HR: 0800h
AN: A51B-0060    [Abstracts]
TI: Seasonal OVOC fluxes from an agricultural field planted with sugar beet
AU: Custer, T G
EM: thomascuster2000@yahoo.com
AF: Institute of Environmental Physics, University of Bremen Otto-Hahn-Allee 1, Bremen, 28359 Germany
AU: * Schade, G W
EM: schade@ariel.met.tamu.edu
AF: Institute of Environmental Physics, University of Bremen Otto-Hahn-Allee 1, Bremen, 28359 Germany
AU: * Schade, G W
EM: schade@ariel.met.tamu.edu
AF: Department of Atmospheric Sciences, Texas A&M University 3150 TAMU, College Station, TX 77843 United States
AB: Although agricultural crops are generally not strong isoprenoid emitters, they do emit a variety of other atmospherically significant species collectively known as oxygenated VOCs (OVOCs), such as methanol, acetaldehyde, or various hexenal and hexenol compounds. Many OVOCs have longer atmospheric lifetimes than isoprenoid compounds and can affect the atmosphere's oxidative potential at higher elevations and far from sources. We performed selected OVOC flux measurements for select species above an agricultural field planted with sugar beets ( B. vulgaris) in northern Germany in 2004 to better understand the magnitude and controls over these OVOC emissions. Virtual disjunct eddy covariance was used to measure fluxes beginning immediately following seeding and continuing until past harvest. A commercial PTR-MS provided mixing ratios of methanol (m/z 33), acetaldehyde (m/z 45), acetone (m/z 59), and the sum of the isoprene oxidation products methacrolein and methyl vinyl ketone (m/z 71) while 3D wind velocities were measured using a Gill R3 sonic anemometer. Here, we compare the fluxes of methanol and acetone over the growth cycle of sugar beet to plant development as measured by the leaf area index. Methanol fluxes ranged from approximately -0.05 to 0.15 mg C m^-2 h^-1 (mixing ratios from ~1 to 15 ppbv) and showed a clear diurnal cycle after the sugar beets established a significant leaf area. Acetone fluxes ranged from approximately -0.2 to 0.2 mg C m^-2 h^-1 (mixing ratios from ~0.2 to 3 ppb). Higher specific emissions were found during earlier growth stages. Methanol flux correlated strongly with latent heat flux (or alternatively, with canopy conductance derived from the latent heat flux), while acetone flux did not. Acetone flux was small compared to methanol flux and sugar beet is likely not a significant acetone emitter. Weekly measurements of soil OVOC exchange using a flux chamber showed that the soil may have contributed significantly to the overall flux values both as a source and a sink.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0322 Constituent sources and sinks
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005