Mobile, Immobile, and Multiflow Domain Approaches - Transport and Fate of Chemicals in Soils: Principles and Applications - page 288

1.2

Column VI, SOM, F9

1

SOM

0.8

SOM-MIM-α 1
SOM-MIM-α c

0.6

0.4

0.2

0 0510

15 20 25 30

V/V o

1.2

Column VII, SOM, F9

1

0.8

SOM

0.6

SOM-MIM-α 1
SOM-MIM-α c

0.4

0.2

0

0 5 10 15 20 25

V/V o

FIGURE 8.19
Measured and predicted atrazine BTCs for two columns of Sharkey clay soil having two
aggregate sizes. Top figure is for a 10-cm column packed with 4- to 6-mm soil aggregates with
no flow interruption, and bottom figure is for a 15-cm column packed with 2- to 4-mm soil
aggregates, 6 d flow interruption after pulse input. Predictions are based on the second-order
mobile-immobile model (MIM-SOM) and the original second-order model (SOM).

of the transfer rate coefficient (α) using Equations 8.14 and 8.16. These exam-
ples illustrate the capability of SOM-MIM in describing the BTC as well as
the influence of flow interruption. Based on these predictions, this modified
approach is a promising one since it accounts for retention and transport pro-
cesses based on physically as well as chemically heterogeneous reactions.
Figure 8.20 presents the BTCs from column experiments on arsenite trans-
port in Olivier loam, which displays diffusive fronts followed by exten-
sive tailing or slow release during leaching. Sharp decrease or increase in
arsenite concentration after flow interruption further verified the extensive
nonequilibrium condition. The arsenite BTC was simulated using coupled
physical and chemical nonequilibrium approaches. Here physical transport