Oil Spill Cleanup

Introduction/Motivation

The Exxon Valdez oil spill was one of the largest oil spills in recorded history. It took four summers to clean up the spill. Why is it so hard to clean up oil? Why does it take so long? One reason is because of its low density, which causes oil to float on top of water. In addition, oil is hydrophobic (afraid of water) so it does not like to be in water. Oil is more likely to stick to anything other than water; which explains how it pollutes animals, beaches and rocks rather than mixes with water.

In some cases, people rely on the environment's ability to dilute pollutants. For example, car exhaust is very toxic, but we depend on the environment's ability to mix the exhaust with the air in the atmosphere. Although it is not the best method of dealing with pollution, diluting the exhaust in the air actually reduces its toxicity. We are not harmed (that is, poisoned) by carbon monoxide while walking alongside a car, but we would be if we sat in a closed garage with the car running. The ocean works in the same way as the atmosphere. Some wastes are unavoidably disposed of in the ocean. Runoff from populated areas, highways and chemical-laden fields contains various types of pollution, and it all ends up in the ocean at some point. The ocean can dilute the runoff to a certain extent—resulting in no immediate threat to inhabitants. Because of its hydrophobic properties, however, oil will never easily dilute into the ocean, which makes it very hard and time-consuming to clean up spills.

Oil spills, like most environmental issues, become contentious political situations. Many questions are asked, and blame is given. Who is responsible for the pollution? Who should pay for the cleanup? How much should they pay? How should the spill be cleaned up? These and other questions are often highly-debated issues. For example, most oil companies argue that the least expensive clean-up option should be used; whereas environmentalist and people impacted by oil spills want the method that works the best—no matter the cost. In the case of the Exxon Valdez oil spill, Exxon paid a tremendous amount of money for the initial cleanup, although a lot of oil still remains in and around Prince William Sound. Although Exxon has already paid $1.1 billion in punitive damages to many of the local people who were negatively affected by the spill, they are still being sued for more. Another example of how complicated environmental issues can become is that even decades after the spill occurred, lawyers are still debating how much money to pay the 32,000 fisherman who were out of work because of the Exxon Valdez oil spill.

Today, we are going to create a model of an oil spill. You are going to play the role of environmental engineers and use different technologies to clean oil from water. You will use booms and skimmers (used to contain the oil and avoid spreading); absorbents (used to soak up the oil and avoid spreading); and dispersants (chemicals used to break down the oil). You will collect data on oil removal and then look the cleanup methods used from the viewpoint of both the environmental engineer and the oil company owner. How do you think they will feel about the oil spill cleanup?

Materials List

Each group needs:

• 1 aluminum pie pan

• 1 large stone that fills ~20% of the pie pan; ask students to bring from home during the two weeks leading up to class

• 2 bird feathers, available from hobby shops

• 1 plastic spoon, for skimming oil from the pie pan

• 1 small graduated cylinder, ~20 ml, for placing spoonfuls of skimmed oil/water

• 1 small funnel, for adding skimmed oil/water to test tubes

• 4 oil absorbing cloth pads, for absorbing oil; either cut a big sheet into smaller squares or use cotton balls/pads

• 1 small squeeze bottle of "grease-fighting" dishwashing detergent labeled "dispersant", such as Dawn®

• Oil Spill Worksheet, one per group

For the entire class to share:

• pitchers/jugs of water

• ~100 ml dark vegetable oil in a plastic squeeze bottle; if necessary, oil can be dyed with liquid food coloring

• plenty of paper towels

• 1 large garbage bag, for cleanup

1. Model setup: Have student pairs set up their oil spill pans. Have them place the pan on the table and put the stone in the middle of the pan. Add water to the pie pan until about half full. Tell students: In this model oil spill, the stone represents the land and the water represents the ocean. One objectives for your cleanup effort is to keep the oil away from the land.

2. Begin testing: Have them place a small amount (~1 tablespoon) of oil (dark-colored vegetable oil) in the pie pan. What happens? Have them watch closely to see if the oil moves toward the land.

3. Have them place a feather in the oily water. After 30 seconds or so, remove the feather and examine what the oil has done to it. What impact can they conclude that oil has on birds?

4. Have them use the skimmer (spoon) to try and remove the oil, pouring into a graduated cylinder. (Note: Demonstrate how to use the spoon to gently skim off the top layer of oil without removing spoonfuls of water). Ask them to determine approximately what percentage of oil and what percentage of water they removed? Record their measurment number on their worksheets. (Note: Obtain the number from the graduated cylinder since the oil and water will separate in the cylinder.)

5. Have them place a score (H = high, M = medium, L = low) on their worksheets for the cost and effectiveness of skimming if they were either the environmental engineer or the oil company owner.

6. Next, have them use the absorbent cloth to absorb the oil. Ask them if they think the cloth is expensive? How well did it work?

7. On their worksheets, have them rate the cloth in terms of effectiveness (H, M, L) and cost (high cost, medium cost, low cost) if they were either the environmental engineer or the oil company owner.

8. Lastly, have them place 1 or 2 drops of "dispersant" into the pie pan and stir it around with a spoon. Expect them to notice that the oil appears to break up into small droplets. Is this an effective means for cleanup?

9. Have them use dispersant on the feathers to see what effect the oil now has on them. Expect the feathers to be fine; the dispersant worked!

10. Have them rate the dispersant in terms of cost and effectiveness if they were either the environmental engineer or the oil company owner.

11. Have students make two vertical bar charts on their worksheets showing the relationship between low, medium and high effectiveness (one of the bar charts) for each cleanup method and cost (the other bar chart) if they were an environmental engineer or an oil company owner.