大气细颗粒物的密度和混合态是计算全球辐射强迫的重要参数，也蕴藏着丰富的大气颗粒物排放、形成和转化信息。本项目拟以DMA-APM和V-TDMA观测为主、以ATOFMS和TEM-EDX为辅的方法研究上海地区大气亚微米细颗粒物的密度分布和混合态。通过长期的系统观测，系统表征大气亚微米细颗粒物的平均有效密度和密度分布，包括日变化特征、季节变化特征和典型天气特征。通过严密的梯度热脱附实验和系统观测，定量表征大气细颗粒物的挥发性和内混合态。重点研究大气细颗粒物密度和混合态的时空演化机制，竭力透过密度和混合态信息探讨大气细颗粒物（尤其是纳米颗粒物）在不同污染背景下的形成和转化机制。所得结果可为丰富长江三角洲地区大气污染化学理论提供基础数据。

Density and mixing state of submicrometer aerosols are of atmospheric importance,and what is more, a realistic treatment of density distribution and mixing state of urban aerosols is ctritical for the modelling of global radiative forcing. On the other hand, density distribution and mixing state show a power light to the particle emission, formation and transformation.In this proposal, determination of density distribution and mixing state of submicrometer aerosols in Shanghai are scheduled by methods of DMA-APM and V-TDMA, coordinated with ATOFMS and TEM-EDX.With extended field observation, average effective densities and density distribution of submicrometer aerosols will be thoroughly characterized, including diurnal, seasonal variations and haze episodes.With temperature-resolved thermodesorption and ehanced observation at constant temperature, we devote ourselves to quantitative description of volatility and internal mixing state of submicrometer atmospheric aerosols.This object is emphasized on analysis of time and spatial features of density and mixing state, as well as to reveal particle formation and transformation mechanism under defferent levels of pollution through information about density and mixing state. These results will support basic information for the further understanding of the atmospheric pollution chemistry in Yangtze River Delta.