Determination of Secondary Organic Aerosol Formation from Cyanobacterial Harmful Algal Blooms

SAMANTHA BELL, Haley Plaas, Graham Smith, Nicolas A. Buchenau, Andrew P. Ault, Jason Surratt, University of North Carolina at Chapel Hill

     Abstract Number: 359
     Working Group: Aerosol Processes and Properties in Changing Environments in the Anthropocene

Abstract
Cyanobacterial harmful algal blooms (CHABs), known for their blue-green color, foul taste and odor, and toxicity in freshwater systems, are due to increased water temperature and increased nutrient-dense run off. Living near CHABs can cause adverse respiratory illnesses; yet mostly primary organic aerosol (POA) mechanisms have been examined. Volatile organic compounds (VOCs) are also emitted from CHABs, which contribute to the taste and odor of the water. VOCs emitted during these CHAB events could undergo atmospheric oxidation, and thus, have the potential to form secondary organic aerosol (SOA), a main component to PM2.5. Our preliminary work demonstrated that geosmin and 2-methylisoborneol, two abundant VOCs emitted during CHAB events, can be oxidized via hydroxyl radicals (·OH) by hydrogen atom abstraction to yield SOA. The main blue-green photosynthetic pigment of cyanobacteria produces volatile b-ionone and b-cyclocitral when oxidized. b-ionone and b-cyclocitral have a greater potential to undergo daytime oxidation via ·OH due to the presence of pi electrons and more reactive functional groups. Their oxidation mechanisms and transformation products need to be chemically characterized to understand if they can form SOA. A potential aerosol mass-oxidation flow reactor was systematically used to photochemically oxidize both VOCs, and the subsequent SOA particles were collected onto Teflon filters. A scanning electrical mobility sizer (SEMS) measured real-time aerosol size distributions during SOA formation. SOA were extracted and chemically analyzed by using reverse-phase liquid chromatography (RPLC) coupled to cyclic ion mobility spectrometry (cIMS) and interfaced with electrospray ionization high-resolution tandem mass spectrometry (ESI-HR-MS/MS). PM2.5 samples were collected along the Chowan River in North Carolina during an active CHAB to determine the presence of lab-measured transformation products.