Monday, June 22, 2009

Pacific Garbage Patch

The existence of the Pacific garbage patch and its apparent longevity is naturally troubling however we wish to ignore it and hope it goes away. Except that begs two issues. The plastic itself keeps coming because we have not decided to make all plastics either reasonably biodegradable which in the presence of sea water cannot be a major trick, or alternatively make it dense enough to simply sink and let geological processes complete the task. Ignoring the problem is not a good option.

We also have little sense of the actual lifetimes of the plastics now adrift. There is a lot of small pieces which graphically shows us that most of the material has likely already been mechanically reduced on the beach. How long do these little pieces stand up? I would love to know that the problem is resolved naturally at the level of fines in say five years. More likely, we are talking about twenty years.

The point I wish to make is that we need some real answers. Mother Nature has ultraviolet and oxidation in seawater to throw against the problem and that is pretty potent. It would be a blessing if that were enough. The evidence so far shows us that Mother Nature is struggling.

The question then is that is it possible to mechanically remove the problem in part at least. The short answer is perhaps, but it will certainly cost.

I can envisage a horizontal drum float acting as the upper jaw and a lower jaw below holding a flow through conveyor belt formed from a strong mesh. Behind we have the other end of the fairly short conveyor belt held above water and naturally dropping debris into a recovery trough holding an auger that draws the debris into a compactor. Compacted blocks are then dense enough to dump. I think that is about as simple as it gets. It is all sort of a simulation of a whale. I hope the whales do not try to eat this crap. Operating in the areas of high density, it is plausible that real headway could be made.

Who knows, we may get enough torque of the drum float to drive the conveyor belt somehow. Anyway this becomes an engineering problem whose difficulty may be that the problem is simply too big. Particularly when a net catches material deeper than it capability.

Today, science needs to provide some answers to difficult questions and troubling concerns.

Voyage to the Pacific Ocean's 'Garbage Patch'
By
Larry Greenemeier

Editor's Note: Scuba instructor and underwater videographer
Drew Wheeler is traveling on board the Algalita Marine Research Foundation's 50-foot (15.2-meter) Ocean Research Vessel, Alguita, on a two-month voyage to sample and study portions of a 10-million-square-mile (25.9-million-square-kilometer) oval known as the North Subtropical Gyre (a.k.a. "Pacific Garbage Patch"). Wheeler and the rest of the Alguita crew left Long Beach, Calif., on June 10 with a plan to cross the International Date Line and investigate regions of reported high plastic concentrations, northwest of the Hawaiian Islands. This is his first blog post for ScientificAmerican.com.

Well, we are one week into our journey, and already Mother Nature has proved to be the boss. We expected to have a day or two of northwesterly winds. But we thought once we left shore behind, our catamaran would catch the prevailing northeast trade winds and take us to our objective—the international dateline, north of Hawaii.

Not so fast. We had five days straight of almost pure north wind that kept pushing us farther and farther south. At one point Alguita Captain Charles Moore made the famous call, "We can't there from here." So we then started discussing other objectives, finally settling on an area where some plankton are blooming, just northeast of the Hawaiian island chain.

There is a theory that the same current and weather patterns that lead to plankton clouds may also corral the plastics on the ocean surface, so we are going to see if this is the case. According to [National Oceanic and Atmospheric Administration (NOAA)]
coastal watch scientist Dave Foley, there is a bloom occurring as we speak, and we are only a few days away, so we are going for it.

Up to this point we have had three successful trawls of the water's surface, gathering data from a region never sampled before. We found plastic material in all three runs, but at a rather low concentration. The results weren't all that surprising because we are on the outside edge of the Northern Subtropical Gyre. Still, it is disturbing to find plastic in any sample taken in the middle of the Pacific.

I have had two chances to go for quick swims and check out my underwater video system. Both times I followed the captain as he spotted plastic floating beneath the surface and gathered it up with his trusty aquarium net.

We found a piece of a plastic packing band and a fragment of a disposable grocery bag along with other small particles. It is important to note that these plastic pieces were found and recovered from depths deeper than the
Manta Trawl could collect. It will be interesting to see what the bongo trawls will reveal.
The crew is getting along fine, which is a good thing because we are stuck on a 50-foot (15.2-meter) catamaran for the next five weeks. Everyone contributes by pulling watch and assisting with the sampling. Spirits are still high despite the slow start and change of plans.

So with our new target location set into the navigation system, it's off into the wild blue yonder.
The journey continues…

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