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| Titel |
Denitrification activity of aquifer material from two different sandy aquifers in northern Germany measured by laboratory incubation experiments in relation to influencing sediment parameters |
| VerfasserIn |
Wolfram Eschenbach, Reinhard Well, Heiner Flessa, Wilhelmus H. M. Duijnisveld, Wolfgang Walther |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039345
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| Zusammenfassung |
| In NO3¯ contaminated aquifers containing reduced compounds like organic carbon or
sulfides, denitrification is an intense process. Its characterization is of interest because NO3¯
consumption improves water quality and N2O production can cause emission of this
greenhouse gas to the atmosphere. Spatial distribution of NO3¯ and N2 produced by
denitrification in groundwater (excess N2) reflects the NO3¯ input as well as cumulative
denitrification during aquifer passage. The amount and spatial distribution of reduced
compounds within denitrifying aquifers is not well known. Recent findings from parallel
investigations on in situ denitrification and reactive compounds suggests that single-well 15N
tracer tests might be suitable to characterize the stock of reduced compounds in
aquifers (Konrad 2008), but an evaluation of this approach has not been realized until
now.
The overall objective of our studies is to measure the spatial and long-term dynamics of
denitrification within two sandy aquifers in northern Germany. This includes measurement of
the actually occurring denitrification process in the field by 15N-tracer experiments and
incubation experiments with corresponding aquifer material. Beside the comparison of field
and laboratory data concerning the denitrification activity, we also want to determine the
long-term denitrification potential which is governed by the stock of reactive material within
these sediments.
Here we present the first results of these long-term incubation experiments to investigate
the stock of reactive material present in these sediments and its denitrification activity. In
these batch experiments we filled the aquifer material from different depths between two and
68 m below ground in glass bottles, supplemented it with K15NO3 solution, sealed the bottles
airtight with rubber septa and flushed the headspace with pure N2. Afterward the
bottles where stored in the dark by 10Ë C to obtain aquifer like conditions. The
labeled denitrification products (15[N2O+N2]), N2, N2O, CO2, Nitrate, Sulfate
and pH were analyzed six times during the experiment. In order to study the stock
of reduced compounds within the incubated sediments we also performed other
laboratory measurements with the aquifer material. We measured its capability to reduce
potassium permanganate and the concentrations of extractable sulfate, dissolved
organic carbon, hot water soluble organic matter and total C, N and S per kilogram
sediment.
Results up to now show for most of the incubated glass bottles with sediments
an almost linear increase of the denitrification products over time. The measured
denitrification rates for aquifer material from the zone of heterotrophic denitrification and
for sediments from the zone of autotrophic denitrification range from 0.2 to 42
μg N kg-1d-1and from 22 to 120 μg N kg-1d-1, respectively. The relationships
between denitrification rates and the parameters of the reduced compounds will be
discussed.
References:
Konrad, C. (2008): Methoden zur Bestimmung des Umsatzes von Stickstoff, dargestellt
für drei pleistozäne Grundwasserleiter Norddeutschlands, PhD thesis, Dresden Univ. of
Techn., Germany, 157 pp. |
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