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| Titel |
Dissolved Oxygen Concentration Profiles in the Hyporheic Zone Through the Use of a High-Density Fiber Optic Measurement Network |
| VerfasserIn |
William Jeffrey Reeder, Annika Quick, Tiffany B. Farrell, Shawn G. Benner, Kevin P. Feris, Daniele Tonina |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102189
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| Publikation (Nr.) |
 EGU/EGU2015-1494.pdf |
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| Zusammenfassung |
| The majority of chemical reactions in riverine systems occur within the hyporheic zone (HZ).
Hyporheic exchange, flow into and out of the hyporheic zone, represents a primary control
over those reactions because the flow rate will determine the residence time and amount of
chemical constituents in the HZ. Hyporheic flow can be conceptualized as discreet
streamlines that collectively represent a broad distribution of residence times. Within this
context, dissolved oxygen (DO) concentration becomes a primary indicator of the redox and
biochemical state of the HZ including, for example, the fate of carbon, contaminant behavior,
nutrient cycling, stream DO levels and nitrous oxide (N2O) production. River systems have
been identified as a significant source of N2O emissions, contributing an estimated 10% of
anthropogenically generated N2O. The primary biochemical transformations that lead
to N2O production are nitrification (NH4+ to NO3-) and denitrification (NO3-
to N2) reactions that are mediated by microbes living in the HZ. Current theory
describes a process in which DO enters the stoss side of the HZ and is consumed by
respiration and nitrification in the upstream, oxic portion of the streamlines leading to a
progressive partitioning of the HZ from oxic to anoxic. This conceptualization,
however, has not been well validated in a physical sense, due to inherent difficulties
associated with measuring chemical concentrations in the HZ. To test current theory,
we measured HZ DO concentrations, in a large-scale flume experiment, almost
continuously for five months using a multiplexed optical network and a precision
robotic surface probe system. We were able to measure DO at higher spatial and
temporal resolution than has been previously demonstrated. These measurements,
coupled with detailed numerical modeling of HZ flowlines, allowed us to map HZ
DO concentrations spatially and over time. Our findings validate the models that
describe the consumption of DO through microbial processes. Additionally, our results
show that residence time is a strong predictor of DO concentration within the HZ. |
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