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1.
We studied recent sedimentation in small saline and brackish lakes located in the Ol’khon region (western Baikal area) with arid and semiarid climate. The lakes belong to the Tazheran system; it is a series of compactly located closed shallow lakes, with a limited catchment area and different mineralization, under the same landscape, climatic, geologic, and geochemical conditions. Two complementary approaches are applied in the research: (1) a detailed study of individual lake and (2) a comparison of the entire series of lakes, which can be considered a natural model for studying the relationship between endogenic mineral formation and the geochemistry of lake waters. The lake waters and bottom sediments were studied by a set of modern methods of geochemistry, mineralogy, and crystal chemistry. The mineral component of the bottom sediments was analyzed by powder X-ray diffraction (XRD), IR spectroscopy, and electron microscopy. The lakes are characterized by predominant carbonate sedimentation; authigenic pyrite, smectite, chlorite, and illite are detected in assemblage with carbonate minerals in the bottom sediments. Carbonate phases have been identified, and their proportions have been determined in the samples by decomposition of the complex XRD profiles of carbonate minerals into peaks using the Pearson VII function. Mathematical modeling of the XRD profiles of carbonates has revealed that predominantly Mg-calcites with variable Mg content and excess-Ca dolomite accumulate in lake bottom sediments influenced by biogenic processes. Aragonite, monohydrocalcite, and rhodochrosite form in some lakes along with carbonates of the calcite-dolomite series. We show a dependence of the composition of the assemblages of the newly formed endogenic carbonate minerals and their crystallochemical characteristics on the chemical composition of lake waters.  相似文献   

2.
Organogenic sediments (sapropels) in lakes are characterized by a reduced type of diagenesis, during which organic compounds are decomposed, the chemical composition of the pore waters is modified, and authigenic minerals (first of all, pyrite) are formed. Pyrolysis data indicate that organic matter undergoes radical transformatons already in the uppermost sapropel layers, and the composition of this organic matter is principally different from the composition of the organic matter of the its producers. The sapropels contain kerogen, whose macromolecular structure starts to develop during the very early stages of diagenesis, in the horizon of unconsolidated sediment (0–5 cm). The main role in the diagenetic transformations of organic matter in sediments is played by various physiological groups of microorganisms, first of all, heterotrophic, which amonifying, and sulfate-reducing bacteria. SO42? and Fe2+ concentrations in the pore waters of the sediments are determined to decrease (because of bacterial sulfate reduction), while concentrations of reduced Fe and S species (pyrite) in the solid phase of the sediment, conversely, increase. Comparative analysis shows that, unlike sapropels in lakes in the Baikal area, sapropels in southern West Siberia are affected by more active sulfate reduction, which can depend on both the composition of the organic matter and the SO42? concentration in the pore waters.  相似文献   

3.
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4.
We present an organic geochemical study of surface sediments of Lake Sarbsko, a shallow coastal lake on the middle Polish Baltic coast. The aim was to provide evidence concerning the origin of the organic matter (OM) and its compositional diversity in surface deposits of this very productive, highly dynamic water body. The content and composition of the OM in the bottom sediments were investigated at 11 sampling stations throughout the lake basin. OM sources were assigned on the basis of bulk indicators [total organic carbon (TOC), total nitrogen (TN), δ13CTOC and δ15N and extractable OM yield], biomarker composition of extractable OM and compound-specific C isotope signatures. The source characterization of autochthonous compounds was verified via phytoplankton analysis. The distribution of gaseous hydrocarbons in the sediments, as well as temporal changes in lake water pH, the concentration of DIC (dissolved inorganic carbon) and δ13CDIC were used to trace OM decomposition.The sedimentary OM is composed mainly of well preserved phytoplankton compounds and shows minor spatial variability in composition. However, the presence of CH4 and CO2 in the bottom deposits provides evidence for microbial degradation of sedimentary OM. The transformation of organic compounds in surface, bottom and pore waters via oxidative processes influences carbonate equilibrium in the lake and seasonally favours precipitation or dissolution of CaCO3.The data enhance our understanding of the relationships between the composition of sedimentary OM and environmental conditions within coastal ecosystems and shed light on the reliability of OM proxies for environmental reconstruction of coastal lakes.  相似文献   

