2月28日，在北京宣武门外大街一天桥上，手机上的空气污染指数应用程序显示当日10时北京空气污染指数458，空气质量属重度污染。当日中午，北京大部分地区出现沙尘天气。据北京气象台消息，由于目前蒙古国和内蒙古自治区出现大片沙尘区，在空中西北气流输送下，北京中午前后出现长时间沙尘天气，北京全境已开始由雾霾污染转变为沙尘污染。新华社发（张铖 摄）     On February 28,,An overpass in Beijing xuanwu gate street,Air pollution index on the mobile phone application shows that Beijing's air pollution index at 10, 458,Air quality is severely polluted.At noon on the day,Sand and dust weather in most parts of Beijing.According to the Beijing meteorological center,Because at present a large dust area of Mongolia and Inner Mongolia autonomous region,Northwest under the air in the air,Beijing around noon in dust weather for a long time,All of Beijing has began to turn the fog haze pollution of dust pollution.Xinhua hair(Zhang Cheng perturbation)

    2月28日，游客在北京天安门广场游览时迎风前行。新华社记者 金良快 摄     On February 28,,Tourists to visit in Beijing's tiananmen square when the wind.Xinhua news agency reporter Jin Liang quickly taken

2月28日拍摄的北京天安门广场。新华社记者 金良快 摄 On February 28, Beijing's tiananmen square.Xinhua news agency reporter Jin Liang quickly taken

2月28日，一位女士在北京三环路上迎风骑行。新华社记者 何俊昌 摄 On February 28,,A lady in Beijing sanhuan on riding in the breeze.The xinhua news agency reporters He Junchang perturbation