大气超细颗粒物凝结增长动态过程在线分析关键技术及机理研究

The regional and complex air pollution has becoming increasingly prominent in China, the atmospheric fine particle matter has become a primary air pollutant, greatly affects the economic development, ecological environment and human health. Currently, the classical condensation growth theory of atmospheric particles is difficult to analyze the mechanism of the explosive growth of severe haze, the existing on-line analytical technique is difficult to characterize the condensation growth process of the ultrafine particles comprehensively. Therefore, this project proposes an on-line technique for analyzing condensation growth process of the ultrafine particles, solves the low activation and charge efficiency of ultrafine particles as well as the dynamically controlling of condensation growth process..Based on the phase transition thermodynamics theory, this project establishes the condensation growth model of ultrafine particles under the complex environmental conditions, analyzes the relationship between particle properties and environmental parameters, proposes an on-line technique for analyzing condensation growth process of the ultrafine particles based on the mixing type and miniaturization charging and classification, establishes a dynamic system for analyzing condensation growth process of the ultrafine particles, quantitatively studies the particle condensation properties under varying supersaturation and other controllable conditions. Combined with the theoretical model, experimental simulation and field observations, this project is committed to figure out the mechanism of particle condensation growth and its key factors, providing theoretical foundation and technical support for research of the particle formation and evolution mechanism and model forecast of the severe haze.

我国区域性大气复合污染问题日益突出，大气细颗粒物已成为首要大气污染物，严重影响到经济发展、生态环境和人体健康。当前，大气颗粒物的凝结增长经典理论难以准确解析大气复合污染条件下重霾爆发增长机制，现有在线分析技术难以全面表征大气超细颗粒物的凝结增长过程。为此，本项目提出大气超细颗粒物凝结增长过程在线分析方法，并解决超细颗粒物的活化与荷电效率低、凝结增长过程难以动态调控等问题。.本项目从相变热力学原理出发，建立复杂环境条件下的超细颗粒物凝结增长模型，系统分析颗粒物性质与环境参数的影响关系；提出基于混合方式、微型化荷电分级等超细颗粒物凝结增长过程在线分析方法；建立超细颗粒物凝结增长动态过程在线分析系统，定量化研究在不同过饱和度等可控条件下的颗粒物凝结增长特性；结合理论模型、实验模拟与外场观测，明晰颗粒物凝结增长机理及其关键因子，为重霾期间颗粒物形成和演变机制研究以及模式预报提供理论基础与技术支撑。

大气细颗粒物已成为我国大气污染的首要污染物，大气超细颗粒物的凝结增长与雾霾共存的大气污染状况密切相关，但其动态过程及霾雾转化机理仍不明确。本项目建立了大气污染超细颗粒物凝结增长动力学模型，设计了新型的过饱和凝结增长系统，并完成了纳米单颗粒和多颗粒吸湿增长的验证实验，进一步提高了对颗粒物凝结增长过程的认识。.在过去的4年中，围绕项目的目标和内容，主要工作及成果如下：.（1）建立了全尺度大气超细颗粒物凝结增长动力学模型。主要包括固体表面气液相变的动力学模型、不可溶球形颗粒表面上的异质稳态成核率，液滴在固体表面和惰性气体环境下增长和减小的模型，实现球形颗粒上异质凝结完整过程的建模和模拟，并从分子动力学角度验证了成核模拟过程。.（2）提出了大气超细颗粒物凝结增长动态过程测量方法。基于流体力学和传热传质理论，建立了水蒸气与纳米颗粒物传热传质模型，设计了三段式过饱和增长控制方案，分析了温控参数、系统流量、温差及温差窗口对饱和度和临界活化尺寸的影响。.（3）建立了多颗粒物和单颗粒物凝结增长过程在线测量系统。设计了基于膨体聚四氟乙烯（ePTFE）水汽热梯度扩散结构的凝结增长腔，实现了水汽过饱和度的精确控制（1.08 - 7.16）。提出了基于光学表面波的微纳单颗粒物吸湿增长特性测量方案，实现了对小于100nm单颗粒物的原位加湿表征，为超细单颗粒原位吸湿测试提供了一种全新的分析手段。.（4）利用搭建的凝结增长测量系统，开展了不同粒径、不同组分、不同饱和度下的标准粒子增长实验。结果表明，单一组分单分散颗粒物增长随水汽饱和度增加而持续增大。不同比例混合组分的对凝结增长因子有所区别，有机葡萄糖与无机硫酸铵的混合体系中，硫酸铵对凝结增长的贡献占主导地位。这些研究结果进一步提高了对水汽与颗粒物在实际大气环境中相互作用过程的认识。.在项目研究过程中，已在Science Advances等期刊发表论文17篇，发表会议论文4篇，申请专利11项，做国际学术会议报告5次。