Geoscience Reference
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C a
Air
Water
C w
D
Sediment
FIGURE 4.10 Volatilization.
where
c w
=
dissolved organic chemical concentration in water [
µ
g l −1 ]
c a
=
concentration of organic chemical in air [
µ
g l −1 ].
H
=
Henry's law constant [atm m 3 mole −1 ]
R
=
universal gas constant (8.206
×
10 −5 ) [atm m 3 mole −1 K −1 ]
T
=
water temperature [K]
D
=
water depth [m]
K v
=
volatilization transfer rate constant [m day −1 ]
The rate constant K v is the reciprocal of the total interface film resistances, and
depends on the intensity of turbulence in the water body and the overlying atmo-
sphere. 78
K V
=
( R L
+
R G ) −1
=
[ K L −1
+
( K G
( H / RT K ) −1 ] −1
(4.45)
where
K V
=
volatilization transfer rate constant [m day −1 ]
R L
=
liquid phase resistance [day m −1 ]
R G
=
gas phase resistance [day m −1 ]
K L
=
liquid phase transfer coefficient [m day −1 ]
K G
=
gas phase transfer coefficient [m day −1 ]
H
=
Henry's law coefficient for the air-water partitioning of the chemical
[atm m 3 mole −1 ]
R
=
universal gas constant (8.206
×
10 −5 ) [atm m 3 mole −1 K −1 ]
T K
=
water temperature [K −1 ]
4.2.4.2
Sorption
Several models have been proposed to mathematically represent sorption isotherms. 45
Among the most popular are:
Langmuir isotherm:
v
=
( v m b c d )/(1
+
b c d )
(4.46)
 
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