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Weathered diesel from oil spills more toxic to marine plants than previously thought

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April 16, 1993 Share This!

RICHLAND, Wash. — A new study has revealed that diesel from marine oil spills can become more toxic as it weathers, rather than relatively inert as previously believed. In addition, the recently concluded six-month study shows the fuel can have an impact on kelp beds over a relatively short period of time.

The $42,000 study was conducted by the Pacific Northwest Laboratory for the Washington State Department of Natural Resources as a result of the July 1991 oil spill off Cape Flattery, Washington, by the Japanese fishing vessel Tenyo Maru. The Department of Natural Resources was acting as Natural Resources Damage Trustee for state-owned aquatic lands and associated vegetation. The research was coordinated by PNL's Marine Sciences Laboratory at Sequim, Washington.

"The most surprising result from our study was the effect of weathered diesel oil on Nereocystis leutkeana, or Bull Kelp," said Dr. Ronald M. Thom, manager of PNL's marine resources group. The PNL team found that the weathered diesel was the most toxic of all the petroleum products studied, killing the kelp after as little as four hours of exposure.

In the past, researchers have not been able to establish a biological link between oil spills and marine plants. This study is the first time researchers have documented that weathered diesel oil is causing problems for kelp plants.

The researchers studied concentrated diesel fuel floating on top of the water. Exposure to the sun weathered the fuel, which then was observed as it coated the kelp.

"We don't know yet the implications of the weathered diesel as it dilutes in the seawater. We also don't know the implications further up the food chain -- that would be the next level of research," said Dr. Thom.

The Pacific Northwest Laboratory in Richland and Sequim, Washington, is a national multiprogram laboratory operated for the U.S. Department of Energy by Battelle Memorial Institute. Battelle is an international technology organization that serves industry and government by developing, commercializing and managing technology.

Tags: Energy

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