Latest documents http://publikationen.ub.uni-frankfurt.de/index/index/ Wed, 20 Mar 2013 10:30:06 +0100 Wed, 20 Mar 2013 10:30:06 +0100 http://publikationen.ub.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.ub.uni-frankfurt.de/frontdoor/index/index/docId/29199 Wed, 20 Mar 2013 10:30:06 +0100 http://publikationen.ub.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.ub.uni-frankfurt.de/frontdoor/index/index/docId/29247 Tue, 19 Mar 2013 16:08:58 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26783 In the abstract of the manuscript, the following sentence needs to be corrected: “A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates.” “metal silicates” is wrong. It should be “aluminosilicates”. Dennis Niedermeier; Susan Hartmann; Tina Clauss; Heike Wex; Alexei Kiselev; Ryan C. Sullivan; Paul J. DeMott; Markus D. Petters; Paul Reitz; Johannes Schneider; Eugene Mikhailov; Berko Sierau; Olaf Stetzer; Bernd Reimann; Ulrich Bundke; Raymond A. Shaw; Angela Buchholz; Thomas F. Mentel; Frank Stratmann article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26783 Mon, 15 Oct 2012 15:39:34 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26782 During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influence of various surface modifications on the ice nucleating ability of Arizona Test Dust (ATD) particles in the immersion freezing mode. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 °C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a single particle. Temperature dependent frozen fractions of these droplets were determined in a temperature range between −40 °C ≤T≤−28 °C. The pure ATD particles nucleated ice over a broad temperature range with their freezing behavior being separated into two freezing branches characterized through different slopes in the frozen fraction vs. temperature curves. Coating the ATD particles with sulfuric acid resulted in the particles' IN potential significantly decreasing in the first freezing branch (T>−35 °C) and a slight increase in the second branch (T≤−35 °C). The addition of water vapor after the sulfuric acid coating caused the disappearance of the first freezing branch and a strong reduction of the IN ability in the second freezing branch. The presence of ammonia gas during water vapor exposure had a negligible effect on the particles' IN ability compared to the effect of water vapor. Heating in the thermodenuder led to a decreased IN ability of the sulfuric acid coated particles for both branches but the additional heat did not or only slightly change the IN ability of the pure ATD and the water vapor exposed sulfuric acid coated particles. In other words, the combination of both sulfuric acid and water vapor being present is a main cause for the ice active surface features of the ATD particles being destroyed. A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates. The strongly enhanced reaction between sulfuric acid and dust in the presence of water vapor and the resulting significant reductions in IN potential are of importance for atmospheric ice cloud formation. Our findings suggest that the IN concentration can decrease by up to one order of magnitude for the conditions investigated. Dennis Niedermeier; Susan Hartmann; Tina Clauss; Heike Wex; Alexei Kiselev; Ryan C. Sullivan; Paul J. DeMott; Markus D. Petters; Paul Reitz; Johannes Schneider; Eugene Mikhailov; Berko Sierau; Olaf Stetzer; Bernd Reimann; Ulrich Bundke; Raymond A. Shaw; Angela Buchholz; Thomas F. Mentel; Frank Stratmann article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26782 Mon, 15 Oct 2012 15:28:46 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26781 During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influences of various surface modifications on the immersion freezing behavior of Arizona Test Dust (ATD) particles. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 °C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a single particle. Temperature dependent frozen fractions of these droplets were determined in a temperature range between −40 °C ≤ T ≤ −28 °C. The pure ATD particles nucleated ice over a~broad temperature range with their freezing behavior being separated into two freezing branches characterized through different slopes in the frozen fraction vs. temperature curves. Coating the ATD particles with sulfuric acid resulted in the particles' IN potential significantly decreasing in the first freezing branch (T > −35 °C) and a slight increase in the second branch (T≤ −35 °C). The addition of water vapor after the sulfuric acid coating caused the disappearance of the first freezing branch and a strong reduction of the IN ability in the second freezing branch. The presence of ammonia gas during water vapor exposure had a negligible effect on the particles' IN ability compared to the effect of water vapor. Heating in the thermodenuder led to a decreased IN ability of the sulfuric acid coated particles for both branches but the additional heat did not or only slightly change the IN ability of the pure ATD and the water vapor exposed sulfuric acid coated particles. In other words, the combination of both sulfuric acid and water vapor being present is a main cause for the ice active surface features of the ATD particles being destroyed. A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates. From an atmospheric point of view, and here specifically the influences of atmospheric aging on the IN ability of dust particles, the strongly enhanced reaction between sulfuric acid and dust in the presence of water vapor, and the resulting significant reductions in IN potential, are certainly very interesting. Dennis Niedermeier; Susan Hartmann; Tina Clauss; Heike Wex; Alexei Kiselev; Ryan C. Sullivan; Paul J. DeMott; Markus D. Petters; Paul Reitz; Johannes Schneider; Eugene Mikhailov; Berko Sierau; Olaf Stetzer; Bernd Reimann; Ulrich Bundke; Raymond A. Shaw; Angela Buchholz; Thomas F. Mentel; Frank Stratmann article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26781 Mon, 15 Oct 2012 14:55:42 +0200 http://publikationen.ub.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.ub.uni-frankfurt.de/frontdoor/index/index/docId/20120 Tue, 26 Oct 2010 16:08:52 +0200