Plant Stress in a Changing Environment and Its Impacts on Future Climate: The Effects of Simulated Herbivory on Biogenic Secondary Organic Aerosol

The largest global source of volatile organic compounds (VOCs) in the atmosphere are from biogenic emissions. 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 could 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 0.3 m³ biogenic chamber. Herbivory was simulated via exogenous application of methyl jasmonate, an herbivory proxy. 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. The evolution of gas-phase species and particle characteristics were monitored over the following eight hours. Gas-phase species were measured with a gas chromatograph coupled to a mass spectrometer and flame ionization detector (GC-MS-FID). Particle size distribution, chemical composition, and hygroscopic properties were measured with a scanning mobility particle sizer (SMPS), high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and cloud condensation nuclei counter (CCNc) respectively. Experiments were repeated under baseline and stressed conditions for three different plant types. A comparison of the BVOC emissions and resultant SOA characteristics under baseline and stressed conditions will be presented.