纳米颗粒物吸湿性和化学组分特征研究

New particle formation is an important source of aerosol particles and a crucial gas-to-particle secondary transformation process in the atmosphere. Knowledge about the chemical composition of nanoparticles is essential to understand their formation and growth mechanisms. Due to analytical limitations, however, direct chemical composition measurement of newly formed particles (sub-10 nm) particles is still difficult. In this project, we are trying to extend the use of water-based condensation particle counter, and to design a nano-cloud condensation nuclei counter (nano-CCNC) with high time resolution and stable supersaturation distribution, ensuring the rapid response and long-term stable operation under ambient atmosphere. Measurement procedures and data analysis methods are established through laboratory experiments with varied mixture and size-resolved nanoparticles. The measured hygroscopicity parameter will be compared with the calculated ones from the traditional thermodynamic models to explore the influence of the size effect on particle hygroscopicity. Finally, we will perform the nano-CCNC in the field measurements, which may provide further insight into the chemical composition of nanoparticles and the role of organic and inorganic compounds in the initial steps of atmospheric new particle formation and growth.

新粒子生成是大气细颗粒物的主要来源，也是重要的气粒二次转化过程。纳米颗粒物的化学组分信息对研究新粒子的生成和增长机制非常重要。由于测量技术手段的限制，目前尚无法直接测量新生成颗粒物（小于10 nm）的化学组分。本研究拟通过以水系颗粒物凝结计数器为核心，研发一套具有高时间分辨率、稳定过饱和度分布的纳米颗粒物活化测量仪，保证其能够实现对环境大气的快速响应和长期稳定运行。通过在实验室对不同体系和不同粒径气溶胶吸湿性的测量，建立和完善标定和数据处理方法，并结合传统热动力学模式探究纳米效应对颗粒物吸湿性的影响。最终和外场观测相结合，定量不同组分在新粒子初始增长过程中的作用。

颗粒物的化学组分信息对研究其在大气中的生成和转化过程非常重要。由于测量技术手段的限制，目前尚无法直接测量新生成颗粒物（小于10 nm）的化学组分。本项目研发了一套通过改变样气流量来扫描过饱和度的高时间分辨率纳米颗粒物活化测量仪，通过对不同体系纳米颗粒物的测量，建立了完善的标定和数据处理方法，研究发现纳米颗粒物的吸湿性和有机组分呈线性关系。同时我们探究了纳米效应对颗粒物吸湿性的影响，结果表明吸湿性参数是粒径的函数，不同的热动力学参数可能是CCN闭合误差的重要来源。因此我们强调使用统一的参数化模型来标定仪器和反演颗粒物的化学组分。我们的工作为纳米颗粒物化学组分的测量及新粒子生成和增长机制的研究提供了新的思路。