ARS | Publication request: PRODUCTION AND TRANSPORT OF DENITRIFICATION GASSES IN SHALLOW GROUND WATER

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Proceedings
Publication Acceptance Date: November 1, 2000
Publication Date: N/A

Technical Abstract: The contribution of N2O to the atmosphere from denitrification in hydromorphic soils is poorly understood. This study investigated the contribution of the saturated zone to surface N2O emission for two fen soils and a Gleyic Luvisol. Total denitrification, denitrification N2O production, ground water dissolved N2 and/or N2O, and surface N2O emissions were measured in situ. Concentrations of dissolved gases and surface emissions were also simulated with a simple process-based model assuming measured rates of N2 and N2O production or constant profiles of dissolved N2O concentration. NO3- and N2O were abundant in all samples of the three sites. Substantial N2O surface emission originating from the saturated zone was measured at both fen sites. Concentrations of N2O measured at the fen sites were 1 to 2 orders of magnitude lower than stimulated concentrations. In contrast, measured N2O emissions were within the order of magnitude of emissions simulated assuming measured N2 and N2O production rates. The agreement between measured and simulated N2O concentrations and surface emissions was satisfactory when gas diffusivity and N2O reduction in the stimulation were multiplied by 10 and 20, respectively. At the Lake Creek site, the measured peak concentration of dissolved N2 was relatively close to the concentration. It was concluded that the disagreements between measured and simulated values of N2O concentrations and emissions resulted from the underestimation of model parameters for gas transfer or for N2O reduction to N2, or both, which were not measured.