Environmental Engineering Reference
In-Depth Information
6.27
2
The air above the city of Baton Rouge, Louisiana, can be considered to
be well-mixed to a depth of 1 km over an area 10
×
10 km
2
. CO is being
emitted by both stationary and mobile sources within the city at a rate of
10 kg/s. Assume CO is a conservative pollutant. (a) For a wind velocity of
5 m/s in the city, what is the steady-state concentration of CO in the city?
(b) If after attaining steady state, the wind velocity decreases to 1.5 m/s,
what is the new steady-state concentration?
6.28
2
Peroxyacyl nitrate (PAN) is a component of photochemical smog. It is
formed from aldehydes by reaction with OH as follows:
CH
3
CHO
+
OH
•
−→
CH
3
CO
+
H
2
O
CH
3
CO
•
+
O
2
−→
CH
3
CO
(
O
2
)
•
CH
3
CO
(
O
2
)
•
+
NO
2
+
M
CH
3
C
(
O
)
O
2
NO
2
+
M
Derive an expression for the production of PAN.
6.29
1
TheannualproductionrateofCH
3
Clis0.3Tg/yandhasanaveragemixing
ratio of 650 pptv.
What is its average residence time in the atmosphere?
6.30
2
Consider a lake 10
8
m
2
of surface area for which the only source of phos-
phorus is the effluent from a wastewater treatment plant. The effluent flow
rate is 0.4 m
3
/s and has a phosphorus concentration of 10 g/m
3
. The lake is
also fed by a stream of 20 m
3
/s flow with no phosphorus. If the phosphorus
settling rate is 10 m/y, estimate the average steady-state concentration of
P in the lake. The depth of the lake is 1 m.
6.31
2
An accident on a highway involving a tanker truck spilled 5000 gallons
of 1,2-dichloroethene (DCA) forming a 2500-m
2
pool. DCA has a vapor
pressureof0.1 atmat298 K.Theairtemperatureis25Candthewindspeed
averaged 4 m/s. The accident occurred on a sunny afternoon. Estimate the
distance downwind of the spill that would exceed the worker standard
exposure limit of 1 ppmv for DCA.
6.32
2
In a poorly ventilated hut in a third world country, logs are burnt to supply
heat for cooking purposes. The total volume of the hut is 1000 m
3
. Log
burning releases CO at the rate of 2 mg/h. The air exchange rate is 0.1 h
−
1
.
(a) What is the CO concentration after 2 h of cooking inside the hut? (b)
Compare the steady-state indoor CO concentration with the U.S. ambient
air quality criteria of 0.05 ppmv.
6.33
2
In 1976, a tragic release of one of the most toxic compounds known
to man (dioxin, i.e., 2,3,7,8-tetrachlorodibenzo-
p
-dioxin) occurred in
Seveso, Italy. The plant was manufacturing 2,4,5-trichlorophenol from
1,2,4,5-tetrachlorobenzene when the reaction ran away. The reactor over-
pressurized and the relief system opened for 5 min during which time 2 kg
of dioxin escaped into the atmosphere through the plant's roof. The wind
speed was 2 m/s and leak occurred on an overcast day. What is the likely
concentration 10 km from the plant site?
6.34
2
ConsiderthecityofBatonRouge,Louisiana,withapopulationof400,000.
The morning peak hour traffic is approximately 100,000 vehicles in an
area 300 km
2
with an average travel distance of 5 km from 7 a.m. to 10
a.m. daily. Assume each vehicle emits 2 g of CO for every 1 km traveled.
Determine the CO concentration in the atmosphere at 9 a.m. The initial
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