Isotopic measurements provide source and process constraints that are difficult to obtain from concentration data or molecular tracers alone. We combine radiocarbon (14C) and stable carbon isotope ratio (δ13C) measurements to distinguish fossil and non-fossil carbon and to further constrain contributions from coal combustion, liquid fossil-fuel emissions, and biomass burning to organic and elemental carbon. Size-resolved isotope measurements also reveal how secondary organic aerosol formation, aqueous-phase processing, and photochemical aging vary across particle sizes in urban environments.
We also develop analytical methods for isotope measurements at low carbon loadings. An automated thermal-optical system coupled with isotope-ratio mass spectrometry enables the separation and δ13C analysis of organic and elemental carbon at sub-microgram carbon loadings. More recently, our isotope research has expanded beyond carbonaceous aerosol to reactive chlorine. Chlorine-isotope measurements of nitryl chloride are used to distinguish oceanic and anthropogenic chlorine sources and to investigate atmospheric transport and cycling.
Representative publications
1. Zong, Z, Xia, M., Lin, C. S., Chen, X. R., Xue, L. K.*, Li, Q. Y., Jiang, Y. F., Tian, C. G., Fan, X. H., Yuan, Q., Wang, X. F., Zhu, Y. J., Zhang, J. S., Lee, S. C., Mu, Y. J., Li, J., Fu, X., Ren, C. H., Huang, X., Yan, C., Nie, W., Badia, A., Zhang, G., Ding, A. J., Huang, R. J.*, Kulmala, M., Saiz-Lopez, A., Wang, T.*, Wang, W. X.: Isotopic constraints on the origin of reactive chlorine in the troposphere, Science Advances, 12, eaeb5397, DOI: 10.1126/sciadv.aeb53, 2026.
2. Ni, H. Y., Huang, R. J.*, Yao, P., Cosijn, M. M., Kairys, N., Zhong, H. B., Dusek, U.*: Organic aerosol formation and aging processes in Beijing constrained by size-resolved measurements of radiocarbon and stable isotopic 13C, Environ. Int., 158, 106890, 2022.
3. Ni, H. Y., Zhong, H. B., Wang, Y., Yao, P., Tian, J., Ma, Y. Y., Huang, R. J.*, Dusek, U.: Reduction in organic aerosol from coal combustion is partially offset by enhanced secondary formation during the Beijing coal burning ban, Environ. Sci. Technol., 59, 9155-9166, 2025.
4. Ni, H. Y., Yao, P., Zhu, C. S., Qu, Y., Tian, J., Ma, Y. Y., Yang, L., Zhong, H. B., Huang, R. J.*, Dusek U.: Non‐fossil origin explains the large seasonal variation of highly processed organic aerosol in the Northeastern Tibetan Plateau (3,200 m asl), Geophys. Res. Lett., 50, e2023GL104710, 2023.
5. Yao, P., Ni, H. Y., Paul, D., Masalaite, A., Huang, R. J.*, Meijer, H. A. J., Dusek, U.*: An automated method for thermal-optical separation of aerosol organic/elemental carbon for 13C analysis at the sub-μgC level: A comprehensive assessment, Sci. Total Environ., 804, 150031, 2022.
