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AGU: Water Resources Research

 

Keywords

  • mass transfer
  • temporal moment
  • memory function

Index Terms

  • Hydrology: Groundwater transport
  • Hydrology: Numerical approximations and analysis
  • Hydrology: Modeling

Abstract

WATER RESOURCES RESEARCH, VOL. 44, W01502, 7 PP., 2008
doi:10.1029/2007WR006262

Temporal moments for transport with mass transfer described by an arbitrary memory function in heterogeneous media

Jian Luo

School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA

Olaf A. Cirpka

Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland

Marco Dentz

Department of Geotechnical Engineering and Geosciences, Technical University of Catalonia, Barcelona, Spain

Jesus Carrera

Department of Geotechnical Engineering and Geosciences, Technical University of Catalonia, Barcelona, Spain

Temporal moment equations are generalized for transport under linear mass transfer, which has been used to model a broad range of small-scale processes: kinetic sorption, diffusion into immobile regions, and transport through heterogeneous aquifers. Solving the moment equations, which are formally identical to steady state transport equations, is computationally more efficient than evaluating the temporal moments by integrating the transient flux concentrations. We derive recursive relations for the moments of the flux concentration, which involve the moments of the memory function but do not dependent on its shape. It turns out that two mass transfer models have the same kth temporal moment if the moments of order lower than k are equal. Particularly, the mean retention time, i.e., the first moment of the retention probability density function (pdf) in the immobile domain, decides the second temporal moment of concentration. A mass transfer model with two first-order rate coefficients can match up to the fourth temporal moment described by a multirate model with a predescribed pdf of the mass transfer rate coefficient. The kth temporal moment is finite when the (k-1)th moment of the memory function exists.

Received 14 June 2007; accepted 7 October 2007; published 18 January 2008.

Citation: Luo, J., O. A. Cirpka, M. Dentz, and J. Carrera (2008), Temporal moments for transport with mass transfer described by an arbitrary memory function in heterogeneous media, Water Resour. Res., 44, W01502, doi:10.1029/2007WR006262.

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