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Viscosity and Chemical Composition of Secondary Organic Aerosol from Real Healthy and Stressed Canary Island Pine Trees
NATALIE R. SMITH, Giuseppe Crescenzo, Anusha P.S. Hettiyadura, Kyla Siemens, Ying Li, Celia Faiola, Alexander Laskin, Manabu Shiraiwa, Allan Bertram, Sergey Nizkorodov, University of California, Irvine
Abstract Number: 24
Working Group: Aerosol Chemistry
Abstract
When plants are stressed, their volatile organic compound (VOC) emission profile changes in both quantity and types of compounds being emitted. For example, pine trees stressed due to aphid herbivory emit more sesquiterpenes, which can lead to the formation of secondary organic aerosols (SOA) with different properties when compared to SOA resulting from healthy plant emissions. The chemical composition of SOA determines particle viscosity, which in turn can impact photochemical aging of particles, their ability to act as cloud condensation and ice nuclei, and lifetimes of particulate pollutants in the atmosphere. In our previous study (in press), we showed that SOA from synthetic mixtures of VOCs simulating stressed plant emissions results in more viscous particles than SOA from mixtures representing healthy plant emissions. In this study, the molecular composition and viscosity were investigated for SOA generated from real healthy or aphid-stressed Canary Island pine (Pinus canariensis) trees, which are commonly used in landscaping. Aerosols were generated in a 5 m3 environmental chamber at 50% relative humidity. Detailed information on particle molecular composition was gained through high resolution mass spectrometry. The observed neutral molecular formulas were used to predict the viscosity as a function of relative humidity using the parameterization developed by DeRieux et al. (2018). At the time of writing the abstract, the actual viscosity of SOA particles has not been measured yet, but we hypothesize that stressed pine trees will produce more viscous aerosol particles. The predictions from the viscosity model will be compared to the experimental values measured via the poke-flow method. Comparison of viscosity and chemical composition for real healthy and stressed Canary Island pine SOA is novel, and it will advance our understanding of how tree stress influences physicochemical properties of SOA in an evolving environment.