5.
Geochemical studies of the ecosystems of 184 Siberian lakes in three largest zones of northern Asia (humid, arid, and semiarid) and in mountainous area were carried out. The contents of natural radionuclides, radiocesium, and rare-earth elements in conjugate components of the systems and the types of the main sources of the bottom sediment material have been determined.Dating of the bottom sediments was made by the activity of radioisotopes 137Cs and 210Pb, which permitted estimation of the sedimentation rates in lakes in different regions of Siberia: 0.35 cm/year in the south and 0.25–0.3 cm/year in the north.Six main ions have been determined in the waters of the studied lakes: Ca2+, Mg2+, Na+, HCO3?, SO42?, and Cl?. The distribution of natural radionuclides in the stratified sections of bottom sediments of Siberian lakes evidences the stable sedimentation and characterizes their contents in the soils of water-catchment areas, which can be considered background contents there. Sediments enriched in organic matter have higher concentrations of U and lower ones of Th and K. The Th/K ratio in the studied bottom sediments is the same as in the soils. The Th/U ratios are somewhat lower than those in the soils because U is accumulated by chemogenic and organic components. The overall 137Cs pollution of bottom sediments of Siberian lakes is close to the global background (40 mCi /km2 in 2000), but in the Altai Territory and Buryatia and Altai Republics it is twice higher. The uneven areal and temporal distribution of residual radiocesium is observed not only in the lacustrine sediments but also in the lake water areas. The REE patterns of bottom sediments of different mineral types are similar to those of continental crust and clays of the Russian Platform, though organogenic and carbonate sediments have higher absolute REE contents than terrigenous ones. Pelitic fraction is the main REE concentrator in the bottom sediments.  相似文献   

6.
Organic matter contained in particulate matter in Lake Michigan waters and sediments has been characterized by CN ratios and by distributions of biomarker fatty acids, alkanols, sterols, and aliphatic hydrocarbons. Differences in organic constituents of particulate matter from various depths and distances from shore indicate a complex interaction of production, transformation, and destruction of the organic matter contained in sinking particles. Near-surface material contains important contributions of landderived organic matter, presumably of eolian input. Midwater particles have predominantly aquatic organic material of algal origin. At the sediment-water interface, selective suspension of the finer fractions of surficial sediments enriches bottom nepheloid layers with these sediment size classes. As a result, near-bottom particulate matter has an aquatic biomarker character. Organic matter associated with sinking particles undergoes substantial degradation during passage to the bottom of Lake Michigan, and aquatic components are selectively destroyed relative to terrigenous components.  相似文献   

7.
Characteristics of the organic material in Green River Formation shale suggest that this material was derived from algae that grew in ancient Eocene lakes. The basin depressions for these nonmarine lakes were formed by the uplifting of the Rocky Mountain ranges. Large quantities of soluble salts flowed into these basins from the mountain streams, increasing the salinity of the lake waters until they became chemically stratified. In the upper, relatively fresh-water section of the lakes, abundant quantities of microscopic algae and other biota grew. Lesser amounts of terrestrial plant life remains were supplied in the form of wind- or water-borne spores and in the form of water-soluble organic materials entering the in-flowing waters. The lower section of the lake waters became highly reducing and stagnant because of lack of seasonal oxidative turnovers, thus providing ideal conditions for the accumulation and preservation of the organic debris from the lake biota.Precipitation of mineral carbonates and silicates from the highly saline waters provided most of the minerals that were co-deposited with the organic matter. Carbon dioxide, which evolved from the aquatic plant life, probably influenced mineral carbonate precipitation. During the life span of a few million of years the characteristics of the lake waters varied considerably and had significant effect upon the composition of both the inorganic and organic constituents of the Green River shale.Sixty to seventy-five core samples from each of three basins of the Green River Formation were analyzed for changes in both the organic and inorganic constituents. Considerable differences in the organic components of the soluble bitumen and of the insoluble kerogen were evident. Some of these differences appeared to be related to depth of burial and some to source material and the environment of the lake waters. Compositional differences relative to lithologic differences in the sediments of the three basins were found.  相似文献   

