Above: Image © Valerie Loiseleux, iStockPhoto.com

When an oil spill occurs in the ocean, like the catastrophe in the Gulf of Mexico, what do scientists do to clean up the toxic mess? There are a number of options for an oil spill cleanup and most efforts use a combination of many techniques.

The fact that oil and water don’t mix is a blessing and a curse. If oil mixed with water, it would be difficult to divide the two.

Think about trying to take the chocolate out of your chocolate milk, how would you do that? However, because crude oil is less dense than water, it spreads out to make a very thin layer (about one millimetre thick) that floats on top of the water. This is good because we can tell what’s water and what’s oil. It’s also bad, because it means the oil can spread really quickly and cover a very large area, which becomes difficult to manage. Combined with wind, ocean currents and waves, oil spill cleanup starts to get really tricky.

Did you know? Crude oil is toxic to almost all living things. Humans get sick from touching it, breathing its fumes, or ingesting it.

Chemical dispersants, or surfactants, can be used to break up big oil slicks into small oil droplets. They work like soaps by emulsifying the hydrophobic (water-repelling) oil in the water (see article on the science of shampoo). These small droplets can degrade in the ecosystem quicker than the big oil slick. Unfortunately, this means that marine life of all sizes ingest these toxic, broken-down particles and chemicals.

Did you know? BP has used more than 850,000 gallons (or about 3.2 million litres) of dispersants to break up the oil leaking into the Gulf of Mexico before it can reach the shore (that’s enough to give 7.7 million Canadians a large Tim Horton's coffee!).

If the oil is thick enough, it could be set fire, a process called “in situ burning”. Because the oil is highly flammable and floats on top of the water, it is very easy to set it alight. It’s not environmentally-friendly though; the combustion of oil releases thick smoke that contains greenhouse gases and other dangerous air pollutants.

Oil containment boom around New Harbour Island, La.
Source: U.S. Navy, Wikimedia Commons

Some techniques can contain and re-capture spilled oil without changing its chemical composition. Booms float on top of the water and act as barriers to the movement of oil. Instead of having a millimetre of oil covering 1km2, a boom could create an oil slick 10mm thick and 1/10 the area, decreasing the affected environment and controlling the spill. Once the oil is controlled, it can be gathered using sorbents. “Sorbent” is a fancy word for sponge. These sponges absorb the oil and allow it to be collected by siphoning it off the water.

However, weather and sea conditions can prevent and hamper the use of booms, sorbents and in situ burning. Imagine trying to perform these operations on the open sea with wind, waves and water currents moving the oil (and your boat!) around on the water.

What about the plants and animals? It’s easy to forget about the organisms in the sea that are under water. Out of sight, out of mind! There is not much we can do to help them. But when oil reaches the shore it impacts sensitive coastal environments including the many fish, bird, amphibian, reptilian, and crustacean species that live there. We have easy access to these areas and there are somethings we can do to clean up. For the plants, it is often a matter of setting them on fire, or leaving them to degrade the oil naturally. Sometimes, we can spray the oil with nutrients (phosphorus and nitrogen) that can encourage the growth of specialized microorganisms. For species that can tolerate our soaps, manpower is needed to wash every affected animal. However, if the animal has tried to lick itself clean, it can die from ingesting the toxic oil.

Did you know? The BP oil spill in the Gulf of Mexico impacted about about 112 kilometres (70 miles) of Louisiana coastline, a little less than the distance from New Orleans to Baton Rouge (128 kilometres or 80 miles).

Unfortunately, there can be many negative economic and social impacts, in addition to the environmental impacts of oil spills and, as you’ve just read, the cleanup techniques are far from perfect. Prevention is the very best cleanup technique we have.

Learn More!

BPGulf of Mexico response

BP/Deepwater Horizon Impact assessment for May 30, 2010

In situ burn video: http://cgvi.uscg.mil/media/main.php?g2_itemId=855618

Article first published on June 3, 2010.

Laura Hill

I have been interested in science for my whole life.  Growing up with a pharmacist mother and an electrician father, the sciences were ingrained in me from the get-go. Nearly everything we do and see has a scientific explanation: the chemistry of cooking, the mathematics of music, the physics of sport.  My favourite however is the interaction between all living things on earth. I graduated from high school knowing I was meant to become a scientist. Because of my extracurricular sports, I was intensely interested in anatomy, so I went into a human kinetics program.  Having transferred in my second year to a different university, I ended up in a different program: biology.  This was a blessing in disguise.  Mandatory courses included genetics, anatomy and physiology of plants and animals, and ecology.  Ecology is my passion, and I didn't know it until 2nd year university. There's nothing like field work in the summer! I have used my knowledge of the environment to work on studies and projects in China, Ecuador and Costa Rica.  I am excited about my future in environmental science and where I go next!

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