Cleaning Up After The Exxon Valdez Was

A Mistake Essay, Research Paper

Cleaning Up after the Exxon Valdez Was A Mistake

Through many hours of research I have determined that the spill cleaning techniques used to clean the Prince William Sound area of Alaska did more harm than leaving the oil where it was. The Alaskan oil spill has become the most studied and managed event of its kind. Although there is not much that can be done about the marine life that came into direct contact with the crude oil, the geologic effects that the oil introduced into the area should have been left to nature to repair. To understand the effects of the oil to the area, it is best that you know a little bit about the oil itself.

There are many types of crude oil, but in general they contain hundreds, even thousands of different compounds. Some are straight-chain hydrocarbons with carbon numbers ranging from 4 or 5 to 35 or more. Other hydrocarbons have branched chains with a wide range of carbon numbers. Aromatic compounds such as benzene, toluene, and polynuclear hydrocarbons are substantially present. Other constituents include waxes and complex, high molecular weight asphaltenes. (Abelson) All of these substances and more are present in Prudhoe Bay crude oil. When ingested, most of the compounds are nontoxic. Notable exceptions are some of the aromatic compounds, including benzene and toluene.

After a crude oil is spilled in a marine environment, many processes follow.

Typical crude has a density of about 0.85, more or less, and this factor combined with winds, wave action, and currents leads to spreading, which is very rapid during the first 24 hours. During that period most of the components having boiling points below 200[deg.]C volatilize. As a result some of the toxic chemicals such as benzene are removed. (The composition of the floating mixture is further changed immediately and later by photooxidation, biodegradation, dispersion, and dissolution. About a day after the spill, depending on temperature and wave action, an emulsification of oil and sea water occurs, leading to formation of a highly viscous material that contains about 70% water. This material is very sticky, and it adheres to almost all objects that it encounters, including birds and sea otters. Abelson) There has been one report of a minor fish kill in Prince William Sound. Observations at other oil spills indicate that dispersed oil is not toxic to zooplankton when ingested. It is eliminated in the feces. In general, oil chemicals are not concentrated in the food chain.

There are many ways that nature fights oil in the environment, when it gets put where its not suppose to be. After all crude oil is a natural part of our environment. In one study designed to simulate the effects of waves and tides, contact with seawater gave the black, sticky oil “the fluffy appearance of a flocculated emulsion” that no longer strongly adheres well to sediment, Bragg reports. Seawater made up about 80 percent of these cloud-like aggregates. The rest consisted largely of mineral grains stably bound to oil droplets 1 to 10 microns in diameter. (Beached)

For instance, the Exxon scientists found that flocculation can increase the area of the oil-water interface — sometimes by up to 1,000 times. This increases the likelihood that the more toxic, water-soluble aromatic chemicals will leach from the oil, Bragg says. Moreover, it expands the area available for hydrocarbonhungry bacteria to latch on to, thereby facilitating the oil’s breakdown. Indeed, water taken from oiled beach sediment revealed that active bacteria usually make up part of any naturally produced oil-clay floc.

Flocculation also helps explain another formerly puzzling observation: the relatively rapid disappearance of oil from even quiet, sheltered bays. Most researchers expected oil to persist in these areas, where abrading waves and sediment movement seldom occur, even during storms. But experiments by Bragg and his co-workers showed that waves too weak to move sediment sands could still drive the flocculation-fostered removal of oil, initially at rates of 3 percent per hour. Bragg says it now appears that every ebb tide may remove some oil – even after heavy weathering has rendered oil tarry and very insoluble in water.

The unusually high levels of “mineral fines” — clay “flours” produced by

local glaciers — along the southern Alaskan shoreline contributed to the unusually efficient emulsification of beached Valdez oil, the Exxon studies indicate. (Beached) They also suggest that adding such flours to shores with low clay contents might augment the natural cleanup of oil spills in the future.

The Alaska Current enters the Sound on the east and exits on the west. This flow has protected some of the Sound from major contamination and has carried part of the spill out of the Sound. As a result of various physical, biological, and chemical processes, the inventory of oil in Prince William Sound (originally 10 million gallons) dropped about 70% during the first 4 weeks after the spill. The U.S. Forest Service, one agency active at the site, quotes an Exxon estimate as follows: evaporated, 35%; recovered, 17%; burned, 8%; biodegraded, 5%; dispersed, 5%. The total in the form of oil slicks on Prince William Sound amounted to 10% of the original spill; that on the shoreline, 18%. A large fleet of vessels was mopping up the slicks, a