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31.
Biogeochemistry of the Russian Arctic. Kara Sea: Research results under the SIRRO project, 1995–2003
E. M. Galimov L. A. Kodina O. V. Stepanets G. S. Korobeinik 《Geochemistry International》2006,44(11):1053-1104
The Kara Sea is an area uniquely suitable for studying processes in the river-sea system. This is a shallow sea into which
two great Siberian rivers, Yenisei and Ob, flow. From 1995 to 2003, the sea was studied by six international expeditions aboard
the R/V Akademik Boris Petrov. This publication summarizes the results obtained, within the framework of this project, at the Vernadsky Institute of Geochemistry
and Analytical Chemistry, Russian Academy of Sciences. Various hydrogeochemical parameters, concentrations and isotopic composition
of organic and carbonate carbon of the sediments, plankton, particulate organic matter, hydrocarbons, and dissolved CO2 were examined throughout the whole sea area at more than 200 sites. The δ13C varies from −22 and −24‰ where Atlantic waters enter the Kara Sea and in the North-eastern part of the water area to −27‰
in the Yenisei and Ob estuaries. The value of δ13C of the plankton is only weakly correlated with the δ13C of the organic matter from the sediments and is lower by as much as 3–4‰. The paper presents the results obtained from a
number of meridional river-sea profiles. It was determined from the relations between the isotopic compositions of plankton
and particulate matter that the riverwaters carry material consisting of 70% detrital-humus matter and 30% planktonogenic
material in the river part, and the material contained in the off-shore waters consists of 30% terrigenous components, with
the contribution of bioproducers amounting to 70%. The carbon isotopic composition of the plankton ranges from −29 to −35‰
in the riverine part, from −28 to −27‰ in the estuaries, and from −27.0 to −25% in the marine part. The relative lightness
of the carbon isotopic composition of plankton in Arctic waters is explained by the temperature effect, elevated CO2 concentrations, and long-distance CO2 supply to the sea with riverwaters. The data obtained on the isotopic composition of CO2 in the surface waters of the Kara Sea were used to map the distribution of δ13CCO
2. The complex of hydrocarbon gases extracted from the waters included methane, C2–C5, and unsaturated C2=–C4= hydrocarbons, for which variations in the concentrations in the waters were studied along river-estuary-sea profiles. The
geochemistry of hydrocarbon gases in surface fresh waters is characterized by comparable concentrations of methane (0.3–5
μl/l) and heavier hydrocarbons, including unsaturated ones. Microbiological methane with δ13C from −105 to −90‰ first occurs in the sediments at depths of 40–200 cm. The sediments practically everywhere display traces
of methane oxidation in the form of a shift of the δ13C of methane toward higher values and the occurrence of autogenic carbonate material, including ikaite, enriched in the light
isotope. Ikaite (δ13C from −25 to −60‰) was found and examined in several profiles. The redox conditions in the sediments varied from normal in
the southern part of the sea to highly oxidized along the Novaya Zemlya Trough. Vertical sections through the sediments of
the latter exemplify the complete suppression of the biochemical activity of microorganisms. Our data provide insight into
the biogeochemistry of the Kara Sea and make it possible to specify the background values needed for ecological control during
the future exploration operations and extraction of hydrocarbons in the Kara Sea.
Original Russian Text ? E.M. Galimov, L.A. Kodina, O.V. Stepanets, G.S. Korobeinik, 2006, published in Geokhimiya, 2006, No.
11, pp. 1139–1191. 相似文献
32.
The effects of intrusive thermal stress have been studied on a number of Pleistocene sediment samples obtained from Leg 64 of the DSDP-IPOD program in the Gulf of California. Samples were selected from Sites 477, 478 and 481 where the organic matter was subjected to thermal stress from sill intrusions. For comparison purposes, samples from Sites 474 and 479 were selected as representative of unaltered material.The GC and GC-MS data show that lipids of the thermally unaltered samples were derived from microbial and terrestrial higher-plant detritus. Samples from sill proximities were found to contain thermally-derived distillates and those adjacent to sills contained essentially no lipids. Curie point pyrolysis combined with GC and GC-MS was used to show that kerogens from the unaltered samples reflected their predominantly autochthonous microbial origin. Pyrograms of the altered kerogens were much less complex than the unaltered samples, reflecting the thermal effects. The kerogens adjacent to the sills produce little or no pyrolysis products since these intrusions into unconsolidated, wet sediments resulted in in situ pyrolysis of the organic matter.Examination of the kerogens by ESR showed that spin density and line width pass through a maximum during the course of alteration but ESR g-values show no correlation with maturity. Stable carbon isotope (δ13C) values of kerogens decrease by 1–1.5‰ near the sills at Sites 477 and 481 and the atomic N/C decreases slightly with proximity to a smaller sill at Site 478. Differences in maturation behavior between Site 477 and 481 and Site 478 are attributed to dissimilarities in thermal stress and to chemical and isotopic heterogeneity of Guaymas Basin protokerogen. 相似文献