EMS 131 Chemical Mass Balance Questionnaire
EMS 131 Chemical Mass Balance Questionnaire
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A small town in California has a factory that employs 50% of the town’s people and is the only “smoke-stack” in town. The only other source of particulate matter is car and truck traffic. The town council wants to know how much the factory and the transportation emissions are contributing to the town air pollution so that they can develop a strategy to reduce air pollution. The town obtained the following data from a consultant: 24-hour samples of PM2.5 every third day during 2013, stack sampling data on the factory to determine emissions % from the factory and evaluation of the peer-reviewed literature to determine the emission rates of pollutants from transportation sources.
The concentrations (g/m3) of species measured on August 25, 2013 were:
Species Concentration (μg/m3)
OC 30
EC 10
Metals 21
Total PM2.5 61
From the stack sampling and literature review, the following has been determined.
Emissions (%)
Species Source 1 (Transportation) Source 2
(Factory)
OC 60 20
EC 25 10
Metals 15 70
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Questions:
a. Write the generalized CMB equation using only symbols. Define each variable. (5 pnts)
b. Write CMB equations for OC, EC and metals for August 25, 2013. (5 pnts)
c. Perform least squares analysis on the CMB equations and determine Mtransportation and Mfactory (show your work to receive full credit) (5 pnts)
d. Calculate the percentage (%) of the PM2.5 mass measured on August 25 due to each source. (5 pnts)
f. Calculate the amount (g/m3) of OC due to each source. (5 pnts)
g. Calculate the percentage (%) of measured metals due to each source. (5 pnts)
h. Discuss the conclusions you can draw from this analysis. (5 pnts)
2. For a box model problem, what effect (increase, decrease or no effect) do the following have on the concentration exiting the box.
a. increased wind speed (5 pnts)
b. increased emission rate (5 pnts)
c. decreased background concentration (5 pnts)
d. decreased inversion height (mixing height in the atmosphere) (5 pnts)
3. A city has a downtown area surrounded on two sided by suburbs. Carbon monoxide concentrations are of concern for this city and you decide to use the box model to determine CO concentrations. The city may be considered to consist of three parallel strips, located perpendicular to the wind. For all of the strips the wind velocity, u, equals 5 m/s. The properties of each of the strips are described in the following table
The length of the side of the box parallel to the wind direction, km Emission rate q, g/s/km2 Mixing height, H, m
Upwind suburbs 5 20 500
Downtown 3 150 1000
Downwind suburbs 5 10 500
Assume that the box model applies to each of the strips. The background concentration Cb in the air entering the upwind suburbs is 2 g/m3. For each part of the city, calculate the concentrations into and out of the box. (10 pnts) (Drawing a picture of the three boxes may help you visualize this problem.)