Analytical Chemistry Seminar: William C. Keene

Analytical & Environmental Chemistry Division and Atmospheric Chemistry Program Seminar

Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program

Marine Aerosol Production, Chemical Processing, and Feedbacks

by William C. Keene - Department of Environmental Sciences, University of Virginia, Charlottesville, VA

Production of primary marine aerosol (PMA) by breaking waves on the ocean surface is a major global source of aerosol mass and number with important implications for biogeochemical cycles and climate. However, factors that modulate PMA production and composition are highly uncertain rendering model parameterizations and simulated impacts poorly constrained. PMA were produced by bursting bubbles from both flowing and fixed volumes of fresh surface seawater under controlled conditions in a high-capacity shipboard generator deployed in the eastern North Pacific Ocean during CalNex and in the western North Atlantic Ocean during the Western Atlantic Climate Study (WACS). Seawater ranged from highly productive (chl a = 12 μg L-1) to oligotrophic (chl a = 0.03 μg L-1). PMA were also produced from fresh flowing seawater sampled at 2505 m depth in which recalcitrant dissolved organic carbon (RDOC) accounts for virtually all organic matter (OM). Bubble sizes, bubble surface tension, and size-resolved aerosol number production fluxes and chemical compositions were quantified. Number fluxes were dominated by particles less than 100-nm dry diameter that were composed primarily of OM. Number fluxes from productive waters during daytime were greater by factors of ~2 relative to those at night and those from oligotrophic waters but corresponding organic enrichments (EFocs) relative to seawater were similar. Bubble scavenging from fixed-volume reservoirs of productive waters rapidly depleted dominant but small pools of surfactants leading to lower number production fluxes that converged towards those for oligotrophic waters. Bubble scavenging from fixed-volume oligotrophic waters had no influence on PMA fluxes suggesting the presence of a large background pool of surfactants. Number production fluxes and EFocs from flowing deep seawater were within the ranges of those from surface waters indicating that RDOC in the surface ocean may contribute to PMA OM emitted to the atmosphere. Subsequent photochemical oxidation of PMA OM corresponds to a potentially important and hitherto unknown removal mechanism for RDOC in the ocean and source for organic reaction products in marine air.

NOTICE:  Since the seminar will held in the CIRES Auditorium, no refreshments will be served.