Spectroscopic Characterization of Dissolved Organic Matter Isolated from Rainwater

The dissolved organic matter (DOM) in rainwater were collected from universities town of Guangzhou and were characterized with UV-Vis absorbance and three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopies. The results shown that the UV-Vis absorbance spectra exhibited similar characteristics, which was exponential attenuation with the increasing wavelength. The spectral slope coefficient (S) of UVvisible spectra indicated relative higher molecular weight in summer than that in spring and winter. Three fluorophores were identified in the EEM fluorescence spectra of DOM: The UV humic-like peak A, the marine humic-like peak M and the protein-like peak (tryptophan) T, and the humic-like peak A was the dominant component in the rain DOM in Guangzhou. Humification index (HIX) suggested that the rain DOMs in winter were characterized with relatively high humification degree.