Search

Field observations showed that the characteristics of chemical composition of waters and the development of plankton algae in the lakes within the delta of the Selenga river are determined by their flowage. The most open Lake Nekipelovskoe communicates with the Selenga outlets throughout a year, and Lake Zavernyaikha only at the period of an open channel. Lake Semenovskoe and Lake Khlystov Zaton are located in the islands and are isolated from the outlets. According to composition of main ions, the lakes under investigation refer to the hydrocarbonate class, the calcium group. The sum of ions in the water of Lake Nekipelovskoe approaches the one in the Selenga (86−221 mg/dm), and the highest sums of ions were recorded in the wintertime in the lakes isolated from the outlets (446−743 mg/dm). The lakes of the delta are characterized by a high trophicity. The maximum concentrations of total phosphorus in Lake Nekipelovskoe and Lake Zavernyaikha were 68 and 122 μg mg/dm, and in Lake Semenovskoe and Lake Khlystov Zaton −0.8 and −0.63 μg mg/dm, respectively. The most intense development of algae is observed in Lake Zavernyaikha, which is due to the high population of Baikal endemics. Lake Zavernyaikha showed a close negative correlation between the concentration of NO, mineral phosphorus and phytoplankton biomass; the correlation coefficient was −0.8 and −0.63, respectively. The lakes exhibited increased contents readily hydrolysable organic matter, and a decrease in dissolved oxygen concentration in winter; hydrogen sulfide was repeatedly recorded in Lake Khlystov Zaton. The water quality in the lakes during the springtime varies from 'quite clean' to 'weakly polluted'; at low-water periods, especially in winters, it can drop to the category of 'exceedingly dirty'. The water quality of the Selenga can be influenced by the lakes during spring floods when material accumulated during the wintertime is transported to the river outlets and further to Lake Baikal. [ABSTRACT FROM AUTHOR]

A microwave digestion procedure with the use of specially designed autoclaves and a domestic microwave oven is proposed for the mass-spectrometric determination of the elemental composition of bottom sediments. The throughput of sample preparation in routine analysis was considerably increased because of the elimination of a purification step. Reaction mixture compositions and microwave digestion conditions were chosen to reach complete decomposition (within the limits of error of semiquantitative ICP MS analysis) of Baikal bottom sediments with respect to the majority of elements. It was found that the procedure is unsuitable for the determination of Sn, Zr, Nb, Hf, As, and Sb. The approximate concentrations of elements in a BIL-1 certified reference material of Baikal bottom sediments were found: Tl, 0.52 ± 0.16 ppm; Bi, 0.33 ± 0.10 ppm; I, 14.3 ± 4.3 ppm; Cd, 0.31 ± 0.09 ppm; and Pb, 0.24 ± 0.07 ppm. [ABSTRACT FROM AUTHOR]

Abstract: A new experimental method for the determination of the isotopic composition of authigenic uranium in Lake Baikal (Siberia) sediments has supplied a record of (234U/238U)aut ratios during the past 150ka with a resolution of ca. 200years. Reconstruction of the (234U/238U)aut activity ratio as a proxy for lake water composition shows that the uranium isotope disequilibrium has not stayed constant throughout this period: it varied greatly in response to regional climate. The 234U/238U activity ratio in Lake Baikal paleowaters was inferred to be high during interglacial time (∼1.85–2 during MIS 5.5 and the Holocene; ∼1.4–1.7 during MIS 5.1 and 5.3) and dropped to ∼1.16±0.01 during glacial time. The variability in the deduced 234U/238U ratios of Lake Baikal waters of the past may have been caused by the climatically-modulated redistribution of contributions of riverine discharges from different provinces of the very large catchment of the lake. Aridity during ice ages was more pronounced in the south of eastern Siberia and in northern Mongolia relative to that in the northern regions of the Lake Baikal watershed. The southern contribution of riverine input into the lake was essentially absent during glacial periods. Records of some elements (Ca/K, Sr/Rb, Si/Al, La/Th, U/Th, CIW) from the bottom sediments of Lake Baikal during the last 0.5Myr with a resolution of ∼2kyr have also been obtained. Coupling these data with records of weathering indices shows that not only riverine waters but also terrigenous material delivered into Lake Baikal from different regions of the very large watershed during interglacial and glacial times. Glacial erosion delivered fine siliciclastic material (“glacial milk”) mainly from the nearest mountain glaciers situated in the northwestern region of Lake Baikal while during warmer periods terrigenous material was sourced from the surrounding river valleys. A conceptual model for the simulation of the fluvial discharge gradient between the northern and southern provinces of the Lake Baikal watershed is proposed and a first-order simulation of past changes in the contribution of the Selenga River to the lake water budget is given. [Copyright &y& Elsevier]