The city's weather bureau gave air quality a rare hazardous ranking.

城市气象局给了今天的空气质量一个罕见的危险排名。

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However, rare earth is often radioactive. Moreover, in the smelting and extraction of rare earth, dangerous chemicals are frequently used, thus polluting local air, water and land.

但是，稀土生产往往带有放射性，加工企业在冶炼和分离稀土时，也经常使用危险的化学品，周围的空气、水和土地容易遭到污染。

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Neon, a rare gas in the air, takes only fractional percentage point of the volume.

氖是空气中的稀有气体，只占空气体积的千分之几。

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This is clear that this was a mistake,". He added that incidents such as this one are rare, especially after the United States imposed new restrictions on air strikes in an effort to avoid civilian casualties.

VOA: standard.2009.11.07

There's a lot of rare air here.

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Without such particles, clouds would be rare: the air would need to be freakishly saturated with water vapour or strangely cold for condensation to occur.

ECONOMIST: Aerobiology

Atlantis was caught in a rare desert downpour after landing at Edwards Air Force Base in the Mojave Desert on February 20.

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