Geoscience Reference
In-Depth Information
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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