1、Environmental PollutionWith the coming of the Industrial Revolution the environment pollution increased alarmingly. Pollution can be defined as an undesirable change in the physical, chemical, or biological characteristics of the air, water, or land that can harmfully affect health, survival, or act
2、ivities of humans or other living organisms. There are four major forms of pollution-waster on land, water pollution (both the sea and inland waters),and pollution by noise.Land can be pollution by many materials. There are two major types of pollutants: degradable and nondegradable. Example of degr
3、adable pollutions are DDT and radioactive material. DDT can decompose slowly but eventually are either broken down completely or reduced to harmless levels. For example, it typically takes about 4 years for DDT in soil to be decompose to 25 percent of the original level applied. Some radioactive mat
4、erials that give off harmful radiation, such as iodine131, decay to harmless pollution. Other, such as plutonium239 produced by nuclear power plants, remains at harmful levels for thousands to hundreds of thousands of year.Nondegradable pollutions are not broken down by natural processes. Examples o
5、f nondegradable pollutants are mercury, lead and some of their compounds and some plastics. Nondegradable pollutants must be either prevented from enter the air, water, and soil or kept below harmful level by removal from the environment. Water pollution is found in many forms. It is contamination o
6、f water with city sewage and factory wastes; the runoff of fertiliser and manure from farms and feed lots; sudsy streams; sediment washed from the land as a result of storms, farming, construction and mining; radioactive discharge from nuclear power plants; heated water from power and industrial pla
7、nts; plastic globules floating in the worlds oceans; and female sex hormones entering water supplies through the urine of women taking birth control pills.Even though scientists have developed highly sensitive measuring instruments, determining water quality is very difficult. There are a large numb
8、er of interacting chemicals in water, many of them only in trace amounts. About 30000 chemicals are now in commercial production, and each year about 1000 new chemicals are added. Sooner or later most chemicals end up in rivers, lakes, and oceans. In addition, different organisms have different rang
9、es of tolerance and threshold levels for various pollutants. To complicate matters even further, while some pollutants are either diluted to harmless levels in water or broken down to harmless forms by decomposers and natural processes, others such as DDT, some radioactive materials, and some mercur
10、y compounds) are biologically concentrated in various organisms.Air pollution is normally defined as air that contains one or more chemicals in high enough concentrations to harm humans, other animals, vegetation, or materials. There are two major types of air pollutants. A primary air pollutant is
11、a chemical added directly to the air that occurs in a harmful concentration. It can be a natural air component, such as carbon dioxide, that rises above its normal concentration, or something not usually found in the air, such as a lead compound. A secondary air pollutant is a harmful chemical forme
