Chapter 9 Chapter 9 Polymers That Never Die

The port of Plymouth in south-west England is no longer listed as a City of Landscape in the British Isles, although it did qualify before World War II. For six consecutive nights in March and April 1941, the Nazi bombing destroyed 75,000 buildings. This is the "Plymouth Blitz" in history.After the bombed-out city center was rebuilt, Plymouth's winding cobbled lanes were replaced by a criss-cross of modern concrete roads, obliterating the traces of the Middle Ages. But the main history of Plymouth is its coast, where the Plim River and the Tamar River meet and flow into the English Channel and the Atlantic Ocean, forming a natural harbor.The Pilgrims set out from here and called their landing point in the United States "Plymouth".Captain Cook's three Pacific expeditions began here, and Francis Drake's circumnavigation of the world departed from here. On December 27, 1831, the British "Beagle" set sail in Plymouth, and 21-year-old Charles Darwin was on board at the time.

Richard Thompson, a marine biologist at the University of Plymouth, often walks Plymouth's ancient banks.He especially liked going in winter, when the beaches of the bay were deserted.Thompson, taller, wore jeans, boots, a blue trench coat and a zip-up cardigan.Thompson's PhD focused on the slimy stuff mollusks like limpets and snails eat: diatoms, cyanobacteria, seaweed, and the small plants that cling to aquatic plants.But Thompson is known not because of his research on marine life, but because of a growing substance in the ocean—but it was never alive. As an undergraduate in the 1980s, he spent autumn weekends convening members of the British National Beach Cleanup Project in Liverpool.Little did he realize at the time that this would be his life's work.In his final year at university, he and 170 teammates collected tons of trash along 85 miles of coastline.Except for items that were clearly dropped from ships, such as the Greek salt extractor and the Italian oil drum, he could tell from the labels that most of the debris had drifted east from Ireland.In turn, the coast of Sweden is also full of rubbish from the United Kingdom.Anything airy and capable of surfacing seems to be driven by the wind—at this latitude, the currents are eastward.

Smaller, less noticeable pieces, however, were clearly held by the currents.Every year when he puts together the annual report, Thompson always finds that more and more of the trash in ordinary bottles and car tires is getting smaller and smaller.So he and another student began collecting sand samples along the shoreline.They sifted through the smallest particles from what looked unusual, and then tried to identify what it was through a microscope.The job was tricky: Their subjects were too small to be sure which bottle, toy or device they came from. He didn't stop at the annual cleanup during his postgraduate years at Newcastle.After getting his PhD, he started teaching at Plymouth with a Fourier Transform Infrared Spectrometer – a device that passes tiny beams of light through a substance and compares its infrared spectrum against a database of known materials .Now, as long as he wants to know, he can know what substance he is observing.

"Do you know what these are?" Thompson led a tourist to the shore of the Primm River, which is very close to the mouth of the sea.A few hours after moonrise, the tide had risen to almost two hundred meters, revealing a flat sandy beach strewn with fucus and cockle shells.The breeze blows over the tide, and the glowing rows of houses on the hillside seem to vibrate slightly.Thompson picked up the rubble left by the crashing waves, looking for anything recognizable: nylon rope, syringes, plastic food containers without lids, supplies from the boat, small crumbs of polystyrene packaging, and There are a wide variety of bottle caps in different colors.The most common ones are the colorful plastic handles of ear swabs.But there are still some small things that look the same but have strange shapes that make it difficult for people to identify.He grabbed a handful of sand, and among the twigs and weed fibers, there were dozens of blue-green plastic cylindrical objects two millimeters high.

"They are called "natto" (plastic granules). They are the raw materials for the production of plastics. People can soften them and make all kinds of things." He went to a distance and dug out another handful of sand with his hands.In this handful of sand, there are more of these plastic particles: grey-blue, green, red, and tan.According to his statistics, each handful of sand contains 20% plastic, which means that each handful of sand contains at least 30 plastic particles. "Actually, now, you can see this substance on all the beaches. They are obviously produced by some factories."

