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| Titel |
Fluorescent diatoms as hydrological tracers: a proof of concept percolation experiment |
| VerfasserIn |
Flavia Tauro, Núria Martínez-Carreras, Carlos E. Wetzel, Christophe Hissler, Francois Barnich, Jay Frentress, Luc Ector, Lucien Hoffmann, Jeffrey J. McDonnell, Laurent Pfister |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078847
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| Zusammenfassung |
| Tracers are widely used in catchment hydrology to understand natural phenomena, such
as runoff generation processes and water flowpaths, due to their versatility and
generally good detectability. Although tracing methodologies are key observational
tools in complex settings such as ungauged basins, their implementation can be
hindered by cumbersome detection procedures, unrealistic mixing assumptions, and
temporally and spatially varying concentrations. In this framework, recent efforts are
being devoted to the development of novel tracing techniques with the twofold
objective of reducing tracer identification uncertainty while minimizing detection
equipment. Specifically, living organisms such as diatoms have proven successful
to investigate rainfall-runoff events, thus positing their feasibility as hydrologic
tracers.
In previous and ongoing research from our group, sampling and analysis of terrestrial diatoms
in the Weierbach catchment (NW Luxembourg) highlight substantial contribution of soil and
groundwater to stream water during winter and summer events, respectively. Nonetheless,
terrestrial diatom concentration is observed to increase with precipitation in stream water
samples even if overland flow relative contribution is meager. Possible motivations for such
behavior can be sought in the transfer and flushing of diatoms through subsurface macropore
networks.
In this work, we study the hypothesis of terrestrial diatom flushing through shallow soil
macropores by conducting proof of concept percolation experiments with fluorescent diatoms
in laboratory settings. Specifically, labeled diatoms are synthesized by either functionalizing their
frustules through Rhodamine 123 adsorption or by growing Conticribra weissflogii (Grunow)
Stachura-Suchoples & D.M. Williams cultures in the presence of the biogenic silica tracer
2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)-phenyl)oxazole
(PDMPO). Labeled diatoms demonstrate good resilience under weathering agents and
enhanced detectability through expeditive and noninvasive spectrofluorometry techniques.
Selected quantities of fluorescent diatoms are deployed on the surface of undisturbed and
saturated soil cores from the Weierbach (0.45km2, schistous, loamy to sandy soils) and
Huewelerbach (2.7km2, sandstone, sandy soils) catchments to experiment with
varying soil matrices. Water is added in constant volumes to induce percolation and
samples recovered at the bottom of the columns are analyzed through microscopy and
spectrofluorometry.
Experimental findings suggest that diatom flushing through the soil cores does not occur after
the addition of significant water volumes and for time scales on the order of ten hours. Not
taking into account inherent complexities found in the environment, these results are a first
step towards a comprehensive understanding of diatom transport in natural watersheds.
Further work will be devoted to study the effects of rain drop energy on macropore formation
and consequent diatom transfer as well as the impact of series of precipitation events on cell
mobility. |
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