SwePub - search: WFRF:(Schobesberger Siegfried)

Enumeration	Reference	Cover	Find
1.	Almeida, Joao, et al. (author) Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere 2013 In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 502:7471, s. 359- Journal article (peer-reviewed)abstract Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes(2). Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases(2). However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere(3). It is thought that amines may enhance nucleation(4-16), but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.
2.	Buchholz, Angela, et al. (author) Deconvolution of FIGAERO-CIMS thermal desorption profiles using positive matrix factorisation to identify chemical and physical processes during particle evaporation 2020 In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:13, s. 7693-7716 Journal article (peer-reviewed)abstract The measurements of aerosol particles with a filter inlet for gases and aerosols (FIGAERO) together with a chemical ionisation mass spectrometer (CIMS) yield the overall chemical composition of the particle phase. In addition, the thermal desorption profiles obtained for each detected ion composition contain information about the volatility of the detected compounds, which is an important property for understanding many physical properties like gas-particle partitioning. We coupled this thermal desorption method with isothermal evaporation prior to the sample collection to investigate the chemical composition changes during isothermal particle evaporation and particulate-water-driven chemical reactions in alpha-pinene secondary organic aerosol (SOA) of three different oxidative states. The thermal desorption profiles of all detected elemental compositions were then analysed with positive matrix factorisation (PMF) to identify the drivers of the chemical composition changes observed during isothermal evaporation. The keys to this analysis were to use the error matrix as a tool to weight the parts of the data carrying most information (i.e. the peak area of each thermogram) and to run PMF on a combined data set of multiple thermograms from different experiments to enable a direct comparison of the individual factors between separate measurements. The PMF was able to identify instrument background factors and separate them from the part of the data containing particle desorption information. Additionally, PMF allowed us to separate the direct desorption of compounds detected at a specific elemental composition from other signals with the same composition that stem from the thermal decomposition of thermally instable compounds with lower volatility. For each SOA type, 7-9 factors were needed to explain the observed thermogram behaviour. The contribution of the factors depended on the prior isothermal evaporation. Decreased contributions from the factors with the lowest desorption temperatures were observed with increasing isothermal evaporation time. Thus, the factors identified by PMF could be interpreted as volatility classes. The composition changes in the particles due to isothermal evaporation could be attributed to the removal of volatile factors with very little change in the desorption profiles of the individual factors (i.e. in the respective temperatures of peak desorption, T-max). When aqueous-phase reactions took place, PMF was able to identify a new factor that directly identified the ions affected by the chemical processes. We conducted a PMF analysis of the FIGAERO-CIMS thermal desorption data for the first time using laboratory-generated SOA particles. But this method can be applied to, for example, ambient FIGAERO-CIMS measurements as well. There, the PMF analysis of the thermal desorption data identifies organic aerosol (OA) sources (such as biomass burning or oxidation of different precursors) and types, e.g. hydrocarbon-like (HOA) or oxygenated organic aerosol (OOA). This information could also be obtained with the traditional approach, namely the PMF analysis of the mass spectra data integrated for each thermogram. But only our method can also obtain the volatility information for each OA source and type. Additionally, we can identify the contribution of thermal decomposition to the overall signal.
