Measurements of BVOC fluxes Above Mixed Hardwood Forest Canopy During the 2009 CABINEX Field Campaign

Biological volatile organic compounds (BVOCs) such as isoprene and monoterpenes are emitted in large amounts from North American forests. Quantification of the flux of (BVOCs) is therefore critical in the evaluation of the impact of these compounds on the concentration of oxidants and on the production of secondary organic aerosol. A disjunct eddy accumulation (DEA) sampler system has been constructed for the measurement of BVOC fluxes. Unlike the traditional relaxed eddy accumulation (REA) and eddy covariance (EC) systems which measure continuously, the relatively new technique of disjunct sampling differs by taking short, separate samples. Ambient airflow is directed into cartridges containing sorbant materials at sampling rates proportional to the magnitude of the vertical wind. The cartridges are changed after a suitable accumulation period. Compounds accumulated on the cartridges can then be quantified by thermal desorption of the BVOCs into a gas chromatograph. Data presented will describe laboratory tests to validate the disjunct sampling procedure as well as the magnitude of fluxes of isoprene and monoterpenes from mixed hardwood forest at the University of Michigan Biological Station (Pellston, MI) during the 2009 CABINEX field campaign.