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| Titel |
Radial Continuous Time Random Walks for Non-Fickian Solute Transport under Forced Flow Conditions and Different Heterogeneity Scenarios |
| VerfasserIn |
Marco Dentz, Peter K. Kang, Tanguy Le Borgne |
| 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 |
250107407
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| Publikation (Nr.) |
 EGU/EGU2015-7108.pdf |
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| Zusammenfassung |
| Solute transport in heterogeneous porous media is characterized by features that do not
conform to advection-dispersion models characterized by equivalent transport parameters.
This has been observed in tracer experiments under forced and natural flow conditions. Key
questions are (i) how non-Fickian solute transport can be quantified under radial flow
conditions, and (ii) how different heterogeneity sources of non-Fickian behavior manifest in
non-Fickian radial transport models. In order to approach these questions, we develop a
radial continuous time random walk (CTRW) formulation for the quantification and
interpretation of non-Fickian solute transport under forced flow conditions and different
heterogeneity scenarios. The derived radial CTRW approaches model anomalous behavior
induced by heterogeneous flow distributions and mobile-immobile mass transfer
processes (matrix diffusion). We start by establishing a general CTRW framework in
radial coordinates on the basis of the random walk equations for radial particle
positions and times. The evolution of solute concentration is governed by a non-local
radial advection-dispersion equation. Unlike in CTRWs for uniform flow scenarios,
particle transition times here depend on the radial particle position, which renders the
CTRW non-stationary. We then derive radial CTRW implementations that (i) emulate
non-local radial transport due to heterogeneous advection, (ii) model multirate mass
transfer (MRMT) between mobile and immobile continua, and (iii) quantify both
heterogeneous advection in a mobile and mass transfer between mobile and immobile
regions. We analyze the transport signatures for the distinct CTRW models in terms of
solute breakthrough curves and their dependence on the heterogeneity scenarios. |
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