Auflistung nach Autor:in "Gysel, Martin"

Gerade angezeigt 1 - 20 von 64

13-month climatology of the aerosol hygroscopicity at the free tropospheric site Jungfraujoch (3580 m a.s.l.)
(Copernicus, 16.11.2010) Kammermann, Lukas; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs
A hygroscopicity tandem differential mobility analyzer (HTDMA) was operated at the high-alpine site Jungfraujoch in order to characterize the hygroscopic diameter growth factors of the free tropospheric Aitken and accumulation mode aerosol. More than ~5000 h of valid data were collected for the dry diameters D0 = 35, 50, 75, 110, 165, and 265 nm during the 13-month measurement period from 1 May 2008 through 31 May 2009. No distinct seasonal variability of the hygroscopic properties was observed. Annual mean hygroscopic diameter growth factors (D/D0) at 90% relative humidity were found to be 1.34, 1.43, and 1.46 for D0 = 50, 110, and 265 nm, respectively. This size dependence can largely be attributed to the Kelvin effect because corresponding values of the hygroscopicity parameter κ are nearly independent of size. The mean hygroscopicity of the Aitken and accumulation mode aerosol at the free tropospheric site Jungfraujoch was found to be κ≈0.24 with little variability throughout the year. The impact of Saharan dust events, a frequent phenomenon at the Jungfraujoch, on aerosol hygroscopicity was shown to be negligible for D0<265 nm. Thermally driven injections of planetary boundary layer (PBL) air, particularly observed in the early afternoon of summer days with convective anticyclonic weather conditions, lead to a decrease of aerosol hygroscopicity. However, the effect of PBL influence is not seen in the annual mean hygroscopicity data because the effect is small and those conditions (weather class, season and time of day) with PBL influence are relatively rare. Aerosol hygroscopicity was found to be virtually independent of synoptic wind direction during advective weather situations, i.e. when horizontal motion of the atmosphere dominates over thermally driven convection. This indicates that the hygroscopic behavior of the aerosol observed at the Jungfraujoch can be considered representative of the lower free troposphere on at least a regional if not continental scale.
01A - Beitrag in wissenschaftlicher Zeitschrift
A 17 month climatology of the cloud condensation nuclei number concentration at the high alpine site Jungfraujoch
(Wiley, 24.05.2011) Jurányi, Zsófia; Gysel, Martin; Weingartner, Ernest; Bukowiecki, Nicolas; Kammermann, Lorenz; Baltensperger, Urs
Between May 2008 and September 2009 the cloud condensation nuclei (CCN) number concentration, NCCN, was measured at the high alpine site Jungfraujoch, which is located in the free troposphere most of the time. Measurements at 10 different supersaturations (0.12%–1.18%) were made using a CCN counter (CCNC). The monthly median NCCN values show a distinct seasonal variability with ∼5–12 times higher values in summer than in winter. The major part of this variation can be explained by the seasonal amplitude of total aerosol number concentration (∼4.5 times higher values in summer), but it is further amplified (factor of ∼1.1–2.6) by a shift of the particle number size distribution toward slightly larger sizes in summer. In contrast to the extensive properties, the monthly median of the critical dry diameter, above which the aerosols activate as CCN, does not show a seasonal cycle (relative standard deviations of the monthly median critical dry diameters at the different supersaturations are 4–9%) or substantial variability (relative standard deviations of individual data points at the different supersaturations are less than 18–37%). The mean CCN-derived hygroscopicity of the aerosol corresponds to a value of the hygroscopicity parameter κ of 0.20 (assuming a surface tension of pure water) with moderate supersaturation dependence. NCCN can be reliably predicted throughout the measurement period with knowledge of the above-mentioned averaged κ value and highly time-resolved (∼5 min) particle number size distribution data. The predicted NCCN was within 0.74 to 1.29 times the measured value during 80% of the time (94,499 data points in total at 10 different supersaturations).
