Adsorption behaviour of dibutyl phthalate on marine sediments

Laboratory experiments were carried out to investigate the adsorption behaviour of dibutyl phthalate (DBP) on marine sediments collected from five different sites in Victoria Harbour, Hong Kong. DBP adsorption can be well described by the Langmuir isotherm. The maximum DBP adsorption capacity (Q(max)) of the marine sediments ranges from 53 to 79 mg g(-1), which has a positive correlation with their organic content. Around 90% of the organic can be removed from the sediments with treatment by H(2)O(2) oxidation, and the Q(max) then decreases to a range between 13 and 22 mg g(-1). The black carbon content of the sediments has a much greater DBP adsorption capacity than does the natural organic matter of the sediments. The amount of DBP adsorbed on the sediments increases as the salinity of the marine water increases.     

Sulfate reduction in natural water bodies. 1. The effect of environmental factors and the measured rates of the process

Sulfate reduction is an important oxidation process involving transformation of organic matter and its components and taking place in the aquatic environment and bottom sediments of water bodies (both fresh and marine) under anaerobic conditions. The intensification of sulfate reduction in water bodies is a sign of a stronger anthropogenic impact on the environment and natural water bodies. The development of sulfate reduction under natural conditions reflects the influence of many environmental factors. The effect of the most important factors (the concentration of organic matter and its components and sulfates, the temperature of aquatic environment, and the abundance and activity of sulfate-reducing bacteria) on the process of sulfate reduction in the aquatic environment and bottom sediments in water bodies is considered.     

The use of faecal bacteria as a tracer for sewage sludge disposal in the sea

Samples of bottom sediment taken in an area used for marine dumping of sewage sludge were examined for the presence of Escherichia coli and coliform bacteria. Using a simple membrane filtration technique, an extensive network of stations was sampled and examined at sea in under two days. The results obtained were in good agreement with seabed drifter and radioactive tracer studies, and suggest that the use of bacterial indices may be a useful means of estimating the distribution of sewage sludge solids in bottom sediments.     

Wave- and current-induced bottom shear stress distribution in the Gulf of Lions

Simulations of both currents and waves were performed throughout the year 2001 to assess the relative contribution of each to their overall erosive potential on the Gulf of Lions shelf. Statistical analysis of bottom shear stress (BSS) was compared to sediment grain-size distribution on the bottom. The hydrodynamic features of the bottom layer coincide with the distribution of surficial sediments, and three areas with different hydro-sedimentary characteristics were revealed. (i) The sandy inner shelf (<30 m) area is a high-energy-wave dominated area but may be subjected to intense current-induced BSS during on-shore winds along the coast and during continental winds mainly in the up-welling cells. (ii) The middle shelf (30–100 m) is a low-energy environment characterised by deposition of cohesive sediments, where the wave effect decreases with depth and current-induced BSS cannot reach the critical value for erosion of fine-grained sediments. (iii) The outer shelf, which has a higher bottom sand fraction than the middle shelf, may be affected by strong south-westward currents generated by on-shore winds, which can have an erosive effect on the fine-grained sediments.     

Adsorption behaviour of dibutyl phthalate on marine sediments

Laboratory experiments were carried out to investigate the adsorption behaviour of dibutyl phthalate (DBP) on marine sediments collected from five different sites in Victoria Harbour, Hong Kong. DBP adsorption can be well described by the Langmuir isotherm. The maximum DBP adsorption capacity (Q_max) of the marine sediments ranges from 53 to 79 mg g⁻¹, which has a positive correlation with their organic content. Around 90% of the organic can be removed from the sediments with treatment by H₂O₂ oxidation, and the Q_max then decreases to a range between 13 and 22 mg g⁻¹. The black carbon content of the sediments has a much greater DBP adsorption capacity than does the natural organic matter of the sediments. The amount of DBP adsorbed on the sediments increases as the salinity of the marine water increases.     

