Vol. 9, No. 1, 13-21, 2010

The "blue shift" of emission maximum and the fluorescence quantum yield as quantitative spectral characteristics of dissolved humic substances
Daria Shubina, Elena Fedoseeva, Olga Gorshkova, Svetlana Patsaeva, Vera Terekhova, Mikhail Timofeev, and Viktor Yuzhakov

Humic substances (HS) play important roles in a variety of biogeochemical processes. Fluorescence spectra can be used for quantitative and qualitative characterisation of water-soluble humic substances (HS) and, in particular, of dissolved organic matter (DOM) in water. In this study, we measured the fluorescence spectra of natural HS (riverine, lake, marine water, and soil aqueous extractions) and commercial water-soluble HS under excitation from 270 to 355 nm. Natural water samples were filtered in two stages by micro- and ultra-filtration. After ultra-filtration, DOM was separated into two fractions depending on the size of the particles, for which fluorescence spectra were also obtained. The comparative analysis was made with a focus on the so-called "blue shift" (emission maximum shifts towards shorter wavelengths with increasing excitation wavelength) and the fluorescence quantum yield (QY) of samples of different origin. The fluorescence quantum yield under excitation at 355 nm for commercial HS (QY=0.008) was less than that for natural water DOM (QY=0.028), but more than for soil HS (QY=0.003). The low molecular weight fraction quantum yield was bigger than that for the colloidal fraction by 20-30%. The fluorescence quantum yield for natural water and for soil extractions HS increased with excitation wavelength, but the quantum yield did not depend on the excitation wavelength for commercial HS samples. Natural HS differed from commercial HS in higher heterogeneity of fluorophore composition as evidenced by the larger "blue shift" value and QY dependence on excitation wavelength.

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Submitted: 1 July 2009
Revised: 20 Nov 2009
Accepted: 12 Feb 2010
Published: 12 Mar 2010
Responsible editor: Rainer Reuter

Shubina D, E Fedoseeva, O Gorshkova, S Patsaeva, V Terekhova, M Timofeev & V Yuzhakov, 2010. The "blue shift" of emision maximum and the fluorescence quantum yield as quantitative spectral characteristics of dissolved humic substances. EARSeL eProceedings, 9(1): 13-21


EARSeL European Association of Remote Sensing Laboratories, Strasbourg, France


BIS Library and Information System, Carl von Ossietzky University of Oldenburg


ISSN 1729-3782