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| Titel |
Do diatoms percolate through soil and can they be used for tracing the origin of runoff? |
| VerfasserIn |
Lenka De Graaf, Erik Cammeraat, Laurent Pfister, Carlos Wetzel, Julian Klaus, Christophe Hissler |
| 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 |
250109086
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| Publikation (Nr.) |
 EGU/EGU2015-8961.pdf |
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| Zusammenfassung |
| Tracers are widely used to study the movement of water in a catchment. Because of depletion
of scientific possibilities with most common tracer types, we proposed the use of diatoms as a
natural tracer. Paradoxical results on the contribution of surface runoff to the storm
hydrograph were obtained in pioneer research on this idea. Diatom transport via the
subsurface flow to the stream would explain this paradox. Prerequisite for this is vertical
transport of diatoms through soils, which is the topic of this study. Emphasis is on percolation
behavior (speed of percolation, speed of percolation over time, and species distribution) of
Pseudostaurosira sp. and Melosira sp. (Bacillariophyceae) through undisturbed soil columns
of contrasting substrates. Co-objective is to study the flowpaths of water through the soil
columns.
Natural undisturbed soil columns were sampled in the Attert basin (Luxembourg) on
schist, marl and sandstone substrates. Rain simulation experiments were performed to
study vertical diatom transport. Rhodamine dye experiments were carried out to
gain insight in the active flowpaths of water, and breakthrough experiments were
performed to study the responses of the soil columns to applied water. Diatoms were
transported through the soil columns of the three substrates. A vast majority of diatom
percolation took place within the first 15 minutes, percolation hereafter was marginal
but nevertheless present. Peaks in diatom percolation corresponded with a high
flux caused by the addition of the diatom culture, but seepage of diatoms along
the sides is unlikely according to the species distribution and the rhodamine dye
experiment. Pseudostaurosira sp. percolated significantly better than Melosira sp.
Significantly more diatoms percolated through the marl columns compared to the
schist columns and variance within the sandstone group was very high. Absolute
differences between substrates however, were marginal. Most preferential flowpaths were
observed in the marl columns, indicating highest active macroporosity in these
columns. Although the sample size of this study was small, it is suspected that the
highest diatom percolation percentages of the marl columns is linked to its greater
macroporosity and most importantly, diatoms can percolate through soil (macro-) pores. |
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