Oil spill! A marine calamity raises the burning question: how to prevent a repeat disaster? (Oil/Oceans).
PETROLEUM or crude oil, is a viscous mix of liquid hydrocarbons, compounds made of the elements hydrogen and carbon. Crude oil forms underground as plant and animal remains decay over time. Petroleum refineries separate crude oil into products such as fuel oil, asphalt, and gasoline.
On November 13, 45 kilometers (28 miles) off the Galician coast in northwest Spain, a mysterious gash suddenly ruptured the tanker's hull. As seawater flooded the ship and oil started to ooze, its crew radioed a frantic SOS (see diagram, p. 8). Alarmed by a looming environmental disaster--the coastal waters are a mother lode for local fishermen, the rugged shore a wildlife haven--the Spanish government ordered Prestige to halt. Rescue tugs sped to the leaking ship and towed it 322 km (200 mi) out into the open sea.
Choppers airlifted all 27 crew members to safety, but the disaster was far from over. Six days later, Prestige split in two and sank 3,500 meters (1.5 mi) to the bottom of the Atlantic. Before descending, the tanker shed over half its load, say environmental scientists. The rest--some 37,500 tons--sank to the seabed with Prestige. "It's one of the worst spills ever," says Simon Cripps of the Worldwide Fund for Nature. Though its tool is still far out-stripped by the largest recorded tanker spill: 279,000 tons of oil dumped off the West Indies in 1979.
The Prestige cleanup effort began immediately. Veterinarians and volunteers rescued oil-smothered birds, while thousands of soldiers and fishermen shoveled gummy oil off thousands of kilometers of coastline. As the big mop-up continues, questions linger: Will the Galician coastal ecosystem ever recover? What happens to oil trapped in the sunken tanker? And how can scientists and governments prevent such future disasters? Read on.
Q: What kind of oil did Prestige spill?
A: The tanker carried dense, gooey oil used to fuel large ships. "It's the kind that floats real low in the water, like blobs in a lava lamp," says David Kennedy, a director of the National Oceanographic and Atmospheric Agency's (NOAA) Office of Response and Restoration. Oil this heavy doesn't readily evaporate or break into droplets--making for a killer cleanup.
Q: What happens when oil oozes into the sea?
A: Actually, natural oil seeps on the ocean floor constantly bubble up petroleum. "Oil is a natural product," says NOAA marine biologist Gary Shigenaka. "You can have a diverse, healthy ecosystem around it." But an enormous oil spill can overwhelm and maim an ecosystem.
All oil spills eventually clear up over time. "The name for this process is weathering," explains NOAA marine biologist Rebecca Hoff. Wind. waves, and sunlight decompose an oil slick into droplets; then microscopic organisms in the sea feed on the droplets. Light petroleum products like kerosene or gasoline evaporate quickly, disappearing in a matter of days. But unless experts physically remove Prestige's tarlike fuel oil from the water. it will wash ashore and possibly devastate the coastline.
Q: Is there a quick fix to get oil out of seawater?
A: One tactic is to spray a slick with chemical dispersants that split oil into tiny particles so natural weathering can begin. But that method wouldn't work in this case. Says Hoff: "Very heavy oils are hard to disperse."
Other strategies: Sometimes experts lasso a spill with nets called booms. and skimmer boats suck up the oil. Or they can set floating oil afire. "Burning the oil removes a lot of it from the surface," Hoff says. The resulting smoke is similar to that of a forest fire. But the Prestige oil sank 10 to 15 feet below the surface--out of reach of booms, skimmers, or fire.
Q: What happens to oil that reaches the coast?
A: "When oil washes up on beaches, people just shovel it up," Hoff explains. "It's not a high-tech thing." In this case, the affected coast is a mix of rocky shorelines and nearly 600 sandy beaches. "We went to places where the oil was a meter thick," Shigenaka says. After people have mopped up the "black tide," nature will weather remaining oil on the surface.
Q: How has the oil spill impacted the region?
A: It's hard for scientists to predict the extent of the ecological damage. But they're looking at the aftermath of the worst oil spill in U.S. waters for clues: Oil patches left over from the 1989 Exxon Valdez disaster still release toxins that harm Alaskan sea life--from fish and birds to land mammals. "It's going to take a long time for the oil to be gone and for the effects to go away," says Brenda Ballachey of the U.S. Geological Survey's Alaska Science Center.
