Tracking Ozone Pollution
On a hot summer day, you might hear a TV or radio announcement like this: High ozone
levels are expected, so take a bus, walk, or ride your bike today! Yet, you may have learned that
the ozone layer helps shield the Earth from damaging ultraviolet rays. In fact, ozone (O3) is both
an environmental protector and a pollutant. High in the atmosphere, ozone benefits the Earth.
But close to the Earth’s surface, ozone threatens air quality. It is one of the main components of smog, and at high
levels it can cause lung damage & other respiratory problems.
Ozone forms when hydrocarbons (CxHy) & nitrogen compounds (NOx) react with sunlight. Hydrocarbons come
from engine exhaust, the storage & transfer of fuels, and various industrial chemicals. Dangerous nitrogen compounds
form during high temperature combustion. Although ozone production takes place all year long, the intense sunlight of
summer significantly increases concentration levels. For this reason, ozone alerts are most common in summer, which is
when air quality experts strongly urge you to avoid unnecessary activities that lead to the production of ozone-forming
compounds.
What is the Standard?
The Environmental Protection Agency (EPA) has established a national standard for acceptable ozone levels. The
standard is based on the concentration of ozone that causes harmful effects on human health. In order to meet the EPA
standard, many cities have taken measures to reduce ozone levels & improve air quality. In this activity, you are the airquality analyst for the city of Ozonopolis.
1. To apply the standard, ozone concentrations are monitored daily at different sites.
2. If the average for ozone concentration is greater than 0.12 ppm, then the day is identified as an excedance day.
A site that has more than one excedence day per year is in violation of the EPAs standard.
3. The EPA evaluates the highest level of ozone measured each year to determine if a violation has occurred.
4. You must analyze the higher yearly levels of ozone and identify trends in pollutants concentrations over a 10year span. Then you must decide how effective the city has been at reducing ozone pollution.
Graphing Maximum Measurements
The data table below shows the measurements recorded at two different sites in Ozonopolis. These measurements are
the highest concentration of ozone recorded each year for 10 years. Graph the data on the right.
Yearly Highest Levels of O3
Year
Site A
Site B
1998
0.131 ppm
0.110 ppm
1999
0.119 ppm
0.089 ppm
2000
0.095 ppm
0.075 ppm
2001
0.106 ppm
0.086 ppm
2002
0.098 ppm
0.068 ppm
2003
0.090 ppm
0.062 ppm
2004
0.089 ppm
0.073 ppm
2005
0.091 ppm
0.073 ppm
2006
0.101 ppm
0.070 ppm
2007
0.095 ppm
0.081 ppm
1.
Identify all times & places at which the EPA’s standard was exceeded.
2. Which years show a citywide decrease in the highest-recorded ozone levels?
3. For each site, describe the trend in highest recorded ozone concentrations for the following time periods:
a. 1998 – 2002
b. 2003 – 2007
4. Why might two sites in the same city have different pollutant levels? Provide examples of two places in
Charlotte that you would expect to have different pollutant levels.
5. Based on the information provided, describe the environment in which each site is probably located. Explain
your reasoning.
Analyzing a Box-Plot Graph
6. As an air quality analyst, you may need more information about ozone
levels than just the year’s highest concentrations. A box-plot graph allows
you to compare & contrast the readings taken all year long. During 1990,
monitors throughout Ozonopolis took 8800 readings. To the right is a boxplot graph for 2000. Notice that the value at the top of the chart is 0.085
ppm. The box-plot shows that 95% of the measurements taken that year,
or 8360 readings, were below 0.085 ppm. The value 0.070 ppm
corresponds to the box-plot mark of 90%. How many readings were below
0.070 ppm?
7.
What percent of the measurements taken were below 0.040 ppm?
8. What percent of the measurements taken were below 0.01 ppm?
Investigating Ice Bubbles
Scientists look for patterns in collected data to
help them make predictions about particular
phenomena. Part of data analysis is asking questions
about the data while looking for patterns or trends.
One question that scientists ask is whether the
increase of greenhouse-type gases in the
atmosphere is causing global warming. Greenhouse
gases, such as CO2, trap the sun’s heat and warm the
atmosphere. The planet Venus, which has a high
level of CO2 in its atmosphere, has a surface
temperature of about 453o C (700o F). Many
scientists are trying to draw a correlation between
the rise in greenhouse gases in the atmosphere and
the steady increase in Earth’s surface temperature.
Your task is to analyze the following graphs of data
and draw your own conclusions about the changes
in the amount of CO2 in Earth’s atmosphere.
Look at Recent Data
1.
Atmospheric CO2 is naturally produced as part of the carbon cycle. The graph in Figure 1 below was generated
from data collected at Mauna Loa observatory on the island of Hawaii. This site is isolated from large
landmasses and large cities and is at an elevation above 13,000 feet. Explain why scientists would measure
global atmospheric CO2 in an area such as this?
2.
Look at the graph of atmospheric CO2 above. Describe two patterns or trends in the level of CO2 that are
apparent from the data.
3. Look carefully and you’ll see that the line graph is curved. What does the shape of the graph tell you about the
rate of increase in the level of CO2?
4. What might explain the peaks and valleys in the graph?
5. Assuming the current rate of increase continues for the level of CO2, predict the levels of atmospheric CO2 in the
years 2025 & 2050.
Look at the Ice Record
The collected data from Mauna Loa is the longest, most detailed record of its kind. However, the data has only
been charted for 40 years. Are increasing levels of CO2 part of a general trend or are they the direct result of human
activity? To find out scientists analyze air trapped in glacial ice.
Scientists extract a long core of ice from a glacier to learn about conditions on Earth before recorded history.
They date the ice core, crush the ice to release trapped gas, expand the gas, and measure the concentration. By
measuring the percentage of CO2 in the trapped air, scientists can reasonably estimate the changing level of
atmospheric CO2 over longer periods of time.
6. Take a look at Figure 2 above. Describe the level of CO2 from 1750 to
1800.
7. What happened to the level of CO2 after the year 1800?
8. What major development characterizes human civilization in the late
1700s & early 1800s?
Figure 2
9. Are present levels of CO2 normal or unusual? Explain your
answer.
10. In geological time, 250 years is like the “blink of an eye.” It is
difficult to accurately identify a global trend from such a small
interval of time. The graph if Figure 3 represents data from an
older ice core that provides a recore of Earth’s atmospheric
content for the last 1000 years. Describe the change in the
level of atmospheric CO2 before the year 1800.
Figure 3
11. What does the Law Dome graph seem to indicate about the
relationship between the level of CO2 and human activity?
Explain your answer.
12. Even a thousand years is a relatively short interval in
geologic time. Compare the level of CO2 as indicated in
figures 2 & 3, to the levels of the last 160,000 years, as
indicated in Figure 4. Is today’s level of atmospheric CO2
unusually high or normal? Explain.
Figure 4
13. What do you think is a normal level of CO2 in the Earth’s atmosphere? Explain your answer.
14. Based on the data you have analyzed in this activity, do you think human activity is responsible for the
greenhouse effect? Explain your answer.