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Part 4 Air Pollution 空气污染
Air is the ocean we breathe. Air supplies us with oxygen which is essential for our bodies to live. Air is 99.9% nitrogen, oxygen, water vapor and inert gases. Human activities can release substances into the air, some of which can cause problems for humans, plants, and animals.
There are several main types of pollution and well-known effects of pollution which are commonly discussed. These include smog, acid rain, the greenhouse effect, and "holes" in the ozone layer. Each of these problems has serious implications for our health and well-being as well as for the whole environment.
One type of air pollution is the release of particles into the air from burning fuel for energy. Diesel smoke is a good example of this particular matter. This type of pollution is sometimes referred to as "black carbon" pollution. The exhaust from burning fuels in automobiles, homes, and industries is a major source of pollution in the air. Some authorities believe that even the burning of wood and charcoal in fireplaces and barbeques can release significant quantities of soot into the air.
Another type of pollution is the release of noxious gases, such as sulfur dioxide, carbon monoxide, nitrogen oxides, and chemical vapors. These can take part in further chemical reactions once they are in the atmosphere, forming smog and acid rain.
Smog is a type of large-scale outdoor pollution. It is caused by chemical reactions between pollutants derived from different sources, primarily automobile exhaust and industrial emissions. Cities are often centers of these types of activities, and many suffer from the effects of smog, especially during the warm months of the year.
Another consequence of outdoor air pollution is acid rain. When a pollutant, such as sulfuric acid combines with droplets of water in the air, the water or snow can become acidified . The effects of acid rain on the environment can be very serious. It damages plants by destroying their leaves, it poisons the soil, and it changes the chemistry of lakes and streams. Damage due to acid rain kills trees and harms animals, fish, and other wildlife.
The Greenhouse Effect, also referred to as global warming, is generally believed to come from the build up of carbon dioxide gas in the atmosphere. Carbon dioxide is produced when fuels are burned. Plants convert carbon dioxide back to oxygen, but the release of carbon dioxide from human activities is higher than the world's plants can process. The situation is made worse since many of the earth's forests are being removed, and plant life is being damaged by acid rain. Thus, the amount of carbon dioxide in the air is continuing to increase. This buildup acts like a blanket and traps heat close to the surface of our earth. Changes of even a few degrees will affect us all through changes in the climate and even the possibility that the polar ice caps may melt.
Ozone depletion is another result of pollution. Chemicals released by our activities affect the stratosphere , one of the atmospheric layers surrounding earth. The ozone layer in the stratosphere protects the earth from harmful ultraviolet radiation from the sun. Ultraviolet radiation is known to cause skin cancer and has damaging effects on plants and wildlife.
Pollution also needs to be considered inside our homes, offices, and schools. Some of these pollutants can be created by indoor activities such as smoking and cooking.
In many countries in the world, steps are being taken to stop the damage to our environment from air pollution. Scientific groups study the damaging effects on plant, animal and human life. Legislative bodies write laws to control emissions. Educators in schools and universities teach students, beginning at very young ages, about the effects of air pollution.
The first step to solving air pollution is assessment . Researchers have investigated outdoor air pollution and have developed standards for measuring the type and amount of some serious air pollutants. Scientists must then determine how much exposure to pollutants is harmful. Once exposure levels have been set, steps can be undertaken to reduce exposure to air pollution. These can be accomplished by regulation of man-made pollution through legislation. Many countries have set controls on pollution emissions for transportation vehicles and industry.
Prevention is another key to controlling air pollution. The regulatory agencies mentioned above play an essential role in reducing and preventing air pollution in the environment.
In addition, it is possible to prevent many types of air pollution that are not regulated through personal, careful attention to our interactions with the environment. Only through the efforts of scientists, business leaders, legislators, and individuals can we reduce the amount of air pollution on the planet. This challenge must be met by all of us in order to assure that a healthy environment will exist for ourselves and our children.
