DO, BOD, pH, and Turbidity of four Aquatic Environments in Natchitoches, Louisiana
From August 27th to September 3rd of this year, data was collected from Chaplin’s Lake, Cane River, Wellwoods Lake, and Wellwoods Bayou in Natchitoches, Louisiana. Data collected by previous Ecology classes in 2010 and 2011 was included in the experiment in order to provide data that could help to determine patterns over time. The objective of this experiment was to measure and compare dissolved oxygen content, pH, biological oxygen demand, and turbidity of these four sites in order to determine whether any correlations exist between these factors. Because of the variance between each of the aquatic ecosystems involved in this experiment, each supports different types of plants and animals which are affected by environmental changes such as temperature and, by extension, dissolved oxygen content. II. Procedure
At each site a water sample was collected by throwing a bucket attached to a rope into the body of water after rinsing the bucket three times with water from the body being tested. Once the sample was collected, pH, temperature, dissolved oxygen, and turbidity were measured. To determine turbidity, a transparency tube with a checkerboard pattern was used. The trasparency tube was emptied and then filled with water so that the pattern on the bottom could bnot be seen. Water was then slowly released and a measurement was taken when the checkerboard was visible again. There were some measurements that were not taken due to the lack of a thermometer on September 13th at Wellwoods Bayou and Wellwoods Lake. A sample bottle from each site was collected and analyzed by Meredith McManus in the lab to determine biological oxygen demand (BOD). Salinity was also measured at each site, but there was no salt present because all sites consisted of fresh water. To determine the dissolved oxygen content, the LaMotte Kit (or Winkler Method) was used. These steps were followed: 1. Fill glass container provided in the kit with desired water sample 2. Put on gloves
3. Add 8 drops of the Manganous Sulfate Solution (Green)
4. Add 8 drops of Alkaline Potassium Iodide Azide (Blue)
5. Close the container and slowly flip it upside down and then upright again three times - this will cause a precipitate to form inside the container 6. Wait for the precipitate to settle to the bottom third of the container 7. Reopen the container
8. Add 8 drops of sulfuric acid (Red) to the sample
9. Close the container and slowly mix the contents by turning the container upside down and upright – this willcause the precipitate to dissolve and, should oxygen be present, the solution will turn a light yellow. Next, the sample from step nine was analyzed to determine the dissolved oxygen content in parts per million. These steps were followed: 1. Open the sample container and pour 20 ml of the solution into the titration tube provided in the kit. 2. Take the titrator (syringe) and depress the plunger.
3. Insert the tip of the titrator into the bottle of Sodium Thiosulfate (Yellow) 4. Turn the bottle of Sodium Thiosulfate upside down
5. Slowly pull the plunger downwards until the titrator is full up to the 10 ml line 6. Turn the bottle upright again and carefully remove the titrator 7. Insert the tip of the titrator into the titration tube containing the water sample 8. Depress the plunger slowly to add one drop of Sodium Thiosulfate to the solution 9. Swirl the sample container to mix the solution evenly
10. Repeat steps 8 and 9 until all 10 ml of Sodium Thiosulfate have been emptied into the titration tube. 11. Remove the titrator from the hole in the plastic lid of the titration tube 12. Add 8 drops of starch indicator – this should cause the solution to turn blue 13. Refill the titrator with Sodium Thiosulfate (using steps 2,3, 4,and 5) 14. Replace the titrator in the hole at the top of the titration tube 15. Add the Sodium Thiosulfate...
Cited: Previous Ecology classes ' data
Louisiana Universities Marine Consortium. LUMCON.
Cary Institute of Ecosystem Studies, Changing Hudson Project
Ecology on Campus: lab manual. Robert W. Kingsolver
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