Atmospheric Pollution
AP Environmental Science Topic 7 8:02 English narration · English + 中文 subtitles burned in
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Transcript
Look at this city.
看看这座城市。
You cannot see the buildings, because you can see the air.
你看不见建筑，因为你能看见空气。
Now step inside a kitchen, where one cooking fire fills the room with smoke.
现在走进一间厨房，一堆炊火让屋里满是烟。
Now go far from both, into a forest no factory ever touched.
再走到离两者都很远的地方，一片从未有过工厂的森林。
The trees are dying anyway.
那里的树却在死去。
What we burn does not stay where we burn it.
我们燃烧的东西，不会留在我们燃烧的地方。
This is Unit Seven in six steps.
这就是第七单元，分六步。
First, the two kinds of pollutant.
第一，两类污染物。
Then photochemical smog, the brown haze over a sunny city.
然后是光化学烟雾，晴朗城市上空的褐色雾霾。
Then thermal inversion, the warm lid that traps it.
然后是逆温，把它困住的那层暖空气盖子。
Then carbon dioxide, particulates and indoor air.
然后是二氧化碳、颗粒物和室内空气。
Then acid rain, which falls far downwind.
然后是酸雨，它落在很远的下风处。
And last, cutting it at the source.
最后，从源头削减它。
Air pollution arrives in two ways, and the exam always checks the difference.
空气污染有两种到来的方式，考试总是考这个区别。
A primary pollutant is released already harmful.
一次污染物排出时就已经有害。
Carbon monoxide from an exhaust pipe is primary: it left the pipe as it is.
汽车尾气里的一氧化碳是一次污染物： 它离开排气管时就是这个样子。
A secondary pollutant is not emitted at all.
二次污染物根本不是被排放出来的。
It forms later, up in the air, when primary pollutants react.
它是后来在空气中，由一次污染物反应生成的。
Ground-level ozone is the classic one: nothing emits it, sunlight makes it.
近地面臭氧就是最典型的一个：没有东西排放它，是阳光造出了它。
Where does it all come from?
这一切从哪里来？
Burning fossil fuels is by far the biggest source.
燃烧化石燃料是最大的来源。
A coal power plant releases sulfur dioxide, particulate matter, toxic metals and carbon dioxide — and rising atmospheric CO2 from fossil fuels is what enhances the greenhouse effect.
燃煤电厂排放二氧化硫、颗粒物、有毒金属和二氧化碳——化石燃料带来的大气二氧化碳上升，正是增强温室效应的原因。
Vehicles release nitrogen oxides, carbon monoxide and organic compounds.
机动车排放氮氧化物、一氧化碳和有机化合物。
Burning forests release carbon dioxide and fine particles.
森林燃烧排放二氧化碳和细颗粒物。
But not every source is human.
但并不是每个来源都来自人类。
Volcanoes, wildfires, dust storms, sea spray, breathing and decay add them too.
火山、野火、沙尘暴、海浪飞沫、呼吸和分解也会产生它们。
Now that brown haze.
现在来看那层褐色雾霾。
Photochemical smog forms when pollutants bake in sunlight.
光化学烟雾在污染物被阳光烘烤时形成。
The recipe has three parts: nitrogen oxides, volatile organic compounds — VOCs — and sunlight.
配方有三样：氮氧化物、挥发性有机化合物（VOCs）和阳光。
Together they make ground-level ozone.
它们合在一起，生成近地面臭氧。
Ozone is the classic secondary pollutant, worst on hot, sunny afternoons in a traffic-filled city like this one.
臭氧是最典型的二次污染物，在炎热晴朗、车流拥堵的城市午后最严重， 就像照片里这一座。
Here is the part students miss.
这里是学生容易漏掉的一点。
Nitrogen oxides come out early, in the morning rush hour.
氮氧化物出现得早，在早高峰。
Then sunlight goes to work: ozone climbs all morning and peaks in mid-afternoon, long after the traffic has gone.
然后阳光开始起作用：臭氧整个上午不断上升，在下午中段达到最高， 那时车流早已散去。
Summer makes it worse three ways: stronger sunlight, warmer air that speeds the reaction, and trees giving off more organic compounds.
