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Evaluation of the nitrogen isotope‐pairing method for measuring benthic denitrification: A simulation analysis
Author(s) -
Middelburg Jack J.,
Soetaert Karline,
Herman Peter M. J.
Publication year - 1996
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1996.41.8.1839
Subject(s) - denitrification , benthic zone , nitrification , nitrogen cycle , nitrogen , isotopes of nitrogen , environmental science , environmental chemistry , isotope , pairing , nitrate , diagenesis , chemistry , geology , mineralogy , oceanography , physics , superconductivity , organic chemistry , quantum mechanics
The nitrogen isotope‐pairing method to measure sedimentary denitrification is evaluated by means of a general diagenetic model that describes the depth distribution of O 2 , NH 4 + , 14 NO 3 ‒ , and 15 NO 3 ‒ , among others. The model simulations demonstrate that isotope fractionation effects during denitrification can be neglected, but that nonuniform mixing of added 15 NO 3 ‒ with locally produced 14 NO 3 ‒ causes underestimation of in situ rates of denitrification. Enrichment of bottom water with 15 NO 3 ‒ concentrations above ambient levels not only results in enhanced rates of denitrification, but may also change in situ rates of coupled nitrification‐denitrification. However, the resulting rates usually deviate < 10% from in situ values, and the nitrogen isotope‐pairing method therefore remains a powerful technique to determine rates of denitrification in sediments. We argue that one should not partition denitrification into bottom‐water‐supported and nitrification‐coupled components. This partitioning causes confusion, is not required to understand sedimentary nitrogen cycling, and does not reflect a physically realizable situation.