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| Titel |
Effective denitrification at the groundwater surface-water interface: exposure rather than residence time |
| VerfasserIn |
Stefan Peiffer, Sven Frei |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094831
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| Publikation (Nr.) |
 EGU/EGU2014-10263.pdf |
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| Zusammenfassung |
| Effective processing of material in aquatic systems, e. g. removal of nitrate upon
denitrification, requires sufficient reaction time. This statement sounds trivial albeit its
implication for biogeochemistry seems to be not fully recognized.
The time teff required for effective processing of nitrate is controlled by the underlying
biogeochemical rate law. In the simplest case of a 1st order reaction, teff is often
calculated as the time when 63% of the initial concentration is consumed setting teff as
1/kreaction. It may, however, be more appropriate to derive teff,90%or teff,99% from the
respective rate law. Hence a minimum time t > teff is required that exposes a specific
biogeochemical process to conditions favourable for this process, which is anoxia in case of
denitrification.
This exposure time Ïexp is not necessarily identical to the residence time Ï
of water in the particular system or flow path. Rather, the exposure time can be
much shorter and may even fluctuate with time. As a consequence, Damköhler
numbers (Da = Ïexp/teff) for denitrification < 1 may be the consequence even
though the age of water may be comparatively high. We therefore argue that the
key for understanding denitrification efficiency at the groundwater surface-water
interface (or in groundwater systems in general) is the quantification of the exposure
time.
This contribution therefore aims i) to estimate exposure times required for effective
denitrification based on an analysis of rate constants for denitrification, ii) to relate these time
scales to typical residence time distributions found at the groundwater surface-water interface
and iii) to discuss implications for denitrification efficiencies.
References:
Oldham, C; Farrow, DE; Peiffer, S (2013): A generalized Damköhler number for
classifying material processing in hydrological systems, Hydrology and Earth System
Sciences, 17, 1133-1148
Frei, S; Knorr, KH; Peiffer, S; Fleckenstein, J (2012): Surface micro-topography
causes hot spots of biogeochemical activity in wetland systems - a virtual modeling
experiment., Journal of Geophysical Research - Biogeosciences, 117(G00N12), 1 - 18 |
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