HR: 17:45h
AN: A54C-08    [Abstracts]
TI: Oceanic Uptake and the Global Atmospheric Acetone Budget
AU: * Marandino, C A
EM: cmarandi@uci.edu
AF: University of California, Irvine, Department of Earth System Science 2103 Croul Hall, Irvine, CA 92697 United States
AU: DeBruyn, W J
EM: debruyn@chapman.edu
AF: Chapman University, Department of Physical Sciences One University Dr., Orange, CA 92866 United States
AU: Miller, S D
EM: sdmiller@uci.edu
AF: University of California, Irvine, Department of Earth System Science 2103 Croul Hall, Irvine, CA 92697 United States
AU: Prather, M J
EM: mprather@uci.edu
AF: University of California, Irvine, Department of Earth System Science 2103 Croul Hall, Irvine, CA 92697 United States
AU: Saltzman, E S
EM: esaltzma@uci.edu
AF: University of California, Irvine, Department of Earth System Science 2103 Croul Hall, Irvine, CA 92697 United States
AB: Acetone and other carbonyl compounds are believed to play a significant role in upper tropospheric chemistry as a precursor of OH and ozone. The oceans are thought to play a significant role in the global atmospheric acetone budget, but neither the sign nor the magnitude of the air/sea flux are well established. Little is known about the oceanic distribution of acetone or factors controlling its air/sea flux. In this study we report shipboard measurements of acetone air/seawater concentrations, and direct air/sea fluxes determined by eddy correlation with chemical ionization mass spectrometry. The measurements were conducted during the PHASE-1 cruise in the North Pacific aboard the R/V Wecoma between May and July, 2004. The mean acetone concentrations in near surface seawater (approx. 5 m depth) were 14.5 - 12.7 nM and 12.1 - 3.0 nM, in the equatorial and North Pacific, respectively. Acetone levels in air ranged from 270 ppt in the equatorial region to 1.4 ppb in the northern mid-latitudes. The direct flux measurements indicated a net flux of acetone into the oceans, with average fluxes of ~1.5 and ~13.6 mmol m-2 day-1 in the two regions. The direct flux measurements were not consistent with fluxes inferred from the air/sea concentration gradient. This inconsistency may reflect near surface gradients in the oceanic acetone concentration. A global extrapolation of the measured air/sea acetone fluxes yields an ocean uptake of 48 Tg yr-1, roughly 47% of the global annual sink. This large global sink is consistent with estimates based on atmospheric gradients observed over the Pacific Ocean. These results, and the recent downward reevaluation of acetone photodissociation quantum yields (Blitz et al, 2004), suggests that oceanic uptake considerably larger than previously thought, and is roughly comparable on a global basis to atmospheric losses via photolysis and reaction with OH.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0330 Geochemical cycles (1030)
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005