Part 5 Water Pollution 水污染

Comprising over 70% of the Earth's surface, water is undoubtedly the most precious natural resource that exists on our planet. Without the seemingly unvaluable compound comprised of hydrogen and oxygen, life on Earth would be non-existent: it is essential for everything on our planet to grow and prosper. Although we as humans recognize this fact, we disregard it by polluting our rivers, lakes, and oceans. Subsequently, we are slowly but surely harming our planet to the point where organisms are dying at a very alarming rate.

Water pollution occurs when a body of water is adversely affected due to the addition of large amounts of materials to the water. The sources of water pollution are categorized as being a point source or a non-source point of pollution. Point sources of pollution occur when the polluting substance is emitted directly into the waterway. A pipe spewing toxic chemicals directly into a river is an example. A non-point source occurs when there is runoff of pollutants into a waterway, for instance when fertilizer from a field is carried into a stream by surface runoff.

There are several types of water pollution. A toxic substance is a chemical pollutant that is not a naturally occurring substance in aquatic ecosystems. The greatest contributors to toxic pollution are herbicides, pesticides and industrial compounds.

Organic pollution occurs when an excess of organic matter, such as manure or sewage, enters the water. When organic matter increases in a pond, the number of decomposers will increase. These decomposers grow rapidly and use a great deal of oxygen during their growth. This leads to a depletion of oxygen as the decomposition process occurs. A lack of oxygen can kill aquatic organisms. As the aquatic organisms die, they are broken down by decomposers which leads to further depletion of the oxygen levels.

Thermal pollution can occur when water is used as a coolant near a power or industrial plant and then is returned to the aquatic environment at a higher temperature than it was originally. Thermal pollution can lead to a decrease in the dissolved oxygen level in the water while also increasing the biological demand of aquatic organisms for oxygen.

Ecological pollution takes place when chemical pollution, organic pollution or thermal pollution are caused by nature rather than by human activity. An example of ecological pollution would be an increased rate of siltation of a waterway after a landslide which would increase the amount of sediments in runoff water. Another example would be when a large animal, such as a deer, drowns in a flood and a large amount of organic material is added to the water as a result. Major geological events such as a volcano eruption might also be sources of ecological pollution. And this is just one of the biggest problems facing the countries now which were hit by tsunami in December last year.

There are many sources of water pollutants.Farms often use large amounts of herbicides and pesticides, both of which are toxic pollutants. These substances are particularly dangerous to life in rivers, streams and lakes, where toxic substances can build up over a period of time. Farms also frequently use large amounts of chemical fertilizers that are washed into the waterways and damage the water supply and the life within it.

Waste and sewage generated by industry can get into the water supply, introducing large organic pollutants into the ecosystem. Many industrial and power plants use rivers, streams and lakes to despose of waste heat. The resulting hot water can cause thermal pollution. Thermal pollution can have a disasterous effect on life in an aquatic ecosystem as temperature increaces decreace the amount of oxygen in the water, thereby reducing the number of animals that can survive there.

Water can become contaminated with toxic or radioactive materials from industry, mine sites and abandoned hazardous waste sites. Acid precipitation is caused when the burning of fossil fuels emits sulfur dioxide into the atmosphere. The sulfur dioxide reacts with the water in the atmosphere, creating rainfall which contains sulfuric acid. As acid precipitation falls into lakes, streams and ponds it can lower the overall pH of the waterway, killing vital plant life, thereby affecting the whole food chain.

Sewage generated by houses or runoff from septic tanks into nearby waterways, introduce organic pollutants that can cause eutrophication. Fertilizers, herbicides and pesticides used for lawn care can runoff and contaminate the waterway. As with agriculteral fertilizers, home fertilizers can lead to the eutrophication of lakes and rivers.

Improper disposal of hazardous chemicals down the drain itroduce toxic materials into to the ecosystem, contaminating the water supplies in a way that can harm aquatic organisms. Leaks of oil and antifreeze from a car on a driveway can be washed off by the rain into nearby waterways, polluting it.

Clearly, the problems associated with water pollution have the capabilities to disrupt life on our planet to a great extent. In order to combat water pollution, we must understand the problems and becomepart of the solution.

As we head into the 21st century, awareness and education will most assuredly continue to be the two most important ways to prevent water pollution. If these measures are not taken and water pollution continues, life on earth will suffer severely.

