The comparison of spectral and optical properties of dissolved organic matter of the Lake Kislo-Sladkoe in the winter and summer seasons.

Abstract

Meromictic water bodies are of particular interest for studying the composition and
distribution of coloured dissolved organic matter (CDOM). These water bodies
have a stable vertical stratification arising from the difference in density of water
layers. In such water bodies, starting from a certain depth, an oxygen-free zone is
usually present. At the upper boundary of which, with a sufficient amount of
penetrating sunlight, an outbreak of anoxygenic phototrophic bacteria occurs. It is
known that the optical properties of natural water significantly depend on the
composition and concentration of CDOM, which affects the functioning of aquatic
ecosystems, therefore, the study of CDOM in different horizons of stratified water
bodies is important for understanding their evolution. A CDOM of natural origin
effectively absorbs UV light and luminesces, therefore, light absorption
spectroscopy and fluorescence spectroscopy are currently widely used for its study.
The purpose of this work is to study the optical properties of CDOM of natural
water on the example of a meromicitic lake of the White Sea coast (Lake Kislo-
Sladkoe). Water samples were taken in January, March and June 2024. To study
the CDOM, the samples were filtered through nylon filters with a pore diameter of
0.22 microns. Light absorption spectra, fluorescence emission spectra and
synchronous fluorescence spectra were measured. The fluorescence emission
spectra carry information about the concentration of CDOM in water from a given
depth, and synchronous fluorescence spectra show the heterogeneity of the CDOM
composition.

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Anastasia Denisovna Tsvetkova
Faculty of Physics, M.V.Lomonosov Moscow State University, Moscow
Russia

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