Download Ecosystems in Distress

Wards: Ecosystems in Distress Oil Spill Clean-up
Introduction
A hydrocarbon is an organic compound consisting only of carbon and hydrogen atoms. Oil, or petroleum,
consists of a number of hydrocarbons, including gas, natural gas, kerosene, lubricating oil, and gas oil.
These crude oil constituents can be separated by a method called fractional distillation. Each of the
hydrocarbons in the mixture has a different boiling point. The mixture is heated, and as the temperature
increases, each fraction changes to a vapor and is collected separately.
Petroleum is used in a variety of liquid hydrocarbon compounds. The chief use of all but the non-volatile
fraction is as fuel. The gas fraction, like natural gas, is mainly used for heating. Gasoline is used for
internal combustion engines that need a fairly volatile fuel, kerosene is used in tractor and jet engines,
gas oil is used in diesel engines, and the lubricating oil fraction is used for engine lubrication. Kerosene
and gas oil (furnace oil) are also used for heating purposes. When these compounds are burned/
combust they release energy in the form of heat, water vapor, and carbon dioxide (2 C8H18 + 25 O2 → 16
CO2 + 18 H2O). Byproducts of the combustion of gasoline includes NOX, particulate matter, CO, and SO2
(sulfur dioxide), many of these byproducts result from naturally occurring impurities found in the
Petroleum and ALL contribute to climate change and impact human health.
Oil Spills
Over the past several years, the people of the world have become increasingly aware of the hazards of
oil spills. A recent study estimated that the amount of oil spilled into the ocean is between five and ten
million tons annually, the major sources include:
1. Cargo tanker washings at sea: Oil tankers use seawater as ballast to stabilize the craft after they have
discharged their oil. This contaminated water is then discharged back into the ocean when the tanker is
refilled.
2. Waste oil dumping at sea: This type of dumping by ships other than tankers contributes an estimated
500,000 tons annually,
3. In-port oil losses: Such losses are attributed to collisions in port and to the procedures used during
loading and unloading of oil. In-port oil losses contribute over one million tons to sea pollution.
4. Tanker accidents: Such accidents on the high seas or near shore have recently added to the problem
and have received great amounts of publicity, Tanker disasters are potentially becoming larger all the
time. The largest supertankers now built are as long as the Empire State Building (300 meters). On of the
largest spills in this category took place on March 24, 1989, when the supertanker Exxon Valdez,
carrying 1.2 million barrels of crude oil, collided with a reef off the coast of Alaska. Other costly oil spills
include spills in Hawaii, Galveston Bay and Santa Barbara.
5. Exploration losses: Such oil spills occur during exploration for and production of oil due to the blowout
of wells and accidental damage to offshore drilling rigs. Oil leakage has also occurred from the 200,000
miles of pipeline that cross waterways and reservoirs due to cracks, punctures, or corrosion. The largest
spill of this category occurred in April of 2010 when the Deepwater Horizon oil rig exploded and
discharged over 260 million gallons into the Gulf of Mexico.
6. Motor oil: Oil droplets found on the surface of our roads and parking lots runoff into our local
waterways and into the oceans after every rain event. It is estimated that EVERY MONTH the amount of
oil droplets that enter the oceans from these surfaces equals the amount of oil spilled by Exxon Valdez.
The Fate of Spilled oil
According to a well-known axiom that oil and water don't mix, it might be expected that spilled oil would
float around until it was washed ashore. However, this is not the case. A single gallon of oil can spread
enough to cover up to four acres of water. As soon as the oil is spilled in a marine environment, many
changes begin to take place. The volatile components of oils that have boiling points below 200°C begin
to evaporate. Within days, 25% of the spilled oil is lost through evaporation. The remaining oil undergoes
an emulsification process that leads to a formation of a highly viscous material, which, when heavy
enough, sinks to the bottom of the ocean. This highly viscous material adheres to almost all objects that
it encounters, including birds and marine mammals. Oil that survives the emulsification process is
degraded by microorganisms and photo-oxidation (breakdown under the influence of radiant energy). By
the time three months have passed, only 15% of the original oil volume remains. This is in the form of
dense, black, tarry lumps that end up on the shores.
Short-Term Effects of Oil Spills
Short-term effects receive the most publicity because they are immediately obvious.