3.	Buchholz, Angela, et al. (author) Insights into the O : C-dependent mechanisms controlling the evaporation of alpha-pinene secondary organic aerosol particles 2019 In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:6, s. 4061-4073 Journal article (peer-reviewed)abstract The volatility of oxidation products of volatile organic compounds (VOCs) in the atmosphere is a key factor to determine if they partition into the particle phase contributing to secondary organic aerosol (SOA) mass. Thus, linking volatility and measured particle composition will provide insights into SOA formation and its fate in the atmosphere. We produced alpha-pinene SOA with three different oxidation levels (characterized by average oxygen-to-carbon ratio; (O:C) over bar = 0.53, 0.69, and 0.96) in an oxidation flow reactor. We investigated the particle volatility by isothermal evaporation in clean air as a function of relative humidity (RH < 2 %, 40 %, and 80 %) and used a filter-based thermal desorption method to gain volatility and chemical composition information. We observed reduced particle evaporation for particles with increasing <(O:C )over bar> ratio, indicating that particles become more resilient to evaporation with oxidative aging. Particle evaporation was increased in the presence of water vapour and presumably particulate water; at the same time the resistance of the residual particles to thermal desorption was increased as well. For SOA with (O:C ) over bar = 0.96, the unexpectedly large increase in mean thermal desorption temperature and changes in the thermogram shapes under wet conditions (80 % RH) were an indication of aqueous phase chemistry. For the lower (O:C ) over bar cases, some water-induced composition changes were observed. However, the enhanced evaporation under wet conditions could be explained by the reduction in particle viscosity from the semi-solid to liquid-like range, and the observed higher desorption temperature of the residual particles is a direct consequence of the increased removal of high-volatility and the continued presence of low-volatility compounds.
4.	D'Ambro, Emma L., et al. (author) Isothermal Evaporation of alpha-Pinene Ozonolysis SOA : Volatility, Phase State, and Oligomeric Composition 2018 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 2:10, s. 1058-1067 Journal article (peer-reviewed)abstract We present measurements of the isothermal evaporation of alpha-pinee ozonolysis secondary organic aerosol (SOA). Using a novel, filter-based method, we reproduce literature observations of the time-dependent evaporation of SOA particles. We apply two detailed physical models to interpret the evaporative behavior of both the bulk SOA and individual components. Both models find that a combination of effectively nonvolatile products, together with reversibly formed oligomers (or otherwise reactive monomers) having a decomposition lifetime of 9 to 28 h, best explains the evolution of composition and volatility as particles age in the absence of both organic vapors and oxidants, even under an assumption of relatively viscous (soft wax-like with a minimum diffusion coefficient of 1 x 10(-5) cm(2) s(-1)) particles. We find that the residence time in the SOA formation chamber and time spent undergoing isothermal evaporation, both indicative of the physical age of the aerosol, are the most important experimental parameters determining the evaporation rate. The evolution of volatility observed in these experiments is compared to field measurements in a boreal forest site. The ambient monoterpene-dominated SOA volatility is only reproduced in the laboratory after 24 h of extended aging in a dilute, dark, oxidant-free environment.
5.	Donahue, Neil M., et al. (author) How do organic vapors contribute to new-particle formation? 2013 In: Faraday discussions. - : Royal Society of Chemistry. - 1359-6640 .- 1364-5498. ; 165, s. 91-104 Journal article (peer-reviewed)abstract Highly oxidised organic vapors can effectively stabilize sulphuric acid in heteronuclear clusters and drive new-particle formation. We present quantum chemical calculations of cluster stability, showing that multifunctional species can stabilize sulphuric acid and also present additional polar functional groups for subsequent cluster growth. We also model the multi-generation oxidation of vapors associated with secondary organic aerosol formation using a two-dimensional volatility basis set. The steady-state saturation ratios and absolute concentrations of extremely low volatility products are sufficient to drive new-particle formation with sulphuric acid at atmospherically relevant rates.
6.	Huang, Wei, et al. (author) Variation in chemical composition and volatility of oxygenated organic aerosol in different rural, urban, and mountain environments 2024 In: Atmospheric Chemistry and Physics. - 1680-7316 .- 1680-7324. ; 24:4, s. 2607-2624 Journal article (peer-reviewed)abstract The apparent volatility of atmospheric organic aerosol (OA) particles is determined by their chemical composition and environmental conditions (e.g., ambient temperature). A quantitative, experimental assessment of volatility and the respective importance of these two factors remains challenging, especially in ambient measurements. We present molecular composition and volatility of oxygenated OA (OOA) particles in different rural, urban, and mountain environments (including Chacaltaya, Bolivia; Alabama, US; Hyytiälä, Finland; Stuttgart and Karlsruhe, Germany; and Delhi, India) based on deployments of a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-CIMS). We find on average larger carbon numbers (nC) and lower oxygen-To-carbon (O:C) ratios at the urban sites (nC: 9.8±0.7; O:C: 0.76±0.03; average ±1 standard deviation) compared to the rural (nC: 8.8±0.6; O:C: 0.80±0.05) and mountain stations (nC: 8.1±0.8; O:C: 0.91±0.07), indicative of different emission sources and chemistry. Compounds containing only carbon, hydrogen, and oxygen atoms (CHO) contribute the most to the total OOA mass at the rural sites (79.9±5.2%), in accordance with their proximity to forested areas (66.2±5.5% at the mountain sites and 72.6±4.3% at the urban sites). The largest contribution of nitrogen-containing compounds (CHON) is found at the urban stations (27.1±4.3%), consistent with their higher NOx levels. Moreover, we parametrize OOA volatility (saturation mass concentrations, Csat) using molecular composition information and compare it with the bulk apparent volatility derived from thermal desorption of the OOA particles within the FIGAERO. We find differences in Csat values of up to 1/43 orders of magnitude and variation in thermal desorption profiles (thermograms) across different locations and systems. From our study, we draw the general conclusion that environmental conditions (e.g., ambient temperature) do not directly affect OOA apparent volatility but rather indirectly by influencing the sources and chemistry of the environment and thus the chemical composition. The comprehensive dataset provides results that show the complex thermodynamics and chemistry of OOA and their changes during its lifetime in the atmosphere. We conclude that generally the chemical description of OOA suffices to predict its apparent volatility, at least qualitatively. Our study thus provides new insights that will help guide choices of, e.g., descriptions of OOA volatility in different model frameworks such as air quality models and cloud parcel models.
7.	Kirkby, Jasper, et al. (author) Ion-induced nucleation of pure biogenic particles 2016 In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 521-526 Journal article (peer-reviewed)abstract Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood(1). Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours(2). It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere(3,4), and that ions have a relatively minor role(5). Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded(6,7). Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of a-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.
8.	Kulmala, Markku, et al. (author) Direct Observations of Atmospheric Aerosol Nucleation 2013 In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 339:6122, s. 943-946 Journal article (peer-reviewed)abstract Atmospheric nucleation is the dominant source of aerosol particles in the global atmosphere and an important player in aerosol climatic effects. The key steps of this process occur in the sub-2-nanometer (nm) size range, in which direct size-segregated observations have not been possible until very recently. Here, we present detailed observations of atmospheric nanoparticles and clusters down to 1-nm mobility diameter. We identified three separate size regimes below 2-nm diameter that build up a physically, chemically, and dynamically consistent framework on atmospheric nucleation-more specifically, aerosol formation via neutral pathways. Our findings emphasize the important role of organic compounds in atmospheric aerosol formation, subsequent aerosol growth, radiative forcing and associated feedbacks between biogenic emissions, clouds, and climate.
9.	Lampilahti, Janne, et al. (author) Zeppelin-led study on the onset of new particle formation in the planetary boundary layer 2021 In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:16, s. 12649-12663 Journal article (peer-reviewed)abstract We compared observations of aerosol particle formation and growth in different parts of the planetary boundary layer at two different environments that have frequent new particle formation (NPF) events. In summer 2012 we had a campaign in Po Valley, Italy (urban background), and in spring 2013 a similar campaign took place in Hyytiälä, Finland (rural background). Our study consists of three case studies of airborne and ground-based measurements of ion and particle size distribution from ∼1 nm. The airborne measurements were performed using a Zeppelin inside the boundary layer up to 1000 m altitude. Our observations show the onset of regional NPF and the subsequent growth of the aerosol particles happening almost uniformly inside the mixed layer (ML) in both locations. However, in Hyytiälä we noticed local enhancement in the intensity of NPF caused by mesoscale boundary layer (BL) dynamics. Additionally, our observations indicate that in Hyytiälä NPF was probably also taking place above the ML. In Po Valley we observed NPF that was limited to a specific air mass.
10.	Lawler, Michael J., et al. (author) Unexpectedly acidic nanoparticles formed in dimethylamine-ammonia-sulfuric-acid nucleation experiments at CLOUD 2016 In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:21, s. 13601-13618 Journal article (peer-reviewed)abstract New particle formation driven by acid-base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10-30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models, which predict a higher dimethylaminium fraction when NH3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : acid ratios lower than 1 : 1. The lowest base fractions were found in particles below 15 nm VMD, with a strong size-dependent composition gradient. The reasons for the very acidic composition remain uncertain, but a plausible explanation is that the particles did not reach thermodynamic equilibrium with respect to the bases due to rapid heterogeneous conversion of SO2 to sulfate. These results indicate that sulfuric acid does not require stabilization by ammonium or dimethylaminium as acid-base pairs in particles as small as 10 nm.
11.	Lee, Ben H, et al. (author) Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets. 2016 In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 113:6, s. 1516-21 Journal article (peer-reviewed)abstract Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gas-particle equilibrium and (ii) have a short particle-phase lifetime (∼2-4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment.
12.	Lehtipalo, Katrianne, et al. (author) How Do Amines Affect the Growth of Recently Formed Aerosol Particles 2013 In: NUCLEATION AND ATMOSPHERIC AEROSOLS. - : American Institute of Physics (AIP). - 9780735411524 ; , s. 295-297 Conference paper (peer-reviewed)abstract Growth rates of recently born nanometer-scale particles were measured during the CLOUD experiments at CERN. Combining the data from several recently developed measurement techniques allowed us to follow the growth of the particles starting from molecules to molecular clusters and finally to climatically relevant particles. We studied the binary system with sulphuric acid and water, and the ternary systems with ammonia or dimethylamine added to the chamber, both in purely neutral situation, and with ionization from cosmic rays or the CERN particle beam.
13.	Lehtipalo, Katrianne, et al. (author) The effect of acid-base clustering and ions on the growth of atmospheric nano-particles 2016 In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7 Journal article (peer-reviewed)abstract The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.
14.	Merikanto, Joonas, et al. (author) Effect of ions on sulfuric acid-water binary particle formation : 1. Theory for kinetic- and nucleation-type particle formation and atmospheric implications 2016 In: Journal of Geophysical Research-Atmospheres. - : American Geophysical Union (AGU). - 2169-897X. ; 121:4, s. 1736-1751 Journal article (peer-reviewed)
15.	Schobesberger, Siegfried, et al. (author) A model framework to retrieve thermodynamic and kinetic properties of organic aerosol from composition-resolved thermal desorption measurements 2018 In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:20, s. 14757-14785 Journal article (peer-reviewed)abstract Chemical ionization mass spectrometer (CIMS) techniques have been developed that allow for quantitative and composition-resolved measurements of organic compounds as they desorb from secondary organic aerosol (SOA) particles, in particular during their heat-induced evaporation. One such technique employs the Filter Inlet for Gases and AEROsol (FIGAERO). Here, we present a newly developed model framework with the main aim of reproducing FIGAERO-CIMS thermograms: signal vs. ramped desorption temperature. The model simulates the desorption of organic compounds during controlled heating of filter-sampled SOA particles, plus the subsequent transport of these compounds through the FIGAERO manifold into an iodide-CIMS. Desorption is described by a modified Hertz-Knudsen equation and controlled chiefly by the temperature-dependent saturation concentration C, mass accommodation (evaporation) coefficient, and particle surface area. Subsequent transport is governed by interactions with filter and manifold surfaces. Reversible accretion reactions (oligomer formation and decomposition) and thermal decomposition are formally described following the Arrhenius relation. We use calibration experiments to tune instrument-specific parameters and then apply the model to a test case: measurements of SOA generated from dark ozonolysis of alpha-pinene. We then discuss the ability of the model to describe thermograms from simple calibration experiments and from complex SOA, and the associated implications for the chemical and physical properties of the SOA. For major individual compositions observed in our SOA test case (#C = 8 to 10), the thermogram peaks can typically be described by assigning C(25 degrees C) values in the range 0.05 to 5 mu g m(-3), leaving the larger, high-temperature fractions (> 50 %) of the thermograms to be described by thermal decomposition, with dissociation rates on the order of similar to 1 h 1 at 25 degrees C. We conclude with specific experimental designs to better constrain instrumental model parameters and to aid in resolving remaining ambiguities in the interpretation of more complex SOA thermogram behaviors. The model allows retrieval of quantitative volatility and mass transport information from FIGAERO thermograms, and for examining the effects of various environmental or chemical conditions on such properties.
16.	Schobesberger, Siegfried, et al. (author) Airborne measurements over the boreal forest of southern Finland during new particle formation events in 2009 and 2010 2013 In: Boreal environment research. - 1239-6095 .- 1797-2469. ; 18:2, s. 145-163 Journal article (peer-reviewed)abstract Schobesberger, S., Vaananen, R., Leino, K., Virkkula, A., Backman, J., Pohja, T., Siivola, E., Franchin, A., Mikkila, J., Paramonov, M., Aalto, P.P., Krejci, R., Petaja, T. & Kulmala, M. 2013: Airborne measurements over the boreal forest of southern Finland during new particle formation events in 2009 and 2010. Boreal Env. Res. 18: 145-163. We conducted airborne observations of aerosol physical properties over the southern Finland boreal forest environment. The aim was to investigate the lower tropospheric aerosol (up to 4-km altitude) over an area of 250 by 200 km, in particular during new particle formation (NPF) events, and to address the spatial variability of aerosol number concentration and number size distribution. The regional NPF events, detected both airborne and at the ground, with air masses originating from the Arctic or northern Atlantic Ocean were studied throughout the boundary layer and throughout the area covered. Three suitable case studies are presented in more detail. In two of these studies, the concentrations of nucleation mode particles (3-10 nm in diameter) were found considerably higher (up to a factor of 30) in the upper parts of the planetary boundary layer compared to ground-based measurements during the nucleation events. The observed vertical variation can be connected to boundary layer dynamics and interactions between the boundary layer and the lower free troposphere, likely yielding high concentrations of newly formed aerosol particles. Our results suggest that nucleation does not necessarily occur close to the surface. In one presented case we found evidence of NPF occurring in a limited area above cloud, in the complete absence of a regional NPF event.
17.	Thornton, Joel A., et al. (author) Evaluating Organic Aerosol Sources and Evolution with a Combined Molecular Composition and Volatility Framework Using the Filter Inlet for Gases and Aerosols (FIGAERO) 2020 In: Accounts of Chemical Research. - : American Chemical Society (ACS). - 0001-4842 .- 1520-4898. ; 53:8, s. 1415-1426 Research review (peer-reviewed)abstract The complex array of sources and transformations of organic carbonaceous material that comprises an important fraction of atmospheric fine particle mass, known as organic aerosol, has presented a long running challenge for accurate predictions of its abundance, distribution, and sensitivity to anthropogenic activities. Uncertainties about changes in atmospheric aerosol particle sources and abundance over time translate to uncertainties in their impact on Earth's climate and their response to changes in air quality policy. One limitation in our understanding of organic aerosol has been a lack of comprehensive measurements of its molecular composition and volatility, which can elucidate sources and processes affecting its abundance. Herein we describe advances in the development and application of the Filter Inlet for Gases and Aerosols (FIGAERO) coupled to field-deployable High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometers (HRToF-CIMS). The FIGAERO HRToFCIMS combination broadly probes gas and particulate OA molecular composition by using programmed thermal desorption of particles collected on a Teflon filter with subsequent detection and speciation of desorbed vapors using inherently quantitative selected-ion chemical ionization. The thermal desorption provides a means to obtain quantitative insights into the volatility of particle components and thus the physicochemical nature of the organic material that will govern its evolution in the atmosphere. In this Account, we discuss the design and operation of the FIGAERO, when coupled to the HRToF-CIMS, for quantitative characterization of the molecular-level composition and effective volatility of organic aerosol in the laboratory and field. We provide example insights gleaned from its deployment, which improve our understanding of organic aerosol sources and evolution. Specifically, we connect thermal desorption profiles to the effective equilibrium saturation vapor concentration and enthalpy of vaporization of detected components. We also show how application