Turbidity Tube (Mary Eckel)

Author

Mary Eckel 

Los Angeles River School

Principles

Earth Science

Environmental Science

Standards

HS-ESS2-5: Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.

Materials needed

Turbidity Tube

Water Sample

Bucket to collect water sample

Procedure

  1. Collect a large amount of water in a bucket (or other container).  Make sure to collect flowing water, and do NOT disturb the sediment on the bottom of the river bed .  Do not include algae floating on the top.
  2. One person should pour the water into the tube, while another person looks down from the top through the water column.  Rotate the tube while looking down at the image.
  3. Stop adding water when you can no longer see the black and white pattern on the bottom of the tube.
  4. Record the depth at which you can no longer see the bottom of the tube.  If the tube has been filled and you can still see the bottom, record as > total depth of the tube.
  5. You may empty water back into the river and have two students repeat steps 1-4. Recoed an average of your findings.
  6. Find the Q-value for your data.

Explanation

Turbidity is the relative clarity of a liquid.  Turbidity is caused by particles of varying sizes scattering or absorbing light.  This can cause a cloudy appearance.  Turbidity can result from suspended particles, dissolved substances (such as oxygen), phytoplankton, and other microorganisms. Once you measure the turbidity of the water, use the conversion chart and the graph below to find the Q-value for the water sample.  According to Friends of the Chicago River, you can look at the Q-value like a test score. Anything below a 50 is a failing grade, the higher the number the better the water quality.


Questions

  1. What is a Q-value and why is this important?
  2. What factors can affect the turbidity of the LA River? Why?
  3. If we take water samples for different areas of the LA River, do you think the values will be similar? Why or why not? Explain.

Everyday examples of the principles illustrated

Turbidity is important when looking at the quality of drinking water (especially in waterborne disease outbreaks) and the health of rivers and streams.

Photos


Movies

 

References 

EPA: Importance of Turbidity
Find the Q-Value

Friends of the Chicago River


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