学位英语

A Strong Greenhouse Gas

1.Methane is a colorless, odorless gas; it is also a potent greenhouse gas, and once released into the atmosphere, it absorbs heat radiating from Earth’s surface. That’s why methane is a major contributor to the planet’s increasing temperature rise—or global warming. Molecule for molecule, methane’s heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide, the most abundant greenhouse gas.

2.With 13 billion cows belching almost constantly around the world (100 million in the U.S. alone), it’s no surprise that methane released by livestock is one of the chief global sources of the gas. Other prime methane sources: petroleum, drilling, coal mining, solid-waste landfills and wetlands.

3.Greenhouse gases like methane and carbon dioxide make up only a small part of Earth’s atmosphere, which is 78 percent nitrogen and nearly 21 percent oxygen. And without greenhouse gases to trap the sun’s heat and warm the planet, life was we know it couldn’t exist. But in the last 200 years, human activity that requires burning oil, natural gas, and coal for energy has magnified the greenhouse effect.

4.Atmospheric concentrations of methane have more than doubled in the last two centuries. Blame for this often focuses on big industries and gas-guzzling vehicles. But agriculture plays a major role, too. In the past 40 years alone, the global cattle population has doubled.

5.Cows munch mostly grasses and hay—yet they grow big and hefty. Why? Because of the rumen. The rumen holds 160 liters of food and billions of microbes. These microscopic bacteria and protozoa break down cellulose and fiber into digestible nutrients. A cow couldn’t live without its microbes. As the microbes digest cellulose, they release methane. The process occurs in all animals with a rumen (cows, sheep, and goats, for example), and it makes them very gassy. It’s part of their normal digestion process. When they chew their cud, they regurgitate some food to rechew it, and all this gas comes out. the average cow expels 600 liters of methane a day.

6.That’s why we say livestock gas is also a major factor of causing the global warming.

词汇：

methane 甲烷 munch 用力咀嚼

odorless 无味的 hefty 健壮的

potent 强有力的 rumen 瘤胃

belch 打嗝 protozoa 原生动物(复数)

livestock 家畜，牲畜 cellulose 纤维素

landfill 埋填的废渣 nutrient 有营养的

magnify 扩大 cud 反刍的食物

guzzle 大量消耗(燃料等) regurgitate 反刍

注释：

1.once released into the atmosphere…：一旦(甲烷)释放到大气中……once released into the atmosphere相当于once methane is released into the atmosphere。

2.Molecule for molecule，molecule's heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide…：按分子与分子对比，甲烷在大气中吸热的能力比二氧化碳强20倍……介词for表示“对比或比例关系”。

3.without greenhouse gases…life as we know it could'n't exist：没有温室气体……我们所知道的生命就不能生存。本句中，life是主语。as从句中的it指代life。

4.Atmospheric concentrations of methane：甲烷在大气中的浓度。

练习：

1.Paragraph 1 _____

2.Paragraph 2 _____

3.Paragraph 4 _____

4.Paragraph 5 _____

A. Life of Microscopic Bacteria in Livestock’s Rumen

B. Ways to Reduce Methane’s Heat-trapping Power

C. Agriculture Also Contributes to Increased Concentrations of Methane in the Atmosphere

D. Why Livestock Releases Methane

E. Methane as a Strong Greenhouse Gas

F. Livestock as a Prime Factor of the Greenhouse Effect

5.Methane is ___________ to the intensifying greenhouse effect.

6.Greenhouse gases are indispensable to mankind, but the problem mankind is faced with is ___________.

7.Generally people heap criticism on __________ for the planet’s temperature rise.

8.Nothing has been mentioned in the passage about __________.

A one of the major contributors

B the ever-increasing atmospheric concentrations of greenhouse gases

C big and hefty cows

D livestock’s normal digestion process

E how to cut down the cattle populations

F big industries and gas-guzzling vehicles

答案与题解 :

1. E本段的第三句点出了 methane’s heat-trapping power in the atmosphere is 21 times stronger than carbon dioxide。

2. F 本段要表达的中心意思是： livestock排出的甲烷也是温室效应的一个主要源头。

3. C本段表达的重点是用 but转折的段后两句。

4. D 本段从科学的角度分析反刍动物为什么会释放出甲烷。

5. A 选 A的依据在第一段的第二句和昀后一句。

6.B 选 B的依据在第三段的第二句、第三句和第四段的第一句。这三个句子先后介绍了下列观点：没有温室气体，生物不能生存;人类燃烧能源，加剧温室效应;大气甲烷含量增加一倍。

7. F 第四段第二句直接谈到这个问题。人们常常将不断加剧的温室效应归罪于大工业和汽车，而 cattle释放甲烷的因素被忽略了。

8. E 选项 E是本文没有提到的内容，也就是说，其他五个选项的内容文章部有涉及。

译文：一种强烈的温室气体

甲烷是一种无色无味的气体，同时也是一种很强烈的温室气体，一旦释放到空气中，就会吸收地球表面散发的热量。所以说甲烷是使这个星球日趋变暖 (或叫全球变暖 )的一个主要原因。按分子与分子对比，甲烷在大气中吸收热量的能力是二氧化碳——最丰富的温室气体的 21倍。

由于全世界有 130亿头牛几乎在连续不断地打嗝(仅美国就有一亿头)，难怪由牲畜释放的甲烷就成为了一种主要的全球性甲烷来源。其他主要的甲烷来源有：石油、钻井、采煤、固体垃圾以及沼泽地。

甲烷和二氧化碳等温室气体只占地球大气的一小部分，大气中 78%为氮气，将近 21%为氧气。如果没有温室气体来吸收太阳的热量，使地球变暖，我们所知道的生命就不会存在。但在过去的 200年里，通过燃烧油、天然气和煤来获取能量的人类活动加剧了温室效应。

在过去的两个世纪里，甲烷在大气中的浓度地加了一倍多，人们常常将此归罪于大工业和汽车。但是农业在其中也扮演了一个重要角色。仅在过去 40年里，全球牲畜数量就翻了一番。

牛吃的大部分是草，但却长得身高体壮。原因何在?在于它们都长有瘤胃。它们的瘤胃容纳160升的食物，养育数十亿的微生物。这些微小的细菌和原生动物可分解纤维素，形成可吸收的营养。没有这些微生物牛就无法生存。由于微生物可吸收纤维素，所以就会释放出甲烷。所有长有瘤胃的动物(比如牛、绵羊和山羊)都会这样，因此它们经常释放出气体。这是它们的正常吸收过程的一部分。它们反刍时，就会将食物重新咀嚼，于是就释放出气体。一般每头牛每天会排出600升甲烷。

因此，我们认为，牲畜释放的气体也是全球变暖的一个主要因素。

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