Agriculture Reference
In-Depth Information
1.0
1.0
0.8
0.9
0.8
0.6
α = 0.35 d
-1
q
= 41 cm d
-1
0.7
0.0
3
4
5
6
0.4
F
= 0.15
0.45
0.75
0.2
0.0
0
2
4
6
8
102 4
Pore Volumes
FIGURE 8.7
Breakthrough of bromide in a structured soil. Simulations are based on the mobile-immobile
model for different values of the fraction of the mobile water (
F
).
Schulin, and Flühler (1987) successfully used such estimates of
f
for a well-
aggregated soil. Estimates for α were obtained using:
1
−µ
α=
15
a
Θ
D
(8.55)
2
a
where μ = Θ
m
/Θ and
D
a
is the molecular diffusion coefficient in a soil con-
sisting of uniform aggregates of radius
a
. The above equation was derived
by Parker and Valocchi (1986) and is based on time-moment analysis for
1.0
1.0
0.8
0.8
0.6
0.6
F
= 0.45
q
= 41 cm d
-1
0.0
3
4
5
6
0.4
α = 0.08 d
-1
0.35 d
-1
0.62 d
-1
0.2
0.0
0
2
4
6
8
10
12
14
Pore Volumes
FIGURE 8.8
Breakthrough of bromide in a structured soil. Simulations are based on the mobile-immobile
model for different values of the transfer coefficient (α).
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