Fluorescence characterization of dissolved organic matter in East China sea

Abstract

Sea water samples were collected in the East China Sea in March and April, 2005, and three-dimensional fluorescence of dissolved organic matter was measured by fluorescence excitation-emission matrix spectroscopy. The position, number and intensity of fluorescence peak in the spectra and the relations of the peaks were analyzed to determine the type, distribution and origin of the fluorescence dissolved organic matter. Seven types of fluorescence peaks were detected from the samples. There are protein-like fluorescence peaks B with Exmax/Emmax = 275/300 nm, D with Exmax/Emmax = 225/295-305 nm, T with Exmax/Emmax = 280/345 nm, and S with Exmax/Emmax = 225-240/320-350 nm, two humic-like peaks A with Exmax/Emmax = 250-255/410-455 nm and C 335-345/410-440 nm, and marine humic peak M with Exmax/Emmax = 305 nm/400-420 nm. Peaks B, S and A appeared in all surveyed area. Peaks T and D appeared in the north of the surveyed area. Peaks M and C only appeared in a few stations. In the surface layer, the source of the fluorescence dissolved organic matter might be the fresh water outflow of the Yangtze River, while the fluorescence dissolved organic matter in the middle layer had double sources from the Yangtze River and the phytoplankton. The good correlationships of different fluorescence peaks showed the same source or some relationship between the protein-like and the humic-like fluorescence dissolved organic matter.