1. Reduction of light transmission: Studies have shown that light intensity two meters below an oil slick
can be reduced by 90%. Such a reduction in light intensity, in turn, hampers marine plants and protist
growth by reducing the rate of photosynthesis.
2. Reduction in dissolved oxygen: Oil film hinders the rate of oxygen uptake by water. Studies have
shown a lower dissolved oxygen level in oil-polluted water than in clear water.
3. Damage to marine birds: Swimming and diving birds covered with oil can drown or become
handicapped. Oil causes the bird feathers to mat together, which reduces the bird's ability to fly and float
on water. In addition, feathers lose their insulating ability due to the breakdown of natural insulating oils
and waxes found on feathers. Eventually, oil-soaked birds will die as a result of exposure in cold water or
their inability to obtain food.
4. Toxic effects to marine environment: Crude oil is a complex mixture, made up of various compounds
that differ in molecular weight and structure. Certain crude oil fractions are toxic to marine life and man.
Such compounds include: benzene, toluene, xylene all of which are known carcinogens (cause cancer).
Within days of an oil spill, a massive destruction of aquatic life can occur. The species affected include a
wide range of fish, shellfish, worms, Crabs, microcrustaceans and other invertebrates.
Long-Term Effects of Oil Spills
Long-term effects are not as apparent as the short-term effects because they require more extensive
research. Recent studies have identified many areas of concern regarding long-range effects. Chemical
messengers in seawater mediate many important biological processes that are important to the survival
of the organism. For example, many marine organisms depend on chemical messengers for processes
such as finding food, escaping from predators, locating habitats, and attracting a mate. The oil
compounds interfere with such processes by blocking the taste receptors of organisms or by mimicking
the natural stimuli, both causing disastrous effects on the survival of some marine organisms. Certain
crude oil fractions are chemically stable, and once incorporated into a particular organism, they can pass
through the food chain and even reach marine organisms that are harvested for human consumption
(similar to mercury and DDT). Recent reports have identified that the oil can serve as a concentration
medium for poisons such as pesticides that can reach marine organisms and humans in higher
concentrations than would normally be found.
Methods of oil Spill Clean-Up
Since the principal cause of an oil spill is human error, efforts should be directed towards prevention.
However, Some accidents will still take place in spite of any prevention method. So, what do we do with
an oil spill?
Mechanical methods
Presently, mechanical methods to clean up oil spills include the following:
1. Booms or barriers contain the oil slick (figure 1). This makes it easier to skim the oil off the surface.
2. Skimmers are used to remove oil from the surface of the water (figure 2). They are attached to ships
on open waters or they may be hand-held along a shoreline. They skim the oil and a thin layer of water
from the surface. If skimming on open waters, the oil and water are separated into storage tanks within
the ship, and the water is dumped back into the ocean. The oil collected must be disposed of or
reclaimed. Skimming barges are useful on calm waters only.
3. Sorbents are materials that have been used to soak up and contain oil spills. Some of these include
straw, powdery clay, sawdust, chopped corn cobs stuffed in cloth "sausages", human hair, and other
organic and inorganic adsorbents such as pine bark and polyurethane.
4. Chemical dispersants, detergents and solvents are used to degrade (breakdown) the oil.
Unfortunately, most of these chemicals are toxic to benthic (bottom dwelling) organisms, littoral (shoredwelling) organisms, and open marine life.
5. Flame can be used to burn the oil. However, it does not undergo complete combustion and the
unburned black smoke contains toxic compounds.
Case Study: The Exxon Valdez
In the spring of 1989, one of the largest oil spills in U.S. history occurred when an oil tanker named the
Exxon Valdez hit a reef in Prince William Sound off the coast of Alaska. More than ten million gallons of
crude oil spilled into the sound. The resulting oil slick covered more than 1,000 miles of the Alaskan
coastline and caused an estimated five billion dollars in environmental damages.
The deadly effects of the crude oil spill on plants and animals were immediate and harsh. Even today,
more than ten years later, the Alaskan ecosystem still suffers. The Exxon Valdez disaster killed more
wildlife than any other environmental disaster in our nation's history. The official death toll estimates that
250,000 seabirds, 2,800 sea otters, 300 harbor seals, 250 bald eagles, and as many as 22 killer whales
were killed by the spill.
In particular, the Exxon Valdez oil spill affected Seabirds in a number of ways and unless these birds
were quickly found and cleansed of oil by rescue workers, they died.