scholarly journals Experimental investigation of oxygen isotope exchange between CO2and O(1D) and its relevance to the stratosphere

2003 ◽  
Vol 108 (D23) ◽  
Author(s):  
Subrata Chakraborty
Keyword(s):  
Experimental Investigation ◽  
Oxygen Isotope ◽  
Isotope Exchange ◽  
Oxygen Isotope Exchange

Coupled cation and oxygen-isotope exchange between alkali feldspar and aqueous chloride solution

2004 ◽  
Vol 89 (11-12) ◽  
pp. 1822-1825 ◽  
Author(s):  
Theodore C. Labotka ◽  
David R. Cole ◽  
Mostafa Fayek ◽  
Lee R. Riciputi ◽  
Frank J. Stadermann
Keyword(s):  
Oxygen Isotope ◽  
Isotope Exchange ◽  
Chloride Solution ◽  
Alkali Feldspar ◽  
Oxygen Isotope Exchange ◽  
Aqueous Chloride Solution ◽  
Aqueous Chloride

Oxygen isotope exchange and closure temperatures in cooling rocks

1994 ◽  
Vol 12 (3) ◽  
pp. 221-235 ◽  
Author(s):  
G. R. T. JENKIN ◽  
C. M. FARROW ◽  
A. E. FALLICK ◽  
D. HIGGINS
Keyword(s):  
Oxygen Isotope ◽  
Isotope Exchange ◽  
Oxygen Isotope Exchange

scholarly journals Oxygen isotope fractionation during N<sub>2</sub>O production by soil denitrification

2016 ◽  
Vol 13 (4) ◽  
pp. 1129-1144 ◽  
Author(s):  
Dominika Lewicka-Szczebak ◽  
Jens Dyckmans ◽  
Jan Kaiser ◽  
Alina Marca ◽  
Jürgen Augustin ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Soil Water ◽  
Isotope Effect ◽  
Isotope Exchange ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
N2o Production ◽  
Oxygen Isotope Fractionation ◽  
Oxygen Isotope Exchange ◽  
Incubation Experiments

Abstract. The isotopic composition of soil-derived N2O can help differentiate between N2O production pathways and estimate the fraction of N2O reduced to N2. Until now, δ18O of N2O has been rarely used in the interpretation of N2O isotopic signatures because of the rather complex oxygen isotope fractionations during N2O production by denitrification. The latter process involves nitrate reduction mediated through the following three enzymes: nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR). Each step removes one oxygen atom as water (H2O), which gives rise to a branching isotope effect. Moreover, denitrification intermediates may partially or fully exchange oxygen isotopes with ambient water, which is associated with an exchange isotope effect. The main objective of this study was to decipher the mechanism of oxygen isotope fractionation during N2O production by soil denitrification and, in particular, to investigate the relationship between the extent of oxygen isotope exchange with soil water and the δ18O values of the produced N2O. In our soil incubation experiments Δ17O isotope tracing was applied for the first time to simultaneously determine the extent of oxygen isotope exchange and any associated oxygen isotope effect. We found that N2O formation in static anoxic incubation experiments was typically associated with oxygen isotope exchange close to 100 % and a stable difference between the 18O ∕ 16O ratio of soil water and the N2O product of δ18O(N2O ∕ H2O)  =  (17.5 ± 1.2) ‰. However, flow-through experiments gave lower oxygen isotope exchange down to 56 % and a higher δ18O(N2O ∕ H2O) of up to 37 ‰. The extent of isotope exchange and δ18O(N2O ∕ H2O) showed a significant correlation (R2 = 0.70, p <  0.00001). We hypothesize that this observation was due to the contribution of N2O from another production process, most probably fungal denitrification. An oxygen isotope fractionation model was used to test various scenarios with different magnitudes of branching isotope effects at different steps in the reduction process. The results suggest that during denitrification, isotope exchange occurs prior to isotope branching and that this exchange is mostly associated with the enzymatic nitrite reduction mediated by NIR. For bacterial denitrification, the branching isotope effect can be surprisingly low, about (0.0 ± 0.9) ‰, in contrast to fungal denitrification where higher values of up to 30 ‰ have been reported previously. This suggests that δ18O might be used as a tracer for differentiation between bacterial and fungal denitrification, due to their different magnitudes of branching isotope effects.

Sign in / Sign up

Export Citation Format

Share Document