Aquatic Field Investigation
Materials and Methods 8
Sediment Analysis


At this station your team will examine the different types of sediment at your aquatic site. The color, odor, and particle size of the sediment provide important information about the health of an aquatic environment. Sediments are particles deposited onto the bottom of an aquatic site through the action of rivers, glaciers, or wind. The kinds of sediments deposited are important, because they help determine the drainage of the site. The finer the sediments, the less the water is able to drain through the site. Some drainage is beneficial, because de-oxygenated water or heavier pollutants can drain away. A well-drained aquatic site usually supports a larger variety of organisms than a poorly drained aquatic site.

Materials

For the Pre-Field station:

For the Field Experiment:

Methods

Pre-Field Experiment:

To remove layers of sediment from the water, you will use an instrument called a corer. Your corer will consist of a PVC tube and a long rod.
  1. To practice using your corer, find a location in the school yard where the ground is not too hard. Hold the tube perpendicular to the surface of the ground. Push it down as far as you can into the ground. Use a hammer if necessary to get the tube into the ground. If the soil is too sandy or soft, wet it with water so that the sample will pack into the corer.
  2. Remove the tube from the ground. Insert the rod into the tube and push the sample out of the tube onto several large sheets of newspaper.
  3. Examine the sample to see if it contains different types of materials (sand, pebbles, large rocks, other objects). Try to categorize the materials you found using Master 4d, "Sediment Sizing Chart."

Field Experiment

You will be using the corer you used in the Pre-Field Experiment to examine the sediment in different locations at your aquatic site.
  1. Take your first sample at the edge of the water at your aquatic site. Hold the tube perpendicular to the ground and press down. Use a hammer if necessary.

  2. Remove the tube from the ground and use the rod to push the sample onto the newspaper.
  3. Examine the sample to see if the sediment contains particles of different sizes. Describe each element of the sediment, using the sediment sizing chart in Master 4d. Record your observations in your JASON Journal.
  4. Describe the texture of each element of the sediment. Rub a sample of each layer between your fingers. Does it feel smooth? Gritty? Sticky? What else do you notice about your sample (e.g., does it have an odor?) Record your observations in your JASON Journal.
  5. Draw your findings in the Sample 1 column of the table below. Use the illustrations in Master 4d, "Sediment Sizing Chart," as a drawing guide. For example, if the very top of your sample contained pebbles, draw pebbles in the first row of the column marked Sample 1. If there was a large layer of coarse sand under the pebbles, draw coarse sand in the second and third rows of the column marked Sample 1. If the bottom of your sample was silt, draw silt in the last row of the Sample 1 column.
  6. Repeat steps 1Ð5 at a site that is 5 meters away from the water. Fill in the column labeled Sample 2 on the Site illustration above.
  7. Repeat steps 1Ð5 at a site that is 10 meters away from the water. Fill in the column labeled Sample 3 on the Site illustration above.
  8. Did each of your three samples contain similar types of sediment? How is the sediment within each sample different? Is this the same for all samples? How do the layers in one sample compare to another (for example, was the bottom of every sample the same or different)? Record your answers in your JASON Journal.

Conclusions

After you have conducted both the Pre-Field and Field Experiments, discuss the following questions within your research team and record your answers in your JASON Journal.
  1. How is the sediment in an aquatic environment sampled, and what does itindicate about the water's ability to support life?
  2. What new questions do you have?
  3. Look for more answers to your questions in JASON Online Systems, the library, and science text books.


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Gene Carl Feldman (gene@seawifs.gsfc.nasa.gov) (301) 286-9428
Todd Carlo Viola, JASON Foundation for Education (todd@jason.org)
Revised: 3 Nov 1995