Three-dimensional fluorescence spectral characteristics of different molecular weight fractionations of dissolved organic matter in the water-level fluctuation zones of Three Gorges Reservoir areas

Abstract

The study of the molecular weight (MW) fractions of dissolved organic matter (DOM) in aquatic environment is of interests because the size plays an important role in deciding the biogeochemical characteristics of DOM. Thus, using ultrafiltration (UF) technique combined with three-dimensional fluorescence spectroscopy, DOM samples from four sampling sites in typical water-level fluctuation zones of Three Gorge Reservoir areas were selected to investigate the differences of properties and sources of different DOM MW fractions. The results showed that in these areas, the distribution of MW fractions was highly dispersive, but the approximately equal contributions from colloidal (Mr 1×103-0.22 μm) and true dissolved fraction (Mr<1×103) to the total DOC concentration were found. Four fluorescence signals (humic-like A and C; protein-like B and T) were observed in all MW fractions including bulk DOM, which showed the same distribution trend: true dissolved>low MW (Mr 1×103-10×103)>medium MW (Mr 10×103-30×103)>high MW (Mr 30×103-0.22 μm). Additionally, with decreasing MW fraction, fluorescence index (FI) and freshness index (BIX) increased suggesting enhanced signals of autochthonous inputs, whereas humification index (HIX) decreased indicating lower humification degree. It strongly suggested that terrestrial input mainly affected the composition and property of higher MW fractions of DOM, as compared to lower MW and true dissolved fractions that were controlled by autochthonous sources such as microbial and alga activities, instead of allochthonous sources. Meanwhile, the riparian different land-use types also affected obviously on the characteristics of DOM. Therefore, higher diversity of land-use types, and also higher complexity of ecosystem and landscapes, induced higher heterogeneity of fluorescence components in different MW fraction of DOM.

Keywords

Dissolved organic matter(DOM); Three Gorges Reservoir areas; Three-dimensional fluorescence spectrum; Ultrafiltration; Water organic colloid; Water-level fluctuation zones

Published in

Huan Jing Ke Xue
2016, volume: 37, number: 3, pages: 884-892
Publisher: Science Press

SLU Authors

• Jiang, Tao

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • Southwest University

UKÄ Subject classification

Ecology

Publication identifier

• DOI: https://doi.org/10.13227/j.hjkx.2016.03.012

Permanent link to this page (URI)

https://res.slu.se/id/publ/130340