01A - Beitrag in wissenschaftlicher Zeitschrift
A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles
(Copernicus, 19.09.2008) Zardini, Alessandro A.; Sjogren, S.; Marcolli, Claudia; Krieger, Ulrich K.; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs; Peter, Thomas
Atmospheric aerosols are often mixtures of inorganic and organic material. Organics can represent a large fraction of the total aerosol mass and are comprised of water-soluble and insoluble compounds. Increasing attention was paid in the last decade to the capability of mixed inorganic/organic aerosol particles to take up water (hygroscopicity). We performed hygroscopicity measurements of internally mixed particles containing ammonium sulfate and carboxylic acids (citric, glutaric, adipic acid) in parallel with an electrodynamic balance (EDB) and a hygroscopicity tandem differential mobility analyzer (HTDMA). The organic compounds were chosen to represent three distinct physical states. During hygroscopicity cycles covering hydration and dehydration measured by the EDB and the HTDMA, pure citric acid remained always liquid, adipic acid remained always solid, while glutaric acid could be either. We show that the hygroscopicity of mixtures of the above compounds is well described by the Zdanovskii-Stokes-Robinson (ZSR) relationship as long as the two-component particle is completely liquid in the ammonium sulfate/glutaric acid system; deviations up to 10% in mass growth factor (corresponding to deviations up to 3.5% in size growth factor) are observed for the ammonium sulfate/citric acid 1:1 mixture at 80% RH. We observe even more significant discrepancies compared to what is expected from bulk thermodynamics when a solid component is present. We explain this in terms of a complex morphology resulting from the crystallization process leading to veins, pores, and grain boundaries which allow for water sorption in excess of bulk thermodynamic predictions caused by the inverse Kelvin effect on concave surfaces.
01A - Beitrag in wissenschaftlicher Zeitschrift
A European aerosol phenomenology - 6. Scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
(Copernicus, 2018) Pandolfi, Marco; Alados-Arboledas, Lucas; Alastuey, Andrés; Andrade, Marcos; Angelov, Christo; Artiñano, Begoña; Backman, John; Baltensperger, Urs; Bonasoni, Paolo; Bukowiecki, Nicolas; Collaud Coen, Martine; Conil, Sébastien; Coz, Esther; Crenn, Vincent; Dudoitis, Vadimas; Ealo, Marina; Eleftheriadis, Kostas; Favez, Olivier; Fetfatzis, Prodromos; Fiebig, Markus; Flentje, Harald; Ginot, Patrick; Gysel, Martin; Henzing, Bas; Hoffer, Andras; Holubova Smejkalova, Adela; Kalapov, Ivo; Kalivitis, Nikos; Kouvarakis, Giorgos; Kristensson, Adam; Kulmala, Markku; Lihavainen, Heikki; Lunder, Chris; Luoma, Krista; Lyamani, Hassan; Marinoni, Angela; Mihalopoulos, Nikolaos; Moerman, Marcel; Nicolas, José; O'Dowd, Colin D.; Petäjä, Tuukka; Petit, Jean-Eudes; Pichon, Jean Marc; Prokopciuk, Nina; Putaud, Jean-Philippe; Rodríguez, Sergio; Sciare, Jean; Sellegri, Karine; Swietlicki, Erik; Titos, Gloria; Tuch, Thomas; Tunved, Peter; Ulevicius, Vidmantas; Vaishya, Aditya; Vana, Milan; Virkkula, Aki; Vratolis, Stergios; Weingartner, Ernest; Wiedensohler, Alfred; Laj, Paolo
This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of σsp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, σsp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intra-annual variability. At mountain sites, higher σsp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher σsp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low σsp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high σsp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of σsp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of σsp are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
01A - Beitrag in wissenschaftlicher Zeitschrift
A European aerosol phenomenology-5. Climatology of black carbon optical properties at 9 regional background sites across Europe
