Size and composition resolved aerosol fluxes above a pine forest and their response to biogenic chemistry
2 University of Colorado / CIRES, Boulder, CO, USA
3 Chemistry Department, Sacramento State University, CA, USA
4 National Risk Management Laboratory, USEPA, NC, USA
5 University of Colorado / CIRES, Boulder, CO, U.S.A.
6 Atmospheric Chemistry Division, NCAR, CO, USA
7 Air Quality Reserach Division, Environment Canada, Toronto, Canada
O 1.3 in Heterogeneous Photochemical Processes and Aerosols
05.10.2009, 16:00-16:25, Kutschenhaus
Fluxes of aerosols were measured above a loblolly pine plantation at Duke Forest, North Carolina, during the CELTIC campaign (Chemical Emission, Loss, Transformation, and Interactions with Canopies). Measurements were made by eddy covariance for total number fluxes (using two condensation particle counters with different cut-offs), size-segregated particle fluxes (using an optical particle spectrometer) and for individual sub-micron aerosol components by aerosol mass spectrometry (AMS). The fluxes of particle numbers, sulphate and organic components show bi-directional behaviour with consistent diurnal patterns, while nitrate was always deposited. The reasons for the bi-directional behaviour are discussed, and the measurements are used to estimate particle growth rates due to vapour uptake that would be consistent with the observations. Aerosol measurements are integrated with measurements of biogenic volatile organic compounds (BVOCs) at different scales (branch emissions, in-canopy gradients and canopy scale fluxes). The measurements demonstrate that organic emissions during midday are linked to the peak in plant emissions and photo-chemistry, and point to a yet unidentified source of reactive sulphur compounds in the forest canopy.
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