Isotopologue signatures of N2O such as 18O, average 15N (15Nbulk) and 15N site preference (SP = difference
in 15N 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 (") for the various partial
processes involved, e.g. N2O production by nitrification or denitrification, and N2O reduction by denitrification.
Here we present results from laboratory incubations of soils and aquifer material to determine "gf N2O production
("prod) and N2O reduction to N2 ("red) during denitrification. "prod for 18O, 15Nbulk and SP was obtained
by anaerobic incubation of NO
3 amended soils when N2O reduction was inhibited by 10 kPa acetylene. "red
of the respective signatures was derived by comparing treatments with and without inhibition of N2O reduction.
We investigated samples from 4 mineral soils, one organic soil and from a sandy aquifer. The mineral soils were
incubated under unsaturated conditions in closed or open systems, the organic and aquifer samples as homogenized
slurries in a closed system.
Results of fractionation factors, process rates and incubation conditions will be presented and discussed in view of
previous studies and theoretical considerations.