Concentration of Terpenoid Oxidation Products in Aerosol in the Southeastern U.S. and the Role of Different BVOC Classes

GRAHAM FRAZIER, Gabriel Isaacman-VanWertz, Virginia Tech

     Abstract Number: 179
     Working Group: Remote and Regional Atmospheric Aerosol

Abstract
Biogenic volatile organic compounds (BVOC) represent the primary source of reactive carbon in the atmosphere and contribute to formation of secondary organic aerosol (SOA) through atmospheric oxidants including ozone and hydroxyl radicals. One class of BVOC, sesquiterpenes, have higher reaction rates with ozone compared to other BVOC species and higher SOA yields. However, these and other higher molecular weight chemical classes exist at low concentrations relative to other BVOCs, so their contribution to aerosol formation remains uncertain. While some modelling predicts sesquiterpenes contribute substantially to SOA, several sampling campaigns have observed low concentrations of sesquiterpenes and have suggested that SOA in BVOC-rich locations can be explained without significant contributions from sesquiterpenes. The central uncertainty is therefore whether low concentrations are due to sesquiterpenes being emitted at high rates and reacting quickly with atmospheric oxidants, which would contribute significantly to SOA, or whether emissions of sesquiterpenes are simply insufficient to contribute substantially to SOA formation. To rectify this knowledge gap, we present data from several field deployments to quantify terpenoid oxidation products and provide insight into the importance of sesquiterpenes in comparison to other BVOC classes with regards to their contribution to aerosol. The composition of organic aerosol and aerosol-forming gases were measured by a semi-volatile thermal desorption aerosol gas chromatography (SV-TAG) at several sites in Virginia to provide a representation of different ecosystems in the Southeastern US. This work focuses on presenting concentrations of oxidation products from a variety of terpene classes and seeks to provide constraints on the observed contribution of sesquiterpene oxidation products to aerosol mass.