Dynamics of microelement concentrations in bottom sediments of the marginal filter (Razdol’naya R.–Amur Bay)—Result of biogeochemical processes

Atomic-emission spectroscopy was used to determine the concentrations of Be, Ga, Nb, Ta, Y, Zr, Hf, Sc, Mo, U, and Th in subcolloidal, medium-pelite, coarse-pelite, fine-aleurite, and coarse-aleurite fractions of bottom sediments of Razdol’naya R. marginal filter. The concentrations of examined elements are maximal for the subcolloidal sediment fraction. The average concentration (n = 10) of elements in the soil and fluvial sediments (upstream of the mixing zone) were calculated and taken as background concentrations. The highest concentrations of Y, Be, U was shown to correspond to sediments in the zone of fresh and sea water mixing, which is accompanied by flocculation and sorption on Fe and Mn hydroxides and clay minerals (hydromica in fluvial sediments, and smectite in marine sediments).     

Methanogenesis and organic matter destruction in bottom sediments of technogenic water bodies

Traits have been revealed in the microbial processes of methane formation and organic matter destruction in bottom sediments of technogenic water bodies, in which at the abundance of C_org compounds, including toxic, dissolved oxygen deficiency, and low redox potential, organic matter decay in sediments is mostly anaerobic with the predominance of methanogenesis and sulfate reduction. Data on major microbial processes are used to calculate the total sludge destruction; it is maximal in the sediments of low-toxicity technogenic water bodies; organic matter destruction in them is mostly due to methanogenesis; it is minimal in high-toxicity water bodies, the share of sulfate reduction in them increases, and that of methanogenesis decreases.     

Bioremediation of petroleum hydrocarbons in anoxic marine sediments: Consequences on the speciation of heavy metals

We investigated the effects of biostimulation and bioagumentation strategies applied to harbor sediments displaying reducing conditions and high concentrations of petroleum hydrocarbons and heavy metals. We compared the microbial efficiency of hydrocarbon removal from sediments maintained for 60 days in anoxic conditions and inoculated with acetate, sulfate-reducing bacterial strains and acetate and sulfate-reducing bacteria. All treatments determined a significant increase in the microbial growth and significant decreases of hydrocarbon contents and of redox potential values. The addition of sulfate-reducing bacterial strains to the sediment was the most efficient treatment for the hydrocarbon removal. In all experiments, significant changes of the heavy metals’ phase repartition were observed. The results reported here suggest that the biodegradation of petroleum hydrocarbons in anoxic marine sediments may be enhanced by stimulating microbial anaerobic metabolism, but care should be applied to monitor the potential changes in the mobility and bioavailability of heavy metals induced by bio-treatments.     

Radiocaesium distribution in the bottom sediments of the Kara Sea

The article presents the results of radiogeochemical studies carried out by the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, RAS (IGEM RAS), in the Kara Sea and the estuaries of the Ob and Yenisei rivers in 1995–2003. The studies were carried out onboard the Akademik Boris Petrov research vessel, belonging to the Institute of Geochemistry, RAS. Based on studies of circa 1500 samples of bottom sediments, taken from 172 marine and river stations, a map of ¹³⁷Cs distribution in the surface sediments has been compiled. Four zones of radiocesium overactivity (>15 Bk/kg) have been identified: Novaya Zemlya Zone, Vaigach Zone, Ob Zone, and Yenisei Zone. The zones have different radiocesium concentration levels, as well as different input sources, but all of them have formed under the influence of complex geochemical barriers. Data from 47 sectioned cores of bottom sediments, sampled in Ob and Yenisei overactivity zones, demonstrate distinct differences in the vertical radiocesium distribution. These differences have been shown to be due to many-year oscillations of suspended silt discharge, which are main transfer agents of solvable and poorly solvable radiocesium forms and to be independent of sedimentation conditions and the geochemical characteristics of the deposition environment.     

