Isotopomer fractionation during N2O consumption within soil mesocosms as a function of water filled pore space

HR: 0800h
AN: B11A-1029 [Abstracts]
TI: Isotopomer fractionation during N2O consumption within soil mesocosms as a function of water filled pore space
AU: * Jinuntuya, M
EM: jinuntuy@msu.edu
AF: Michigan State University, 237 Natural Science Building, East Lansing, MI 48824 United States
AU: Ostrom, N E
EM: ostromn@msu.edu
AF: Michigan State University, 237 Natural Science Building, East Lansing, MI 48824 United States
AU: Ostrom, P
EM: ostrom@msu.edu
AF: Michigan State University, 237 Natural Science Building, East Lansing, MI 48824 United States
AU: Sutka, R
EM: sutkarob@msu.edu
AF: Michigan State University, 237 Natural Science Building, East Lansing, MI 48824 United States
AB: Our prior research has demonstrated that the intramolecular distribution of ¹⁵N within the N₂O molecule can be used to distinguish N₂O derived from nitrification and denitrification. For this approach to be successful, however, the affect of fractionation during consumption of N₂O by denitrification must be understood. Stable isotope and isotopomer analysis of soil mesocosm experiments were used to investigate fractionation of N₂O during consumption at four different levels of water filled pores space (WFPS) 60, 80, 100 and 110% Uncultivated soil from the Long Term Ecological Research Site at Kellogg Biological Station was used to establish that the fractionation factors for δ¹⁵N, δ¹⁸O-N₂O, δ¹⁵Nα and δ¹⁵Nβ ranged from -4.2 to -7.8 ‰, -12.5 to -19.1 ‰,-5.3 to -9.7‰ and -2.0 to -6.0 ‰, respectively. Lower fractionation factors were observed at higher WFPS demonstrating the importance of diffusion in limiting the expression of fractionation. The small degree of fractionation for δ¹⁵Nα and δ¹⁵Nβ indicates that consumption must be marked (e.g. >50%) before a significant isotope effect is observed. Our characterization of fractionation factors as a function of WFPS provides a basis to apportion the origins of N₂O even when consumption is evident.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 4870 Stable isotopes (0454, 1041)
SC: Biogeosciences [B]
MN: Fall Meeting 2005