LINGERING LEGACY OF VALDEZ OIL SPILL
Review paper finds impact of tanker disasters lasting longer than expected
When the Exxon Valdez oil tanker ran aground in Alaska's Prince William Sound in March 1989, it released 11 million gal of crude oil into a vibrant coastal ecosystem. Based on other oil spills, environmental experts envisioned that the affected areas would recover within a few years following the initial cleanup and biodegradation of most of the residual oil.
Although ExxonMobil and some scientists monitoring the long-term effects of the spill believe this recovery has happened, a new review of Prince William Sound research projects concludes that, while not immediately visible, a surprising amount of oil from the Valdez persists in some shoreline sediments [Science, 302, 2082 (2003)].
||OILED A pit excavated along Prince William Sound last summer reveals residual subsurface oil from the Exxon Valdez.
PHOTO BY NOAA/NMFS AUKE BAY LAB
The review, led by ecologist Charles H. Peterson of the Institute of Marine Sciences at the University of North Carolina, Chapel Hill, suggests that the toxicity stemming primarily from polyaromatic hydrocarbons (PAHs) in the oil continues to affect the recovery of sea otters and some birds in places where the oil is most persistent. The paper calls for a paradigm shift in assessing the long-term ecological risks of oil spills and water pollution in general.
A crucial line of supporting evidence is a study led by chemist Jeffrey W. Short of the National Oceanographic & Atmospheric Administration's Auke Bay Laboratory, Juneau, Alaska. Short, a coauthor of the Science paper, reports an estimate of Valdez oil remaining on Prince William Sound beaches following a field study that involved digging some 9,000 test pits at 91 random sites [Environ. Sci. Technol., 38, 19 (2004)].
After the original cleanup was complete in 1992, about 2% of the spilled oil was thought to remain in the environment, Short says. In the ES&T paper, Short and coworkers estimate that about 0.2% of the original oil remains--several hundred times more than expected. The conclusion is that animals and plants dependent on intertidal areas have remained at a substantially higher risk of PAH exposure than previously thought.
Chemistry professor David S. Page of Bowdoin College, Brunswick, Maine, who has published ExxonMobil-sponsored studies on the sound since 1989, disputes the design and conclusions of the ES&T study and the conclusions of the Science paper. Page and coworkers conclude that remaining PAH levels they have measured "are far below those known to cause harm to birds and wildlife that forage on the shorelines."
In a press release, ExxonMobil Vice President Frank B. Sprow states that many papers "strongly support our position of a recovered ... ecosystem" and dispute the view taken in the Science paper.
The new report could have a bearing on the $100 million "reopener" clause of the $1 billion 1992 civil settlement between Exxon and the government, a pending $4 billion punitive settlement, and future decisions on developing U.S. oil reserves.