Wastewater and Its Effect on Atmospheric Carbon Dioxide Lab
DESIGN/PLANNING
Objective/Purpose: Describe the purpose of this lab in your own words.
Background Info: In aquatic ecosystems, 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.
Hypothesis:
Controls/Variables:
Materials:
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Computer or USB thumbdrive
Vernier LabQuest2
Logger Lite
CO2 probe
40 ml of milk
Yeast
10-ml graduated cylinder
50-ml graduated cylinder
1-ml pipettes
Beaker
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 aside.
3. Turn on your LabQuest2. Go to “File”, “Delete”, and delete any existing files.
4. Plug the CO2 probe into Channel 1 and let it warm up for about 90 seconds. Be sure switch on sensor is set to “Low”.
5. Use the stylus to calibrate the sensor by pressing the “CAL” button on the side of the sensor.
6. Using the stylus, select LabQuestApp from the Home menu. You should see a live CO2 reading in ppm. If not, see your
instructor. LabQuest2 should now read under 400ppm. You are now ready to begin recording data.
If using your USB:
7. Plug your USB drive into the LabQuest2.
8. 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.
9. Firmly secure the 250-ml gas-sampling bottle to the ring stand clamp.
10. Carefully take the CO2 probe and put it into the neck of the 250-ml gas-sampling bottle until the stopper has fit securely.
DO NOT ALLOW THE PROBE TO TOUCH LIQUID!!!!
11. Click on the green PLAY (start) button at the bottom left corner of the screen. This will begin your data collection.
12. As the yeast utilize the material for energy, they will begin using the oxygen and producing CO 2. The 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.
13. Continue to sample for 4 minutes, and then click the red STOP button. (Time is shown at the bottom right corner of the
screen). If your sample time ran over, simply touch the stylus to the end line and drag it to the desired time on the xaxis.
14. Repeat steps 1 through 11, but change the amount of milk from 10 mls to 30 mls.
15. At the top right of the screen, you will see “RUNS” listed. Click on “Run 2”, and then click on the green play button and
record data for 4 min.
16. Select “All Runs” from the menu at the top right, so that both graphs are displayed on the screen. This is the data/graph
you want to embed in your lab report.
17. Select “File”, “Export”, choose the icon of your USB drive to save as a text file (.csv). Be sure to name the file by clicking
on the empty “untitled” field. DO NOT SAVE YOUR DATA TO THE LABQUEST2.
18. RETURN THE STYLUS TO ITS HOLDER ON THE LABQUEST2.
19. Clean up your materials and return them to the proper laboratory station.
DATA COLLECTION &PROCESSING
 Recording and presentation of data with the appropriate units
 Transforming and manipulation of raw data: when applicable give formulas and show all calculations.
 Presentation of processed data: data/results are presented appropriately and effectively, i.e. graphs of data,
statistic data tables etc.
Analysis Questions:
1.
What gas do the microorganisms require?
2.
What gas do the microorganisms release?
3.
Write out the equation for respiration and compare to photosynthesis.
4.
Which part of your experiment represents the decomposers?
5.
Which part of your experiment represents the sewage dumped into the water or agricultural runoff?
6.
How can we remediate the problem of sewage and/or agricultural runoff into our rivers, lakes, and streams?
7.
Why did we use up the milk in the second part of the experiment? What did this represent?
8.
How would the amount of CO2 in the atmosphere be affected by large amounts of waste being dumped into the
ocean?
9.
Describe and give an example of a carbon flux and a carbon sink.
CONCLUSION & EVALUATION
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Interpretation of results: drawing valid conclusions (i.e. support or reject your hypothesis) based on your data, with an
explanation. Where appropriate, results are compared with given/known values.
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Evaluate procedure: The procedure (i.e. materials and methods) including limitations, weaknesses or errors in
manipulation are evaluated (discussion of the limitations of data analysis may be included.)
Modifying the Procedure: Suggest ways to improve the lab or suggest an area for further study. This should be based on the
identification of weaknesses or limitations.