2013年1月宁波市PM_(2.5)污染的形成过程与传输规律

为了深入认识宁波市冬季细颗粒物(PM2.5)的污染特征和主要影响因素的作用规律,利用Models-3/CMAQ模式系统对2013年1月宁波市的PM2.5污染形成过程进行了模拟分析.结果表明,宁波市PM2.5的重点污染区主要分布在市区、北部地区及东部沿海,除了受到局地污染源排放的影响外,对比非污染的情况,大气输入和气溶胶生成作用的增强是引起PM2.5污染的主导因素,其中水平传输过程对PM2.5浓度升高的贡献最为突出.气溶胶过程的贡献在近地面(0~80 m)最显著,随着高度升高而逐渐减弱.硝酸盐在局地二次生产的细颗粒物中占主要份额(~70%).对于硫酸盐,局地二次生成所占的比例很低,主要来自宁波局地排放和宁波以外地区的大气传输(贡献比例分别为44%和40%).宁波市的PM2.5污染主要受到来自北向沿岸气团(占比54%)、西北向大陆气团(占比21%)和西向局地气团(占比25%)的传输影响.在西北方向短距离区域传输的作用下PM2.5浓度最高;在我国中东部大范围灰霾天气的影响下,西北向和北向的长距离传输作用也会导致宁波地区的PM2.5污染.

Formation and Transport of PM2.5 Pollution over Ningbo in January, 2013

To investigate PM_2.5 pollution characteristics and its major affecting factors, the Models-3/CMAQ modeling system was applied to simulate PM_2.5 pollution in Ningbo in January, 2013. The results showed that high levels of PM_2.5 occurred in the downtown, the north region and the east coastal region of Ningbo. Besides local emissions, aerosol formation and transport processes of PM_2.5 were enhanced during the non-attainment days compared with the attainment days, especially horizontal transport process. The contribution of aerosol formation process was significant near the ground, and decreased gradually with the height. Nitrate accounted for ~70% of secondary fine particulate matter. Sulfate was mainly from the atmospheric transports and primary emissions of Ningbo, accounting for 40% and 44% of sulfate level, respectively. PM_2.5 pollution of Ningbo was mainly influenced by the transport of northern coastal air mass (54%), northwestern continental air mass (21%) and western local air mass (25%). The highest PM_2.5 concentration was primarily related to short-distance transport from the northwest. When East China suffered from fine particle pollution (haze) on a large scale, long-distance transport from the northwest and the north would also lead to PM_2.5 pollution in Ningbo.