But there are no plastic factories around.These plastic particles waded through the water and settled here, where a combination of wind and tides brought them together. In Thompson's lab at the University of Plymouth, graduate student Mark Brown unwraps a foil-wrapped sample of beach material in a sealed clean bag - sent by a colleague elsewhere in the world.He transferred the samples to a separatory funnel and added a sea salt concentrate to get rid of floating plastic particles.He filtered out what he could recognize—such as the overwhelming number of colored cotton swab handles—and studied it under a microscope.Strange things will be checked again with a Fourier transform infrared spectrometer.

It takes more than an hour to identify a single sample.One-third of the test results were natural fibers such as aquatic plants, another third were plastic, and the remaining third were unknown substances-that is, they could not find them in their polymer database. either the particles had been in water for too long and their color had peeled off, or they were too small for the device to detect.Our equipment can only analyze fragments as small as 20 microns, which is slightly thinner than a human hair. "This means we're underestimating the amount of plastic. In fact, we didn't know there was such a large amount of it before."

What they do know is that there is far more plastic than ever before.In the early 20th century, Plymouth marine biologist Ellisdale Hardy developed a device that could be towed behind Antarctic expedition ships ten meters below the surface to collect samples of krill.Krill are shrimp-like invertebrates about the size of an ant that start many food chains on Earth.In the 1930s, he improved the device to collect even smaller plankton.It was fitted with an impeller to turn over a silk belt, like an automatic paper towel dispenser in a public restroom.The silk filters plankton from the water that flows around it.Each ribbon is capable of sampling 500 nautical miles.Hardy persuaded British merchant ships to tow his "plankton continuous recorder" in the North Atlantic waterway for decades, and the data collected were invaluable, and he was eventually awarded a knighthood for his contribution to marine science.

He took many samples around the island of Great Britain, and every second a sample was analyzed and studied.Decades later, Richard Thompson realized that a sample stored in an air-conditioned warehouse in Plymouth turned out to be a vault of period artefacts documenting how pollution had grown by the day.He cites two routes that are regularly sampled in southern Scotland: one to Iceland and one to the Shetland Islands in north-east Scotland.His crew peered at the preservative-smelling ribbon rolls, searching for plastic left behind.There's no need to look in the pre-World War II history, because there were very few plastics in the world before that, except for phenolic resins used in telephones and radios - devices that were so durable that they're still alive today.Single-use plastic packaging was not yet available.

By the 1960s, though, they found an increase in the number and variety of plastic particles.By the 1990s, there were three times as many fragments of acrylic, polyester, and other synthetic polymers in the samples as there were three decades earlier.To make matters worse, Hardy's "plankton loggers" were collected at a depth of ten meters—they were just suspended in the water.But most plastics can surface, which means that what they see is only a part of the plastic.The amount of plastic in the ocean is on the rise, and there are even smaller plastic particles -- small enough to drift with the tide.

