『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 44 Lec 4听力练习：What is the main purpose of the talk?原文题目答案解析，TPO/Official 44 Lec 4听力原文范文音频翻译。

托福TPO/Official 44 Lec 4听力原文What is the main purpose of the talk?【新东方在线】

旁白：请听一段环境科学的讲座。

Narrator: Listen to part of a lecture in an environmental science class.

教授：现在，人们对利用可再生能源发电越来越有兴趣，对吧？

Professor: Now, there is growing interest these days in generating electricity from renewable energy sources, right?

从开发风电场到开采地热能，可见一斑。

From developing wind farms to tapping into an underground source of geothermal energy.

考虑一个新项目时，既要考虑开发该能源的好处，又要考虑成本，这两者都很重要。

And when you're considering a new project, it's important to look at the costs as well as benefits of developing that energy source.

Let me give you an example of the kind of thing I am talking about.

目前人们对利用海洋的力量有浓厚的兴趣，也就是能引发海洋的水位上升和下降的海洋潮汐。

There is currently a lot of interest in harnessing the power of the oceans, of the ocean tides, that is, the movement of huge amounts of water which causes the water level of oceans to rise and fall.

其理念是，如果我们可以利用这种潮汐能，那将是一种很好的清洁可再生能源。

The idea is that if we can harness that tidal energy, it'd be a great clean renewable energy source.

而可以利用潮汐能的一个地方是浅水区，比如入海口。

One place where this tidal energy can be harnessed is at a shallow body of water, such as an estuary.

Now, can anyone tell us what an estuary is?

学生：入海口是河流流入海洋的地方。

Student: An estuary is where a river enters the ocean.

教授：由于潮汐的涨落，入海口的某些部分确实会这样，但还有一部分一直是淹没在水中的。

Professor: Some parts of the estuary, as the tides go in and out, but other parts are always submerged.

入海口是试图从潮汐变化中获取能量的理想场所，因为在高潮和低潮时水位有非常大的差异。

Now, estuaries are an ideal place to try to capture energy from changes in tides because, well, there is an exceptionally large difference between the water level at high tide and at low tide.

这些大量的水的运动会产生巨大能量。

All that movement of water generates a lot of energy.

而利用这种能量的一种方法是建拦河坝。

And one way to harness that energy is by building a structure called a barrage there.

拦河坝就是一个建在入河口的大型低坝。

A barrage is basically a large low dam that's built across an estuary.

当潮汐涨涨落落时，水会流过拦河坝中的隧道。

When the tides go in and out, the moving water flows through tunnels in the barrage.

因此，当大量的水要流经这些较窄小的隧道时，就能带动涡轮机发电。

So you have huge amounts of water trying to flow through these relatively small tunnels and that turns turbines that generate electricity.

这些入海口很重要，因为它们有很高的生物生产力。

Now, these estuaries are important because of their high level of biological productivity.

它们是很多鸟类、鱼类和其他海洋生物的家。

They are home to lots of birds, fish and other marine life.

因此要建拦河坝时，需要考虑的很多问题。

So when you propose to construct a barrage, you have lots of issues to consider.

例如，拦河坝的建设会改变入海口现有的水位。

For example, it would change the existing water levels in the estuary.

由于拦河坝拦截了大量的水，即将来临的潮汐不会涨很高，但落潮时，也不会很低。

Since a lot of water is getting held up by the barrage, the incoming tides won't go as high, but they wouldn't be as low during low tide, either.

但也会影响到泥滩，泥滩是潮水退去后露出的淤泥地带。

But it would also affect the mudflats, those areas of mud that normally are exposed when the tide recedes.

学生：但是，不是大量的鸟要依赖露出的泥滩提供食物吗？

Student: But don't lots of birds rely on exposed mudflats for food?

我是说，它们不吃泥田中的小动物吗？

I mean, don't they eat tiny animals that live in the mud?

如果泥滩受到威胁，会有什么事发生到它们身上？

What would happen to them if the mudflats were endangered?

教授：所以你看到了拦河坝的一些潜在问题。

Professor: So you are seeing some of the potential problems with the barrage.

但是想想另一面吧，现在入海口的水是浑浊的。

But consider this, right now, the water in an estuary is very cloudy.

潮汐流不断搅动着河流入海口沉积的沉淀物。

The tidal currents are constantly churning up the sediments that rivers deposit in the estuary.

But a barrage would reduce the tidal currents.

所以很多沉淀物会沉积到入海口的海底。

So a lot of that sediment would settle to the floor of the estuary.

水会更清澈，能更多的阳光能到达更深的水中，这可能会为鸟类和其他动物带来更多的食物，也会吸引新的野生动物到该地区来。

The water would be clearer, allowing more sunlight to reach deeper into the water, which might lead to more food for birds and other animals, attracting new wildlife to the area.

因此，这是一个复杂的环境问题。

So it's a complicated environmental picture.

教授：建过，有几个拦河坝正在使用中。

Professor: Yes, there are several in operation.

