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Isotope dilution models and the mystery of the vanishing 15 N
Author(s) -
Laws Edward
Publication year - 1984
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.1984.29.2.0379
Subject(s) - isotope dilution , dilution , adsorption , nitrification , chemistry , isotope , environmental chemistry , particulates , nitrogen , stable isotope ratio , analytical chemistry (journal) , environmental science , chromatography , thermodynamics , mass spectrometry , physics , nuclear physics , organic chemistry
An examination of recently published 15 NH 4 + uptake data shows that the amount of 15 N which disappeared from the NH 4 + phase was consistently greater than that which appeared in the particulate phase. The discrepancy, which ranged from 1.5 to 5.6 times at nine stations, did not seem to be caused by analytical errors in NH 4 + or isotope ratio measurements. Possible mechanisms for the loss include nitrification, adsorption of NH 4 + to clay particles or to container walls, and release of 15 N as dissolved organic nitrogen. A new method for calculating the average atom % excess of the NH 4 + improves estimates of NH 4 + assimilation in cases where experimental data indicate that uptake and regeneration are not in balance. Correction of a mathematical misconception regarding the Blackburn‐Caperon model allows more accurate estimates of NH 4 + uptake and regeneration rates.