Waves and tides lap the shoreline, turning rocks into sand.Thompson's team realized that this slow, mechanical movement also works on plastics.As long as they oscillate in the waves, the largest and most prominent objects will slowly become smaller and smaller.At the same time, we have yet to find any plastic that biodegrades, not even plastic that has been transformed into tiny fragments. "We envisioned it getting smaller and smaller and eventually being ground into a powder. We also realized that smaller and smaller plastic particles created bigger and bigger problems." Horrific stories he'd heard more than once: sea otters suffocating on the polyethylene liners of beer crates; swans and seagulls dying from nylon netting and fishing line; A foot of nylon cord and toy truck wheels.One of the worst things he experienced personally happened when he was studying fulmars: fulmars whose bodies washed up on the coast of the North Sea, 95 percent of their stomachs were plastic fragments, an average of 100 per bird. Contains 44 tablets.This proportion of plastic would weigh almost five pounds if placed in the human body. Whether it was the plastic that killed them, we don't know, but what is certain is that so many indigestible pieces of plastic blocked their guts.Thompson believes that if large pieces of plastic break down into smaller particles, small organisms might be able to devour them.He devised an experiment in a tank with bottom-sludge-feeding sea gnats that feed on organic sediment, barnacles that leach suspended organic matter from the water, and sand fleas that eat beach gravel.In this experiment, plastic particles and fibers were sized accordingly so that they could be swallowed in one bite.As a result, they quickly ingest the plastic. After the plastic particles entered their intestines, they caused constipation.If the particles are small enough, they can pass through the digestive tracts of these invertebrates and be excreted seemingly unchanged.Does this mean that the composition of the plastic is very stable and will not cause harm to living organisms?Under what circumstances will they naturally decompose?If they do decompose, will they release some terrible chemical components that will cause harm to organisms in the future? Richard Thompson didn't know.Nobody knows.Because plastics haven't been around long enough, there's no way of knowing how long they'll last or how they'll change.His research group has so far identified nine types of plastic from the ocean, different types of acrylic, nylon, polyester, polyethylene, polypropylene and polyvinyl chloride.All he knew was that it wouldn't be long before every creature in the world would be devouring this substance. "When they become as fine as a powder, even zooplankton will swallow them." Thompson had never thought about the source of these two tiny plastic particles before.Plastic bags can clog everything, not just drains, but also turtles' gullets - because they mistake it for jellyfish.We hear more and more about biodegradable plastic bags.Thompson's research group did an experiment.Most are nothing more than mixing cellulose and polymers together.After the fiber starch is decomposed, tens of thousands of plastic particles, which are almost invisible to the naked eye, still clearly exist. Some plastic bags can decompose in compost piles when the heat from rotting organic waste exceeds 100°F, the ad says. "Maybe they can. But that's not going to happen on the beach or in the sea." They concluded from an experiment with plastic bags tied to a mooring in Plymouth Harbour. "You can still use this plastic bag for things after a year." His PhD student Mark Brown's pharmacy-shopping discovery was even more outrageous.Brown opened the top drawer of the laboratory cabinet, and inside were the women's beauty and skin care products: bath and massage cream, skin scrub and hand sanitizer.Some bear the shop's own label: Niova Body Lotion, Sutiko Exfoliator, and DDF Strawberry Almond Exfoliator.The others are international brands: Johnson & Johnson Face & Eye Cleansing Oil, Palmolive Spa, Colgate Ice Toothpaste, Neutrogena, and Clear.Some are also available in the US, while others are limited to the