(Elsevier, 2016) Zanatta, Marco; Gysel, Martin; Bukowiecki, Nicolas; Müller, Thomas; Weingartner, Ernest; Areskoug, Hans; Fiebig, Markus; Yttri, Karl Espen; Mihalopoulos, Nikolaos; Kouvarakis, Giorgos; Beddows, David; Harrison, Roy; Cavalli, Fabrizia; Putaud, Jean; Spindler, Gerald; Wiedensohler, Alfred; Alastuey, Andrés; Pandolfi, Marco; Sellegri, Karine; Swietlicki, Erik; Jaffrezo, Jean-Luc; Baltensperger, Urs; Laj, Paolo
01A - Beitrag in wissenschaftlicher Zeitschrift
A review of more than 20 years of aerosol observation at the high altitude research station Jungfraujoch, Switzerland (3580 m asl)
(Taiwan Association for Aerosol Research, 2016) Bukowiecki, Nicolas; Weingartner, Ernest; Gysel, Martin; Coen, Martine Collaud; Zieger, Paul; Herrmann, Erik; Steinbacher, Martin; Gäggeler, Heinz W.; Baltensperger, Urs
01A - Beitrag in wissenschaftlicher Zeitschrift
A study of wood burning and traffic aerosols in an Alpine valley using a multi-wavelength aethalometer
(Elsevier, 20.09.2008) Sandradewi, Jisca; Prévôt, André S.H.; Weingartner, Ernest; Schmidhauser, Ralph; Gysel, Martin; Baltensperger, Urs
We present a study of aerosol light absorption using a multi-wavelength Aethalometer (l ¼ 370–950 nm) in an Alpine valley where the major local emissions of aerosols in winter are from domestic wood burning and traffic. The measurements were done in winter and summer periods in 2004 and 2005. Much stronger diurnal trends in CO, NOx and aerosol light absorption parameters were observed in winter than in summer. The average (71 S.D.) PM10 concentrations measured at this site were 31.5721.7 mg m 3 in winter and 15.8710.0 mg m 3 in summer. The highest PM10 concentrations were observed between 18:00 and 22:00 h CET in both campaigns, with 45.4721.0 mg m 3 for winter and 21.079.5 mg m 3 for summer. The average (71 S.D.) power law exponents of the absorption coefficients (also called absorption exponent) with l ¼ 370–950 nm, a370–950 nm were 1.670.25 in winter and 1.170.05 in summer. The calculation of a separately for lower and higher wavelengths (i.e., a370–520 nm and a660–950 nm) provided a better description of the wavelength dependence from the UV- to the near-IR region. The highest mean values of a370–520 nm and a660–950 nm were observed between 22:00 and 02:00 h CET in winter with 2.770.4 and 1.370.1, respectively. Comparison of a370–520 nm with CO and NOx data indicated that the relative contribution of wood burning versus traffic was responsible for the seasonal and diurnal variability of a. The seasonal and diurnal trends of a were not attributed to changes in the particle size since the aerosol volume size distributions (dV/d log D) were found to be similar in both campaigns.
01A - Beitrag in wissenschaftlicher Zeitschrift
A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network
(Copernicus, 2015) Paramonov, Mikhail; Kerminen, Veli-Matti; Gysel, Martin; Aalto, Pasi Pekka; Andreae, Meinrat O.; Asmi, Eija; Baltensperger, Urs; Bougiatioti, Aikaterini; Brus, David; Frank, Göran; Good, Nicholas; Gunthe, Sachin S.; Hao, Liqing; Irwin, Martin; Jaatinen, Antti; Jurányi, Zsófia; King, S. M.; Kortelainen, Aki; Kristensson, Adam; Lihavainen, Heikki; Kulmala, Markku; Lohmann, Ulrike; Martin, Scot T.; McFiggans, Gordon; Mihalopoulos, Nikolaos; Nenes, Athanasios; O'Dowd, Colin D.; Ovadnevaite, Jurgita; Petäjä, Tuukka; Pöschl, Ulrich; Roberts, Greg; Rose, Diana; Svenningsson, Birgitta; Swietlicki, Erik; Weingartner, Ernest; Whitehead, James; Wiedensohler, Alfred; Wittbom, Cerina; Sierau, Berko
Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (NCCN) to the total number concentration of particles (NCN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations – exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A50 and A100, respectively) renders a much more stable dependence of A on S; A50 and A100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of NCCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of NCCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol–cloud interactions in various environments.
