Crude petroleum or mineral oil is the term usually applied to the complex mixture of gases, liquids and associated solids which occur deep inside earth’s crust. The composition of crude petroleum varies from locality to locality from where they are drawn out. However, all of them contain hydrocarbons both aliphatic as well as aromatic, cycloparaffins naphthenes etc.
In addition to these, crude petroleum also contains a number of compounds of sulphur, nitrogen and a number of metalic constituents like nickel, chromium, cadmium, vanadium iron etc. Crudes found in eastern and mid- western sections of the United States of America are reported to be predominantly parafftnic while those found along the Gulf coast are mostly naphthenic.
Crude petroleum is distilled to separate various useful components which include light oils such as petrol and benzene, medium oils such as kerosene and diesel, heavy oils such as lubricating oils, greases, Vaseline, hard wax and coal taretc.
Oil Spills:
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Petroleum crude is a precious substance and its distillates drive millions of vehicles around the world, light countless number of homes and provide energy for domestic, industrial and agricultural use. As its distribution is limited to certain places and rock formations, huge amountsof crude pertroleum has to be transported across the sea and land from one place to another and so are its finished products.
In the process some of this precious material spills out. In marine environment these oil spills cause enormous damages. Each litre of spilled oil may spread to cover an area of about 4000 sq. meters over the water surface while its oxidation requires about 3.3 kg of oxygen which usually occurs in four hundred thousand litres of sea water.
Oil spills have been occurring ever since large scales transportation of crude petroleum and its distillates started. However, probably the first oil spill with disastrous consequences which drew enormous public attention occured on March 18, 1967 when a Liberian tanker, Terry Canyon, ran aground near the entrance of English Channel spilling about 60,000 tons of crude petroleum into the sea. In January 1969, an off-shore oil well blew off near the coast of Santa Barbara in the United States and discharged about 4500 litres of petroleum crude per hour causing extensive damage to littoral and sub-littoral life.
In 1978, the much publicized Amoco Cadiz disaster dumped about 6! Million gallons of crude oil along the French coast. The Alaskan oil spill from the 30,000 ton-supertanker, Exxon Valdez occurred on March 24, 1989 when the tanker plied up on a reef, causing the release of about 11 million gallons of crude petroleum into the clean waters of Prince Williums Sound.
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As the oil hit 2000 kms of the shore line about a hundred thousand birds, which included some rare species as well, were killed. A countless number of sea animals died and a couple of bears and deer’s which lived on sea animals and plants were found dead. The largest oil slick which made history occurred in 1990 during the Gulf war in which Kuwait’s oil installations dotted along the shore were blown up.
About 330 million gallons of petroleum crude was discharged into the water of the gulf which spread over an area of about 700-800 sq.kms. A countless number of sea animals were affected and an ecological catastrophe followed.
Apart from these major oil spills, minor leakages of crude oil keep occurring all along important trade routes in sea through which oil is transported. Some smaller incidences of oil spill have occurred along Indian coast as well. About 3000 tons of oil was washed on to the Gujarat coast when in July 1973 the oil tanker Cosmos Pioneer was grounded. In 1974, Transhuron, an American tanker sprang a leak near Laccadives and discharged about 5000 tons of special furnace oil causing extensive damages.
In June 1989, a Maltese tanker jammed into a British vassel and spilled over 5,000 tons of furnace oil in the open sea near Bombay. While other type of pollution is being minimized, the frequent presence of oily waters and floating tar balls along important trade routes and ports testily to the fact that oil pollution is slowly rising all around the world.
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Natural Oil Seeps:
Man made oil spills are not the only source of crude petroleum and associated substances in the sea. Natural seeps developed in submarine rock strata have been discharging crude petroleum into the environment since millions of years. More than 200 submarine oil seeps have been identified around the world and the amount of crude discharged annually by them is far greater than the total contamination from off-shore oil production and transportation activities.
Most of these oil seeps Pollution of Earth’s Surface occur deep inside the ocean where the slow discharge of petroleum crude is taken care of by natural agencies of degradation. Man-made oil spills, however, tend to be disastrous because they introduce suddenly enormously quantities of crude petroleum on ocean surface which causes problems of toxicity to the organisms exposed to it and an ecological catastrophe.