Denitrification as a sink for dissolved nitrous oxide in a freshwater riparian fen

Journal Article · · Journal of Environmental Quality

DOI:https://doi.org/10.2134/jeq1999.00472425002800010031x· OSTI ID:6151455

Blicher-Mathiesen, G; Hoffmann, C C ^[1]

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1. National Environmental Research Inst., Silkeborg (Denmark). Dept. of Streams and Riparian Areas

Denitrification as a sink of dissolved nitrous oxide (N[sub 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[sub 3][sup [minus]]) declined from 1.8 mM NO[sub 3][sup [minus]] to less than 0.01 mM NO[sub 3][sup [minus]], dissolved oxygen (O[sub 2]) and nitrous oxide (N[sub 2]O) declined from approximately 110 [micro]M O[sub 2] (3.5 mg O[sub 2] LO[sup [minus]1]) and 4.0 [micro]M N[sub 2]O-N, respectively, to zero and the dissolved N[sub 2] concentration increased by 589 [micro]M N[sub 2]-N. The NO[sub 3][sup [minus]] reduction was 0.42 [micro]M cm[sup [minus]3] d[sup [minus]1] or 7.71 [micro]M cm[sup [minus]2]d[sup [minus]1] in sediment columns with continuous upward groundwater flow through the sediment. Concomitant with NO[sub 3][sup [minus]] reduction, N[sub 2]O was produced at a rate of 54.4 nM N[sub 2]O-N cm[sup [minus]2] d[sup [minus]1] in this same 18-cm narrow sediment zone. However, the N[sub 2]O produced was subsequently reduced at the same rate closer to the sediment surface. In [sup 15]NO[sub 3][sup [minus]] experiments on chloramphenicol-treated anaerobic sediment slurries, the denitrifying enzyme activity (DEA) was estimated to be 118 [+-] 16.7 nmol N (N[sub 2]-N + N[sub 2]O-N)g fresh weight[sup [minus]1] d[sup [minus]1], of which 36% accumulated as N[sub 2]O. Thus, in this permanently water-covered riparian fen, denitrification served as a sink for both the dissolved N[sub 2]O in groundwater charging the fen and the N[sub 2]O produced within the riparian sediment.

• OSTI ID: 6151455
• Journal Information: Journal of Environmental Quality, Vol. 28:1; ISSN 0047-2425
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BIODEGRADATION
DENITRIFICATION
GROUND WATER
MICROCOSMS
NITRATES
NITROGEN CYCLE
NITROUS OXIDE
SINKS
WATER POLLUTION
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
HYDROGEN COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
POLLUTION
WATER
540220* - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)