Synchronous fluorescence spectra of natural waters: tracing sources of dissolved organic matter

Environmental contextDissolved organic matter (DOM) plays an important role in influencing the migration and ultimate fate of metals. Different sources of pollution resulted in changes in the structure of sediment DOM in Lake Wuliangsuhai. We investigate the binding properties of DOM with CuII and HgII using fluorescence quenching combined with two-dimensional correlation spectroscopy (2D-COS) in order to demonstrate the influence of different sources of DOM on metals. AbstractDissolved organic matter (DOM) was collected from three sampling sites (L1, L2 and L3) in Lake Wuliangsuhai. L1 received upstream industrial wastewater and domestic sewage. L2 had suffered from agricultural non-point source pollution. L3 was situated in the lake outlet area. The complexation of DOM with CuII and HgII was investigated based on fluorescence quenching of the synchronous fluorescence spectra on the addition of CuII and on two-dimensional correlation spectroscopy (2D-COS). The synchronous and asynchronous maps derived from 2D-COS provided a clear picture of the heterogeneous distribution of CuII and HgII binding sites, which was not readily detected using only the synchronous fluorescence spectra. CuII and HgII complexation was stronger at shorter wavelengths than at longer wavelengths. Moreover, fluorescence quenching also occurred intensely in the fulvic-like regions (363nm for DOM-Cu in L2 and 365nm for DOM-Hg in L1). The logarithms of the stability constants (log KM) ranged from 4.42 to 6.23, from 4.75 to 4.86, and from 4.80 to 5.73 for DOM-Cu in L1, L2 and L3, respectively, depending on the wavelength. DOM at the longer wavelengths exhibited a higher log KM than that at the shorter wavelengths, and the f values in the protein-like region were clearly high. These results suggest that the influence of the structural and chemical properties of DOM on CuII binding may differ for DOM from different sources. The combined approach of fluorescence quenching and 2D-COS could be applied as a tool for evaluating the metal binding site heterogeneity of DOM.

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Synchronous fluorescence spectra of natural waters

Deep Sea Research Part B Oceanographic Literature Review ◽

10.1016/0198-0254(87)95886-9 ◽

1987 ◽

Vol 34 (12) ◽

pp. 1038

Keyword(s):

Fluorescence Spectra ◽

Natural Waters ◽

Synchronous Fluorescence ◽

Synchronous Fluorescence Spectra

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Synchronous Fluorescence Spectra as Chemical Tracers to Monitor the Organic Matter Dissolved in North Adriatic Waters

Mediterranean Ecosystems ◽

10.1007/978-88-470-2105-1_16 ◽

2001 ◽

pp. 115-122

Author(s):

M. Mingazzini

Keyword(s):

Organic Matter ◽

Fluorescence Spectra ◽

Synchronous Fluorescence ◽

Chemical Tracers ◽

Synchronous Fluorescence Spectra

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Photochemical effects on the interaction of enzymes and dissolved organic matter in natural waters

Limnology and Oceanography ◽

10.4319/lo.2003.48.5.1818 ◽

2003 ◽

Vol 48 (5) ◽

pp. 1818-1824 ◽

Cited By ~ 23

Author(s):

Norman M. Scully ◽

Lars J. Tranvik ◽

William J. Cooper

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Natural Waters

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Optical Properties of Dissolved Organic Matter in Finnish and Estonian Lakes

Hydrology Research ◽

10.2166/nh.2003.0012 ◽

2003 ◽

Vol 34 (4) ◽

pp. 361-386 ◽

Cited By ~ 14

Author(s):

L. Sipelgas ◽

H. Arst ◽

K. Kallio ◽

A. Erm ◽

P. Oja ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Natural Waters ◽

Mean Value ◽

Published Data ◽

Optical Parameters ◽

Exponential Approximation ◽

Absorption Coefficients ◽

Specific Absorption ◽

The Mean

The main objective of the present study is to test various methods for describing the absorption spectra of coloured dissolved organic matter (CDOM) and to determine the numerical values of some optical parameters of CDOM in lakes with diverse water quality. First, the parameters of an exponential model in different spectral intervals were determined. In addition, the suitability of some other models for the approximation of CDOM spectra was estimated. Specific absorption coefficients of CDOM were calculated from the absorption coefficients and dissolved organic carbon (DOC) concentrations. The experimental initial data were differences between spectral attenuation coefficients of filtered and distilled water. Two datasets were used: 1) for 13 Estonian and 7 Finnish lakes (altogether 404 spectra between 350 and 700 nm) measured by the Estonian Marine Institute (EMI); 2) for 10 Finnish lakes (73 spectra) measured by the Finnish Environment Institute (FEI). The spectra of CDOM absorption coefficients (aCDOM) were calculated from experimental data taking into account the correction due to scattering properties of colloids in the filtered water. The total content of CDOM in natural waters of Estonian and Finnish lakes was expressed by means of aCDOM at the wavelength of 380 nm. It varied significantly, from 0.71 to 19.5 m−1, the mean value (of all the investigated lakes) being around 6.6 m−1. Slopes of the exponential approximation varied widely, from 0.006 to 0.03 nm−1. Averaged over all lakes values of slope for the interval 380-500 nm obtained from the EMI dataset are close to those obtained from the FEI dataset: from 0.014 nm−1 (without correction) to 0.016-0.017 nm-1 (with different types of correction). These results are in good correspondence with most published data. Attempts to describe the spectra in the region of 350-700 nm by means of hyperexponential functions (∽ exp(-αλη)) show that: (1) η < 1 (in the case of traditional exponential approximation η = 1); (2) a promising idea is to seek the best fit only for wavelengths λ > λ1, where λ1 will be chosen taking into account the real shape of aCDOM spectra. The mean value of the specific absorption coefficient (a*CDOM) at the wavelength 380 nm obtained in this study (0.44 L mg−1 m−1) is close to the values published in the literature, if we assume that a*CDOM (380) is calculated using the data of dissolved organic matter (DOM). The optically non-active fraction of DOM in our study was high and therefore a*CDOM (380) was considerably higher (1.01 L mg−1 m−1) than a*CDOM (380). The results of the present work could be used in the modeling of underwater light field as well as in the interpretation of radiation measurements and optical remote sensing results.

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