Kozhevnikova N.K., Boldeskul A.G., Lutsenko T.N., Yurchenko S.G., Elovskiy E.V.
Hydrosphere. Hazard processes and phenomena 2025; 7(1): 10-34
This article presents the results of assessing the input of chemical components with rains and their output with river waters in contrasting watershed moisturizing. The analysis was performed on the field data of the summer - autumn periods of 2014-2022 in the stream basins forming the river flow of the fourth order. Based on the relationship between concentrations and water discharge, the paper discusses the possible causes of different dynamics and behavior of dissolved substances during export from ecosystems to the streams. Atmospheric precipitation is the low-mineralized slightly acidic solutions the main component of which is dissolved organic carbon. In wet years, the input of mineral components was 18 % higher than in relatively dry years, while organic components were 44 % higher. River catchments differ in the landscape factors and exhibit different sensitivity to humidification. Differences in the dissolved substances behavior are determined by seasonal changes and by the mixing of various water sources. In the streams the dissolved organic carbon and sulfates are identified as the most dynamic to hydrological changes, while chlorides, potassium, silicon, and phosphorus demonstrate more static behavior. The difference between the waters of neighboring basins is established for nitrate, aluminum, iron, and manganese. The main source of them is the soils and plants, as well as for calcium, magnesium, and sodium, which mainly come from soils and groundwater. It is shown that the highest element concentrations are observed in the low water period of the year, and organic components - in the high-water period. At the same time, in high-water years, the export of mineral components increases up to 14-67 %, and organic components up to 24-100 % compared to the annual average. Dissolved calcium, silicon, and inorganic carbon make up the bulk of the carried mineral components. Regardless of the moisture, the largest contribution of dissolved mineral components to the river flow is made by the waters of a third-order tributary, in the catchment of which there are highly weathered Jurassic rocks of the basic composition. In the waters of this stream a slight dominance of dissolved organic carbon was revealed only in the high-water years. The basin with a high proportion of indigenous coniferous forests the soils of which are formed on acidic rocks resistant to weathering, exports the largest amount of dissolved organic carbon (0.1-2.0 t/km2) and N-NO3 (0.1-0.2 tN/km2). In the waters of a third-order stream, a slight dominance of dissolved organic carbon was found only in years of increased water levels.
