Chapter 11. Air Resources Engineering
11.1 Carbon monoxide (CO) is measured to have a concentration of 103 µg/m3. What is
the concentration in (a) ppmv, (b) ppbv, and, (c) percent by volume? Assume a
temperature of 25°C and pressure of 1 atm.
Solution:
11.2 If the atmospheric mass concentrations of nitrogen monoxide (NO) and nitrogen
dioxide (NO2) are 90 and 120 µg/m3, respectively, what is the NOx concentration in
ppbv? Assume a temperature of 30ºC and pressure of 1 atmosphere.
Solution:
11.3 If the mass concentration of particulate matter is 12,500 µg/m3, report this
concentration as the number concentration (# particles/cm3). Assume spherical particles
of 0.5 µm diameter with density of liquid water (1 g/cm3).
Solution:
Use unit conversions from what is provided in the problem.
11.4 Formaldehyde is commonly found in the indoor air of improperly designed and
constructed buildings. If the concentration of formaldehyde in a home is 1.2 ppmv and the
inside volume is 600 m3, what mass (in grams) of formaldehyde vapor is inside the
home? Assume T = 298 K and P = 1 atm. The molecular weight of formaldehyde is 30.
Solution:
11.5 The National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (SO2) is
0.14 ppmv (24–hr average). (a) What is the concentration in µg/m3 assuming an air
temperature of 25oC? (b) What is the concentration in moles SO2 per 106 moles of air?
Solution:
11.6 Table 11.5 provided information that suggested “clean” air might have a sulfur
dioxide (SO2) concentration of < 30 ppbv , while polluted air might have a concentration
of 1 ppmv. Convert these two concentrations to µg/m3. Assume a temperature of 298 K.
(note the difference units of concentrations, ppmv versus ppbv).
Solution:
11.7 Carbon monoxide (CO) affects the oxygen-carrying capacity of your lungs.
Exposure to 50 ppmv CO for 90 minutes has been found to impair one’s ability to
discriminate stopping distance; therefore, motorists in heavily polluted areas may be
more prone to accidents. Are motorists at a greater risk of accidents if the CO
concentration is 65 mg/m3? Assume a temperature of 298 K.
Solution:
11.8 Diesel engines emit very fine soot particles. In the atmosphere, these soot particles
often agglomerate with other particles as they “age.” Assume the agglomerated soot
particles are initially suspended at a height of 2.2 m. They are spherical (diameter = 0.5
µm) and have a density of 1.1 g/cm3. (a) Calculate the terminal settling velocity of the
soot particles. (b) How many hours will the soot particles remain suspended before
settling by gravity to the ground? The density of air is 1.2 kg/m3 and its fluid viscosity is
1.72 × 10-4 g/cm–sec.
Solution:
11.9 This problem allows you to think about how exposure impacts the concentration of
air pollutants you are exposed to. (a) Maintain a diary for one full day and record all the
locations you visit. Include the times of entry and exit for each location. Also record any
interesting air quality information for each location. Calculate the percentage of time
spent in each type of location. Summarize the data in a table. (b) In which location did
you spend the most amount of time? The least? (c) Calculate the 24–hr time integrated
average exposure concentration (units of µg/m3) to airborne particles based on your
recorded activity patterns, using the average airborne PM10 concentration for different
locations provided below.
Location
Average Airborne PM
10
Concentration (µg/m
3
)
Home
90
Office–Factory
40
Bar–Restaurant
200
Other Indoor
20
In a Vehicle
45
Outdoors
35
(a) (b) Students should be developing this type of table from the data entered into
their dairy for their 24 hour period. Their raw data from the diary can be attached
to the problem solution as an appendix. (c) Students can the use the table below
to determine the “time averaged” concentration
Location
Average Airborne
PM10
Concentration (µg/m
3
)
Time spent in
Location (mins)
Home
90
Office–Factory
40
Bar–Restaurant
200
Other Indoor
20
In a Vehicle
45
Outdoors
35