Ecologically we’re almost there’

Mother Nature Helping Cleanup

American Association of Petroleum Geologists (AAPG)
Ed Overton
Ed Overton

Ed Overton, internationally renowned chemist and toxicologist, was a mighty popular guy during the aftermath of the Macondo oil spill debacle in the Gulf of Mexico.

The professor emeritus of the department of environmental sciences at Louisiana State University in Baton Rouge, La., not only understands the scientific aspects of the spill, he has the ability to explain the complex details and concepts in layman’s terms to the media and the public in general.

Speaking at the DEG luncheon at the recent AAPG Annual Convention and Exhibition in Houston, the affable Overton presented a number of observations about the spill.

♦He noted that all of the oil in the environment is being degraded. Some of it is even being converted into excess biomass, which is part of the food chain, just more of it now than the natural environment expected to see.

“We must be very careful about remedial activity associated with oil spills because in a marshy environment this activity could cause more damage,” Overton said. “Sometimes the best answer is to let Mother Nature handle it rather than saying humans caused it, so humans should do something about it.

“Some damage is obvious, like oil onshore or on birds, but in the marsh it’s not always that obvious, such as the single cell and multi-cell critters in the marsh that serve as the basis of the food chain for the ones you can see, such as pelicans,” he said. “It will be several years before we know for certain how much damage was done at this basic structure, so we have to live through this and see.

“I’m reasonably optimistic because of the makeup of the oil,” Overton said. “The oil was not as toxic as some projected; this was not the worst case of toxicity makeup.”

♦He noted that once in the environment, oil is subjected to weathering, dissolution, degradation and sedimentation, and these all have one thing in common: they change the composition of the oil as it comes out of the ground.

Generally, the changes begin at the most toxic level, quickly rendering it less toxic.

Because the light oil from the Macondo was released far offshore, the toxicity damage would be muted. The deepwater environment itself is fairly acclimated to oil, given the thousands of natural oil seeps migrating upward from the subsurface.

♦Overton said he doesn’t think there is any evidence that fresh oil came onshore, noting that it would have been weathered.

♦He commented that the oil that wasn’t dispersed would take about four hours to get to the surface.

“Some of it would require tens of hours if it’s broken down into smaller particles as it moves through cracks, say, in the riser, with some of the smallest requiring hundreds of hours to surface,” he said, “and some in the micron size would need hundreds of hours.

“As for the very smallest, the resistance of the water is such they don’t get to the surface,” he said. “So as the oil is dispersed, a lot of it never got up; dispersed oil is dissolved into the water column and can’t come onshore – it’s gone.

“Also, a lot of lighter components are water soluble and can dissolve,” he added. “A lot of the oil was in different physical forms as it got to the surface. There was black oil, emulsified oil – a lot of looks and colors, and in some forms, it doesn’t look like oil.”

He mentioned also that this particular oil contained gas, which caused it to blow out at high pressure.

♦Overton emphasized that by the end of last July there was no visible oil offshore in the Gulf. A suspicious area was observed a few months later near Southwest Pass that was identified in the lab as an algal bloom. Much later, oil spotted off Grand Isle was fingerprinted to identify a different source.

He noted that the bottom line is the spill put an estimated 10,000 miles in harm’s way, yet only 1,100 miles were impacted – with just 550 acres heavily impacted.

The amazingly small 10 percent impact overall, he said, can be attributed to the combination of light oil, its meandering path with no strong currents to carry it ashore and the massive amount of offshore dispersants, which, though controversial, provided the mechanism to prevent thick oil from coming onshore.

Overton emphasized that the Louisiana marshes are a sick area to begin with. He noted, however, that numerous fresh green sprouts can be seen in many places inside the marsh.

He also mentioned the possibility of re-seeding the areas without growth.

♦The overall damage from the spill is still being estimated.

“Ecologically, we’re almost there,” Overton said. “The catches seem to be good, and the seafood has been certified safe to eat.

“I don’t know how long the sociological impact will remain,” he said, “and the economic impact is hard to tell.

“The geologic impact will not be easy to measure, as significant land loss was already there.”

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