CHAPTER 4 SOLUTIONS
1. a. Using Eq. (4.14) and assuming no sinks for CO and a negligible
concentration of CO outside:
b. Given the assumptions of no sinks for CO and a negligible CO
concentration outside the room, use Eq. (4.15):
c. After the heater’s fuel supply is depleted, the CO concentration in
the room will decay exponentially, with a first-order decay rate of
2. Given that the total source strength for SO
2
is known, and the mixing
height is well-defined, a simple box model can be used to estimate the
steady-state SO
2
concentration in the factory town’s air:
e111CHAPTER 4 SOLUTIONS
3. a. To estimate the maximum steady-state zinc concentrations in
the air at ground level, use Eq. (4.16). Note that this equation
b. To estimate steady-state concentrations of zinc at ground level at
various distances from the plume centerline, the horizontal
Gaussian distribution factor must be calculated from Eq. (4.17a):
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Then the equation to estimate the zinc concentration can be
written as:
4. a. From Table 4.3, at 18 C, the vapor pressure of water is 15.5 mm Hg.
b. If a dry adiabatic lapse rate is assumed (Eq. 4.12), the dew
5. To determine the mixing height, draw a line with a slope equal to
the dry adiabatic lapse rate, beginning at the temperature and
6. a. Region A is more likely to encounter precipitation than Region B.
e113CHAPTER 4 SOLUTIONS
b. In Region C, wind direction is likely to be from the northwest.
c. Region F is more likely to be subject to air pollution because it is in
7. The steady-state concentration of radon gas can be estimated using
the mass balance expression of Eq. (4.14):
According to EPA guidelines, no action is required to increase the
ventilation rate.
If the ventilation rate is lowered to 0.3 air changes per hour:
8. Given that the wind speed is greater than 6 m/sec, and that
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9. The oxidation of NO to NO
2
in automobile emissions will most likely
increase the amount of ozone in the air; the emitted NO
2
will react in
the sunlight to form NO and a free oxygen atom, which is readily
2
10. a. To estimate the dry deposition rate of nitric acid aerosol, Eq. (4.31)
can be used. Assuming a deposition velocity of approximately
1 cm/sec:
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b. Equation (4.31) can also be used to estimate the dry deposition
rate of sulfate aerosol. Again assuming a deposition velocity
of approximately 1 cm/sec, the annual flux density is
approximately:
11. The adiabatic chart in Fig. 4.7 can be used to estimate the
temperature on the leeward side of the mountains. Because foggy
12. a and b. To calculate the amount of ethene remaining in the test
chamber after one hour, first calculate the pseudo-first-order rate
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c. The pseudo-first-order rate constant in the atmosphere near the
Earth’s surface can be approximated by using a similar equation to
13. a. A stack 125 ft high is approximately 38 m high. From Fig. 4.28, the
standard deviations of the distribution of chemical mass about the
b. Assuming unlimited mixing height, Eq. (4.16) can be used to
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The rate of chemical emission, assuming short tons, not metric
tons, is:
6m=secðÞ3600 sec=hrðÞ
2p300 m 90 m ¼6:8105gSO
m3
14. a. Given the existence of several metalworking industries in the
area, and given a low effective mixing height, it is not
unreasonable to assume that the various plumes of 1,1,1-TCA
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b. The primary sink for this chemical in the air is probably
15. a. To estimate the dry deposition rate of sulfate aerosol, Eq. (4.31)
can be used. Assuming a deposition velocity onto the forested
watershed of approximately 1 cm/sec:
b. On an annual basis, the flux density of sulfate aerosol to this
watershed due to dry deposition is approximately:
c. To determine whether the watershed is acting as a net source or
sink of sulfate, convert the stream water concentration of sulfate
into a flux leaving the watershed by using the annual runoff depth:
16. Increased levels of nitrate deposition in precipitation (wet deposition
of nitrate) may exacerbate several regional or global-scale problems,
such as:
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17. a. Given the plane’s speed and the distance to friendly territory, the
amount of time the pilot needs to stay aloft can be estimated:
To estimate the location of the cloud base, the dew point of the
thermal must be used in conjunction with the dry adiabatic lapse
rate, which describes the rate at which the air cools upon rising.
b. Once condensation has occurred, a wet adiabat must be followed
to estimate the height at which the air temperature cools to 0 C
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18. In general terms, if an air mass contains moisture, and it is raised to a
height at which the temperature equals the dewpoint, condensation
can occur and precipitation may result. The three listed
meteorological features have different mechanisms by which the
air mass is elevated.
19. a. To reduce nitric oxide to nitrogen gas, the following reaction
must be balanced:
e121CHAPTER 4 SOLUTIONS
b. This NO reducing capacity would come from the oxidation of
CO and hydrocarbons in the exhaust. For example, in the
20. a. If the container is totally airtight, the input and output terms
of Eq. (4.14) are zero. There is also no source term after the
initial concentration inside the container is established. To solve
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b. With a nonzero ventilation rate, the output term in Eq. (4.14) is no
longer zero:
c. With the container being airtight, the input and output terms of
21. a. First estimate the concentration of gasoline vapor above the
roadway depression by using Eq. (2.38):
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b. To estimate the gasoline vapor concentration in air downwind,
Eq. (4.16) can be used. First estimate the rate of gasoline vapor
emission using the pool area and the flux density estimated above:
22. The vapor pressure of water in air at 12 C with a RH of 60% can be
estimated from Table 4.3:
vapor pressure ¼0:60 10:52 mm Hg ¼6:3mmHg
The dew point for air with a vapor pressure of water of 6.3 mm Hg
can be estimated from Table 4.3 to be approximately 4.5 C.
a. To estimate whether the pilot will need to fly on instruments due
to clouds, estimate the height at which the dew point will be
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23. a. For cloudy, nighttime conditions with a windspeed of 3.5 m/sec,
the Pasquill stability category from Table 4.5 is D. Using
b. From Fig. 2.13, a gravitational settling velocity for a submicron-
sized fine particle is approximately 10
3
cm/sec. However, dry
deposition for aerosols is typically in the range of 1 cm/sec.
24. a. When insolation is slight and the windspeed is 2.5 m/sec, the
Pasquill stability category from Table 4.5 is C. Using Fig. 4.28, s
y
Then use Eq. (4.16) to estimate the maximum SO
2
concentration:
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b. If the wind shifts by 5, the distance between the original point
and the new downwind point is y, the distance along a horizontal
axis perpendicular to the wind. ycan be estimated as:
25. First use Eq. (4.32) to estimate the flux density of SO
2
to the pool in
units of (mol/(m
2
week)):
26. a. A pseudo-first-order rate constant can be estimated as:
b. Using Eq. (1.21), the half-life of NO
2
due to photolysis is:
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27. a. Use Fig. 4.7 to estimate the altitude at which hail forms. Follow
b. Stokes’ law can be used to estimate the settling velocity
for the hail, which in turn provides an estimate of the
28. a. A mass balance expression for COS can be written by
assuming that the troposphere is a well-mixed box. Consider
the mass balance expression in Eq. (4.14):
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A mass balance expression thus can be written as:
29. a. On a bright, sunny day, insolation is strong; with a windspeed
of 4 m/sec, the Pasquill stability category from Table 4.5 is
b. On an overcast night with a windspeed of 4 m/sec, the Pasquill
stability category from Table 4.5 is D. Again using Fig. 4.28, s
y
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