How Oil Breaks Down in Water

Popular Mechanics explains how the oil spill may be taken care of by the ocean.

How Oil Breaks Down in Water (Cassie Rodenberg, 5/7/2010)

"Nature has its own chemical processes to minimize oil's impact in seawater—can human dispersant efforts measure up?

"Initiatives to scrub the Gulf of oil are moving forward. One method includes spraying chemicals to break up and sink globs of oil before the slick spreads to the shorelines—but using chemicals to clean up the ocean is controversial because the environmental consequences are unknown. The sea has its own way of handling the problem, but researchers worry that the water's processes won't act fast enough to save coastal shores from damage. Of course, science informs the debate. Here's what happens on a molecular level when oil hits ocean water.

"As soon as oil hits water, the ocean begins its deconstruction. In fact, the marine environment handles oil much like a human body handles alcohol: destroying, metabolizing and depositing the excessive compounds —in oil's case, hydrocarbons—then transforming the compounds into safer substances, says Stanislav Patin, chairman of the Aquatic Toxicology Committee under the Russian Academy of Sciences and international expert on marine pollution.

"Here's how it breaks down.

"In a 10-minute span after spilling into the sea, 300 gallons of oil can spread to a radius of 160 feet and create a slick a fourth of an inch deep. After that, how far and fast the oil spreads depends upon the water's surface tension—how much the molecules in the water are attracted to one another—and the oil's thickness.

"The day after it enters the water, chemicals in the oil begin to transform, both at the water's surface and farther into the water column. Trace elements lurking in water can speed or slow the process while the sun fuels the breakdown, decomposing even the most complex of oil's components over time. The warmer the water temperature and the more sun exposure, the faster the oil breaks down.

"During the first few days after a spill, between 20 to 40 percent of oil's mass turns into gases, and the slick loses most of its water-soluble hydrocarbons—what's left are the more viscous compounds that slow down the oil's spread across the water.

"When components of crude oil evaporate and its lighter fractions dissolve or are chemically transformed, oil clumps form. These sticky masses are found in all types of water environments, in open and coastal waters and on beaches. They have an uneven shape and can measure tenths of inches to 4 inches in length. The oily masses serve as a base for developing bacteria and one-celled algae, while invertebrates such as crustaceans, resistant to the impact of oil, use them as shelter. These clumps can exist from months to years in enclosed seas and for years in the open ocean—eventually, they degrade." [The article continues.]

So, the ocean, the sun, oil-loving bacteria and algae can break down the spilled oil, given time. As the article points out, the worry is that "the water's processes won't act fast enough to save coastal shores from damage".

The oil blobs have washed ashore, as everyone feared and knew. Why the affected state governments didn't build a barrier to prevent the oil from washing up the shore is a mystery to me. What were they waiting for? A permission to do something from the federal government, whose head has said he's been in charge and took two vacations since the spill (and will probably take more until the relief wells start to work)?

Popular Mechanics has a beautiful picture of oil spill from the air. Vermilion against deep blue - it is artistic.


(Oh I get it now. The color of shirts those clean-up crew were wearing when they suddenly materialized just in time for President Obama visit the other day! They were either wearing blue shirt or red shirt. The color of the spill! They sure looked stylish, with white pants and hats to match the white sand, and no protective masks.)

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