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据国家环保总局1999年《中国环境状况公报》报道,在被统计的338个城市环境空气质量中,达到国家空气质量二级标准的只有33.1％;剩余66.9％的城市都超过二级标准,有137个城市超过三级标准,为40.5％。作为造成空气污染的氮氧化物(NOx)大部分来源于矿物燃料的燃烧过程,包括燃煤和燃
According to the State Environmental Protection Administration’s “Bulletin on the State of China’s Environment 1999”, only 33.1% of the ambient air quality of the 338 cities in the country that has reached the national secondary air quality standard has been reported; the remaining 66.9% of the cities have exceeded the Grade II standard, with 137 cities exceeded the third-grade standard, which is 40.5%. Most of the nitrogen oxides (NOx) that cause air pollution come from the combustion process of fossil fuels, including coal combustion and combustion