Gulf oil dispersants: helpful or harmful?

Scientists are wondering if the chemicals dispersed to mitigate the spill will hinder oil-eating microorganisms that could clean it up.
Written by Deborah Gage, Contributor

Now that hundreds of thousands of gallons of chemical dispersants have been pumped into the Gulf of Mexico to try to stop the oil leak from reaching the fragile coastal marshes of Louisiana (too late), scientists at U.C. Santa Barbara are racing to figure out how the dispersants might impact oil-eating microbes that could help clean up the spill.

Dr. David Valentine and his team have been given a "rapid response" grant from the National Science Foundation -- meaning the NSF has cut its application turn-around time from months to a few days -- and the team is now taking samples from the spill site, both onshore and offshore.

"Right now, we don't get it," Valentine said in an interview this morning, when I asked him how complicated this spill is compared to the natural oil seep he's worked with off the coast of Santa Barbara. "It has great complexity. Over the coming weeks things will come to light, and we'll see what's happening with the oil beyond the pictures you see in the news."

Oil is a very complex substance, according to research Valentine has done so far. By 2008, for instance, his team had traced 1,500 different compounds in the Santa Barbara oil seep -- at least 1,000 of them eaten by microorganisms. From UC Santa Barbara:

The microbes prefer the lighter compounds of oil, the gasoline part of the black goo. They tend to leave behind the heavily weathered residue, which is what makes its way to the surface and, sometimes, to the beaches in the form of tar.

"There always seems to be a residue," Valentine said. "They (bacteria) hit a wall. There seems to be stages in which they eat. There's the easy stuff ––the steak. And then they work their way to the vegetables, and then garnish, and then they stop eating after awhile. Just depends on how hungry they are and what's fed to them."

Adding chemical dispersants, as was done with this spill, adds even more complexity, Valentine said today, because "many micro-organisms produce their own chemical dispersants, and we don't know how the (added) chemical dispersants interact with the natural ones.

"There are lots of chemical nuances between different dispersants," he said, "whether they have a negative charge or no charge, how they form in the water, are these organisms really evolved for their own dispersants and will some chemical dispersants inhibit them? We have no evidence yet."

Analyzing the oil samples from the Gulf spill will take Valentine's team months, unfortunately, although Valentine says he's got some sophisticated tools to help him tackle the job.

The scientists will be using 2-D gas chromatography developed by Chris Reddy, a marine chemist at Woods Hole Oceanographic Institution, to resolve thousands of compounds in the oil. Traditional techniques might resolve 200 compounds, Valentine said.

Again, from UC Santa Barbara:

Typically, chromatography involves heating up a sample and putting it into a column around 60 meters long. Compounds are then separated based on their boiling points, which works well with light crude oil...But, with the two-dimensional test, the compounds are put into a cooled trap, for about 10 seconds, and a flash pulse of hot air releases them into the second column. This two-dimensional separation allows the researchers to pick out the many thousands of compounds [NOTE: which they can analyze with algorithms].

The team will also try to detect and analyze the key genes that microorganisms are using to degrade the oil, in hopes of identifying which types of organisms are involved.

That work could be used by others to create oil-eating microorganisms especially designed for the gulf, Valentine said.

EPA officials are now surveying the damage in the gulf and will be holding a press conference on chemical dispersants this afternoon. The EPA has already directed BP to use a less toxic dispersant -- here is BP's latest response. If there's new information, I'll add to this post.

So far, though, we don't know enough about what impact dispersants might have on oil-eating microorganisms or other aspects of this spill.

Previously on SmartPlanet:

This post was originally published on Smartplanet.com

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