Ultraviolet-visible (UV-Vis) and fluorescence spectral characteristics of soil dissolved organic matter (DOM) in typical agricultural watershed of Three Gorges Reservoir region

Abstract

As an important geo-factor to decide the environmental fate of pollutants in watershed, soil dissolved organic matter (DOM) sampled from a typical agricultural watershed in the Three Gorges Reservoir area was investigated using ultraviolet-visible (UV-Vis) and fluorescence spectroscopies, to analyze and discuss the effect of different land uses including forest, cropland, vegetable field and residence, on soil DOM geochemical characteristics. The results showed that significant differences in DOM samples amongst different land uses were observed, and DOM from forest had the highest aromaticity and humification degree, followed by DOM from cropland. Although DOM from vegetable field and residence showed the highest dissolved organic carbon (DOC) concentration (average values 0.81 g·kg-1 and 0.89 g·kg-1, respectively), but the aromaticity was lower indicating lower humification, which further suggested that the non-chromophoric component in these DOM samples contributed significantly to total DOM compositions. Additionally, in all DOM samples that were independent of land uses, fluorescence index (FI) values were between 1.4 (terrigenous) and 1.9 (authigenic), evidently indicating both the allochthonous and autochthonous sources contributed to DOM characteristics. Meanwhile, r(T/C) values in most of samples were higher than 2.0, suggesting that soil DOM in this agricultural watershed was heavily affected by anthropogenic activities such as agricultural cultivation, especially, vegetable field was a good example. Additionally, sensitivities of different special spectral parameters for reflecting the differences of DOM characteristics amongst different land uses were not identical. For example, neither spectral slope ratio (SR) nor humification index (HIX) could clearly unveil the various geochemical characteristics of soil DOM from different sources. Thus, simple and single special spectral parameter cannot comprehensively provide the detailed information of DOM, and combined application of UV-Vis and fluorescence spectroscopies is highly recommended.

Keywords

Fluorescence spectroscopy; Soil dissolved organic matter; Three Gorges Reservoir region; UV-Vis spectroscopy; Water-level fluctuation zones

Published in

Huan Jing Ke Xue
2015, volume: 36, number: 3, pages: 879-887
Publisher: Science Press

SLU Authors

• Jiang, Tao

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

UKÄ Subject classification

Soil Science
Agricultural Science

Publication identifier

• DOI: https://doi.org/10.13227/j.hjkx.2015.03.017

Permanent link to this page (URI)

https://res.slu.se/id/publ/132022