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Oxygen exchange between (de)nitrification intermediates and H 2 O and its implications for source determination of NO 3 − and N 2 O: a review
Author(s) -
Kool D. M.,
Wrage N.,
Oenema O.,
Dolfing J.,
Van Groenigen J. W.
Publication year - 2007
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3249
Subject(s) - chemistry , nitrification , nitrous oxide , environmental chemistry , denitrification , nitrate , oxygen , isotopic signature , ecosystem , stable isotope ratio , nitrogen , ecology , organic chemistry , physics , quantum mechanics , biology
Stable isotope analysis of oxygen (O) is increasingly used to determine the origin of nitrate (NO 3 − ) and nitrous oxide (N 2 O) in the environment. The assumption underlying these studies is that the 18 O signature of NO 3 −and N 2 O provides information on the different O sources (O 2 and H 2 O) during the production of these compounds by various biochemical pathways. However, exchange of O atoms between H 2 O and intermediates of the (de)nitrification pathways may change the isotopic signal and thereby bias its interpretation for source determination. Chemical exchange of O between H 2 O and various nitrogenous oxides has been reported, but the probability and extent of its occurrence in terrestrial ecosystems remain unclear. Biochemical O exchange between H 2 O and nitrogenous oxides, NO 2 −in particular, has been reported for monocultures of many nitrifiers and denitrifiers that are abundant in nature, with exchange rates of up to 100%. Therefore, biochemical O exchange is likely to be important in most soil ecosystems, and should be taken into account in source determination studies. Failing to do so might lead to (i) an overestimation of nitrification as NO 3 −source, and (ii) an overestimation of nitrifier denitrification and nitrification‐coupled denitrification as N 2 O production pathways. A method to quantify the rate and controls of biochemical O exchange in ecosystems is needed, and we argue this can only be done reliably with artificially enriched 18 O compounds. We conclude that in N source determination studies, the O isotopic signature of especially N 2 O should only be used with extreme caution. Copyright © 2007 John Wiley & Sons, Ltd.