Facile Differentiation of Four Sources of Water-Soluble Organic Carbon in Atmospheric Particulates Using Multiple Fluorescence Spectral Fingerprints

Water-soluble organic carbon (WSOC) is an important component of atmospheric particulate matter, consisting of complex and reactive organics with significant environmental impacts such as light absorption and health risks. This study proposed a source identification method for particulate matter based on the excitation-emission matrix (EEM) multiple fluorescence spectral fingerprints of WSOC. It was found that EEM fluorescence fingerprints, including fluorescence spectra and fluorescence parameters, could recognize differences in chemical structure characteristics of WSOC from diverse sources involving biomass burning, coal combustion, dust emission, and vehicle emission. Applying statistical methods such as Bootstrap sampling and the Mann-Whitney U test, a simple guide to determine the pollution source of particulate matter was established based on discrepancies in fluorescence fingerprints such as the modified regional fluorescence integral and fluorescence quantum yield. Fourier-transform infrared spectroscopy and ultrahigh-performance liquid chromatography-mass spectrometry combined with parallel factor analysis showed that the diversity in EEMs of different source samples was attributed to aromatic groups with various side chains and substituents. This study will provide a simple and intuitive potential approach for the source apportionment of atmospheric particulate matter and set the stage for studying the relationship between atmospheric chemical processes and fluorescent components.