Composition and physico-chemical properties of bottom sediments in the southern part of the Bratsk Reservoir (Russia)

Abstract

The paper presents the results of studies of bottom sediments taken from the southern part of the Bratsk Reservoir. The following analyses have been conducted: trace element analysis, particle-size analysis as well as chemical analysis of water, hydrochloric acid and alkaline extracts for 18 samples of the bottom sediments. The granulometric analysis has identified the predominance of fine silt and silty-clayed sediments. The data on the content of trace elements in the bottom sediments of the Bratsk Reservoir is presented in comparison with their content in the natural environment of the Baikal region; the anomaly ratio was used to characterize the excess for trace elements. The chemical analysis of extracts has showed “saline contamination” of mud (silt), high concentration of carbonates in it, as well as the presence of mobile (free) forms of aluminum oxide. In this research, an attempt was made by using a correlation analysis to evaluate the impact of various physical and chemical characteristics of the bottom sediments, such as the content of clay fraction, organic carbon, carbonates, and water-soluble salts on the accumulation of trace elements.

Water-Sediment Physicochemical Dynamics in a Large Reservoir in the Mediterranean Region under Multiple Stressors

“…The sediment particle size has a great influence on the distribution of natural and anthropogenic elements, as organic matter, nutrients and metals, showing usually high affinity to fine particles (<0.063 nm) [26,27,64]. These compounds may be released from the sediments to the bottom phase of the water column under specific limnological conditions.…”

Hydrochemistry of sediment pore water in the Bratsk reservoir (Baikal region, Russia)

“…1 c). The composition of the Bratsk bottom sediments on the site from Svirsk to Unga Bay revealed that the total content of carbonates, with a predominance of CaCO 3 and MgCO 3 , averaged to 24% 19 . With time, the sediment-forming terrigenous material underwent leaching that resulted in the increase of Ca 2+ , Mg 2+ , HCO 3 − and SO 4 2− concentrations in the Bratsk reservoir pore water.…”

“…3 , 4 ) indicate that the bottom sediments undergo reduced diagenetic transformations whose intensity depends on the amount of organic matter 54 . In the Bratsk Reservoir bottom sediments, on the site from Svirsk to Unga Bay, the organic carbon content is on average, 5.60%, with its highest concentration in the bottom sediments of the bays (to 17.7%) 19 . It should be noted that large amounts of organic materials were brought during the reservoir filling when 166 thousand hectares of agricultural land and 135.2 thousand hectares of forest were flooded 22 .…”

“…Amongst the cascade reservoirs, the Bratsk, the second of the cascade, whose filling was completed in 1967, is considered the most technogenically stressed. Despite the great amount of information concerning the elemental composition of water 16 , 17 , bottom sediments 18 , 19 , and biota 20 of the Bratsk reservoir, pore water chemistry remains an insufficiently studied geochemical sector. The pore water studies performed in the 1980s during the initial period of reservoir operation 21 included only the determination of main cations (Na + , K + , Ca 2+ , Mg 2+ ) and biogenic components (NO 3 – , SiO 2 – , PO 4 3– ) in the pore solution.…”

Hydrochemistry of sediment pore water in the Bratsk reservoir (Baikal region, Russia)

“…However, water ow slowdown and changes in sedimentation conditions after the river ow reservoirs, the Bratsk, the second of the cascade, whose lling was completed in 1967, is considered the most technogenically-stressed. Despite there is great amount of information concerning the elemental composition of water [16][17][18], bottom sediments [19,20] and biota [21] of the Bratsk reservoir, yet, the pore water chemistry remains an insu ciently studied geochemical sector. The pore water studies, done in 1980ies, the initial period of the reservoir operation [22], included only the determination of main cations (Na + , K + , Ca 2 + , Mg 2+ ) and biogenic components (NO 3 -, SiO 2 -, PO 4 3-) in the pore solution.…”