01A - Beitrag in wissenschaftlicher Zeitschrift
Analysis of long‐term aerosol size distribution data from Jungfraujoch with emphasis on free tropospheric conditions, cloud influence, and air mass transport
(Wiley, 2015) Herrmann, Erik; Weingartner, Ernest; Henne, Stephan; Vuilleumier, Laurent; Bukowiecki, Nicolas; Steinbacher, Martin; Conen, Franz; Collaud Coen, Martine; Hammer, Emanuel; Jurányi, Zsófia; Baltensperger, Urs; Gysel, Martin
Six years of aerosol size distribution measurements between 20 and 600 nm diameters and total aerosol concentration above 10 nm from March 2008 to February 2014 at the high‐alpine site Jungfraujoch are presented. The size distribution was found to be typically bimodal with mode diameters and widths relatively stable throughout the year and the observation period. New particle formation was observed on 14.5% of all days without a seasonal preference. Particles typically grew only into the Aitken mode and did not reach cloud condensation nucleus (CCN) sizes on the time scale of several days. Growth of preexisting particles in the Aitken mode, on average, contributed very few CCN. We concluded that the dominant fraction of CCN at Jungfraujoch originated in the boundary layer. A number of approaches were used to distinguish free tropospheric (FT) conditions and episodes with planetary boundary layer (PBL) influence. In the absence of PBL injections, the concentration of particles larger than 90 nm (N90, roughly corresponding to the CCN concentration) reached a value ~40 cm−3 while PBL influence caused N90 concentrations of several hundred or even 1000 cm−3. Comparing three criteria for free tropospheric conditions, we found FT prevalence for 39% of the time with over 60% during winter and below 20% during summer. It is noteworthy that a simple criterion based on standard trace gas measurements appeared to outperform alternative approaches.
01A - Beitrag in wissenschaftlicher Zeitschrift
Analysis of the hygroscopic and volatile properties of ammonium sulphate seeded and unseeded SOA particles
(Copernicus, 28.01.2009) Meyer, Nic K.; Duplissy, Jonathan; Gysel, Martin; Metzger, Axel; Dommen, Josef; Weingartner, Ernest; Alfarra, Rami; Prévôt, André S.H.; Fletcher, C; Good, Nicholas; McFiggans, Gordan; Jonsson, Åsa M.; Hallquist, Mattias; Baltensperger, Urs; Ristovski, Zoran D.
The volatile and hygroscopic properties of ammonium sulphate seeded and unseeded secondary organic aerosol (SOA) derived from the photo-oxidation of atmospherically relevant concentrations of α-pinene were studied. The seed particles were electrospray generated ammonium sulphate ((NH4)2SO4) having diameters of approximately 33 nm with a quasi-mono-disperse size distribution (geometric standard deviation σg=1.3). The volatile and hygroscopic properties of both seeded and unseeded SOA were simultaneously measured with a VH-TDMA (volatility – hygroscopicity tandem differential mobility analyzer). VH-TDMA measurements of unseeded SOA show a decrease in the hygroscopic growth (HGF) factor for increased volatilisation temperatures such that the more volatile compounds appear to be more hygroscopic. This is opposite to the expected preferential evaporation of more volatile but less hygroscopic material, but could also be due to enhanced oligomerisation occurring at the higher temperature in the thermodenuder. In addition, HGF measurements of seeded SOA were measured as a function of time at two relative humidities, below (RH 75%) and above (RH 85%) the deliquescence relative humidity (DRH) of the pure ammonium sulphate seeds. As these measurements were conducted during the onset phase of photo-oxidation, during particle growth, they enabled us to find the dependence of the HGF as a function of the volume fraction of the SOA coating. HGF's measured at RH of 85% showed a continuous decrease as the SOA coating thickness increased. The measured growth factors show good agreements with ZSR predictions indicating that, at these RH values, there are only minor solute-solute interactions. At 75% RH, as the SOA fraction increased, a rapid increase in the HGF was observed indicating that an increasing fraction of the (NH4)2SO4 is subject to a phase transition, going into solution, with an increasing volume fraction of SOA. To our knowledge this is the first time that SOA derived from photo-oxidised α-pinene has been shown to affect the equilibrium water content of inorganic aerosols below their DRH. For SOA volume fractions above ~0.3 the measured growth factor followed roughly parallel to the ZSR prediction based on fully dissolved (NH4)2SO4 although with a small difference that was just larger than the error estimate. Both incomplete dissolution and negative solute-solute interactions could be responsible for the lower HGF observed compared to the ZSR predictions.
