Outdoor Air Pollution Lab
(modified from Flinn Scientific)
The EPA labels the following air pollutants as criteria pollutants – particulates,
carbon monoxide, nitrogen oxides (NOx), Sulfur dioxide (SOx), Ozone, and Lead.
Cities are required by law to monitor 5 of these six (omitting lead). We are going to
test for particulates, sulfur dioxide, and Ozone in our local (Westwood) outdoor air
environment.
Part A: Particulates
1. Get a slide from the supply area, and record the slide location on data table 1. These slides were
placed outside, with the sticky label side up, for 7 days.
2. Make some general qualitative observations about the type of particles you see on the slide. Measure
and draw two 1 cm2 squares (1 cm by 1 cm) on your label. Using a magnifying glass, count or carefully
estimate how many particles are in each of the squares. Make sure to look for particles that may be
white or tan. Record these values for each square, and average the two. Total particle counts between
100 to 500 per square centimeter indicate slight particulate pollution, counts over 500 per square
centimeter indicate high particulate pollution.
Data Table 1: Westwood Outdoor Particulate Pollution Data
Item
Data
Location of Slide
General observations
Square #1 Count (1 cm2)
Square #2 Count (1 cm2)
Average value of count 1 and 2
Part A: Analysis Questions
1. Did your test area have low or high particulate pollution? Give examples of possible sources of
particulate pollution in your test area.
Compare your results with other lab groups for questions 2-3.
2. Which location had the highest number of particulates? The lowest?
3. Which location had the most variable types of particulates (size, color differences)?
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Part B: Acidic Air Compounds – SOx and NOx
Experiment 1 – Smoke from a Match
1. Fill the sampling container to the 10 mL line with distilled water. Add 10 drops of universal indicator
solution to the water. Use the pH probe to take the pH of the solution. You may need to tilt the liquid so
the end of the pH probe is completely in the solution.
2. Swirl the solution in the sampling container and record the original color of the solution in the data
table.
3. Light a match and blow it out. Capture as much smoke as you can in the sampling container by
holding the smoking match inside the continar with the lid over it. Try to capture all of the smoke from
the match in the sampling container. Then drop the match INTO the solution. The smoke produced from
a match has some phosphorus and sulfur compounds, including SOx compounds. This smoke from the
burning simulates industrial/coal fumes.
4. Swirl solution in the sampling container so it can interact with the fumes. Record the color change
observation and the pH of the resulting solution. Take a pH reading with pH paper.
5. CLEAN UP: Dispose of the match in trash, pour any solution down the drain, and rinse the sampling
container with distilled water for the next experiment.
Experiment 2: Outside Air
1. Fill the sampling container to the 10 mL line with distilled water. Add 10 drops of universal indicator
solution to the water. Take the pH of the solution with the pH meter. You may need to tilt the liquid so
the end of the pH probe is completely in the solution.
2. Swirl the solution in the sampling container and record the original color of the solution in the data
table.
3. Attach a 2 inch piece of tubing to the end of a syringe (the same way we connected the water syringe
to the tubing of the flat-plate collector lab). Take your syringe AND sampling container outside, and fill
the syringe completely with outside air.
4. Force the air out of the syringe through the tubing and into the universal indicator /water solution by
pushing the plunger. Repeat filling the syringe with air and putting it into the solution TEN more times.
If the solution does not change color, the air in your area has a fairly low amount of acidic gases. If the
solution changes to a darker yellow or orange color, you local air supply contains a high amounts of
acidic gases (SOx or NOx). Take the pH of the solution with the pH meter.
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5. CLEAN UP: Pour any solution down the drain, and rinse the sampling container with distilled water for
the next group.
Data Table 2: Acidic Air Compounds – SOx and NOx
Information
Data
Experiment 1 – original color and pH of solution
Experiment 1 – pH of solution after match burning
Experiment 2 – original color and pH of solution
Experiment 2 – pH of solution after outside air
Analysis Questions Part B:
1. What was the pH change of the solution after burning a match? Was your simulated rain acidic or
basic?
