Can A One Billion Pound Oil Spill Disappear?

The BP oil leak disaster lasted 85 days. A gooey, toxic, and stinking spill kept spreading on surface waters. Parts were converted to tiny oil globules by dispersants. Another fraction evaporated and kept changing its composition under the impact of high water temperatures and intense sunshine.

Surface winds, water currents, wave action, and stormy seas kept spreading the spill over a quickly growing area. Contiguous oil patches soiled wetlands, estuaries, beaches, and shores of Louisiana, Mississippi, Alabama, Florida, and Texas. Globs in a multitude of sizes washed ashore and fouled beaches, contaminated wetlands, dirtied estuaries, and polluted shores.

Dispersants were injected in huge amounts into the gushing oil jet and atomized escaping oil into microscopic droplets that will take months and years to reach the surface. The suspended oil will influence marine life by becoming a semi-permanent part of the water that fish and other creatures must ingest to derive the oxygen they need for survival. Most dispersants are water soluble and become part of the watery medium that all marine life depends on for procreation and existence. At least one of the major ingredients of dispersants has a very large biological oxygen demand; this ingredient will deplete the water column of dissolved oxygen.

After tropical storm Bonnie moved over the Gulf, the media are reporting that the oil had mostly disappeared. How can that possibly be?

Science knows that mass never disappears. But mass can change into many forms, compounds, and other disguises. If one looks at the seemingly disappearing oil spill under this perspective, one can do some old-fashioned accounting. At the end of tallying all possible disguises one always must end up with the same number; the amount of leaked oil during the 85 days of gushing from the dysfunctional blow out preventer.

BP and the administration have slowly increased their estimate of the leaking oil flow from 1000 barrels per day in the first week to 80,000 to 100,000 barrels per day at closure. There is one anomaly in the reporting; the flow of leaking oil supposedly increased after the unsuccessful "junkshot". This does not make any sense. Taking this anomaly into account, one may come close to an actual leak rate of at least 90,000 barrels of oil per day for 85 days. A multiplication results in an oil leak of roughly 7.5 million barrels or a total of more than 300 million gallons of spilled oil!

One can find arguments for adjusting this number downwards or upwards. Realistically, we will never know for sure how much oil gushed into the Gulf.

Looking ahead, one can hope that the pending top kill will be successful and that the permanent cementing and closure of the reservoir can progress under more favorable working conditions.

Proceeding from the number of 300 million gallons, one can now try to find out how much oil is still floating on the surface of the Gulf.

Some of the oil disappeared into thin air; literally. Lighter fractions of the oil began evaporating already on their way from the reservoir to the surface of the Gulf. At a pressure of approximately 9000 psi in the reservoir, several hydrocarbons can still be liquids. On the surface of the Gulf, at oil temperatures approaching 100 degrees F and at an atmospheric pressure of merely 14.7 psi, several oil compounds just evaporate. One cannot see vapors, one can only smell them. They can be toxic in higher concentrations and some of the cleanup crews felt their toxic effects.

There is no information available to accurately know the evaporated oil fraction. A fair guess is that 25 % to 40 % of the leaked oil escaped into the air, which quickly spread across the Gulf, the Atlantic, and parts of the U.S. Assuming a median amount of 32.5 %, one calculates that close to 100 million gallons were vaporized, ended up in the Earth's atmosphere, and are being oxidized slowly.

Huge oil plumes have been detected below the surface of the Gulf. These plumes are formed by dispersants that create finely dispersed oil droplets, which can rise through the water column only at the very slow speeds of tiny droplets. Information provided by the administration puts the amount of dispersants injected directly into the jet of oil and gas emerging from the broken blow out preventer at 1.5 million gallons of dispersants. These oil plumes may contain as much as 30 million gallons of finely dispersed oil when assuming that each gallon of dispersant breaks up as much as 20 gallons of oil. It may last months and years before this finely dispersed oil reaches the surface, eventually coalesces, and produces very small tar droplets that float on the surface. Only time will tell the actual facts.

Small amounts of surface oil may be picked up by hurricanes and tropical storms and may be spread over huge land and sea areas. Most of the oil will stay on the surface of the Gulf and will assume the shape of small tarballs with diameters in the range of one quarter of one inch to somewhat larger than one inch.

The volume of these small tarballs will be close to 170 million gallons. With oil having a density lower than water, the mass of floating tarballs exceeds 1000 billion pounds.

These tarballs will most likely not do too much damage to marine life because they are becoming chemically inert by weatherization. They still will not look good on a clean towel or a tanned body.

Beach communities that depend strongly on tourism will have to prepare themselves for years of daily beach maintenance. Vehicles, equipped with large vacuum equipment, must remove the top layer of sand, sieve it, thermally clean it, and redeposit the recovered, virgin sand.

Dependent on winds and water currents, tarballs will occasionally appear in higher concentrations. Protecting beaches with boom will become a more common sight. However, boom designs must be changed to make them more effective in rough waters and make repetitive deployment and retrieval less labor intensive and more efficient.