拦河坝工作人员需要小心翼翼地使用涡轮机，因为涡轮机推动的水流和波浪会影响船只。

Now, they have to be careful there about how they turn on the turbines because they create currents and waves that can affect boats.

但目前我还没有看到任何重大的生态问题。

But I haven't read about any major ecological problems.

事实上，捕鱼业应该有所改善。

In fact, the fishing is supposed to have improved.

而且现在有更多的鸟生活在泥滩。

但是有些将要建设的拦河坝比我们现在讨论的要大很多。

But some of the barrages we're considering now would be much larger than that one.

有人提议在世界上最大的入海口之一——英国塞文河入海口（建一个）。

There has been one proposed for the estuary of Great Britain's Severn River, one of the largest estuaries in the world.

就想一下吧，法国的拦河坝还不到1千米。

Just to give you an idea, the barrage in France is less than a kilometer.

除了环境方面的考虑，这样一个工程，额，也就是这么大的，一定耗资巨大，这也是反对拦河坝的又一理由。

Outside of environmental concerns, such a project would be hugely expensive and that's another argument against barrages, well, such large ones anyway.

反对者认为，这笔钱最好用于其他方面，例如用来提高建筑物的能效。

Critics say that it would better to use that money for something else, such as improving the energy efficiency of buildings.

用这些钱，你可以让很多建筑更加高效，从而减少对电力的需求。

You could make a lot of buildings more efficient with all that money and that would reduce the need for electricity.

What does the professor say about estuaries to support the claim that they are appropriate places for building barrages?

What is the professor's opinion when the man expresses concern about marine life on the mud flats?

The professor mentions a change in the quantity of fish caught near a barrage in France. What most likely happened to the water in the estuary as a result of the construction of the barrage?

What does the professor say is a criticism of the proposed barrage at the Severn River in Great Britain?

Listen to part of a lecture in an environmental science class
Professor 
Now, there is growing interest these days in generating electricity from renewable energy sources, right? From developing wind farms to tapping into an underground source of geothermal energy. And when you’re considering a new project, it’s important to look at the costs as well as benefits of developing that energy source. Let me give you an example of the kind of thing I’m talking about.
There is currently a lot of interest in harnessing the power of the oceans, of the ocean tides that is, the movement of huge amounts of water which causes the water level of oceans to rise and fall. The idea is that if we can harness that tidal energy, it will be a great clean renewable energy source. One place for this tidal energy can be harnessed is that a shallow body of water, such as the estuary. Now, can anyone tell us what an estuary is? Yes, Ted?
Student 
An estuary is where a river enters the ocean, and the freshwater meets the ocean water. Sometimes it’s covered in water, sometimes it’s not.
Professor 
Some parts of the estuary, as the tides go in and out, but other parts are always submerged. Now estuaries are an ideal place to try to capture energy from changes in tides, because, well, there is an exceptionally large difference between the water level of high tide and low tide. All that movement of water generates a lot of energy and one way to harness that energy is by building a structure called a barrage there.
A barrage is basically a large low damn that is built across an estuary. When the tides go in and out, the moving water flows through tunnels in the barrage. So you have huge amounts of water trying to flow through these relatively small tunnels, and that turns turbines that generate electricity. Now these estuaries are important because of their high level of biological productivity. They are home to lots of birds, fish and other marine life. So when you propose to construct a barrage, you have lots of issues to consider. For example, it would change the existing water levels in the estuary, since a lot of water is getting held up by the barrage. The incoming tides won’t go as high. But they wouldn’t be as low during low tide either. This might help prevent flooding, but it would also affect the mud flats, those areas of mud that normally are exposed when the tide recedes.
Student 
But don’t lots of birds rely on exposed mud flats for flood? I mean though they eat tiny animals that live in the mud and what about these tiny animals? What would happen to them if the mud flats were endangered?
Professor 
So you were saying some of the potential problems with the barrage. But consider this. Right now the water in estuaries is very cloudy; the tidal currents are constantly transporting the sediments that rivers deposit in the estuary. But a barrage would reduce the tidal currents, so a lot of that sediments would settle to the floor of estuary. It wouldn’t get stirred up so much. The water would be clear, allowing more sunlight to reach deeper into the water, which might lead to more food for birds and other animals, attracting new wildlife to the area. So it’s a complicated environmental picture.
Student 
How they try the weir, the old of a barrage?
Professor 
Yes. There are several in operations. There is one in France. And they have to be careful there about how they turn on the turbines, because they create currents and waves that can affect boats. But I haven’t read about any major ecological problems. In fact, the fishing is supposed to be improved, supporting even more birdlife. But some of the barrages we’re considering now would be much larger than that one. There’s been one propose for the estuary of Great Britain Severn River, one of the largest estuaries in the world. It would be 16km long. Just to give you an idea, the barrage in France is less than a kilometer. Outside the environmental concerns, such a project would be hugely expensive and that’s another argument against barrages, well, such large ones anyway. Critics say that it would be better to use that money for something else, such as improving the energy efficiency of buildings. You can make a lot of buildings more efficient with all that money, and that would reduce the need for electricity.

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