Dissolved Oxygen
77
EXERCISES
OPTION 1. FIELD TRIPS
1. From the central depression of a lake, collect water samples for oxygen analysis and fix the
dissolved oxygen chemically by the techniques outlined earlier (pp. 73-74). Collect replicates
at each depth. Place samples in an ice chest for transport to the shore or laboratory.
2. Determine the temperature of the water at each depth throughout the vertical profile with an
underwater thermometer.
3. Working in pairs, determine the dissolved oxygen content of each sample. Analyze duplicate
samples from the same sample bottle and determine the standard error and variance (cf.,
Appendix 2). When prestandardized sodium thiosulfate solution is not available, standardize
the Na2S2 0 3 solution according to the directions given below (p. 79) and calculate the
molarity of your solution.
4. Calculate the percentage saturation of dissolved oxygen from the temperature data and
barometric pressure or altitude. Use the nomogram provided in Figure 6.1. From the
collective class data, plot the dissolved oxygen concentrations, percentage saturation, and
temperature data versus depth.
5. Collect oxygen in the littoral zone among dense strands of aquatic macrophytes and from inlet
sources. Compare these values with those from comparable depths in open water.
OPTION 2. LABORATORY EXERCISE
1. From the water sources provided by your instructor, fill the sample bottles carefully with the
rubber tubing, taking care to avoid the inclusion of air bubbles. Measure the temperature of
the water source. Fix the dissolved oxygen of the water samples chemically by the techniques
outlined earlier (p. 73).
2. Working in pairs, determine the dissolved oxygen content of each sample. Analyze duplicate
samples from the same sample bottle and determine the standard error and variance (cf.,
Appendix B). When prestandardized sodium thiosulfate is not available, standardize the
Na2S2 0 3 solution according to the directions given below and calculate the molarity of your
solution.
3. Calculate the percentage saturation of dissolved oxygen from the temperature data and the
barometric pressure or altitude. Use the nomogram provided in Figure 6.1.
4. From the data provided in Table 6.2, plot the dissolved oxygen concentration, percentage
saturation, and temperature data versus depth.
Questions
1. What do the data for concentrations of dissolved oxygen tell you about solubility of this gas in
relation to temperature?
2. How does the percentage saturation of oxygen clarify the relationship of solubility and
temperature of the water?
3. How would you expect the oxygen concentrations of epilmnetic water to fluctuate throughout
the course of a day? Why? In an unproductive versus a productive lake?
4. How would you expect the oxygen concentrations of epilimnetic water to vary in horizontal
distribution from the shore line to open water?
5. How would you expect the dissolved oxygen content to vary above and below the sedimentwater interface? [cf., Carlton and Wetzel (1988).]
77
EXERCISES
OPTION 1. FIELD TRIPS
1. From the central depression of a lake, collect water samples for oxygen analysis and fix the
dissolved oxygen chemically by the techniques outlined earlier (pp. 73-74). Collect replicates
at each depth. Place samples in an ice chest for transport to the shore or laboratory.
2. Determine the temperature of the water at each depth throughout the vertical profile with an
underwater thermometer.
3. Working in pairs, determine the dissolved oxygen content of each sample. Analyze duplicate
samples from the same sample bottle and determine the standard error and variance (cf.,
Appendix 2). When prestandardized sodium thiosulfate solution is not available, standardize
the Na2S2 0 3 solution according to the directions given below (p. 79) and calculate the
molarity of your solution.
4. Calculate the percentage saturation of dissolved oxygen from the temperature data and
barometric pressure or altitude. Use the nomogram provided in Figure 6.1. From the
collective class data, plot the dissolved oxygen concentrations, percentage saturation, and
temperature data versus depth.
5. Collect oxygen in the littoral zone among dense strands of aquatic macrophytes and from inlet
sources. Compare these values with those from comparable depths in open water.
OPTION 2. LABORATORY EXERCISE
1. From the water sources provided by your instructor, fill the sample bottles carefully with the
rubber tubing, taking care to avoid the inclusion of air bubbles. Measure the temperature of
the water source. Fix the dissolved oxygen of the water samples chemically by the techniques
outlined earlier (p. 73).
2. Working in pairs, determine the dissolved oxygen content of each sample. Analyze duplicate
samples from the same sample bottle and determine the standard error and variance (cf.,
Appendix B). When prestandardized sodium thiosulfate is not available, standardize the
Na2S2 0 3 solution according to the directions given below and calculate the molarity of your
solution.
3. Calculate the percentage saturation of dissolved oxygen from the temperature data and the
barometric pressure or altitude. Use the nomogram provided in Figure 6.1.
4. From the data provided in Table 6.2, plot the dissolved oxygen concentration, percentage
saturation, and temperature data versus depth.
Questions
1. What do the data for concentrations of dissolved oxygen tell you about solubility of this gas in
relation to temperature?
2. How does the percentage saturation of oxygen clarify the relationship of solubility and
temperature of the water?
3. How would you expect the oxygen concentrations of epilmnetic water to fluctuate throughout
the course of a day? Why? In an unproductive versus a productive lake?
4. How would you expect the oxygen concentrations of epilimnetic water to vary in horizontal
distribution from the shore line to open water?
5. How would you expect the dissolved oxygen content to vary above and below the sedimentwater interface? [cf., Carlton and Wetzel (1988).]