所谓干洁空气是指在自然状态下的大气，由混合气体、水气和杂质组成，当大气中污染物质的浓度达到有害程度，以至破坏生态系统和人类正常生存和发展的条件，对人或物造成危害的现象叫做大气污染。造成大气污染的原因，既有自然因素又有人为因素，尤其是人为因素，如工业废气、燃烧、汽车尾气和核爆炸等。随着人类经济活动和生产的迅速发展，在大量消耗能源的同时，同时也将大量的废气、烟尘物质排入大气，严重影响了大气环境的质量，特别是在人口稠密的城市和工业区域。
大气中的二氧化碳浓度增加，阻止地球热量的散失，使地球发生可感觉到的气温升高，这就是有名的“温室效应”，致使地球气温上升。
随着工业化和能源消费增多，酸性排放物也日益增多，它们进入空气中，经过一系列化学作用就形成了酸雨。人们对酸性排放物已经有了控制，但仍然还有酸雨现象。大气尘埃可能是造成酸雨问题的另一原因。
臭氧层是地球最好的保护伞，它吸收了来自太阳的大部分紫外线。然而近二十年的科学研究和大气观测发现：每年春季南极大气中的臭氧层一直在变薄，事实上在极地大气中存在一个臭氧“洞” 通过不断的科学研究，人们发现人类社会活动释放的物质严重的破坏了臭氧层，当然这种现象还受到这一地区独特的气象状态（极涡、寒冷的平流层温度、极地平流层云）的影响。
大气被污染后，由于污染物质的来源、性质和持续时间的不同，被污染地区的气象条件、地理环境等因素的差别，以及人的年龄、健康状况的不同，对人体造成的危害也不尽相同。大气污染对人体的危害主要表现为呼吸道疾病；对植物可使其生理机制受抑制，生长不良，抗病抗虫能力减弱，甚至死亡；大气污染还能对气候产生不良影响，如降低能见度，减少太阳的辐射而导致城市佝偻病发病率的增加；大气污染物能腐蚀物品，影响产品质量；近十几年来，不少国家发现酸雨，雨雪中酸度增高，使河湖、土壤酸化、鱼类减少甚至灭绝，森林发育受影响，这与大气污染是有密切关系的。
大气污染对气候的影响很大，大气污染排放的污染物对局部地区和全球气候都会产生一定影响，尤其对全球气候的影响，从长远的观点看，这种影响将是很严重的。由于人类对自然的严重破坏，在世界范围内掀起了保护大气环境的浪潮。许多国家围绕大气污染物的来源与归宿，大气化学过程中的反应机理及效应进行了大量的研究工作，促进了人类对一系列环境问题的认识。
Dialogue Script 对话原文
David: The air in Beijing is seriously polluted. Look! I can even see the floating dirt overhead.
Li: Yes, air pollution in China is extremely serious, especially in cities with heavy industry.
David: Isn't there any protecting measure adopted by government for the sake of people's health?
Li: There are many. But some depurating devices are not so effective. Some effective devices are so expensive that manufacturers can't even afford.
David: That's it. Then why not consider reducing some heavy industries?
Li: Pretty hard! China is a developing country and needs heavy industries to increase it's GDP.
David: How about transferring some plants to suburbs?
Li: It's a good idea! There is a low population density in suburbs so that the harm to people is also slight. However, it brings great inconvenience.
讲解：
1. 对话中David和李平在讨论有什么办法能够缓解现在城市中的空气污染状况。David抱怨说北京空气污染真的很严重，都能看见上空飘着的浮尘。pollute是污染的意思，常用的句式就是pollute something with something，for example, Rivers are polluted with chemical waste from factories. 河流被工厂排放的化学废料污染了。
2. 如果用到比喻当中，pollute可以表示“玷污或亵渎某事物，破坏”，那么我们再来延伸一下，pollutant，污染物，pollution，pollute的名词形式，污染。
3. 李平也说中国的空气污染很严重，尤其是那些重工业城市，heavy industry，就是“重工业”，那么轻工业呢，就是“light industry”。David问难道政府没有为了人们的健康而采取措施吗？adopt表示“采取，采用”，例如：They adopted our methods. 他们采用了我们的办法。Adopt还表示“收养”，She adopted a baby girl last year. 她去年收养了一个女婴。
4. sake表示“为了…之好处, 出于对...的兴趣, 缘故, 理由”，那么由它组成的短语for the sake of something或者for one's sake，就表示“为了…好处；为…着想”，I stopped smoking for the sake of my health.为了我的健康我戒烟了。She only did that for her own sake. 她那么做只是为了她自己。
5. sake还以用来加强语气，表示迫切的请求 或不耐烦，例如：for God's sake 看在上帝的份上for Christ's sake 看在基督面上，看在老天面上，比如说，你正在专心读书准备考试，但是隔壁正在开party，你就可以大喊，For God's sake, stop making the noise! I'm trying to read!
6. 政府当然会采取措施来控制空气污染，只是很多净化空气的设备不是很有效，而很多工厂又支付不起效果显著但是非常昂贵的机器设备。afford，表示“能够提供，负担得起”，既可以指实质性的东西，比如金钱，也可以指一些抽象的东西，比如时间、感情等等，例如：I can't afford a new car. 我买不起新车。He's so busy that he can't even afford an hour for lunch. 他太忙了，甚至抽不出一小时来吃午饭。
7. David说，既然负担不起，就减少一些重工业好了，但是李平觉得这很难，因为中国是一个发展中国家，需要重工业来发展经济，GDP就是国内生产总值，gross domestic product。David又建议说或者可以把一些工厂搬到郊区，那里人口密度小，空气的污染面相对就会小一些。但是这又会带来极大的不便。
