Latest documents http://publikationen.stub.uni-frankfurt.de/index/index/ Wed, 20 Mar 2013 10:30:06 +0100 Wed, 20 Mar 2013 10:30:06 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29199 Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed from these compounds in the CLOUD chamber experiments at CERN. The investigation is carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during their growth from sizes of a few nanometers to tens of nanometers was derived from measured hygroscopicity assuming the Zdanovski-Stokes-Robinson relationship, and compared to values gained from the spectrometers. The ZSR-relationship was also applied to obtain the measured ethanol affinities during the particle growth, which were used to derive the volume fractions of sulphuric acid and the other inorganics (e.g. ammonium salts). In the presence of sulphuric acid and ammonia, particles with a mobility diameter of 150 nm were chemically neutralised to ammonium sulphate. In the presence of oxidation products of pinanediol, the organic volume fraction of freshly nucleated particles increased from 0.4 to ∼0.9, with an increase in diameter from 2 to 63 nm. Conversely, the sulphuric acid volume fraction decreased from 0.6 to 0.1 when the particle diameter increased from 2 to 50 nm. The results provide information on the composition of nucleated aerosol particles during their growth in the presence of various combinations of sulphuric acid, ammonia, dimethylamine and organic oxidation products. Helmi Keskinen; Annele Virtanen; Jorma Joutsensaari; Georgios Tsagkogeorgas; Jonathan Duplissy; Siegfried Schobesberger; Martin Gysel; Francesco Riccobono; Jay G. Slowik; Federico Bianchi; Taina Yli-Juuti; Katrianne Lehtipalo; Linda Rondo; Martin Breitenlechner; Agnieszka Kupc; Joao Almeida; António Amorin; Eimear M. Dunne; A. J. Downward; Sebastian Ehrhart; Alessandro Franchin; Maija K. Kajos; Jasper Kirkby; Andreas Kürten; Tuomo Nieminen; Vladimir Makhmutov; Serge Mathot; Pasi Miettinen; Antti Onnela; Tuukka Petäjä; Arnaud Praplan; F. D. Santos; Simon Schallhart; Mikko Sipilä; Yuri Stozhkov; Antonio Tomé; P. Vaattovaara; Daniela Wimmer; Andre Prévôt; Josef Dommen; Neil M. Donahue; Richard C. Flagan; Ernest Weingartner; Yrjö Viisanen; Ilona Riipinen; Armin Hansel; Joachim Curtius; Markku Kulmala; Douglas R. Worsnop; Urs Baltensperger; Heike Wex; Frank Stratmann; Ari Laaksonen article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29199 Wed, 20 Mar 2013 10:30:06 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29247 During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the CLOUD1 experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm−3s−1, and growth rates between 2 and 37 nm h−1. The corresponding H2SO4 concentrations were typically around 106 cm−3 or less. The experimentally-measured formation rates and H2SO4 concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1°C). Jonathan Duplissy; Martin Bødker Enghoff; Karen L. Aplin; Frank Arnold; Heinfried Aufmhoff; Michael Avngaard; Urs Baltensperger; Torsten Bondo; Robert Bingham; Kenneth Carslaw; Joachim Curtius; André David; Bent Fastrup; Stéphanie Gagné; F. Hahn; R. Giles Harrison; Barry Kellett; Jasper Kirkby; Markku Kulmala; Lauri Laakso; Ari Laaksonen; Egil Lillestol; Michael Lockwood; Jyrki Mäkelä; Vladimir Makhmutov; Nigel D. Marsh; Tuomo Nieminen; Antti Onnela; E. Pedersen; Jens Olaf Pepke Pedersen; Josef Polny; Ulrike Reichl; John H. Seinfeld; Mikko Sipilä; Yuri Stozhkov; Frank Stratmann; Henrik Svensmark; J. Svensmark; Rob Veenhof; Bart Verheggen; Yrjö Viisanen; Paul E. Wagner; Günther Wehrle; Ernest Weingartner; Heike Wex; Mats Wilhelmsson; Paul M. Winkler article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29247 Tue, 19 Mar 2013 16:08:58 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/20120 During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm -3 s -1, and growth rates between 2 and 37 nm h -1. The corresponding H2O concentrations were typically around 106 cm -3 or less. The experimentally-measured formation rates and htwosofour concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1 °C) Jonathan Duplissy; Martin Bødker Enghoff; Karen L. Aplin; Frank Arnold; Heinfried Aufmhoff; Michael Avngaard; Urs Baltensperger; Torsten Bondo; Robert Bingham; Kenneth Carslaw; Joachim Curtius; André David; Bent Fastrup; Stéphanie Gagné; F. Hahn; R. Giles Harrison; Barry Kellett; Jasper Kirkby; Markku Kulmala; Lauri Laakso; Ari Laaksonen; Egil Lillestol; Michael Lockwood; Jyrki Mäkelä; Vladimir Makhmutov; Nigel D. Marsh; Tuomo Nieminen; Antti Onnela; E. Pedersen; Jens Olaf Pepke Pedersen; Josef Polny; Ulrike Reichl; John H. Seinfeld; Mikko Sipilä; Yuri Stozhkov; Frank Stratmann; Henrik Svensmark; J. Svensmark; Rob Veenhof; Bart Verheggen; Yrjö Viisanen; Paul E. Wagner; Günther Wehrle; Ernest Weingartner; Heike Wex; Mats Wilhelmsson; Paul M. Winkler article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/20120 Tue, 26 Oct 2010 16:08:52 +0200 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/7837 We synthesised observations of total particle number (CN) concentration from 36 sites around the world. We found that annual mean CN concentrations are typically 300–2000 cm -3 in the marine boundary layer and free troposphere (FT) and 1000–10 000 cm -3 in the continental boundary layer (BL). Many sites exhibit pronounced seasonality with summer time concentrations a factor of 2–10 greater than wintertime concentrations. We used these CN observations to evaluate primary and secondary sources of particle number in a global aerosol microphysics model. We found that emissions of primary particles can reasonably reproduce the spatial pattern of observed CN concentration (R2=0.46) but fail to explain the observed seasonal cycle (R2=0.1). The modeled CN concentration in the FT was biased low (normalised mean bias, NMB=& -88%) unless a secondary source of particles was included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB= -25%). Simulated CN concentrations in the continental BL were also biased low (NMB= -74%) unless the number emission of anthropogenic primary particles was increased or a mechanism that results in particle formation in the BL was included. We ran a number of simulations where we included an empirical BL nucleation mechanism either using the activation-type mechanism (nucleation rate, J, proportional to gas-phase sulfuric acid concentration to the power one) or kinetic-type mechanism (J proportional to sulfuric acid to the power two) with a range of nucleation coefficients. We found that the seasonal CN cycle observed at continental BL sites was better simulated by BL particle formation (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). The nucleation constants that resulted in best overall match between model and observed CN concentrations were consistent with values derived in previous studies from detailed case studies at individual sites. In our model, kinetic and activation-type nucleation parameterizations gave similar agreement with observed monthly mean CN concentrations. Dominick V. Spracklen; Kenneth S. Carslaw; Joonas Merikanto; Graham W. Mann; Carly L. Reddington; Steven Pickering; John A. Ogren; Elisabeth Andrews; Urs Baltensperger; Ernest Weingartner; Michael Boy; Markku Kulmala; Lauri Laakso; Heikki Lihavainen; Niku Kivekäs; Mika Komppula; Nikos Mihalopoulos; G. Kouvarakis; S. Gerard Jennings; Colin D. O'Dowd; Wolfram Birmili; Alfred Wiedensohler; Rolf Weller; John Gras; Paolo Laj; Karine Sellegri; Boris Bonn; Radek Krejci; Ari Laaksonen; Amar Hamed; Andreas Minikin; Roy M. Harrison; Robert Talbot; Youbin Sun article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/7837 Thu, 24 Jun 2010 00:00:00 +0200