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Does the Level of Turbidity in Water Increase or Decrease Dissolved Oxygen Levels??

Researched by Cristal G.



The purpose of this experiment was to determine if the level of turbidity in water affected the amount of dissolved oxygen.  I became interested in this idea because I am interested in water quality and environmental issues.  I am interested in water quality because dissolved oxygen keeps fish and other animals alive.  The information gained from this experiment could be useful to the fish and wildlife foundation and dam operators.

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My hypothesis is that the more turbidity levels in water increase, the more dissolved oxygen levels decrease.  I base my hypothesis on information that I have found in numerous sources, including books, encyclopedias, and Internet Sites.

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 Experimental Design

The constants in this study were:
 ~ Same amount of water tested
 ~ Same testing procedures
 ~ Test the same time each day
 ~ Same chemicals used

The manipulated variable was the level of turbidity in water.  There were three different locations tested.  Each different location had three different levels of turbidity. 

The responding variable was the amount of dissolved oxygen in different levels of turbidity.

To measure the responding variable a dissolved oxygen kit and a turbidometer were used.

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2 bottle with stopper
1 dissolved oxygen pillow #1
1 dissolved oxygen pillow #2
1 dissolved oxygen pillow #3
1 bottle of sodium thiosulfate
1 pair of protective gloves
1 nail clippers
1 pair of boots/hipwaiters
1 testing tube 
10 quart Jars

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1. Find an area of water that looks like it would be good to test turbidity on.
2. Put one of the quart jars beneath the river surface and allow water to go in. 
3. Put the lid on the jar.
4. Next, grab the bottle with stopper and put it in the exact spot that you got the water in the jar from.
5. Remove the stopper from the bottle and allow water to flow over for two to three minutes to eliminate air bubbles.
6. Put on goggles and safety gloves.
7. Add the contents of pillow #1 and pillow #2 into the dissolved oxygen bottle and swirl.
8. Put the stopper into the bottle.  Make sure that no air gets trapped inside.  Be sure to shake well to fully mix.
9. If a brownish-orange precipitate forms oxygen is present.  IF no brownish-orange precipitate shows up then redo the sample.
10. Add dissolved oxygen pillow #3 to the sample and swirl.  The precipitate will dissolve and the water will turn yellow.
11. Pour sample into top of measuring tube, and then pour the contents of the measuring tube into the square-mixing bottle.
12. Add one drop of thiosulfate to the square mixing bottle and swirl.  Be sure to hold the eyedropper straight over the bottle.
13. While swirling, continue to add more drops of thiosulfate into the bottle.  Count how many drops before the yellow color turns clear.  Each drop of thiosulfate equals 0.5 mg/L of dissolved oxygen.
14. Find somewhere that has a turbidometer and make an appointment to use it.
15. Get your sample (the water in the quart jars) and take it to the place where the turbidometer is located.
16. Get a water vial and pour the sample into it.
17. Dry the outside of the vial.
18. Put the vial into the turbidimeter and light will refract through to the sensor to give you a turbidity reading.

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The original purpose of this experiment was to determine if the level of turbidity in water increased or decreased dissolved oxygen levels.  The results were that the test groups with the greater level of turbidity also had the greatest level of dissolved oxygen.  The groups with the lower level of turbidity had a low level of dissolved oxygen.

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My hypothesis was that the more turbidity levels increase, the more dissolved oxygen levels decrease.  The results of this experiment indicate that my hypothesis should be rejected because in fact, higher turbidity levels actually increase the level of dissolved oxygen in water.  Because of this experiment, I wonder if turbidity affects photosynthesis?  If I were to conduct this experiment again I would have taken more samples.  This would have been more informative.

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Research Report

 Does Dissolved Oxygen increase or decrease with high turbidity levels??  Do the words Turbidity and Dissolved oxygen seem confusing?   Hopefully, in reading this report, these terms will become understandable and better enable understanding towards this project.
 This project is about the relationship between turbidity and dissolved oxygen.  The reason that this project is important is because fish and wildlife need oxygen to live.  Another reason this project is important is that dam operator and wildlife preservers could use the information contained in this report to know if fish and wildlife are safe in turbid waters.  They would also know, that if turbidity levels are healthy and increase dissolved oxygen levels, they would have to add turbidity to zoo water so that fish would have more oxygen.
 Water is one of the most important recourses on earth.  Without water most things won’t survive.  An example would be dehydration causes plants, animals, and people to die.  Water is the only natural substance on earth that occurs in all of the states in matter; liquid, solid, and gas.  Water is formed from compound H2O, which means two hydrogen atoms and one oxygen atom. 
 Oxygen is another very important recourse for humans to have.  Without there would be no air to breathe and mankind would die.  Almost everything needs oxygen to live because oxygen combines with other chemicals in cells to produce energy.  When oxygen combines with hydrogen it produces the liquid state of water.
 Most dissolved oxygen comes from the atmosphere.  Dissolved oxygen levels change from day to day as the currents in water change because the currents act to mix the atmospheric oxygen with water.
 Turbidity is the effect of residue from moving solids and is used as a measurement of the clarity of water.  The higher level of turbidity, the dirtier or murkier the water.  Turbidity levels usually increase as it rains because pollutants and other matter get into the water.

  There is a relationship between turbidity and dissolved oxygen.  The level of turbidity does affect dissolved oxygen levels.  The main cause for this experiment is to determine if turbidity helps make dissolved oxygen or not.   This factor is important because then it will be know if wildlife will be safe in high turbidity levels.

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 "Algae," Microsoft Encarta 98 Encyclopedia, 1993
Knap, Brian, Oxygen, Danbury, Connecticut, Grolier Educational, 1996
Mithchelle "et al," Field Manual for Water Quality Monitoring, Dexter, Michigan, Thomson-shore, Inc., 1996
"Oxygen," Microsofn Encarta 98 Encyclopedia, 1993
Rickard, Gram, Water Energy, Milwaukee, Gareth Stevens Childrens books, 1991.
"Solutions," Encarta, 1996
"Solvent," Encarta, 1996
"Turbidity," [online] Available Http://, Tuesday, November 9, 1999
"Water," Encarta, 1998
"Water Sheds, Turbidity," [online] available, Tuesday, November 9, 19999
"Water, the Planet Earth," World Book encyclopedia of Science, 1990




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