北京地区三级以上污染日的气象影响因子初步分析

依据2001—2007年北京市环境保护局公布的SO2、NO2和PM10日平均空气质量等级大于或等于三级以上的污染日作为样本,统计分析了污染日3种污染物指数与同期南郊观象台(近郊区)的地面和探空气象要素的相关关系。同时采用Hysplit-4后向轨迹分析方法,对出现四级以上污染的重污染日污染源进行了初步探讨。结果表明:风向是造成上述3种污染物出现重污染的主要原因之一;污染日存在两重或多重逆温层,而且逆温层较低较厚,垂直对流和水平扩散作用较弱,湿沉降作用较小,因此污染物不易扩散和输送,堆积在近地面,造成重污染。北京西南、东南部地区以及沙尘暴过程内蒙古、河北北部是造成重污染天气的主要输送源地。研究结果可为北京重污染过程的预警预测及其综合防治提供科学依据。

Effects of meteorological factors on air quality above the third grade pollution in Beijing

The relationship between mean daily pollution indices of SO2, NO2, PM10 issued by Beijing municipal environmental protection bureau during 2001-2007 and synchronous meteorological factors such as ground and radiosonde data from Beijing observatory were analyzed by statistic method based on air pollution day of the third grade or that above the third grade in Beijing. At the same time, pollution sources of serious pollution day that mean daily air pollution indices of SO^₂, NO₂, PM₁₀ were the forth grade or above were discussed by backward trajectory analysis method (Hysplit-4 model). The results indicate that wind direction is one of main reasons leading to serious pollution of three pollutants. There are two layers or multi-layers inversion layer in pollution day. Inversion layer is lower and deeper, vertical convection, horizontal diffusion and wet deposition are very weak, so pollutants are difficult to be diffused and transported. They are accumulated on the ground, which comes into being serious pollution. The main source locations of heavy pollution weather are located in the southwest and southeast of Beijing, in Inner Mongolia and in the north of Hebei province. The results could provide scientific basis for heavy pollution alarm and forecast and integrated control systems in Beijing.