HR: 1340h
AN: B43A-0889    [Abstracts]
TI: Laboratory incubation studies to investigate the control of isotopologue signatures of soil- emitted N₂O
AU: * Well, R
EM: rwell@gwdg.de
AF: Abteilung Oekopedologie der gemaessigten Zone, Buesgeninstitut, Universitaet Goettingen, Buesgenweg 2, Goettingen, 37077, Germany
AU: Flessa, H
EM: hflessa@gwdg.de
AF: Abteilung Oekopedologie der gemaessigten Zone, Buesgeninstitut, Universitaet Goettingen, Buesgenweg 2, Goettingen, 37077, Germany
AB: Isotopologue signatures of N₂O such as δ¹⁸O, average δ¹⁵N (δ¹⁵Nbulk) and ¹⁵N site preference (SP = difference in δ¹⁵N between the central and peripheral N positions of the asymmetric N2O molecule) can be used to constrain the atmospheric N₂O budget and to characterize N₂O turnover processes. However, the use of this approach to study N₂O dynamics in soils requires knowledge of isotopologue fractionation factors (ε) for the various partial processes involved, e.g. N₂O production by nitrification or denitrification, and N₂O reduction by denitrification. The aim of our study is to investigate the control of isotopologue signatures of soil-emitted N₂O. Two soils were incubated in the laboratory under varying conditions in order to manipulate the partial processes of N₂O turnover. ε of δ¹⁸O, δ¹⁵Nbulk and SP was determined in experiments, where only one of the partial processes was governing the isotopic signature of N₂O in the incubation system of the respective treatment. ε of nitrification was determined by favoring N₂O fluxes originating from NH₄⁺ oxidation using high NH₄⁺ levels and low soil moisture (30 to 50 % water-filled pore space). ε of N₂O production by denitrification was obtained by anaerobic incubation of NO₃^- amended soils when N₂O reduction was inhibited by 10 kPa acetylene. ε of N₂O reduction was derived by (i) comparing treatments with and without inhibition of N₂O reduction or (ii) by monitoring the time course of isotopic signatures of N₂O applied to the headspace of NO₃^-- depleted anaerobic soil. To investigate the combined effect of various simultaneous processes, isotopologue signatures of N₂O emitted from soils incubated under varying N-fertilizer level and moisture were measured while gross rates of the partial processes were determined independently. Results of fractionation factors and isotopologue signatures will be presented and discussed in view of previous studies and theoretical considerations.
DE: 0402 Agricultural systems
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0469 Nitrogen cycling
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: 2007 Fall Meeting