第17课听力
| UNIT 17 Saving the Environment The effort to save the environment derives much of its political popularity from the impact of immediate personal inconveniences: a sewage polluted beach, the smog that leaves one's eyes watering, the black granules of soot that drift in through an open window, traffic jams , noise, the smoking vehicles and industries. But the significance of the current consciousness for the environment protection goes much, much deeper than nuisance reduction. It is a postponed recognition that as we "succeed" in terms of production, size, speed, growth, quality of life may deteriorate our living conditions disastrously. It is a delayed recognition of our unity with nature, a concern for man himself and his natural environment. It is a delayed awareness that our fate as individuals is in fellowship with our fate as a species and the future of life on this planet. Precisely because we have recognized late, we must redouble our efforts to gain command of the situation. We must take all the means at our disposal- basic and applied research, public education, and, above all, the governmental action. We could have a productive, prosperous society without destroying the ecological balance of our environment. Why should man create the impropriety of material plenty around poisoned air, polluted water and mountains of solid wastes? Russia is currently concerned with the fight to save Lake Baikal, four hundred miles long and six thousand feet deep. The beautiful, wooded shoreline is being inhabited upon by new industrial plants and a new generation of Russia conservationists is raising a challenge. The United States contains less than 6 percent of the world's population but it consumes 34 percent of the world's production and brings about much more than 5 percent of the world's pollution. Each American in his lifetime uses an average of 26 millions gallons of water, 21 000 gallons of gasoline, 10 000 pounds of meat, 28 000 pounds of milk and cream, $ 6 000 worth of clothing and $ 7 000 worth of furniture. Each year, people in the United States discard 7 millions automobiles and 100 millions tires, 20 million tons of paper, 28 billion bottles and 48 billions cans. Just to collect the garbage costs $ 2.8 billion a year. The United States factories get rid of 165 million tons of solid wastes and 172 million tons of smoke, vehicle emissions and other forms of atmospheric pollution. Eighty three million United States automobiles contribute 60 per cent of air pollution in urban districts. Each year, the United States paves over a million acres of field, forests and rural green spaces. Fortunately, saving the environment has become a popular crusade aided especially by the energy and concern of young people. Man is beginning to realize that he must drastically alter his pattern of shortsighted abuse of the natural resources if he wants to survive. Large firms are moving to compete with the small ones; specialist makers of pollution control equipments have watched their own sales increase tenfold. We must achieve interaction of popular pressures and enthusiasm, the precise application of sizable funds and technological skills, and the wise action of government at all the levels of our socio economic system. That means federal, state and local governments should coordinate their efforts to solve the problems. While polluted air almost never appears on a death certificate, medical research strongly implicates it as a contributing cause of many deaths. Polluted air influences health gradually, so its effects are extremely difficult to pinpoint. However, mounting evidence indicates a steady increase in the incidence of such respiratory diseases as asthma, bronchitis, lung cancer, and emphysema. Cities with an abundance of air pollution have the greatest incidence of these diseases. The number-one cause of atmospheric pollution is the automobile. Some further observation is needed on this subject, but the automobile is indeed a crucial polluter and killer. The accident death rate from automobile is currently in excess of fifty-five thousand people every year. The automobile creates traffic jams in the cities and junkyards in the countryside. Experts say the family car has made possible not only the spread of the suburbs but also the abandonment of central cities. The internal combustion engine may well give place to other forms of propulsion. However, research work on the electricity, steam and hybrid gasoline natural gas powered automobiles has not proceeded very far. The fact is that no one has yet invented a substitute which has adequate performance, reliability,and safety, or which can be produced at a reasonable cost and requires a minimum of maintenance. We have made progress in cleaning up the atmosphere, in part because the public recognizes the health dangers and is willing to accept the expenditures. But there has little progress, nationally speaking, against noise pollution, because so little is known about the subject. Noise pollution is, in fact, a threat to millions that could be as dangerous as the pollution of the atmosphere. Clinicians believe that prolonged exposure to noise, especially to sharp, sudden, surprise sounds, produces severe involuntary response in the digestive nervous systems. Human ears cannot shut out noise in sleep in the same way eyelids shut out light. The constriction of blood vessels by noise pollution can go on all night long. Many people are fatigued by their efforts to remain asleep in the midst of urban noise. The lowest audible sound is one decibel and louder sounds are measured upward on a logarithmic scale. Twenty decibels is ten times 10 decibels, and 80 decibels is a million times louder than 20 decibels and 30 or so if it is dropped on a wooden library floor. The ordinaryconversation level in an average size room runs at approximately 60 decibels. Sounds of 80 decibels or more are uncomfortable to human ears. Decibel levels of 90 or more are estimated by