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Denitrification as a Sink for Dissolved Nitrous Oxide in a Freshwater Riparian Fen
Author(s) -
BlicherMathiesen Gitte,
Hoffmann Carl Chr.
Publication year - 1999
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/jeq1999.00472425002800010031x
Subject(s) - denitrification , nitrous oxide , denitrifying bacteria , riparian zone , environmental chemistry , sediment , chemistry , nitrate , zoology , nitrogen , ecology , geology , biology , organic chemistry , habitat , paleontology
Denitrification as a sink of dissolved nitrous oxide (N 2 O) was investigated in a freshwater riparian fen. In a 15‐m transect extending from the hillslope and into the fen the groundwater concentrations of nitrate (NO − 3 ) declined from 1.8 m M NO − 3 (25 mg L −1 ) to less than 0.01 m M NO − 3 , dissolved oxygen (O 2 ) and nitrous oxide (N 2 O) declined from approximately 110 µ M O 2 (3.5 mg O 2 L −1 ) and 4.0 µ M N 2 O‐N (56 µg N L −1 ), respectively, to zero and the dissolved N 2 concentration increased by 589 µ M N 2 ‐N (8.2 mg N L −1 ). The NO − 3 reduction was 0.42 µ M cm −3 d −1 or 7.71 µ M cm −2 d −1 in sediment columns with continuous upward groundwater flow through the sediment. Concomitant with NO − 3 reduction, N 2 O was produced at a rate of 54.4 n M N 2 O‐N cm −2 d −1 in this same 18‐cm narrow sediment zone. However, the N 2 O produced was subsequently reduced at the same rate closer to the sediment surface. In 15 NO − 3 experiments on chloramphenicol‐treated anaerobic sediment slurries, the denitrifying enzyme activity (DEA) was estimated to be 118 ± 16.7 nmol N (N 2 ‐N + N 2 O‐N) g fresh weight 1 −1 d −1 , of which 36% accumulated as N 2 O. Thus, in this permanently water‐covered riparian fen, denitrification served as a sink for both the dissolved N 2 O in groundwater recharging the fen and the N 2 O produced within the riparian sediment.