AS3.1
Orals: Mon, 24 Apr | Room F2
Understanding the health co-benefits of climate change mitigation and how they manifest across different socioeconomic groups is crucial to justify and prioritise future decarbonisation pathways to achieve net zero. In this work, we quantify future worldwide air quality and public health co-benefits of decarbonisation to limit end-of-century warming to either 2ºC (scenario SSP1-2.6) or 1.5ºC (scenario SSP1-1.9), relative to the middle-of-the-road pathway with a medium long-term radiative forcing target of 4.5 W m-2 (scenario SSP2-4.5). We use simulated ambient fine particulate matter (PM2.5) concentrations for the period 2015-2100 from the Coupled Model Intercomparison Project (CMIP6) experiments. We estimate the mortality burden attributable to exposure to ambient PM2.5 using population attributable fractions of relative risk, incorporating projected changes in population demographics and per-capita GDP. We find that following a future decarbonisation pathway could produce substantial global reductions in population exposure to PM2.5 pollution and associated premature mortality across all socioeconomic groups, with maximum health benefits achieved for middle-income populations (predominantly in Asia) around mid-century. Overall, the more moderate 2ºC-compliant mitigation scenario (SSP1-2.6) could reduce the global PM2.5-attributable mortality burden by 24% in 2050 relative to SSP2-4.5, averting ~2.5M (95% uncertainty interval (UI): 2.1-2.8M) annual deaths worldwide. The more stringent 1.5ºC scenario (SSP1-1.9) could reduce the PM2.5 mortality burden by 29% in 2050, averting ~2.9M (UI: 2.5-3.4M) annual deaths. The magnitude of the air quality and health benefits of reduced PM2.5 pollution through decarbonisation vary with the socioeconomic status of the exposed population, with greater reductions in the PM2.5 mortality burden in middle- and high-income regions (22%) than in the low-income region (15%). Overall, the disparity in PM2.5 exposure between low- and high-income populations is predicted to reduce by 2100 under all three future scenarios. However, the global PM2.5 exposure disparity is projected to increase up to mid-century under the SSP2-4.5 scenario, thus, immediate reduction in the disparity in the near term, is only achieved under a decarbonisation scenario. Despite overall reductions in global PM2.5 exposure inequalities by the end of the century, the disparity in PM2.5 exposure remains around 30%, with the low- and lower-middle-income populations continuing to experience PM2.5 exposures that are over three times the WHO Air Quality Guideline.
How to cite: Reddington, C., Turnock, S., Conibear, L., Arnold, S., Berrang Ford, L., Weaver, C., Forster, P., and Lowe, J.: Air pollution health inequalities in a low-carbon future, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9624, https://doi.org/10.5194/egusphere-egu23-9624, 2023.
Ultrafine particles (UFP), i.e. particles with an aerodynamic diameter below 100 nm, have a significant impact on public health and the hydrological cycle. Recent studies showed that their ability to penetrate more deeply into the lungs and potentially into the blood stream may cause an increased incidence of cardiovascular and cerebrovascular diseases. Additionally, UFPs significantly contribute to cloud condensation nuclei concentrations. However, knowledge on global distributions of UFPs is scarce.
We present a global simulation of UFP concentrations using the ECHAM/MESSy Atmospheric Chemistry Model (EMAC), including tropospheric and middle-atmospheric processes, and the modal aerosol microphysics submodel GMXe. Due to the high sensitivity of UFP concentrations to the size distribution of emitted particles, we derived emission median diameter for primary emissions from various sectors and species based on existing literature. We show the importance of primary emissions and nucleation on UFP concentrations as well as their composition, seasonality and vertical distributions.
Model results were evaluated over Europe, the United States, India and China, using particle size distribution and particle number concentration measurements from available datasets and the literature. We obtain reasonable agreement between the model results and observations. However, the highest values of observed, street-level UFP concentrations are systematically underestimated, whereas in rural environments close to urban areas they are generally overestimated by the model. As the relatively coarse global model does not resolve concentration gradients in urban centres and local UFP hotspots, high-resolution data of anthropogenic emissions is used to account for such differences in each model grid box. This downscaling further improves the agreement with observations, decreasing the root mean squared logarithmic error and removing discrepancies associated with air quality and population density gradients within the model grid boxes.
How to cite: Kohl, M., Chowdhury, S., Sharma, D., Cheng, Y., Tripathi, S. N., Sebastian, M., Pandithurai, G., Wang, H., Lelieveld, J., and Pozzer, A.: Numerical simulation and evaluation of global ultrafine particle concentrations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12650, https://doi.org/10.5194/egusphere-egu23-12650, 2023.
Over the past few decades, adequate evidence has confirmed the adverse effects of short-term PM2.5 exposure on asthma exacerbation, whereas the effects of long-term exposure on asthma morbidity and mortality, especially in adults, are still under debate. Benefiting from the recent explosion of relevant epidemiological studies, we comprehensively explored the impact of long-term ambient PM2.5 exposure on both childhood and adult asthma in light of the emerging evidence by combining multiple state-of-the-art approaches.
First, we explored the association between long-term PM2.5 exposure and risk of asthma by conducting a systematic review and meta-analysis. Through the systematic review, we identified a total of 3187 unique literatures, and found 32 on childhood asthma and 17 on adult asthma meeting the full eligibility criteria. According to the random-effects meta-analyses covering 10,519,588 children and 9,876,107 adults, we find that every 2 µg/m3 increment in PM2.5 is associated with a 3.8% (95% CI: 1.6%–6.1%) and a 1.1% (95% CI: 0.1%–2.2%) increase in risk of childhood asthma and adult asthma, respectively.
We then explored the exposure-response effect of asthma at different exposure levels—i.e., estimated the exposure-response curves for asthma, by constructing exposure-response functions (ERFs) based on the data extracted from the systematic review. We find that risk of childhood asthma increases almost linearly with exposure concentrations, while the risk of adult asthma increases sub-linearly. We also find that the risk of childhood asthma is much higher than that of adult asthma at any given exposure level.
After confirming by the meta-analysis and exposure-response analysis that PM2.5 exposure is statistically significantly associated with increased risk of asthma, we estimated the global burden of asthma attributable to long-term PM2.5 exposure by applying the ERFs in an epidemiological model. We find that PM2.5 exposure is responsible for 11.2 (95% CI: 7.4–14.1) million new cases of asthma and 58.3 (95% CI: 37.3–74.7) million prevalent cases in 2015, and children present majority of these cases.
Our study provides additional evidence on the effects of long-term PM2.5 exposure on asthma by concluding a statistically significantly positive association between PM2.5 exposure and the increased risk of asthma both in children and adults. Moreover, the substantial PM2.5-attributable burden of asthma assessed in this study suggests a large impact of PM2.5 on public health through asthma—i.e., the overall disease burden caused by PM2.5 is much higher than previously thought. In light of these findings, we call for more attention to the effects of PM2.5 exposure on asthma and for more stringent legislation to be designated sooner to improve air quality. In addition, the exposure-response curves established in our study—which incorporating evidence on high exposure levels that covering most of the worldwide exposure ranges—could be applied to assess the city to global scale asthma-related health benefits obtained from air pollutant reduction associated with policy scenarios.
How to cite: Ni, R., Su, H., and Cheng, Y.: Effects of long-term ambient fine particulate matter exposure on asthma: Evidence both for children and adults, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16213, https://doi.org/10.5194/egusphere-egu23-16213, 2023.
More than 50% of the population in the Indian subcontinent still depends on solid fuel for cooking purposes, and around 0.5 million yearly deaths are attributed to household air pollution. Despite the poor indoor air quality, especially in the rural spheres of the country, there is a lack of comprehensive field-based understanding of exposure to toxic chemical components such as polycyclic aromatic hydrocarbons (PAHs) associated with particulate matter (PM). This study attempts to quantify and assess the exposure to and inhalation health risk from 16 US EPA priority PAHs in size-segregated PM collected from relatively unexplored rural kitchens of northeastern India. A total of 44 sets of samples (5 from kitchens using liquefied petroleum gas (LPG), 18 using firewood (FW), 18 using a mixture of biomass (MB), and 3 non-cooking blanks) were collected and characterized from 6 locations. The sum of PM10-associated 16 priority PAHs (∑16 PAHs) was observed to be 258, 745, and 2554 ng m-3 for LPG, MB, and FW using kitchens, respectively. Size fraction-wise, the highest concentration of ∑16 PAHs was observed in PM0.25 and the least in PM1-10 across kitchen categories, with PM1 associated ∑16 PAHs comprising 80-92% of the total. ∑16 PAHs in kitchen settings were enriched by factors of 1.7-16.5 in comparison to the non-cooking background. Fuel-wise, stark differences were observed between kitchen categories. Within biomass using kitchens, the type of biomass and combustion (flaming vs smoldering) influenced the PAHs concentration and composition, e.g., ∑16 PAHs were enriched by factors of 3.4 for smoldering combustion of FW compared to flaming combustion of MB. Composition-wise, 2-3 ring PAHs dominated the total PAHs concentration in LPG kitchens (82%), while it constituted 43 and 25% in MB and FW using kitchens, respectively. In contrast, 5-6 ring PAHs showed dominance in FW using kitchens (52%), followed by MB (40%). This suggested a greater release of high molecular weight PAHs during biomass combustion with an increased contribution during the smoldering phase. Estimation of the total BaP equivalent concentration (BaPeq) revealed a similar profile as ∑16 PAHs with the lowest values in LPG using kitchens (29 ng m-3) followed by MB (235 ng m-3), and the highest in FW (856 ng m-3). Incremental lifetime cancer risk (ILCR) estimation via the inhalation pathway showed values above the acceptable risk for LPG (3.2×10-5), and much above tolerance levels for biomass using kitchens (MB: 2.6×10-4; FW: 9.4×10-4). Overall, these findings warrant immediate intervention into the cooking practices prevalent in northeastern India, with an emphasis on biomass-dependent households, in order to alleviate health risks.
How to cite: Sharma, B. and Sarkar, S.: Human exposure to size-segregated particulate polycyclic aromatic hydrocarbons during residential cooking in northeastern India, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-616, https://doi.org/10.5194/egusphere-egu23-616, 2023.
Corona Virus Disease 2019 (COVID-19) caused global reductions in transportation and industrial activities, which provided an unprecedented opportunity to examine the effects of reductions in anthropogenic activities on aerosol characteristics on a global scale. The observational study of the impact on columnar aerosol characteristics and radiative effects during the COVID-19 pandemic outbreak period, when anthropogenic emissions are significantly suppressed globally, can be helpful in quantifying the anthropogenic influence on aerosol properties for the accurate assessment of radiative and climatic impacts of aerosols. This study utilizes the high-quality aerosol datasets from Aerosol Robotic Network (AERONET) over 224 sites covering the entire globe, and satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) to analyze the difference in columnar aerosol properties between the year 2020 (COVID) and 2017-2019 (normal) on a seasonal scale over 10 different regions of the world. The most significant reduction in AOD by AERONET and MODIS observations is observed over most of the regions during the summer season, followed by the spring season of 2020 compared to the respective seasons of 2017-2019, when many countries imposed lockdowns. During summer, the highest reduction in AOD is observed over South Asia by MODIS (−0.09, 20% reduction) and AERONET (−0.07, 15% reduction), where aerosol loading is relatively higher during normal scenario. Over East North America and Europe, AERONET AOD reduced by −0.02 and −0.04, respectively. A significant reduction in Angstrom exponent (AE) and fine mode fraction (FMF) in most regions confirms the reduction in fine mode anthropogenic aerosols. However, a significant increase in AE and FMF (~20%) in South Asia is observed due to significant reduction in dust AOD (natural), which decreased the amount of coarse mode aerosols during the COVID period. Furthermore, the difference in aerosol radiative forcing at the surface (ARFSFC) by Clouds and Earth’s Radiant Energy Budget Scanner (CERES) data shows a significant reduction in ARFSFC in most regions during COVID period, whereas the highest reduction in ARFSFC of ~20% is observed over South Asia consistent with the reduction in aerosol emissions. This observational study over a global scale during the unprecedented COVID-19 period can be helpful for undertaking future mitigation strategies related to anthropogenic aerosol emissions and their precursors to reduce their impact on the climate.
How to cite: Ansari, K. and Srikanthan, R.: Global impact on aerosol characteristics during COVID-19 using ground- and satellite-based observations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13964, https://doi.org/10.5194/egusphere-egu23-13964, 2023.
To elucidate the molecular chemical compositions, volatility-polarity distributions, as well as influencing factors of Chinese cooking emissions, a comprehensive cooking emission experiment was conducted. Volatile organic compounds (VOCs), intermediate volatility, and semi-volatile organic compounds (I/SVOCs) from cooking fumes were analyzed by a thermal desorption comprehensive two-dimensional gas chromatography coupled with quadrupole mass spectrometer (TD-GC×GC-qMS). Emissions from four typical Chinese dishes, i.e., fried chicken, Kung Pao chicken, pan-fried tofu, and stir-fried cabbage were investigated to illustrate the impact of cooking style and material. Fumes of chicken fried with corn, peanut, soybean, and sunflower oils were investigated to demonstrate the influence of cooking oil. A total of 201 chemicals were quantified. Kung Pao chicken emitted more pollutants than other dishes due to its rather intense cooking method. Aromatics and oxygenated compounds were extensively detected among meat-related cooking fumes, while a vegetable-related profile was observed in the emissions of stir-fried cabbage. Ozone formation potential (OFP) was dominated by chemicals in the VOC range. 10.2% - 32.0% of the SOA estimation could be explained by S/IVOCs. Pixel-based partial least squares-discriminant analysis (PLS-DA) and multiway principal component analysis (MPCA) were utilized for sample classification and component identification. The results indicated that the oil factor explained more variance of chemical compositions than the cooking style factor. MPCA results emphasize the importance of the unsaturated fatty acid-alkadienal-volatile products mechanism (oil autooxidation) accelerated by the cooking and heating procedure.
How to cite: Guo, S., Song, K., Gong, Y., Lv, D., Zhang, Y., Wan, Z., li, T., Zhu, W., Wang, H., Yu, Y., Tan, R., Shen, R., Lu, S., Chen, Y., and Hu, M.: Semi-and intermediate- volatility organic compounds from Chinese domestic cooking emissions and their contribution to secondary organic aerosols, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1939, https://doi.org/10.5194/egusphere-egu23-1939, 2023.
A major fraction of organic aerosol (OA) is water-soluble. The water-soluble organic aerosol (WSOA) significantly impacts aerosol hygroscopicity and cloud condensation nuclei (CCN) formation, and adversely affects human health. In this study, characterization of WSOA in PM2.5 was done for the samples collected at two sites (Hauz Khas and Pusa) in Delhi NCR, one of the most polluted cities in the world, during the agricultural crop-residue burning period (October-November, 2019) and winter (December, 2019) using offline aerosol mass spectrometry (AMS) technique and compared with co-located real-time AMS measurements. Offline AMS provides quantitative separation of OA factors that can be primary or secondary. Offline AMS analysis showed that approximately 68% and 64% of OA are water-soluble in Hauz Khas and Pusa, respectively, which was corroborated by the filter-based measurements of water-soluble organic carbon (WSOC) and organic carbon (OC) using a TOC-L analyzer and OCEC analyzer, respectively. Three primary factors, including traffic, biomass burning, and solid fuel combustion, and two secondary factors (or sources) were resolved with Positive Matrix Factorization (PMF) analysis on the WSOA data from offline AMS. The results showed that secondary factors dominated the WSOA (~41%), followed by biomass-burning organic aerosol (BBOA) (30-34%). In addition, the recoveries of the organic factors from several sources, including traffic, biomass burning, solid fuel combustion, and secondary organic aerosol are discussed. More oxidized organic aerosol (MO-OOA) is highly water soluble (88-92%), representing highly oxidized compounds generated from aqueous-phase reactions. The relatively small contribution of hydrocarbon-like organic aerosol (HOA) to WSOA was most likely due to their low water solubility. Overall, this study improves the understanding of the OA sources and their water solubility over the study region.
How to cite: Bhowmik, H., Rastogi, N., Prévôt, A., and Tripathi, S. N.: Organic aerosol sources and their water-solubility in Delhi NCR: Insights from offline Aerosol mass spectrometric technique., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-916, https://doi.org/10.5194/egusphere-egu23-916, 2023.
