The Effect of Pollution and Atmospheric Carbon
Dioxide Lab
Objective:
To evaluate the effect of the presence of pollutants such as sewage, agricultural
runoff, etc., on atmospheric carbon dioxide.
Time:
This lab will take approximately 1 hour from set up to completion.
Materials:
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Computer
Vernier computer interface
Logger Pro
Vernier CO2 probe
40 ml of milk
Yeast
10-ml graduated cylinder
1-ml pipettes
Beaker
Background Information:
In aquatic systems, aerobic microorganisms such as bacteria use biodegradable
material for energy. In doing so, they consume oxygen and produce carbon dioxide.
The oceans and other bodies of water are the largest producers of carbon dioxide
going to our atmosphere. Refer to Figure 3.11 on page 68 of your textbook to see
other fluxes of carbon in our environment.
Procedure:
1. Using the graduated cylinder, add 5 ml of tap water to the 250-ml gas-sampling
bottle.
2. Add 10 ml of milk to the 250-ml gas-sampling bottle and set the bottle aside.
3. Plug the Vernier CO2 probe into Channel 1 of the Vernier computer interface.
4. Prepare the computer for data collection by opening the Logger Pro software found
on the desktop.
5. Click on File; then click on Open. Double-click on the folder Biology with
Computers. Finally, double-click on lab 12A Yeast Respiration.
6. Noting the time, add 1 ml of yeast mixture (1 package of yeast to 400 mls water) to
the 250-ml gas-sampling bottle and swirl to mix.
7. Carefully take the Vernier CO2 probe and put it into the neck of the 250-ml gassampling bottle until the stopper has fit securely.
8. Allow the Vernier CO2 probe about 90 seconds to warm up; then click on the
Collect button on the top tool bar.
9. As the yeast utilize the material for energy, they will begin using the oxygen and
producing CO2. The Vernier CO2 probe will measure the amount of CO2 that is
dissolving out of the liquid and into the air in the 250-ml gas-sampling bottle.
10. Continue to sample for 4 minutes.
11. Highlight the line on the graph that appears by dragging your mouse over it and
clicking on the R= button on the top tool bar.
12. Click on the Stop button and print your graph.
13. Repeat steps 1 through 12, but change the amount of milk from 10 mls to 30 mls.
14. Clean up your materials and return them to the proper laboratory station.
Analysis:
1. What gas is needed by the microorganisms?
2. What gas is given off by the microorganisms? Write out the equation for respiration
and compare to photosynthesis.
3. Which part of your experiment represents the decomposers?
4. Which part of your experiment represents the sewage dumped into the water or
agricultural runoff?
5. How can we remediate the problem of sewage and/or agricultural runoff into our
rivers, lakes, and streams?
6. Why did we use up the milk in the second part of the experiment? What did this
represent?
7. How would the amount of CO2 in the atmosphere be affected by large amounts of
waste being dumped into the ocean?
8. Describe and give an example of a carbon flux and a carbon sink.
9. Write a conclusion describing what you learned by performing this lab.