Multiphase Oxidative Molecular-Level Transformations of Sea Spray Aerosol and Plastics Studied by Extractive Electrospray Ionization High-Resolution Time-of-Flight Mass Spectrometry

With rapid and continued population growth in coastal urban environments, humans have an increasingly measurable impact on atmospheric and water chemistry in those areas. Plastic waste, and the interaction of gaseous pollutants (NO x , O 3 , and ·OH) with marine-derived aerosol and gases, modulate the composition and quality of coastal marine boundary layer air. In this work, as part of the Sea Spray Chemistry and Particle Evolution (SeaSCAPE) 2019 study with the NSF Center for Aerosol Impacts on Chemistry of the Environment, we report on the molecular-level transformations of nascent sea spray aerosol (nSSA) from multiphase ·OH oxidation in the presence of marine-derived gases generated during phytoplankton blooms in a laboratory mesocosm with controlled wave breaking. We utilize an extractive electrospray ionization high-resolution time-of-flight mass spectrometer (EESI-HR-ToF-MS) to study the evolving molecular composition of the extractable components of nSSA as a function of phytoplankton bloom age, relative humidity, and ·OH exposure. Preliminary results indicate that with increasing ·OH exposure in the presence of marine-derived gases, the weighted-average particle molar mass of nSSA increases concurrently with the presence of iodine-containing molecular clusters in the aerosol phase. This work contributes to better understanding of the fundamental processes affecting the age and growth of SSA following emission from the ocean surface. In addition, laboratory studies are underway which will report on the ·OH-mediated and photochemical degradation kinetics of the persistent toxic plastic additive, Bisphenol-A (BPA), which has been found ubiquitously in ocean water, and more recently in aerosols over both terrestrial and marine environments across the globe. Here, a moveable injector flow tube reactor and potential aerosol mass oxidation flow reactor are used to study the uptake kinetics of ·OH and the photo-initiated degradation of BPA in the presence and absence of representative marine chromophoric dissolved organic material (m-cDOM). This work ultimately contributes to a growing understanding of the processes affecting the emission and degradation of toxic plastic additives in the environment and specifically will help guide future atmospheric risk assessment models of BPA.