Oil from Prestige has already killed 200,000 seabirds of 71 species, says the British Trust for Ornithology. As for fishing--Galicia's economic backbone--"a lot of fisheries shut down," says Shigenaka. And the wrecked tanker oozing oil at the ocean bottom threatens the entire marine food chain, as oil particles pass from tiny microbes called zooplankton to the small fish that eat them, and so on; even tiny amounts of crude oil can damage fish eggs and embryos, according to a National Marine Fisheries Services study.
Q: Will the oil sit in Prestige forever?
A: At first, that was the idea. "There was hope the cold temperature in the ocean depths would solidify the oil," Shigenaka says. Instead, the oil has thickened into a gel that steadily seeps into the water. As a temporary fix, a French mini-submarine patched 17 of 20 holes in the tanker. "But ultimately the hull will rust through," says Shigenaka.
That's why scientists are urging the Spanish government to use underwater robots to pump remaining oil out of the ship's tanks. Although the remedy could prove daunting in 3.5-km-deep water, research teams are exploring strategies.
Q: How can we prevent future spills?
A: For starters, oil tankers need to be upgraded. Old tankers like Prestige contain one layer of metal separating the cargo from the ocean. The new "millennium class" oil tanker has a double hull, offering greater protection against spills (see diagram, p.8). U.S. and European Union laws now require all new tankers to feature double hulls.
But as experts point out, even the best crew in the safest ship can run into trouble. "This is not the first tanker disaster and it will not be the last," says Klaus Toepfer, executive director of the United Nations Environment Program. To meet the planet's 3-billion-gallon-per-day oil habit, fuel is shipped, piped, and trucked around the globe. Are there energy alternatives? Turn the page to find out.
THE PRESTIGE OIL TANKER DISASTER
The 26-year-old oil tanker split in two and sank off the coast of northwestern Spain last November, sparking what environmental scientists call Europe's biggest ecological disaster ever. Here, a close look at the oil spill:
Single-hulled tankers like Prestige are being phased out. By 2010, all tankers in U.S. waters must feature double hulls.
One layer of steel separates oil tanks from the ocean. Oil will spill if the hull cracks.
New "millenium class" tankers have two layers of steel spaced 10 ft apart.
HOW THE TANKER SANK
1 A strong storm rips a hole in the hull.
2 Violent waves quickly flood some empty fuel tanks.
3 The weight difference between the center and the ends of the hull eventually snap Prestige in two.
THE FATE OF SPILLED OIL
As oil spreads over the sea surface, natural processes start to break it down. Below, eight physical and chemical changes that help the ocean clean itself of oil:
Evaporation Light substances in the oil vaporize off the surface.
Emulsification Wave action mixes oil and water into a mousse-like substance, which people can scoop up.
Dissolution A tiny percentage of oil compounds dissolve in seawater.
Sinking Gravity can pull heavy oil down to the seafloor.
Oxidation Oxygen molecules combine with oil, allowing it to slowly dissolve in water.
Biodegradation Microbes in water feed on compounds in oil, breaking it down into water-soluble compounds.
Dispersion Waves break up oil and spread it into the water, encouraging biodegration an dissolution.
Ingestion by organisms After microbes begin degrading oil, small worms join in. As fish eat the worms, oil enters the marine food chain.
Did You Know?
* Scientists call the emulsion formed by oil and water "chocolate mousse," due to its color and texture.
* On the Galicia Bank more than 86 species of fish--including anchovies, sardines, and monkfish--are threatened by the Prestige tanker spill. Galicia's mussel and clam beds are Spain's largest.
* The Spanish government' estimates the Prestige disaster cleanup will cost $1 billion over the next year.
Math: Prestige was carrying 77,000 tons of oil. About how many barrels is that? How many liters? Use these figures to help you:
1 barrel = 160 liters
1 ton = 7 to 9 barrels (depending on the oil weight)
Critical Thinking: In response to the Prestige disaster, the European Union plans to introduce tougher penalties for marine polluters--upping the severity from monetary fines to criminal sanctions. When a tanker spills oil, who should be held responsible and how should they be penalized?
"Oil Tanker Splits Apart Off Spain, Threatening Coast," by Emma Daly and Andrew C. Revkin, The New York Times, November 20, 2002
NOAA's Office of Response and Restoration has a comprehensive Web site for kids: www.response.restoration.noaa.gov/kids/kids.html
For a broad range of activities and strategies, check out the videotapes and workbook module, titled Oil Spill by Russell G. Wright, Dale Seymour Publications, 1995. To order call 1-800-872-1100.
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|Author:||Masibay, Kim Y.|
|Date:||Apr 18, 2003|
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