Analytical Chemistry Seminar
Analytical & Environmental Chemistry Division and Atmospheric Chemistry Program Seminar
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
UV Photochemistry of Carboxylic Acids at the Air-Sea Boundary: A Relevant Source of Glyoxal and other OVOC in the Marine Atmosphere
by Randall Chiu - Analytical division 3rd year student, Department of Chemistry and Biochemistry, and CIRES; University of Colorado Boulder
Photochemistry plays an important role in marine dissolved organic carbon (DOC) degradation, but the mechanisms that convert DOC into volatile organic compounds (VOCs) remain poorly understood. We irradiated carboxylic acids (C7-C9) on a simulated ocean surface with UV light (<320 nm) in a photochemical flow reactor, and transferred the VOC products into a dark ozone reactor. Glyoxal was detected as a secondary product from heptanoic, octanoic, and NA films, but not from octanol. Primary glyoxal emissions were not observed, nor was glyoxal formed in the absence of ozone. Addition of a photosensitizer had no noticeable effect. The concurrent detection of heptanal in the NA system suggests that the ozonolysis of 2-nonenal is the primary chemical mechanism that produces glyoxal. This source can potentially sustain few 10 pptv glyoxal over oceans, and helps to explain why glyoxal fluxes in marine air are directed from the atmosphere into the ocean.