of errors on LCS data information content?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9676, https://doi.org/10.5194/egusphere-egu22-9676, 2022.