2020年经济学人 灌溉沙漠(1)

If you live in a desert, maintaining a supply of fresh water is a challenge.

如果你生活在沙漠中，保持淡水的供应是个挑战。

One answer is desalination¹, but that needs a source of brine from which to remove the salt—

一个答案是海水淡化，但这需要一个盐水源来去除盐，

which in turn requires that your desert be near the sea. Even in inland deserts, though, moisture is often present in the air as water vapour.

因此也要求你所在的沙漠靠近大海。即便是在内陆沙漠，空气中的水分也常常以水蒸气的形式存在。

The problem is extracting this vapour effectively and cheaply. And that is what two groups of researchers—

问题是如何有效而廉价地提取这些蒸汽。这就是两组研究人员—

one at the University of Connecticut, the other at the University of California, Berkeley—hope they have managed to do.

一组来自康涅狄格大学，另一组来自伯克利加利福尼亚大学—所希望他们能够做到的。

The ease with which water can be won from air depends on that air's relative humidity.

从空气中获取水分的难易程度取决于空气的相对湿度。

This is a measure of its current vapour content as a percentage of its maximum possible vapour content at its current temperature.

这是其目前水蒸汽含量的计算方式，作为其在当前温度下最大可能蒸汽含量的百分比。

A relative humidity of 100% means the air in question is holding as much water vapour as it possibly can.

100%的相对湿度意味着空气中含有尽可能多的水蒸气。

A good way to get air to give up some of its moisture is therefore to cool it to the point where its relative humidity exceeds 100%.

因此，让空气失去一部分水分的一个好办法是将其冷却到相对湿度超过100%的程度。

Sometimes this happens naturally at night, causing mist and dew to form.

有时，夜间会自然发生这种情况，造成雾和露水的形成。

These can be collected in special traps in areas where liquid water is otherwise rare.

在液态水稀少的地区，这些水可以用特殊的捕集器收集。

But if nocturnal cooling does not bring air all the way up to 100% relative humidity,

但如果夜间降温并不能将空气的相对湿度提高到100%，

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building water traps out of special materials might give nature a helping² hand.

那么用特殊材料制造脱水器可能会给大自然带来帮助。

Adsorption is a process which plucks water molecules³ from air

吸附是将相对湿度小于100%的空气中的水分子

that has less than 100% relative humidity by attaching them to the surface of a solid material.

吸附到固体材料表面的过程。

The molecules are held there by electrostatic connections called Van der Waals forces that link them with the molecules of the pertinent⁴ surface.

分子通过一种被称为分子间作用力的静电连接与相关表面上的分子相连接而固定在那里的。

To collect a lot of water this way therefore requires a material that has two properties.

因此，用这种方法收集水需要一种具备两种特性的材料。

One is a large surface area. The other is an appropriate Van der Waals response.

一个是很大的表面积。另一个是适当的分子间作用力反应。

Experimental traps that employ this principle have been made using substances called metal-organic frameworks.

利用这一原理的实验捕集器是用一种叫做金属-有机骨架的物质制成的。

These are porous⁵ molecular⁶ networks through which air can circulate. Their porosity⁷ gives them a huge surface area.

这些是多孔的分子网络，空气可以通过它们循环。它们的多孔性使它们具有很大的表面积。

And by picking the right ingredients, such as zirconium, they can be given the necessary Van der Waals properties. Zirconium is, however, costly⁸.

通过选择正确的材料，如锆，它们可以获得必要的分子间作用力性质。但锆价格昂贵。

Moreover, once adsorbed, the water must then be released.

而且，一旦被吸附，水就必须被释放。

This means warming the adsorptive material—the warmth being provided by the sun, once it has risen.

这意味着加热吸附物质，即太阳升起后提供的热量。

Here, metal-organic frameworks present a problem. They tend to reflect sunlight rather than absorbing it, and so do not heat up well.

在此，金属-有机骨架出现了一个问题。它们更倾向于反射而不是吸收阳光，因此不能很好地加热。

To overcome this, engineers build solid "foams⁹" made of copper¹⁰ into the system.

为了克服这个问题，工程师们在系统中加入了由铜制成的固体“泡沫”。

These heat up in the sun and transfer some of their heat to parts of the adjacent metal-organic framework

它们在太阳下受热，将一部分热量传递到邻近的金属-有机骨架上，

where adsorbed water needs to be released. This works, but adding such foams makes an already costly technology even dearer.

在那里被吸附的水需要被释放出来。这种方法起了作用，但添加泡沫这种方法让本就昂贵的技术更加昂贵。

1 desalination   

n.脱盐(作用)

参考例句：

• Crops can be grown on this land after desalination. 这片土地经过脱盐就可以种植庄稼了。
• One source is by desalination-taking the salt out of salt water to make it drinkable. 淡水的来源之一是使水淡化--把含盐的水中的盐份去掉，使之能够饮用。

2 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。

3 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

4 pertinent   

adj.恰当的；贴切的；中肯的；有关的；相干的

参考例句：

• The expert made some pertinent comments on the scheme.那专家对规划提出了一些中肯的意见。
• These should guide him to pertinent questions for further study.这些将有助于他进一步研究有关问题。

5 porous   

adj.可渗透的，多孔的

参考例句：

• He added sand to the soil to make it more porous.他往土里掺沙子以提高渗水性能。
• The shell has to be slightly porous to enable oxygen to pass in.外壳不得不有些细小的孔以便能使氧气通过。

6 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

7 porosity   

n.多孔性，有孔性

参考例句：

• Commonly the dolomite crytals form a framework with evenly distributed porosity. 通常白云石晶体构成格架，它有均匀分布的孔隙。 来自辞典例句
• Seismic velocity can occasionally be affected by porosity and temperature. 孔隙率和温度有时也能影响地震波速。 来自辞典例句

8 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。

9 foams   

n.泡沫，泡沫材料( foam的名词复数 )

参考例句：

• The sea water foams under the bow. 海水在船首下面泛起浪花。 来自《现代汉英综合大词典》
• The meter handles gases, liquids, foams, and slurries. 这流量计可以处理气体，液体，泡沫状物和稀浆等。 来自辞典例句

10 copper   

n.铜；铜币；铜器；adj.铜(制)的；(紫)铜色的

参考例句：

• The students are asked to prove the purity of copper.要求学生们检验铜的纯度。
• Copper is a good medium for the conduction of heat and electricity.铜是热和电的良导体。