水體因某種物質的介入，而導致其化學、物理、生物或者放射性等方面特征的改變，從而影響水的有效利用，危害人體健康或者破壞生態環境，造成水質惡化的現象稱為水污染。

水污染物源于很多的人類活動。工業污染物可從工廠中的排泄管流出，或者可從管道和地下儲存罐中外泄。受污染的水也可能是從礦山流出，而流經礦山的水通過含礦物的巖石的瀝濾，或已受到加工礦石的化學制品的污染。

城市和其他居民區的水污染大多源自下水道中混有的微量家庭化學制品。有時工廠將污染物排泄到城市的污水系統中，使城區各種污染物質增多。來自于像農田。牧草場、飼育場和大農場等農業源頭的污染物有動物糞便、農業化學制品以及腐蝕過程中產生的沉淀物。

人類的活動會使大量的工業、農業和生活廢棄物排入水中，使水受到污染。目前，全世界每年約有4200多億立方米的污水排入江河湖海，污染了5.5萬億立方米的淡水，這相當于全球徑流總量的14%以上。

水污染有兩類：一類是自然污染；另一類是人為污染。當前對水體危害較大的是人為污染。水污染可根據污染雜質的不同而主要分為化學性污染、物理性污染和生物性污染三大類

在發展工業，建設城市的同時，就要注意到水資源的保護。因為一旦水資源受到污染，將嚴重的制約工業、農業的發展以及人類的生存。

Dialogue Script 對話原文

Sarah: The more I learn about the world around me, the more aware I become of the problems facing us.
Bob: Do you mean the problems here in China?
Sarah: Yes, here and all over the world.
Bob: Well, there's one problem I'm certainly aware of and that is the environmental pollution all around us.
Sarah: That is one of the great problems, but in many parts of the world, as people become more aware and apply new technology to solving the pollution problem; there is hope for the future.
Bob: What technology will help with pollution control?
Sarah: Well, for example, I've recently read an article about using certain types of bacteria to help control some pollution problems.
Bob: How could that be? I thought bacteria just caused illness.
Sarah: That's not true. Bacteriologists have identified certain strains of bacteria that "eat" petroleum products, such as oil and gasoline.
Bob: That sounds strange. How does it work?
Sarah: They ingest the petroleum and excrete hydrogen and oxygen, leaving a clean environment behind them.
Bob: Could they use that little bug to clean up big oil spills?
Sarah: Yes, as a matter of fact, they are being proven to be the most successful method of cleaning up after land-based oil spills and are useful for marine spills.
Bob: Wow! Are there other types of pollution that those microbes like to eat?
Sarah: Sure, bacteria have been used to remove arsenic from the sludge produced by gold mining operations. There are seven experiments being done now to reduce nuclear waste to a harmless residue.
Bob: Maybe those bacteria that we used to worry about will eventually save the world!

講解：

1. 對話中Sarah 和Bob在為世界的環境污染狀況擔憂。Sarah說The more I learn about the world around me, the more aware I become of the problems facing us. 這里我們又看到了the more…, the more…這個句式，就是兩個比較級形式重疊起來，表示“越…就…”，在以前的實用英語課堂中我們提到過。后面的句子，the more aware I become of the problems facing us. 把順序調整過來就是I become more aware of the problems facing us. 一定要注意這個句式中的語序，別丟三落四的。這里就不能丟掉這個of，因為of是be /become aware of 這個短語的重要組成部分。

2. be /become aware of表示“知道，了解”，相當于know，只不過感覺上要更正式一些。例如：I was not aware of President's being here.我不知道總統先生在這。

3. 環境污染是全世界共同關心的問題，而不僅僅是中國。但是Sarah相信，隨著人們對環境污染的認識越來越清醒，并使用新的技術解決污染問題，未來還是大有希望的。那么有哪些技術能有利于環境污染的治理呢？真是太多了，比如，Sarah在這里就提到了一種細菌，就是“bacteria”，能夠控制污染。

4. Bob問細菌不是導致疾病的嗎？其實并不是所有的細菌都能導致疾病的。細菌學家已經發現，某些種類的細菌能夠“吃掉”石油產品，例如機油和汽油。這些細菌把汽油等石油產品吃下肚，然后排出氫氣和氧氣，從而使周圍的環境變得清潔。這些細菌可以用來清除大片泄漏的油污。事實上，這樣的細菌已經被證明是清除陸地上泄漏油污的最成功的方法，對清除海洋泄漏油污也很有效果。他們還可以被用來清除金礦開采所產生的污泥中的砷。有人還在進行試驗，把核廢料轉化成無害物。說不定我們以前害怕的細菌最終能拯救世界呢。