01A - Beitrag in wissenschaftlicher Zeitschrift
Black carbon physical properties and mixing state in the European megacity Paris
(Copernicus, 2013) Laborde, Marie; Crippa, Monica; Tritscher, Torsten; Jurányi, Zsófia; Decarlo, Peter; Temime-Roussel, Brice; Marchand, Nicolas; Eckhardt, Sabine; Stohl, Andreas; Baltensperger, Urs; Prévôt, André S.H.; Weingartner, Ernest; Gysel, Martin
Aerosol hygroscopicity and refractory black carbon (rBC) properties were characterised during wintertime at a suburban site in Paris, one of the biggest European cities. Hygroscopic growth factor (GF) frequency distributions, characterised by distinct modes of more-hygroscopic background aerosol and non- or slightly hygroscopic aerosol of local (or regional) origin, revealed an increase of the relative contribution of the local sources compared to the background aerosol with decreasing particle size. BC-containing particles in Paris were mainly originating from fresh traffic emissions, whereas biomass burning only gave a minor contribution. The mass size distribution of the rBC cores peaked on average at an rBC core mass equivalent diameter of DMEV ~ 150 nm. The BC-containing particles were moderately coated (coating thickness Δcoat ~ 33 nm on average for rBC cores with DMEV = 180–280 nm) and an average mass absorption coefficient (MAC) of ~ 8.6 m2 g−1 at the wavelength λ = 880 nm was observed. Different time periods were selected to investigate the properties of BC-containing particles as a function of source and air mass type. The traffic emissions were found to be non-hygroscopic (GF ≈ 1.0), and essentially all particles with a dry mobility diameter (D0) larger than D0 = 110 nm contained an rBC core. rBC from traffic emissions was further observed to be uncoated within experimental uncertainty (Δcoat ~ 2 nm ± 10 nm), to have the smallest BC core sizes (maximum of the rBC core mass size distribution at DMEV ~ 100 nm) and to have the smallest MAC (~ 7.3 m2g−1 at λ = 880 nm). The biomass burning aerosol was slightly more hygroscopic than the traffic emissions (with a distinct slightly-hygroscopic mode peaking at GF ≈ 1.1–1.2). Furthermore, only a minor fraction (&leq; 10%) of the slightly-hygroscopic particles with 1.1 &leq; GF &leq; 1.2 (and D0 = 265 nm) contained a detectable rBC core. The BC-containing particles from biomass burning were found to have a medium coating thickness as well as slightly larger mean rBC core sizes and MAC values compared to traffic emissions. The aerosol observed under the influence of aged air masses and air masses from Eastern Continental Europe was dominated by a~more-hygroscopic mode peaking at GF ≈ 1.6. Most particles (95%), in the more-hygroscopic mode at D0 = 265 nm, did not contain a detectable rBC core. A significant fraction of the BC-containing particles had a substantial coating with non-refractory aerosol components. MAC values of ~ 8.8 m2g−1 and ~ 8.3 m2g−1 at λ = 880 nm and mass mean rBC core diameters of 150 nm and 200 nm were observed for the aged and continental air mass types, respectively. The reason for the larger rBC core sizes compared to the fresh emissions – transport effects or a different rBC source – remains unclear. The dominant fraction of the BC-containing particles was found to have no or very little coating with non-refractory matter. The lack of coatings is consistent with the observation that the BC-containing particles are non- or slightly-hygroscopic, which makes them poor cloud condensation nuclei. It can therefore be expected that wet removal through nucleation scavenging is inefficient for fresh BC-containing particles in urban plumes. The mixing-state-specific cloud droplet activation behaviour of BC-containing particles including the effects of atmospheric aging processes should be considered in global simulations of atmospheric BC, as the wet removal efficiency remains a major source of uncertainty in its life-cycle.
