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Simultaneous Determination of Nitrification and Nitrate Reduction in Sediment‐Water Columns by Nitrate‐15 Dilution
Author(s) -
DeLaune R. D.,
Smith C. J.
Publication year - 1987
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1987.00472425001600030007x
Subject(s) - nitrification , water column , nitrate , dilution , sediment , environmental chemistry , denitrification , ammonium , chemistry , isotope dilution , hydrology (agriculture) , nitrogen , geology , chromatography , oceanography , mass spectrometry , paleontology , physics , geotechnical engineering , organic chemistry , thermodynamics
The magnitude of N loss from nitrification‐denitrification reactions in sediment‐water columns of a freshwater lake of Louisiana Gulf Coast drainage basin receiving elevated N loading from agricultural runoff was determining using 15 NO 3 dilution. Isotope dilution using added labeled NO 3 allowed for the simultaneous determination of nitrification and NO 3 reduction in the sediment‐water column. The contribution of internal NH 4 pools in bottom sediment to NO 3 content in water column through diffusion and nitrification was measured. Nitrate reduction averaged 134 µ mol m −2 h −1 over a 50‐d incubation period in the sediment‐water columns. Nitrification averaged 90 µ mol m −2 h −1 , approximately 70% of the denitrification rate. Nitrification and ammonium assimilation were also determined in lake water using 15 N‐labeled NH 4 as a tracer. The nitrification rate determined in the water (0.9–1.4 mmol N m −3 d −1 ) was less than the rates measured in the sediment‐water columns (1.4–3.3 mmol N m −3 d −1 ) using 15 NO 3 dilution. The results presented and isotope dilution technique used are applicable for use in understanding the fate of N in sediment‐water systems of other aquatic environments.