UK.But they have one thing in common. "Scrubs are little particles that massage your body when you shower." He picks out a pink St. Ives almond scrub; the label says it's 100 percent natural scrub. "There's nothing wrong with the ingredients in this stick, the granules are actually ground almond seeds." Other brands that use natural ingredients use grape seeds, jaggery or sea salt. "The rest," he said, sweeping his hand around, "are all plastic." The first three ingredients of the product are "ultrafine polyethylene particles", "polyethylene microspheres" and "polyethylene beads".Or, just write "polyethylene". "Can you believe it?" Richard Thompson's voice was loud, and several faces bent over the microscope all looked up at him in unison, but he didn't intend to ask anyone to answer the question. "The plastic particles they sell go straight into drains, sewers, rivers and oceans. Tiny plastic particles waiting to be ingested by marine life." Plastic pellets are also used to polish paint on ships and aircraft.Thinking of this, Thompson shuddered. "People are amazed at where the paint-coated plastic beads go. It's hard to keep them on a windy day. Even if they could, no sewer has a screen that fine to keep out those tiny particles. It's inevitable. things. They end up in the environment.” He looked at a sample from Finland through Brown's microscope.It's a single green fiber, probably from some kind of plant, and the three light blue strands in the back are most likely not plant fibers.He sat at his workbench, hanging his sneakers on a laboratory stool. "Think about it this way. Suppose all human activity ends tomorrow, and suddenly no one is producing plastic anymore. If the existing plastic keeps breaking down, organisms will have to deal with it forever. It may take Thousands of years, maybe longer." * To put it in perspective, plastic has been around for millions of years.Plastic is a polymer: a single molecular structure of carbon and hydrogen atoms that repeats itself in a chain.Before the Carboniferous, spiders spun silk to form the polymer fibers we call silk, and trees produced cellulose and lignin—also natural polymers.Cotton and rubber are polymers; we humans also grow our own polymers called collagen—our fingernails, for example. Another natural, moldable polymer that fits our idea of ​​"plastic" is the secretion of the Asian gum bug, which we call "shellac."It was in his search for an artificial alternative to shellac that chemist Leo Baekeland one day mixed pyrocarbonic acid, phenol, and formaldehyde in his garage in Yonkers, New York.Until then, shellac had been the only material used for wire and wiring wrapping.The result of molding is Bakelite.Baekeland became a rich man, and the world has changed since then. It didn't take long for chemists to work on cracking oil's long hydrocarbon-chain molecules into smaller molecules, then mixing the fractions to see if they could create something else based on Baekeland's first man-made plastic. What plastic.When chlorine was added, the plastic became a much stronger blend of polymers with no parallel in nature, known today as polyvinyl chloride.Blowing gas during the formation of this polymer blend creates a tough, interconnected foam known as "polystyrene," commonly known by the product name: Styrofoam.The relentless quest for rayon led to the creation of nylon.The introduction of nylon socks alone revolutionized the clothing industry; nylon played a role in the acceptance of plastic as an affirmation of modern life.In World War II, most of the nylon and plastic went to the military, but the desire for them only grew stronger. After 1945, an unprecedented abundance of products entered the homes of ordinary people: acrylic textiles, Plexiglas, polyethylene bottles, acrylic containers and "foam latex" polyurethane toys.What changed the world the most was the advent of clear packaging, including sticky plastic wrap made of polyvinyl chloride and polyethylene, which allows us to wrap food in it and keep it longer than before. Within a decade, the flaws of this wonder substance were revealed. Life magazine coined a phrase called the "disposable society," although throwing out trash is nothing new.There