Clean Up and Environmental Impact_Exxon_Valdez

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Clean Up and Environmental Impact_Exxon_Valde

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Clean-Up & Environmental impact
Before the Exxon Valdez oil spill, information available for constructing risk assessment models to predict ecological impacts of petroleum hydrocarbons was limited to selective, largely shortterm monitoring after previous oil spills. After the tanker Exxon Valdez grounded on Bligh Reef in northern Prince William Sound on 24 March 1989, the magnitude of the spill, extent of shoreline contamination, and evident high mortality of wildlife prompted an evaluation of ecological impacts of unprecedented scope and duration extending now for more than 14 years.The release of 42 million liters of Alaskan North Slope crude oil contaminated to some degree at least 1990 km of pristine shoreline. There was use of a dispersant, a surfactant and solvent mixture. A private company applied dispersant on March 24 with a helicopter and dispersant bucket. Because there was not enough wave action to mix the dispersant with the oil in the water, the use of the dispersant was discontinued. One trial explosion was also conducted during the early stages of the spill to burn the oil, in a region of the spill isolated from the rest by another explosion. The test was relatively successful, reducing 113,400 liters of oil to 1,134 liters of removable residue, but because of unfavorable weather no additional burning was attempted. The dispersant Corexit 9580 was considered and tried but was not used for shore clean-up due largely to concerns about toxicity. According to a report by David Kirby for TakePart, the main component of the Corexit formulation used during cleanup, 2-butoxyethanol, was identified as "one of the agents that caused liver, kidney, lung, nervous system, and blood disorders among cleanup crews in Alaska following the 1989 Exxon Valdez spill. Mechanical cleanup was started shortly afterwards using booms and skimmers, but the skimmers were not readily available during the first 24 hours following the spill, and thick oil and kelp tended to clog the equipment. Despite civilian insistence for a complete clean, only 10% of total oil was actually completely cleaned. Exxon was widely criticized for its slow response to cleaning up the disaster and John Devens, the mayor of Valdez, has said his community felt betrayed by Exxon's inadequate response to the crisis. The decision was made to displace the oil with high-pressure hot water. However, this also displaced and destroyed the microbial populations on the shoreline; many of these organisms (e.g. plankton) are the basis of the coastal marine food chain, and others (e.g. certain bacteria and fungi) are capable of facilitating the biodegradation of oil. At the time, both scientific advice and public pressure was to clean everything, but since then, a much greater understanding of natural and facilitated remediation processes has developed, due somewhat in part to the opportunity presented for study by the Exxon Valdez spill.

Despite the extensive cleanup attempts, less than ten percent of the oil was recovered and a study conducted by NOAA determined that as of early 2007 more than 26 thousand U.S. gallons (98 m3) of oil remain in the sandy soil of the contaminated shoreline, declining at a rate of less than 4% per year. Immediate effects included the deaths of 100,000 to as many as 250,000 seabirds, at least 2,800 sea otters, approximately 12 river otters, 300 harbor seals, 247 Bald Eagles, and 22 orcas, and an unknown number of salmon and herring. The researchers found that at only a few parts per billion, polycyclic aromatic hydrocarbons caused a long-term increase in mortality rates. They reported that "species as diverse as sea otters, harlequin ducks and killer whales suffered large, long-term losses and that oiled mussel beds and other tidal shoreline habitats will take an estimated 30 years to recover. The effects of the spill continued to be felt for many years afterwards. As of 2010 there were an estimated 23,000 US gallons (87 m3) of Valdez crude oil still in Alaska's sand and soil, breaking down at a rate estimated at less than 4% per year. Three major pathways of induction of long-term impacts emerge: i) ii) iii) chronic persistence of oil, biological exposures, and population impacts to species closely associated with shallow sediments; delayed population impacts of sublethal doses compromising health, growth, and reproduction; indirect effects of trophic and interaction cascades, all of which transmit impacts well beyond the acute-phase mortality.

After the release of crude oil from the Exxon Valdez into Prince William Sound (PWS), acute mortality followed a pattern largely predictable from other oil spills. Because marine mammals and seabirds require routine contact with the sea surface, these taxa experience high risk from floating oil . Oiling of fur or feathers causes loss of insulating capacity and can lead to death from hypothermia, smothering, drowning, and ingestion of toxic hydrocarbons. Scientists who have monitored the spill area for the last 25 years report that concern remains for one of two pods of local orca whales, with fears that one pod may eventually die out. Federal scientists estimate that between 16,000 and 21,000 gallons of oil remains on beaches in Prince William Sound and up to 450 miles away. Some of the oil does not appear to have biodegraded at all.

There is a huge demand that the US government force ExxonMobil to pay the final $92 million (£57 million) still owed from the court settlement. The major part of the money would be spent to finish cleaning up oiled beaches and attempting to restore the crippled herring population.

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