8.
 The concentrations of N, P and Fe in surface sediments and interstitial and overlying (bottom and surface) waters of the Ashtamudi estuary located in the southwest coast of India are reported along with the various chemical species of N (NO2–N, NO3–N, NH3–N and total N) and P (organic P, inorganic P and total P) in interstitial and overlying waters and discussed in terms of the physico-chemical environment of the system. The interstitial water exhibits higher salinity values compared to bottom and surface waters, indicating the coupled effects of salt-wedge phenomena and gravitational convection of more saline-denser marine water downward through surface sediments. N, P and Fe as well as their chemical forms are enriched in the interstitial water compared to bottom and surface waters. However, the dissolved oxygen (DO) shows an opposite trend. The marked enrichment of NH3–N in the interstitial water and its marginal presence in bottom and surface waters, together with the substantial decrease in the DO concentrations of bottom water and consequent increase in the concentrations of NO2–N and NO3–N in interstitial and bottom waters, points to the nitrification process operating in the sediment-water interface of the Ashtamudi estuary. The enrichment of total N, P and Fe in the interstitial water compared to the overlying counterparts and the positive correlation of sediment N, P and Fe with mud contents as well as organic carbon indicate that these elements are liberated during the early diagenetic decomposition of organic matter trapped in estuarine muds. Received: 5 Oktober 1998 · Accepted: 9 February 1999  相似文献   

9.
The paper presents the results of study of ferromanganese carbonate rocks in the Sob area (Polar Urals), which is located between the Rai-Iz massif and the Seida–Labytnangi Railway branch. These rocks represent low-metamorphosed sedimentary rocks confined to the Devonian carbonaceous siliceous and clayey–siliceous shales. In terms of ratio of the major minerals, ferromanganese rocks can be divided into three varieties composed of the following minerals: (1) siderite, rhodochrosite, chamosite, quartz, ± kutnahorite, ± calcite, ± magnetite, ± pyrite, ± clinochlore, ± stilpnomelane; (2) spessartite, rhodochrosite, and quartz, ± hematite, ± chamosite; (3) rhodochrosite, spessartite, pyroxmanite, quartz ± tephroite, ± fridelite, ± clinochlore, ± pyrophanite, ± pyrite. In all varieties, the major concentrators of Mn and Fe are carbonates (rhodochrosite, siderite, kutnahorite, Mn-calcite) and chlorite group minerals (clinochlore, chamosite). The chemical composition of rocks is dominated by Si, Fe, Mn, carbon dioxide, and water (L.O.I.): total SiO2 + Fe2O 3 tot + MnO + L.O.I. = 85.6?98.4 wt %. The content of Fe and Mn varies from 9.3 to 55.6 wt % (Fe2O 3 tot + MnO). The Mn/Fe ratio varies from 0.2 to 55.3. In terms of the aluminum module AlM = Al/(Al + Mn + Fe), the major portion of studied samples corresponds to metalliferous sediments. The δ13Ccarb range (–30.4 to–11.9‰ PDB) corresponds to authigenic carbonates formed with carbon dioxide released during the microbial oxidation of organic matter in sediments at the dia- and/or catagenetic stage. Ferromanganese sediments were likely deposited in relatively closed seafloor zones (basin-traps) characterized by periodic stagnation. Fe and Mn could be delivered from various sources: input by diverse hydrothermal solutions, silt waters in the course of diagenesis, river discharges, and others. The diagenetic delivery of metals seems to be most plausible. Mn was concentrated during the stagnation of bottom water in basin-traps. Interruption of stagnation promoted the precipitation of Mn. The presence of organic matter fostered a reductive pattern of postsedimentary transformations of metalliferous sediments. Fe and Mn were accumulated initially in the oxide form. During the diagenesis, manganese and iron oxides reacted with organic matter to make up carbonates. Relative to manganese carbonates, iron carbonates were formed under more reductive settings and higher concentrations of carbon dioxide in the interstitial solution. Crystallization of manganese and iron silicates began already at early stages of lithogenesis and ended during the regional metamorphism of metalliferous sediments.  相似文献   