Non-methane volatile organic compounds (NMVOCs) are emitted from various anthropogenic and biogenic sources. They act as precursors for the formation of tropospheric ozone and secondary organic aerosols (SOA) in the presence of sunlight and oxidizing radicals (OH, Cl, NO3). The measurements of NMVOCs are essential to understand the formation of new gas-to-particle aerosols, leading to high air pollution episodes. The Indo-Gangetic Basin (IGB) of India, one of the world’s most polluted areas, has been experiencing high aerosols and NMVOCs loadings throughout the year. Delhi and Lucknow are the two main cities in the IGB region selected for the study. The main aim of this study is to compare the contributions of different source factors to NMVOCs concentrations and their role in SOA formation. A proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) was deployed to perform real-time chemical characterisation of NMVOCs during two different campaigns in Delhi (2019) and Lucknow (2020-2021), respectively. The High-resolution Time of Flight Mass Spectrometer (HR-ToF-MS), Aethalometer and other instruments were also deployed at both sites. A receptor modelling approach, positive matrix factorisation (PMF), was used with a robust multilinear engine (ME-2) for source apportionment analysis. The present study is a novel attempt to perform PMF over mass spectra of ~90 and ~170 NMVOCs in Delhi and Lucknow, respectively, for different seasons. Their associations with secondary organic aerosol formation using SOA yields were also analyzed. For Delhi, 8-factor solution was selected and resolved into two traffic-related factors: solid-fuel combustions (SFC), secondary VOCs (SVOCs), biogenic factor and solvent-use factor based on statistical parameters. Similarly, for Lucknow, a 6-factor solution was selected with traffic, 2 SVOC factors, 2 SFC factors and one volatile chemical products-related factor. The traffic factor has the presence of aromatics, non-aromatics and oxygenates, while the biogenic factor is marked by isoprene and its fragment (methyl vinyl ketone). The first, second, and third-order oxygenates show peaks in the SVOCs factor, while phenols, furans, and n-containing compounds are found in the SFC factor. It is observed that vehicular emissions (30%) contributed highest to NMVOCs concentrations in Delhi, while the SFC (28%) was a prominent factor in Lucknow. Interestingly, SFC factors contribute the highest to SOA formation at both cities. It is inferred that the agricultural residue burning episodes in neighbouring states, trash burning and solid fuel burning for cooking within and around the cities contributed to the emissions of NMVOCs and the formation of SOA during winter and post-monsoon periods.
How to cite: Jain, V., Tripathi, S. N., Tripathi, N., Gupta, M., Sahu, L. K., Murari, V., Gaddamidi, S., Shukla, A. K., and Prevot, A. S. H.: Comparison of real-time NMVOCs measurements using PTR-TOF-MS in two cities of IGB region, India: Sources identification and influence on SOA formation, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-585, https://doi.org/10.5194/egusphere-egu23-585, 2023.
The aerosol-based transport of viruses and bacteria through the transmission of aerosolized expiratory secretions is one of the main routes for the spreading of infectious diseases such as SARS-CoV-2. A number of studies have confirmed that environmental factors such as temperature and relative humidity can affect the inactivation and transmission of respiratory pathogens. However, there remain significant uncertainties in understanding aerosol micro-physics occurring under different environmental conditions to quantify the survival of microorganisms carried by aerosols. Here we study the size and phase changes of levitated saliva droplets composed of various salts and mucin under well-defined atmospheric conditions. An electrodynamic balance (EDB) is utilized for recording the evaporation and condensation kinetics of single, levitated saliva droplets with a time resolution of seconds. Efflorescence and deliquescence behaviors of droplets are monitored using light scattering and Mie theory. Compared with pure water droplets, a saliva droplet remains stably levitated for hours when the droplet approaches crystallization having reached a final size during evaporation. The morphology of crystallized particles will be imaged using a scanning electron microscope (SEM). The organic-based phase is expected to shield pathogens from inactivation by forming a solid or semisolid shell hindering the diffusion of solutes. This work highlights the importance of accounting for changes in the micro-environment of aerosols undergoing evaporation and condensation in a realistic environment which is needed to study the viability of airborne viruses and other microorganisms.
How to cite: Meng, Y., Dresch, T., Duft, D., Kiselev, A., and Leisner, T.: The efflorescence-deliquescence behavior of saliva droplets and its implication for viability of airborne microorganisms, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7737, https://doi.org/10.5194/egusphere-egu23-7737, 2023.
Light-absorbing organic aerosols, often referred to as brown carbon (BrC), significantly contribute to atmospheric brown clouds and are a major climate forcing agent over South Asia. In addition to direct emissions in the form of fine mode aerosol, BrC forms secondarily in the atmosphere via homogeneous and heterogeneous chemical reactions involving anthropogenic and biogenic precursor gases, thereby enhancing the complexity of its molecular composition. Detailed molecular characterization and identification of potential BrC chromophores are essential to facilitate a proper understanding of BrC source profiles, atmospheric transformation processes and resultant climate effects. However, owing to its relatively short atmospheric lifetime and large spatial variability, molecular-level characterization of BrC aerosol is challenging. Here we report the first insights into molecular profile of aqueous BrC in the Indian subcontinent, specifically, the eastern Indo-Gangetic Plains (IGP) with a distinct heterogeneity of BrC sources, on a diurnal and seasonal basis. To this end, daytime and nighttime PM2.5 samples collected during 2019-2020 at a rural receptor location in the eastern IGP were extracted for the aqueous BrC fraction and subsequently analyzed using high-performance liquid chromatography coupled with a diode array detector and a time-of-flight mass spectrometer (HPLC-DAD-ToF-ESI-MS).
In total, around 3000 chemical formulas of organic compounds were determined in the positive and negative modes, which were classified into four major groups: CHO, CHON, CHONS and CHOS. In the negative mode, CHO- (36-48%) was the most abundant group, followed by CHON- (23-31%) and S-containing groups (CHONS- (7-19%) and CHOS- (11-32%)) whereas CHON+ (47-58%) showed the highest abundance in the positive mode followed by CHO+ (21-29%) and S-containing groups (CHONS+ (11-18%) and CHOS+ (3-11%)). The reaction between ammonia and carbonyls could lead to the formation of abundant CHON+ compounds with reduced N-containing groups (averaged O/C: 0.2, H/C: 1.7), while CHON- consisted of oxidized N-containing groups (averaged O/C: 0.5, H/C: 1.1). Daytime samples were enriched with CHO- and CHOS- compounds as compared to nighttime samples throughout the seasons, potentially suggesting photochemical formation of these multifunctional compounds. On the contrary, N-containing compounds such as CHON- and CHONS- showed higher abundance during nighttime, suggesting the importance of dark-phase NO3- chemistry. The higher double-bond equivalent (DBE) value of the CHON- group in post-monsoon and winter (7-8) indicated the presence of unsaturated compounds possibly emitted from agricultural residue burning or via secondary formation through NOx reactions. In contrast, the higher DBE value of the CHOS- group during summer (~6) suggested the emission of S-containing compounds from diesel vehicles, coal combustion or secondary formation via photochemical reaction pathways. The enrichment of water-soluble nitroaromatic chromophores (C6H5NO3, C7H7NO4, C9H7NO4, etc.) during post-monsoon and winter was consistent with the dominant presence of a biomass burning source, echoing our previous findings based on multiple independent lines of evidence. Overall, these results provide the first insights into the linkage between BrC chemical and optical properties in the Indian context.
How to cite: Dey, S. and Sarkar, S.: Molecular characteristics of aqueous brown carbon in the eastern Indo-Gangetic Plains: Insights from a high resolution mass spectrometry approach, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2275, https://doi.org/10.5194/egusphere-egu23-2275, 2023.
The synoptic meteorological field plays an important role in the daily-scale PM2.5 variability in East Asia. Since East Asia is located on the eastern boundary of the Eurasian continent, the expansion and contraction of the Siberian high-pressure system act as an essential mechanism for determining surface PM2.5 concentrations in the winter season. Here, we select four climate indices representing the variability of the Siberian high-pressure system and analyze the correlation with the daily variability of the observed winter PM2.5 concentrations in China and South Korea over the past six years. Siberian High Intensity and East Asian Winter Monsoon indices showed a more pronounced correlation with the daily surface PM2.5 concentration changes, and the daily surface PM2.5 concentrations in North China Plain showed a maximum change of ±40 μg m-3 after exceeding the threshold (+1 or −1). The climate indices associated with the Siberian high-pressure system can effectively predict daily PM2.5 concentrations in East Asia within a week.
How to cite: Jeong, J. and Park, R.: Prediction of PM2.5 concentrations during winter in East Asia using climate indices, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3150, https://doi.org/10.5194/egusphere-egu23-3150, 2023.
Homogeneous nucleation is an important source of new particles in the atmosphere worldwide. The resulting newly formed stable nuclei can grow to larger sizes and affect air quality and climate. Unexpected significant spatial variability of the nucleation frequency has been observed in Greece in the only previous relative study: very high frequency in Thessaloniki, intermediate in Eastern Crete and low in Patras (Patoulias et al., 2018). Our hypothesis is that Greece may be an excellent natural laboratory to investigate the factors affecting nucleation and to understand the reasons behind this surprising variability.
Extensive continuous aerosol size distribution measurements took place during two summers (2020 and 2021) as part of the PANACEA project in 11 different locations: Patras, Xanthi, Ioannina, Finokalia, Athens, Thessaloniki, Sifnos, Chania, Costa Navarino (NEO), Lesvos and Mt. Helmos. The instrumentation used included a number of scanning mobility particle sizers (SMPS) for the measurement of the particles and a suite of gas monitors for measuring SO2, NOx, NH3 and CO in selected sites. A particle size magnifier (PSM) was deployed in the Patras site during the 2021 campaign, providing valuable information regarding nanoparticles with diameter down to 1 nm.
The observations suggest that indeed the nucleation frequency during summer in Greece varies from close to zero in the southwestern parts of the country to more than 70% in the northern central and eastern regions. The analysis of the measurements in the various sites shows that the proximity to coal-fired power plants is a major factor affecting the nucleation frequency. North-eastern and northern airmasses passing over such locations in the Balkans and Western Turkey where strongly associated with nucleation. Also, the emissions of ammonia during summer, suggest that it exhibits similar spatial gradients with the observed nucleation frequency and may be controlling nucleation in Greece. The corresponding measurements in each site, were also used to estimate the corresponding particle growth and formation rates and the condensation and coagulation sinks.
The detailed analysis of the measurements in Patras, Western Greece, suggests that nucleation was infrequent in this location (12%), but particles that were formed a few hours earlier over central Greece are often transported to this area after they have grown to sizes of 20-30 nm. The air mass history suggested that new particle formation often took place in the vicinity of an area 100-150 km northeast of Patras, with significant agricultural activity and therefore, high emissions of ammonia and amines. The relatively high emissions of biogenic volatile organic compounds in Western Greece where Patras is located, did not appear to assist in the local formation of new particles.
How to cite: Aktypis, A., Kaltsonoudis, C., Matrali, A., Vasilakopoulou, C. N., Mihalopoulos, N., Kalkavouras, P., Bougiatioti, A., Kalivitis, N., Eleftheriadis, K., Vratolis, S., Gini, M. I., Kouras, A., Lazaridis, M., Chatoutsidou, S. E., Nenes, A., and Pandis, S. N.: Significant spatial gradients in new particle formation frequency in Greece during summer, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3943, https://doi.org/10.5194/egusphere-egu23-3943, 2023.
Water-soluble dicarboxylic acids (hereafter diacids) and sugars are an important part of the atmospheric water-soluble organic aerosol. Here, we studied diacids and other compounds in fine aerosol particles (PM1) collected at a rural background site National Atmospheric Observatory Košetice (NAOK), Czech Republic, Central Europe. Aerosol samples were collected every second day for 24 h from September 2013 to August 2014 (n=146). Based on receptor modeling (PMF), we identified PM1 organic compounds that are more typical to anthropogenic and to biogenic sources. We have apportioned two anthropogenic sources especially evident during the heating season from mid-October to mid-April: (i) biomass burning (BB) (main contribution of levoglucosan and methylsuccinic, maleic, methylmaleic and azelaic acids) and (ii) fossil fuel combustion (FF) (represented by phthalic, terephthalic and ketomalonic acids). Furthermore, we identified two sources of biogenic aerosols: (iii) summer factor was largely characterized by compounds with three and seven carbons (malonic, 4-ketopimelic, oxoheptanoic, methylmalonic acids) while (iv) spring biogenic factor was characterized mostly by primary sugars, normal chain diacids and their precursors (oxalic, malonic, succinic, glutaric, ketomalonic, 4-oxobutanoic and 5-oxopentanoic acids). Last but not least, we distinguished (v) background factor mainly represented by less oxidized diacids precursors such as glyoxal, methylglyoxal, glyoxylic and pyruvic acids, but also by aromatic diacids, which may originate from traffic emissions; a stable and year-round source.
Acknowledgement: This conference contribution was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project ACTRIS-CZ-LM2018122, by the Czech Science Foundation grant No. 20–08304J 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., Deshmukh, D.K., Pokorná, P., Schwarz, J., Ždímal, V.: Anthropogenic and biogenic tracers of fine aerosol based on seasonal distributions of dicarboxylic acids, sugars and related compounds at a rural background site in Central Europe, Atmos. Environ., submitted, 2023.
How to cite: Vodička, P., Kawamura, K., Deshmukh, D. K., Pokorná, P., Schwarz, J., and Ždímal, V.: Source apportionment of fine aerosol at a rural background site in Central Europe based on seasonal distributions of dicarboxylic acids, sugars and related compounds, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6145, https://doi.org/10.5194/egusphere-egu23-6145, 2023.
The dynamics of atmospheric aerosols is governed by the spatio-temporal variability in the particle number size distributions. Atmospheric new particle formation begins with the formation of the cluster mode (sub-3nm) particle number concentrations followed by their growth to large sizes in the atmosphere. Here, we used three years (2019-2022) particle number size distribution measurements in the size range from 1 to 3 nm from nano Condensation Nucleus Counter (nCNC) in Hyderabad, India. The distinct seasonal variation was observed in size-segregated cluster mode particle number concentrations, with the highest concentrations in spring (March-May) and the lowest concentrations in winter (December-February). The seasonal variability is strongly linked to the factors affecting cluster mode formation such as planetary boundary layer evolution, temperature (oxidation extent), pre-existing particles (coagulation sink), etc. The calculated sulfuric acid proxy is strongly correlated with cluster mode particle number concentrations and formation rates, indicating the important role of sulfuric acid in aerosol nucleation. The formation rate and growth rate of cluster mode particles were also the highest during spring than winter. Our analysis further revealed that cluster mode number concentrations were the highest at low particulate matter less than 2.5 µm (PM2.5) while it was the lowest at high PM2.5 levels, indicative of the efficient scavenging of cluster mode particles by large-size pre-existing particles. We have also used PARticle Growth And Nucleation (PARGAN) inversion model to estimate the formation rate and growth rate from particle size distribution measurements in the size range from 10 nm to 560 nm. We found that the estimated formation and growth rates from PARGAN model were compared with the measured formation and growth rates from nCNC, within the uncertainty levels. This underlines the applicability of PARGAN inversion model for estimating cluster mode formation and growth rates where such measurements are not available, particularly in India.
How to cite: Sebastian, M. and Kanawade, V. P.: Characteristics of cluster mode particle number concentrations in India, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-563, https://doi.org/10.5194/egusphere-egu23-563, 2023.
The stable carbon isotope 13C has the potential to give insights into sources and processing of organic aerosol. We use a method to measure d13C in OC desorbed from filter samples at three different temperature steps: 200 °C, 350°C and 650°C. The results give a rough indication of aerosol volatility, as more volatile compounds usually desorb at lower temperatures.
We demonstrate with an extensive source study that in Lithuania and likely other Eastern European regions, the main anthropogenic primary sources for organic carbon (OC) have distinct isotopic signatures. d13C values of vehicular emissions show the most negative values around - 29 ‰, emissions from combustion of the most common wood types are more enriched with values around -26 to -27 ‰, and coal burning is around -25‰. For source samples, d13C values at the three desorption temperature steps usually do not differ more than 1 ‰.
In the ambient samples, OC had more negative δ13C values in summer than in winter, which can be explained by the contribution of biomass/coal burning sources in winter. At the urban site δ13C of OC did not change much with increasing desorption temperature in winter, which is typical for primary sources. In the summer δ13C of OC was clearly more negative for lower desorption temperatures at all three sites. This is likely due to the influence of secondary organic aerosol formation in summer, which should have depleted (more negative) isotopic signature and contributes strongly to the more volatile fraction.A higher fraction of more refractory OC in summer compared to winter-time suggests active photochemical processing of the primary organic aerosol as an important process at all three sites.
This is consistent with our laboratory studies, where we age source samples in a small reactor under UV light. Photolysis causes mainly mass loss in OC that desorbs at 200 °C. At the same time, 13C becomes more enriched in OC desorbed at the higher temperature steps, leading to a bigger difference in d13C between OC200 and OC350, as observed in the ambient atmosphere.
In summary, analyzing stable isotopes of OC at different desorption temperature steps gives a powerful tool for diagnosing aging processes.
How to cite: Dusek, U., Masalaite, A., Yao, P., van Ettinger, N., Remeikis, V., and Paul, D.: Seasonal changes of sources, volatility, and aging of organic aerosols in eastern Europe reflected in the stable isotopic composition, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16841, https://doi.org/10.5194/egusphere-egu23-16841, 2023.
The chemical composition and physical properties of aerosols significantly affect human health, cloud physics, and local climate. Hygroscopicity, a crucial physical property, represents the ability of aerosol to absorb moisture from the surrounding atmosphere and act as cloud condensation nuclei. In this study, we applied two home-built Air Quality Box (AQB) systems co-locating with Taiwan EPA Nanzi station (22°44’12” N, 120°19’42” E) in Kaohsiung, Taiwan, from 4 to 19 February 2021. AQB is composed of low-cost sensors to monitor the ambient gaseous pollutants (CO, CO2, NO, NO2, O3, SO2, and Non-Methane Hydrocarbons), aerosol particles (number size distribution between the diameter of 0.38-17 μm), and the meteorological parameters (T, RH, and P). As to PM (Particulate matter), EPA station monitors PM concentration at the dry state by controlling the measurement at less than 50% while the optical particle counter (OPC) in AQB reflects the ambient PM directly. The difference between the two values represents the amount of absorbed liquid water in the ambient condition. With the consideration of OPC sensitivity and aerosol hygroscopicity, OPC sensitivity and k-Köhler equation are applied to derive the hygroscopicity parameter (k) for PM2.5 (fine particles) and PM2.5-10 (coarse particles with a diameter in the range of 2.5 to 10 µm). In our preliminary results, OPC sensitivity is different between fine and coarse particles at RH<50%, suggesting the requirement of sensitivity adjustment for simple OPC at different particle ranges. The derived k ranges from 0.15 to 0.29, and 0.05 to 0.13 for fine and coarse particles, respectively. The results are consistent with those derived from collected samples analyzed using ion chromatography in our previous Kaohsiung winter campaign. The developed method provides a comprehensive way to determine the hygroscopicity of ambient aerosols, which can be helpful for atmospheric models to compare the results for further efficiency evaluation of aerosol acting as cloud condensation nuclei and radiation calculation. Furthermore, the application of this method for the low-cost sensors applied widely nearby EPA stations is under analysis to evaluate the performance of low-cost OPC sensors and to retrieve the enhanced temporal and spatial aerosol hygroscopicity.
