Atmospheric nanoparticles hygroscopic growth measurement by combined surface plasmon resonance microscope and hygroscopic-tandem differential mobility

WashU Affiliated Authors: Jiaoshi Zhang (Center for Aerosol Science and Engineering, Department of Energy, Environmental & Chemical Engineering)

Abstract: The hygroscopic growth of atmospheric aerosols plays an important role in regional radiation, cloud formation and hence climate. Aerosol hygroscopic growth is often characterized by humidified tandem differential mobility analyzers (HTDMA), and Xie et al. (2020) recently demonstrated that hygroscopic growth measurements of single-particle are possible using a surface plasmon resonance microscope-azimuthal rotation illumination (SPRM-ARI). The hygroscopic properties of ambient aerosols are not uniform and often exhibit large RH and size variabilities, due to different chemical compositions and mixing states. To better understand the contribution of different aerosol components and establish the link between the apparent hygroscopic properties of bulk aerosols and single-particle, we conduct combined hygroscopic growth measurements of single-particle by a SPRM-ARI and bulk particles by an HTDMA. The atmospheric nanoparticles were grouped into four subgroups labeled as EC, fly ash, OC and AS+OC based on the energy dispersive spectroscope results (Experimental information: 100 nm~200 nm, at noon, September 28th, 2021 and March 22th, 2022 in Hefei China). The relationship between the chemical composition of a single nanoparticle in each subgroup and its hygroscopicity was characterized using SPRM-ARI. Then, the HTDMA data were shown to be fitted and reconstructed by the constitutive particle size distributions calculated by the SPRM-ARI measured GFs (growth factor), and the percentage of four subgroups in atmospheric particles could also be found through the fitting. Based on the test results, we found the OC content of AS+OC nanoparticles increased with the increase of particle size, and the OC condensation may play a promoting role in the particle growth process. Lastly, this fitting reconstruction method has a good correlation with the quantitative results of membrane sampling, and can be used for reference to analyze the contribution of particle hygroscopicity and the growth mechanism of nanoparticle.

Citation/DOI: Xie, Z., Zhang, J., Gui, H., Liu, Y., Yang, B., Dai, H., Xiao, H., Zhang, D., Chen, D.-R., and Liu, J.: Atmospheric nanoparticles hygroscopic growth measurement by combined surface plasmon resonance microscope and hygroscopic-tandem differential mobility analyzer, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2022-666, in review, 2022.