Latest documents http://publikationen.stub.uni-frankfurt.de/index/index/ Wed, 20 Mar 2013 14:47:54 +0100 Wed, 20 Mar 2013 14:47:54 +0100 http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29251 Current atmospheric models do not include secondary organic aerosol (SOA) production from gas-phase reactions of polycyclic aromatic hydrocarbons (PAHs). Recent studies have shown that primary semivolatile emissions, previously assumed to be inert, undergo oxidation in the gas phase, leading to SOA formation. This opens the possibility that low-volatility gas-phase precursors are a potentially large source of SOA. In this work, SOA formation from gas-phase photooxidation of naphthalene, 1-methylnaphthalene (1-MN), 2-methylnaphthalene (2-MN), and 1,2-dimethylnaphthalene (1,2-DMN) is studied in the Caltech dual 28-m3 chambers. Under high-NOx conditions and aerosol mass loadings between 10 and 40 μg m, the SOA yields (mass of SOA per mass of hydrocarbon reacted) ranged from 0.19 to 0.30 for naphthalene, 0.19 to 0.39 for 1-MN, 0.26 to 0.45 for 2-MN, and constant at 0.31 for 1,2-DMN. Under low-NOx conditions, the SOA yields were measured to be 0.73, 0.68, and 0.58, for naphthalene, 1-MN, and 2-MN, respectively. The SOA was observed to be semivolatile under high-NOx conditions and essentially nonvolatile under low-NOx conditions, owing to the higher fraction of ring-retaining products formed under low-NOx conditions. When applying these measured yields to estimate SOA formation from primary emissions of diesel engines and wood burning, PAHs are estimated to yield 3–5 times more SOA than light aromatic compounds. PAHs can also account for up to 54% of the total SOA from oxidation of diesel emissions, representing a potentially large source of urban SOA. Arthur Wing Hong Chan; Kathryn E. Kautzman; Puneet Singh Chhabra; Jason D. Surratt; Man N. Chan; John D. Crounse; Andreas Kürten; Paul O. Wennberg; Richard C. Flagan; John H. Seinfeld article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/29251 Wed, 20 Mar 2013 14:47:54 +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/6542 Current atmospheric models do not include secondary organic aerosol (SOA) production from gas-phase reactions of polycyclic aromatic hydrocarbons (PAHs). Recent studies have shown that primary semivolatile emissions, previously assumed to be inert, undergo oxidation in the gas phase, leading to SOA formation. This opens the possibility that low-volatility gas-phase precursors are a potentially large source of SOA. In this work, SOA formation from gas-phase photooxidation of naphthalene, 1-methylnaphthalene (1-MN), 2-methylnaphthalene (2-MN), and 1,2-dimethylnaphthalene (1,2-DMN) is studied in the Caltech dual 28-m3 chambers. Under high-NOx conditions and aerosol mass loadings between 10 and 40 microg m-3, the SOA yields (mass of SOA per mass of hydrocarbon reacted) ranged from 0.19 to 0.30 for naphthalene, 0.19 to 0.39 for 1-MN, 0.26 to 0.45 for 2-MN, and constant at 0.31 for 1,2-DMN. Under low-NOx conditions, the SOA yields were measured to be 0.73, 0.68, and 0.58, for naphthalene, 1-MN, and 2-MN, respectively. The SOA was observed to be semivolatile under high-NOx conditions and essentially nonvolatile under low-NOx conditions, owing to the higher fraction of ring-retaining products formed under low-NOx conditions. When applying these measured yields to estimate SOA formation from primary emissions of diesel engines and wood burning, PAHs are estimated to yield 3–5 times more SOA than light aromatic compounds. PAHs can also account for up to 54% of the total SOA from oxidation of diesel emissions, representing a potentially large source of urban SOA. Arthur Wing Hong Chan; Kathryn E. Kautzman; Puneet Singh Chhabra; Jason D. Surratt; Man N. Chan; John D. Crounse; Andreas Kürten; Paul O. Wennberg; Richard C. Flagan; John H. Seinfeld article http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/6542 Thu, 14 May 2009 12:42:24 +0200