AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
A Diversity and Distribution of Organic Aerosol Functional Groups across Multiple Sites and Seasons
JENNA DITTO, Taekyu Joo, Jonathan Slade, Paul Shepson, Nga Lee Ng, Drew Gentner, Yale University
Abstract Number: 370 Working Group: Aerosol Chemistry
Abstract Highly functionalized organic compounds are known to be a major component of secondary organic aerosol in urban, downwind, and remote environments. However, these complex mixtures of compounds are understudied at the molecular level, and the impact of changes in the molecular-level composition of aerosol mixtures on air quality is often poorly understood. Characterizing the functional group distribution of organic aerosol (OA) can help constrain reaction pathways and products in the atmosphere, and ultimately improve our understanding of the health and environmental impacts of OA. Here, we leverage liquid chromatography with electrospray ionization and quadrupole time-of-flight tandem mass spectrometry (LC-ESI-MS/MS) to characterize the molecular-level elemental and structural characteristics of OA. A non-targeted screening of OA functional groups from a forest, from a major US city, and from aged urban outflow shows a diverse range of oxygen-, nitrogen, and sulfur-containing structures. We observe important contributions from hydroxyl groups (~25-30% relative prevalence), carboxylic acids (~5-20%), and esters (~7-10%), along with a range of other functional groups with smaller but persistent contributions across ambient locations, including amines, organonitrates, and organosulfates. We compare the structural features present in functionalized OA across time of day, season, and location. Urban summertime data show a greater proportion of hydroxyl groups, carboxylic acids, carbonyls, and non-aromatic rings relative to the winter, while we observe an increased proportion of amines and aromatic rings at the same site in winter. Comparing urban and aged urban outflow functional group distributions, we observe an increased contribution from carboxylic acids, carbonyls, and amines at the urban site, and an increased contribution of esters in urban outflow. Finally, we use these results to identify key characteristics of OA functional group distribution and associated implications for OA properties and impacts.