12、d in the atmosphere through a chemical reaction among air components. We normally associate air pollution with smokestacks and cars, but volcanoes, forest fires, dust storms, marshes, oceans, and plants also add to the air chemicals we consider pollutants. Since these natural inputs are usually wide
13、ly dispersed throughout the world, they normally dont build up to harmful levels. And when they do, as in the case of volcanic eruptions, they are usually taken care of by natural weather and chemical cycles.As more people live closer together, and as they use machines to produce leisure, they find
14、that their leisure, and even their working hours, become spoilt by a byproduct of their machine-namely, noise. The technical difficulties to control noise often arise from the subjective-objective nature of the problem. You can define the excessive speed of a motor-car in terms of a pointer reading
15、on a speedometer. But can you define excessive noise in the same way? You find that with any existing simple “noise-meter”, vehicles which are judged to be equally noisy may show considerable difference on the matter. Though the ideal cure for noise is to stop it at its source, this may in many case
16、s be impossible. The next remedy is to absorb it on its way to the ear. It is true that the overwhelming majority of noise problems are best resolved by effecting a reduction in the sound pressure level at the receiver. Soft taped music in restaurants tends to mask the clatter of crockery and the co
17、nversation at the next table. Fan noise has been used in telephone booths to mask speech interference from abjacent booths. Usually, the problem is how to reduce the sound pressure level, either at source or on the transmission path.环境污染随着工业革命的到来，环境污染剧增。污染可以被定义为一个在空气，水和土地的方面的不良变化，这种变化会严重影响人或其它生物有机体的
18、健康，生存，或活动。主要有四种形式的污染浪费土地，水污染（包括海洋和内陆水域） ，和噪音污染。土地可以被很多材料污染。其中有两种主要类型的污染物：可降解和不可降解的。可降解的污染物如 DDT 和放射性物质。 DDT 能缓慢分解但最终要么彻底破裂，要么减少到无害的水平。例如，它通常需要大约 4 年才能分解到 25%原级应用。一些释放有害辐射的放射性物质，如碘 131，能够衰变为无害的污染物。其他的，如核电厂产生的钚239，仍然能够对环境危害成千上万年。不可降解的污染物不能通过自然过程分解。如汞铅及其化合物和一些塑料。必须阻止不可降解的污染物进入空气，水，土壤中或使它们保持在低的有害水平而从环境移
19、除。水体污染有多种形式。它包括城市污水和工业废水；径流化肥和从农场和饲养场排放的有机肥；起泡沫的溪流；由于暴雨，农业，建筑和采矿而从土地上冲积下来的沉积物；从核电厂排放出的放射性物质；电厂和工厂排放的热水；漂浮在世界海洋上的塑料球；和通过服用避孕药的妇女的尿液进入供水系统的女性性激素。虽然科学家们已开发了高灵敏度的测量仪器，但是确定水的质量仍然非常困难。在水中有大量相互作用的化学品，他们中的许多只是微量的。目前约 30000 的化学品在商业化生产，并且每年会新增加大约 1000 种化学品。早晚大多数化学物质会被排放到河流，湖泊和海洋中。此外，不同的生物对各种污染物有不同的耐受范围和阈值水平。更
20、加复杂化的是，虽然一些污染物在水中被稀释到无害的水平或通过分解器和自然过程分解成无害的形式，但是其他的污染物（如 DDT，一些放射性物质，和汞化合物）却在各种生物体内不断积累。空气污染通常被定义为：空气中含有一个或更多浓度高到足以伤害人类，其他动物，植物，或材料的化学品。主要有两种类型的空气污染物。一种主要的空气污染物是一种以有害浓度直接添加到空气中化学品。它可以是一种自然的空气成分，如高于正常浓度的二氧化碳，也可以是空气中不常见的，如铅的化合物。二次空气污染是一种在大气中通过空气成分之间的化学反应形成的有害化学物质。我们通常把空气污染与烟囱和汽车联系在一起，但火山，森林火灾，沙尘暴，沼泽，海
21、洋，工厂也会带来我们认为会污染空气的化学物质。因为这些自然输入通常是广泛分布在整个世界，所以它们通常不增加空气的有害水平。当它们发生的时候，如火山爆发，它们通常被自然气候和化学循环消弱对空气的影响。随着越来越多的人生活更紧密，以及越来越多的人通过机器打发时间，他们发现他们的闲暇时间，甚至他们的工作时间，都充斥着机器的副产品即噪声。控制噪音的技术难点往往产生于主客体性质的问题。你可以依据速度表上指针的读数来定义一辆机动车的超速，但你可以用相同的方式来定义过度噪声吗？你会发现使用任何已有的简单的噪声调试器，在同样嘈杂的情况下，对这个问题车辆会出现相当大的差异。虽然理想的治疗噪声的方法是停止它的来源，但是这在很多情况下是不可能的。另一个治疗方法是在噪音传到人耳朵的过程中吸收它。的确，绝大多数的噪音问题最好的解决办法是减小接受者听到的声压级。餐厅里的轻音乐可以掩盖陶器的碰撞声和邻桌的交谈声。电话亭里风扇的噪音可用来掩盖来自隔壁电话亭的语音干扰。通常，噪声问题的解决办法就是在其生源处或是在其传播途中降低其声压水平。
