Environmental Engineering Reference
In-Depth Information
4.6
3
Calculate the pH of an aqueous solution that is in equilibrium with
100 ppmv of CO
2
in the gas phase. The liquid-to-gas volume is 100:1.
The temperature is 298 K. The necessary parameters are given in the text.
4.7
1
100 mL of an aqueous solution containing 0.0004 mM
n
-nonane is placed
in a closed cylindrical vessel of inner diameter 5 cm and total height
10 cm. What fraction of
n
-nonane is present at the air-water interface
in this system? If the total height of the vessel is reduced to 5.5 cm, what
is the adsorbed fraction? Assume that
n
-nonane does not adsorb to the
vessel wall.
4.8
2
CFCs form an important class of atmospheric pollutants implicated in the
formation of ozone hole above the polar regions. These are no longer used
as a result of the worldwide agreement to ban their production and utiliza-
tion. One most common CFC was CCl
3
F (Freon-11) used as refrigerants.
If the dry air concentration of Freon-11 is 10
×
10
−
6
ppmv, determine
its concentration in atmospheric moisture as a function of water contents
ranging from 10
−
9
to 10
−
4
in a closed system.
K
aw
for Freon-11 is 5.
4.9
2
The surface area of an average aerosol in Baton Rouge, Louisiana, is
5
×
10
−
4
m
−
1
Determine the fraction of a polyaromatic hydrocarbon
(phenanthrene)adsorbedontheaerosol.Assumethatthevalueof
ρ
i
=
0.10
in the Junge's equation. The average temperature during the collection
of the aerosols was 73
◦
F on April 16, 1993. The average precipita-
tion was 0.46
of water. The average particulate phase concentration of
phenanthrene measured on that day was 0.21 ng/m
3
. The air-particulate
partition constant for phenanthrene was related to temperature in Kelvins
through the equation log
K
AP
=−
3423
/T
+
19. Determine the flux of
phenanthrene in
μ
g/m
2
/day.
4.10
2
The concentration of a pesticide (chlorpyrifos) measured in air from a
foggy atmosphere in Parlier, CA, was 17.2 ng/m
3
at about 25
◦
C. The
Henry's constant for chlorpyrifos at 25
◦
C is 170
×
10
−
6
and the air-water
partition constant is 6.4
×
10
−
4
at 12.5
◦
C. The average fog diameter is
1
μ
m. If the fog deposition rate is 0.2 mm/h, and the fog lasts for 4 h, what
is the surface flux of chlorpyrifos?
4.11
2
Liss and Slater (1974) determined that over the Atlantic Ocean the mean
atmospheric concentration of a CFC (CCl
3
F, Freon-11, molecular weight
137) is 50
×
10
−
6
ppmv, whereas the mean aqueous concentration is
7.76
×
10
−
12
cm
3
/mL. The overall aqueous-phase mass transfer coeffi-
cient was estimated as 11 cm/h. Determine the magnitude and direction
of freon flux? If the ocean surface area is 3.6
×
10
14
m
2
, and the total
annual flux of freon is 3
×
10
11
g, what fraction is contributed by the
Atlantic Ocean?
4.12
3
(a) The aqueous solubility of hexachlorobenzene is 5
μ
g/L. Estimate its
octanol-water partition constant. Use this information alone to cal-
culate the aqueous concentration that will be present in a sediment
suspension containing 100 mg of a sediment with an organic carbon
fraction of 0.02.
(b) If the equilibrium concentration is equal to the saturation aqueous
solubility, what is the sediment concentration?
(c) If the aqueous solution in (a) also contains 0.05 mol fraction
of ethanol, what is the value of the sediment-water partition
constant?
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