夏天让情况更糟，有三个原因： 阳光更强、空气更热使反应更快、树木释放出更多有机化合物。
And smog does real harm: sore eyes and lungs in people, slower photosynthesis in plants.
烟雾确实带来伤害：让人眼睛和肺部不适，让植物的光合作用变慢。
Now a real exam answer.
现在写一个真正的考试答案。
Why is photochemical smog worst on hot, sunny, windless afternoons in a city?
为什么光化学烟雾在城市里炎热、晴朗、无风的午后最严重？
Four sentences earn the marks.
四句话就能拿到分。
One: cars emit nitrogen oxides and organic compounds in the rush hour.
第一：汽车在早高峰排出氮氧化物和有机化合物。
Two: sunlight drives the reaction and ozone forms.
第二：阳光驱动反应，生成臭氧。
Three: heat speeds it up, so ozone peaks in the afternoon.
第三：高温加快反应，所以臭氧在下午达到最高。
Four: no wind, often an inversion, traps it.
第四：没有风，常常还有逆温，把它困住。
Remember: good ozone is high up, bad ozone is down here.
记住：好臭氧在高空，坏臭氧在我们脚下。
Why does the haze sit there for days?
雾霾为什么能一连好几天不散？
Normally air gets colder as you go up, so warm polluted air keeps rising and leaves.
正常情况下，越往上空气越冷， 所以温暖的污浊空气会一直上升、离开。
In a thermal inversion the air at the surface is cooler than the air higher up — backwards from normal.
而在逆温中，地面附近的空气比高处的空气更冷——和正常情况相反。
A warm lid sits on top, the cool air cannot rise, and the pollution cannot disperse.
暖空气盖在上面，冷空气无法上升，污染物也就无法扩散。
A valley or basin is worst of all.
山谷或盆地的情况最糟。
Step indoors, where the air is often worse than outside.
走进室内，那里的空气常常比外面更糟。
The exam splits indoor pollutants three ways.
考试把室内污染物分成三类。
Natural: radon, mould and dust.
天然来源：氡、霉菌和灰尘。
Human-made: asbestos, lead paint, and compounds from new furniture and carpet.
人造来源：石棉、含铅油漆，以及新家具和地毯释放出的化合物。
Combustion: carbon monoxide, particulates and tobacco smoke.
燃烧来源：一氧化碳、颗粒物和烟草烟雾。
Radon deserves its own line: a radioactive gas from uranium in the rock below, and the second leading cause of lung cancer.
氡值得单独一行：它是下方岩石中铀衰变产生的放射性气体，也是肺癌的第二大病因。
The fix is nearly always ventilation.
解决办法几乎总是通风。
To cut pollution, match the device to the pollutant.
要减少污染，就把装置和污染物一一对应。
That is how the marks are given.
分数正是这样给的。
Sulfur dioxide from a coal plant is stripped out by a scrubber.
燃煤电厂的二氧化硫由洗涤器脱除。
Particulates are pulled out by an electrostatic precipitator.
颗粒物由静电除尘器捕集。
In a car, carbon monoxide, nitrogen oxides and unburned fuel pass through a catalytic converter.
在汽车上，一氧化碳、氮氧化物和未燃尽的燃料要通过催化转化器。
Petrol fumes at the pump are caught by a vapor recovery nozzle.
加油时逸出的油气由油气回收加油枪捕获。
Then the rules: the Clean Air Act sets limits and cleaner fuels cut it at the root.
再看规则：《清洁空气法》设定限值，更清洁的燃料从根源上减少污染。
Look closely at that converter, because the exam likes the chemistry.
仔细看这个转化器，因为考试喜欢考它的化学过程。
Harmful gases go in: nitrogen monoxide and carbon monoxide.
有害气体进去：一氧化氮和一氧化碳。
Inside sits the catalyst, which holds them together so they react.
里面是催化剂，把它们聚在一起，使它们反应。
Harmless gases come out: nitrogen and carbon dioxide.
无害气体出来：氮气和二氧化碳。
Two pollutants gone.
两种污染物都不见了。
Acid rain starts from the same two gases.
酸雨来自同样的两种气体。
Nitrogen oxides, mostly from vehicles, dissolve straight into cloud water and make nitric acid.
