The science of smog - Kim Preshoff

譯者: Cadence Chen 審譯者: 瑞文Eleven 林Lim

On July 26, 1943,

1943 年 7 月 26 日

Los Angeles was blanketed by a thick gas that stung people's eyes

洛杉磯被一層濃厚的氣體壟罩著

刺激人們的眼睛，也遮住了太陽

and blocked out the Sun.

Panicked residents believed their city had been attacked using chemical warfare.

驚慌的居民們相信他們的城市 遭受到化學戰爭攻擊

But the cloud wasn't an act of war.

但這雲層並非由戰爭引起

It was smog.

而是煙霧 (smog)

A portmanteau of smoke and fog,

一種含有煙與霧的混合物

the word "smog" was coined at the beginning of the 20th century

煙霧一名詞出現在 20 世紀初期

to describe the thick gray haze that covered cities

用來形容覆蓋在城市之上 那層厚重且呈灰色的霾

such as London,

就像倫敦

Glasgow,

格拉斯哥 (Glasgow)

and Edinburgh.

及愛丁堡

This industrial smog was known to form

這種工業煙霧據悉

when smoke from coal-burning home stoves and factories

是家用鍋爐及工廠燃煤所產生的煤煙

combined with moisture in the air.

結合空氣中的水氣所形成

But the smog behind the LA panic was different.

但這場讓洛杉磯驚慌的煙霧卻不同

It was yellowish with a chemical odor.

它是黃色的還帶有化學異味

Since the city didn't burn much coal, its cause would remain a mystery

既然這個城市並未燃燒太多煤炭 煙霧的起因成為問號

until a chemist named Arie Haagen-Smit identified two culprits:

一直到化學家艾瑞．哈格斯密 找到兩個罪魁禍首

volatile organic compounds, or VOCs,

揮發性有機化合物，簡稱 VOC

and nitrogen oxides.

以及一氧化氮

VOCs are compounds that easily become vapors

VOCs 是容易揮發的化合物

and may contain elements, such as carbon,

可以帶著其他物質如碳

oxygen,

氧氣

hydrogen,

氫氣

chlorine,

氯氣

and sulfur.

還有硫

Some are naturally produced by plants and animals,

有些是由植物或動物自然產生

but others come from manmade sources,

但其他來自於人造物

like solvents,

像是溶劑

paints,

油漆

glues,

and petroleum.

膠料

還有石油

Meanwhile, the incomplete combustion of gas in motor vehicles

同時因汽車燃油無法完全燃燒

releases nitrogen oxide.

會排放出一氧化氮

That's what gives this type of smog its yellowish color.

這是導致這類煙霧帶著黃色的原因

VOCs and nitrogen oxide react with sunlight

VOCs 及一氧化氮被光照時發生反應

to produce secondary pollutants called PANs and tropospheric,

產生出二級汙染物 PANs （過氧醯基硝酸鹽）

or ground-level, ozone.

以及對流層或是地面附近的臭氧

PANs and ozone cause eye irritation and damage lung tissue.

PANs 與臭氧刺激眼睛並傷害肺部

Both are key ingredients in photochemical smog,

兩者是光化學煙霧的主要物質

which is what had been plaguing LA.

也導致了洛杉磯的災禍

So why does smog affect some cities but not others?

但為什麼煙霧沒有 影響到所有的城市呢？

Both industrial and photochemical smog combine manmade pollution

工業及光化學煙霧兩者 都與人造汙染物

with local weather and geography.

及當地天氣及地理環境有關

London's high humidity made it a prime location for industrial smog.

倫敦的潮濕使它成為 工業煙霧的主要地點

Photochemical smog is strongest in urban areas with calm winds

最強的光化學煙霧 存在於帶有微風的都市

and dry, warm, sunny weather.

乾燥、溫暖、晴天的天氣

The ultraviolet radiation from sunlight provides the energy necessary

陽光中的紫外線輻射 提供了所需的能量

to breakdown molecules that contribute to smog formation.