10.
The Parnok deposit is made up of stratiform lodes of iron (magnetite) and manganese (oxide-carbonate, carbonate, and carbonate-silicate) ores localized among terrigenous-carbonate sediments (black shales) on the western slope of the Polar Urals. The lithological study showed that ore-bearing sediments were accumulated in a calm hydrodynamic setting within a relatively closed seafloor area (trap depressions). Periodic development of anaerobic conditions in the near-bottom seawater was favorable for the accumulation of dispersed organic matter in the terrigenous-carbonate sediments. Carbon required to form calcium carbonates in the ore-bearing sediments was derived from carbon dioxide dissolved in seawater. In the organic-rich sediments, carbonates were formed with the participation of carbon dioxide released by the destruction of organic matter. However, δ13C values (from 0.5 to ?4.4‰ PDB) suggest a relatively low fraction of the isotopically light biogenic carbon in the host calcite. The most probable sources of Fe and Mn were hydrothermal seepages at the seafloor. The Eh-pH conditions during stagnation were favorable for the precipitation of Fe and accumulation of Mn in a dissolved state. Transition from the stagnation regime to the concentration of oxygen in near-bottom waters was accompanied by oxidation of the dissolved Mn and its precipitation. Thus, fluctuations in Eh-pH parameters of water led to the differentiation of Fe and Mn. Initially, these elements were likely precipitated as oxides and hydroxides. During the subsequent lithification, Fe and Mn were reduced to form magnetite and rhodochrosite. The texture and structure of rhodochrosite aggregates indicate that manganese carbonates already began to form at the diagenetic stage and were recrystallized during the subsequent lithogenetic stages. Isotope data (δ13C from ?8.9 to ?17.1‰ PDB) definitely indicate that the oxidized organic matter of sediment served as the main source of carbon dioxide required to form manganese carbonates. Carbonates from host rocks and manganese ores have principally different carbon isotopic compositions. Unlike carbonates of host rocks, manganese carbonates were formed with an active participation of biogeochemical processes. Further processes of metagenesis (T ≈ 250–300°C, P ≈ 2 kbar) resulted in the transformation of textures, structures, and mineral composition of all rocks of the deposit. In particular, increase in temperature and pressure provided the formation of numerous silicates in manganese ores.  相似文献   

11.
We present integrated mineralogical, geochemical, and palynological data for Late Pleistocene-Holocene bottom sediments of Lake Arakhlei located in the Beklemishev tectonic basin in the southern Vitim Plateau (central Transbaikalia). The sediment samples were studied by X-ray diffractometry (XRD), Fourier-transform infrared (FTIR) spectroscopy, laser particle sizing, spore-pollen analysis, radiocarbon (14C AMS) dating, and XRF spectrometry. The cored 128 cm long section of lake sediments consists of two units: One is composed mainly of layered silicates (illite-smectite, illite, chlorite, chlorite-smectite, muscovite, and kaolinite) and organic matter (OM) but no carbonates from 0 to 80 cm and the other contains authigenic Ca-Mg carbonates (up to 30%) of Mg-calcite and excess-Ca dolomite from 80 to 128 cm. The sediments also contain a rare mineral weddellite CaC2O42H2O discovered for the first time in Transbaikalian lakes. The evolution of Lake Arakhlei and its drainage basin comprised four stages, with pollen zones that mark the Late Pleistocene and Holocene climate history of the Beklemishev basin. The reconstructed history of Lake Arakhlei for the past ~ 15,500 years followed general climatic changes in the Northern Hemisphere. Thus, integrated research, including detailed analysis of mineral components and spore-pollen assemblages in lake sediments, is a workable tool for studying climatic controls of continental sedimentation.  相似文献   

12.
文章以修水地区下寒武统王音铺组至观音堂组下部富铀黑色页岩地层钻孔样品（U含量为9.37×10-6~202×10-6） 为研 究对象,进行了细致的显微观察和分析,并对该区下寒武统地层中U含量与沉积环境因素（沉积盆地中的生物生产力、底 层水体的氧化还原状态、及盆地与广海间的流通性） 之间的关系进行了探讨。结果表明,这些钻孔样品显示明显的沉积成 岩特征,未发现明显热液叠加/淋积作用现象,说明本区下寒武统地层只经历了沉积成岩作用,而没有经历过明显的热液作 用或者淋积作用。研究地层大部分样品中的U含量与TOC含量呈正相关,王音铺组上部U含量最高（202×10-6） 的样品沉积 时的初级生物生产力也最高。经扫描电镜观察和电子探针分析,发现其中有机质中包裹着沥青铀矿,两者关系密切,推测 U与有机质很可能是一起沉积-成岩富集的;在缺氧硫化的强还原沉积环境下沉积的王音铺组地层的U含量,明显高于在 缺氧非硫化环境下沉积的观音堂组下部地层中的U含量,而且在强还原硫化环境下,沉积时盆地处于开放流通性程度较高 时期的样品,其U含量明显高于盆地处于开放程度较低时期的样品。综合这些观察和分析得出,早寒武世王音铺组上部地 层沉积时,高生物生产力所形成的有机质降解时大量耗氧,导致底层水沉积环境处于强还原硫化状态,同时,沉积盆地处 于适当的开放程度,与广海之间水流交换使盆地上层含U氧化水体得到补充,U最终在底层水体强还原硫化环境下沉淀于 沉积物中,可达到较高程度的富集乃至矿化的水平。  相似文献   

