Mobile, Immobile, and Multiflow Domain Approaches - Transport and Fate of Chemicals in Soils: Principles and Applications - page 293

0.8

Mahan I-large pulse

(a)

v = 2.02 cm hr -1

0.6

Exp. data

0.4

One domain
Two domain

0.2

0.0 0

1 2 3 4

0.8

Mahan II-large pulse

(b)

0.6

v = 3.82 cm hr -1

0.4 Exp. data

One domain
Two domain

0.2

0.0 0

1 2 3 4

0.8

Mahan III-large pulse

(c)

0.6

v = 5.28 cm hr -1

Exp. data
One domain
Two domain

0.4

0.2

0.0 0

1 2 3 4

Pore Volume (V/V o )

FIGURE 8.21
Tritium breakthrough curves (BTCs) for three Mahan soil columns under different fluxes. Solid
and dashed curves are fitted BTCs with the one- and two-flow domain models, respectively.

tailing side, which became more obvious as the velocity increased. These
observed humps or peaks suggest a nonuniform flow domain in such a
soil. The humps or second peaks were more distinct for the tritium BTCs
shown in Figure 8.22. In fact, the peaks developed into a bimodal peak at
the highest flow velocity (bottom of Figure 8.22). All three soil columns
shown in Figure 8.22 received a small pulse of tritium of 0.02 pore vol-
umes. Based on the BTCs shown in Figure 8.22, it is apparent that the