Sources of pollutants
There is no strong scientific data concerning the origins of pelagic plastics. The figure that an estimated 80% of the garbage comes from land-based sources and 20% from ships, is derived from an unsubstantiated estimate.[15]However, ship-generated pollution is a source of concern since a typical 3,000 passenger cruise ship produces over eight tons of solid waste weekly, a minor amount of which ends up in the patch, as most of the waste is organic.[16] Pollutants range in size from abandoned fishing nets to micro-pellets used in abrasive cleaners.[17] Currents carry debris from the west coast of North America to the gyre in about six years [1], and debris from the east coast of Asia in a year or less.[18][19] An international research project led by Dr. Hideshige Takada of Tokyo University studying plastic pellets, or nurdles, from beaches around the world may provide further clues about the origins of pelagic plastic.[20]
[edit] Plastic photodegradation in the ocean
Main article: Photodegradation
The Great Pacific Garbage Patch has one of the highest levels known of plastic particulate suspended in the upper water column. As a result, it is one of several oceanic regions where researchers have studied the effects and impact of plastic photodegradation in the neustonic layer of water.[21] Unlike debris, which biodegrades, the photodegraded plastic disintegrates into ever smaller pieces while remaining a polymer. This process continues down to the molecular level.[22]
As the plastic flotsam photodegrades into smaller and smaller pieces, it concentrates in the upper water column. As it disintegrates, the plastic ultimately becomes small enough to be ingested by aquatic organisms which reside near the ocean's surface. Plastic waste thus enters the food chain through its concentration in the neuston.
Some plastics decompose within a year of entering the water, leaching potentially toxic chemicals such as bisphenol A, PCBs and derivatives of polystyrene.[23]
There is no strong scientific data concerning the origins of pelagic plastics. The figure that an estimated 80% of the garbage comes from land-based sources and 20% from ships, is derived from an unsubstantiated estimate.[15]However, ship-generated pollution is a source of concern since a typical 3,000 passenger cruise ship produces over eight tons of solid waste weekly, a minor amount of which ends up in the patch, as most of the waste is organic.[16] Pollutants range in size from abandoned fishing nets to micro-pellets used in abrasive cleaners.[17] Currents carry debris from the west coast of North America to the gyre in about six years [1], and debris from the east coast of Asia in a year or less.[18][19] An international research project led by Dr. Hideshige Takada of Tokyo University studying plastic pellets, or nurdles, from beaches around the world may provide further clues about the origins of pelagic plastic.[20]
[edit] Plastic photodegradation in the ocean
Main article: Photodegradation
The Great Pacific Garbage Patch has one of the highest levels known of plastic particulate suspended in the upper water column. As a result, it is one of several oceanic regions where researchers have studied the effects and impact of plastic photodegradation in the neustonic layer of water.[21] Unlike debris, which biodegrades, the photodegraded plastic disintegrates into ever smaller pieces while remaining a polymer. This process continues down to the molecular level.[22]
As the plastic flotsam photodegrades into smaller and smaller pieces, it concentrates in the upper water column. As it disintegrates, the plastic ultimately becomes small enough to be ingested by aquatic organisms which reside near the ocean's surface. Plastic waste thus enters the food chain through its concentration in the neuston.
Some plastics decompose within a year of entering the water, leaching potentially toxic chemicals such as bisphenol A, PCBs and derivatives of polystyrene.[23]