written by: Dr Mike C•edited by: Sarah Malburg•updated: 6/2/2011
We live on an ocean planet where the seas cover almost 2/3 of the surface. Much of the pollution that we produce finds its way into the sea. This article looks at some of the types of ocean pollution which stem from man's activities, but also arise from natural processes.
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The Solution To Pollution
A friend of mine who happens to be a radiochemist once remarked to me that “the solution to pollution is dilution"; he was only being partially serious. Ocean covers two thirds of the surface of the planet and the depth can range from a few meters in the near coastal zone to 10,923 m at the bottom of the Challenger Deep, off the Marianas Islands in the Pacific Ocean. Given that the surface of the Earth covers approximately 510 million square kilometers, it gives an idea of the volume of seawater on the planet (which has been estimated as 1.5 billion cubic kilometers), so my friend’s flippant comment does have some mileage to it.
The world ocean has been described as the ultimate sink for pollution since ultimately, any material which is released into the river system (and many sewage systems around the world) will exit into the sea. This article will consider the types of ocean pollution that may occur and indicate their sources.
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Definition Of Ocean Pollution
Before getting into an identification of the types of pollution that end up in the ocean, we need to understand what is meant by pollution in this context. According to the Organization for Economic Co-operation and Development, marine/ocean pollution "refers to direct or indirect introduction by humans of substances or energy into the marine environment (including estuaries), resulting in harm to living resources, hazards to human health, hindrances to marine activities including fishing, impairment of the quality of sea water and reduction of amenities."
This definition cites the "hazard" as being an important criterion, but also involves a human component. In a sister article, the topic of marine eutrophication was discussed and it is clear that this potentially harmful problem can be a natural occurrence.
From what has gone before, it will come as no surprise that the ocean plays unwilling host to a vast array of types of ocean pollution. The most obvious types of pollution are the ones that make the news such as the recent oil spill disaster in the Gulf of Mexico which caused loss of life and widespread damage to the environment involving hefty clean-up bills. Rig accidents and tanker sinkings may make the news, but rare, minor spillages such as oil tankers purging their tanks, may also harm the local environment. Following the Gulf War, the UNEP set up a program to monitor the marine environment in the region (ROPME) for petroleum hydrocarbon and heavy metal pollution. It involved an active ocean pollution monitoring campaign. This was necessary because of the deliberate pollution of the environment by burning oil fields carried out by Iraq.
Maritime wrecks can pose an ocean pollution hazard because of harmful products used in the vessel (fuel, for instance), but also because of the cargoes that they may be carrying. As the hulks decay, they can also cause severe (local) heavy metal pollution.
Deliberate, illegal dumping in the sea probably represents the most significant pollution hazard since it is unregulated and often times believed that the most dangerous waste pays the best premium. Certain types of dumping do remain legal (for instance, of dredged material) and these are regulated under the London Dumping Convention.
Until 1982, the dumping of certain radioactive waste at specific sites by civilian nuclear authorities was permitted. The world’s military powers have also dumped reactor cores in certain seas and of course, some nuclear powered vessels have been lost in accidents. This practice made sense since dump sites were well away from civilization and fishing activities, sources were supposedly sealed and seawater makes a good shield for any radioactivity that may have seeped out.
Much concern has been expressed about the fate of polythene bags that escape into the marine environment. Apart from the physical hazard that the plastics may cause, the breakdown products of the hydrocarbons that produce them may also be harmful.
This article just scratches the surface of this topic, but for the sake of future generations and the marine ecosystem, the solution to pollution better not be dilution!
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The Challenger Deep - http://www.extremescience.com/zoom/index.php/oceanography/45-deepest-ocean
Volume of the Earth’s Oceans - http://hypertextbook.com/facts/2001/SyedQadri.shtml
Organization for Economic Co-operation and Development - http://stats.oecd.org/glossary/detail.asp?ID=1596
NOLA Gulf of Mexico Oil Spill 2010 - http://www.nola.com/news/gulf-oil-spill/
London Dumping Convention - http://www.londonprotocol.imo.org/
Ocean Disposal of Radioactive Waste - http://www.iaea.org/Publications/Magazines/Bulletin/Bull314/31404684750.pdf
National Geographical; plastics in the ocean - http://news.nationalgeographic.com/news/2009/08/090820-plastic-decomposes-oceans-seas.html