Composition and genesis of the organic matter in the bottom sediments of the East Siberian Sea

The chemical composition of organic matter (C_org, N_org, δ¹³C, δ¹⁵N, and n-alkanes) was studied in the top layer of bottom sediments of the East Siberian Sea. Possible ways were proposed to estimate the amount of the terrigenous component in their organic matter (OM). The fraction of terrigenous OM estimated by the combined use of genetic indicators varied from 15% in the eastern part of the sea, near the Long Strait, to 95% in the estuaries of the Indigirka and Kolyma rivers, averaging 62% over the sea area.     

Sterols in interstitial waters of marine sediments

In order to attempt to elucidate the nature of biogeochemical processes occurring at the water-sediment interface, sterols have been analysed in near bottom sea and interstitial waters collected in the eastern and western intertropical Atlantic ocean. Free and esterified sterol concentrations range from 0.2 to 82 μg l^?1 and are much higher than those found in overlying sea water, which range from 0.2 to 1.7 μg l^?1 for the dissolved fraction and from 0.01 to 0.07 μg l^?1 for the particulate fraction. Cholest-5-en-3β-ol and 24-ethylcholest-5-en-3β-ol are the dominant sterols in sea and interstitial waters. The variability encountered for the relative importance of minor sterols such as 24-methylcholesta-5,24(28)-dien-3β-ol and stanols, 5α-cholest-22(E)-en-3β-ol, 5α-cholestan-3β-ol and 24-ethyl-5α-cholestan-3β-ol in interstitial water and their variation with depth is discussed in terms of diversity of inputs and bacterial activity. For sediments cored off the Mauritanian coast, a productive area characterized by an intense upwelling, the chemical signatures observed in interstitial water through stanol/stenol ratios occur at levels of very high heterotrophic aerobic bacterial biomass estimations. The study of the sterol composition of interstitial water could constitute a valuable tool in appreciating the intensity of chemical and biological processes occurring in the first few metres of recent marine sediments.     

Composition of organic compounds in bottom sediments of lakes in the taiga and steppe zones in Siberia

The paper presents chromatographic–mass spectrometric data on the individual composition of organic compounds in sapropel-like deposits of lakes in the steppe, forest–steppe, and three taiga natural climatic zones (NCZ) in Khakassia and western Siberia. Data on the individual composition of n-alkanes, carboxylic acids and their esters, thiophenes, phytol, phytone, steroids, and di- and triterpenoids and on their distribution in the sediments show systematic variations in the composition of the organic matter (OM) with increasing ambient temperature and the aridity of the climate. The concentrations of all groups of the compounds in lacustrine sediments decrease southward, and simultaneously esters with long (up to С₂₀) alkyl substituents appear. The concentrations of oxygen-bearing compounds increase among the acyclic structures and triterpenoids, as also do the concentrations of structures ketonic substituents among the steroids. The dominance of the carboxylic acids and their esters by high molecular weight homologues gives way to the dominance of palmic acid and its derivatives. Among n-alkanes, the dominance of С₂₇ and С₂₉ hydrocarbons typical of terrestrial plants gives way to a higher percentage of homologues С₂₁–С₂₅ (macrophytes) and С₃₁ (herbaceous plants). Among the tocopheroles, the concentration of the oxidized form of α-tocopherol (acetate) increases.     

Composition of waters and sediments in the Antwerp harbor

Industrial expansion in the harbor areas of Antwerp has altered environmental conditions to a great extent. This study examines the relation between the water economy of the port of Antwerp docks and the composition of dock waters, sediments, and interstitial waters, with emphasis on trace metals and chlorides. Some conclusions are reached as to the possible use of the dredged deposits in agriculture.     

Geochemical signature of bottom sediments in the mixing zones of Ob and Yenisei waters with Kara Sea water

This paper reports the results of a study of the geochemistry of bottom sediments from the zones of mixing between the freshwater of the Ob and Yenisei rivers and the saline water of the Kara Sea by means of neutron activation analysis. Using separate datasets for the sediments of the Ob and Yenisei estuaries accumulated under identical facies conditions, some characteristic features of the distribution of a number of chemical elements (mostly lithophile group elements) were established. The differences between them were attributed to distinctive regional geological and geochemical features of the catchments of the Ob and Yenisei, which are inherited by the geochemical characteristics of terrigenous material transported to the sea. The choice of the most informative indicator elements and their grouping on the basis of the character of behavior demonstrated that bottom sediments of the Ob or Yenisei origin can be identified in the marine region studied using the geochemical characteristics of a small group of samples.     

