秸秆焚烧影响南京空气质量的成因探讨

The origin of crop residue burning impact on air quality of Nanjing

综合利用卫星遥感的火点和云覆盖信息,结合气团后向轨迹分析,探讨了由秸秆焚烧造成的空气污染物的区域尺度输送和本地源对城市空气质量的影响.结果表明,在一定气象条件下,污染物可以发生区域尺度的输送,上风火点与下风城市的污染有明显的相关,将空气污染分为局地型(如,2006年5月31日、2009年11月8日)、区域型(如,2008年10月28日),以及局地区域相结合型(如,2006年6月14日、2007年6月5日、2008年6月2日)3种.应用本文的方法,在有云时,可以通过部分火点和气团后向轨迹分析推测污染物源地.空气污染气象条件分析表明,秸秆焚烧若伴随高空(500hPa)有槽(或位于槽前),低空存在弱切变,气流由周边向中心辐合;同时,若在均压场控制下,等压线稀疏,风速较小或静风,污染物则易积聚而不易输送;逆温层的形成将污染物禁锢在混合层以下,不利于垂直扩散;再加上较大的相对湿度,有利于霾的形成,造成严重空气污染。

The regional transport and local sources of air pollution inducing by crop residue burning was discussed by using satellite remote sensing of fire hot spots data,cloud cover information and back trajectory analysis.The results showed that the polluted air mass could dispersion in regional scale in certain meteorological condition and the relationship between upstream fire hot spots and downstream city Air Pollution Index was obviously.We categorized the air pollution events into three types,which were local（e.g.,31May 2006,8November 2009）,regional（e.g.,28October 2008）,and the integration of the two（e.g.,14June 2006,5June 2007,2June 2008） respectively.By using fire hot spots and air mass back trajectory analysis,the source of pollutants could be conformed in cloudy days.Weather conditions of air pollution analysis showed that crop residue burning accompanies 500hPa trough（in or in front）,low shear and weak convergence in atmospheric boundary layer,sparse isobar,low wind speed/calm wind,are not convenience for air pollutants dispersion.On the other hand,inversion layer confined the pollutants in the mixing layer and high relative humidity was in favor of the formation of haze,intensifying air pollution.