01A - Beitrag in wissenschaftlicher Zeitschrift
CCN activity and volatility of β-caryophyllene secondary organic aerosol
(Copernicus, 2013) Frosch, Mia; Bilde, Merete; Nenes, Athanasios; Praplan, Arnaud P.; Jurányi, Zsófia; Dommen, Josef; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs
In a series of smog chamber experiments, the cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) generated from ozonolysis of β-caryophyllene was characterized by determining the CCN derived hygroscopicity parameter, κCCN, from experimental data. Two types of CCN counters, operating at different temperatures, were used. The effect of semi-volatile organic compounds on the CCN activity of SOA was studied using a thermodenuder. Overall, SOA was only slightly CCN active (with κCCN in the range 0.001–0.16), and in dark experiments with no OH scavenger present, κCCN decreased when particles were sent through the thermodenuder (with a temperature up to 50 °C). SOA was generated under different experimental conditions: In some experiments, an OH scavenger (2-butanol) was added. SOA from these experiments was less CCN active than SOA produced in experiments without an OH scavenger (i.e. where OH was produced during ozonolysis). In other experiments, lights were turned on, either without or with the addition of HONO (OH source). This led to the formation of more CCN active SOA. SOA was aged up to 30 h through exposure to ozone and (in experiments with no OH scavenger present) to OH. In all experiments, the derived κCCN consistently increased with time after initial injection of β-caryophyllene, showing that chemical ageing increases the CCN activity of β-caryophyllene SOA. κCCN was also observed to depend on supersaturation, which was explained either as an evaporation artifact from semi-volatile SOA (only observed in experiments lacking light exposure) or, alternatively, by effects related to chemical composition depending on dry particle size. Using the method of Threshold Droplet Growth Analysis it was also concluded that the activation kinetics of the SOA do not differ significantly from calibration ammonium sulphate aerosol for particles aged for several hours.
01A - Beitrag in wissenschaftlicher Zeitschrift
Changes of hygroscopicity and morphology during ageing of diesel soot
(Institute of Physics Publishing, 2011) Tritscher, Torsten; Jurányi, Zsófia; Martin, Maria; Chirico, Roberto; Gysel, Martin; Heringa, Maarten F.; DeCarlo, Peter F.; Sierau, Berko; Prévôt, André S.H.; Weingartner, Ernest; Baltensperger, Urs
01A - Beitrag in wissenschaftlicher Zeitschrift
Chemical and physical influences on aerosol activation in liquid clouds. A study based on observations from the Jungfraujoch, Switzerland
(Copernicus, 2016) Hoyle, Christopher R.; Webster, Clare S.; Rieder, Harald E.; Nenes, Athanasios; Hammer, Emanuel; Herrmann, Erik; Gysel, Martin; Bukowiecki, Nicolas; Weingartner, Ernest; Steinbacher, Martin; Baltensperger, Urs
A simple statistical model to predict the number of aerosols which activate to form cloud droplets in warm clouds has been established, based on regression analysis of data from four summertime Cloud and Aerosol Characterisation Experiments (CLACE) at the high-altitude site Jungfraujoch (JFJ). It is shown that 79 % of the observed variance in droplet numbers can be represented by a model accounting only for the number of potential cloud condensation nuclei (defined as number of particles larger than 80 nm in diameter), while the mean errors in the model representation may be reduced by the addition of further explanatory variables, such as the mixing ratios of O3, CO, and the height of the measurements above cloud base. The statistical model has a similar ability to represent the observed droplet numbers in each of the individual years, as well as for the two predominant local wind directions at the JFJ (northwest and southeast). Given the central European location of the JFJ, with air masses in summer being representative of the free troposphere with regular boundary layer in-mixing via convection, we expect that this statistical model is generally applicable to warm clouds under conditions where droplet formation is aerosol limited (i.e. at relatively high updraught velocities and/or relatively low aerosol number concentrations). A comparison between the statistical model and an established microphysical parametrization shows good agreement between the two and supports the conclusion that cloud droplet formation at the JFJ is predominantly controlled by the number concentration of aerosol particles.
01A - Beitrag in wissenschaftlicher Zeitschrift
Cloud forming potential of secondary organic aerosol under near atmospheric conditions
(Wiley, 2008) Duplissy, Jonathan; Gysel, Martin; Alfarra, M. Rami; Dommen, Josef; Metzger, Axel; Prévôt, André S.H.; Weingartner, Ernest; Laaksonen, Ari; Raatikainen, Tomi; Good, Nicholas; Turner, S. Fiona; McFiggans, Gordon; Baltensperger, Urs
Cloud droplets form by nucleation on atmospheric aerosol particles. Populations of such particles invariably contain organic material, a major source of which is thought to be condensation of photo‐oxidation products of biogenic volatile organic compounds (VOCs). We demonstrate that smog chamber studies of the formation of such biogenic secondary organic aerosol (SOA) formed during photo‐oxidation must be conducted at near atmospheric concentrations to yield atmospherically representative particle composition, hygroscopicity and cloud‐forming potential. Under these conditions, the hygroscopicity measured at 95% relative humidity can be used reliably to predict the CCN activity of the SOA particles by assuming droplet surface tension of pure water. We also show that the supersaturation required to activate a given size of particle decreases with age.
