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@ARTICLE{Mojid:44581,
      author       = {Mojid, M. A. and Vereecken, H.},
      title        = {{O}n the physical meaning of retardation factor and
                      velocity of a nonlinearly sorbing solute},
      journal      = {Journal of hydrology},
      volume       = {302},
      issn         = {0022-1694},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {PreJuSER-44581},
      year         = {2005},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {This study investigated the variation of retardation factor
                      and velocity of a lithium (a nonlinearly sorbing solute)
                      plume in relation to the variation of lithium concentration
                      in the plume by using field-measured breakthrough curves
                      (BTCs). A concentration-dependent/time-dependent retardation
                      factor (R-c) and a cell-averaged retardation factor ((R)
                      over bar) (please see Section 2.1 for definitions) of the
                      lithium plume were derived from the BTCs. The
                      concentration-dependent retardation factor, R., is initially
                      large at low concentration of the lithium plume, and it
                      drops steadily with the increasing concentration to a
                      minimum value at the highest concentration of the plume.
                      After the peak concentration has passed away, R-c increases
                      gradually with the decreasing concentration of the plume.
                      The cell-averaged retardation factor, (R) over bar, is close
                      to a section of the concentration-dependent retardation
                      factor, which is obtained at the few highest concentrations
                      in a BTC. (R) over bar varies widely, especially at the low
                      concentrations of the lithium plume, with the distribution
                      coefficient K of lithium and exponent n of the Freundlich
                      isotherm for lithium adsorption. Considerable variations in
                      (R) over bar are also observed between the BTCs at different
                      depths in a monitoring well. A single average retardation
                      factor defined for a monitoring well is thus confounded with
                      the variation of concentrations in the BTCs at different
                      depths. The instantaneous velocity of the lithium plume,
                      called the retarded velocity/local velocity (please see
                      Section 2.2 for definitions), changes with the concentration
                      of the plume in an opposite way from the retardation factor.
                      The retarded velocity is, of necessity, always lower than
                      the constant velocity of the groundwater flow in the
                      aquifer. A cell-averaged velocity of the lithium plume,
                      derived from the cell-averaged retardation factor, is an
                      average velocity of the plume at any point on the travel
                      path for the entire breakthrough time of the plume. This
                      velocity provides little information about the transport
                      processes of lithium in the aquifer. (C) 2004 Elsevier B.V.
                      All rights reserved.},
      keywords     = {J (WoSType)},
      cin          = {ICG-IV},
      ddc          = {690},
      cid          = {I:(DE-Juel1)VDB50},
      pnm          = {Chemie und Dynamik der Geo-Biosphäre},
      pid          = {G:(DE-Juel1)FUEK257},
      shelfmark    = {Engineering, Civil / Geosciences, Multidisciplinary / Water
                      Resources},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000226396500008},
      doi          = {10.1016/j.jhydrol.2004.06.041},
      url          = {https://juser.fz-juelich.de/record/44581},
}