Detection of CO2 leakage by eddy covariance during the ZERT project’s CO2 release experiments

Carbon dioxide was released from a shallow horizontal well for ten days at 0.1 t d−1 (Release 1) and for seven days at 0.3 t d−1 (Release 2) during Summer 2007. Net CO2 fluxes (Fc) were continuously monitored by eddy covariance during the summers of 2006 and 2007. To improve leakage detection ability, we removed ecosystem fluxes correlated with changes in soil temperature and light intensity from Fc. The Release 2 leakage signal was enhanced in a time series of upper 95th percentile residual Fc, while the Release 1 signal fell within the variability of unmodeled processes.