How to cite: Huang, W.-C., Hwang, W.-C., and Hung, H.-M.: Deriving the hygroscopicity of ambient particles using low-cost optical particle counters, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2213, https://doi.org/10.5194/egusphere-egu23-2213, 2023.
The physical and chemical characteristics of atmospheric aerosol particles are complex in urban areas. It is of great significance to clarify the influence of different emission sources on atmospheric chemical components for tracing and fine control of air pollution. In this study, passive aerosol samplers were used to collect samples in urban area and steel industrial area in Rizhao, a typical coastal city in eastern China, the collected samples were analyzed by intelligent scanning electron microscope environmental particle analysis system (IntelliSEM-EPAS), which is based on computer-controlled scanning electron microscopy technology. The results show that the atmospheric particulates in Rizhao city are mainly composed of irregular carbonaceous particles, sulfur-containing particles and mineral particles, the number contribution of C-rich particles in urban samples is 53.5%, which is 2.5 times higher than that in steel industrial area samples, the number contribution of particles greater than 1 μm was 9.0%, which is 1.7 times that of the samples in steel industrial area, urban dwellers' activities and industrial processes are the main sources of atmospheric particulate matter in urban area. In steel industrial area, the number contribution of sulfur-containing particles is 72.9%, the mass contribution of sulfur-containing particles is 30.9%, and the mass contribution of iron rich particles is 5.3%, which are 1.8 times, 3.6 times and 2.9 times higher than that of urban samples, respectively. These results indicated that primary pollutants emitted by iron and steel enterprises and secondary formation are the main sources of atmospheric particles in steel industrial area, which has a significant impact on the composition of regional atmospheric particulates.
How to cite: Yao, W. and Pan, X.: Study on physical and chemical characteristics and source of atmospheric Single particulate matter in Rizhao city based on EPAS technology, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5435, https://doi.org/10.5194/egusphere-egu23-5435, 2023.
This study focuses on the characterization of aerosol hygroscopicity using remote sensing techniques. A Mie-Raman-Fluorescence lidar, developed at the Laboratoire d’Optique Atmosphérique in Lille, France, in combination with a Microwave radiometer, allow to monitor continuously both aerosols and water vapor. Hygroscopic growth cases can be identified when an aerosol layer presents an increase in both aerosol backscattering coefficient and relative humidity. Looking at the class of the aerosol among the layer, determined from clustering methods, and the fluorescence backscattering coefficient, which is expected to be unaffected by the presence of water, it is possible to verify that the aerosol layer is homogeneous. Therefore, the change in the backscattering coefficient is then only due to water uptake. The Hänel theory describes the evolution of the backscattering coefficient with relative humidity and introduces a hygroscopic coefficient, γ which depends on the aerosol type and the relative humidity threshold of the dry condition. One case study has been identified on 10 March 2021 for a smoke aerosol layer. For this case, γ was determined at for . This value is consistent with other values found in the literature for smoke particles. Other cases have been analyzed and this set of example illustrates the potentiality of the methodology presented here.
How to cite: Miri, R., Goloub, P., Pujol, O., Hu, Q., Veselovskii, I., Podvin, T., and Ducos, F.: Aerosol hygroscopic growth study from synergy between Mie-Raman-Fluorescence Lidar and Microwave Radiometer, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2058, https://doi.org/10.5194/egusphere-egu23-2058, 2023.
Quantifying aerosol impacts on climate is an inherently multiscale problem since macro-scale impacts are determined by processes on the micro-scale. This poses unique modeling challenges, since these microscale processes lead to a continuously evolving aerosol mixing state, which is difficult to represent in large-scale models. This presentation will show how high-detail particle-resolved simulations can be used to predict the evolving aerosol mixing state on the regional scale. In contrast to traditional aerosol models that use bins or modes to represent the aerosol, the particle-resolved approach uses individual computational particles that evolve in size and composition as the particles undergo aging processes in the atmosphere. This approach is therefore not limited by assumptions about particle composition within a given size range and can represent the full aerosol mixing state without simplifying assumptions. I will show results that illustrate the spatio-temporal evolution of aerosol mixing state, going beyond the traditional definitions of “externally” or “internally” mixed populations. I will conclude with a framework to synthesize a picture of the ambient aerosol from models and observations. This focuses on suitable metrics to quantify mixing state and sampling strategies to determine these metrics that are accessible for both models and observations. Together, these provide a unique opportunity for “getting the right answer for the right reasons”.
How to cite: Riemer, N., Curtis, J., Gasparik, J., and West, M.: Aerosol mixing state evolution in the atmosphere: A synthesis of measurements and models, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10921, https://doi.org/10.5194/egusphere-egu23-10921, 2023.
Atmospheric aerosol particles play an important role for air quality and climate. Secondary organic aerosol (SOA) make up a significant mass fraction of these particles. SOA particles mostly forms from oxidation of gases, followed by gas-particle conversion of the oxidation products. Due to the variety of precursors and oxidation pathways involved in SOA formation, atmospheric SOA rank among the least understood aerosol types. To assess the impacts of SOA particles on air pollution and climate, knowledge of the number of phases in internal mixtures of different SOA types is critical. For example, gas-particle partitioning of organic species, and thus ultimately ambient SOA mass concentration, strongly depend on the number of phases in SOA particles. Atmospheric models traditionally assumed that different SOA types form a single condensed organic phase when internally mixed in individual particles. In case of mixed SOA particles with a single condensed phase uptake of semi-volatile vapors are enhanced, due to a lowering of the activities in the organic aerosol phase, and hence a lowering of the equilibrium partial pressure. By contrast, the equilibrium partial pressure is greater if the different SOA types form separate phases due to repulsive intermolecular forces between immiscible organic molecules. Consequently, enhancement of vapor uptake and ambient SOA mass concentrations will be smaller or absent in the case of phase-separated SOA particles.
Here, using fluorescence microscopy, we directly observed the number of phase in individual particles containing mixtures of different SOA types. A total of 6 different SOA types were generated in environmental chambers from oxidation of single precursors. This included both biogenic and anthropogenic SOA types, having elemental oxygen-to-carbon (O/C) ratios between 0.34 and 1.05, covering values characteristic for aged and fresh atmospheric SOA. The number of phases of all possible internal mixtures of two different SOA types, termed SOA+SOA particles, was investigated as a function of humidity between 90% and 0% relative humidity (RH). We found that the number of phases was independent of RH within the range investigated and that 6 out of 15 SOA+SOA mixtures resulted in particles with two condensed organic phases. The observation of phase separated SOA+SOA particles challenges the approach of assuming a single condensed organic phase when representing SOA formation in atmospheric models. Specifically, we demonstrate that the difference in the average O/C ratio between the two SOA types of a mixture (ΔO/C) is a good predictor of the number of phases in particles that are internal mixtures of different SOA types: two-phase SOA+SOA particles formed for ΔO/C ≥ 0.47, while one-phase SOA+SOA particles formed for ΔO/C < 0.47. This threshold ΔO/C provides a simple, yet powerful parameter to predict whether mixtures of fresh and aged SOA particles form one- or two-phase particles in models.
How to cite: Mahrt, F., Peng, L., Zaks, J., Ohno, P. E., Smith, N. R., Gregson, F. K. A., Qin, Y. M., Faiola, C. L., Nizkorodov, S. A., Ammann, M., Martin, S. T., and Bertram, A. K.: Not all types of secondary organic aerosol mix: two phases observed when mixing different secondary organic aerosol types, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1923, https://doi.org/10.5194/egusphere-egu23-1923, 2023.
Night-time reactions of biogenic volatile organic compounds (BVOCs) and nitrate radicals (NO3) can lead to the formation of secondary organic aerosol (BSOANO3). Here we firstly present the chemical composition and volatility of BSOANO3 formed in the dark from three precursors (isoprene, α-pinene, and β-caryophyllene) in atmospheric simulation chamber experiments (Wu et al., 2021; Bell et al., 2022; Graham et al., 2022). The chemical composition of particle-phase compounds was measured with a chemical ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). The volatility information of BSOANO3 was derived from isothermal evaporation chambers, temperature-dependent evaporation in a volatility tandem differential mobility analyzer (VTDMA), and thermal desorption in the FIGAERO-CIMS. In addition, the molecular composition of particulate compounds was used in volatility parametrizations to calculate the compounds’ saturation vapor pressures and to establish volatility basis sets (VBS, Donahue et al., 2011) for the bulk aerosol. Four different parametrizations were tested for reproducing the observed evaporation in a kinetic modeling framework (Riipinen et al., 2010). Here, we compare the different methods for particle volatility determination and discuss the limitation of the parameterizations.
Our results suggest the BSOANO3 from α-pinene and isoprene be dominated by low-volatility organic compounds (LVOC) and semi-volatile organic compounds (SVOC), while the corresponding BSOANO3 from β-caryophyllene consists primarily of extremely low-volatility organic compounds (ELVOC) and LVOC. The parameterizations yielded variable results in terms of reproducing the observed evaporation, and generally the comparisons pointed to a need for re-evaluating the treatment of the nitrate group in such parameterizations.
Furthermore, we link the lab experiments to field observations of secondary organic aerosols and organic nitrates from a boreal forest (ICOS Norunda, Sweden), which is dominated by monoterpene emissions and includes also isoprene and sesquiterpene emissions. We will show the chemical composition and volatility of the particles detected with a FIGAERO-CIMS, compare them to the lab results, and discuss how nitrate-initiated nighttime oxidation of different precursors contribute to the total particle formation and growth.
References:
Wu, C. et al., Atmos. Chem. Phys., 21, 14907–14925, 2021
Bell, D. et al., Atmos. Chem. Phys., 22, 13167–13182, 2022
Graham, E. and Wu, C. et al, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2022-1043, 2022
Donahue, N. M. et al., Atmos. Chem. Phys., 11, 3303–3318, 2011
Riipinen, I. et al., Atmos. Environ., 44-5, 597-607, 2010
How to cite: Wu, C., Graham, E. L., Bell, D. M., Bertrand, A., Baltensperger, U., El Haddad, I., Fujimura, C., Gramlich, Y., Haslett, S. L., Krejci, R., Tsiligiannis, E., Hallquist, M., Riipinen, I., and Mohr, C.: Molecular composition and volatility of secondary organic compounds from nitrate radical oxidation of biogenic volatile organic compounds – from lab to field , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13967, https://doi.org/10.5194/egusphere-egu23-13967, 2023.
Volatile (VOCs) and intermediate volatility organic compounds (IVOCs) can undergo atmospheric oxidation, forming secondary organic aerosol (SOA) as their low volatility oxidation products condense in the particulate phase. Recent research has suggested that IVOCs, which have been neglected for decades, may have an important role in atmospheric SOA formation (Tkacik et al., 2012). Most of the work until now, has focused on SOA formation from VOCs with 5 to 10 carbon atoms.
The main goal of this work is to study the SOA production from the reactions of individual anthropogenic large VOCs and IVOCs with hydroxyl radicals (OH), under high NOx conditions often encountered in urban areas. The organic compounds that were studied include cyclic alkanes of increasing size (amylcyclohexane, hexylcyclohexane, nonylcyclohexane and decylcyclohexane) and also aromatic compounds (1,3,5-trimethylbenzene, 1,3,5-triethylbenzene and 1,3,5-tri tri-tert-butylbenzene). The effects of the structure of the compound (alkylic cycle and aromatic ring) and the size of the molecule on the SOA yields is also investigated.
Photo-oxidation experiments were carried out in the atmospheric simulation chamber of the Foundation for Research and Technology-Hellas (FORTH-ASC). The instrumentation used included a scanning mobility particle sizer (SMPS) to measure the particle size distribution, a high-resolution aerosol mass spectrometer (AMS) to quantify the particle mass concentration and composition, and a proton transfer reaction mass spectrometer (PTR-MS) to monitor the organic vapor concentrations. Thermal desorption gas chromatography was also used for offline analysis of the gas-phase products of the reactions. The volatility distribution of the produced SOA was quantified combining thermodenuder and isothermal dilution measurements with the SOA yields.
In each experiment the basic procedure was to fill the chamber, which is a 10 m3 Teflon reactor, with dry, clean air, introduce dry ammonium sulfate particles, inject d9-butanol and the VOC, add the nitrous acid (HONO) and turn on the UV lights to initiate the SOA formation. The injection of the cyclic alkanes demanded heating the injection lines. Because the 1,3,5-tri-tert-butylbenzene is solid at room temperature, it was introduced with a vaporizer. Before each experiment the chamber was cleaned with dry, clean air for a full day.
The total SOA concentration in the chamber was calculated after the data were corrected for particle losses to the chamber walls. The AMS measurements were corrected also for the collection efficiency (CE) that was estimated in each experiment using the algorithm of Kostenidou et al. (2007). From the same algorithm the density of SOA was also estimated.
All the compounds were found to form a considerable amount of SOA. The cyclohexanes were found to have higher yields than the aromatic compounds. Our experiments indicated that aromatic precursors produce a more oxidized SOA than the cyclohexanes. The results of this study can be used in atmospheric chemical transport models for more accurate simulation of anthropogenic SOA formation.
REFERENCES
Kostenidou, E., Pandis, S. N., Pathak, R. K., Pandis, S. N., Kostenidou, E., and Pandis, S. N. (2007). Aerosol Science and Technology, 41, 1002–1010.
Tkacik, D. S., Presto, A. A., Donahue, N. M., and Robinson, A. L. (2012). Environmental Science and Technology, 46, 8773–8781.
How to cite: Pavlidis, D., Simonati, A., Florou, K., Vasilakopoulou, C. Ν., Matrali, A., Kaltsonoudis, C., and Pandis, S. Ν.: Secondary organic aerosol formation during the oxidation of large aromatic and other cyclic anthropogenic volatile organic compounds, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2421, https://doi.org/10.5194/egusphere-egu23-2421, 2023.
During the recent decade our molecular level understanding of secondary aerosol generation in the atmosphere has progressed tremendously. The old paradigm that ambient aerosol pre-stage formation necessitates long processing times with scarce oxidants in the atmosphere has been found flawed, and we are continuously learning how the increase in molecular oxygen content, and the corresponding decrease in vapour pressure, happen far faster than presumed. We are steadily approaching a situation where the classical “single compound, single SOA yield” type of a thinking becomes obsolete, and the mechanistic description at a molecular level is required to tackle the rapid formation of ambient secondary aerosol mass.
In the current work we have performed laboratory flow reactor experiments of monoterpene and aromatic compound (auto-)oxidation applying chemical ionization mass spectrometry (CIMS) for product detection. The experiments were complemented by high-level quantum chemical computations of the important mechanistic steps, and the energy non-accommodation was accounted for in the formation of the important intermediates (i.e., we investigated the role of excess reaction energy for the product formation). It has been learned that even in seemingly very disparate chemical systems the formation of condensable products occurs fast, often in sub-second time-scales.
How to cite: Rissanen, M., Kumar, A., Barua, S., and Iyer, S.: From volatile to non-volatile in sub second time-scales: rapid HOM formation in seemingly disparate chemical systems, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16598, https://doi.org/10.5194/egusphere-egu23-16598, 2023.
The oxygenated volatile organic compounds, including terpenoic alcohols (TAs) are emitted into the atmosphere mainly from vegetation; from plant resins, and to communicate with neighbouring plants and insects. Furthermore, biogenic alcohols, including menthol, borneol, fenchol, pinanediol and camphanediol are widely utilized in industries. Consequently, terpenoic alcohols are present in all environmental compartments: air, surface and cloud water, fog, and atmospheric particulate matter. Therefore, water provides an important reaction medium for the environmental processing of terpenoic alcohols.
Hydroxyl radical (OH) is the most important daytime atmospheric oxidant, and plays a fundamental role in the advanced oxidation processes in the gas phase as well as in the atmospheric waters. In the atmosphere, TAs partition into the clouds and fog droplets, where they can undergo aqueous oxidation by free radicals, mainly OH, which yields low-volatility products. These low-volatility, highly-oxygenated molecules contribute to secondary organic aerosols (SOA) and tropospheric ozone following their aqueous and multiphase oxidation. Hence, terpenoic alcohols are the potential precursors of aqueous SOAs (aqSOAs). Atmospheric aerosols are important climate forcing agents and also have a negative impact on human health. According to recent estimates, SOAs, including aqSOAs, contribute significantly to the global budget for fine particulate matter (PM).
The goal of this work is to investigate kinetics and mechanism of the aqueous phase oxidation of menthol, borneol, fenchol, pinanediol and camphanediol by the OH radicals. The rate coefficients measurements for reaction of TAs with OH radicals were carried out in the custom-designed aqueous photoreactor using relative rate method approach. The mechanism of the oxidation reactions under investigation were studied with gas and liquid chromatography coupled with the mass spectrometry. Such an approach provided detailed insights into the molecular structures and distribution of products, including neutral molecules (alcohols, carbonyls) and functionalized carboxylic acids. Yields of formation of the major products were also measured using a commercially available and synthesized standards (terpenoic acids). The detailed reaction mechanism of the OH-initiated reaction for five TA was proposed using the experimental data acquired. Subsequently, a box-model for the aqueous OH oxidation of the five terpenoic alcohols was developed and compared to the experimental data; the reaction channels and branching ratios of the major detected by-products were proposed. Atmospheric implications of the results obtained are discussed in the connection with the possible in-cloud formation following the OH oxidation of menthol, borneol, fenchol, pinanediol and camphanediol. Additionally, the rate coefficients and reaction mechanism information for TA reaction with OH radicals in water could be utilized for wastewater treatment.
How to cite: Jain, P., Witkowski, B., Kołodziejczyk, A., and Gierczak, T.: Investigation of the aqueous oxidation of terpenoic alcohols by OH as a potential source of secondary organic aerosols, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1301, https://doi.org/10.5194/egusphere-egu23-1301, 2023.
Biogenic volatile organic compounds (BVOC) are key precursors for the formation of secondary organic aerosol (SOA) and strongly impact air quality and climate change. To assess the role of BVOC and their transformation to SOA, we studied BVOC sources, concentrations, and their oxidation to SOA in an urban area in southwest Germany during a summertime heatwave episode. State-of-the-art mass spectrometers including a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) coupled with a new particle inlet chemical analysis of aerosol online (CHARON) and an aerosol mass spectrometer (AMS) were utilized to measure compositions and concentrations of particles and trace gases. By combining meteorological parameters (temperature, relative humidity, wind direction, wind speed, and radiation), potential sources of BVOC and SOA in this characteristic urban area during the summer heatwave of 2022 were identified. Potential sources as well as the influence of temperature on BVOC to SOA conversion will be discussed.
How to cite: Li, Y., Jiang, F., Zhang, H., Bian, Y., and Saathoff, H.: Biogenic volatile organic compounds concentrations and their conversion to oxidized VOCs and secondary organic aerosol particles, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12455, https://doi.org/10.5194/egusphere-egu23-12455, 2023.
Organic peroxy radicals (RO2) and stabilized Criegee intermediates (SCIs), as important reactive species in the atmosphere, are critical in oxidation processes and secondary organic aerosol (SOA) formation. However, the influence of temperature on these reactive intermediates and the corresponding reaction mechanisms in SOA formation is still not well defined. In this study, through utilizing SCIs scavengers and regulating [HO2]/[RO2] from ~0.3 to ~1.9, the roles of RO2 and SCIs in SOA formation were investigated at 298 K, 273 K, and 248 K, respectively, particularly for dimers formation in β-pinene ozonolysis. It was found that the dependence of the SOA yields on temperature was not monotonic. With the temperature decreasing from 298 K to 273 K, the SOA formation was promoted by the gas-particle partitioning of semi- and low-volatility products. However, when the temperature further decreased to 248 K, the SOA yields were lower due to the temperature effect on chemical reactions. The addition of SCIs scavengers showed that SCIs reactions accounted for more than 40% of both dimers and aerosol formation under all temperature conditions. The SCIs reactions predominantly contributed to the formation of C18 and C19 dimers. Increasing the [HO2]/[RO2] ratio suppressed SOA and dimers formation at all temperatures, indicating that in β-pinene ozonolysis RO2+RO2 reactions generate products of lower volatility, while RO2+HO2 reactions tend to form products of higher volatility. The lower RO2 concentrations and suppressed RO2+RO2 reactions could partly explain the reduced SOA yield at 248 K. Additionally, it was found that the sensitivity of dimers formation on [HO2]/[RO2] was higher at lower temperatures. Even though the impact of temperature on the reaction coefficients of peroxy radicals was considered, the dimers formation at different [HO2]/[RO2] ratios could not be explained well at 273 K and 248 K. This suggests that SCIs reactions with RO2 radicals may become more important at lower temperatures due to slower isomerization and decomposition of SCIs.
How to cite: Gong, Y., Saathoff, H., Jiang, F., Li, Y., and Leisner, T.: Roles of peroxy radicals and Criegee intermediates in β-pinene ozonolysis at different temperatures, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12594, https://doi.org/10.5194/egusphere-egu23-12594, 2023.
Aromatic compounds contribute significantly to the formation of secondary organic aerosol (SOA) that have implications on health and on climate. Toluene is the most abundant aromatic compound in the atmosphere and is emitted through anthropogenic activities such as incomplete combustion and industrial processes. To form SOA, participating vapors such as toluene need to have sufficiently low volatility, which in practice implies molecules with multiple oxygen containing polar functional groups called highly oxygenated organic molecules (HOMs). The oxidation of toluene by OH can lead first to bicyclic peroxy radicals (BPR), and then to HOM. While the formation of HOM has been shown to be efficient, the underlying molecular level mechanism has been challenging to accurately elucidate because of the sheer number of potential pathways. This leads to a major gap in the understanding of the formation of SOA from toluene in the atmosphere. In this work, we conclusively demonstrate for the first time that the toluene derived BPR is unstable under atmospheric conditions and undergoes spontaneous molecular rearrangement to lead to completely ring broken RO2s at rates competitive with bimolecular reactions with NO even under polluted conditions. Intriguingly, several of the closed shell products deriving from the BPR are likewise unstable and decompose in finite timescales. This is relevant for those aromatic compounds that lead to BPRs that are otherwise stable against rearrangement reactions, providing, e.g., a long-range transport vehicle for NOx similar to peroxyacyl nitrates (PAN). Using quantum chemical calculations and master equation simulations that account for energy non-accommodation, we elucidate the molecular level mechanism of the subsequent autoxidation of the ring broken RO2s that leads rapidly to the HOM O9-RO2. Furthermore, using targeted flow reactor experiments of the OH reaction of toluene and partially deuterated toluene with nitrate chemical ionization mass spectrometry (CIMS) detection, we corroborate the proposed new mechanism. This is the only unambiguous reaction pathway to toluene derived HOM reported to date, and it has implications on the aerosol and ozone forming potential of toluene.
How to cite: Iyer, S., Kumar, A., Savolainen, A., Barua, S., Garmash, O., Seal, P., and Rissanen, M.: Molecular rearrangement of bicyclic peroxy radicals: key route to aerosol from toluene, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15768, https://doi.org/10.5194/egusphere-egu23-15768, 2023.
Biogenic volatile organic compounds (BVOCs) emitted from a wide range of trees and plants undergo oxidation reactions in the atmosphere to produce secondary organic aerosol (SOA), which has direct and indirect effects on climate, and is accountable for a large proportion of climate uncertainties. The composition and yield of SOA is determined by the precursor BVOCs, which depends on the emission profile of the plant. In Ireland forestry is dominated by Sitka spruce (Picea Sitchensis), the emissions of which are not well characterised. The goal of this study is to identify the BVOC emissions from Sitka spruce, and to assess their SOA formation potential.
To characterise the emission profile of Sitka spruce, 4-year old trees were housed in a plant growth chamber under controlled environmental conditions and the emissions monitored on-line with a time-of-flight chemical ionisation mass spectrometer (ToF-CIMS), and off-line with thermal desorption gas chromatography mass spectrometry. The atmospheric reactions of the VOCs emitted by the Sitka spruce were investigated by oxidising them with hydroxyl (OH) radicals in an atmospheric simulation chamber. BVOC oxidation and gas-phase product formation was monitored by ToF-CIMS. A scanning mobility particle sizer (SMPS) was used to track particle formation and growth, and the SOA composition was determined with the use of a filter inlet for gas and aerosols (FIGAERO) fitted to the ToF-CIMS.
Over 60 different BVOCs were identified in the Sitka spruce emissions, with oxygenated species accounting for over 50% of them. The most abundant compound identified was piperitone, C10H16O an oxygenated monoterpene. Other compounds prevalent in the emissions included isoprene and monoterpenes, such as myrcene and β-phellandrene. During oxidation experiments the decay of the Sitka spruce emissions was observed with the ToF-CIMS in C6H6+ mode, while the formation of oxidised gas products was observed in I- mode. The most prevalent gas-phase product was C5H6O3. Analysis of the gas-phase oxidation products indicated that the oxidation of multiple BVOCs led to their formation. Particle formation and growth commenced quickly after the OH reaction was initiated. The composition of the SOA showed C6H8O6 as the dominant species, but the majority of the products had formulas in the range #C7 – 15 and #O5 - 8. Analysis of both gas and particle phase chemistry has been performed to determine the SOA formation potential of Sitka spruce BVOC emissions.
How to cite: Furnell, H., Kammer, J., Wingler, A., Kilcawley, K., Mannion, D., and Wenger, J.: Formation of secondary organic aerosol from sitka spruce emissions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14075, https://doi.org/10.5194/egusphere-egu23-14075, 2023.
Secondary organic aerosol (SOA) can undergo atmospheric aging processes that alter their impact on climate, air quality and human health. Transition metals, such as iron, can age SOA particles through catalytic chemical reactions within the condensed phase. Iron-containing particles originating from e.g., mineral dust, often become internally mixed with SOA, forming iron-containing SOA particles through various atmospheric processes, such as coagulation, condensation or cloud processing. When acidic organic vapors condense on iron-containing mineral dust particles, they can cause dissolution of minerals followed by iron-organic complex formation. Iron-organic complexes are common in atmospheric particles and can generate reactive oxygen species within a particle through dark peroxide and photochemical reactions (i.e., Fenton chemistry), leading to further aging of the particles by functionalization or fragmentation of organic species. Such particle-phase aging processes can considerably change the particle chemical composition. However, detailed understanding of these compositional changes is lacking to date, and hence considerable uncertainties still exist regarding the impact aged particles have on air quality and climate.
Here, we present detailed information on the chemical composition of iron-containing SOA particles and how it evolves over time. Particles were produced by forming SOA via α-pinene ozonolysis on both ammonium sulfate or iron-containing seed particles in an atmospheric simulation chamber under dark conditions. This allowed us to probe the impacts of iron on dark e.g., peroxide reactions and aerosol aging in the absence of photochemical driven Fenton chemistry, i.e., simulating nocturnal aging processes. Experiments were also conducted under both wet (relative humidity (RH) >80%) and dry (RH <10%) conditions. Aerosol bulk composition was determined using extractive electro-spray ionization mass spectrometry, allowing for high chemical and temporal identification of oxidation products, i.e., monomers and dimers, present within the particles. Under dry conditions, particles (both with and without iron) were found to contain a higher fraction of monomers, compared to dimers. Whereas under wet conditions the monomer/dimer ratio was smaller when iron was present. This suggests that iron-catalyzed functionalization reactions are favoured under wet conditions. Furthermore, when iron was present in the seed particles the lifetimes of monomers and dimers varied greatly, where the signal for some organic species (e.g., C19s and C20s) was observed to decrease rapidly (t1/2 ~ 25 min.) following SOA formation under wet conditions, while only slow decay was observed under dry conditions (t1/2 ~ 110 min.). This suggests that iron-catalyzed reactions are limited by diffusion of organic molecules under dry conditions. Overall, our results elucidate the key role of transition metals, such as iron, in altering the chemical composition of SOA particles during atmospheric transport. Such effects need to be considered to correctly reflect atmospheric aging of ambient SOA particles that are internally mixed with e.g., mineral dust, when predicting their role for air pollution and climate in atmospheric models.
How to cite: Garner, N., Top, J., Mahrt, F., El Haddad, I., Ammann, M., and Bell, D.: Dark aging of iron containing alpha-pinene secondary organic aerosol, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10852, https://doi.org/10.5194/egusphere-egu23-10852, 2023.
Reactive air pollutants and their secondary products are related to air quality and climate. The growing human activities (fossil fuel combustion, biomass burning, fertilizer use, and industrial activity) result in increasing negative impacts on ocean biota and marine resources. Aerosols in the marine atmosphere are episodically & dramatically influenced by long distance transport from continental regions. Monsoon climate, high population density and strong anthropogenic emissions in East Asia and Southeast Asia cause interaction of air pollutants between sea and land to affect air quality and climate change.
Our study based on two intensive measurements by ground sites, ship cruise, and aircraft in eastern of China in 2011 and southern and southwest of China in 2015.
The ship cruise measurements in the eastern coast of China indicated that the decline of the organic indicators for continental anthropogenic sources and the decline of PM and its major chemical compositions with longitude. The influence of Asian continental outflow during monsoon season was analyzed by identification of BC source regions at a receptor site of eastern coast of China. The variability in the relationship between BC and CO found BC aging during transport.
Two Mt. background sites and aircraft measurements to explore the influence of biomass burning (BB) in the South Asia to air quality in southern and southwest of China. The aloft BB transport was captured by aircraft observations to demonstrate impacts of springtime BB in Southeast Asia on atmospheric carbonaceous components over the Gulf of Beibu in China. Intensive BB activities in the South Asia were detected by fire maps. The long-range transport of BB pollutants can increase the accumulation mode particles in the background atmosphere at Mt. Yulong (3410 m). CCN concentration was 2-8 times higher during BB periods than during clean periods.
How to cite: Hu, M., Guo, Q., Shang, D., Wu, Z., Lu, S., and Guo, S.: Regional transport and formation of air pollutants between sea and land under the monsoon climate, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2334, https://doi.org/10.5194/egusphere-egu23-2334, 2023.
Aerosol-cloud interaction contributes to one of the highest uncertainties in radiative forcing estimations. Aerosols from ship emissions alter the cloud properties and have become an important source of anthropogenic air pollution in recent decades. We have measured the size distributions and number concentrations of aerosols in the cloud and outside clouds using various onboard instruments such as cloud droplet probe (CDP; DMT), passive cavity aerosol spectrometer (PCASP, DMT), Scanning Mobility Particle Sizer (SMPS) and Single Particle Soot Photometer (SP2; DMT). The measurements were performed in the ship emission-dominated environments and relatively cleaner regions of the Celtic Sea. We discuss the difference in the characteristics of in-cloud and out-cloud measurements in these relatively contrasting environments. The measurements were made between 29th September and 12th October 2021 using the Facility for Airborne Atmospheric Measurements (FAAM) research aircraft as a part of the Atmospheric Composition and Radiative forcing changes due to UN International Ship Emissions regulations (ACRUISE) Project.
How to cite: Thamban, N. M., Wu, H., Choularton, T., Coe, H., Bower, K., Matthews, E., Bannan, T., Marsden, N., Lee, J., Pasternak, D., Yang, M.-X., Batten, S., Bell, T., Temple, L., and Bauguitte, S.: Understanding the aerosol-cloud interactions in ship-dominated and cleaner environments in the Celtic Sea., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11259, https://doi.org/10.5194/egusphere-egu23-11259, 2023.
Arctic earth system is highly sensitive environmental change. Arctic warms up by 2-4 times faster than the rest of the world. Environmental changes in Arctic has a profound impact on the regional and global climate. Aerosol particles play an important role in Arctic climate system. Predicting how Arctic atmosphere will change in a warming world requires a better understanding of the state of aerosols now, as a baseline from which any predictions can be made. Motivated by this, we carried out field observations in the Arctic region during a research cruise and at ground stations. The overall aim is to improve our understanding on the sources and aerosol particles and their impact on the climate and clouds.
This presentation will show preliminary results from the DY151 research cruise (May-June 2022) to the Labrador Sea and the Davis Strait. The main objectives of the cruise include:
- Sources and processes of aerosol particles, cloud condensation nuclei and ice nuclei
- Source and processes of gaseous pollutants
- Formation and growth mechanism of new particles
- Improve modelling of aerosol sources and processes in the Arctic and predict the impact of potential increase in Arctic shipping on the clouds and climate in the future
Operations onboard included the measurement of atmospheric and oceanic parameters, including:
- size distributions of particles from 1 nm to 20 µm;
- gaseous pollutants such as volatile organic compounds, nitrogen oxides, HONO, HCHO, carbon monoxide, and sulphur dioxide;
- molecular clusters and highly oxygenated organic compounds that contribute to the formation and growth of new particles;
- chemical composition of aerosol particles including both organic tracers and inorganic species, and black carbon;
- particle mass concentrations;
- cloud condensation nuclei and ice nuclei concentrations;
- optical observations of atmospheric particles and radiation; and
- surface ocean chlorophyll a concentrations and routinely measured parameters onboard such as salinity.
These comprehensive observations will allow to better understand (1) the emissions, sources, and oxidation of key gaseous pollutants, (2) formation and growth of new particles, (3) contribution of newly formed particles to cloud condensation nuclei, and (4) sources of aerosol particles, cloud condensation nuclei and ice nuclei.
How to cite: Du, M. and Shi, Z.: Aerosol source and processes in the Arctic, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15676, https://doi.org/10.5194/egusphere-egu23-15676, 2023.
The biogeochemical behaviour of the Southern Ocean is extremely complex and dynamic. The processes that effect this behaviour in the Southern Ocean are highly dependent on radiative (e.g. sunlight), chemical (e.g. nutrient availability) and biological (e.g. phytoplankton) constraints. We aim to assess how the Southern Ocean DMS emissions change when the underlying biological constraints on the production of DMS are altered across time and space.
Using a nudged configuration of the atmosphere-only Earth System Model, UKESM1-AMIP, we performed two sets of four different 10-year simulations from 2009 – 2018. One set tested four different seawater DMS data sets (Anderson et al. 2001, Hulswar et al. 2022, Lana et al. 2011, ), while the other set tested four different DMS sea-to-air flux parameterisations (Goddijn-Murphy et al. 2016, Liss and Merlivat 1986, Nightingale et al. 2000, Wanninkhof 2014). Our goal is to evaluate the variability in each stage for atmospheric DMS formation using four sea-to-air parameterizations and four oceanic DMS sources.
Using a quadratic sea-to-air flux (Wanninkhof (2014) and Nightingale et al. (2000)) provides high transfer velocities in DMS, creating a positive bias across most areas of the Southern Ocean, except for biologically productive areas, such as the high latitude regions. Although the Southern Ocean atmospheric DMS average corresponds well to observations using quadratic formulas, large areas of the Southern Ocean have lower measured atmospheric DMS than model simulations. Linear relationships between wind and flux are shown to be more realistic. We find that there is a greater range of outcomes from the different sea-to-air flux parameterizations (2.84 TgS Yr-1 to 7.44 TgS Yr-1) than from the different oceanic DMS datasets (3.37 TgS Yr-1 to 7.29 TgS Yr-1). This work highlights the need for Earth System Models to include a sea-to-air parameterization that is more appropriate for DMS, and for oceanic DMS datasets to capture the time-varying nature of biological activity. Such improvements would help provide more accurate and realistic simulations of DMS in the Southern Ocean.
How to cite: Bhatti, Y., Revell, L., Alex, S., Adrian, M., Alex, A., Jonny, W., and Erik, B.: Southern Ocean Emissions of DMS, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1108, https://doi.org/10.5194/egusphere-egu23-1108, 2023.
Water covers about 71 percent of the Earth’s surface (i.e., oceans, glaciers) and it is crucial for all the biological systems. Although bulk water is inert, water microdroplets provide a favourable environment for chemical processes. The investigation and the understanding of the physico-chemical processes that occur in the atmospheric aerosols is of great importance, while aerosols is well-known that have an adverse effect in air-quality, climate and public health. In the air-water interface the presence of a strong electric field can lead to the acceleration of chemical reactions and initiate spontaneous reduction of organic compounds. Our study is focusing on the spontaneous H2O2 production at the interface of water droplets, which occurs via the recombination of the hydroxyl radicals that are formed via the dissociation of hydroxyl ions, while other pathways cannot be excluded. H2O2 may play a key role in the oxidation of atmospheric aerosols and therefore, it may alter the oxidation capacity by increasing the production of radicals.
Within this framework, a thorough laboratory study, using state-of-the-art instrumentation has been carried out. Two different types of experiments were performed, where the H2O2 and thus the OH production was measured either directly or indirectly by using sensitive water-soluble fluorescent probes. Aqueous microdroplets, in a range of diameter 0.1 to 10 µm were generated by nebulizing salted solutions inside a glass reactor. These particles were then collected after 4 hours reaction time and the liquid phase H2O2 was measured by using an H2O2 analyser. During our experiments, an Optical Particle Counter was connected in order to monitor the size distribution and the number of the particles. To extend our understanding in the processes that occur at the interface, different types of salts were selected (NH4Cl, Na2SO4 and CaSO4) in order to investigate the way that different ions of different valence affect the H2O2 production. A correlation between the size distribution and the hydrogen peroxide concentration was also performed. In order to verify the OH production, salted solutions containing terephalic acid (TA) were also nebulised inside the reactor. The collected droplets were analysed via fluorescent spectroscopy where the 2-hydroxyterephthalic acid (TAOH), product of the reaction of TA with OH radicals, was observed. TAOH was also observed in the particle phase in a size range of 1–5 µm.
All the experiments provide evidence that H2O2 is produced in the air-water interface of microdroplets at a range of (1–7)×10-2 µM, which depends on the size distribution, the concentration of the solution and the type of salt. Results from this study are expected to significantly improve our insight on the processes that occur in atmospheric droplets and to assess the contribution of this OH radical source in total atmospheric budget.
How to cite: Angelaki, M., Carreira Mendes Da Silva, Y., and George, C.: Spontaneous Formation of OH Radicals in the Air-Water Interface of Water Droplets, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12438, https://doi.org/10.5194/egusphere-egu23-12438, 2023.
Aerosol observations always suffer from limited sampling, be they in-situ or remote sensing measurements. This introduces representation errors when using these observations to derive regional estimates, or when using them to evaluate models. In the latter case, one can collocate the model data with the observations to alleviate the problem. The downside is that only part of the model data (the collocated part) can be compared to observations).
We present a technique to homogenize observations (i.e. "remove" their limited sampling). In essence, this is possible because aerosol exhibits spatial and temporal correlations. In practice, we use models to provide this information. Here the technique is applied to satellite data.
First we use synthetic observations to show that remaining representation errors due to this homogenization technique are below 10%. Next, we show that after applying this homogenization technique, estimates of regional AOD (or AAOD) from 14 (or 5) different observational datasets are far better in agreement than without homogenziation. Lastly, we present evidence that remaining differences in homogenzied (A)AOD in these daatsets is dominated by retrieval error.
We also discuss the evaluation of AEROCOM models with these homogenized data. In particular, we highlight existing biases in modelled AAOD.
Although we have not tried it yet, the technique should also be applicable to in-situ data.
How to cite: Schutgens, N. and the AEROCOM modellers & AEROSAT retrieval specialists: How to derive regional/global averages from sparsely sampled data, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1782, https://doi.org/10.5194/egusphere-egu23-1782, 2023.
The chemical composition of the aerosol phase is still a major uncertainty in global chemistry climate models. One the one hand, aerosol thermodynamics calculations are needed to determine the chemical composition of the inorganic fraction of the aerosol particles, on the other hand these calculations are computationally expensive. However, to properly describe the combined gas and aerosol phase composition, e.g., the reactive nitrogen budget including HNO3 or chlorine displacement from sea-salt aerosol, it is mandatory to have a reasonable description of the aerosol thermodynamics. To overcome the computational costs, but to still obtain a reasonable degree of proper process description, a machine learning approach for the aerosol thermodynamics might offer opportunities in CCM modelling.
In this study, we embed a machine learning approach for the description of aerosol thermodynamics in the chemistry climate model EMAC to reduce computational load (compared to explicit thermodynamics calculations) and show the capabilities of a modern computing approach, implemented in a multi-modal aerosol scheme.
The new aerosol thermodynamics scheme is formulated as a machine learning neural network, which has been trained with the help of an explicit inorganic aerosol thermodynamics box model, i.e. ISORROPIA-2.
This study presents first results of global 3D simulations using the ML approach and compares the results to explicit calculations in terms of the spatio-temporal distribution of the aerosol chemical composition as well as the effective performance of the modelling system.
How to cite: Tost, H., Bruening, S., Niebler, S., and Spichtinger, P.: A Machine Learning approach to aerosol thermodynamics embedded in aglobal chemistry-climate model, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5521, https://doi.org/10.5194/egusphere-egu23-5521, 2023.
The transport of Saharan dust to the mountain range of Sierra Nevada occurs recurrently as well as episodically and represents an important source of nutrients for its ecosystem. At the same time, the mountain range is also vulnerable to the radiative effects, changing albedo and reduced snow covers attributed to the deposited particles from various natural and anthropogenic sources. A two-year campaign was conducted from June 2018 to August 2019 in the Sierra Nevada at 2500 m MSL (site: Albergue Universitario de Sierra Nevada) and simultaneously samples were also taken from Granada, a city lying in the foothills of Sierra Nevada (site: Faculty of Sciences, University of Granada, 670m MSL). The aim was to deduce the various sources acting over two distinct environments within a short-range distance (22 km). Deposition samples were collected on a carbon substrate using a flat plate sampler (passive method) with a sampling period of 40-72 hours. An average of 10 samples were collected per month from both sites and the current study focuses mainly on the summer months of June, July, and August when episodic dust events were observed. Along with the dust episodes, control days samples were also taken when no rain event or dust event occurred.
Single particle microscopy coupled with energy-dispersive X-ray analysis was utilized to get the chemical information on approx. 100,000 single particles over the size range of 0.5- 50 µm projected area diameter. The particles were classified according to a definite set of rules, and the main chemical classes as dust-like, sulphates, and salts-like and their mixtures were derived. Particles which didn’t fit into any of these classes were named ‘other’ classes. The focus of the results includes the relative abundance of these classes and their particle morphology (size and shape) over the two locations affected by different aerosol sources. Furthermore, the characteristics of iron-rich particles and iron content in the other dust particles were also studied given their importance in absorption properties and bioavailability for ecosystems. During the dust event days, the relative number abundance of chemical composition at Sierra Nevada showed >98 % of dust particles enriched in silicate type in the particle size range >1 µm while the <1 µm had a significant percentage in sulphates (>20%). Meanwhile at Granada, even though the dust events had an influence on the composition with higher dust content (>90%) for diameter >5µm modes, the lower size range presented higher fractions of anthropogenic particles consisting of sulphates and other particle types.
How to cite: Sudharaj, A., Orza, J. A. G., Gomez-Cascales, P. J., Suarez, V. M. E., Milena-Perez, A., Ferro-Garcia, M. A., and Kandler, K.: Deposition and mineralogy of atmospheric dust at Sierra Nevada and Granada (Andalusia, SE Spain): A single particle perspective, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10787, https://doi.org/10.5194/egusphere-egu23-10787, 2023.
Posters on site: Tue, 25 Apr, 08:30–10:15 | Hall X5
A phase state of ambient aerosols is a key parameter to understand physicochemical properties of aerosols such as growth rate, size distribution, and mass concentration that affect climate and human health. However, only limited information of real aerosol phase states has been obtained. Herein, to explore phase states of fine particulate matter (PM2.5) in megacities, we collected daily PM2.5 filter samples during December 2020 – January 2021 in Seoul and Beijing. Optical microscopy and a poke-and-flow technique were used to observe the morphologies and phase states of the PM2.5. Results showed that the average phase states of the PM2.5 were significantly different in the two megacities. The PM2.5 existed as a liquid state to a semisolid in Seoul while it existed as a semisolid to a solid in Beijing. These differences were governed by the chemical composition of PM2.5 and aerosol liquid water content. Furthermore, the phase state of PM2.5 in two megacities was correlated with particle size distribution. Our findings can provide an understanding of the phase states of real-world aerosols and how the phase state is linked to chemical compositions, ALWC, and size distributions of PM2.5.
How to cite: Kim, D., Jeong, R., Qui, Y., Meng, X., Wu, Z., Zuend, A., Ha, Y., Kim, C., Kim, H., Gaikwad, S., Jang, K.-S., Lee, J., Ahn, J., and Song, M.: Phase state of PM2.5 in Seoul and Beijing and its effect on particle size distribution, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-253, https://doi.org/10.5194/egusphere-egu23-253, 2023.
The air quality in the Metropolitan Area of São Paulo (MASP) is influenced by local sources of pollution, mainly from vehicles and industries, but there is a concern about the role of remote sources in the concentration of particulate matter, such as biomass burning plumes, which occur mainly in the interior regions of Brazil. During the dry period (mainly between July and October), the central region of Brazil suffers from biomass burning, which releases large quantities of gases and particles into the atmosphere and not only affects nearby cities, but also regions hundreds of kilometers away, as is the case of the city of São Paulo.This study aimed to evaluate the concentration of PM10, PM2.5and Aerosol Optical Depth (AOD) between 2005 and 2022, identifying seasonal variations, spatial distribution, frequency, meteorological influences, and the main sources of the aerosol, including understanding and quantifying the impact of burning events on air quality in the MASP.The surface pollutant data, meteorological data, and AOD data were provided, respectively, by: São Paulo Environmental Company (CETESB; https://cetesb.sp.gov.br/ar/qualar/),Institute of Astronomy, Geophysics andAtmospheric Sciences (IAG/USP; http://www.estacao.iag.usp.br/)and Aerosol Robotic Network (AERONET;https://aeronet.gsfc.nasa.gov/).The results indicate a downward trend for aerosol, since several public policies were implemented in the period, but the values are still far above the standards recommended by the World Health Organization (WHO), especially in the winter months (June-September), due to meteorological conditions. Burning events that affect the MASP (more frequent in September) contribute to the increase of particle concentrations at the surface,as well as to the increase of AOD, related to the frequency of northwest wind direction in these eventsandalsoto the number of fire spots in the country.
How to cite: Oliveira, M. and Miranda, R. M.: Understanding the role of forest fires in urban pollution in São Paulo, Brazil, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-325, https://doi.org/10.5194/egusphere-egu23-325, 2023.
To explore aerosol chemistry and climate change, information of the physical state of aerosol particles is essential. Herein, we measured viscosities of binary mixtures of sucrose/H2O and ammonium sulfate (AS)/H2O, and ternary mixtures of sucrose/AS/H2O with different organic-to-inorganic dry mass ratios. For sucrose droplets, the viscosity gradually enhanced from ~4 × 10-1 to > ~1 × 108 Pa‧s as the relative humidity (RH) decreased from ~81% to ~24%. This corresponds from liquid to semisolid or solid state. For AS droplets, the viscosity dramatically enhanced at ~ 50% RH upon dehydration; to be < 102 Pa‧s for RH > ~50% (liquid state), and > ~1 × 1012 Pa‧s for RH ≤ ~50% (solid state). In case of the ternary mixtures, remarkable enhancement in viscosity was observed as the inorganic ratio increased at a given RH. All particles studied in this work were observed to exist as a liquid, semi-solid or solid depending on the organic-to-inorganic dry mass ratios and RH. Moreover, the measured viscosities of the binary and ternary mixtures were compared with the calculated viscosities using the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients Viscosity model (AIOMFAC-VISC) predictions with the Zdanovskii–Stokes–Robinson (ZSR)-style organic–inorganic mixing model. It showed excellent model–measurement agreement. The result will be discussed.
How to cite: Song, M., Jeong, R., Lilek, J., Zuend, A., Xu, R., and Chan, M.: Viscosity and physical state of sucrose/ammonium sulfate/H2O droplets , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-995, https://doi.org/10.5194/egusphere-egu23-995, 2023.
In this study, principal component analysis (PCA) was utilized to identify the sources of water-soluble and water-insoluble metal content of coarse and fine PM in the air. The sampling campaign was conducted in winter (December 2021-February 2022) at the University of Southern California Particle Instrumentation Unit (PIU) in central Los Angeles. Ambient PM2.5 and coarse PM samples were collected on Teflon filters and chemically analyzed to quantify their water-soluble and total metal content. The Multiple Linear Regression (MLR) model was employed to investigate the contribution of each found factor by PCA to the total metal. The most abundant elements in the fine size range were Na, S, Fe, Al, and Ca, while in the coarse range, they were Na, Fe, Ca, Al, and Mg. Ca, Na, and Zn exhibited the highest solubility levels in both size ranges, while Ti, Fe, and Al showed the lowest solubility. Most metals had higher solubility in the fine size fraction. The PCA results indicated that the tire and brake wear source factor contributed significantly to the water-soluble fraction of metals in both size ranges, whereas the soil and re-suspended road dust source factor had the most contribution to the water-insoluble fraction of metals. The primary source of fine water-soluble metal was metal-dominated abrasion due to its higher water-soluble content, typically corresponding to a greater impact of anthropogenic than crustal sources. MLR results confirmed that tire and brake wear are major sources of metal in the water-soluble fractions of both size ranges, while soil and re-suspended road dust are major sources in the water-insoluble portion.
How to cite: Sioutas, C., Badami, M. M., Tohidi, R., and Jalali Farahani, V.: Source apportionment of water-soluble and water-insoluble metal content of coarse and fine PM in central Los Angeles, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1608, https://doi.org/10.5194/egusphere-egu23-1608, 2023.
Aerosols have drawn great scientific interests in the past decades dur to their essential roles in the nucleation of ice, clouds, radiation budget and climate change. Light-absorbing carbonaceous particles (LACs), including black carbon (BC) and brown carbon (BrC), are important radiatively-active aerosols in the atmosphere. In this research, we will present the emissions and physicochemical properties of BC and BrC particles. We will try to figure out the contribution of BC and BrC respectively, by combining results from instrument measurement (photoacoustic extinctiometer and aethalometer) and the analysis of aerosol samples collected on filters (UV/vis spectrometry and LC-TOF-MS). In the end, we would like to show the impacts of LACs in cold-climate sites, comparing with warm-climate sites.
How to cite: Li, H. and Ariya, P.: The Emission and Physicochemical Properties of Light-Absorbing Carbonaceous Particles at A Cold-Climate Site, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2936, https://doi.org/10.5194/egusphere-egu23-2936, 2023.
Humic-like substances (HULIS) are complex macromolecular components of light-absorbing water-soluble organic carbon (brown carbon; BrCaq) consisting of polyacidic and monocyclic/polycyclic structures. HULIS contribute to climate forcing via strong absorption at UV and near-visible wavelengths, and by facilitating the formation of cloud condensation nuclei. Consequently, characterization of the HULIS fractions of BrC is critical to develop a robust understanding of its sources, atmospheric processing and optical effects. To address this issue, we report HULIS fractionation from bulk BrCaq by pH-based multi-step solid phase extraction (hydrophobic fraction at pH=7: neutral HULIS (H-n); hydrophilic fraction at pH=2: acidic HULIS (H-a)) and corresponding optical (UV-Vis and 3D-fluorescence) and chemical properties (1H NMR and FT-IR) on a diurnal and seasonal basis. The study was conducted on PM2.5 samples collected in the eastern part of the Indo-Gangetic Plain (IGP), which is dominantly affected by marine airmasses mixed with fossil fuel emissions during summer, and biomass burning emissions in the IGP outflow during post-monsoon and winter.
