Zemfira Tyugai

The texture of bottom sediments of the Simmy River and its tributaries in the area of the “Bolon'sky” reserve (Khabarovskiy region, Far East) was studied with methods of laser diffractometry, sedimentation and electron microscopic analysis. It was found out that the texture of Simmy sediments in downstream is characterized by the accumulation of fine sand, which corresponds to alluvial-lake genesis of the studied area. In the wellhead part of river sediments are formed mainly by suspended sediments with a predominance of the clay fraction. This is due to the impact of the floodplain Bolon Lake, which level fluctuations correspond to changes in the level of water in the Amur River. It is shown that coagulation and deposition of suspended particles with low content of organic matter (< 1%) leads to the formation of volumetric aggregated, dense and viscous sediments. The high content of organic matter in sediments (> 6%, the Kirpy River, the tributary of the Simmy River) leads to the “nodal” differentiation of spatial structures and to the formation of porous microaggregates.

The composition of bottom sediment in the estuarine part of the Simmi River, a small tributary of the Amur River (Bolon State Nature Reserve, Russian Far East), was studied using X-ray fluorescence, electron microscopy, sedimentation analysis, and laser diffractometry. It is established that the formation of labile components in the bottom sediments (vivianite–clay microaggregates, gypsum microcrystals, and vaterite mesocrystals) is linked with effects of the pyrogenous factor in the Simmi River basin and the level regime of the main river. The formations are mobile due to their small size (<100 μm). The bottom deposits are primarily formed by such suspended sediments (particle size <100 μm), which is consistent with the lacustrine–alluvial genesis of the area. Two vivianite formation mechanisms have been identified in the bottom sediments in periods following fires, when the concentration of phosphate ions in the river water is elevated. Vivianite is formed on the surface of ferruginous–clay microaggregates, due to the reduction of Fe (III) in the presence of organic matter and on biological templates (organic residues and single-celled microorganisms).