Agriculture Reference
In-Depth Information
80
SOM Model
with Concurrent Irreversible Reaction
Sharkey Soil
60
40
C
o
= 100 mg/L
20
80
40
20
0
0 0
100
150
200
250 00
350 00
450 00
Time, Hours
Sharkey Soil
SOM Model
with Consecutive Irreversible Reaction
100
80
60
C
o
= 100 mg/L
40
80
20
40
0
20
0 0
100
150
200
250 00
350 00
450 00
Time, Hours
FIGURE 6.21
Experimental results of As(V) concentration in soil solution for Sharkey soil versus time for
all values of
C
o
. Dashed curves were obtained using the second-order model with concurrent
(top figure) and consecutive (bottom figure) irreversible reactions.
that incorporation of an equilibrium sorbed phase into the various model
versions for As(V) predictions should be avoided.
The success of the SOM approach in describing As(v) retention results
is significant since the SOM formulation described in this chapter has not
been applied to metalloid elements like arsenic. Previous use of the SOM
formulation, which included a partitioning of the sites, indicated that for
Cr and Zn the rate coefficients were highly concentration dependent (Selim
and Amacher, 1988; Hinz, Buchter, and Selim, 1992). Selim and Ma (2001)
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