Environmental Engineering Reference
In-Depth Information
TABLE 3.1
Properties Affecting Volatilization Rates from Dry Soil for Chlorinated Solvents and
Selected Stabilizer Compounds
Vapor Density
Relative to Air
(g/cm
3
)
Evaporation Rate
Relative to Evaporation
Rate of Butyl Acetate
Molecular
Weight (g/mol)
Vapor Pressure
(mm Hg, 25°C)
Diffusivity
(cm
2
/s)
Compound
Stabilizers
1,4-Dioxane
88.1
38.09 [1]
3.03 [2]
0.229 [3]
2.7; 2.42 [4]
1,3-Dioxolane
74.08
70 at 20°C [5]
2.6 [7]
0.146
a
0.29 [18]
79 at 20°C [6]
tert
-Butyl alcohol
74.12
40.7 [1]
2.55 [8]
0.115
a
1.05 [19]
sec
-Butyl alcohol
74.12
18.3 [1]
2.6 [7]
0.101
a
1.3 [20]
tert
-Amyl alcohol
88.15
13.8 [1]
3
0.102
a
0.93 [21]
Epichlorohydrin
92.52
16.4 [1]
3.29 [8]
0.086 [3]
1.35 [6]
Nitroethane
75.08
20.8 [1]
2.58 [8]
0.165
a
1.2 [9]
Nitromethane
61.0
35.8 [1]
2.11 [8]
0.116
a
1.39 [10]
Cyclohexane
84.18
96.9 [11]
2.9 [12]
0.089
a
6.1 [12]
Triethanolamine
149.19
5.1 [13]
0.121
a
3.59 × 10
−6
[1]
<1 [13]
< 0.01 [13]
1,2-Butylene oxide
72.11
207 [3]
2.2 [7]
0.135 [3]
6.05 [16]
180 [14]
Solvents
Methyl chloroform
133.42
100 [15]
4.63 [2]
0.078 [3]
4.6 [15]
Dichloromethane
84.93
355 [15]
2.93 [16]
0.101 [3]
7.0 [15]
Trichloroethylene
131.39
60 [15]
4.53 [17]
0.079 [3]
3.0 [15]
Perchloroethylene
165.83
14 [15]
5.7 [17]
0.072 [3]
1.5 [15]
Sources:
[1] Daubert and Danner (1985); [2] Verschueren (1996); [3] USEPA (1998a); [4] USEPA (1981); [5] Riddick et al.
(1985); [6] Sax and Lewis (1987); [7] NFPA (1991); [8] Sax (1984); [9] Mackison et al. (1981); [10] NLM (2006);
[11] Chao et al. (1983); [12] Fisher Scientii c (1999); [13] Baker (2006); [14] Osborn and Scott (1980); [15] Dow
Chemical (2006); [16] Kirk and Othmer (1982); [17] Budavari (1996); [18] Beaujean (2007); [19] NIOSH (1978);
[20] Smallwood (1996); and [21] Cheremisinoff and Archer (2003).
a
Air diffusion constants displayed in italic font were estimated by using Equation 3.1 at 25°C.
where
E
is the emission rate (in cm
3
/s),
P
v
is the equivalent vapor pressure (in percent), where
P
v
vapor pressure (in mm Hg) divided by 760 mm Hg,
W
A
is the width of the area occupied by the
chemical (in cm),
L
A
is the length of the area occupied by the chemical (in cm),
D
a
is the diffusion
coefi cient of the chemical in air (in cm
2
/s), generally at 25°C,
v
is the wind speed (in cm/s),
W
c
/
W
is the weight fraction of the chemical in soil (in g/g), and
f
is the correction factor, where
f
=
(0.985-
0.00775
P
v
) and the range of
P
v
is 0-80%. The above volumetric emission rate can be converted to a
mass emission rate:
=
E
(MW)
_______
Q
=
G
,
(3.5)
where
Q
is the mass emission rate (in g/s),
E
is the volumetric emission rate (in cm
3
/s), MW is the
molecular weight (in g/mol), and the empirical conversion factor
G
is 24,860 cm
3
/mol (Dragun, 1988).
Many other empirical equations are available for estimating rates of volatilization; however,
given the many unknown aspects of ground surface conditions, the best use of such equations is to
determine the relative volatility and transfer rates among compounds instead of seeking absolute
transfer rates for an individual compound. Several equations for estimating rates of volatilization
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