| Ozone:
Ground-Level Ozone
Simulation
Smog
City
There
exists on the Internet an exceptional simulation of the factors
involved in smog formation - Smog City. The simulation was
produced by the Sacramento Metropolitan Air Quality Management District
and allows users to change various parameters and observe the changes
in air quality that result.
The site has several pages with useful, concise information regarding
the simulation, so I will forego additional comments and refer you
straight away to the Smog
City simulation.
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Smog
City: Weather Conditions
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1.
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Review
the following sections in order listed: Home, Visitors Tour
Guide, Smog City Science, Help, and What You'll Learn.
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2.
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After
learning how to run the simulation, choose Run Smog City.
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3.
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Print
out the Activity Sheet and place it nearby to record the results
of your simulations. |
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4.
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The
first step is to examine the weather factors that influence
smog levels, and see each one's contribution to smog concentrations.
Vary each of the factors as listed on the Activity Sheet and
draw the resultant smog profile. Make sure you hit Reset
after each run to return to the default settings before altering
any parameters. |
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5.
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Following
this, complete the portions of your Activity Sheet that ask
you to evaluate the relative contribution of each factor, and
to design a "worst case" weather scenario for smog
concentrations. |
Graphing
In
the first section of the Activity Sheet, you are asked to graph
two smog profiles on one chart. Do this by distinguishing between
the lines with different colors, or by drawing two different types
of lines (dashed line vs. solid line). Make sure the reader is easily
able to distinguish which line is which by adding a label to the
chart identifying each line. An example is provided in Figure 1.
Figure
1. Graphing two smog profiles on one chart
Interpreting
Ozone Profiles
When
interpreting the severity of the ozone profiles the simulation returns,
you must look at two characteristics. First, you should evaluate
the maximum ozone concentration attained during the day, and the
corresponding air quality level. If you change a parameter and the
air quality reading goes from Moderate to Unhealthy,
this represents a significant reduction in air quality. Second,
you should also evaluate the length of time spent at different ozone
levels. This is best exemplified by Figure 2, which shows two runs
that both have peak ozone levels at the upper portion of the Unhealthy
level. Note though, that in the second curve, air quality is at
the upper portion of the Unhealthy range throughout the entire
afternoon (note plateau shape of curve), while in the first curve
the air quality is in the Unhealthy range for a much shorter
period of time (note peak shape of curve). This has obvious implications
for the individuals breathing the air, as adverse effects are dependent
not only on the severity of exposure (the maximum ozone level attained),
but also on the length of time individuals are exposed to these
conditions (the shape of the curve).
Figure
2. Comparing peak ozone concentrations and exposure durations
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Smog
City: Pollutant Outputs
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6.
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Note
that the factors we've examined so far aren't the only ones
modeled in Smog City. The simulation also allows you to manipulate
the sources of the compounds that form ozone, and this is
done with the controls at the bottom of the screen. You can
change the population size of your city, as well as pollutant
inputs from passenger vehicles, off-road vehicles, industry,
and consumer products. Follow the directions on the Activity
Sheet to evaluate these outputs.
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7.
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While the weather conditions that affect smog formation are
beyond human control, the release of the compounds that cause
ozone formation is not. Let's model some approaches to reducing
smog concentrations in Smog City by altering some factors
we realistically could control, and observing the resultant
changes in air quality with the simulation. Complete the exercise
described on your Activity Sheet.
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Internet
Addresses of Linked Sites
Smog
City: http://www.smogcity.com/welcome.htm
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