[Fluorescence characteristics of fractionated colloidal organic matter in freshwater from Hunhe and Taizihe watersheds].

The ultrafiltration system with molecular mass of 100 x 10(3) and 1 x 10(3) membrane was used for the fractionation of total dissolved organic matter (DOM) in waters from Hunhe and Taizihe Watersheds. The fluorescence properties of colloidal organic matter with different sizes were investigated using a three-dimension excitation-emission matrix (3-D EEM) fluorescence spectroscopy. It was shown that the tryptophan-, fuvic-and humic-like materials were presented in the waters from Hunhe and Taizihe Watersheds, of which fuvic-and humic-like materials were mainly in colloidal form with small size (relative molecular mass < 100 x 10(3)) and truly dissolved phase (relative molecular mass < 1 x 10(3)). The adsorption of protein-like matters onto the colloid particles made the majority of these materials in colloidal phase though they had a low molecular mass. The higher percentages of small colloidal and truly dissolved organic carbon in total dissolved organic carbon (DOC) were observed in the water samples collected in wet season. Fluorescence index (FI), index of recent autochthonous contribution (BIX) and humification index (HIX) indicated that humic-like components in truly dissolved phase were mainly originated from autochthonous source and colloidal humic-like components were mainly derived from terrestrial organic matter. The recent autochthonous organic matter made a major contribution to truly dissolved phase. The humic-like matter was the domain of DOC content, but the contribution of protein-like materials to the organic carbon was not negligible due to the pollution of waterbody by industrial wastewater discharge.