will be leftover bones from hunting, and leftover chaff from harvesting. Since then, humans have started throwing out garbage, and then other creatures will take over this "garbage".Man-made items go down the drain, and at first people think they're less of a nuisance than stinky organic waste.Broken bricks and pottery provided building materials for generations to come.Discarded clothing turns up in secondary markets run by thrift dealers, or is recycled into new textiles.The parts of broken machines piled up in the junkyard can be reused and assembled into new machines.Blocks of metal can be melted down and made into completely different things.World War II—at least Japan's navy and air force—was built from American scrap heaps. William Reese, an archaeologist at Stanford who studies America's trash problem, explains to waste officials and the public what he believes to be a myth: Plastic is responsible for the country's litter.Reese's waste research program spans decades.For the project, his students weigh and measure residents' waste that has accumulated over weeks.In the 1980s, their research reported that, contrary to popular belief, plastics accounted for only 20 percent of landfill waste in volume, in part because they could be compressed more easily than other wastes. close.Although people are producing more and more plastic, Reese doesn't see that percentage changing, as less and less plastic is being used to make soda bottles or single-use packaging. Construction waste and paper products account for the most landfills, he said.He explained that newspapers cannot biodegrade when buried in the absence of air and water—again, contrary to popular belief. "That's why we still see ancient Egyptian papyrus scrolls from 3,000 years ago. We've pulled newspapers from the 1930s out of landfills and they're still quite legible. They're here to stay a thousand years." Still, he agrees that plastic is a manifestation of human pollution of the environment.It's disturbing that plastic lasts forever.The difference between plastic and newspaper goes beyond landfills: Even if newspaper doesn't burn, it shatters in the wind, cracks in the sun, and dissolves in the rain. However, what will happen to the plastic?We can see more intuitively where garbage is not collected.Humans have lived in the Hopi Indian Territory in northern Arizona since 1000 AD, which is the oldest human settlement in the United States today.Hopi villages are mainly concentrated on three flat-topped mountains, which can overlook the surrounding desert in all directions.For centuries, they dumped their trash, ranging from food scraps to broken ceramics, at the foot of the mesas.Coyotes and vultures take over the food waste, and pottery returns to the soil. This model worked well until the mid-twentieth century.Suddenly, nature can no longer take care of the garbage that people dump on the side of the mountain.The Hopi is surrounded by an ever-higher pile of new types of junk.Only when the wind blows in the desert does the rubbish disappear from view.Yet they are still there, hanging from the branches of sagebrush and pea trees, or poking at the spines of cacti. To the south of the Hopi Mesa lies the 12,500-foot San Francisco Peak, where forests of aspen and Douglas fir are home to the Hopi and Navajo gods: the sacred mountain is clothed in a white mantle every winter—however, more recently There has been no such scene for several years, because it rarely snows.Droughts are intensifying and temperatures are rising.The Indians claimed that the operators of the ski resorts had polluted this sacred ground with their clanging machines and dirty money, and they were sued again.Their latest act of desecration is laying artificial snow made of waste water on the ski slopes, which in the eyes of the Indians is equivalent to washing the face of the gods with excrement. To the east of the San Francisco peaks are the more majestic Rockies; to the west are the Sierra Madre—its volcanic summit at a higher elevation.It is hard to believe that these massive mountains will one day be buried in the sea - boulders, rocks, coves, peaks and canyons no exception.Each gigantic bulge will corrode to powder, the minerals they contain will dissolve into seawater salts, and the nutrients in their soil will create a new age of marine life, and the previous age of life will disappear in their place. below the resulting deposits. But before that, something much lighter than rock or sediment particles and more easily carried by seawater would pre-deposit. Captain Charles Moore of Long Beach, Calif., sailed from Honolulu one day in 1997, aboard his aluminum-hulled schooner into an area of ​​the western Pacific that he had traditionally avoided.Sometimes called the subtropical calm, it's about the size of Texas and lies in the ocean between Hawaii and California.The crew rarely come here, because there is a high-pressure cyclone formed by hot equatorial air that rotates slowly all year round, and the wind can only enter and exit here.Beneath the cyclone, seawater slowly forms a clockwise eddy toward its center of low pressure. Its correct name should be the North Pacific subtropical cyclone, but soon after, Moore learned that oceanographers had given it another name: the Great Pacific Garbage Patch.Captain Moore lost his way and entered this vortex - where almost all the garbage blown into the sea in North America ends up collecting, slowly circling around the vortex.These industrial wastes are accumulating more and more, which is really frightening.For a week, Moore and his crew sailed across the ocean, about the size of a small landmass, filled with floating trash.Moore's ship was like an arctic icebreaker shoveling ice, except that floating up and down around them were cups, bottle caps, tangled fishing nets, monofilament, scraps of polystyrene bags, Cartons of canned beverages, broken balloons, bits of sandwich wrap and countless loose plastic bags. Moore retired from a wood furniture polisher just two years ago.He has battled the waves all his life, and his hair has not yet turned gray. He wants to build himself a boat, live in it, and enjoy the exciting life after early retirement.Influenced by his sailor father, he was later approved as a captain by the U.S. Coast Guard.He started out as a volunteer with the Marine Environment Monitoring Group.Since he encountered the hellish "Pacific Garbage Patch" in the middle of the Pacific Ocean, his group has transformed into the current El Kita Marine Research Base, dedicated to remediating the floating garbage of the past half century.Ninety percent of the trash he saw was plastic. After learning the source of these plastics, Moore was even more shocked. In 1975, the U.S. National Academy of Sciences estimated that all ships that go to sea emit a total of 8 million tons of plastic each year.Research now shows that the world's merchant fleet alone brazenly emits some 639,000 plastic utensils every day.But Moore found that the litter that was thrown away by the merchant fleet and navy paled in comparison to the aggregates that were dumped into the sea from the coast. He found that the real reason landfills aren't filled with plastic is that most of it ends up in the ocean.Over the years, Moore has sampled that eddy in the North Pacific, and he has come to the conclusion that 80 percent of the floating debris in the middle of the ocean is initially discarded on land. Winds blow them off garbage trucks or out of landfills, and they sometimes fall from railroad containers and into storm sewers, downriver or with the wind, and end up in this ever-expanding in the vortex. Captain Moore said to his passengers, "This is where things go down the rivers and into the sea." That's the first thing geologists say to their students, but they mean corrosion - relentless The corrosion process of the earth fragmented the mountains into salt substances, which were small in size and entered the ocean along with the rainwater, where they were deposited layer by layer and became rocks in the distant future.Moore, however, is referring to a phenomenon of loss and deposition unprecedented in Earth's 5-billion-year geological epoch—and one that we may learn about later. During the first 1,000 miles through the whirlpool, Moore calculated that there was half a pound of rock debris and 3 million tons of plastic per 100 square meters of ocean