Source Apportionment of Urban Volatile Organic Compounds Measured via PTR-ToF-MS and HR-ToF-CIMS during the COVID-19 Pandemic in Atlanta, Georgia

Abstract:

Volatile organic compounds (VOCs) impact tropospheric oxidation capacity, ozone production, and secondary organic aerosol formation, thus affecting the environment and human health. Anthropogenic VOC emissions have changed in recent decades as emissions from mobile sources have decreased, leaving large uncertainties in the sources and speciation of reactive organic carbon in urban environments. The coronavirus disease 2019 (COVID-19) pandemic provides a test point for VOC source apportionment as anthropogenic activities slowed, and then gradually increased as cities reopened. We measured ambient VOCs and oxidized VOCs using proton-transfer-reaction with time-of-flight mass spectrometer (PTR-ToF-MS) and gaseous phase measurements using a high resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) using iodide-adducts at an urban site in Atlanta, Georgia. Our observations began in May 2020, and are continuing at the point of abstract submission. Atlanta is a particularly interesting study site due to the prevalence of biogenic emissions in its urban setting, and an observed steady resurgence of anthropogenic activities comparable to levels prior to the COVID-19 pandemic, providing a wide range of emissions scenarios in a short period of time. We will present source apportionment analyses performed using non-negative matrix factorization (NNMF). We will evaluate the variance of key VOC species to identify major source factors from both biogenic and anthropogenic activities, examine temporal patterns from these identified sources, and analyze the impact of the COVID-19 pandemic on atmospheric VOC composition through comparison with emission inventories.