"The untreated coastal areas were fully recovered within five years of the Amoco Cadiz spill," says Hazen. "As for the treated areas, ecological studies show that 30 years later, those areas still have not recovered."
In March of 1989, the oil supertanker Exxon Valdez spilled 11 million gallons of crude oil into the Prince William Sound and impacted some 1,300 miles of coastline. It remains the largest oil spill in U.S. history. A combination of detergents and bioremediation were used in the clean-up. The detergents were nutrient rich, being high in phosphorous and nitrogen compounds. In addition, as part of the bioremediation effort, fertilizers were also used to promote microbial growth. After the first year, the treated areas were dramatically cleaner, Hazen says, but after the second year no improvements were observed. Long-term prospects for the treated area are grim.
"What happened was that we took an oligotrophic (low nutrient) environment, and added lots of nutrients to it to speed up the degradation of the oil, which we probably did," Hazen says. "However, we upset the ecological balance of the system, which could not handle the influx of nutrients. As a result, the severe environmental damage resulting from the spill is expected to persist for decades to come."
While improvements to detergents have been made, including some degree of biodegradability, they remain nutrient rich and in some cases more toxic to the environment than crude oil.
"From a clean-up standpoint, right now we should be using sorbents to take up as much of the oil as possible," Hazen says. "Then we need to gauge how quickly and completely this oil can be degraded without human intervention."
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory