Summer Research Program at Columbia University

Matthew A. Nanes

Park West High School, Manhattan

- 2002

Investigating How Pollutants Travel through Groundwater

Background information

Students should understand porosity and permeability and be able to discuss factors that control each. They should be familiar with subsurface water supplies such as aquifers and artesian wells. [9-12 Content Standard D- Geochemical Cycles]

In this investigation students will determine how pollutants can travel though sediment as well as the method of removal.

Problem:

Aim: How do pollutants travel through the subsurface and what methods are used for removal? [9-12 Content Standard A- Understandings about scientific inquiry]

Materials (per group)

1 plastic cup ¾ filled with small gravel

1 plastic cup ¾ filled with water

1 plastic cup with small holes around the bottom

1 plastic cup

food coloring

pump dispenser from lotion/soap bottle

Procedure

Ask the students to design an experiment within their group that can determine how pollutants move through the subsurface and methods for removal. [9-12 Content Standard A- Design and conduct scientific investigations] After allowing the students to design their own experiment for about 10-minutes then allow the groups to report on their methods. [9-12 Content Standard A- Communicate and defend arguments]

When the groups have finished reporting decide which method will be most appropriate and then begin the experiment with the procedure below. Hold the paper cup with the holes in the bottom over the cup containing the gravel and pour enough water to fill the gravel filled cup until all but the top 1 cm of the gravel is saturated.

Question: What do you think the water in the gravel filled cup represents?

Answer: This represents the groundwater in our environment

Take the cup filled with gravel and dig out a hole in the center to create a lake in the middle. The lake should be about ¼ full of water. (Have students take note of the relationship between the water level in the lake and how it corresponds to the water level in the gravel.

Add 2 drops of food coloring to the gravel on one side of the lake. (Not in the lake itself)

Question: What do you think the food coloring represents?

Now hold the cup with the holes in the bottom over the gravel filled cup. Add water to the cup with the holes so that it drips onto only that portion of the lake-side where the food coloring was dropped. Observe what happens to the coloring. Continue adding water until the coloring can be seen in the lake and beneath.

Question: What does this demonstrate?

Answer: This shows how contaminants can move from soil (gravel) into the groundwater, (water beneath the gravel), and in turn, to stream and lakes (visible lake water).

Now it’s time to clean up this pollution from the soil

Insert the pump into the gravel until it hits the bottom of the cup, opposite from where the contaminant was added. Pump water into the paper cup without holes. Note the color of the pumped water. Continue to pump water until the color of the pumped water changes to the color of the contaminant. Add small amounts of clean water to the model lake while pumping. Continue adding water until the water pumped becomes clear.

Question: What does this process illustrate?

Answer: This shows a typical method of cleanup used by the EPA known as “pump and treat”. A well is dug into the contaminated groundwater and then the water is pumped and treated. After extensive pumping and replacement with clean water, eventually the contaminant is effectively removed.

Analysis and Conclusions

At this point discuss how pollutants can easily enter water supplies when not directly introduced to them. Discuss methods of how these pollutants can be prevented from ever entering the soil. Discuss real world examples of mining companies and other illegal dumping that has led to such pollution. [9-12 Content Standard F- Natural resources, Environmental quality, Natural and human induced hazards, Science and technology in local, national, and global challenges.]

Assignment:

Have students research similar occurrences of pollutants being spread through the subsurface. Have them research what Superfund means and relate it to this lesson. Provide a list op some of the most severe cases of pollutants contaminating water supplies and discuss what is being done or already has been done to remediate the problem. . [9-12 Content Standard F- Environmental quality, Natural and human induced hazards.]