2014年中国大陆地区冷、暖季大气颗粒物的分布特征

Spatial distribution of particulate matter in China's Mainland during cold and warm seasons in 2014

利用中国环境监测总站发布的2014年中国大陆地区114个站点的空气污染物质量浓度数据,系统探讨了中国大陆地区冷、暖季大气颗粒物的空间分布特征及其差异.结果表明,中国大陆大部分地区冷季的大气污染情况比暖季严重,冷季污染天数平均为76 d,约为暖季的2倍,其中北京、天津、石家庄和济南在冷季的严重污染天数分别是暖季的3.7、13.0、8.5和9.0倍.中国大陆地区大气颗粒物污染呈现明显的"冷高暖低"形势,w(PM_(2.5))/w(PM_(10))在冷季约为73%,是暖季的1.4倍,说明细颗粒物对冷季大气颗粒物污染的贡献非常重要.在颗粒物污染最严重的京津冀地区,w(PM_(2.5))的年平均值为100.3μg/m^3,冷季是暖季的1.5倍.与PM_(2.5)相比,沙尘事件的影响导致中国北方地区的w(PM_(10))相对较高.w(PM_(10))的冷、暖季差异相对较小,冷季w(PM_(10))约为暖季的1～2倍.除了人为排放影响外,气象条件是导致中国大陆地区大气颗粒物冷、暖季差异的重要因素.受热力、动力因素的影响,冷季的边界层高度相对较低、逆温强烈、地面风速小,气象条件不利于大气污染物的垂直扩散,导致近地面颗粒物质量浓度相较暖季偏高.

Air pollutant concentration data of 114 sites released by the China Environmental Monitoring Main Station in 2014 were utilized to discuss the space distribution characteristics and differences in atmospheric particles during cold and warm seasons in China's Mainland. Most large cities in China's Mainland showed different degrees of pollution. Days of mild and moderate pollution constituted 20.53%and 6.83%, respectively, of the total number of days. According to the spatial distribution, pollution in Beijing, Tianjin, and Shijiazhuang was particularly serious. The total number of pollution days in Shijiazhuang reached 275 d, with up to 38 d severe pollution days. Studies have shown that air pollution during cold seasons in most of China's Mainland was obviously more severe than that during warm seasons. The number of cold-season pollution days（75.4 d） was approximately 1.67 times that of the warm season（45 d）, with the number of serious pollution days during the cold season in Beijing, Tianjin, Shijiazhuang,and Jinan being respectively 3.7,13.0, 8.5 and 9.0 times higher than those during the warm season. The particulates in China's Mainland（especially fine particles） also indicated that the concentration of cold pollution days was higher than that during the warm season. High fine particulate matter PM2.5 concentrations were mainly distributed in the eastern regions during the warm season, and the PM2.5 pollution in Beijing, Tianjin and Hebei was the most serious in China's Mainland. The distribution of PM2.5 during cool and warm seasons was similar, but the concentration during the former was twice that of the latter. The ratio of w（PM2.5）/w（PM10） during the cold season（73%） was approximately 1.4 times higher than that during the warm season（53%）. Particulate matter pollution was the most serious in the Beijing-TianjinHebei region, where the annual average PM2.5 concentration was 100.3 μg/m^3. w（PM2.5） during the cool season was 1.5 times higher than that during the warm season. Compared with w（PM2.5）, w（PM10） was relatively high in northern China because of the impact of dust. The difference w（PM10） during warm and cold seasons was relatively small, with the w（PM10） during cold seasons measuring 1 to 2 times higher than that during warm seasons. In addition to the impact of anthropogenic emissions, atmospheric particulates were an important cause of these differences between warm and cold seasons. The boundary layer height was lower during cold seasons, the inversion was stronger, and the wind speed near the ground was smaller. These properties were not conducive to the vertical diffusion of atmospheric pollutants,thus,the concentration of particles near the ground would rise.