Relationship between P- and S-wave velocities and geological properties of near-surface sediments of the continental slope of the Barents Sea

Seismic velocities ( V _p and V _s) of compressional (P-) and shear (S-) waves are important parameters for the characterization of marine sediments with respect to their sedimentological and geotechnical properties. P- and S-wave velocity data of near-surface marine sediments (upper 9 m) of the continental slope of the Barents Sea are analysed and correlated to sedimentological and geotechnical properties. The results show that the S-wave velocity is much more sensitive to changes in lithology and mechanical properties than the P-wave velocity, which is characterized by a narrow range of values. The correlation coefficients between S-wave velocity and silt and clay content, wet bulk density, porosity, water content and shear strength are higher than 0.5 while the correlation coefficients of P-wave velocity and the same parameters are always lower than 0.4. Although the relationship between V _s and clay content has been widely described, the data show that V _s is better correlated with silt content than with clay content for the sediments of the area investigated. However, they show different trends. While V _s increases with increasing clay content, it decreases with increasing silt content.     

Retrospective Assessment of Bottom Deposits in Kondopoga Bay,Lake Onega

Long-term observations of the chemical composition of bottom sediments in Kondopoga Bay, Lake Onega, are considered. The present-day state of bottom sediments is characterized, and regularities of variations in the composition and properties of sediments occurring in the zone of influence of wastewaters from a pulp and paper plant (PPP).     

Application of Marine Seismic Profiling to a Ground Water Contamination Study, Aberdeen Proving Ground, Maryland

Continuous high-frequency marine seismic profiling was used to define the extent of geologic units in the offshore areas of J-Field, Aberdeen Proving Ground, Maryland, during March and April of 1988. J-Field is an area that was used by the U.S. Army for disposal of chemical warfare agents, munitions, and organic solvents from the 1950s through the 1970s. A major concern at this site is the subsurface migration of hazardous wastes into offshore areas and eventually into the Chesapeake Bay. A 150-foot (45.7 meter) deep paleochannel containing Pleistocene age fluvial and estuarine sediments was identified from boreholes constructed onshore. The paleochannel sediments consist of three lithic units. From bottom to top these units consist of gravel and sand, massive silty and sandy clay, and interbedded sand and clay. The seismic profiles were used to identify the extent of these units and map them in offshore areas. An accurate knowledge of the distribution of the geologic units in onshore and offshore areas is important to the investigation because the coarse-grained paleochannel sediments may provide a preferential flow path for contaminated ground water and the fine-grained sediments may impede the movement of contaminants into deeper aquifers.     

Effects of tides and weather on sedimentation of iron‐oxyhydroxides in a shallow‐marine hydrothermal environment at Nagahama Bay,Satsuma Iwo‐Jima Island,Kagoshima, southwest Japan

Nagahama Bay of Satsuma Iwo‐Jima Island, southwest Japan, is an excellent place for studying sedimentation of iron‐oxyhydroxides by shallow‐marine low‐temperature hydrothermal activity. Its fishing port has a narrow entrance that limits exchange of seawater between the bay and open ocean, allowing the accumulation of fine‐grained precipitates of iron‐bearing materials (Fe‐oxyhydroxides) on the seafloor. The fishing port is usually filled with orange‐ to brown‐colored Fe‐rich water, and deposits >1.5 m thick Fe‐rich sediments. To elucidate the movement and depositional processes of the Fe‐rich precipitates in the bay, we conducted continuous profiling of turbidity throughout the tidal cycle and monitoring of surface water. The results showed that clear seawater entered the bay during the rising tide, and turbid colored water flowed into the ocean during the ebb tide. Neap tide was found to be an optimal condition for sedimentation of Fe‐oxyhydroxides due to weak tidal currents. Storms and heavy rains were also found to have influenced precipitation of Fe‐oxyhydroxides. Storm waves disturbed the bottom sediments, resulting in increased turbidity and rapid re‐deposition of Fe‐oxyhydroxides with an upward‐fining sequence. Heavy rain carried Fe‐oxyhydroxides originally accumulated in nearby beach sands to the bay. Our findings provide information on optimal conditions for the accumulation of Fe‐rich sediments in shallow‐marine hydrothermal settings.     

Impact of the chemical composition of bottom sediments on internal phosphorus load

Examples of the impact of the content of organic matter and compounds of Al and Fe in freshwater sediments on the phosphorus release from the bottom are studied. The relationships between the phosphorus release from bottom sediments and organic matter concentration in sediments of 22 lakes of the world are obtained and discussed as a result of generalization of actual data.     