Distinct diurnal and seasonal variations were observed for optical and chemical signatures of bulk BrCaq and HULIS fractions. At 365 nm, daytime absorption of BrCaq, H-n and H-a was 3-13 times higher in post-monsoon and 2-8 times higher in winter as compared to summer while that for nighttime samples were enhanced by factors of 2-7 and 3-13, respectively. These possibly point towards greater emission intensity and/or enhanced dark-phase formation of soluble chromophores of BrCaq and H-n during nighttime and an enhanced presence of conjugated aromatics during post-monsoon and winter. On the other hand, enrichment of H-a during daytime might be due to increased polarity of oxidation products via photochemical processing. Excitation-emission matrix fluorescence coupled with the parallel factor analysis (PARAFAC) model identified two types of HULIS (condensation and degradation) and combinations of tryptophan and tyrosine type protein-like substances (PRLIS) in BrCaq across seasons, with higher PRLIS abundance (78%) in summer associated with marine biogenic emissions and higher HULIS abundance in post-monsoon (62%) and winter (67%) linked to regional biomass burning. H-n showed greater humification during nighttime as compared to day (0.74-1.92 vs. 0.67-1.15) while H-a was more humified during daytime (0.62-1.54 vs. 0.57-1.34), suggesting that the degree of unsaturation in H-a was associated with the atmospheric ageing process. Aliphatics (H-C) were the most abundant group among BrCaq, H-n and H-a, accounting for about 35-51% of total organic hydrogen throughout the seasons. An increased contribution of H-Ar was observed in H-a (8-24%), followed by H-n (2-19%) and BrCaq (7-14%) suggesting dominance of conjugated aromatics in the HULIS fractions. In BrCaq, aliphatic groups (O-H, N-H, C-H) were dominant in summer, consistent with transported fossil fuel emissions, while biomass burning-derived aromatic signatures (phenolic O-H, C=O, C=C) were prominent during post-monsoon and winter. In contrast, HULIS fractions showed aliphatic signatures of O-H and –COOH- throughout the seasons. Overall, these findings provide the first insights into the source- and atmospheric processing-dependent chromophoric composition of BrC over the IGP.
How to cite: Sarkar, S. and Dey, S.: Polarity-based chemical characterization of humic-like substances (HULIS) in the Indo-Gangetic Plain (IGP) and linkage with optical signatures of aqueous brown carbon , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3022, https://doi.org/10.5194/egusphere-egu23-3022, 2023.
The mass extinction efficiency(MEE), which indicates the degree of aerosol extinction(scatter and absorption) per unit PM mass concentration, is an important factor in converting optical concentration into mass concentration. Because its value varies depending on the particles' size and composition, which are particles' characteristics. In this study, the extinction coefficients of coarse and fine particles were calculated using the LiDAR data of Seoul observed by NIES(Japan's National Institute of Environmental Studies) and the visibility data of Seoul observed by the Korea Meteorological Administration. In the case of lidar data, two wavelengths (532nm, 1064nm) measured by lidar were used to calculate extinction coefficients, and the wavelength of 532 nm (532P and 532S) were used to classify extinction coefficients into coarse particles(PM10-2.5) and fine particles(PM2.5). In the case of visibility data, the PM10 and PM2.5 extinction coefficients were calculated using the equation of Koschmieder (1924) and Cheng et al. (2017). The PM10, PM10-2.5, and PM2.5 respective MEE were calculated using Seoul data of PM10 and PM2.5 at the same time provided by the Korea Environment Corporation. The relative humidity data provided by the Korea Meteorological Administration were divided into seven sections less than 40%, 40~49%, 50~59%, 60~69%, 70~79%, 80~89%, and 90~100%. According to relative humidity, this study examined the change of the calculated MEE. This study analyzes the effect of relative humidity on the Hygroscopic Growth of PM10, PM10-2.5, and PM2.5.
How to cite: Joo, S., Sim, J., Kim, J., Lee, Y., and Noh, Y.: Analysis of Mass Extinction Efficiency variation according to relative humidity using lidar and visibility data in Seoul, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3072, https://doi.org/10.5194/egusphere-egu23-3072, 2023.
Atmospheric aerosols are of great concern due to their impacts on human health, visibility, and climate. Sub-3 nanometer particles are initially formed through gas-to-particle conversion with a typical size of 1-3 nm, which is crucial for understanding the steps of new particle formation and sources of aerosol particles in the atmosphere. In this study, sub-3 nm particle concentration was measured from 2018 to 2020 at SORPES station in the Yangtze River Delta, China by particle size magnifier (PSM). Based on three years’ measurement, a high number concentration of sub-3 nm particles was observed all year round. Sub-3 nm particle concentration in polluted urban environments is two orders of magnitude higher than that in clean environments, e.g., Hyytiälä. Moreover, formation rates and growth rates of sub-3 nm particles were calculated in these 3 years. The formation rate in anthropogenic pollution regions is much higher than that in the clean environment, while the growth rate is similar to other field observations. Besides the secondary formation of sub-3 nm particles via new particle formation, we found traffic primary emission is a neglectable source of sub-3 nm particles in the urban area. We estimated the contribution of traffic emission and new particle formation on sub-3 nm particle concentration using sulfuric acid and NOx concentration as tracers. During the daytime, the contribution of traffic emissions can be over 50% on non-NPF-event days, and the contribution even comes to 13% on NPF-event days. During the nighttime, the contribution of traffic emissions can be up to 70%. Furthermore, in some conditions, synergistic effects of traffic emission and new particle formation can happen in the daytime, which causes an extremely high concentration of sub-3 nm particles. Our study also suggests that regional and global air quality models should consider traffic emissions as a primary source of sub-3 nm particles in anthropogenic pollution areas.
How to cite: Chen, L.: High Number Concentration of Atmospheric Sub-3 nm Particles in Polluted Environment of East China: three-year Observation at SORPES Station, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3958, https://doi.org/10.5194/egusphere-egu23-3958, 2023.
SPARTAN (Surface Particulate Matter Network) is a network of Particulate Matter (PM) samplers that analyze aerosol samples for PM mass concentration and chemical composition. Two aerosol samplers were installed at two sites in Korea: Yonsei University at Seoul and UNIST (Ulsan Institute of Science and Technology) at Ulsan. These SPARTAN filter samplers and additional nephelometers provide the PM2.5 mass concentration and reconstructed chemical speciation data (May, 2019~ Nov, 2021). In most SPARTAN PM2.5 cases, both sites showed time series patterns similar to data from the Korean regional observation network (Airkorea). In the case of high-loading fine dust, the daily value was relatively well matched with Airkorea data. The co-location of these SPARTAN samplers with AERONET (Aerosol Robotic Network) sun photometer presents the possibility of analyzing aerosol optical depth, aerosol surface mass concentration, and aerosol speciation data together. If the fraction of a particular component is high, the optical properties may vary. When the mass concentration of sulfate was relatively high, AERONET data displayed a large distribution of non-absorbing small particles. Similar to the previous analysis, we also show a detailed analysis of the relationship between other chemical components and optical properties.
How to cite: Eom, S., Kim, J., Lee, S., Cho, Y., and Park, S. S.: Relationship of aerosol optical properties and particle types from SPARTAN and AERONET data in South Korea, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4702, https://doi.org/10.5194/egusphere-egu23-4702, 2023.
PM2.5, defined as particulate matter less than 2.5 μm, is derived from a variety of natural and anthropogenic sources. Studies have shown that PM2.5 adversely affects human health, causing various respiratory and cardiovascular diseases. One of the methods to assess the potential health impacts of PM2.5 is to measure its oxidative potential, which refers to the ability of the particles to generate reactive oxygen species when inhaled into the lungs. In this study, antioxidants including ascorbic acid (AA) and reduced glutathione (GSH) as well as dithiothreitol (DTT) were used to measure the oxidative potential of PM2.5 collected in Chuncheon, a medium-sized residential city of South Korea. The degree of oxidation of antioxidants and DTT were measured using a spectrophotometric assay. In addition, a detailed PM2.5 compositions including NO3-, SO42-, NH4+, organic carbon (OC), elemental carbon (EC), metallic elements, and individual organic substances were measured to identify the characteristics of high PM2.5 concentration episodes (HCE) and to determine the association between chemical components with oxidative potential.
PM2.5 concentrations were generally higher in fall than in summer, and OC was the biggest contributor to PM2.5 mass. Among organic matters, sugar compounds, the marker species of biomass burning, were prominent while dicarboxylic acids, predominantly secondarily formed in atmosphere, were important in summer. For HCEs, NO3- and dicarboxylic acids increased the most among PM2.5 components, suggesting that secondary formation was important to enhance PM2.5 concentration. Nitrogen oxidation ratio (NOR) also increased during HCEs, and there was statistically significant correlation between NO2 and NO3-, possibly indicating that in situ oxidation of NO2 and/or gas-aerosol partitioning for HNO3 and NO3- occurred. Average OP measured by depletion of AA (OPAA), GSH (OPGSH), and DTT (OPDTT) were 4.5 ± 1.1, 4.9 ± 1.3, and 17.7 ± 5.9 pmol min-1 mg-1, respectively, during summer. All three OPs were especially low for the sample obtained when Asian dust event occurred. PM2.5 mass concentration was successfully reconstructed by EC, ∑n-Alkane, Ca2+, SO42–, and OC from multiple linear regression while oxidative burden by GSH (OBGSH) was explained by EC and ∑PAHs. These different results between PM2.5 mass and OP suggest that the PM2.5 concentration alone is not sufficient to explain the association with health effects.
How to cite: Park, S.-W., Han, Y.-J., Jeon, J.-W., Hong, J.-H., Lee, H.-W., Hong, S., Koo, J.-H., and Kim, Y.-K.: Oxidative potential and chemical characterization of PM2.5 in a medium-sized residential city of South Korea., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4891, https://doi.org/10.5194/egusphere-egu23-4891, 2023.
The source apportionment of organic aerosols (OA) in background locations is one of the important issues in contemporary air quality protection. A better understanding of the atmospheric aerosols origin and their source apportionment in different locations is essential for improving air quality.
Measurements of non-refractory PM1 (NR-PM1) were simultaneously performed during winter (1st February – 10th March) and summer (1st July – 20th August) 2021 at three background sites, National Atmospheric Observatory Košetice (N 49°35′, E 15°05′; 534 m a.s.l.) and Frýdlant (N 50°94′, E 15°07′; 366 m a.s.l.) in Czech Republic, and Melpitz (N 51°32', E 12°56'; 86 m a.s.l.) in Germany. Each site was equipped with an Aerosol Mass Spectrometer: a ToF- Aerosol Chemical Speciation Monitor (ToF-ACSM) at Košetice, a Compact Time-of-Flight Aerosol Mass Spectrometer C-ToF-AMS) at Frýdlant, and a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) at Melpitz.
A Positive Matrix Factorization (PMF) with multi-linear engine (ME-2) using Source Finder (SoFi) (Canonaco et al., 2013) was applied to OA data sets to separate OA into different factors in terms of their mass spectra and time series. Four sources of OA were identified for the winter season. Three of these sources, hydrocarbon-like organic aerosol (HOA), biomass burning organic aerosol (BBOA), and coal combustion organic aerosol (CCOA), belong to the primary sources. The last factor, designated oxidised organic aerosol (OOA), belongs to the secondary sources. Four sources of OA have also been identified for the summer season. Two of these sources were designated as primary sources (HOA and BBOA) and two as secondary sources, more oxidized organic aerosol (MO-OOA) and less oxidized organic aerosol (LO-OOA).
Acknowledgements:
This work was supported within a German-Czech cooperation in the TRACE project funded by the GACR under grant 20-08304J and by DFG under grant 431895563, also by the MEYS of the Czech Republic under grants ACTRIS-CZ LM2018122 and ACTRIS-CZ RI (CZ.02.1 .01 / 0.0 / 0.0 / 16_013 / 0001315), and European Union's Horizon 2020 research and innovation program ACTRIS IMP (871115).
Reference:
Canonaco, F., Crippa, M., Slowik, J. G., Baltensperger, U., Prévôt, A. S.: SoFi, an IGOR-based interface for the efficient use of the generalized multilinear engine (ME-2) for the source apportionment: ME-2 application to aerosol mass spectrometer data, Atmos. Measur. Tech., 6(12), 3649-3661, 2013.
How to cite: Lhotka, R., Pokorná, P., Vodička, P., Zíková, N., Ondráček, J., Mbengue, S., Arora, S., Poulain, L., Herrmann, H., Schwarz, J., and Ždímal, V.: Origin and transformation of organic aerosol at three background sites in Central Europe, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5085, https://doi.org/10.5194/egusphere-egu23-5085, 2023.
The aim of the study was to analyze the impact of very fine atmospheric particles (submicron particulate matter; PM1) on visibility deterioration. Taking into consideration not only their entirely different physio-chemical properties in comparison to a well-recognized PM10 but also the origin and a growing environmental awareness of PM1, the main research problem has been solved in few steps. At first, the chemical composition of PM1 was determined in two selected urban areas in Poland. Measurements of meteorological parameters, i.e., air temperature and humidity, precipitation, atmospheric pressure, wind speed, and visibility, were also conducted. The next step of the work was the analysis of (1) seasonal changes of the concentration of PM1 and its main components, (2) the influence of chemical components of PM1 on light extinction, and (3) the influence of PM1 and humidity on visibility. Hierarchical cluster analysis, correlation matrixes and a heat map, and classification and regression tree analysis were used. The light extinction coefficient is influenced mainly by coarse mass of PM, and PM1-bound ammonium nitrate, organic matter, and by Rayleigh scattering. The less important in the light extinction coefficient shaping has PM1-bound ammonium sulfate, elemental carbon, and soil. In this way, the secondary origin PM1 components were proved to most significantly influence the visibility. The obtained results confirmed the possibility of the use of statistical agglomeration techniques to identify ranges of variation of visibility, including independent variables adopted to analyses (meteorological conditions, chemical composition of PM1, etc.).
How to cite: Anioł, E., Majewski, G., Rogula-Kozłowska, W., Szeląg, B., Rogula-Kopiec, P., Brandyk, A., Walczak, A., and Radziemska, M.: New insights into submicron particles impact on visibility, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5289, https://doi.org/10.5194/egusphere-egu23-5289, 2023.
The vertical distribution of black carbon (BC) as well as its mixing state is of great concern due to BC’s strong regional climatic and environmental effects. In this study, vertical measurements were conducted through a moveable container based on a meteorology tower in an urban area. A total of 112 vertical profiles (0-240 m), including the concentrations of BC, O3, NOx and the optical properties of aerosols, were obtained. Based on BC concentration, the vertical profiles could be classified into four categories: uniform, gradual decrease, sharp decrease, and sudden increase. The uniform type indicates strong vertical mixing with similar pollutant concentrations along the vertical direction. The gradual/sharp decrease types indicate stable vertical conditions with higher pollutant concentrations on the ground and lower concentrations at higher altitudes. Due to the strong radiation in summer, the vertical profiles exhibited a clear diurnal variation in which ~80% of profiles were uniform during the daytime and ~40%-90% of profiles were gradual/sharp decrease types at night. O3 is an exception, and its concentration generally increases with height even under strong vertical mixing conditions. The size distribution of BC core varied slightly along the vertical direction, and the coating thickness of BC increased with height under stable conditions. However, the vertical variation in BC concentration is much more significant than BC coating thickness and plays a more critical role in the determination of BC absorption ability vertical distribution. In addition, O3 and Dp/Dc occasionally increased during 6:00-8:00 but remained stable during 8:00-10:00. Vertical mixing and transportation from upper heights, such as the residual layer, could significantly influence the pollutant properties on the surface during early mornings. This study exhibits a continuous vertical picture of BC and its mixing state in urban areas, which would be helpful for understanding BC’s regional environmental effect.
How to cite: Liu, H., Pan, X., Sun, Y., and Wang, Z.: Vertical distribution of black carbon and its mixing state in urban boundary layer in summer, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6340, https://doi.org/10.5194/egusphere-egu23-6340, 2023.
Redox reactions transition metal ions (TMI), such as iron and copper, affect the concentrations of reactive oxygen species (ROS) in atmospheric cloud droplets and aqueous aerosol particles. Copper and iron have distinct emission sources resulting in only a small number fraction of cloud condensation nuclei and droplets that contain these metals. The fact that TMI reactions only occur in a small subset of particles and droplets is not taken into account in current multiphase chemistry models that are usually initialized with TMI concentrations derived from bulk sampling.
Our previous model studies have shown that model predictions based on bulk iron concentrations may significantly underestimate total OH and HO2 budgets if iron is assumed in all cloud (Ervens, 2022; Khaled et al., 2022). We extend this approach to copper reactions and to reactions between copper and iron ions. We use a multiphase chemistry box model to investigate the importance of the number fraction of TMI-containing particles and droplets and show under which atmospheric conditions detailed information on this parameter is most important. The aim of our study is to identify the impacts of the copper and iron distributions in cloud droplets and aqueous aerosol particles on the total gas and aqueous budgets of OH, HO2, H2O2 and O3 in the multiphase system. Our model results give guidance for measurement needs to further constrain the ROS budgets in the atmosphere.
How to cite: Aregahegn, K. and Ervens, B.: The impact of copper and iron distribution on reactive oxygen species concentrations in the atmospheric multiphase system, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6704, https://doi.org/10.5194/egusphere-egu23-6704, 2023.
