Suchergebnisse

Secondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks. ; Research at the University of Cambridge was supported by a Marie Curie Intra-European fellowship (project no. 254319) and the ERC grant no. 279405. We thank the SAPHIR and TNA2012 team in Jülich for supporting our measurements and the support by EUROCHAMP2 contract no. 228335. The field-work was funded by ERC grant 227463 and the Academy of Finland Centre of Excellence (grants 1118615 and 272041) and by the Office of Science (BER), US Department of Energy via Biogenic Aerosols - Effects on Clouds and Climate (BAECC). European Union's Horizon 2020 research and innovation programme under grant agreement no. 654109 and previously from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262254. We thank the Met Office for use of the NAME model. S.C. thanks the UK Natural Environment Research Council for her studentship.

Kolb, C. E. Cox, R. A. Abbatt, J. P. D. Ammann, M. Davis, E. J. Donaldson, D. J. Garrett, B. C. George, C. Griffiths, P. T. Hanson, D. R. Kulmala, M. McFiggans, G. Poeschl, U. Riipinen, I. Rossi, M. J. Rudich, Y. Wagner, P. E. Winkler, P. M. Worsnop, D. R. O' Dowd, C. D. ; International audience A workshop was held in the framework of the ACCENT (Atmospheric Composition Change - a European Network) Joint Research Programme on "Aerosols" and the Programme on "Access to Laboratory Data". The aim of the workshop was to hold "Gordon Conference" type discussion covering accommodation and reactive uptake of water vapour and trace pollutant gases on condensed phase atmospheric materials. The scope was to review and define the current state of knowledge of accommodation coefficients for water vapour on water droplet and ice surfaces, and uptake of trace gas species on a variety of different surfaces characteristic of the atmospheric condensed phase particulate matter and cloud droplets. Twenty-six scientists participated in this meeting through presentations, discussions and the development of a consensus review. In this review we present an analysis of the state of knowledge on the thermal and mass accommodation coefficient for water vapour on aqueous droplets and ice and a survey of current state-of the-art of reactive uptake of trace gases on a range of liquid and solid atmospheric droplets and particles. The review recommends consistent definitions of the various parameters that are needed for quantitative representation of the range of gas/condensed surface kinetic processes important for the atmosphere and identifies topics that require additional research.