BOTTOM SEDIMENTS NEAR THE KUIBYSHEV RESERVOIR DAM (ACCORDING TO THE DATA OF THE 2020 EXPEDITION RESEARCH)
The composition of bottom sediments and the patterns of their spatial distribution are determined by external (type of underlying surface of the catchment area, anthropogenic development, intensity of soil erosion) and internal (water regime, intensity of water exchange, morphometry of the basin) factors. As a result of the expedition studies of the IEVB RAS in the autumn period from September 14 to October 3, 2020, samples of bottom sediments were collected at 21 stations near of Kuibyshev reservoir dam in a 10-centimeter layer. Based on the results of the granulometric analysis and assessment of the organic matter content in the bottom sediment samples, integral granulometric curves were constructed and the spatial distribution of different characteristics of the bottom sediments was analyzed such as the percentage of organic matter in the samples, the interquartile range and the median value of the bottom sediment size at the studied sampling points. The analysis showed that the largest differences in the percentage of particles in the samples of the studied stations (over 60%) are accounted for by particles with a size of about 0,1 mm. Sampling stations located closer to the right bank are characterized by a smaller size of the bottom sediment soil than stations near the left bank. This is due to the fine-grained erosion products of the catchment area is characterized by a relatively uniform granulometric composition of bottom sediments, also mainly by dusty-sand fractions. More uniform in size soil is observed along the right bank - fine products of erosion of sandstones and dolomites of the right bank. The larger interquartile range characterizes the samples taken along the longitudinal profile of the reservoir dam reach and near the left bank in the shallow water zone. In this area of the water area, which is genetically composed of sands and mineral silts, due to the favorable temperature regime and the peculiarities of the circulation of water masses, intensive organic sedimentation processes occur. On average, for the dam reach the content of organic matter in the bottom sediments is 1,1%, which is in good agreement with the data of other researchers.