將分子分解而形成煙霧

Cities surrounded by mountains, like LA,

像洛杉磯這種被群山環繞的城市

or lying in a basin, like Beijing,

或是建構在盆地的都市像北京

are also especially vulnerable to smog since there's nowhere for it to dissipate.

因為無處可分散煙霧 而特別容易產生

That's also partially due to a phenomenon known as temperature inversion,

這其中有部分來自於逆溫現象

where instead of warm air continuously rising upward,

溫暖的空氣沒有持續地往上升

a pollution-filled layer of air remains trapped near the Earth's surface

反而滯留在靠近地球的表面 被上面更為溫暖的一層所困住

by a slightly warmer layer above.

成為一層充滿著汙染物的空氣

Smog isn't just an aesthetic eyesore.

煙霧不僅醜陋傷眼

Both forms of smog irritate the eyes,

兩種類型的煙霧都對眼睛造成刺激

nose,

and throat,

還有鼻子

跟喉嚨

exacerbate conditions like asthma and emphysema,

加速氣喘、肺氣腫的惡化

and increase the risk of respiratory infections like bronchitis.

增加呼吸道如支氣管感染的風險

Smog can be especially harmful to young children and older people

煙霧對於幼童及老人特別有害

and exposure in pregnant women has been linked to low birth weight

曝露其中的懷孕婦女中有機會造成 嬰兒出生體重過低

and potential birth defects.

以及出生缺陷的可能性

Secondary pollutants found in photochemical smog

在光化學煙霧裡所找到的二級汙染物

can damage and weaken crops and decrease yield,

會損傷及削弱農作物還有降低收成量

making them more susceptible to insects.

讓作物容易受到蟲害

Yet for decades, smog was seen as the inevitable price of civilization.

這數十年來

煙霧被視為文明化所產生 無可避免的代價

Londoners had become accustomed to the notorious pea soup fog

倫敦客漸漸習慣那 惡名昭彰的綠色濃煙

swirling over their streets until 1952,

它們席捲著大街小巷

直到 1952 年

when the Great Smog of London shut down all transportation in the city for days

倫敦大煙霧事件 關閉了所有的交通達數天之久

and caused more than 4,000 respiratory deaths.

導致四千起以上呼吸道相關的死亡

As a result, the Clean Air Act of 1956

1956 年《清潔空氣法》隨之而生

banned burning coal in certain areas of the city,

禁止城市裡部分區域燃燒煤炭

leading to a massive reduction in smog.

促使煙霧的大幅降低

Similarly, regulations on vehicle emissions and gas content in the US

同樣的，美國對於車輛排放 及氣體內容的管控

reduced the volatile compounds in the air and smog levels along with them.

減少了空氣中的揮發性物化合物 及相隨的煙霧程度

Smog remains a major problem around the world.

煙霧在全球仍是個主要問題

Countries like China and Poland that depend on coal for energy

如中國或波蘭這類 仰賴煤炭能源的國家

experience high levels of industrial smog.

籠罩著重度的工業煙霧

Photochemical smog and airborne particles from vehicle emissions

光化學煙霧及來自 汽車廢氣的空浮粒子

affect many rapidly developing cities,

影響著許多正在快速開發的城市

from Mexico City and Santiago

從墨西哥市到智利的聖地牙哥

to New Delhi and Tehran.

從新德里到德黑蘭

Governments have tried many methods to tackle it,

各政府想盡辦法對付煙霧

such as banning cars from driving for days at a time.

如：在某幾天的特定時段禁止開車

As more than half of the world's population crowds into cities,

就當全球有一半以上的人口湧入城市

considering a shift to mass transit and away from fossil fuels

轉搭大眾運輸工具或是避用化石燃料

may allow us to breathe easier.

或許會讓我們的呼吸更順暢

本篇作者是一名高中自然科學老師

任教於紐約州水牛城 名為金·普茲霍

她三十多年的老師生涯 教過超過六千名學子

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