surface.His estimates matched those of the U.S. Navy.And that's just the first of the scary numbers he's encountered.And that's just the visible plastic: the larger numbers of plastic fragments, corroded by algae and barnacles and sunk in the sea, are unknown. Moore came here again in 1998, this time with a trawling rig similar to that used by Sir Ellistair Hardy to collect krill samples, and made a startling discovery: There is more plastic than there is floating on the ocean. In fact, the difference in numbers is quite dramatic: there is six times as much plastic in seawater as there is on the surface. When he sampled the estuary of a river in Los Angeles, that number increased tenfold, and it increased every year.Now he is comparing the data with Richard Thompson, a marine biologist at the University of Plymouth.What surprised them both were the plastic bags and the ubiquitous pellets of raw plastic.Kenya produces 4,000 tons of plastic bags every month that cannot be recycled. These raw pellets are called "natto," and humans produce 5,500 trillion pellets each year, weighing 250 billion pounds.Moore not only found that plastic has taken over every corner of the world, but also clearly saw the debris of plastic resin entering the transparent bodies of jellyfish and salps—the most abundant and widespread filter feeders in the ocean.Like waterfowl, they mistook the brightly colored raw pellets for fish eggs and the dull ones for krill.Coated with body-cleaning chemicals, the pellets are just the right size for small creatures that feed on the larger ones...presumably God only knows how many plastic particles have been washed into the ocean. What does this mean for oceans, ecosystems and the future?Plastics are only fifty years old.Their chemical components or additives—for example, will coloring agents such as metallic copper advance toward the upper reaches of the food chain, gather and concentrate, and eventually affect the evolution of organisms?Will they become the fossil record? Will geologists millions of years from now find Barbie doll parts in conglomerates deposited on the ocean floor?Will they be so intact that they can be pieced together like dinosaur bones?Or is it possible that they rot, hydrocarbons slowly escaping from Poseidon's plastic graveyard, and all that's left is that while Barbie and Ken 20 have become fossilized imprints, will they turn to stone forever? Moore and Thompson began consulting materials experts.Hidezuka Takada, a geochemist at the University of Tokyo, works with endocrine-disrupting chemicals, or "gender-benders."All the while, he's had the unsavory task of figuring out exactly what hideous substance is escaping from the garbage dumps of Southeast Asia.Now, he's studying piles of plastic pulled from the Sea of ​​Japan and Tokyo Bay.In the ocean, "natto" and other plastic debris can combine with resilient pollutants such as DDT and various PCBs, he reports. Since 1970, the highly toxic polychlorinated biphenyls, which make plastics more flexible, have been banned; among the harmful substances, polychlorinated biphenyls are known to disrupt the secretion of hormones, such as for hermaphrodites Both fish and polar bears can cause damage.Like time-release capsules, pre-1970 floating plastics released PCBs into seawater for centuries to come.However, Takada also found toxic floating waste from various sources—graphics paper, car oil, coolant, aging glow sticks, and the notorious smog that General Electric and Monsanto factories dumped directly into rivers. Scrap - has stuck to the surface of free-floating trash. One study found plastics containing PCBs in the fatty tissue of puffins.What is astonishing is the sheer number of them.Hidetsuka Takada and his colleagues found that the toxins in the plastic pellets eaten by the birds were a million times higher than normal in seawater. By the time Moore spoke of the Pacific garbage vortex in 2005, it was 10 million square miles in size—about the size of the continent of Africa.This isn't the only vortex: There are a total of seven major tropical oceanic cyclones around the world, and they all create ugly garbage eddies.After World War II, plastic grew from a small seed, eventually