title: Fractionation factors for stable isotopes of N and O during N2O reduction in soil depend on reaction rate constant.
abstract: Nitrous oxide (N(2)O) is a major greenhouse gas that is mainly produced but also reduced by microorganisms in soils. We determined factors for N and O isotope fractionation during the reduction of N(2)O to N(2) in soil in a flow-through incubation experiment. The absolute value of the fractionation factors decreased with increasing reaction rate constant. Reaction rates constants ranged from 1.7 10(-4) s(-1) to 4.5 10(-3) s(-1). The minimum, maximum and median of the observed fractionation factors were for N -36.0 per thousand, -1.0 per thousand and -9.3 per thousand and for O -74.0 per thousand, -6.9 per thousand and -26.3 per thousand, respectively. The ratio of O isotope fractionation to N isotope fractionation was 2.4 +/- 0.3 and it was independent from the reaction rate constants. This leads us to conclude that fractionation factors are variables while their ratio in this particular reaction might be a constant.
authors.affiliation: Institute of Environmental Geosciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland. b.vieten@unibas.ch
authors.forename: Beatrix
authors.initials: B
authors.lastname: Vieten
authors.forename: Thomas
authors.initials: T
authors.lastname: Blunier
authors.forename: Albrecht
authors.initials: A
authors.lastname: Neftel
authors.forename: Christine
authors.initials: C
authors.lastname: Alewell
authors.forename: Franz
authors.initials: F
authors.lastname: Conen