Siliceous microfossil distribution in the surficial sediments of Lake Baikal

Examination of surficial sediments at 16 stations shows minor, but consistent differences in the numbers and kinds of siliceous microfossils deposited in different regions of Lake Baikal. There is a general north-south decreasing trend in total microfossil abundance on a weight basis. Endemic plankton diatom species are the most abundant component of assemblages at all stations. Chrysophyte cysts are present at all stations, but most forms are more abundant at northern stations. Non-endemic plankton diatom species are most abundant at southern stations. Small numbers of benthic diatoms and sponge spicules are found in all samples. Although low numbers are present in offshore sediments, the benthic diatom flora is very diverse. Principal components analysis confirms primary north-south abundance trends and suggests further differentiation by station location and depth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43071/1/10933_2004_Article_BF00682594.pd

(Table) Bacterial counts and Fe, Mn and SO4 content in sediments and pore waters of two cores from Lake Baikal

Sediments at the bottom of Lake Baikal are mostly oxidized at their surface, and the oxidized sedimentary deposits are enriched in Fe and Mn hydroxides. The thickness of the oxidized zone of the pelagic sediments averages at 5 cm and locally reaches 10-15, occasionally exceeding 20 cm. Both the thickness of the oxidized layer and the degree of its enrichment in iron and manganese hydroxides are controlled by the depth to which oxygen can penetrate into the sedimentary deposits, which is, in turn, closely related to the sedimentation conditions in the lake (which broadly vary). The sedimentation rate far off the shores of Lake Baikal ranges from 4%. The variability of the sedimentation process makes Lake Baikal very convenient to study its diagenetic processes related to redox reactions in sediments, first of all, processes responsible for the redistribution of Fe and Mn compounds. Although the diagenetic enrichment of Fe and Ni in bottom sediments is known to be of biogenic character, very scarce information is available so far on the microorganisms involved in the redistribution of these elements in sediments in Lake Baikal, which lately led us to explore this issue in detail. Our research was centered on the role played by the microbial community in the diagenetic transformations of Fe and Mn with reference to sedimentation conditions in Lake Baikal

Eh and pH values in sediments and composition of interstitial waters from the Frolikha Bay, Baikal Lake

Redox conditions and compositions of bottom sediments and sedimentary pore waters in the area of the hydrothermal vent in the Frolikha Bay (Baikal Lake) are under discussion. According to obtained results, the submarine vent and its companion spring nearby on the land originate from a common source. The most convincing evidence for their relation comes from proximity of stable oxygen and hydrogen isotope compositions in the pore waters and spring water. The isotope composition indicates meteoric origin of the pore waters, but their major- and minor element compositions have influence of deep water, which may seep through the permeable faulted crust. Although the pore waters near the submarine vent have specific enrichment in major and minor constituents, hydrothermal discharge at the Baikal bottom causes minor influence on water composition of the Baikal Lake, unlike freshwater lakes in rifts of the East Africa and North America

Vivianite formation and distribution in Lake Baikal sediments

International audienc

Determination of content and valence state of iron and manganese in nodules usind K-series emission lines of X-ray fluorescence spectrum

Исследована возможность одновременного определения содержания железа и марганца, а также оценки отношений концентраций С(FeO)/С(Fe₂O₃общ) и С(MnO₂)/С(MnOобщ) по K-серии рентгеновского флуоресцентного спектра в железомарганцевых конкрециях. Измерения выполнены на спектрометре S4 Pioneer. Относительное стандартное отклонение определения содержания общего марганца составило 1.1 %, общего железа - 3.9 %. В качестве аналитического сигнала при определении валентного состояния железа и марганца использовали отношение интенсивностей линий IKβ₂,₅/IKβ₁,₃. Стандартное отклонение определения отношения C(MnO₂)/C(MnOобщ) для выборки стандартных образцов железомарганцевых конкреций составило 0.03 для величины отношения 1.16-1.23. Относительное стандартное отклонение определения содержания MnO₂ составило 1.8 % для диапазона содержания MnO₂ 24.30-40.80 мас. %. Стандартное отклонение определения отношения С(FeO)/С(Fe₂O₃общ) для выборки образцов минералов и оксидов железа составило 0.07. Оценка валентного состояния подтвердила, что железо и марганец в образцах железомарганцевых конкреций содержится преимущественно в окисленном состоянии (Fe³⁺ и Mn⁴⁺). Преимуществами метода РФА являются низкие затраты на пробоподготовку и возможность одновременного определения содержания железа и марганца.This study was performed to search for the possibility to determine iron and manganese contents and to assess the C(FeO)/С(Fe₂O₃tot) and C(MnO₂)/С(MnOtot) ratios in nodules using K-series of X-ray fluorescence (XRF) spectrum. The measurements have been implemented by spectrometer S4 Pioneer. The relative standard deviation of MnOtot content was 1.1 %. The relative standard deviation of Fe₂O₃tot content was 3.9 %. The standard deviation of C(MnO₂)/C (MnOtot) for the set of standard samples of nodules was 0.03 for the range of ratio 1.16-1.23 %. The relative standard deviation of MnO₂ content was 1.8 % for the range of MnO₂ content 24.30-40.80 %. The standard deviation of C(FeO)/C(Fe₂O₃tot) for set of minerals and iron oxides was 0.07. The estimation of valence state proved that iron and manganese are mainly in high valence state in nodules (Fe³⁺ and Mn⁴⁺). The XRF method is preferred, for it is fast and convenient for sample preparation. This method allows to determine iron and manganese contents simultaneously