Atmospheric aerosols affect the Earth’s radiative budget directly by scattering, reflecting, and absorbing light and also indirectly by acting as nuclei for the formation of liquid water and ice clouds. Many of these effects are directly related to the chemical and physical properties of the aerosol particles, e.g. their phase state, which is unknown for many atmospherically relevant compounds.
Glyoxal is one of the most abundant organic species in the atmosphere with a production rate of about 45 teragram per year.1 Despite being a simple gaseous dialdehyde in the absence of water, glyoxal exhibits a complex chemistry in aqueous solutions.2 Upon drying such solutions, glyoxal does not evaporate completely, but remains in the condensed phase due to the formation of water adducts and oligomeric species.3
In our work, we present differential scanning calorimetry (DSC) experiments on dried aerosolized as well as bulk aqueous glyoxal solutions. We studied the effect of the drying rate, of the concentration of the initial glyoxal solution, of temperature, and of the addition of atmospherically relevant ammonium salts on the glass transition temperature (Tg) of the glyoxal solutions. During fast and very slow drying, highly viscous or even glassy phase states were detected via DSC measurements, and we report the corresponding glass transition temperatures of such systems. After diluting the aqueous solutions with water, mimicking atmospheric water uptake in the atmosphere, Tg of the dried solution varies with time until a new chemical equilibrium is established. Considering their temperature dependence, the time scale of these processes can range from hours to days. We use the measured time-dependent glass transition temperatures to infer dependencies of the aqueous phase equilibria between monomer, dimer, and trimer glyoxal species and their water adducts and support these by infrared spectroscopy.4 We show that glass transition measurements can be used to infer information on the aqueous chemistry of organic molecules in solution in slowly equilibrating systems.
References:
(1) Fu, T.-M.; Jacob, D. J.; Wittrock, F.; Burrows, J. P.; Vrekoussis, M.; Henze, D. K. Global budgets of atmospheric glyoxal and methylglyoxal, and implications for formation of secondary organic aerosols. J. Geophys. Res. 2008, 113 (D15). DOI: 10.1029/2007JD009505.
(2) Ervens, B.; Volkamer, R. Glyoxal processing by aerosol multiphase chemistry: towards a kinetic modeling framework of secondary organic aerosol formation in aqueous particles. Atmos. Chem. Phys. 2010, 10 (17), 8219–8244. DOI: 10.5194/acp-10-8219-2010.
(3) Loeffler, K. W.; Koehler, C. A.; Paul, N. M.; De Haan, D. O. Oligomer formation in evaporating aqueous glyoxal and methyl glyoxal solutions. Environmental Science & Technology 2006, 40 (20), 6318–6323. DOI: 10.1021/es060810w.
(4) Peters, J.-H.; Dette, H. P.; Koop, T. Glyoxal as a Potential Source of Highly Viscous Aerosol Particles. ACS Earth Space Chem. 2021, 5 (12), 3324–3337. DOI: 10.1021/acsearthspacechem.1c00245.
How to cite: Peters, J.-H., Dette, H. P., and Koop, T.: Insights into Aqueous Glyoxal Chemistry via Glass Transition Measurements, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6917, https://doi.org/10.5194/egusphere-egu23-6917, 2023.
The particulate pollutants present in the atmosphere can have a negative impact on human health. Particulate matter consists of biological aerosols (pollen, viruses, etc.) as well as non-biological particles. Among the bioaerosols, research on pollen has been a hot topic in recent years. Pollen allergy is one of the typical clinical symptoms in Europe, with manifestations including but not limited to a runny nose and sneezing. Numerous figures show that the number of people suffering from pollen wind allergies in Europe is increasing year on year, with statistics showing that the prevalence of allergies is now up by 40%. For children, pollen allergies can further lead to serious illnesses such as asthma and eczema.
We are now working on time series pollen concentration forecasting and it is also the first real-time pollen concentration data table in England currently. Pollen concentration data is collected every five minutes. Seasonal variations in concentration as well as annual distribution curves have been plotted from this and correlation analysis has been carried out in conjunction with meteorological data to derive relationships between pollen concentrations and meteorological parameters. Accordingly, a suitable time frame will be selected, the data will be substituted into machine learning for training and accurate forecasting results will be produced.
How to cite: Chen, Z., Topping, D., and Crawford, I.: Accurate forecasting of pollen concentration in real time using machine learning, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6964, https://doi.org/10.5194/egusphere-egu23-6964, 2023.
The ubiquitous presence of organic aerosols (OA) and their dominant role in climate forcing via direct and indirect effects are increasingly recognized. Among the large spectrum of OAs, water-soluble secondary organic aerosols (SOA) have gained considerable scientific interest due to the in-cloud formation process and consequent climate effects. However, a lack of consensus on the molecular fingerprints and formation pathways of SOA limits our ability to assess their climate impact globally.
In this study, a detail investigation is made on water-soluble SOA components such as dicarboxylic acids, oxocarboxylic acids and dicarbonyls in springtime (March to May 2019) PM10 samples collected from a remote high-altitude site Lachung (27.4˚N and 88.4˚E, 2700 m a.s.l.) in the eastern Himalayas. The molecular fingerprints of water-soluble SOA components showed the predominance of oxalic acid (C2) followed by phthalic (Ph) and succinic acid. The diagnostic mass ratio of Ph to azelaic (C9) acid (2.1-7.7) indicated that anthropogenic emissions are the major sources of water-soluble OA at this remote high-altitude site. Moreover, SO42- dominates total water-soluble inorganic constituents and correlates significantly (R2 = 0.66) with the ISORROPIA-II model-derived aerosol liquid water content (LWC), indicating a crucial role of anthropogenic SO42- in controlling LWC of aerosols over the eastern Himalayas. Notably, we found significant positive relationships of C2 acid with both SO42- (R2 = 0.94) and aerosol LWC (R2 = 0.76), suggesting oxalic acid formation in LWC-enriched aerosols largely controlled by anthropogenic SO42- via aqueous phase photochemical processes. The increased formation of oxalic acid and related polar compounds with increasing SO42- is indicative of the fact that the reduction in anthropogenic emissions at the regional scale or source regions could control the water-soluble SOA loading in the atmosphere of the eastern Himalayas.
How to cite: Deshmukh, D. K., Hegde, P., Sujakumari, A. B., Gogoi, M. M., and Babu, S. S.: Anthropogenic sulfate-driven secondary organic aerosol formation over the eastern Himalayas through aqueous phase photochemical reactions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7274, https://doi.org/10.5194/egusphere-egu23-7274, 2023.
Knowledge of the glass transition temperature of molecular compounds in atmospheric aerosol particles is important for estimating their viscosity, which directly influences chemical reaction kinetics and phase state. While there is a great diversity of organic compounds present in aerosol particles, experimental glass transition temperatures are known of only a minor fraction of them. Therefore, we have developed a machine learning model in Python designed to predict the glass transition temperature of organic molecular compounds based on molecule-derived input variables. The extremely randomized trees (extra trees) procedure was chosen for this objective. Two approaches using different sets of input variables were followed. The first one uses the number of predefined functional groups present in the compound, while the second one generates descriptors from a SMILES (Simplified Molecular Input Line Entry System) string. For improved results both approaches can be combined with the melting temperature of the compound as an additional input variable, if known. The results show that the SMILES-based predictions had a slightly lower mean absolute error (MAE), but both approaches had a similar MAE of about 12-13 K. Furthermore, we also show that its performance exceeds that of previous parametrizations developed of this purpose and performs better than existing machine learning models. We believe that this model is a powerful tool for many applications in atmospheric aerosol science and material science.
How to cite: Armeli, G., Peters, J.-H., and Koop, T.: Glass Transition Temperature Prediction via Machine Learning, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7486, https://doi.org/10.5194/egusphere-egu23-7486, 2023.
Brown carbon (BrC) is the light-absorbing fraction of organic aerosols that can affect atmospheric photochemistry and influence regional and global climate. BrC can be emitted directly from incomplete combustion or formed through multiphase reactions. BrC consists of both water-soluble and methanol-soluble fractions (Me-BrC), with the Me-BrC fraction exhibiting greater absorption compared to the aqueous fraction owing to greater extraction potential. It is important to characterize the molecular composition of BrC to gain a better understanding of the link between BrC chromophores and their light absorption properties. In this study, proton nuclear magnetic resonance (1H NMR) and high-performance liquid chromatography (HPLC) coupled with a diode array detector (DAD) and a time-of-flight mass spectrometer (TOF-MS) with an electrospray ionisation (ESI) source are used to comment on the molecular composition of Me-BrC. For this purpose, daytime and nighttime PM2.5 samples collected from April 2019 to February 2020 in a rural area in the eastern Indo-Gangetic Plain (IGP) were used.
Both ESI- and ESI+ modes were utilized due to their respective affinity towards acidic and basic functional groups and about 500-2000 molecules were classified into four major compound classes: CHO, CHON, CHONS and CHOS. Among these, CHO- (25-32%) was the most abundant group followed by CHONS- (25-30%), CHON- (21-28%) and CHOS- (13-17%) in the negative mode whereas CHON+ (42-50%) showed the highest abundance in the positive mode followed by CHONS+ (30-38%) and CHO+ (6-14%) and CHOS+ (5-13%). 1H-NMR showed dominance of saturated oxygenated compounds (H-C-O) for all seasons, which is consistent with the high O/C ratio and OSc (oxidation state), with increasing Ar-H and hence double bond equipment (DBE) towards winter. Higher O/C (>0.3) and lower DBE of CHON+ and CHONS+ showed their significant contribution towards H-C-O type of BrC along with CHO-. CHON species can be formed by atmospheric reactions involving NOx (oxidised N-containing groups (O/C: 0.4, H/C: 1.5)) or NH3 (reduced N-containing groups (O/C: 0.2, H/C: 1.9)) with CHON- containing more organic nitrate moieties (−(O)NO2); (O/N >3)). Lower CHON towards the night time cross all seasons corresponds to the lower relative percentage of the H–C–C= type in NMR. High CHONS+ suggest presence of nitroxy organo-sulfate (formed via photooxidation of BVOCs under high NOx) or come from coal combustion. CHOS+ showed greater fraction of high‐molecular weight organosulfate compounds (low DBE or high H/C) which increased towards the winter. Also CHOS+ with high DBE (>4) with O/C (<0.4) suggests presence of reduced S‐containing compounds which are more likely to be originated from primary emissions. These findings provide the first insights into the chromophoric composition of the Indo-Gangetic Plain outflow.
How to cite: Rana, A. and Sarkar, S.: Molecular characterization of methanol-soluble BrC using 1H NMR fingerprinting and high-resolution mass spectrometry., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10478, https://doi.org/10.5194/egusphere-egu23-10478, 2023.
Indoor biofuel use for cooking/heating purposes is potentially a significant source of fine-mode aerosols in the Indian Himalayan region, with important implications for ambient atmospheric processes. Incomplete combustion of biofuels leads to emission of absorbing aerosols such as elemental carbon (EC), brown carbon (BrC) and humic-like substances (HULIS), which can affect climate via direct as well as indirect forcing. However, profiles of these aerosols in indoor microenvironments are poorly studied, especially from the Indian Himalayan region. Here, we report size-segregated light absorption properties (absorption coefficient; babs_aq) of aqueous brown carbon (BrCaq) for cow dung cake (CDC), firewood (WD), charcoal (CC), kerosene (KS) and liquified petroleum gas (LPG) combustion in indoor settings from two northwest Himalayan states (Uttarakhand and Himachal Pradesh). We further characterize BrC composition using excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis. Size-segregated samples (>2.5 µm, 2.5-1 µm, 1-0.5 µm, 0.5-0.25 µm and <0.25 µm) were collected during indoor cooking activities which showed PM levels exceeding Indian ambient PM2.5 standard by 8-460 times, with CDC showing the highest PM concentration in all size ranges. Size distribution profile of the fuels showed trimodal distributions with one peak in the Aitken nuclei mode (0.05 μm for CDC, WD and LPG; 0.06 μm for CC and KS) and the other two in the accumulation mode (0.22 and 2.03 μm for CDC, 0.21 μm and 2.1 μm for WD, 0.24 and 1.91 μm for KS, and 0.17 and 0.83 μm for CC). PM size distribution across kitchen and fuel types was characterized by more than 50% concentration in the Greenfield Gap region (0.1-2 μm)., CDC showed highest babs_365 for all size ranges combined (2245±357 Mm-1) compared to other fuels while LPG showed the lowest (190±46 Mm-1). BrCaq in the lowest size fraction showed greater babs compared to other size ranges in all fuels except KS. High values of babs ratio (>5) for300-400 nm (babs_300_400) to 400-500 nm (babs_400_500) wavelength range suggested the presence of HULIS in CDC and WD samples while other fuels exhibited values below 2.6. The lower size fractions (<0.5 µm) of CDC and WD were characterized by higher babs_300_400/babs_400_500 values (6.9±1.6 for CDC and 7.4±2.8 for WD) than upper size ranges (3.2±0.8 for CDC and 2.3±0.5 for WD), indicating a dominance of HULIS components in finer aerosol. Upon analysis of EEMs coupled with PARAGAC, three major chromophoric categories in BrCaq of CDC and WD samples were observed: two types of HULIS components with varying degree of conjugation and one type of protein-like substances (PRLIS). HULIS was the dominant chromophore type in lower size fractions (<0.5 µm) of CDC and WD samples (70±4% for CDC and 61±6% for WD) while for upper size fractions its contribution was relatively lower (50±10% for CDC and 36±9% for WD). Finally, BrCaq from CDC and WD emissions exhibited direct climate forcing potential equivalent to EC (relative radiative forcing (RRF): 91-98%), confirming that indoor biofuel emissions are indeed significant sources of climate forcing agents in the Indian Himalayan context.
How to cite: Rawat, P., Bau, S., and Sarkar, S.: Humic-like substances in residential biofuel use emissions from the northwestern Himalayan region, India, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10785, https://doi.org/10.5194/egusphere-egu23-10785, 2023.
Air pollution is typically at its lowest in Taiwan during summer. The mean concentrations of PM10, PM2.5, and daytime ozone (08:00–17:00 LST) during summer (June–August) over central Taiwan are 35–40 µg m-3, 18–22 µg m-3, and 30–42 ppb, respectively, between 2004 and 2019. Sampling analysis revealed that the contribution of organic carbon (OC) in PM2.5 could exceed 30% in urban and inland mountain sites during July in 2017 and 2018. Frequent episodes of air quality deterioration occur over the western plains of Taiwan when an easterly typhoon circulation interacts with the complex topographic structure of the island. We explored an episode of air quality deterioration that was associated with a typhoon between 15 and 17 July 2018, using the Weather Research Forecasting with Chemistry (WRF-Chem) model. The results indicated that the continual formation of low-pressure systems or typhoons in the area between Taiwan and Luzon island in the Philippines provided a strong easterly ambient flow, which lasted for an extended period between 15 and 17 July. The interaction between the easterly flow and Taiwan’s Central Mountain Range (CMR) resulted in stable weather conditions and weak wind speed in western Taiwan during the study period. Numerical modeling also indicated that a lee side vortex easily formation and the wind direction could be changed from southwesterly to northwesterly over central Taiwan because of the interaction between the typhoon circulation and the CMR. The northwesterly wind coupled with a sea breeze was conducive to the transport of air pollutants, from the coastal upstream industrial and urban areas to the inland area. The dynamic process for the wind direction changed given a reasonable explanation why the observed SO42- became the major contributor to PM2.5 during the episode. SO42- contribution proportions (%) to PM2.5 at the coastal, urban, and mountain sites were 9.4 µg m-3 (30.5%), 12.1 µg m-3 (29.9%), and 11.6 µg m-3 (29.7%), respectively. Moreover, the variation of the boundary layer height had a strong effect on the concentration level of both PM2.5 and ozone. The combination of the lee vortex and land-sea breeze, as well as the boundary layer development, were the key mechanisms in air pollutants accumulation and transport. As typhoons frequently occur around Taiwan during summer and fall, and their effect on the island’s air quality merits further research attention.
How to cite: Lin, C.-Y., Sheng, Y.-F., Chen, W.-C., Chou, C. C. K., Chien, Y.-Y., and Chen, W.-M.: Air quality deterioration episode associated with typhoon over the complex topographic environment in central Taiwan, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10987, https://doi.org/10.5194/egusphere-egu23-10987, 2023.
Heterogeneous processes such as aerosol-gas chemical reactions and vapour uptake are key to understanding the behaviour of aerosols in our environment. They contribute to their ability to take up water to form cloud droplets and determine the persistence of harmful particle-bound compounds, impacting the climate and human health.
Kinetic multi-layer models such as the kinetic multi-layer model for aerosol surface and bulk chemistry (KM-SUB) and gas-particle interactions (KM-GAP) are state-of-the-art models used to describe these processes on the particle and film level (Shiraiwa et al., 2010, 2012). KM-SUB and KM-GAP-based models have been used to determine the oxidative potential of particulate matter, the impact of surfactant self-organisation on aerosol chemical lifetimes, and the impact of aerosol phase state on the long-range transport of toxic chemicals. These models are useful but cumbersome to write and there is a need for an open-source tool to assist researchers in creating and optimising them.