Noble metals in the bottom sediments of the Chukchi Sea

Abundance of noble metals (NM) and bulk chemical composition have been studied in bottom sediments of the Chukchi Sea. Distribution of NM and their correlation with major and trace elements in the sediments have been analyzed using multicomponent statistics. It was established that the average contents of NM in the bottom sediments of the Chukchi Sea significantly exceed those both in shelf terrigenous sediments and stratisphere. Osmium and iridium enrich mixed and pelitic sediments relative to shallow-water areas and their influx is presumably determined by erosion of coastal and bottom loose deposits. High Ag, Ru, Au, and Pt contents were identified in the clayey sediments enriched in biogenic elements in the individual areas of the Southern Chukchi plain (Chukchi sea) confined to the intersection zones of submeridional and sublatitudinal structures of the graben-rift system, which was formed in the Mesozoic and activated in the late Cenozoic time.     

Silica distribution in interstitial waters and sediments from the southeastern pacific

Analyses for silica in the interstitial water of five cores from the southeast Pacific are presented. Silica is enriched in these interstitial waters resulting in a vertical flux of silica of between 10 and 50 μmol cm^?2 yr^?1 from the sediment into the overlaying seawater. This flux is generated by the dissolution of biogenic silica, the dissolution of which is increased in areas of bottom water turbulence. The Si, Al and calculated opal (Leinen, 1977) contents of the bulk sediment of these cores are also presented. Small scale variations over depth intervals of tens of centimetres are present as a result of chaning conditions of sedimentation.     

Dissolved aluminium in interstitial waters of recent marine sediments

Measurements of the concentration and vertical distribution of dissolved aluminium and silica, and of pH. in interstitial waters of recent marine sediments from the North Sea and the Mediterranean Sea were performed to evaluate the behaviour of aluminium during early diagenesis. The results suggest that thermodynamic equilibria alone do not control the concentrations of dissolved species in the system Al-Si-O₂-H₂O during early diagenesis. Rather, these concentrations are governed by dynamic factors involving mineral dissolution-precipitation reactions and diffusion.     

An interpretation of carbon and sulfur relationships in Black Sea sediments as indicators of environments of deposition

Syngenetic iron sulfides in sediments are formed from dissolved sulfide resulting from sulfate reduction and catabolism of organic matter by anaerobic bacteria. It has been shown that in recent marine sediments deposited below oxygenated waters there is a constant relationship between reduced sulfur and organic carbon which is generally independent of the environment of deposition. Reexamination of data from recent sediments from euxinic marine environments (e.g., the Black Sea) also shows a linear relationship between carbon and sulfur, but the slope is variable and the line intercepts the S axis at a value between 1 and 2 percent S. It is proposed that the positive S intercept is due to watercolumn microbial reduction of sulfate using metabolizable small organic molecules and the sulfide formed is precipitated and accumulates at the sediment-water interface. The variation in slope and intercept of the C to S plots for several cores and for different stratigraphic zones for the Black Sea can be interpreted in relation to thickness of the aqueous sulfide layer or thinness of the oxygen containing layer and to deposition rate, but also may be influenced by availability of iron, and perhaps the type of organic matter (Leventhal, 1979).     