doctors to present a health hazard. Decibel levels of 100 or more are a definite threat to hearing. Heavy city traffic is measured at 90 to 95 decibels, and a common household food blender at 93 decibels. Air hammers and air compressors along city sidewalks erupt in sudden blasts of 95 decibels. This is also the reading, incidentally, of a subway train screaming around a curve. Farm tractors can sound at 98 decibels, roughly the same as a newspaper printing press. Incredible as it may seem, there are many familiar implements of modern life that measure 100 decibels and above. These include loud outboard motors, powering along offshore, 102 decibels; textilelooms, 106 decibels; riveting guns, 110 decibels on up, usually way up. There are psychological effects of noise pollution. Starting sounds contribute to outbursts of anger among normally placid people. A dropped toy, a blaring television set, a police siren, a tingling telephone, a suddentruck noise, might propel a neurotic to minor violence. As for prolonged, steady sound, men and women exposed to it are more inclined to quarrel or act foolishly. A British study showed not long ago that people who lived near deafening London airport were admitted to mental hospitals at a higher rate than people living in quiet districts in the same part of the country. The noises of our daily life have been blamed variously for the high divorce rate, social conflict, indigestion, nervous breakdown, high blood pressure, heart failure, and even insanity. The damage is done deep in the inner ear, near the brain, to the delicate cilia, rows of micro scopic, hair like organs capable of responding individually to thousands of frequencies of sound. The first of these tiny organs to be injured by noise are those, which respond to the higher frequencies above the level of speech. But the hearing loss takes place very gradually, and deafness is often not noticed until it is too late to take corrective measures. In fact, most city dwellers have "invented" their own methods of withstanding noise pollution. They turn on a low decibel producer a fan or an air conditioner to strain out and distill the louder noises and make indoor life more preferable. Some states have passed laws against defective motorcycle mufflers, against alarms on other than emergency vehicles, against inadequate mufflers on automobiles. New York city prohibits the use of automobile horns on stationary vehicles, except as a danger signal. The city also bans the use of any vehicles out of repair to avoid creating loud and unnecessary grating, clashing, or other noises. The city forbids the unnecessary blowing of steam whistles and, along with the state, the use of a stationary internal combustion engine without an effective muffler. There are city laws against excessive noise near schools and hospitals and in the loading and unloading of vehicles. The shouting of street hawkers is forbidden. The dull hum of fans and air conditioners continues to be the citizen's principal weapon against neighbors' conversations. The development of off-site, prefabricated houses by the Office of Housing and Urban Development in Washington has offered new hope of effective noise controls. The house devised is simpler and less costly to install. Another promising new concept is the development of portable, soundproofed rooms for installation in homes, offices, or industrial plants. Noise control technology in transportation is also being devised. General Motors has designed quieter public trucks, conducting new research into noise abatement features of body and structural framework design, and making its findings available to other manufacturers. Trucks may be required to reduce diesel engine noise by simple techniques that have already been tested in diesel bus design, basically a sealed engine compartment, mechanically ventilated by fans. Small discharge and line mufflers may reduce air brake noise and frantic pumping sound. Tires may be designed with cross bar and rib treads to minimize the familiarwhirring noise. The air transportation industry also has a major noise problem. Aircraft technology is only one part of the problem, however. The other is the quality of life in residential, industrial, and wildlife areas in the vicinity of airports. The noise of the jets is indeed substantial. Environmental factors must be considered well in advance in all aspects of aviation planning. Reducing the pollution of our rivers, lakes, streams, and offshore waters is important for the coming generation. We have made visible and encouraging progress by operating new sewage disposal projects. Sewage treatment plants' construction has improved the quality of ten billion gallons of water a day some 20 percent of all of our fresh water resources. Pollution of the rivers, streams, and lakes must be ended as quickly as possible as a prerequisite for our good future and our good health. We can stop water pollution if we are prepared to pay the price. The basic technology of sewage control has been successfully developed. The primary need is for more sewage treatment of plants and filters. Municipal collection systems gather the sewage in lateral and trunk sewers. When treatment is not provided, the sewage is dumped directly into the nearest waters. Filters are designed to gather sewage from these trunk and lateral sewers and bring them to the treatment facilities. Treatment plants receive sewage from collection systems and from filters. Treatment then eliminates many of the harmful composition of sewage by sedimentation, biological or chemical action, and purification. Primary treatment (sedimentation) is always necessary. Secondary treatment (biological and chemical action is also always necessary. Chlorination (purification) is needed in most cases. To eliminate existing pollution in industries not tied to municipal sewage collection systems, there must be separate industrial facilities and even changers in industrial processes. |
京公网安备 11011202003401号
