HR: 1330h
AN: A52A-0771    [PDF]
TI: Isotopic Composition of Molecular Hydrogen Formed From the Photolysis of Formaldehyde in Sunlight
AU: * Crounse, J D
EM: crounjd@caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AU: Rahn, T
EM: trahn@lanl.gov
AF: Los Alamos National Laboratory, EES-6, MS-D462, Los Alamos, NM 87545 United States
AU: Wennberg, P O
EM: wennberg@caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AU: Eiler, J
EM: eiler@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AB: The main source of atmospheric H2 is through the photochemical oxidation of methane, with the immediate precursor being formaldehyde. The isotopic composition of atmospheric H2 can be used to place contraints on the sources and sinks of H2 as each process has a specific fractionation. We present measurements of D/H from H2 generated from the photolysis of formaldehyde, showing that this process produces isotopically light H2(dD(H2)$\sim$= -200 $\permil$). This result is consistant with estimates by Rahn, et.al, 2003 of the fractionation required by this process to account for the observed D/H in stratospheric H2. Implications of this finding for the tropospheric H2 Budget will be discussed.
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting