Oil spills are cleaned up by using booms and skimmer equipment, dispersants, and the introduction of biological agents to speed up biodegradation.
Have you ever seen a rainbow-colored sheen in parking lots during the rain? That is similar to how an oil spill looks in the ocean. An “oil spill” is literally the spilling of liquid petroleum hydrocarbon into the marine or terrestrial ecosystem. You have likely heard of the Exxon Valdez oil spill in Alaska (1989) or studied it during your Environmental Science lessons.
That tragedy is still known as one of the worst oil spills in the history of the petroleum industry, followed by the Gulf of Mexico or Deep Water Horizon spill of 2010. Although these were major disasters that received international attention and sparked global outrage, there are reportedly 20,000 oil spills every year around the world!
What causes an oil spill?
Oil spills are a result of both natural and man-made accidents. In the case of natural factors, oil spills can happen due to hurricanes in the ocean. Oil spills are mainly caused by accidents involving pipelines, refineries, tankers, barges, storage and drilling rigs. They can also happen due to careless handling of equipment, equipment breaking down or being deliberately damaged by terrorists, military activities or illegal dumping.
So… what happens after the oil gets spilled?
It’s important to note that the behavior of oil depends on the kind of oil being discussed. We’ve all heard before that oil and water never mix, as they are immiscible. Generally speaking, oil floats on water (saltwater), but in rare cases, heavier oils may actually sink in freshwater.
As soon as oil spills, it starts spreading in water. As it slowly evens out, it forms a thin layer called an oil slick. Finally, it becomes an even thinner layer called a sheen (what we seen in parking lots in the rain).
What harm does an oil spill cause?
It’s interesting to note that not only oil spills, but also their cleanup operations, can cause harm to the environment and marine life. Oil harms both internally and externally when it comes in contact with marine life. Since oil has poisonous constituents, it can harm internally by inhalation and ingestion, and externally via skin contact and eye irritation.
Oil also coats the feathers and fur of birds and animals, hindering their homeostasis (regulation of body temperature). Since most oils float, sea otters and sea birds are most affected due to being in contact with surface water. There are rehabilitation centers set up in the U.S to care for birds and mammals that have been exposed to excessive amounts of oil.
Can different types of oil spills have different impacts?
As already discussed, there are different types of oil, so they naturally behave differently in water bodies and affect marine life differently too!
Oils like diesel and gasoline are known as light oils. The silver lining of such oil spills is that, since light oils are volatile, they evaporate quickly after the spill. This means that the oil will not remain in the water body for very long, but certain light oils are explosive and toxic, meaning they can kill any marine creature simply by coming in contact with it. It’s even dangerous for humans who inhale their toxic fumes.
Bunker oils, which are used to fuel ships, are heavier oils. They are black, sticky and can persist in a water body for a much longer time until removed. Although they rate high on persistency, they are low on toxicity, as compared to lighter oils. The short-term threat caused by such oils is that they coat or smother animals and fish.
After days and weeks, such oils usually harden and become similar to asphalt. The long-term harm is that this can cause tumors. Once coated on the feathers of birds, it can lead to hypothermia and death, since it hinders homeostasis.
Finally, how do we clean up an oil spill?
The cleaning of oil spills depends on the type of oil, the location and the weather conditions. The spilling of crude oil versus refined oil would require two different cleanup approaches. Similarly, spills in seawater vs. freshwater are different. Weather conditions like the temperature of air and water, wind speed and its direction, currents, tides, and the presence of ice all affect clean up. However, there are primarily four methods of cleaning up an oil spill.
If the oil spill is not near the shore or affecting the marine industry, it’s best left alone to be dispersed naturally. As we learned before, light oils quickly evaporate, so light oil spills are left the way they are. The wind, sun, waves and currents will naturally deal with the oil. Sounds like taking no responsibility, right? Well, hold your horses, there are more techniques.
Physical barriers: Oil spills are surrounded by booms to prevent the oil from spreading to coasts, harbors and marshlands. After containing the oil, it is collected using skimmer equipment. Booms are either used to isolate a slick or block its passage to important areas. Skimmers then work inside the boundary formed by the booms to suck the oil back into storage tanks.
After this process, workers use sorbents to absorb the remaining oil. Sorbents come in three types. Natural organic sorbents are straw, hay, peat moss and sawdust. Natural inorganic sorbents are clay, volcanic ash and sand. Synthetic sorbents are polypropylene and polyethylene.
Dispersants: Dispersants speed up natural biodegradation by breaking down the oil. This technique is most effective when used within a couple of hours of the oil spill. Unfortunately, these substances cannot be used for all kinds of oil spills. Dispersants are useful for preventing oil from entering important ecosystems, but since it’s a chemical, it can also enter the food chain and cause harm.
Introduction of biological agents to speed up biodegradation: This is a natural method, as compared to dispersants, but somewhat similar. Adding nitrogen and phosphorous stimulates the growth of microorganisms that naturally break down the oil into fatty acids and carbon dioxide.
Prevention is always better than a cure. Even though there are established techniques to clean up oil spills, it is best to prevent them entirely. Stricter laws and regulations on the petroleum industry can prevent manmade accidents that cause serious oil-spill pollution. This will also help protect the entire marine ecosystem, from birds and fish to aquatic plants and vital microorganisms!