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  pH Worksheet
 

Names: _________________________________________

Date: _________________________

Part 1 - pH in a Microcosm

Data Collection
After setting up the microcoms, enter your predictions in the tables below. Then record the initial values for each parameter.

After the microcosms have sat for 20-30 minutes, you can record your results. In determining the final values, begin by collecting and testing water samples for oxygen. Then record the pH and CO2 values.

Aged Water Only

Microcosm A

Prediction

Initial Value

Final Value

DO (mg/l)

     

pH

     

CO2 (mg/l)

     

Buffered Water

Microcosm B

Prediction

Initial Value

Final Value

DO (mg/l)

     

pH

     

CO2 (mg/l)

     

Minnows Only

Microcosm C

Prediction

Initial Value

Final Value

DO (mg/l)

     

pH

     

CO2 (mg/l)

     

Minnows in Buffered Water

Microcosm D

Prediction

Initial Value

Final Value

DO (mg/l)

     

pH

     

CO2 (mg/l)

     

Pondweed Only

Microcosm E

Prediction

Initial Value

Final Value

DO (mg/l)

     

pH

     

CO2 (mg/l)

     

Pondweed in Buffered Water

Microcosm F

Prediction

Initial Value

Final Value

DO (mg/l)

     

pH

     

CO2 (mg/l)

     

Data Management and Analysis
Write the equations for photosynthesis and respiration. Were the changes that you observed in oxygen and carbon dioxide concentrations consistent with the equations? Explain.

Write the carbon-dioxide bicarbonate equilibrium equation. Which microcosms showed changes in pH? Were the changes consistent with this equation? Explain.

Part 2 - Effects of pH in Lakes

Data Collection
Fill in the following tables with the WOW data collected by the RUSS. Construct graphs that show the lake's pH profiles for each date. Do not collected the DO data until you have made a hypothesis about the lake's oxygen profile based on your pH information.

Summer pH and DO for Ice Lake

Date: _______________

Depth (m)

pH

Predicted DO

Actual DO

2

     

4

     

6

     

8

     

10

     

12

     

Winter pH and DO for Ice Lake

Depth (m)

pH

Predicted DO

Actual DO

2

     

4

     

6

     

8

     

10

     

12

     

Interpretation of Results
Based on the results from the microcosms, do you think Ice Lake was stratified or mixed in the winter? In the summer?

Do you think Ice Lake was depleted of oxygen at any depth in the winter? In the summer?

How would you explain your results?




 


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date last updated: Saturday March 06 2004