Sulfur speciation in the upper Black Sea sediments

We report solid phase sulfur speciation of six cores from sediments underlying oxic, suboxic and anoxic-sulfidic waters of the Black Sea. Our dataset includes the five sulfur species [pyrite-sulfur, acid volatile sulfides (AVS), zerovalent sulfur (S(0)), organic polysulfides (RS_x), humic sulfur] together with reactive iron and manganese, as quantified by dithionite extraction, and total organic carbon. Pyrite – sulfur was the major phase in all cores [200-400 µmol (g dry wt)^- 1] except for the suboxic core. However, zerovalent sulfur and humic sulfur also reached very significant levels: up to about 109 and 80 µmol (g dry wt)^- 1, respectively. Humic sulfur enrichment was observed in the surface fluff layers of the eastern central basin sediments where Unit-1 type depositional conditions prevail. Elemental sulfur accumulated as a result of porewater sulfide oxidation by reactive iron oxides in turbidities from the anoxic basin margin and western central basin sediments. The accumulation of elemental sulfur to a level close to that of pyrite-S in any part of central Black Sea sediments has never been reported before and our finding indicates deep basin turbidites prevent the build-up of dissolved sulfide in the sediment. This process also contributes to diagenetic pyrite formation whereas in the non-turbiditic parts of the deep basin water column formed (syngenetic) pyrite dominates the sulfur inventory. In slope sediments under suboxic waters, organic sulfur (humic sulfur + organic polysulfides) account for 33-42% of total solid phase S, indicating that the suboxic conditions favor organosulfur formation. Our study shows that the interactions between depositional patterns (Unit 1 vs. turbidite), redox state of overlying waters (oxic-suboxic-sulfidic) and organic matter content determine sulfur speciation and enable the accumulation of elemental sulfur and organic sulfur species close to a level of pyrite-S.     

Origin of sulfur species in acid sulfate-chloride thermal waters,northeastern Japan

Acid sulfate-chloride thermal water samples collected together with fumarolic gases from various volcanic areas in northeastern Japan were studied chemically and isotogdically. δ³⁴S (COT) values of sulfate and hydrogen sulfide from these volcanic hot springs range from +4.0 to +31 and from ?15.0 to ?2.0% respectively, with δ³⁴S_ys value of +2.5 to +31. The δ³⁴S of the sulfate in the more saline waters tends to become smaller with increasing ratio of SO₄ to Cl, although the chemical and isotopic composition of acid thermal water within some areas may be altered by secondary processes during the discharge of the thermal waters. This trend can be explained by the reaction of the volcanic gases, having S/Cl of 4 ~ 7 and total sulfur of ~0% in δ³⁴S, with ground water at 200°C, and/or the removal of sulfide phase depleted in ³⁴S from the acid thermal water formed by the disproportionation of volcanic sulfur. The sulfur species in acid sulfate-chloride thermal water are shown to be volcanic exhalations.     

Biogeochemical processes of carbon and sulfur cycles in sediments of the outer shelf of the Black Sea (Russian Sector)

Within the mass of recent (unit-I) and ancient Black Sea (unit-II) sediments on the outer shelf of the Russian sector of the Black Sea, the rates of anoxic processes participating in diagenetic transformations of carbon and sulfur compounds were first measured using ³⁵S and ¹⁴C radioactive tracers. The main energy source for biogeochemical processes in (unit-I) sediments is the organic matter (OM) supplied to the bottom from the water mass. In (unit-II) sediments, this is methane in a migratory form proved by the excess of its oxidation rate over that of its generation. In recent silt, the primary microbial process is sulfate reduction; in unit-II, this is methane anoxic oxidation by the consortium of archeides and sulfate reductants. The organic matter produced in methane oxidation, in turn, acts as an energy source for the community of anaerobic heterotrophic microorganisms in the bottom sediments, which are remote from the water-sediment interface.     

Biochemical compounds in offshore California sediments and sea waters

Amino acids and sugars in marine basin sediments, in particulate matter of overlying waters, and in solution in these waters were investigated.Comparison of the percentage distribution of amino acids in sediments with those dissolved or in suspended particulate matter in overlying waters reveals several interesting differences. Arginine decreases rapidly with depth in the particulate matter and is not present in the dissolved state, whereas it is highly abundant in the sediments. In contrast, ornithine, serine and glycine are relatively more abundant in the water. The high concentration of β-alanine in sediments and its absence in the sea may result from a possible decarboxylation of aspartic acid. With depth of burial, glutamic and aspartic acids increase. Experimental data suggest that part of the amino acids in sediments are produced biologically by microbes and burrowing animals in the early stages of diagenesis and that they are not merely survivors of diagenesis.Comparable biogeochemical differences between organic matter in the sea and that in sediments are observed in the case of sugars. Here again, carbohydrates are both products and survivors of diagenesis. Certain phenols and indoles also are found in the sediments and the sea.A tentative interpretation is offered as to the probable source of the organic matter in the sediments.     

