细颗粒物是造成城市空气污染的主要原因之一。城市热环境对空气中细颗粒物的质量浓度分布有着直接的影响，特别是在城市热岛效应明显的城市，其一，高温能促使气溶胶形成，其二，逆温作用会抑制细颗粒物的扩散，其三，热岛辐合效应与次生环流导致局地细颗粒物难以扩散。因此，改善城市热环境是降减细颗粒物质量浓度的有效途径之一。城市绿地在改善城市热环境上作用明显，如可以消低热岛效应强度、减少局地垂直热岛环流、形成良好的小气候、产生“林源风”等，从而间接降减细颗粒物质量浓度。本课题重点研究城市绿地对降减空气中细颗粒物质量浓度的间接作用，通过城市绿地对改善城市热环境的功能，来减少气溶胶的形成和改善细颗粒物的扩散条件，从而达到降减细颗粒物质量浓度、改善空气质量的目的。由于北京在空气污染和热岛效应上的典型性，课题以北京为研究地，采用实地与遥感观测、数值模拟两种主要方法，通过优化城市绿地系统来间接降减细颗粒物质量浓度。

The fine particulate matter (PM2.5) is one of the important resources of air pollution in cities. Urban thermal environment has immediate impact on the distribution of fine particals in cities, especially in those with strong urban island effects. First, the high temperature stimulates the formation of aerosols. Secondly, the thermal inversion suppresses the diffusion of fine particles. Thirdly, unbalanced urban heat island causes verticle thermodynamic circulation, which will block the diffussion of fine particles. Therefore, the improvement to urban thermal environment is one of efficient ways to reduce the fine particulate matter concentration. Urban green spaces can obviously improve urban thermal environment, including elimination or moderation heat island effect by changing underlying surface, creating good microclimate, and generating forest edge wind, in consequence indirectly reduce fine particulate matter concentration in cities. .This research focuses on the indirect effect of urban green spaces to reduce fine particulate matter concentration, reducing aerosols and accelerating diffusion of fine particles by improving the urban thermal environment, so that the fine particulate matter concentration could be reduced, and then air quality could be improved. Because Beijing has typicality in air pollution caused by fine particulate matter and urban heat island effect, this research chooses Beijing as the object to study. The two methods of on-site and remote sensing detection, and digital simulation are used to implement reduction of fine particulate matter concentration through urban green space system.