01A - Beitrag in wissenschaftlicher Zeitschrift
Coated soot particles with tunable, well-controlled properties generated in the laboratory with a miniCAST BC and a micro smog chamber
(Elsevier, 28.05.2021) Ess, Michaela N.; Bertò, Michele; Keller, Alejandro; Gysel, Martin; Vasilatou, Konstantina
A Micro Smog Chamber (MSC) was coupled for the first time with a miniCAST 5201 Type BC combustion generator with the aim to produce a series of stable and reproducible model aerosols simulating the physical properties of combustion particles present in ambient air. With this setup it was possible to generate particles ranging from “fresh” soot (single scattering albedo SSA≤0.05, absorption Ångström exponent AAE close to 1, high EC/TC mass fraction (approximately 90%) and mobility diameter typically <100 nm) to “aged” soot with different amounts of organic coating. The “aged” soot particles could grow up to 200 nm and exhibited high SSA (up to 0.7 at λ = 870 nm), an increased AAE (up to 1.7) and low EC/TC mass fraction (down to <10%). The ageing was achieved by coating the soot particles with increasing amounts of secondary organic matter (SOM) formed by the photo-oxidation of α-pinene or mesitylene in the MSC. Thereby, the SSA and AAE increased with coating thickness, while the EC/TC mass fraction decreased. Over the experimental period of 2 h, the generation of the “aged” soot aerosols was stable with a standard deviation in particle size and number concentration of <1% and <6%, respectively. The day-to-day reproducibility was also satisfactory: with α-pinene as SOM precursor the variability (standard deviation) in particle size was <2% and in the AAE and SSA < 6%. Particle number concentrations up to 106 cm−3 and mass concentrations up to 15 mg/m3 (depending on particle size and SOM amount) could be generated, much higher than what has been reported with other oxidation flow reactors. The generated carbonaceous aerosols could find useful applications in the field of aerosol instrument calibration, particularly in the standardization of filter-based absorption photometers under controlled conditions.
01A - Beitrag in wissenschaftlicher Zeitschrift
Coating of soot and (NH4)2SO4 particles by ozonolysis products of α-pinene
(Elsevier, 10/2003) Saathoff, Harald; Naumann, Karl-Heinz; Schnaiter, Martin; Schöck, Werner; Möhler, Ottmar; Schurath, Ulrich; Weingartner, Ernest; Gysel, Martin; Baltensperger, Urs
The ozonolysis of α-pinene in a large aerosol chamber was used to generate secondary organic aerosol (SOA) mass by homogeneous nucleation, or by heterogeneous nucleation, either on soot, or on (NH4)2SO4 seed aerosols. The rate of the α-pinene + ozone reaction and the aerosol yield of ∼19% are in good agreement with literature data. The organic coating of soot particles leads to a compaction of the fractal agglomerates expressed by an increase in fractal dimension from 1.9 to 2.1 for Diesel soot, and from 2.0 to 2.3 for spark generated “Palas” soot. The dielectric coating of the soot particles with SOA layers between 2 to 11 nm gives rise to a substantial enhancement of their single scattering albedo, from about 0.2 to 0.5, and increases the effective absorption coefficients of both soot types by ca. 30%. The coating of both soot types increases the hygroscopic growth factors (HGF) to values close below the HGF measured for pure SOA material d/d0∼1:12 at 90% RH.
