Abstract View
On the Effects of Wet vs. Dry and Seeded vs. Unseeded Conditions on SOA Hygroscopicity
Patricia Razafindrambinina, Kotiba A. Malek, Joseph Dawson, Miriam Freedman, Akua Asa-Awuku, Tim Raymond, DABRINA DUTCHER, Bucknell University
Abstract Number: 422
Working Group: Aerosols, Clouds and Climate
Abstract
Volatile organic matter that are suspended in the atmosphere such as α-Pinene and trans-caryophyllene undergo the aging process, chemical, and photooxidation reactions to create secondary organic aerosols (SOA) that are thought to be viscous and inhibit water uptake. Currently, the influence of the indirect effect of SOA on the radiative budget is yet to be fully understood, and little is known of the impact of water vapor and ammonium sulfate (ubiquitous species in the atmosphere) presence on the hygroscopicity and CCN activity of SOA. In this research, three water-uptake measurement methods: cavity ring-down spectroscopy (CRDS), hygroscopic tandem differential mobility analysis (H-TDMA), and cloud condensation nuclei counting (CCNC) are employed to study the hygroscopicity of α-Pinene and trans-caryophyllene SOA formed under dark ozonolysis, and observe the changes in water uptake of SOA in the presence of water vapor at 76 % RH and ammonium sulfate seeds. Hygroscopicity was parameterized by the single hygroscopicity parameter (κ) and showed that water vapor and ammonium sulfate modify the water uptake behavior of α-Pinene SOA, but not trans-caryophyllene. It is proposed that a difference in the viscosity and hydrophobicity of the SOA may be the primary factor that leads to changes in hygroscopicity.