Relationships between bacterial-algal proliferating and mass extinction in the Late Devonian Frasnian-Famennian transition: Enlightening from carbon isotopes and molecular fossils

The five major mass extinctions which occurred in the transition of the Ordovician-Silurian (440 Ma), Late Devonian Frasnian-Famennian (F-F) (370 Ma), Permian-Triassic (250 Ma), Triassic-Jurassic (205 Ma) and Cretaceous-Paleogene (65 Ma) are significant phenomena in the Phanerozoic global environment and organic evolution. Their corresponding extinction rates of marine invertebrate at the level of genus and family are 60% (genus) and 26% (family), 57% and 22%, 82% and 51%, 53% and 22%, …     

Long-term variations in the granulometric composition and spatial distribution of bottom sediments in the Northern Caspian Sea

Granulometric analysis was carried out for bottom sediment of the Northern Caspian Sea sampled in 2001. The results of analysis were used to map the spatial distribution of different types of bottom sediments and evaluate their areas. To identify the changes that have taken place in the granulometric composition and spatial distribution of bottom sediments in a transgression period, the obtained materials were compared with data of the previous survey. The main factors of sediments dynamics are shown to be higher continental runoff and sea transgression.     

Luminescence dating of marine sediments from the Sea of Japan using quartz OSL and polymineral pIRIR signals of fine grains

Luminescence dating has long been used for chronological constraints on marine sediments due to the ubiquitous dating materials (quartz and feldspar grains) and its applicability over a relatively long time range. However, one of the main difficulties in luminescence dating on marine sediments is partial bleaching, which causes age overestimations. Especially, partial bleaching is typically difficult to be detected in the fine grain fraction (FG) of marine sediments. The recently developed feldspar post-IR IRSL (pIRIR) protocol can detect non-fading signals and thus avoid feldspar signal instability. In the current study, fine grains were extracted from a gravity core in the northern Sea of Japan, and the aim is to test the feasibility of using different luminescence signals with various bleaching rates to explore the bleaching conditions of fine grain fraction in marine sediments. The results suggest that the quartz OSL signal and polymineral pIRIR signals at stimulation temperatures of 150 °C and 225 °C (pIRIR₁₅₀ and pIRIR₂₂₅) of FG were well bleached prior to deposition. The OSL ages were used to establish a chronology for this sedimentary core and the resulting age-depth relationship is self-consistent and comparable with radiocarbon dates. We conclude that different luminescence signals with various bleaching rates can be used to test the bleaching conditions of fine grain fraction in marine sediments; and the luminescence dating can be applied to marine sediments with great potential.     

Peculiarities of Heavy Metals Accumulation in the Bottom Sediments and Higher Aquatic Plants of the Ivan'kovo Reservoir

Concentrations of heavy metals in the bottom sediments of the Ivan'kovo Reservoir bays are analyzed. The role of higher aquatic plants in the processes of heavy metals accumulation and transformation in bottom sediments is studied. Uneven distribution of microelements in the bottom sediments is found to be typical of the bays, which is related to the character of heavy metals input in the bays and to processes occurring inside the bays themselves.     

黄海两钻孔岩芯的古地磁分析

本文利用沉积物中泥炭层C14的年龄测定,把样品极性方向与A·Cox的极性年表加以对比,发现在黄海两个钻孔的沉积物中有与布容正向期内拉尚反向事件相对应的层位,并估算了沉积物生成年代及该海域的沉积速率     

Accumulation of Polychlorinated Biphenyls in the Sheksninskii Pool of the Rybinsk Reservoir

Specific features of polychlorinated biphenyl (PCB) distributions in bottom sediments, benthos, and fish of the Sheksninskii Pool of the Rybinsk Reservoir are discussed. It is shown that 95% of the total PCB is accumulated in bottom sediments. Mapping of PCB-polluted bottom sediments with allowance for the sediment type and bed relief is proposed. The obtained data along with coefficients of accumulation in the bottom sediments–benthos–fish chain were used to evaluate the maximum concentration of PCB in bottom sediments at which the environmental risk of fish metabolism disturbance will be minimum. It is shown that once the PCB discharge into the water body is completely eliminated, their presence in the system will still be an ecological hazard for 25–30 years.