AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Secondary Organic Aerosol Formation from Healthy and Aphid-Stressed Scots Pine Emissions
CELIA FAIOLA, Iida Pullinen, Angela Buchholz, Fatemeh Khalaj, Arttu Ylisirniö, Eetu Kari, Pasi Miettinen, Jarmo Holopainen, Minna Kivimäenpää, Siegfried Schobesberger, Taina Yli-Juuti, Annele Virtanen, University of California, Irvine
Abstract Number: 556 Working Group: Aerosol Chemistry
Abstract One barrier to predicting biogenic secondary organic aerosol (SOA) formation in a changing climate can be attributed to the complex nature of plant volatile emissions. Plant volatile emissions are dynamic over space and time, and change in response to environmental stressors. Emission rates and volatile composition are expected to evolve as the climate changes and causes plants to experience an increased level of stress. One important plant stressor in a warming boreal forest environment is insect herbivory as insect outbreaks increase in frequency and intensity. This study investigated SOA production from emissions of healthy and aphid-stressed Scots pine saplings via dark ozonolysis and photooxidation chemistry. Plant volatiles were transported to a batch reaction chamber where oxidation products and SOA production were monitored for a minimum of seven hours with the following instrumentation: PTR-ToF-MS, acetate-CIMS, aerosol mass spectrometer, and scanning mobility particle sizer. The initial volatile mixture in the chamber was characterized via cartridge sampling and off-line analysis on a thermo-desorption gas chromatograph mass spectrometer (TD-GC-MS). The initial volatile mixture from healthy plants included monoterpenes, aromatics, and a small amount of sesquiterpenes. The biggest change in the volatile mixture for aphid-stressed plants was a large increase in sesquiterpene emissions—particularly acyclic sesquiterpenes, such as the farnesene isomers. Oxidation products measured with an acetate-CIMS will be presented with estimated volatility distributions. Potential mechanisms accounting for changes in SOA mass yield between different chemical mechanisms and healthy vs. stressed plant volatile mixtures will be discussed.