HR: 10:35h
AN: A42B-02    [Abstracts]
TI: Hg(II) Sources, Sinks, and Reactions with Halogens in the Remote Atmospheric Marine Boundary Layer
AU: * Holmes, C D
EM: holmes2@fas.harvard.edu
AF: Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, United States
AU: Jacob, D J
EM: djj@io.as.harvard.edu
AF: Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, United States
AU: Mason, R P
EM: robert.mason@uconn.edu
AF: Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, CT 06340, United States
AU: Jaffe, D
EM: djaffe@u.washington.edu
AF: Interdisciplinary Arts and Sciences Department, University of Washington, Bothell, 18115 Campus Way NE, Bothell, WA 98011, United States
AB: We investigate the chemistry and sinks of reactive gaseous mercury (RGM) in the remote marine boundary layer, using a box model to interpret observations from the Atlantic and Pacific Oceans and from a coastal site in Okinawa. The diurnal cycles of RGM at all sites have morning increases that we show are quantitatively consistent with RGM production primarily from the oxidation of Hg⁰ by atomic halogens. Atomic bromine may generate the midday peak in RGM and could be the major daytime oxidant of Hg⁰, while atomic Cl could play a secondary role in the morning. Because RGM concentrations fall rapidly in the afternoon but persist above detection limit at night, we posit a photosensitive sink for RGM, possibly involving reduced sulfur species in marine aerosol. Alternately or in addition, a nocturnal oxidant, such as NO₃, could supply detectable amounts of RGM at night. We find much larger amplitude diurnal cycles over tropical and sub-tropical oceans compared with the extra-tropics. The tropical enhancement of RGM concentration occurs in areas with little chlorophyll A, but where previous studies found significant biogenic halocarbon emissions.
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0322 Constituent sources and sinks
DE: 0330 Geochemical cycles (1030)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting