Velici Variation of Aerosol Concentration (2)


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REPORT SERIES IN AEROSOL SCIENCE N:o 46 (2000) VARIATION OF AEROSOL CONCENTRATION IN AMBIENT AIR GINTAUTAS BUZORIUS Department of Physics Faculty of Science University of Helsinki Helsinki, Finland Academic dissertation To be presented with permission of the Faculty of Science of the University of Helsinki, for public criticism in the main Auditorium of the Department of Physics, Siltavuorenpenger 20 D, May, 31-th, 2000, at 12 o’clock noon. Helsinki 2000 ISSN 0784-3496 ISBN 952-5027-22-8
  REPORT SERIES INAEROSOL SCIENCEN:o 46 (2000) VARIATION OF AEROSOL CONCENTRATIONIN AMBIENT AIR GINTAUTAS BUZORIUS Department of PhysicsFaculty of ScienceUniversity of HelsinkiHelsinki, Finland Academic dissertation To be presented with permission of the Faculty of Scienceof the University of Helsinki, for public criticism in the main Auditoriumof the Department of Physics, Siltavuorenpenger 20 D,May, 31-th, 2000, at 12 o’clock noon. Helsinki 2000  ISSN 0784-3496ISBN 952-5027-22-8 (nid.)ISBN 951-45-9428-2 (PDF version)Helsingin yliopiston verkkojulkaisutHelsinki 2000  1 Acknowledgements This thesis was based on research work done at the Laboratory of Aerosol andEnvironmental Physics at the University of Helsinki. I thank Prof. Juhani Keinonen, headof the Physics Department, for providing me the working facilities.I would like to thank to Prof. Markku Kulmala, Doc. Jyrki M. Mäkelä, Doc. Timo Vesalaand Doc. Kaarle Hämeri for their invaluable support and guidance during the studies inHelsinki. I also thank all the group members for the relaxed and supportive workingenvironment. I thank my friend and co-author Üllar Rannik for a friendship andcooperation. I highly appreciate the collaboration with the people from the SMEAR IIstation, especially Dr.Hc. Toivo Pohja for helping to construct and maintain themeasurement system what was used during the study.My best memories stay with the aikido club Seitokai members where I had a lot of funenjoying the practises. I thank all the friends, only few I mentioned here, whom I metduring my study years in Finland, and shared good time. I heartily thank to Mika TapioKleemola, Enzo Filomeno, Lasse Heikkanen and Meri Kukkavara for their invaluablefriendship and support.Finally I thank to my family for their support and caring during my years away inFinland.  2 Variation of aerosol concentration in ambient air Gintautas BuzoriusUniversity of Helsinki, 2000 Abstract Experimental studies on atmospheric aerosol have been increasing over the last decade,resulting in new findings about particle formation in the atmospheric surface layer and inmore intensive studies on public health effects in relation to aerosol numberconcentration. This work consists of experimental results concerning aerosol numberconcentration measured in urban and remote continental environment.Studies on the aerosol spatial variability in urban areas showed that 10 min averages of the number concentration can be highly correlated (> 0.8) between places located morethan 1 km apart from each other. It suggested that aerosol number concentration in thecity is spatially rather homogeneous and simultaneously varying in time at differentplaces.A Condensation Particle Counter was applied in an eddy correlation technique to measureparticle vertical fluxes. The method requires fast aerosol number concentration sampling.The CPC performance under high frequency sampling conditions was analysed underlaboratory conditions where time constant studies were determined as being from 0.8 to0.14 seconds, depending on the counter model. With the time resolution given by theCPC it is possible to measure most of the fluctuations in the number concentrationcontributing to the flux.The flux measurements showed a prevailing depositing flux and a pollution source atSouthwest direction at the field measurement site (Hyytiälä). Fluxes were affected byadvection. There are episodes of upward fluxes, which were confirmed by the particlegradient measurement. However these upward fluxes were associated with the localpollution and are not characteristic features of the forest as a source of particles. Keywords: turbulent flux, condensation particle counter, eddy covariance, spatial variation and depositionvelocity
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