HR: 1340h
AN: B23A-0949    [Abstracts]
TI: Mapping Regional Patterns of Fossils Fuel CO$_{2}$ in the Planetary Boundary Layer Across North America Using Radiocarbon in Annual Plants
AU: * Hsueh, D Y
EM: dhsueh@uci.edu
AF: University of California, Irvine; Deptartment of Earth System Science, 3212 Croul Hall, Irvine, CA 92697
AU: Randerson, J T
EM: jranders@uci.edu
AF: University of California, Irvine; Deptartment of Earth System Science, 3212 Croul Hall, Irvine, CA 92697
AU: Southon, J R
EM: jsouthon@uci.edu
AF: University of California, Irvine; Deptartment of Earth System Science, 3212 Croul Hall, Irvine, CA 92697
AU: Trumbore, S E
EM: setrumbo@uci.edu
AF: University of California, Irvine; Deptartment of Earth System Science, 3212 Croul Hall, Irvine, CA 92697
AB: Radiocarbon levels in annual plants provide a means to map out regional and continental-scale patterns of fossil fuel emissions and biosphere-atmosphere exchange. The imprint of the local atmosphere is recorded within the leaves of these annual plants and represents a time-integral of atmospheric levels over a period of several months, complementing both flask and aircraft sampling techniques. Working with colleagues, we collected corn (Zea mays) from approximately 70 sites across North America. We designed a sampling protocol that captured regional and continental scale patterns of fossil fuel CO$_{2}$ levels; we specifically avoided areas directly influenced by point sources such as major roads or cities. We then analyzed the leaves in the W.M. Keck Carbon Cycle Accelerator Mass Spectrometer at the University of California, Irvine. In areas where the corn plants were exposed to sustained and elevated levels of CO$_{2}$ from fossil fuel emissions, such as the Ohio Valley, the $^{14}$C/$^{12}$C ratio of the corn leaves was reduced. We found that there was a drop of approximately 15 per mil between the western U.S. (Alberta, Idaho, Colorado and New Mexico) and the Northeastern U.S. (Ohio, Maryland and Pennsylvania). This corresponds to approximately 5 ppm increase in fossil fuel CO$_{2}$ levels, as air moves from west to east across the continent. These data provide a means to test our understanding of the coupling of biosphere atmosphere exchange, planetary boundary layer mixing, atmospheric transport, and fossil fuel emissions in mesoscale and global models that are used to estimate the spatial distribution of carbon sources and sinks.
DE: 4805 Biogeochemical cycles (1615)
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting