The optical properties of chromophoric dissolved organic matter (CDOM) of natural water have been studied by fluorescence spectroscopy and absorption spectroscopy. Samples of natural water from various depths from the meromictic lakes Trekhtzvetnoe and Elovoe were taken. The dependences of the quantum yield and the maximum of fluorescence emission on the excitation wavelength in a wide range of excitation wavelength variation (250...500 nm) for different horizons of stratified reservoirs are obtained. It is shown that the dependences of the maximum of the fluorescence emission on the excitation wavelength and the dependences of fluorescence quantum yield on the excitation wavelength in both lakes and at all depths studied are similar. On the other hand, the absolute value of the quantum yield differs in different layers of water. For example, the values of the fluorescence quantum yield took values from 1.4% to 2.4% at an excitation wavelength of 340 nm. The similar nature of the dependence of the fluorescence intensity on the excitation wavelength is explained by the common origin of DOM fluorophores in the studied horizons of stratified lakes. The different values of the fluorescence quantum yield are due to the difference in the proportion of aromatic compounds in the composition of the CDOM and are associated with differences in the hydrochemical characteristics of water at different horizons.
Chlorosomal bacteriochlorophylls are the main photosynthetic pigments of green sulfur bacteria – anoxygenic phototrophic microorganisms. The spectral properties of chlorophylls of higher plants, algae and cyanobacteria are well studied, however, the spectral-luminescent properties of their related compounds, bacteriochlorophylls, which participate in anoxigenic photosynthesis, are practically not described in the scientific literature. The polarity of the solvent and the environment have a significant effect on the emission spectra (bacterio)chlorophylls, which is expressed in the spectral shift of the absorption and fluorescence maxima, as well as changes in the fluorescence intensity. The spectral characteristics of bacteriochlorophylls d and e were obtained in organic solvents such as acetone, methanol, ethanol and isopropanol, as well as in acetone-ethanol (7:2) and acetone-methanol (7:2) mixtures. These solvents are most often used for the extraction of bacteriochlorophylls from bacterial cells, so the work will be useful for the development of methods for the quantitative determination of chlorosomal bacteriochlorophylls in bacterial cells or in samples of natural water.
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