Low concentrations of oxygen and nutrients slowing biodegradation of Exxon Valdez oil spill

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Washington, January 18 (ANI): In a new research, scientists have found that the combination of low concentrations of oxygen and nutrients in the lower layers of the beaches of Alaska's Prince William Sound is slowing the aerobic biodegradation of oil remaining from the 1989 Exxon Valdez spill.

Considered one of the worst environmental disasters in history, the Exxon Valdez spilled more than 11 million gallons of crude oil into Alaska's Prince William Sound, contaminating some 1,300 miles of shoreline, killing thousands of wildlife and severely impacting Alaska's fishing industry and economy.

In the first five years after the accident, the oil was disappearing at a rate of about 70 percent and calculations showed the oil would be gone within the next few years.

However, about seven or eight years ago, it was discovered that the oil had in fact slipped to a disappearance rate of around four percent a year and it is estimated that nearly 20,000 gallons of oil remains in the beaches.

The researchers, lead by Michel Boufadel, director of the Center for Natural Resources Development and Protection in Temple's College of Engineering, have been studying the cause of the remaining oil for the past three years.

Boufadel said that the beaches they studied consisted of two layers: an upper layer that is highly permeable and a lower layer that has very low permeability.

He said that, on average, water moved through the upper layer up to 1,000-times faster than the lower layer, and while both layers are made up of essentially the same materials, the lower layer has become more compacted through the movement of the tides over time.

These conditions, according to Boufadel, have created a sort of sheltering effect on the oil, which often lies just 1-4 inches below the interface of the two layers.

Boufadel and his team found that on average, the nutrient concentration in the beaches was 10 times lower than what is required for optimal aerobic biodegradation of oil.

They also found that the oxygen levels in the beaches are also insufficient to sustain aerobic biodegradation.

Using groundwater hydraulic studies, the researchers found that the net movement of water through the lower layer of beach was outwards, so it is preventing oxygen from diffusing through the upper layer to where the oil is located.

Boufadel and his team are now exploring ways to deliver the much needed oxygen and nutrients to the impacted areas in an effort to spur aerobic biodegradation of the remaining oil. (ANI)

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