Emissions and Photochemistry of BVOCs in a Ponderosa Pine woodland

We deployed two proton-transfer-reaction mass spectrometry instruments (PTR-MS, IONICON ANALYTIK) for ambient and branch enclosure measurements at the Manitou Experimental Forest, located in the Southern Rocky Mountain area as a part of the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen (BEACHON) field campaign in 2008. Vegetation at the field site is dominated by Ponderosa Pine. BVOC emissions from Ponderosa Pine along with temperature, photosynthetic photon flux density (ppfd), relative humidity, and CO2 uptake were measured from two branch-enclosures (shade and sun). Diurnal variations and the emission response to environmental conditions are described and compared to existing models. In addition, we analyzed the speciation of BVOCs from enclosures by GC-MS. We will present quantitative and qualitative characteristics of BVOC emissions from Ponderosa Pine and analytical characteristics of PTR-MS such as fragmentation patterns of semi-volatile compounds (sesquiterpene, bornyl acetate etc) that we identified as major emissions from the enclosures. BVOC emissions observed in the enclosures will be quantitatively compared to BVOC distributions in ambient air. We explore the presence of possibly unidentified BVOCs in the forest canopy by examining PTR-MS mass spectra of enclosure and ambient air samples based on mass scans between 40 - 210 amu.