HR: 09:30h
AN: A21A-07    [PDF]
TI: Turbulent Exchange of Particulate Matter During BEWA2000
AU: * Held, A
EM: andreas.held@uni-muenster.de
AF: University of Muenster, Robert-Koch-Str. 26, Muenster, 48149 Germany
AU: Brggemann, E
EM: erika@tropos.de
AF: Institute for Tropospheric Research, Permoserstr. 15, Leipzig, 04318 Germany
AU: Wiedensohler, A
EM: ali@tropos.de
AF: Institute for Tropospheric Research, Permoserstr. 15, Leipzig, 04318 Germany
AU: Klemm, O
EM: oklemm@uni-muenster.de
AF: University of Muenster, Robert-Koch-Str. 26, Muenster, 48149 Germany
AB: During BEWA2000, two field campaigns were conducted in the "Fichtelgebirge" mountains, NE-Bavaria, Germany, to study biogenic emissions of volatile organic compounds from a "Norway Spruce" forest. BVOC oxidation products may contribute to particulate mass through condensation on existing particles or new particle formation. Measurements of particulate mass, particle size distributions and vertical particle fluxes were jointly analyzed and interpreted. The particle number flux system included a sonic anemometer and two condensation particle counters. Particle size distributions were measured with a differential mobility particle sizer at the same height as the flux system at 22 m agl. Also, particle number concentrations were measured within the forest stand. Particle mass was obtained from impactor and high-volume sampler measurements. Particle numbers differed considerably within and above the forest. The in-canopy concentration ranged from 60 % to 100 % of the concentration above the canopy. A diurnal pattern with effective particle production in the canopy through turbulent mixing and/or particle formation in the morning and effective particle removal in the canopy through deposition and/or coagulation processes in the afternoon was found. An important conclusion from these findings is that not only particle concentrations but also particle size distributions may differ within and above the forest. Turbulent particle number fluxes exhibited a diurnal pattern with small fluxes in the night and large fluxes during daytime. In general, particle deposition dominated over emission. A characteristic "banana-shaped" development of the particle size distribution indicating formation of particulate matter and subsequent growth was found on several days. Strong deposition fluxes occurred during these events. Particle mass fluxes may be determined from a combination of size distribution measurements and size-resolved deposition models. The mass determined from size distributions agrees well with directly measured particle mass. However, the uncertainty of calculated mass fluxes remains large. Funding by the German federal research ministry through grants PT BEO 51-0339476C and PT UKF 07ATF25 is gratefully acknowledged.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting