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| Titel |
The impact of transverse mixing on spreading of solutes in highly heterogeneous aquifers |
| VerfasserIn |
G. Dagan, A. Fiori |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020841
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| Zusammenfassung |
| Transport of solutes in aquifers has been investigated intensively in a stochastic
framework in the last three decades. The main aim was to relate the spreading and
mixing of solute to the aquifer spatial distribution of hydraulic conductivity K and to
water flow conditions. Due to the seemingly erratic distribution and uncertainty,
Y=lnK is usually modeled as a stationary random space function characterized by
the geometric mean KG,the variance ÏY 2 and the horizontal Ih and verticalIv
integral scales. For simplicity, natural gradient flow is modeled as of mean uniform
flow of velocity U and mean head gradient -- J. With an initial solute plume of
constant concentration C0 , solute spreading is characterized by global measures,
e.g. the spatial (centroid location and second moments) and temporal (the mean
and variance of mass arrival at control planes) ones. For large, ergodic, plumes,
the longitudinal αLand transverse αT macrodispersivities are defined with the aid
of the second moments. Simple analytical results were obtained in the past for
weak heterogeneity (ÏY 2 1), the flow and transport
equations were solved in the past only numerically or by semi-analytical approximations. It
was found that solute plumes become skewed and αLmay display an apparent anomalous
behavior, by growing for a considerable time or distance from the injection zone. In such
cases, transverse pore scale dispersion may affect considerably spreading.
The main aim of the presentation is to discuss the influence of the finite Peclet number on
αL for highly heterogeneous formations. The analysis is focused on the essential
differences between transport in flow parallel to the bedding in stratified formations
(Ih -Iv - -) analyzed in the past by Matheron and de Marsily and recent results
obtained for isotropic formations. The practical implications of these findings on prediction
of contaminant spreading are discussed. |
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