Tuesday, November 14, 2006 - 8:55 AM

Dynamics of N2O in Groundwater at the Aquatic-Terrestrial Interface.

Timothy Clough1, Kelly Addy2, Dorothy Kellogg3, Barbara Nowicki2, Arthur Gold4, and Peter Groffman5. (1) PO Box 84, Lincoln University, Soils Department, Canterbury, NEW ZEALAND, (2) Department of Natural Resources Science, University of Rhode Island,, 105 Coastal Institute in Kingston, One Greenhouse Road,, Kingston,, RI RI 02881, (3) University of Rhode Island, Dept. of Natural Resource Science, Rm 105 Coastal Inst. Kingston, Kingston, RI 02881, (4) 105 Coastal Institute, University of Rhode Island, University of Rhode Island, 1 Greenhouse Rd, Kingston, RI 02881-2018, (5) Institute Of Ecosystem Studies, Box Ab, Box Ab, Millbrook, NY 12545-0129, United States of America

Few data are available to validate the Intergovernmental Panel on Climate Change’s emission factors for indirect emissions of N2O. In particular the N2O emissions resulting from nitrogen leaching and the associated groundwater and surface drainage (EF5-g) are particularly poorly characterized. In situ push-pull methods have been used to identify the fate of NO3- in the groundwater. In this study, we adapted a previously published in situ denitrification push-pull method to examine the fate of 15N2O introduced into the subsoil-groundwater matrix. Enriched 15N2O was manufactured and introduced into the groundwater-subsoil matrix in both the fringe area of a salt marsh and a forested alluvial loamy soil. Conservative tracers (SF6 and Br-) and 15N2O were injected into the groundwater and left for 1 to 4 h after which the groundwater was sampled. Added 15N2O behaved in a conservative manner at one site while the other site showed variability with some injections showing significant consumption (3 - 8  μg N2O-15N kg-1 soil d-1) of 15N2O. Our results show that the fate and dynamics of N2O in groundwater are complex and variable and that these dynamics should be considered in the development of improved IPCC inventory calculations.