01A - Beitrag in wissenschaftlicher Zeitschrift
Contribution of new particle formation to the total aerosol concentration at the high‐altitude site Jungfraujoch (3580 m asl, Switzerland)
(Wiley, 2016) Tröstl, Jasmin; Herrmann, Erik; Frege, Carla; Bianchi, Federico; Molteni, Ugo; Bukowiecki, Nicolas; Hoyle, Christopher R.; Steinbacher, Martin; Weingartner, Ernest; Dommen, Josef; Gysel, Martin; Baltensperger, Urs
Previous modeling studies hypothesized that a large fraction of cloud condensation nuclei (CCN) is attributed to new particle formation (NPF) in the free troposphere. Despite the potential importance of this process, only few long‐term observations have been performed to date. Here we present the results of a 12 month campaign of NPF observations at the high‐altitude site Jungfraujoch (JFJ, 3580 m above sea level (asl)). Our results show that NPF significantly adds to the total aerosol concentration at the JFJ and only occurs via previous precursor entrainment from the planetary boundary layer (PBL). Freshly nucleated particles do not directly grow to CCN size (90 nm) within observable time scales (maximum 48 h). The contribution of NPF to the CCN concentration is low within this time frame compared to other sources, such as PBL entrainment of larger particles. A multistep growth mechanism is proposed which allows previously formed Aitken mode particles to add to the CCN concentration. A parametrization is derived to explain formation rates at the JFJ, showing that precursor concentration, PBL influence, and global radiation are the key factors controlling new particle formation at the site.
01A - Beitrag in wissenschaftlicher Zeitschrift
EUCAARI ion spectrometer measurements at 12 European sites – analysis of new particle formation events
(Copernicus, 25.08.2010) Manninen, Hanna E.; Nieminen, Tuomo; Asmi, Eija; Gagné, Stéphanie; Häkkinen, Silja; Lehtipalo, Katrianne; Aalto, Pasi Pekka; Vana, Marko; Mirme, Aadu; Mirme, Sander; Hõrrak, Urmas; Plass-Dülmer, Christian; Stange, Gert; Kiss, Gyula; Hoffer, András; Törő, N.; Moerman, Marcel; Henzing, Bas; de Leeuw, Gerrit; Brinkenberg, Marcel; Kouvarakis, Giorgos N.; Bougiatioti, Aikaterini; Mihalopoulos, Nikolaos; O'Dowd, Colin D.; Ceburnis, Darius; Arneth, Almut; Svenningsson, Brigitta; Swietlicki, Erik; Tarozzi, Leone; Decesari, Stefano; Facchini, Maria Cristina; Birmili, Wolfram; Sonntag, André; Wiedensohler, Alfred; Boulon, Julien; Sellegri, Karine; Laj, Paolo; Gysel, Martin; Bukowiecki, Nicolas; Weingartner, Ernest; Wehrle, Günther; Laaksonen, Ari; Hamed, Amar; Joutsensaari, Jorma; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku
We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range ~1–42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1–30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.
01A - Beitrag in wissenschaftlicher Zeitschrift
Evolution of nanoparticle composition in CLOUD in presence of sulphuric acid, ammonia and organics
(AIP Publishing, 24.06.2013) Keskinen, Helmi; Virtanen, Annele; Joutsensaari, Jorma; Tsagkogeorgas, Georgios; Duplissy, Jonathan; Schobesberger, Siegfried; Gysel, Martin; Riccobono, Francesco; Slowik, Jay Gates; Bianchi, Federico; Yli-Juuti, Taina; Lehtipalo, Katrianne; Rondo, Linda; Breitenlechner, Martin; Kupc, Agnieszka; Almeida, João; Amorim, Antonio; Dunne, Eimear M.; Downard, Andrew J.; Ehrhart, Sebastian; Franchin, Alessandro; Kajos, Maija K.; Kirkby, Jasper; Kürten, Andreas; Nieminen, Tuomo; Makhmutov, Vladimir; Mathot, Serge; Miettinen, Pasi; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Santos, Filipe D.; Schallhart, Simon; Sipilä, Mikko; Stozhkov, Yuri; Tomé, Antonio; Vaattovaara, Petri; Wimmer, Daniela; Prévôt, André S.H.; Dommen, Josef; Donahue, Neil M.; Flagan, Richard C.; Viisanen, Yrjö; Weingartner, Ernest; Riipinen, Ilona; Hansel, Armin; Curtius, Joachim; Kulmala, Markku; Worsnop, Douglas R.; Baltensperger, Urs; Wex, Heike; Stratmann, Frank; Laaksonen, Ari; DeMott, Paul J.; O'Dowd, Colin D.
04B - Beitrag Konferenzschrift