In 2001, the annual average of NO2 concentration in the air of 341 cities attained the Grade II national standards for air quality.

  • 2001年,341个城市空气中二氧化氮浓度年均值均达到国家环境空气质量二级标准。

  • 互联网摘选 2026-07-02 15:28:34

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