2014年10月上旬北京市大气重污染分析

Analysis on heavy air pollution in Beijing in early October, 2014

使用垂直观测、地面观测和PM2.5化学组分观测等手段,对2014年10月上旬北京市一次重污染过程进行分析.结果表明,本次大气重污染发生时北京市近地面后散射激光强度变强,气溶胶消光系数升高,说明污染物在近地面层积累.重污染期间气象要素特征为:风场弱,湿度大,地面受弱气压场控制.从PM2.5浓度变化趋势来看,这次重污染过程大体分为四个阶段:"两个台阶"型的浓度爬升阶段(P1和P2)、高浓度维持阶段(P3)和迅速清除阶段(P4).结合地面观测、遥感反演和PM2.5组分分析可发现,区域传输是导致本次重污染的诱因,其中秸秆焚烧是影响因素之一,随后区域传输和本地污染物排放共同维持并加重了重污染过程.大气氧化剂OX与PM2.5浓度、二次离子浓度均表现出显著正相关性,表明较强的大气氧化性能促进PM2.5浓度增长.

A heavy air pollution process in Beijing on 7-11 October, 2014 was analyzed through vertical observation, ground-based observation and monitoring results of chemical components of PM2.5. The results showed that the surface-level backscatter density and extinction coefficient increased significantly during the heavy pollution, which suggested that air pollutants accumulated near the ground. Compared with the normal days, wind speed was weaker, and relative humidity was higher and surface pressure was lower during the heavy pollution. According to the trends of PM2.5 concentrations, this heavy pollution process was divided into four stages, including two-step type concentration climbing stages （Pland P2）, high concentration maintenance stage （P3） and rapid cleanup stage （P4）. Through analysis on ground-based observation, remote-sensing retrieval and chemical components of PM2.5, it could be concluded that regional transmission, including straw burning, was the main incentive of this heavy pollution. Regional transmission and accumulation of local pollutant emission maintained and aggravated the heavy pollution. Atmospheric oxidants OX showed significant positive correlation with concentrations of PM2.5 and secondary ions, which suggested that strong atmospheric oxidation promoted the increase of PM2.5 concentrations.