Lab Report: Dissolved Oxygen

Lab Report: Dissolved Oxygen Drew H.

I. Purpose The purpose of this test is to see the level of dissolved oxygen in the stream and use this information to propose a course of action for the future.

II. Background Dissolved oxygen is the measure of gaseous oxygen dissolved in an aqueous solution. For the stream, the dissolved oxygen level needs to be between 5mg/l and 20mg/l. Dissolved oxygen is used by organic material for decomposition, and is dictated by the temperature, salinity, and the atmospheric pressure. Temperature, though, will be the most prominent.

III. Materials:

 Thermometer  Pencil  Data Table  Gloves  Manganous Sulfate Solution  Alkaline Potassium Iodide Azide  Sulfuric Acid, 1:1  Sodium Thiosulfate  Starch Indicator  Direct Reading Titrator  Water Sampling Bottle, 60 ml

IV. Procedure 1. Rinse the water-sampling bottle with the sample water. 2. Tightly cap the bottle, and submerge it to the desired depth. 3. Remove the cap and allow the bottle to fill. 4. Tap the sides of the bottle to dislodge any air bubbles. 5. Replace the cap while the bottle is still submerged. 6. Retrieve the bottle and make sure that no air bubbles are trapped inside. 7. Remove cap from the bottle. 8. Immediately add 8 drops of Manganous sulfate solution and 8 drops of Alkaline Potassium Iodide Azide. 9. Cap the bottle and mix by inverting several times. A precipitate will form. 10. Allow the precipitate to settle below the shoulder of the bottle. 11. Add 8 drops of sulfuric acid, 1:1. 12. Cap and gently invert the bottle to mix the contents until the precipitate and the reagent have totally dissolved. The solution will be clear yellow to orange if the sample contains dissolved oxygen. 13. Fill the titration tube to the 20 mL line with the fixed sample. Cap the tube. 14. Depress the plunger of the titrator. 15. Insert the titrator into the plug in the top of the sodium thiosulfate titrating solution. 16. Invert the bottle and slowly withdraw the plunger until the large ring on the plunger is opposite the zero line on the scale. 17. Turn the bottle upright and remove the titrator. 18. Insert the tip of the titrator into the opening of the titration tube cap. 19. Slowly depress the plunger to dispense the titrating solution until the yellow-brown color changes to a very pale yellow. Gently swirl the tube during the titration to mi the contents. 20. Carefully remove the titrator and cap. Do not disturb the titrator plunger. 21. Add 8 drops of starch indicator solution. The sample should turn blue. 22. Cap the titration tube. Insert the tip of the titrator into the opening of the titration tube cap. 23. Continue titrating until the blue color disappears and the solution becomes colorless. 24. Read the test directly from the scale where the large ring on the titraor meets the titrator barrel. Record as ppm dissolved oxygen. Each minor division on the titrator scale equals 0.2 ppm. V. Data Testers Kit, Drew, Alston Date 5/5/2011 Weather Cold, sunny

Site pH D.O. (ppm) Conductivity (mpc) Water Temperature (Celsius) Air Temperature (Celsius) Time 2nd Storm Sewer 7.5 7 950 12.5 21.5 2:00 1st Storm Sewer 7.2 8 1010 13 13.5 8:52 New Circle Runoff 8.3 8 430 12.5 13.5 9:55 Headwater 6 7 630 18 13.5 9:26

Testers Kit, Drew, Alston Date 5/6/2011 Weather Cold, cloudy

Site pH D.O. (ppm) Conductivity (mpc) Water Temperature (Celsius) Air Temperature (Celsius) Time 2nd Storm Sewer 6.6 6 650 13.5 18 1:29 1st Storm Sewer 8.5 12 650 13.5 18 1:52 New Circle Runoff 6.9 7 1070 14 18 2:00 Headwater 7.7 10 1070 16 18 2:09

Testers Kit, Drew, Alston Date 5/9/2011 Weather Hot, sunny

Site pH D.O. (ppm) Conductivity (mpc) Water Temperature (Celsius) Air Temperature (Celsius) Time 2nd Storm Sewer 6.8 8 670 14.5 25 1:26 1st Storm Sewer 8.5 6.5 740 14.5 25 1:41 New Circle Runoff 6.9 5.5 1060 13 25 1:50 Headwater 8.3 9 1030 15 25 2:00

Testers Kit, Drew, Alston Date 5/10/2011 Weather Hot, sunny

Site pH D.O. (ppm) Conductivity (mpc) Water Temperature (Celsius) Air Temperature (Celsius) Time 2nd Storm Sewer 7 8 670 15 26 1:26 1st Storm Sewer 8.5 10 650 15 26 1:42 New Circle Runoff 7 12 1130 16.5 26 1:52 Headwater 8.5 7 1040 19 26 2:00

VII. Conclusion Error might have arisen from unintentional sediment in the stream, as there was much activity before the tests. For higher dissolved oxygen levels in the future, the stream will need to have more oxidization via riffles, falls, or other features that churn the water.