氮氧化物主要来自机动车， 直接溶进云中的水里，生成硝酸。
Sulfur dioxide, mostly from coal plants, is oxidised first and then makes sulfuric acid.
二氧化硫主要来自燃煤电厂，先被氧化，然后生成硫酸。
Both acids fall as rain, snow or dry particles.
两种酸都会以雨、雪或干颗粒的形式降下来。
And notice the green arrow: nitrogen dioxide speeds the sulfur reaction up.
再注意那条绿色箭头：二氧化氮还会加快硫的反应。
Now the damage, and one word carries the marks: downwind.
现在说危害，有一个词最能拿分：下风处。
The acid falls far from the smokestack that made it, often in another country, which makes acid rain an international problem.
酸落下的地方离产生它的烟囱很远，常常是在另一个国家， 所以酸雨是一个国际性问题。
It pushes the pH of soils and lakes below four.
它把土壤和湖泊的酸碱度压到四以下。
Fish eggs fail, forests thin out, stone dissolves.
鱼卵孵不出来，森林变得稀疏，石头被溶蚀。
So we cut it at the source, with scrubbers and cleaner fuels.
所以我们要从源头削减它，用洗涤器和更清洁的燃料。
A full worked example.
一道完整的例题。
Normal rain has a pH of about five point six.
正常雨水的酸碱度大约是五点六。
A sample from a polluted valley measures three point six.
一份来自污染山谷的样品测得三点六。
How much more acidic is it?
它的酸性强了多少倍？
Step one: find the difference.
第一步：求差。
Five point six minus three point six is two pH units.
五点六减三点六等于两个单位。
Step two: the scale is logarithmic, base ten, so every unit is a ten times change.
第二步：这个标度是以十为底的对数标度，所以每一个单位就是十倍的变化。
Step three: two units is ten times ten, so the sample is one hundred times more acidic.
第三步：两个单位就是十乘以十，所以这份样品的酸性强了一百倍。
And normal rain is five point six, not seven, because carbon dioxide dissolves in it.
而正常雨水是五点六而不是七，因为二氧化碳会溶在里面。
One last pollutant you cannot see: noise.
最后一种污染物，你看不见它：噪声。
It comes from road traffic, aircraft, trains, construction and industry.
它来自道路交通、飞机、火车、建筑施工和工业。
In people, long or loud exposure causes hearing loss, stress, lost sleep and higher blood pressure.
对人来说，长期或高强度暴露会造成听力损失、压力、睡眠不足和血压升高。
In wildlife it is subtler: it masks the sounds animals use to communicate, hunt and find a mate, and it can change migration routes.
对野生动物，它的影响更隐蔽：它掩盖了动物用来交流、捕猎和求偶的声音， 还可能改变迁徙路线。
We cut it with sound barriers, quieter engines and buffer zones.
我们用隔声屏障、更安静的发动机和缓冲区来减少它。
Five marks students throw away.
五个学生常丢的分。
One: primary is released already harmful, secondary forms in the air.
第一：一次污染物排出时就有害，二次污染物在空气中形成。
Two: ground-level ozone is a pollutant, but the ozone layer high above protects us.
第二：近地面臭氧是污染物，但高空的臭氧层保护我们。
Three: in an inversion the surface air is cooler than the air above.
第三：在逆温中，地面空气比上方空气更冷。
Four: acid rain falls far downwind, which makes it an international problem.
第四：酸雨落在很远的下风处，所以它是一个国际性问题。
Five: always name the device and the pollutant it removes.
第五：一定要同时写出装置和它去除的污染物。
Four things to carry away.
带走四件事。
Pollutant types: primary is released, secondary forms in the air.
污染物的种类：一次污染物直接排放，二次污染物在空气中形成。
Smog and inversion: nitrogen oxides plus organic compounds plus sun, and a warm lid that traps them.
烟雾与逆温：氮氧化物加有机化合物加阳光，再加一层困住它们的暖空气盖子。
Acid rain: sulfur and nitrogen oxides make acids, the pH drops, life dies.
酸雨：硫和氮的氧化物生成酸，酸碱度下降，生命死亡。
And reduction: converters, scrubbers, laws, cleaner fuel.
还有削减：催化转化器、洗涤器、法律和更清洁的燃料。