Environmental Engineering Reference
In-Depth Information
TABLE 3.3
Henry's Law Constants for Stabilizer and Chlorinated Solvent Compounds
Compound
H
[(atm m
3
)/mol]
H
C
(dimensionless)
b
References
Cyclohexane
1.50 × 10
−1
6.14
Bocek (1976)
Perchloroethylene
Gossett (1987)
1.77 × 10
−2
7.24 × 10
−1
Trichloroethylene
Leighton and Calo (1981)
9.85 × 10
−3
4.03 × 10
−1
Methyl chloroform
Lyman (1990), Dilling et al. (1975)
8.00 × 10
−3
3.27 × 10
−1
Dichloromethane
Leighton and Calo (1981)
3.25 × 10
−3
1.33 × 10
−1
tert
-Amyl alcohol
Butler et al. (1935)
7.30 × 10
−4
2.99 × 10
−2
1,2-Butylene oxide
Bogyo et al. (1980)
1.80 × 10
−4
7.37 × 10
−3
Nitroethane
Gaffney et al. (1987)
4.76 × 10
−5
1.95 × 10
−3
Epichlorohydrin
Lyman (1990)
3.00 × 10
−5
1.23 × 10
−3
Nitromethane
Lyman (1990)
2.59 × 10
−5
1.06 × 10
−3
1,3-Dioxolane
Hine and Mookerjee (1975)
2.40 × 10
−5
9.82 × 10
−4
sec
-Butyl alcohol
Snider and Dawson (1985)
9.06 × 10
−6
3.71 × 10
−4
tert
-Butyl alcohol
Altschuh et al. (1999)
9.05 × 10
−6
3.70 × 10
−4
1,4-Dioxane
Park et al. (1987)
4.80 × 10
−6
1.96 × 10
−4
Triethanolamine
Hine and Mookerjee (1975)
1.00 × 10
−7
4.09 × 10
−6
a
Nonitalics compounds are stabilizers. Italics compounds are chlorinated solvents; these are listed for comparison to show
whether the stabilizer is likely to evaporate with the solvent or remain behind in the soil where it can be leached down to
groundwater.
b
Dimensionless values of Henry's law constants calculated from literature values by using Equation 3.8.
turbulent air l ows, and a thin layer of stagnant water beneath the water surface, below which water
l ows. In “thin-i lm theory,” the thickness of the static air layer above the water surface is approxi-
mated as 1 mm, whereas the stagnant water layer is taken to be 0.1 mm thick (Schwarzenbach et al.,
1993). Molecular diffusion is the dominant transport mechanism in the thin i lms above and below
the water surface, whereas turbulent diffusion is active in the l uids above and below the thin i lms.
Equation 3.9 provides an expression for l ux density (Hemond and Fechner, 1994):
È
1
˘ È
C
˘
J
=-
C
-
a
,
(3.9)
Í
˙ Í
˙
d
/
D
+ d
/(
D
◊
H
)
w
H
Î
˚ Î
˚
ww a
a
where
J
is the l ux density(
M
/
L
2
T
),
δ
w
is the thickness of the hypothetical thin water layer (
L
),
D
w
is
the molecular diffusion coefi cient for the chemical in water (
L
2
/
T
),
δ
a
is the thickness of the hypo-
thetical thin air layer (
L
),
D
a
is the molecular diffusion coefi cient for the chemical in air (
L
2
/
T
),
H
is the Henry's law constant (dimensionless),
C
w
is the chemical concentration in water (
M
/
L
3
),
C
a
is
the chemical concentration in air (
M
/
L
3
), and
L
,
M
, and
T
represent any consistently applied units of
length, mass, and time.
Because wind speed affects the thickness of the air i lm above water and water l ow or circula-
tion affects the thickness of the water i lm below the interface, this l ux density equation should only
be used for rough approximations or to compare relative mass l ux rates. The air i lm is 10 or more
times thicker than the water i lm, and the molecular diffusion coefi cient for a compound in air is
about 10,000 times higher than its molecular diffusion coefi cient in water. If the air concentration
of the compound of interest is zero, then the l ux density is directly proportional to the magnitude
of the compound's Henry's law constant and its concentration in water (Thomas, 1990). Table 3.3
can therefore be interpreted to provide an approximation of the relative magnitude of mass transfer
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