Waste and Its Effect on Atmospheric Carbon Dioxide
Objective:
In this laboratory exercise, you will conduct an experiment to evaluate the effect the
presence of pollutants such as sewage, agricultural runoff, etc. have on atmospheric
carbon dioxide.
Introduction:
In aquatic systems, aerobic microorganisms like bacteria use biodegradable material
for energy and 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 the diagram below to see other fluxes of carbon in our
environment.
Materials:
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Computer
Vernier computer interface
Logger Pro
Vernier CO2 probe
Milk
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Yeast
10-ml graduated cylinder
1 ml pipettes
Beaker
Procedure:
1. Using a 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.
3. Set the gas sampling bottle aside.
4. Plug the Vernier CO2 probe into Channel 1 of the Vernier computer interface.
5. Prepare the computer for data collection by opening the Logger Pro software found on
the desktop.
6. Click on file, then click on open, then double click on the folder biology with computers
and double click on lab 12A Yeast Respiration.
7. Noting the time, add 1 ml of yeast mixture (1package yeast to 400 mls water) to the 250ml gas sampling bottle and swirl to mix.
8. Carefully take the Vernier CO2 probe and put the probe into the neck of the 250-ml gas
sampling bottle until the stopper has fit securely.
9. Allow the Vernier CO2 probe about 90 seconds to warm up and then click on the collect
button on the top tool bar.
10. 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.
11. Sample for 4 minutes.
12. Highlight the line by draggin your mouse over it and click on the R= button on the top
tool bar.
13. Click on the stop button and print your graph.
14. Repeat procedures 1- 12 but change the amount of milk from 10mls to 30 mls.
15. Clean up your materials and return them to the proper laboratory station.
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Analysis:
1. What is the gas needed by the microorganisms?
2. What is the gas given off by the microorganisms?
3. Why is the oxygen in this lab used up?
4. Which part of your experiment represents the decomposers?
5. Which part of your experiment represents the sewage dumped into the water?
6. What would be the effects of dumping a great deal of raw sewage into a river or ocean
as regard to the dissolved oxygen in the same river? Why did we up the amount of 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 as to what you learned by performing this lab.