detonating the entire world, and like the Big Bang, it is still expanding.Even if all plastic manufacturing were to cease instantaneously, this substance would already be present in the environment in staggering quantities and longevity.According to Moore, plastic debris is now the most common substance in the ocean.How long will they exist?Are there any benign, less long-lasting alternatives for humans to use in order to prevent our world from ending up as a plastic-encased planet? That fall, Moore, Thompson, Takata and Anthony Andretti met at the Ocean Plastics Summit in Los Angeles.Andretti, a senior researcher with the North Carolina research trio, is from Sri Lanka, a major rubber producer in Southeast Asia.He studied polymer science at postgraduate level, and his interest gradually shifted from rubber to the emerging plastics production and processing industry.He later compiled an 800-page tome, Plastics in the Environment, which is considered a classic by academics and environmentalists alike. Andretti told the assembled marine scientists that the predictions for plastic are just one word: long term.It's no accident that plastic is causing such enduring chaos in the oceans, he explained.Their elasticity, versatility (they can sink and float), stealth in water, durability and super strong strength are the reason why the manufacturers of fishing nets and fishing lines abandon natural fibers and use artificial ones such as nylon and polyethylene. The reason for the synthetic material.After a long time, the former will decompose; but even if the latter is no longer useful due to breakage, it is still a killer of marine life.As a result, almost all marine life, including whales, is also at risk from the threat of nylon "traps" in the ocean. Andretti says that, like all hydrocarbons, even plastics "will inevitably biodegrade, but it's too slow to be of practical use. Photodegradation is much better, though." He explained that when hydrocarbons biodegrade, their aggregated molecules break down into their raw materials: carbon dioxide and water.When they photodegrade, ultraviolet radiation breaks the plastic's long chain-like polymer molecules into shorter fragments, reducing its tension.Because plastic is only as strong as the length of the polymer chains that hold it together, when UV light breaks them apart, the plastic begins to break down and rot. Everyone has seen polyethylene and other plastics yellow, age and chip in the sun.塑料经常被覆上添加剂，使之更能抵御紫外线的侵蚀；另外一些添加剂则有相反的效果，使它们对紫外线更加敏感。安德瑞蒂暗示说，如果罐装饮料的手提纸箱用的是后者，那么便能拯救许多海洋生物的生命。 然而，这里有两个问题。第一，塑料在水中光降解的速度相当缓慢，在陆地上，阳光照射下的塑料会吸收红外线热量，不用过多久就会比周围的空气更热。在大海中，塑料不仅受到了海水的冷却，海藻也使其免于阳光的照射。 第二个问题是，即使可光降解的塑料制成的渔网真的能够分解，而不再溺死海豚，可塑料的化学特性在几百年、甚至几千年之内都不会发生任何变化。 “塑料就是塑料。这种材料还是聚合体。聚乙烯生物降解的过程漫长无比，很不现实。海洋环境中没有任何机制能生物降解如此之长的分子。”他最后说，即使可进行光降解的渔网真能拯救海洋哺乳动物的生命，它们粉状的残余物还是在海水中，滤食动物终会发现它们。 “除了一小部分已经烧为灰烬，”安德瑞蒂说：“我们五十年来制造的每一小片的塑料依然存在着。它们肯定存在于自然环境中的什么地方。” 半个世纪的总产量超过了10亿吨。塑料的种类成百上千，还有添加了可塑剂、遮光剂、颜料、填料、加固剂和稳定剂等数不清的新品种。每种塑料的寿命有很大的差异。到目前为止，没有任何一种塑料消失于世。研究者曾做过实验，把聚乙烯样本放在有活细菌的环境下，调整到最佳状况，看看生物降解到底需要多少年。一年之后，降解掉的塑料连百分之一都不到。 “这是在控制得最好的实验室条件下得出的数据。在现实生活中根本无法达到这样的结果，”安德瑞蒂说：“塑料存在的时间还不长，微生物还未进化出对付它的酶，所以它们只好降解塑料中分子量最低的部分。”这指的是已经破裂的最小聚合体链。虽然来自天然植物糖、真正可以进行生物降解的塑料已经出现，细菌做成的可降解聚酯也已问世，但是它们取代现有塑料制品的几率并不高。 “包装的目的就是保护食物不受细菌的污染，”安德瑞蒂已经关注过这个问题：“用吸引微生物的塑料来包裹食物或许不是件聪明的事。” 然而，即使这些方法真的有效，即使人类消失再不生产“纳豆”，业已存在的塑料还是留在环境中——它们要停留多久呢？ 安德瑞蒂脾气温和，做事严谨，脸宽宽的，说起话来字正腔圆、思维清晰、颇具说服力：“埃及金字塔保存了玉米、种子，甚至头发之类的人体组织部分，因为它们被封闭起来，远离阳光的照射，也很少接触氧气和水汽。我们的垃圾场和金字塔很像。埋藏在少有水份、阳光或氧气的地方的塑料在很长一段时间内都会保持原状。如果它沉入海洋，被埋藏在沉积物的下面，结果也是如此。洋底没有氧气，也很寒冷。” 他突然笑出了声。“当然，”他接着说：“我们对那么深处的微生物知之甚少。或许那里的厌氧生物有本事降解它们。这并不是完全不可能。但是没有人能潜入水底探个究竟。根据我们现在的观察，这样的可能性实在是很小。我们认为海底的生物降解速度要慢得多，需要的时间更长。甚至会相差一个数量级。” 数量级指的是两个数字相差十倍。那么，要长多久呢？一千年？还是一万年？ 没人说得清楚，因为人类至今未曾见过“寿终正寝”的塑料。今天能够分解建筑材料中的碳氢化合物的微生物是在植物出现后很久才学会了降解木质素和纤维素。最近，它们甚至学会了降解油类物质。现在还没有什么微生物有能力降解塑料，因为五十年对于进化出必要的生物化学成分而言实在是太短了。 安德瑞蒂对此持乐观态度。2004年圣诞节时发生海啸的时候，他正巧在斯里兰卡老家，尽管经历了老天爷的水灾惩罚，人们还是保留希望、保持乐观。“给它们十万年时间，我相信你到时会发现，有很多微生物已经具备降解塑料这个壮举的基因。它们的数量将增加，欣欣向荣。今天那么多的塑料需要几十万年才能被微生物消耗，但最终，它们还是会被降解掉的。木质素的结构要复杂得多，但它还是被降解了。我们要做的是等待，等待微生物的进化赶上我们制造的材料。” 如果生物的时代已经过去，可塑料依然还有，地质时代总还是能接管下去的。 “地质突变和压力会使塑料变为其它物质。这好比许久以前埋藏在沼泽中的树木——是地质过程，而非生物降解将它们转变为石油和煤炭。或许高度浓缩的塑料会变成什么类似的物质。总之，它们肯定会变。变化是大自然的特点。没有什么可以永恒不变。”