ИСТИНА

The study of Kunashir Island is of significant importance due to its unique ecological and geological characteristics, particularly its proximity to active volcanoes and diverse water bodies. By examining the hydrochemistry parameters and optical properties of dissolved organic matter (DOM) in these reservoirs using UV-vis analysis, fluorescence spectroscopy, and organic carbon measurements, this research seeks to uncover volcanic influences on DOM composition of water samples obtained in the Kunashir Island. The primary aim is to compare the optical and hydrochemistry characteristics of DOM from volcanic sources with those of other water bodies on Kunashir Island. The objective of this study was comparison of water properties of rivers and lakes of Kunashir Island and volcanic influence on them. Samples were collected in the summer of 2024 from Rubezhny Creek (N 44.32138°, E 146.28416°), Goryachee and Kipyashchee Lakes (N 43.86349°, E 145.50617° and N 43.86349°, E 145.49891°, respectively), and from the Lesnaya (N 44.00112°, E 145.70699°) and Filatovka (N 44.19108°, E 146.01891°) Rivers. The water reservoirs are situated in proximity to the Golovnin, Mendeleyev, and Tyatya volcanoes. Specifically, Kipyashchee and Goryachee lakes are located near the Golovnin volcano, while the Lesnaya and Filatovka rivers and the Rubezhny stream is less influenced by volcano activity. Thus, the study encompasses reservoirs located near the active volcanoes of the Greater Kuril Ridge. The optical properties of the natural water samples were investigated after filtration through a GFF filter with a pore size of 0.7 μm. Fluorescence spectroscopy and UV-Vis spectrometry were utilized to analyze the samples providing insights into the optical characteristics of DOM present in various water sources. Additionally, the total organic carbon (TOC) content of the samples was measured using a TOC-L analyzer. The analysis revealed a broad range of TOC concentrations: 4.99 ± 0.01 mg/L in the Lesnaya River, 1.95 ± 0.33 mg/L in Rubezhny Creek, 0.95 ± 0.025 mg/L in Lake Goryachee, 3.26 ± 0.03 mg/L in Lake Kipyashchee, and 1.02 ± 0.99 mg/L in the Filatovka River. Furthermore, key hydrochemistry parameters including pH and oxidation-reduction potential (Eh) values were measured to assess the geochemical conditions of these water bodies. The pH values exhibited notable variation across the different sites ranging from neutral to slightly alkaline in the Lesnaya (8.15) and Filatovka (7.03) rivers, mildly acidic in Rubezhny Creek (6.03), to highly acidic conditions in Lake Goryachee (2.79) and Lake Kipyashchee (2.29), likely as a result of volcanic activity in the region. Since the water bodies of Kipyachiye and Goryachee lakes are stagnant in volcanos mouths, the large amount of sulphur, in form of sulphates, bisulphates, thiosulphates, polythionates and sulphuric acid can be released into the water and further influence the optical and hydrochemistry parameter, which leads to decrease of the pH values. Acknowledgements. This research was carried out within the framework of the state task “Ecology” (CITIS no. 122040600057-3).