Second-Order Transport Modeling - Transport and Fate of Chemicals in Soils: Principles and Applications - page 173

C o = 100

100

75

50

25

10

10

5

1

2

1

Windsor

0.1 0 8 6

144 192 240 288 336

Time, h

FIGURE 6.13
Time-dependent retention of Cr(VI) by Windsor soil. Closed squares are the data points and
solid lines are second-order model predictions for different initial concentration curves ( C o = 1,
2, 5, 10, 25, 50, 75, and 100 mg @ L -1 ). (From H. M. Selim and M. C. Amacher. 1997. Reactivity and
Transport of Heavy Metals in Soils . Boca Raton, FL: CRC Press. With permission.)

If the fraction of type 1 sites is small as was the case with the Olivier and
Windsor soils, then their contribution to the kinetic solute retention curve
will be small and indistinguishable at high solute concentrations. For the
Cecil soil where the fraction of type 1 sites was significant ( F = 0.224), the
five-parameter model version was superior to the three-parameter version

100

C o = 100

75
50

10

25

1

10
5 0.1

2

0.01

1

Cecil

0.0001 0 8 6

144
Time, h

192 240 288 336

FIGURE 6.14
Time-dependent retention of Cr(VI) by Cecil soil. Closed squares are data points and solid
lines are second-order model predictions for different initial concentration curves ( C o = 1, 2,
5, 10, 25, 50, 75, and 100 mg @ L -1 ). (From H. M. Selim and M. C. Amacher. 1997. Reactivity and
Transport of Heavy Metals in Soils . Boca Raton, FL: CRC Press. With permission.)