Applicability of Fluorescence Analysis of Sedimentary Porewater Humic Substances for Reconstructing Past Lake Conditions

Abstract

Fluorescence properties of sediment porewater humic substances collected from ten Estonian lakes with various trophy were investigated to reveal if they infer the lake’s past productivity and origin of sedimentary organic matter. The height (fluorescence intensity), location (fluorescence maximum) and shape (fluorescence index, the ratio of intensities at the emission wavelengths 450 and 500 nm) of the fluorescence emission spectrum at an excitation of 340 nm were under consideration. The study demonstrated that humic substances from sediments of eutrophic lakes were generally characterized by high fluorescence intensity and fluorescence index, and their fluorescence maximum was located at shorter wavelengths. Humic substances from sediments of oligotrophic lakes were characterized by low fluorescence intensity. Humic substances from sediments of dystrophic lakes had low fluorescence intensity and fluorescence index values, and their spectral peak was shifted to longer wavelengths. The obtained results suggest that the method has a great potential in retrospective analysis of lake ecosystems.