Abstract:
The optical properties of dissolved organic matter (DOM) of natural water have been studied by fluorescence spectroscopy and absorption spectroscopy. Samples of natural water were taken as objects from different depths of the Tryokhtsvetnoe and Yelovoe meromictic lakes. Dependences of the quantum efficiency and maximum of fluorescence emission on the excitation wavelength were obtained for the first time in a wide range of excitation wavelengths (250–500 nm) for different layers of stratified water bodies. It is shown that the dependence of maximum of the fluorescence emission band on the excitation wavelength and the dependence of the fluorescence quantum efficiency on the excitation wavelength in both lakes and at all studied depths have similar behavior, however, the absolute value of quantum efficiency differs in different water layers. For example, fluorescence quantum efficiencies were from 1.4% to 2.4% at an excitation wavelength of 340 nm. The similar behavior of the fluorescence intensity dependence on the excitation wavelength is explained by the common origin of DOM fluorophores in the under-study layers of stratified lakes. Different values of the fluorescence quantum efficiency are due to the difference in the proportion of aromatic compounds in the composition of DOM and are related to the difference in the hydrochemical characteristics of water at different layers.