Thursday, November 20, 2008

The Great Pacific Garbage Patch

Plastics, besting ancient Gaul, are divided into far more than three parts. There are the acrylics, the polyesters, the silicones, the polyurethanes, and the halogenated plastics to name a few of the major categories. Plastics are made into cups, bags, fabrics, cords, paints, and an infinitude of little parts for computers, tools, factory machines, and other wonders of the modern world. There are millions of tons of various plastics made each year but also--and here, as the Bard says, is the rub--millions of tons are discarded each year. Some 95% of all plastics that are manufactured wind up in garbage dumps where some of them take as long as decades, even centuries, to decompose.

There are some few plastics that are designed to be "biodegradable" which means they can be broken down by enzymes of living organisms. Such plastics decompose in a matter of days. And some plastics, although not biodegradable, are far more recyclable and reusable than others. Both of these factors--biodegradability and recyclability--are very important to consider as the modern world faces this terrible onslaught of sturdy, toxic trash.

My attention this morning is on a recently discovered aquatic garbage dump known as the "Great Pacific Garbage Patch" or or the "Pacific Trash Vortex." Located in the little-passaged Northern Pacific Ocean doldrums, it is vast, estimated at half a million to ten million square miles in extent. Because of the long, slow, clockwise ocean circulation in this region and the centripetal tendencies in such a vortex, the GPGP draws in waste material from Japan and from the west coast of North America and gradually (over one to five years) deposits it in the central doldrums.

The vast majority of the trash that gathers in the GPGP is plastics. The concentration of plastics reaches, in some areas, one million pieces per square mile. Specific studies have found 3.34 pieces (with an average mass of 5.1 mg) per square meter. This comes to a total (calculator don't fail me now!) of at least 75 million tons of plastic garbage afloat there.

Moreover, this enormous mass--which is increasing year by year--has three particularly diabolical characteristics:
(1) it generally degrades by breaking down into smaller and smaller plastic particles
(2) it is concentrated in the top, most sunlit and biologically active surface layer of the ocean
(3) and--though it closely resembles (and often outnumbers) zooplankton, the main food source for fish and aquatic birds and mammals that inhabit the ecosystem--it is utterly indigestible.

There are five major gyres or circular ocean currents in the world--in addition to the one in the northern Pacific there is one in the northern Atlantic (the northward-bound western portion of which is well known to us as the Gulf Stream), and three others in the southern Pacific, southern Atlantic, and Indian Oceans. (These last three, since they are south of the equator, circulate counterclockwise.) Each of these gyres has a grand garbage dump at the center of its vortex, but none of these have been studied as extensively as the GPGP. Over the next few years we will probably find that they, too, are each accumulating millions of tons of poisonous plastic bits.

So, (1) use as little plastic as you can (natural materials have natural degradation paths),
(2) choose "biodegradable" rather than non-degradable or photodegradable plastics as much as possible,
(3) recycle plastics that you use as much as you possibly can,
(4) vote for mitigating legislation whenever it is available, and
(5) pray for us.