在郑州市区，公交车辆排成“长龙”缓缓前行（1月16日摄）。据郑州市环保局公布的信息，今年以来，郑州市空气质量明显下降。截至2月20日，空气质量指数只有2天达标，其中重度污染和严重污染有20天。主要污染物为PM2.5。环保部门还首次公布郑州市区灰霾天气的成因。燃煤烟尘、扬尘、机动车尾气和工业粉尘是PM2.5的四大来源。新华社记者 王颂 摄     In the city of zhengzhou,Transit vehicles in"Long dragon"Slowly forward(January 16, taken).According to the environmental protection bureau of zhengzhou city published information,Since this year,Zhengzhou city air quality decreased obviously.Twenty days in feb.,Air quality index only two days to amount to mark,The severe pollution and serious pollution is twenty days.The major pollutant PM2.5.The environmental protection department also published for the first time the city of zhengzhou gray haze weather causes.Coal dust/dust/The motor vehicle exhaust and industrial dust is PM2.5 four sources.The xinhua news agency WangSong perturbation

    一位清洁工冒着浓雾在擦拭郑州二七纪念塔塔顶的栏杆（1月16日摄）。新华社记者 王颂 摄 A cleaner braved heavy fog in polished zhengzhou erqi memorial tower top rail(January 16, taken).The xinhua news agency WangSong perturbation

    在郑州市中心的二七纪念塔附近，一台大型机械在施工（1月16日摄）。新华社记者 王颂 摄     In zhengzhou city center. Near the monument,A large machinery in the construction(January 16, taken).The xinhua news agency WangSong perturbation

凌晨，郑州市民们冒着浓雾赶路上班（1月11日摄）。新华社记者 王颂 摄 morning,Zhengzhou citizens braved heavy fog on work(On January 11, taken).The xinhua news agency WangSong perturbation

在郑州市区的一个工地上，大型机械在拆除旧建筑（2月1日摄）。新华社记者 王颂 摄 Of the city in a site,Large machinery on tearing down the old building(On February 1st shot).The xinhua news agency WangSong perturbation