Synthesis of Oxidation Products from Biogenic Volatile Organic Compounds in the Atmosphere: A Review

SAHIR GAGAN, Kumar Sarang, Ruizhe Liu, Yue Zhang, Texas A&M University

     Abstract Number: 422
     Working Group: Aerosol Chemistry

Abstract
Volatile organic compounds (VOCs) emitted by plants, such as isoprene, terpenes (e.g., α-pinene and β-caryophyllene), and green leaf volatiles are large contributors to the total organic aerosol budget. VOCs undergo reactions with oxidants such as hydroxyl radical (·OH), nitrates (NO₃), ozone (O₃) followed by physical and multiphase processes to form secondary organic aerosols (SOA). Owing to the complex nature of reaction pathways, multiple intermediate species may form from one precursor at different stages of the reaction. Presently, to characterize these SOA precursors and components, a combination of various high resolution (HR) offline and online analytical techniques like gas chromatography-mass spectrometer (GC-MS), liquid chromatography-mass spectrometer (LC-MS), time of flight-aerosol mass spectrometer (ToF-AMS) are employed. Accurate identification and quantification of these compounds require authentic standards from organic synthesis, making it crucial in understanding the formation and the associated impacts of SOA on air quality, climate, and health.

In this review we have encompassed the progress made in the synthesis of authentic reference marker compounds for SOA originating from biogenic VOCs (BVOCs). Our review is a collection of synthetic procedures developed and reported till date, organized based on the order of appearances during the oxidation reactions of BVOC. We also group the target compound under various atmospheric conditions including of ozonolysis as well as high NOx and low NOx oxidations. This review also includes existing gaps between the current synthetic methods and missing key authentic standards, to further improve understandings in the reaction pathways of SOA formation.

This review is the first based on what we know to systematically summarize current known synthetic pathways of SOA standards from BVOCs oxidations. We hope that the review can further connect synthetic chemistry with atmospheric chemistry and provide the community with tools to identify and quantify key species during complicated reactions that lead to SOA formation.