Manganese ore potential related to hydrosulfuric pollution of bottom waters (with the Black Sea as an example)

Conditions and scales of the accumulation of dissolved manganese in waters of marine basins with hydrosulfuric contamination are considered. It is shown that the Kalamit ferromanganese nodule field, most probably, originated due to the delivery of manganese from the hydrosulfuric zone of the Black Sea. Precisely this source converts the normal diagenetic process of material redistribution into the ore process. It is demonstrated that the formation of ferromanganese nodules in the Black Sea represents an embryonic manganese ore process. Its full-scale development seems to have taken place in the Early Oligocene Maikop basin owing to the spatiotemporal coincidence of a series of favorable conditions.     

Uronic and other organic acids in Baltic Sea and Black Sea sediments

Organic acids were released from marine sediments by acid hydrolysis. Ion-exchange chromatography and GC-MS were used to separate and identify the acids. The major compounds detected were galacturonic, glucuronic, mannuronic, 4-O-methylglucuronic, cellobiouronic, guluronic, glyceric, glycolic, lactic and erythronic acids. Numerous biouronic (sugar-uronic acid compounds) and aldonic acids were also found. The low abundance of uronic acids characteristic of terrigenous plants and the similarity of the biouronic composition to that of marine algae indicate a marine algal source for the acids in the sediment. Results from the Black Sea are compared with those from the Baltic Sea and several diagenetic transformations are discussed.     

Uranium diagenesis in sediments underlying bottom waters with high oxygen content

We measured U in sediments (both pore waters and solid phase) from three locations on the middle Atlantic Bight (MAB) from the eastern margin of the United States: a northern location on the continental shelf off Massachusetts (OC426, 75 m water depth), and two southern locations off North Carolina (EN433-1, 647 m water depth and EN433-2, 2648 m water depth). These sediments underlie high oxygen bottom waters (250-270 μM), but become reducing below the sediment-water interface due to the relatively high organic carbon oxidation rates in sediments (EN433-1: 212 μmol C/cm²/y; OC426: 120 ± 10 μmol C/cm²/y; EN433-2: 33 μmol C/cm²/y). Pore water oxygen goes to zero by 1.4-1.5 cm at EN433-1 and OC426 and slightly deeper oxygen penetration depths were measured at EN433-2 (∼4 cm).All of the pore water profiles show removal of U from pore waters. Calculated pore water fluxes are greatest at EN433-1 (0.66 ± 0.08 nmol/cm²/y) and less at EN433-2 and OC426 (0.24 ± 0.05 and 0.13 ± 0.05 nmol/cm²/y, respectively). Solid phase profiles show authigenic U enrichment in sediments from all three locations. The average authigenic U concentrations are greater at EN433-1 and OC426 (5.8 ± 0.7 nmol/g and 5.4 ± 0.2 nmol/g, respectively) relative to EN433-2 (4.1 ± 0.8 nmol/g). This progression is consistent with their relative ordering of ‘reduction intensity’, with greatest reducing conditions in sediments from EN433-1, less at OC426 and least at EN433-2. The authigenic U accumulation rate is largest at EN433-1 (0.47 ± 0.05 nmol/cm²/y), but the average among the three sites on the MAB is ∼0.2 nmol/cm²/y. Pore water profiles suggest diffusive fluxes across the sediment-water interface that are 1.4-1.7 times greater than authigenic accumulation rates at EN433-1 and EN433-2. These differences are consistent with oxidation and loss of U from the solid phase via irrigation and/or bioturbation, which may compromise the sequestration of U in continental margin sediments that underlie bottom waters with high oxygen concentrations.Previous literature compilations that include data exclusively from locations where [O₂]_bw < 150 μM suggest compelling correlations between authigenic U accumulation and organic carbon flux to sediments or organic carbon burial rate. Sediments that underlie waters with high [O₂]_bw have lower authigenic U accumulation rates than would be predicted from relationships developed from results that include locations where [O₂]_bw < 150 μM.     