We have developed MultilayerPy (Milsom et al., 2022), an open-source Python package which facilitates the creation and optimisation of kinetic multi-layer models. This software is written such that the user uses building blocks (i.e. reaction scheme, bulk diffusion parameterisations, and model components) to automatically generate model code which can then be ran and the output presented in a reproducible manner. This reduces the time needed to develop model descriptions of aerosol processes and allows the user to focus on the scientific issues rather than coding the models. I will present recent use cases of the software looking at the chemical lifetime of real aerosol material in the atmosphere, along with ongoing work extending the base package.
References:
Milsom, A., Lees, A., Squires, A. M. and Pfrang, C.: MultilayerPy (v1.0): a Python-based framework for building, running and optimising kinetic multi-layer models of aerosols and films, Geosci. Model Dev., 15(18), 7139–7151, doi:10.5194/gmd-15-7139-2022, 2022.
Shiraiwa, M., Pfrang, C. and Pöschl, U.: Kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB): The influence of interfacial transport and bulk diffusion on the oxidation of oleic acid by ozone, Atmos. Chem. Phys., 10, 3673–3691, doi:10.5194/acp-10-3673-2010, 2010.
Shiraiwa, M., Pfrang, C., Koop, T. and Pöschl, U.: Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP): Linking condensation, evaporation and chemical reactions of organics, oxidants and water, Atmos. Chem. Phys., 12(5), 2777–2794, doi:10.5194/acp-12-2777-2012, 2012.
How to cite: Milsom, A., Lees, A., Squires, A., and Pfrang, C.: MultilayerPy: a tool for creating and optimising multi-layer models of aerosol and film processes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13194, https://doi.org/10.5194/egusphere-egu23-13194, 2023.
Metal content in traffic emissions is often overlooked during regulation and policy making. Exhaust and non-exhaust traffic emissions, including tire, brake wear and re-suspended dust, contribute greatly to particulate matter and pose significant health effects to humans in urban areas (Johansson et al., 2009). The current lack of strict regulations on these metal emissions draws attention to the need for controls and monitoring, as reflected in the recent Euro 7 standards proposal for research on traffic emissions. This work aims to quantify metal emissions from traffic at an urban traffic site in Prague, Czech Republic, identify key tracers of emissions, and investigate exhaust and non-exhaust emissions observable in fine particulate matter (PM2.5). This project signifies the first high-time resolution metal analysis in Prague.
Two one-month long measurement campaigns were conducted from February to March and November to December 2020 at an urban traffic site in Prague. Elemental data were obtained from the Xact625i Ambient Metals Monitor (analytical method nondestructive energy dispersive X-ray fluorescence – EDXRF) equipped with a PM2.5 head at a two-hour time resolution. Enrichment factors were calculated, and correlations of key tracers (e.g. Cu, Ba, Zn, Mn) were identified. Source apportionment will be carried out using Positive Matrix Factorization (US EPA PMF 5.0) as well as a human risk assessment for potentially carcinogenic elements. Metallic elemental concentrations were observed in decreasing order: Fe > Zn > Cu > Ti > Mn > Ba > Cr > As > Cd > Ni. The most abundant metal, Fe, was found in the range of 10 – 2933 ng/m3, followed by Zn (1 – 144 ng/m3), Cu (1 – 104 ng/m3), Ba (0.1 – 41 ng/m3) and Cr (0.2 – 16 ng/m3). Enrichment factors of Cr, Mn, Cu and Zn were found to be up to 113, 71, 1937 and 1066, respectively.
Acknowledgement:
This conference contribution was supported by the Ministry of Education, Youth and Sports of the Czech Republic under grants ACTRIS-CZ LM2018122, ACTRIS-CZ RI (CZ.02.1 .01 / 0.0 / 0.0 / 16_013 / 0001315) and LTAUSA19006.
References:
JOHANSSON, C., NORMAN, M. & BURMAN, L. 2009. Road traffic emission factors for heavy metals. Atmospheric Environment - ATMOS ENVIRON, 43, 4681-4688.
How to cite: Windell, L., Pokorna, P., Ondracek, J., Schwarz, J., Lhotka, R., and Zdimal, V.: Elemental characterization of PM2.5 at an urban traffic site in Central Europe, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15074, https://doi.org/10.5194/egusphere-egu23-15074, 2023.
Filter Inlet for Gases and Aerosols (FIGAERO) inlet coupled with Time-of-Flight Chemical Ionization Mass Spectrometers (ToF-CIMS) have been successfully employed in numerous studies during past years (Thornton et. al., 2020). The instrument can be used to study both gas-phase and particle-phase chemical compounds over a broad range of chemical functionalities. The inbuilt controlled thermal desorption mechanism also allows for the investigation of volatility of the compounds present in the particle phase. Such a particle volatility measurement using FIGAERO-ToF-CIMS relies on accurate identification of the Tmax for individual compounds, i.e. the temperatures at which highest respective signals are observed. These Tmax values can be converted to saturation vapor pressure Psat and saturation mass concentration C* values with a reliable calibration (Ylisirniö et. al., 2021).
However, due to a lack of calibration compounds with known Psat at the low end of the volatility range (Psat <10-9 (Pa) / C* < -10-4 (μg/m3)), the current calibration procedure can only cover the desorption temperature range up to ~80-100 ˚C, while desorption temperatures of FIGAERO-ToF-CIMS can reach 200 ˚C and Tmax values are routinely identified up to 160 ˚C. In this study we aim to extend the FIGAERO-ToF-CIMS calibration values to cover lower Psatvalues by utilizing a range of different approaches to increase the accuracy of the volatility measurement.
Methods
Tmax values of Polyethylene Glycols (PEG’s) from PEG 5 to 15 were measured with FIGAERO-CIMS and corresponding C* values were either measured (for PEG 5-9) with isothermal evaporation experiments or estimated (PEG 5-15) with several different methods. Used estimation methods were quantum chemical modelling (COSMOtherm), desorption modelling (Schobesberger et. al., 2018), and parametrizations including Modified Grain Model, EVAPORATION, SIMPOL, and by Li et. al., 2016, Stolzenburg et. al., 2018 and Mohr et. al., 2019. Additionally, a parametrization equation according to Li et. al. 2016 was fitted to PEG 4-9 literature data and C* values of PEG 10-15 were estimated with this fit.
Results
Figure 1 shows the measured and estimated C*(298 K) values as function of the measured Tmaxvalues. The spread of results with different models is increasingly larger especially at the higher order PEG’s, with over 10 orders of magnitude difference between models. Two independent measurement methods agree with each other within one order of magnitude. Best agreement with measurements is with desorption model, Modified Grain Model and COSMOTherm.
Figure 1. Tmax vs. C*. Results from different measurements or estimates are shown in the figure legend. Note that some markers are very close to each other.
This work was supported by Academy of Finland Flagship funding (grant no. 337550)
Li et. al., 2016, Atmos. Chem. Phys., 16, 3327-3344.
Krieger et. al., 2018, Atmos. Meas. Tech., 11(1), 49–63.
Mohr et. al., 2019, Nat. Comm. 10, Article number: 4442.
Schobesberger et. al., 2018, Atmos. Chem. Phys., 18(20), 14757–14785.
Stolzenburg et. al., 2018, PNAS, 115 (37) 9122-9127.
Thornton et. al., 2020, Acc. Chem. Res., 53(8), 1415–1426.
Ylisirniö et. al., 2021, Atmos. Meas. Tech., 14(1), 355–367.
How to cite: Ylisirniö, A., Hyttinen, N., Li, Z., Alton, M., Pullinen, I., Yli-Juuti, T., and Schobesberger, S.: Expanding volatility calibration range of FIGAERO-ToF-CIMS, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15685, https://doi.org/10.5194/egusphere-egu23-15685, 2023.
Recent studies have suggested that injection of solid particles such as alumina (Al2O3) and calcite (CaCO3) instead of SO2 for stratospheric aerosol intervention could reduce some of the adverse side effects of SAI such as ozone depletion, stratospheric heating, and changes in diffuse radiation. However, the expected improvements from alteration of stratospheric chemistry are subject to large uncertainties. We constrain some of these uncertainties by experimental work on calcite particles using elastic recoil detection analysis (ERDA) and in-situ experiments using X-ray photoelectron spectroscopy (XPS). Subsequently, we use a global aerosol-chemistry climate model that, for the first time, interactively couples microphysical and chemical processes of solid calcite and alumina particles as well as liquid sulfuric acid aerosols with model radiation and transport. Notably, SAI by solid particles only leads to more effective radiative forcing per aerosol burden compared to sulfuric acid aerosols, not per injected mass. However, reduced stratospheric warming remains a major advantage of solid particles. Furthermore, different assumptions on the heterogeneous chemistry of solid particles, based on the available experimental data, result in drastically different impacts on stratospheric composition, in particular, ozone. For alumina particles, which are thought to not undergo chemical aging during their stratospheric residence time we present a sensitivity analysis for heterogenous reactions to quantify uncertainty. For the alkaline calcite particles, which are thought to undergo chemical aging in the stratosphere via reaction with acids (e.g., HCl, HNO3, H2SO4) we find even larger uncertainties due to unknown reaction pathways and highly uncertain rates under stratospheric conditions. The large uncertainty in predicted stratospheric ozone changes can only be reduced via substantial additional laboratory experiments under stratospheric conditions, i.e., partial pressures of relevant gases (e.g., HCl, HNO3, H2SO4), temperatures < 220 K, relative humidity < 1% and realistic UV irradiance. From the present perspective, sulfur-based SAI has significantly lower uncertainty than injection of solid particles, which have significantly reduced stratospheric heating but very large uncertainties in impacts on stratospheric composition.
How to cite: Vattioni, S., Weber, R., Klaus, O., Luo, B., Dykema, J., Stenke, A., Feinberg, A., Döbeli, M., Vockenhuber, C., Kreiger, U., Weers, U., Artiglia, L., Yang, H., Longetti, L., Gabathuler, J., Ammann, M., Keutsch, F., Peter, T., and Chiodo, G.: Risks and benefits of stratospheric solid particle injection for climate intervention, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15897, https://doi.org/10.5194/egusphere-egu23-15897, 2023.
Biological aerosols mainly include viruses, bacteria, fungal and pollen, which can significantly affect the human health and environments. Accurate classification of biological aerosols contributes to further understand the implications of these aerosols in different domains. In this work, we collected the real-time fluorescence intensity, size and scattering images data of bioaerosols over a six-month period in Hong Kong by using Rapid-E particle identifier. To clustering the different types of bioaerosols, two deep leaning methods: autoencoder neural network (AE) and bidirectional long short-term memory neural network (Bilstms) were designed to extract the main features of bioaerosol fluorescence intensity and scattering images. The results showed that both AE and Bilstms could reconstruct the input bioaerosol data quite well, which illustrated that the main features they exacted were accurate. Then two clustering methods: K-means, and genie clustering were used to assign the extracted main features of bioaerosol into different clusters respectively. According to the aerosol number distribution in different clusters, the K-means clustering always presented a more uniform aerosol number distribution than genie clustering, especially for bioaerosol features extracted by Bilstms, genie believed that no matter how the number of clusters and the type of bioaerosol data changed, most aerosols were only distributed in one or two clusters. In order to assess the accuracy of clustering and obtain the species of bioaerosol in different clusters, different clusters were identified by analyzing their diurnal variation, average scattering images pattern and the relationship to the meteorological variables temperature, relative humidity, wind speed and wind direction. Based on the identification results, the accuracy of different combinations of two deep learning methods and two clustering methods in bioaerosol classification was evaluated. We believed that this work could provide the potential aid in aerosol classification methods development to achieve the easy and accurate bioaerosol identification.
How to cite: Zhang, H., Topping, D., Crawford, I., Gallagher, M., Chan, M. N., Lee, H. B. M., Xing, S., Ng, T. H., and Tai, A.: Deep learning based classification of biological aerosols, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6415, https://doi.org/10.5194/egusphere-egu23-6415, 2023.
A field campaign, AERONET DRAGON J-ALPS (joint research on aerosol process studies), is planned to is planned to study the influence of mountain topography on aerosol transport, the aerosol life cycle, and aerosol properties in a narrow valley. DRAGON/J-ALPS was planned to start in March 2020, with 12 AERONET Cimel sun/sky radiometers deployed in the central valley surrounded by the Japanese Alps. Some instruments were also placed in the mountains to study aerosols transported through the higher layers. In April 2020, however, observations were discontinued due to the COVID-V2; they resumed in the fall of 2020 and were extended until the spring of 2021. Some sites also operated until fall 2021.
The initial results of DRAGON/J-ALPS are presented in terms of aerosol characteristics from ground and satellite observations, with particular focus on regional background aerosols and long-range transboundary aerosols (biomass burning smoke, Asian dust, and volcanic smoke) across the Japanese Alps. Results of regional model simulations will also be presented.
How to cite: Sano, I., Mukai, S., Makiko, N., Holben, B., and Maki, T.: DRAGON J-ALPS: study of aerosol properties in Japanese Alps and valley region, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16364, https://doi.org/10.5194/egusphere-egu23-16364, 2023.
Posters virtual: Tue, 25 Apr, 08:30–10:15 | vHall AS
Mongolia experiences frequent dust and sand storms, particularly in the spring. As a result, this country losses a huge amount of top soils, which triggers land degradation and desertification. We measured sand flux of 2 consecutive dust storm cases occured in 2011 using BSNE (Big Spring Number Eight) sand traps installed at the Bulgan meteorological station in the Gobi area .
Vertical gradients for the sand mass (flux) demonstrated 3 typical patterns:
- a) sand flux increases with height when there is a transported sand from the areas distanced away from the study site
- b) sand flux is constant vertically in the days following dust sand storm (DSS)
- c) sand flux declines exponentially with the height when DSS occur at the site.
Among these three typical patterns, we investigated the c) pattern to quantify the amount of eroded soil during the on-site dust emissions of dust storm event (DSS) at the site. The DSS was largely associated with the increased friction velocity excluding some cases those are related to a short time-span of rainfall even though underlain by dry soil surface etc. Furthermore, we estimated a saltation height, Zq, which was much greater (30 cm) than the other reported findings (3-10 cm).
Keywords: sand flux patterns, saltation height, sand traps, Mongolia
How to cite: Munkhtsetseg, E., Shinoda, M., Gillies, J., and Shao, Y.: Sand flux in a desert site of Mongolia, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3886, https://doi.org/10.5194/egusphere-egu23-3886, 2023.
Nitrous acid (HONO) is an important component of the nitrogen cycle in the atmosphere. Photolysis of HONO generates hydroxyl (OH) radicals and significantly influences the atmospheric oxidative capacity. Early laboratory work discovered that soil nitrite, produced via biological nitrification or denitrification, can be an important HONO source. However, the laboratory-determined chamber HONO fluxes can largely deviate from those in the real world for the same soil sample. Therefore, quantification of soil fluxes of HONO in the atmosphere remains challenging. [HONO]*, the equilibrium gas-phase concentration over the aqueous solution of nitrous acid in the soil, has been suggested as a key parameter for quantifying soil fluxes of HONO; but it has not yet been well-validated and quantified. In this project, we present a method to retrieve [HONO]* by conducting controlled dynamic chamber experiments with soil samples and validate the existence of [HONO]* over the soil. We show that [HONO]* is a soil characteristic, independent of HONO concentrations in the chamber. Therefore, it is reliable to use [HONO]* to quantify soil fluxes of HONO. [HONO]* performs as an indicator of the potential of soil to be a source or a sink for atmospheric HONO and helps to better quantify the role of HONO fluxes of soil in the HONO budget and its implications on the oxidizing capacity in the atmosphere.
How to cite: Bao, F., Cheng, Y., Kuhn, U., Li, G., Wang, W., Kratz, A., Weber, J., Weber, B., Pöschl, U., and Su, H.: Key Role of Equilibrium HONO Concentration over Soil in Quantifying Soil-Atmosphere HONO Fluxes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14862, https://doi.org/10.5194/egusphere-egu23-14862, 2023.
The refractive index (RI) of aerosol is an important parameter that reflects the scattering and absorption capacity of aerosol and is widely used in atmospheric models and remote sensing studies. It depends on several properties such as chemical species, moisture content, etc. RI is usually obtained by the chemical method using a volume mixing ratio of known chemicals and by the optical method based on extinction, scattering and/or absorption coefficient using Mie theory. However, these methods are complicated and are mainly for singular particles. In this study, we tried to make a simple method to estimate RI by measuring the extinction coefficient from camera images and size distribution from the optical particle counter (OPC). We used the wavelength of Red-Green-Blue color as 597, 534, and 459 nm to calculate the extinction coefficient and the number size distribution to retrieve the volume size distribution obtained by OPC. The volume size distribution is expressed by six parameters of two gaussian graphs for fine and coarse-mode particles. We got the volume, median radius, and standard deviation of fine and coarse aerosol peaks. The measurement site was the port area in Busan, Korea. We sometimes discovered the emission of particles but mainly measured for clear days. We effectively retrieved six parameters determining the volume size distribution of ambient aerosols and tried to inverse RI as total, fine, and coarse particles using the nonlinear optimization method. We mainly considered the scattering effects of ambient aerosols, so we focused on the real part of RI. The retrieved RI was from 1.27 to 1.50 and showed different values on fine- and coarse-mode size particles. The results were lower than other RI measurement studies, so we need to validate more. However, we identified the possibility of retrieving the RI of aerosols using the known size distribution retrieved from OPC and the three-color extinctions from the camera.
How to cite: Shin, J., Sim, J., Kim, D., and Noh, Y.: Estimation on the refractive index of ambient aerosols as fine- and coarse-mode volume size distribution, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4572, https://doi.org/10.5194/egusphere-egu23-4572, 2023.
