Fluorescence fingerprinting characteristics of water-soluble organic carbon from size-resolved particles during pollution event

Abstract

A typical haze pollution process in northern China has necessitated this study which focuses on the fluorescence characteristics of water-soluble organic carbon (WSOC) in size-resolved particles. High concentrations of WSOC were found in both fine (38 μg/m³) and coarse particles (36 μg/m³) during the pollution period, which may be related to the secondary formation of organic aerosols and stable meteorological conditions. Five fluorescent components in WSOC were extracted by parallel factor analysis. Our results showed that the fluorophores in fine and coarse particles were mainly humic-like substances (humic-like, terrestrial humic-like, and high oxidation humic-like substances) and protein-like substances (protein-like and tyrosine-like substances), respectively. Moreover, the aging degree analysis, pollution source tracing, and concentration prediction of WSOC were carried out by fluorescence index. An innovative technique called self-organizing map was proposed for an in-depth investigation of the contamination mechanism of the atmospheric organic aerosol. Furthermore, the difference in the fluorescence characteristics of WSOC in fine particles was higher than that in coarse particles. The atmospheric pollution process increased the degree of difference in fluorescence characteristics. Additionally, an effective method for predicting the size of atmospheric particles was established by combining excitation-emission matrix fluorescence spectroscopy with classification and regression tree analysis.