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| Titel |
Field scale variability of solute transport parameters and related soil properties |
| VerfasserIn |
B. Lennartz, S. K. Kamra, S. Meyer-Windel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 1, no. 4 ; Nr. 1, no. 4, S.801-811 |
| Datensatznummer |
250000235
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| Publikation (Nr.) |
 copernicus.org/hess-1-801-1997.pdf |
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| Zusammenfassung |
| The spatial variability of transport parameters has
to be taken into account for a reliable assessment of solute behaviour in natural field soils. Two field sites
were studied by collecting 24 and 36 small undisturbed soil columns at an uniform grid of 15 m
spacing. Displacement experiments were conducted in these columns with bromide traced water
under unsaturated steady state transport conditions. Measured breakthrough curves (BTCs)
were evaluated with the simple convective-dispersive equation (CDE). The solute mobility
index (MI) calculated as the ratio of measured to fitted pore water velocity and the dispersion
coefficient (D) were used to classify bromide breakthrough behaviour. Experimental BTCs were
classified into two groups: type I curves expressed classical solute behaviour while type
II curves were characterised by the occurrence of a bromide concentration maximum
before 0.35 pore volumes of effluent (MI<0.35) resulting from preferential flow conditions.
Six columns from site A and 8 from site B were identified as preferential. Frequency distributions
of the transport parameters (MI and D) of both sites were either extremely skewed or bimodal. Log-transformation
did not lead to a normal distribution in any case. Contour maps of bromide
mass flux at certain time steps indicated the clustering of preferential flow regions at both
sites. Differences in the extent of preferential flow between sites seemed to be governed by soil structure.
Linear cross correlations among transport parameters and independently measured
soil properties revealed relations between solute mobility and volumetric soil water content
at time of sampling, texture and organic carbon content. The volumetric field soil water content,
a simple measure characterising the soil hydraulic behaviour at the sampling location, was
found to be a highly sensitive parameter with respect to solute mobility and preferential flow situations.
Almost no relation was found between solute transport parameters and independently determined
soil properties when non-preferential and preferential samples were considered separately
in regression analyses. Future work should concentrate to relate integrated parameters such
as the infiltration rate or the soil hydraulic functions to solute mobility under different flow
situations. |
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