of the FIGAERO HRToF-CIMS to environmental simulation chamber experiments and the field provide new insights and constraints on the chemical mechanisms governing secondary organic aerosol formation and dynamic evolution. We discuss the associated challenges of thermal decomposition during desorption and calibration of both the volatility axis and signal. We also illustrate how the FIGAERO HRToF-CIMS can provide additional insights into organic aerosol through isothermal evaporation experiments as well as for detection of ultrafine particulate composition. We conclude with a description of future opportunities and needs for its ability to further organic aerosol science.
18.	Tröstl, Jasmin, et al. (author) The role of low-volatility organic compounds in initial particle growth in the atmosphere 2016 In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 527-531 Journal article (peer-reviewed)abstract About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday(1). Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres(2,3). In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles(4), thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth(5,6), leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer(7-10). Although recent studies(11-13) predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon(2), and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Kohler theory)(2,14), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown(15) that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
19.	Wang, Mingyi, et al. (author) Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation 2022 In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 605:7910, s. 483-489 Journal article (peer-reviewed)abstract New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region. Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO3–H2SO4–NH3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.
20.	Ylisirniö, Arttu, et al. (author) Composition and volatility of secondary organic aerosol (SOA) formed from oxidation of real tree emissions compared to simplified volatile organic compound (VOC) systems 2020 In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:9, s. 5629-5644 Journal article (peer-reviewed)abstract Secondary organic aerosol (SOA) is an important constituent of the atmosphere where SOA particles are formed chiefly by the condensation or reactive uptake of oxidation products of volatile organic compounds (VOCs). The mass yield in SOA particle formation, as well as the chemical composition and volatility of the particles, is determined by the identity of the VOC precursor(s) and the oxidation conditions they experience. In this study, we used an oxidation flow reactor to generate biogenic SOA from the oxidation of Scots pine emissions. Mass yields, chemical composition and volatility of the SOA particles were characterized and compared with SOA particles formed from oxidation of alpha-pinene and from a mixture of acyclic-monocyclic sesquiterpenes (farnesenes and bisabolenes), which are significant components of the Scots pine emissions. SOA mass yields for Scots pine emissions dominated by farnesenes were lower than for a-pinene but higher than for the artificial mixture of farne-senes and bisabolenes. The reduction in the SOA yield in the farnesene- and bisabolene-dominated mixtures is due to exocyclic C =C bond scission in these acyclic-monocyclic sesquiterpenes during ozonolysis leading to smaller and generally more volatile products. SOA particles from the oxi- dation of Scots pine emissions had similar or lower volatility than SOA particles formed from either a single precursor or a simple mixture of VOCs. Applying physical stress to the Scots pine plants increased their monoterpene, especially monocyclic beta-phellandrene, emissions, which further decreased SOA particle volatility and increased SOA mass yield. Our results highlight the need to account for the chemical complexity and structure of real-world biogenic VOC emissions and stress-induced changes to plant emissions when modelling SOA production and properties in the atmosphere. These results emphasize that a simple increase or decrease in relative monoterpene and sesquiterpene emissions should not be used as an indicator of SOA particle volatility.

Skapa referenser, mejla, bekava och länka

Permalink

Träfflista för sökning "WFRF:(Schobesberger Siegfried) "

Refine your search

Year