The Effects of Simulated Herbivory on Biogenic VOC Emissions and Secondary Organic Aerosol Formation

Biogenic emissions are the largest global source of volatile organic compounds (VOCs) in the atmosphere. These VOCs are one of the principal factors influencing the oxidative capacity of the atmosphere in forested regions, and impact both ozone concentration and secondary organic aerosol (SOA) formation. Emission rates of biogenic VOCs are predominantly controlled by temperature. However, plant stressors associated with a changing environment can alter both the quantity and composition of the compounds that are emitted. Alterations to the biogenic VOC profile may impact the characteristics of the SOA formed from those emissions. This study investigated the effects of one global change stressor, increased herbivory, on the characteristics of SOA derived from real plant emissions. Plants were housed in the laboratory within a 0.7 m3 biogenic chamber. Herbivory was simulated via exogenous application of a proxy compound, methyl jasmonate. Plant emissions were transported from the biogenic chamber to a 7 m3 FEP Teflon aerosol growth chamber, where they were oxidized with ozone in the absence of light. Experiments were repeated under baseline and stressed conditions for several different plant types. Results indicate that trees varied significantly in both their emissions and their response to the simulated herbivory stress. These differences led to variability in the amount of SOA produced, and, to a less degree, in the SOA composition. A comparison of the BVOC emissions and resultant SOA characteristics under baseline and stressed conditions will be presented.