HR: 10:35h
AN: H12D-02    [Abstracts]
TI: Monitoring Surface CO₂ Fluxes Associated with Shallow Subsurface CO₂ Release Experiments
AU: * Lewicki, J L
EM: jllewicki@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
AU: Fischer, M L
EM: mlfischer@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, United States
AU: Rahn, T A
EM: trahn@lanl.gov
AF: Los Alamos National Laboratory, MS D429, Los Alamos, NM 87545, United States
AU: Dobeck, L
EM: dobeck@chemistry.montana.edu
AF: Montana State University, 108 Gaines Hall PO Box 173400, Bozeman, MT 59717, United States
AU: Spangler, L
EM: spangler@montana.edu
AF: Montana State University, 108 Gaines Hall PO Box 173400, Bozeman, MT 59717, United States
AB: A new facility designed by the ZERT Project to release CO₂ into the shallow subsurface provides the opportunity to test field methods to detect and quantify potential CO₂ leakage from geologic storage sites. CO₂ release experiments were conducted in an agricultural field at Montana State University, in Bozeman, MT, where a ~100-m long horizontal well was installed at ~2.5 m depth, sub-water table, within a sandy gravel. The well was divided into zones separated by inflatable packers, from which 0.1 t CO₂ d^{- 1} was released from 07/09/2007 to 07/19/2007 (Release 1), and 0.3 t CO₂ d^-1 was released from 08/05/2007 to 08/10/2007 (Release 2). We measured soil CO₂ fluxes using the chamber method on grids repeatedly on a daily basis and net CO₂ fluxes continuously using the eddy covariance technique. Based on chamber measurements near the well, CO₂ breakthrough at the surface occurred on day two of Release 1. The spatial distribution and magnitude of leakage fluxes reached quasi-steady state by day six. Fluxes returned to near those measured at background locations two days following the end of Release 2. Spatial patterns in chamber CO₂ fluxes were strongly related to well design. Estimates of total, background (soil respiration), and leakage CO₂ discharges (t d^-1) based on chamber measurements showed that during Release 1, background CO₂ discharge was relatively high but declined at nearly the same rate as leakage discharge increased, leading to little change in total discharge. Conversely, during Release 2, background soil respiration remained low relative to leakage discharge. Because the comparatively large spatial footprint of the eddy covariance measurements averages over both background and well locations, CO₂ leakage signals were difficult to detect by eddy covariance during Release 1, while during Release 2, signals were clearly detectable. Results emphasize the influence of background CO₂ flux variations on the ability to detect leakage signals.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0394 Instruments and techniques
DE: 1865 Soils (0486)
DE: 1875 Vadose zone
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting