2.19 The dissolved oxygen (DO) concentration is measured as 0.5 mg/L in the anoxic zone and 8
mg/L near the end (of a 108-ft–long aerated biological reactor). What are these two DO
concentrations in units of (a) ppmm, (b) moles/L?
Solution:
2.20 Assume that the average concentration of chlordane – a chlorinated pesticide now banned in
the United States – in the atmosphere above the Arctic Circle in Norway was found to be 0.6
pg/m3. In this measurement, approximately 90 percent of this compound is present in the gas
phase; the remainder is adsorbed to particles. For this problem, assume that all the compound
occurs in the gas phase, the humidity is negligibly low, and the average barometric pressure is 1
atm. Calculate the partial pressure of chlordane. The molecular formula for chlordane is
C10C18H6. The average air temperature through the period of measurement was -5°C.
Solution:
First, find concentration in ppmv. The molecular weight equals 409.8.
2.21 What is the concentration in (a) ppmv, and (b) percent by volume, of carbon monoxide (CO)
with a concentration of 103 µg/m3? Assume a temperature of 25°C and pressure of 1 atm.
Solution:
2.22 Ice resurfacing machines use internal combustion engines that give off exhaust containing
CO and NOx. Average CO concentrations measured in local ice rinks have been reported to be as
high as 107 ppmv and as low as 36 ppmv. How do these concentrations compare to an outdoor-
air-quality 1-h standard of 35 mg/m3? Assume the temperature equals 20°C.
Solution:
2.23 Formaldehyde is commonly found in the indoor air of improperly designed and constructed
buildings. If the concentration of formaldehyde in a home is 0.7 ppmv and the inside volume is
800 m3, what mass (in grams) of formaldehyde vapor is inside the home? Assume T = 298 K, P
= 1 atm. The molecular weight of formaldehyde is 30.
Solution:
3
3
0.7 30 1,000 1
/
0.08205 298
×× ×
=−
×
−
v
gL
ppm atm
mole m
gm L atm K
mole K
µ
2.24 The concentration of ozone (O3) in Beijing on a summer day (T = 30°C, P = 1 atm) is 125
ppbv. What is the O3 concentration in units of (a) µg/m3, and (b) number of moles of O3 per 106
moles of air?
Solution:
2.25 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:
2.26 An empty balloon is filled with exactly 10 g of nitrogen (N2) and 2 g of oxygen (O2). The
pressure in the room is 1 atm and the temperature is 25°C. (a) What is the oxygen concentration
in the balloon in units of percent by volume? (b) What is the volume of the balloon after it’s
blown up, in L?
Solution:
2.27 A gas mixture contains 1.5 × 10-5 mole CO and has a total of 1 mole. What is the CO
concentration in ppmv?
Solution:
2.28 “Clean” air might have a sulfur dioxide (SO2) concentration of 0.01 ppmv, while “polluted”
air might have a concentration of 2 ppmv. Convert these two concentrations to µg/m3. Assume a
temperature of 298 K.
Solution:
2.29 Carbon monoxide (CO) affects the oxygen carrying capacity of your lungs. Exposure to 50
ppmv CO for 90 min has been found to impair one’s ability to time/interval discriminate; thus,
motorists in heavily polluted areas may be more prone to accidents. Are motorists at a greater
risk to accidents if the CO concentration is 65 mg/m3? Assume a temperature of 298 K.
Solution:
2.30 Humans produce 0.8 to 1.6 L of urine per day. The annual mass of phosphorus in this urine
on a per capita basis ranges from 0.2 to 0.4 kg P. a) What is the maximum concentration of
phosphorus in human urine in mg P/L? b) What is the concentration in moles P/L? c) Most of
this phosphorus is present as HPO42-. What is the concentration of phosphorus in mg HPO42–/L?
Solution:
2.31 Assume 66% of phosphorus in human excrement in found in urine (the remaining 34% is
found in feces). Assume humans produce 1 L of urine per day and the annual mass of
phosphorus in this urine is 0.3 kg P. If indoor water usage is 80 gallons per capita per day in a
single individual apartment, what is the concentration (in mg P/L) in the wastewater that is
discharged from the apartment unit? Account for phosphorus in urine and feces.
Solution:
2.32 A dry cleaning facility owned by JMA Inc. has been observed to have impacted 6,000
gallons of groundwater with 0.70 pounds of tetrachloroethylene (PCE). Assuming all the PCE is
present in the dissolved phase and the chemical pollutant is evenly distributed throughout the
impacted volume of the groundwater, what is the concentration of PCE In groundwater in ppm?
2.33 A dry cleaning facility has been observed to have impacted 20 m3 of a saturated
groundwater aquifer (porosity of 0.30) with 0.70 pounds of tetrachloroethylene (PCE) (molecular
formula of C2Cl4). A bioremediation system is utilized which degrades all of the PCE present to
ethene through the process of reductive dechlorination (molecular formula of ethene is C2H4).
How many moles/L of chlorine are present in the impacted volume of aquifer after all the PCE is
dechlorinated? Porosity is defined as the number of voids (that can fill with air or water)
divided by the volume (that includes voids and solids).
Solution:
2.34 Copper was used as a fungicide in citrus orchards which are being considered for a
stormwater retention project as part of the Everglades restoration effort. Copper accumulates in
apple snails, a primary food source of the federally endangered bird called the Everglades Snail
kite. The professional engineer at BTA Inc. is considering two former citrus production areas for
construction of a stormwater treatment area – a 1,500-acre site with soils having a copper content
of 220 ppm and a 2,000-acre site with 160 pounds of copper uniformly distributed in the top 6-8
inches of soil. Which site would our female engineer recommend for the project if the ecological
threshold to support the Everglades Snail Kite is 85 mg Cu/kg? Ecological threshold means that
the soil concentration of copper can’t exceed this value. Assume the plow layer of soil (upper 6-
8 inches) for the 2,000-acre site weighs 2,000,000 pounds.
Solution: