托福tpo53聽力lecture2 Two Kinds of Pollution

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Two Kinds of Pollution托福聽力原文翻譯及問題答案

一、Two Kinds of Pollution托福聽力原文：

NARRATOR:Listen to part of a lecture in an environmental science class.FEMALE PROFESSOR:The Chesapeake Bay,on the east coast of the United States,is huge—the largest estuary in the U.S.—and it's very important to local economies.

But,like many of the world's waterways,the Chesapeake is being polluted;and efforts to stop that from happening have not been entirely successful.And that's partly because of the type of pollution affecting the Chesapeake…which may not be what you might predict.

Uh,first let's mention that the sources of pollution are of two general types.And let’s begin with what's known as“point source pollution”Point source pollution has an identifiable source,and you can find the specific point where,say,one particular pipe is dumping pollutants into the bay—and then treat the water right there where the pollution’s coming from.

And that's what's happened over the past 30 years or so.Modifications have been made at factories and sewage treatment plants to treat polluted water before it's released into public waterways.But there's also something we call“non-point source pollution.”

Nowadays,the most serious pollution threat doesn’t come from any particular source,like a factory or sewage treatment plant,but originates from many sources over a large area.And this non-point source pollution is a challenge to deal with,because it doesn’t just enter the bay through one pipe—you can't identify precisely where it's coming from.

And to be specific,the biggest problem now facing the Chesapeake Bay is due not to toxins,but to nutrients contained in chemical fertilizers used on farms all over the region.These nutrients—like phosphorus and especially nitrogen—wash away in what we call agricultural runoff.That’s when water from a hard rain or from melting snow carries these chemicals down to streams and into the bay,

and there they stimulate the explosive growth of algae.And that uses up much of the oxygen in the water,oxygen that fish and other aquatic organisms need to stay alive.So,since there's no single place you can treat the runoff before it reaches the bay,any efforts to reduce this non-point source pollution generally need to be aimed at keeping pollution out of the streams in the first place.

But before we go into that,let's look at the role of nitrogen fertilizer in modern farming.Until about 60 years ago,before a great increase in industrialization,this wasn’t a problem.In the past,farmers used natural fertilizers and rotated crops so that,in addition to commercial food crops,like corn and wheat,they might plant legumes,like alfalfa and clover,for animal feed.

But these legumes also enriched the soil—by converting nitrogen in the atmosphere into nitrates—a form of nitrogen the crops like wheat or corn could use as a nutrient.And,these and other“cover crops,”planted to hold the soil after the wheat or corn was harvested—they stored much of the surplus nitrogen during the time of the year when the runoff tended to be greatest.But farming practices changed as farmers came under pressure to use more and more chemical fertilizer in order to increase crop production on the same amount of land.But more isn’t always better,at least in terms of chemical fertilizer in the environment.And,along the way,farmers switched from legumes…to animal feeds more suited to intensive,large-scale animal production.

And the excess nitrogen,once trapped by these cover crops,either washed away in the next big rain or went down into the groundwater and,either way,eventually ended up in the streams and the bay.And that,as we said,means more algae in the water and less oxygen for the fish and other aquatic life to breathe.

So what’s being done?Well,two things.

First,after the main crops are harvested,more farmers are planting cover crops again—other kinds,like rye and barley—that hold the nitrogen and keep it from washing out of the soil during the months when that’s most likely to occur.And the second strategy is to plant“buffer zones”at the edges of streams—not crops,but natural areas…trees.The roots of these trees can absorb the excess nitrogen in the runoff before it reaches the streams.Farmers sometimes object to letting trees grow on land where they might otherwise be cultivating crops.But there’s a government program that compensates them,that pays them for creating these buffer zones between their fields and the streams that eventually feed into bays like the Chesapeake.And it's beginning to show some success.

二、Two Kinds of Pollution托福聽力中文翻譯：

旁白：聽一節(jié)環(huán)境科學(xué)課上的講座。女教授：切薩皮克灣位于美國東海岸，是美國最大的河口，對(duì)當(dāng)?shù)亟?jīng)濟(jì)非常重要。

但是，像世界上許多水道一樣，切薩皮克正在受到污染；阻止這種情況發(fā)生的努力并沒有完全成功。這部分是因?yàn)橛绊懬兴_皮克的污染類型……這可能不是你所能預(yù)測的。

呃，首先讓我們提到污染源有兩種類型。讓我們從所謂的“點(diǎn)源污染”開始，點(diǎn)源污染有一個(gè)可識(shí)別的來源，你可以找到一個(gè)特定的點(diǎn)，比如說，一條特定的管道將污染物傾倒到海灣中，然后在那里處理污染來源的水。

這就是過去30年左右發(fā)生的事情。工廠和污水處理廠已經(jīng)進(jìn)行了改造，以便在污水排入公共水道之前對(duì)其進(jìn)行處理。但也有一些我們稱之為“非點(diǎn)源污染”

如今，最嚴(yán)重的污染威脅并非來自工廠或污水處理廠等任何特定來源，而是來自大面積的許多來源。這種非點(diǎn)源污染是一個(gè)需要解決的挑戰(zhàn)，因?yàn)樗粌H僅是通過一條管道進(jìn)入海灣，你無法準(zhǔn)確識(shí)別它的來源。

具體來說，切薩皮克灣目前面臨的最大問題不是毒素，而是該地區(qū)農(nóng)場使用的化肥中所含的營養(yǎng)素。這些營養(yǎng)物質(zhì)，如磷，尤其是氮，在我們所稱的農(nóng)業(yè)徑流中被沖走。當(dāng)大雨或融化的雪帶來的水將這些化學(xué)物質(zhì)帶到小溪和海灣時(shí)，

在那里它們刺激藻類的爆炸性生長。這消耗了水中的大部分氧氣，魚類和其他水生生物生存所需的氧氣。因此，由于沒有一個(gè)地方可以在徑流到達(dá)海灣之前對(duì)其進(jìn)行處理，任何減少這種非點(diǎn)源污染的努力通常都需要首先將污染控制在溪流之外。

但在我們開始之前，讓我們看看氮肥在現(xiàn)代農(nóng)業(yè)中的作用。直到大約60年前，工業(yè)化大幅度增長之前，這還不是一個(gè)問題。過去，農(nóng)民使用天然肥料和輪作作物，因此除了商業(yè)糧食作物，如玉米和小麥，他們還可以種植豆類，如苜蓿和三葉草，作為動(dòng)物飼料。

但這些豆科植物也通過將大氣中的氮轉(zhuǎn)化為硝酸鹽來豐富土壤，硝酸鹽是小麥或玉米等作物可以用作養(yǎng)分的一種氮。而且，這些和其他“覆蓋作物”在小麥或玉米收獲后種植以保持土壤，它們?cè)谝荒曛袕搅髯畲蟮臅r(shí)候儲(chǔ)存了大量剩余氮。但是，隨著農(nóng)民面臨越來越多的化肥使用壓力，為了在同樣數(shù)量的土地上增加作物產(chǎn)量，農(nóng)業(yè)做法發(fā)生了變化。但更多并不總是更好的，至少在環(huán)境中的化肥方面。一路上，農(nóng)民們從豆類轉(zhuǎn)向更適合集約化、大規(guī)模動(dòng)物生產(chǎn)的動(dòng)物飼料。

而過量的氮一旦被這些覆蓋作物吸收，要么在下一場大雨中被沖走，要么流入地下水，最終流入溪流和海灣。正如我們所說，這意味著水中的藻類增多，魚類和其他水生生物呼吸的氧氣減少。

那么正在做什么？嗯，有兩件事。

首先，在主要作物收獲后，更多的農(nóng)民種植其他作物，如黑麥和大麥，這些作物可以保持氮，并在最有可能發(fā)生氮流失的月份防止氮從土壤中沖走。第二個(gè)策略是在溪流邊緣種植“緩沖區(qū)”，而不是作物，而是自然區(qū)域……樹木。這些樹的根部可以在徑流到達(dá)溪流之前吸收多余的氮。農(nóng)民有時(shí)反對(duì)讓樹木生長在他們可能種植作物的土地上。但有一項(xiàng)政府計(jì)劃對(duì)他們進(jìn)行補(bǔ)償，為他們?cè)谔锏睾秃恿髦g建立緩沖區(qū)，最終流入切薩皮克灣等海灣提供資金。它開始顯示出一些成功。

三、Two Kinds of Pollution托福聽力問題：

Q1:1.What is the lecture mainly about?

A.The difference between point source and nonpoint source pollution

B.The source and treatment of a serious type of pollution affecting the Chesapeake Bay

C.The causes for the large decrease in algae in the Chesapeake Bay

D.The development of farming methods during the past century

Q2:2.What is one of the reasons that the professor mentions pollution that comes from a pipe?

A.To compare point source pollution with nonpoint source pollution

B.To blame factories and sewage treatment plants for producing most water pollution

C.To demonstrate that agricultural runoff is a point source pollutant

D.To suggest new methods that may someday begin to reduce water pollution

Q3:3.According to the professor,why has it been difficult for fish and many other organisms to live in the Chesapeake Bay?

A.Toxic chemicals in the water have poisoned many of them.

B.Runoff from farmland has made the water very muddy.

C.Water flow from streams has been unreliable.

D.Oxygen levels in the water have been reduced.

Q4:4.What is the professor's attitude about the use of chemical fertilizer?

A.She is surprised that some farmers have stopped using it.

B.She is convinced that its use should be increased substantially.

C.She worries that farmers may be using too much of it.

D.She regrets that it was not more useful for increasing crop production.

Q5:5.What two practices does the professor suggest for reducing the amount of nitrogen that enters a bay such as the Chesapeake?[Click on 2 answers]

A.Planting trees along the sides of streams

B.Building water treatment facilities where streams enter the bay

C.Planting cover crops that take up excess nitrogen in the soil

D.Letting farm animals graze in areas near streams and the bay

6.According to the professor,why were farmers reluctant to create buffer zones near streams?

A.They were not convinced that buffer zones effectively control pollution.

B.They feared that creating buffer zones might decrease farm income.

C.Government approval for creating buffer zones was at first difficult to obtain.

D.Planting trees was much more expensive than planting the usual crops.

四、Two Kinds of Pollution托福聽力答案：

A1:正確答案：B

A2:正確答案：A

A3:正確答案：D

A4:正確答案：C

A5:正確答案：AC

A6:正確答案：B

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