Sea pollution

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Temps de lecture : 5 minutes  

rejet mine d'or philippines pollution des océans
Between 75 and 80% of marine pollution is caused by land, particularly agriculture. 30% of this is from the atmosphere. Around 12% of the pollution is caused by maritime transport. In South America, 98% of domestic wastewater ends up, untreated, in the sea. The countries along the Mediterranean Sea throw 50 million tons of waste into it every year and the Chinese throw 60 million tons of waste into the Yellow sea daily. Over half of the hydrocarbon discharge comes from continents, 5% comes from oil tanker accidents, 20% comes from waste and other ship-related accidents, 4% from sea exploitation and 11 to 15% is due to natural causes. Accidental pollution through hydrocarbon is significantly decreasing and only represents a small percentage of waste through degassing estimated at between 1.5 and 3 million tons of oil a year. In 2003, according to the WWF, between 0.7 and 1.3 million tons of oil were spread by degassing in the Mediterranean. According to the Ifremer (the French Institute for Exploitation of the Sea), coastal water pollution cost the world economy almost 12.8 billion dollars in 2006.

Marine pollution is the result of products being thrown into seas and oceans, mostly by mankind: domestic waste (sewage and rubbish, pollutants in runoff water…), industrial waste (hydrocarbons, metals, synthetic chemical and organic substances, radionuclides…) and agricultural waste (fertilisers, pesticides…). This includes water pollution and marine sediments, and more generally all damage to marine ecosystems caused by harmful substances being discharged into the sea, either by their nature or their quantity.

Fragile coastal areas

Most of the pollution comes from continents and is carried by rivers and winds. It is concentrated in coastal waters which provide water for 99% of total fish production. In fact, only a small amount of industrial pollution on the high seas is the result of accidents or malice: shipwrecks, deballasting, degassing and oil spills which are spectacular and disastrous when they reach the coast. Plastic bags make up about 60% of the visible mass of waste polluting the sea and cause the death of a million birds, 100.000 marine mammals and an innumerable number of fish.

All coasts are more or less affected by pollution. The European coasts from the north to the south, the Atlantic coasts of the North-American continent and the Caribbean, the Pacific coasts from Mexico to Panama and Los Angeles to Vancouver, the seas of China from the north to the south of Japan, of Java, the oriental coasts of the Indian continent, the South-African coast between the Cape and Maputo as well as the banks of the Black sea and the Caspian sea are the most affected.

Situation of seas surrounded by land

– Mediterranean Sea: 30% of the world maritime trade and 20 to 25% of international oil transport, 156 accidents followed by hydrocarbon discharges between 1977 and 2000, three significant oil spills: Irenes Serenade in Greece and Captain Marcos in Algeria in 1980 and Haven in Italy in 1991; thousands of tons of toxic waste poured directly into the sea by the industry, 60 % of urban wastewater poured into the sea without any prior treatment.

– Baltic Sea: benthic fauna practically decimated on half of the central Baltic’s seabed (100.000 km2); this is due to land-based pollution (56% nitrogenous content, the remaining 44% coming from the atmosphere); 98% of pollution by hydrocarbons from oil from the continent.

— Caspian Sea: 140 million tons of pollutants poured into the sea every year, 65% from heavy industry wastewater, 44 mg of pesticides per litre (on average) in the northern part, especially that of the Volga delta, compared to the 7mg/l of the Sea of Azov deemed an environmental disaster zone by the Ministry of natural resources of the Russian Federation.

– Black Sea, polluted by the Dniestr, the Dniepr, the Danube and the Don, in a very critical state: eutrophication, important and increasing animal mortality rate over the last three decades , 80% drop in fishing yields, only 6 species of fish that can still be fished out of the 26 which could previously be commonly marketed in this basin.

Effects on the marine environment

Pollution can be physical, chemical or biological. Pollutants can be natural substances (organic and mineral matter), synthetic degradable or non-degradable substances (plastics, pesticides). They can be toxic or not with varying endurance.

Their consequences are much more serious close to coasts than out at sea.

Living resources are destroyed or become unfit for consumption. The deterioration of water quality can lead to intoxications and illnesses and have an impact on the economy by preventing fishing, leisure activities or water being used for industrial purposes. The disappearance of sensitive species and the proliferation of more adapted species threaten ecosystems. Pesticide pollution in South Carolina caused half the disappearance of fish. The 10 billion tons of ballast water poured into the sea every year from one end of the globe to the other introduce species which colonise the environment at the expense of indigenous species. Toxic substances are stored in the fatty tissue of fish, marine mammals and piscivorous birds.

In humans, polychlorinated biphenyl plays a part in causing breast cancer, lung cancer, liver cancer and colon cancer. It can cause delays in neurological development and growth. Persistent organic pollutants are concentrated in shells and other filters and they can cause typhoid, hepatitis and other illnesses if they are ingested.

Here are some of the most recent oil spills

2007: Hebei Spirit oil tanker, 10.500 tons of crude oil dumped, 300 km of coast affected, South Korea

2006: Israelis bomb the tanks of the Jiyyeh power plant, Lebanon, 15.000 t

2003: Tasman Spirit oil tanker, over 12.000 t, Pakistan

2002: Prestige oil tanker, 64.000 t of heavy fuel oil, 2.600 km of coast affected, Galicia (Spain)

2001: P-36 oil rig, 350.000 t, Bacia de Campos, Brazil

1999: Erika oil tanker, 20.000 t of heavy fuel oil, 400 km of coast affected, Brittany (France)

1996: Sea Empress oil tanker, 73.000 t, Wales

1993: Braer oil tanker, 84.500 t, Shetland Islands

1992: Aegean Sea oil tanker, 67.000 t, Galicia (Spain)

1991: Haven oil tanker, 144.000 t, Genoa (Italy)

1991: ABT Summer oil tanker, 260.000 t, Angola

1991: Gulf War, 800.000 t, Kuwait

1989: Exxon-Valdez oil tanker, 38.500 t of crude oil, 800 km of coasts affected in Alaska (United States)

1983: Castillo de Belver oil tanker, 250.000 t, South Africa

1983: Nowruz offshore well (Iran), 250.000 t

1980: Irenes Serenade oil tanker, 103.000 t, Greece

1979: Atlantic Empress oil tanker, 276.000 t, Caribbean

1979: Ixtoc drilling platform, Gulf of Mexico, between 500.000 and 1.500.000 t

1978: Amoco-Cadiz oil tanker, 227.000 t of crude oil, 360 km of coast affected, Brittany (France)

1976: Urquiala oil tanker, 101.000 t, Galicia (Spain)

1972: Sea Star oil tanker, 115.000 t, Gulf of Oman

1967: Torrey-Canyonn oil tanker, 121.000 t of crude oil, 180 km of coast affected, Wales

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