Nature and reactions of dissolved organic matter in the interstitial waters of marine sediments

Two organic rich sediments, an oxic muddy sand and a silty mud containing sulphate reducing and methane producing metabolic zones, were sampled from Loch Duich, a fjord type estuary in the N.W. coast of Scotland. Dissolved organic carbon (DOC), as measured by dry combustion and UV absorption, remained constant (8.3–15.8 mg C/l) with depth in the oxic pore waters at a concentration at least twice that of the overlying seawater. DOC in the anoxic pore waters increased linearly with depth from 13.6 at the surface to 55.9–70.5 mg C/l at 80cm. Most of the DOC was present in the high molecular weight (HMW) fraction as separated by ultrafiltration; the low molecular weight (LMW) fraction remained constant (10.0 mg C/l) in both oxic and anoxic pore waters. Spectroscopic data showed the ‘humic’ fraction of the HMW dissolved organic matter was mainly fulvic acid, a small proportion (approx 1%) of humic acid, and a third fraction, possibly melanoidins, which increased relative to fulvic acid with depth. These data confirm the pathway of humification (NissenBaum et al, 1971; nissenbaum and Kaplan, 1972) where HMW organic matter accumulates in pore waters as condensation products of LMW organic substances.     

Chemical composition of pore waters of bottom sediments in different Baikal basins

Results of study of pore waters of bottom sediments from different Baikal basins are presented. The most typical ion distribution patterns reflecting the Baikal sediment diagenesis are given. We have established that in areas with regular sedimentation, in the absence of faults and inflows, the sediment pore waters of three lake basins inherit the chemical composition of the Baikal water, which is stable in time and space. Changes in pore water composition mark general natural anomalies, such as the presence of active faults, tectonic movements, and inflows along permeable zones. In areas with the subsurface occurrence of gas hydrates, thorough long-term research has revealed an anomalous composition of pore waters. It has been established that the anomalies are caused by a discharge of deep-level mud-volcanic fluids. The ejected mud-volcanic waters differ from each other in mineralization, ion composition, and sources, which determines the difference in hydrate formation and the composition of gas hydrates.     

Stenols and stanols in the oxic and anoxic waters of the Black Sea

Water samples collected from a slope station and two deep stations in the western basin of the Black Sea were analyzed for stenols and stanols by glass capillary gas chromatography. These results were used in conjuction with hydrographic, particulate organic carbon, and chlorophyll a data to better understand sterol sources and their transport and transformation mechanisms in anoxic basins.The total free sterol concentrations found in the surface waters were 450–500 ng/l dropping rapidly to values well below 100 ng/l at depths below the $\text{O}{}_2\text{H}{}_2\text{S}$ interface. In the upper 200 m of the water column a strong association of sterols with particulate matter is suggested. Structural elucidation by a gas chromatograph-mass spectrometer-computer system revealed the presence of at least sixteen different stenols and stanols in the surface waters of the Black Sea. Cholesterol, 24-methylenecholesterol and 24-methylcholesta-5,22-dien-3β-ol were the major sterols in the surface waters. Cholesterol and 24-ethylcholesterol both exhibited a subsurface maximum at the $\text{O}{}_2\text{H}{}_2\text{S}$ interface. In the anoxic deep waters (200–2000 m) only cholesterol and 24-ethylcholesterol were found. Two stenols were found that have not been reported in seawater: a C₂₆ stenol with a saturated C₇H₁₅ side chain (presumably 24-norcholesterol) and 24-ketocholesterol. At least six 5α-stanols could be identified in the surface samples, each of them comprising about 10–20% of the concentration of the corresponding Δ5-stenol. From these comparatively high surface values the stanol concentrations drop rapidly to values near zero at the $\text{O}{}_2\text{H}{}_2\text{S}$ interface. Except for very low concentrations of 5α-cholestanol (< 4ng/l) no other stanols could be detected in the anoxic zone.From this data it appears that no detectable stenol → stanol conversion is occurring at the $\text{O}{}_2\text{H}{}_2\text{S}$ interface or in the deep anoxic waters of the Black Sea.