Grain-Size Composition of Bottom Sediments of the Simmy River in the Bolon Nature Reserve

Resumo

The composition of bottom sediments in the Simmy River (the Amur River tributary, the Bolon Nature Reserve, Khabarovsk krai, Russia) was studied using laser diffractometry, sedimentation analysis, and electron microscopy. It was found that the grain-size composition of sediments from the area treated was mainly constituted by small-size grains and characterized by the accumulation of fine sand which conformed to lacustrine–alluvial genesis of the territory. The sediments in the near-mouth area were mainly formed by particulate alluvium with prevailing silty fraction. The definitive effect on the composition of sediments is exerted by hydrological conditions of Lake Bolon receiving the riverine waters: the variations in the lake water level conform to those in the Amur River. It was shown that the coagulation and precipitation of suspended solids at low content of organic matter (below 1%) resulted in the appearance of volume-aggregated dense and viscous sediments. A higher content of organic matter (>6% in the Kirpu tributary of the Simmy River) caused the “nodal” differentiation of volume-aggregated spatial structures to form porous microaggregates.