2. What are some possible sources of acidic gases in the air?
3. Explain possible environmental consequences of high levels of acidic gas in the air.
Part C: Effects of Acid Rain/ How Acidic is Austin Rain
Experiment 1: Effects of Acid Rain on Building Materials
1. Place a small marble chip in the sampling container
2. Using a pipette, place 20 drops of “unpolluted” rain water on the marble chip. Record
observations. Pull the chip out of the container with the forceps, rinse with distilled water,
and dry. Dump the water out of the container and rinse with distilled water.
3. Using a pipette, place 20 drops of “simulated acid rain solution” on the same marble chip. Record
your observations. Pull the chip out of the container with the forceps, rinse with distilled water, and dry.
Dump the water out of the container and rinse with distilled water.
4. Clean up: Make sure to return the stone chip to the supply area.
Experiment 2: Rainwater
1. Go over to the “Austin Rain” station, which has a sample of Austin Rain water.
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2. Dip an acid rain test strip into the water.
3. Compare the color of the test strip to the color chart. Record the color of the test strip and the acidity
of the rainwater in your area in the data table.
Data Table 3: Effects of Acid Rain/ How Acidic is Austin Rain
Information
Data Observations
Experiment 1 – Marble Chip with “Unpolluted”
rain water
Experiment 1 –Marble chip with “Simulated Acid
Rain Solution”
Experiment 2 – Color of Austin rain test strip after
sampling
Experiment 2 – pH of rain water
Analysis Questions
1. What effect did the simulated acid rain have on the limestone chip?
2. What does this experiment show about the decay of buildings and statues in metropolitan areas?
3. What effect does acid rain have on plant life and aquatic organisms?
Experiment D: Sooo Good, Tooo bad. Levels of
tropospheric ozone in Austin.
You will be doing the Schoenbein test for ground level ozone. The ozone in the
atmosphere will oxidize the potassium iodide that you have put on a test strip, to
produce iodine. The iodine then reacts with the starch on the test paper, staining the
paper purple. The darker the purple color, the more ozone in the air.
Block 1: Making the Ozone Test Strip
1. Add 5 g of corn starch to 100 mL of distilled water in a 250 mL beaker.
2. Heat on a hot plate and stir the mixture with a stirring rod until it becomes evenly mixed and starts to
gel. The mixture is gelled when it thickens and becomes somewhat translucent.
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3. Carefully remove the beaker from the hot plate with your hot hands and add 1 g of potassium iodide.
Stir well, and let cool. Hot beakers can be placed directly with the heat-resistant black lab tables.
4. On your filter paper, use a sharpie to make an identifying mark on your filter paper. Then place your
filter paper on your cafeteria tray, and use the small sponge brush to brush the starch-potassium iodide
solution evenly on one side of the filter paper. Turn the filter paper over, and spread more of the
solution on the other side of the paper. Apply the paste as evenly as possible.
5. Use an unfolded paper clip to make a hook to hang the wet test strip. Select an outdoor location to
hang the test strip. The strip should be out of direct sunlight.
Block 2 – Analyzing the Test Strip
1. Use the humidity value on the board and record today’s humidity.
2. Get your test paper from your outdoor sampling location.
3. To observe the test results, DIP THE PAPER IN DISTILLED WATER. Observe the color and determine the
Schoenbein Number using the Schoenbein color scale.
9. Using your humidity data, and the Schoenbein number, determine the ozone concentration, in parts
per billion.
Data Table 4: Tropospheric Ozone Concentrations Around Westwood
Description of Test
Site
Today’s
Humidity
Color of test
strip (AFTER
being dipped in
distilled water)
Schoenbein
Color Scale
Number
Ozone ppb
(From YOUR
experiment)
Analysis Questions:
1. Do you think this is a good method for measuring tropospheric ozone? Why or why not?
2. Find the actual ozone ppb from the teacher for the day you put your test strip out. What was the
percent error for your measurement?
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