keane
Joined: 09 Jul 2007
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 Posted: Tue Nov 27, 2007 2:47 am Post subject: Plastics: forever and ever, amen. |
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Nobody Home: Earth Without Man Would Recover
Even from plastics... but not in any meaningful time scale for humans or any other animal life... An excerpt from a book about how the Earth would change without us. Fascinating... The book site is here. Watch the vids. Cool.
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Capt. Charles Moore of Long Beach, California, ...steered his aluminum-hulled catamaran into a part of the western Pacific he'd always avoided. Sometimes known as the horse latitudes, it is a Texas-sized span of ocean between Hawaii and California rarely plied by sailors because of a perennial, slowly rotating high-pressure vortex of hot equatorial air that inhales wind and never gives it back...
Its correct name is the North Pacific Subtropical Gyre, though Moore soon learned that oceanographers had another label for it: the Great Pacific Garbage Patch... Moore and his crew found themselves crossing a sea the size of a small continent, covered with floating refuse. ...what was bobbing around them was a fright of cups, bottle caps, tangles of fish netting and monofilament line, bits of polystyrene packaging, six-pack rings, spent balloons, filmy scraps of sandwich wrap, and limp plastic bags that defied counting.
..."This," Captain Moore tells his passengers, "is where all the things end up that flow down rivers to the sea."...
During his first 1,000-mile crossing of the gyre, Moore calculated half a pound for every 100 square meters of debris on the surface, and arrived at three million tons of plastic. His estimate, it turned out, was corroborated by U.S. Navy calculations. It was the first of many staggering figures he would encounter. And it only represented visible plastic: an indeterminate amount of larger fragments get fouled by enough algae and barnacles to sink. In 1998, Moore returned with a trawling device, such as Sir Alistair Hardy had employed to sample krill, and found, incredibly, more plastic by weight than plankton on the ocean's surface.
In fact, it wasn't even close: six times as much.
When he sampled near the mouths of Los Angeles creeks that emptied into the Pacific, the numbers rose by a factor of 100, and kept rising every year.
...One study directly correlated ingested plastics with PCBs in the fat tissue of puffins... plastic pellets that the birds ate concentrate poisons to levels as high as one million times their normal occurrence in seawater.
By 2005, Moore was referring to the gyrating Pacific dump as 10 million square miles � nearly the size of Africa.
..."Plastic is still plastic. The material still remains a polymer. Polyethylene is not biodegraded in any practical time scale. There is no mechanism in the marine environment to biodegrade that long a molecule." Even if photodegradable nets helped marine mammals live, he concluded, their powdery residue remains in the sea, where the filter feeders will find it.
"Except for a small amount that's been incinerated," says Tony Andrady the oracle, "every bit of plastic manufactured in the world for the last 50 years or so still remains. It's somewhere in the environment."
That half-century's total production now surpasses one billion tons. It includes hundreds of different plastics, with untold permutations involving added plasticizers, opacifiers, colors, fillers, strengtheners, and light stabilizers. The longevity of each can vary enormously. Thus far, none has disappeared. Researchers have attempted to find out how long it will take polyethylene to biodegrade by incubating a sample in a live bacteria culture. A year later, less than one percent was gone.
"And that's under the best controlled laboratory conditions. That's not what you will find in real life," says Tony Andrady. "Plastics haven't been around long enough for microbes to develop the enzymes to handle it, so they can only biodegrade the very-low-molecular-weight part of the plastic" � meaning, the smallest, already-broken polymer chains... |
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