Geoscience Reference
In-Depth Information
Figure 12.5
Linear and Langmuir isotherms of sorption.
Eq. (12.100) is the general formof the Langmuir isotherm. Both linear and Langmuir
isotherms are depicted in Fig. 12.5. One can see that when
C
s
C
s
,max
, Eq. (12.99)
reduces to Eq. (12.95) and the Langmuir isotherm becomes the linear isotherm.
Using Eqs. (12.94) and (12.100) yields the fractions of the dissolved and sorbed
contaminants in the equilibrium state:
1
1
1
2
C
s
,max
C
t
1
k
D
r
sw
f
d
=
−
+
C
s
,max
C
t
1
1
2
1
k
D
r
sw
−
1
4
C
s
,max
C
t
1
k
D
r
sw
±
−
+
f
s
=
1
−
f
d
(12.101)
The parameters
k
ad
,
k
de
,
k
D
, and
C
s
,max
vary with contaminant species, sedi-
ment properties, and water conditions. They are usually measured through sorption
and desorption experiments. The estimation of these parameters can be found in
Thomann and Mueller (1987), Chapra (1997), Furumai and Ohgaki (1989), Chao
et al
. (2006), etc.
12.3.2 Contaminant transport in water column
12.3.2.1 Non-equilibrium partition model
Fig. 12.6 shows the general transport and transformation patterns of contaminant con-
stituents in both water column and sediment bed. Changes in concentrations of the
dissolved and sorbed contaminants in the water column are caused by advection, dif-
fusion, external loading, sorption, desorption, and decay. Additionally, the settling of
