Increasing Contributions of Temperature-Dependent Oxygenated Organic Aerosol to Summertime Particulate Matter in New York City

TORI HASS-MITCHELL, Mitchell Rogers, Taekyu Joo, Benjamin A. Nault, Catelynn Soong, Mia Tran, Minguk Seo, Jo Machesky, Manjula Canagaratna, Joseph Roscioli, Nga Lee Ng, Ann Dillner, Roya Bahreini, Armistead G. Russell, Jordan Krechmer, Andrew Lambe, Drew Gentner, Yale University

     Abstract Number: 418
     Working Group: Urban Aerosols

Abstract
As part of the summer 2022 NYC-METS (New York City metropolitan Measurements of Emissions and TransformationS) campaign and the ASCENT (Atmospheric Science and Chemistry mEasurement NeTwork) observational network, ambient concentrations of organic, nitrate, sulfate, ammonium, chloride, and black carbon particulate matter (PM) were measured in Manhattan and Queens, NYC, along with a range of supporting gas-phase measurements. Due to steady reductions in inorganic aerosol concentrations during the 21^st century, summertime aerosol composition in NYC was predominantly organic (79-81%). Positive matrix factorization (PMF) source apportionment analysis shows major contributions from oxygenated organic aerosol (OOA) (73-76%), which is typically associated with secondary OA (SOA). The concentration and oxidation level of OOA source factors increased as a function of ambient temperature, including during a heatwave event in the measurement intensive period. The average ratio of total OOA to sulfate (5.8) was 4.5 times higher than previous observations. Additional primary source factors include hydrocarbon-like and cooking-related organic aerosols, which are comparatively less influenced by temperature and represent 10% and 14% of OA, respectively. The limited reductions in OA concentrations over recent years and the temperature-sensitivity of OOA source factors highlights the importance of a changing climate on summertime air quality in NYC given the established health impacts of SOA. Elevated temperatures, as well as extreme heat events, are likely to play an increasingly significant role in both the magnitude and composition of PM in NYC and similar east coast cities in the future. Therefore, greater attention to temperature-sensitive sources, emissions pathways, and associated chemical processing is required to make continued reductions in summertime PM in NYC and downwind areas.