13.
A multicomponent diagenetic model was developed and applied to reconstruct the conditions under which the most recent sapropel, S1, was deposited in the eastern Mediterranean Sea. Simulations demonstrate that bottom waters must have been anoxic and sulphidic during the formation of S1 and that organic matter deposition was approximately three times higher than at present. Nevertheless, most present day sediment and pore water profiles — with the exception of pyrite, iron oxyhydroxides, iron-bound phosphorus and phosphate — can be reproduced under a wide range of redox conditions during formation of S1 by varying the depositional flux of organic carbon. As a result, paleoredox indicators (e.g., Corg:S ratio, Corg:Porg ratio, trace metals) are needed when assessing the contribution of oxygen-depletion and enhanced primary production to the formation of organic-rich layers in the geological record. Furthermore, simulations show that the organic carbon concentration in sediments is a direct proxy for export production under anoxic bottom waters.The model is also used to examine the post-depositional alteration of the organic-rich layer focussing on nitrogen, phosphorus, and organic carbon dynamics. After sapropel formation, remineralisation is dominated by aerobic respiration at a rate that is inversely proportional to the time since bottom waters became oxic once again. A sensitivity analysis was undertaken to identify the most pertinent parameters in regulating the oxidation of sapropels, demonstrating that variations in sedimentation rate, depositional flux of organic carbon during sapropel formation, bottom water oxygen concentration, and porosity have the largest impact. Simulations reveal that sedimentary nutrient cycling was markedly different during the formation of S1, as well as after reoxygenation of bottom waters. Accumulation of organic nitrogen in sediments doubled during sapropel deposition, representing a significant nitrogen sink. Following reventilation of deep waters, N2 production by denitrification was almost 12 times greater than present day values. Phosphorus cycling also exhibits a strong redox sensitivity. The benthic efflux of phosphate was up to 3.5 times higher during the formation of S1 than at present due to elevated depositional fluxes of organic matter coupled with enhanced remineralisation of organic phosphorus. Reoxygenation of bottom waters leads to a large phosphate pulse to the water column that declines rapidly with time due to rapid oxidation of organic material. The oxidation of pyrite at the redox front forms iron oxyhydroxides that bind phosphorus and, thus, attenuate the benthic phosphate efflux. These results underscore the contrasting effects of oxygen-depletion on sedimentary nitrogen and phosphorus cycling. The simulations also confirm that the current conceptual paradigm of sapropel formation and oxidation is valid and quantitatively coherent.  相似文献   

14.
古海洋生产力指标研究进展   总被引：20，自引：1，他引：19  
寻求反映古海洋生产力变化的指标是古海洋学研究的重要内容。生物沉积物、营养元素、微量元素和同位素、古生物资料等与古海洋生产力具有一定的关系,常用于古海洋生产力的重建工作:(1)生物沉积物主要包括有机碳、生物碳酸盐和生物硅质沉积等,其埋藏速率在很大程度上受到古海洋生产力的控制,常常用作古海洋生产力的替代性指标;(2)在地质时间尺度上,古海洋生产力主要受到大洋中营养元素可利用程度的控制,因此营养元素的相关记录可以提供古海洋生产力状况的重要信息;(3)海洋中某些微量元素的地球化学行为或者与有机质的改造有关,或者受到氧化还原条件变化的控制,或者受到某种浮游生物的生长的影响,从而能够直接或者间接地指示古海洋生产力的变化;(4)海相碳酸盐和有机质的碳同位素记录,海相有机物的氮同位素比值也用以再造古生产率等古海洋学参数;(5)可以利用对微体化石丰度值及其组合反映古生产力的变化。  相似文献   

15.
Crystallization of authigenic carbonates in mud volcanoes at Lake Baikal   总被引：1，自引：0，他引：1  
This paper presents data on authigenic siderite first found in surface sediments from mud volcanoes in the Central (K-2) and Southern (Malen’kii) basins of Lake Baikal. Ca is the predominant cation, which substitutes Fe in the crystalline lattice of siderite. The enrichment of the carbonates in the 13C isotope (from +3.3 to +6.8‰ for the Malen’kii volcano and from +17.7 to +21.9‰ for K-2) results from the crystallization of the carbonates during methane generation via the bacterial destruction of organic matter (acetate). The overall depletion of the carbonates in 18O is mainly inherited from the isotopic composition of Baikal water.  相似文献   

16.
The carbon isotopic composition of organic matter from lake sediments has been extensively used to infer variations in productivity. In this paper, based on the study of the contents and δ13C values of organic matter in different types of lakes, it has been found that δ13C values of organic matter have different responses to lake productivity in different lakes. As to the lakes dominated by aqutic macrophytes such as Lake Caohai, organic matter becomes enriched in 13C with increasing productivity. As to the lakes dominated by aquatic algae such as Lake Chenghai, δ13C values of organic matter decrease with increasing productivity, and the degradation of aquatic algae is the main factor leading to the decrease of δ13C values of organic matter with increasing productivity. Therefore, we should be cautious to use the carbon isotopic composition of organic matter to deduce lake productivity.  相似文献   

17.
Using some uranium deposits and recent U-bearing sediments as examples, it is shown that all U-bearing rocks are characterized by an association of organic matter and calcium phosphate, irrespective of the quantitative relationship between these components. A considerable proportion of these components was delivered into sediments with remains of marine planktonic and nektonic organisms. Along with organic matter, calcium phosphate played a significant role in uranium concentration. This is related to a high sorption ability of the calcium phosphate. Uranium accumulated during diagenesis as a result of diffusion exchange between bottom and interstitial waters. The combination of anoxic bottom environment with high bioproductivity in upper aerated waters, a typical phenomenon in oceanic upwelling zones, is the most favorable factor of uranium concentration in the sedimentary process. This determines the stable paragenetic association of organic matter, phosphorus, and uranium in marine sediments, such as black shales and organogenic phosphate deposits.  相似文献   

18.
中国中新生代咸化湖盆烃源岩沉积的问题及相关进展   总被引：8，自引：0，他引：8  
我国东部断陷湖盆和西部坳陷湖盆第三系均有蒸发岩与烃源岩共生现象。前者水体深、咸化范围小，在氯化盐和碳酸盐沉积环境中形成了优质烃源岩，后者水体浅、咸化范围大，在氯化盐和硫酸盐沉积环境中发育了优质烃源岩，作者认为两种湖盆出现的水体分层是有机质堆积和保存的重要条件。济阳坳陷和柴达木盆地为两类咸化湖盆的典型代表，对它们的研究可以深化蒸发岩-烃源岩共生区油气地质的认识、促进勘探发展。  相似文献   

19.
Major and trace elements, organic matter, carbonates, loss of ignition, grain size, gravel, sand, silt, clay, and qualitative mineralogical composition were determined on surficial marine sediments sampled during the stormy (February), dry (May), and rainy (September) seasons in the coastal area adjacent to Panuco River discharges into the Gulf of Mexico. The sediments supplied by the river move in a north-east direction, and are deposited in the north-east extreme of the studied area. Terrigenous sediments show a strong association of Al2O3 with Fe2O3, Na2O, K2O, P2O5, Rb, Cu, Zn, organic matter, clay, and grain size (Mz). Mineralogical analysis shows that they are formed by quartz, kaolinite, montmorillonite, illite-montmorillonite and biotite. The highest metal concentration of Cu (25 mg/kg), Zn (155 mg/kg), Pb (50 mg/kg) and organic matter (1.26%) was observed in the sampling points located very close to the river mouth. A statistical analysis was done with the information contained in the variables. Five significant factors explain 77% of the total variance: factor 1 is due to sediments from a terrigenous source, factor 2 corresponds to sediments from a biogenous source, factor 3 is associated to sediments with heavy minerals, factor 4 is due to Co concentration, and factor 5 is due to Ni concentration. The sediments supplied from the river had a short-term local impact on the sediment distribution, as observed by the carbonate and heavy mineral concentration of the sediments.  相似文献   

20.
The paper reviews data (acquired in 2007–2016) on aliphatic and polycyclic aromatic hydrocarbons in comparison with data on concentrations of lipids, Corg, and chlorophyll a in the water and bottom sediments the river–sea geochemical barrier (for the Northern Dvina, Ob, Yenisei, and Lena rivers). It was established that the concentrations of anthropogenic hydrocarbons decrease and these compounds precipitate like other organic compounds and particulate matter, where riverine and marine waters mix. Relatively pure water flows in the pelagic zones of seas. In spite of low temperatures in the Arctic, anthropogenic hydrocarbons transform so rapidly that natural compounds dominate in the water and bottom sediments: autochthonous in the seawater and allochthonous in the bottom sediments.  相似文献   

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