Bottom Sediment Cores Research Articles

難透水性湖底堆積物コアの間隙水を用いた霞ヶ浦の完新世における古水文状況の復元

地層が堆積した時代の水文情報が封入されている可能性がある霞ヶ浦湖底の難透水性完新世粘土堆積物を対象に，2地点にてオールコアボーリングを行い，コア間隙水の水質や珪藻化石を用いて，霞ヶ浦の水文状況の変遷に関する復元を試みた。その結果，コア間隙水には堆積当時の古汽水成分が残っており，間隙水は古海水・表流水・地下水の三つの端成分から構成されていた。また，コア間隙水のプロファイルの違いにより2地点の水文環境が異なることが分かった。湖岸に近いSiteK-1は地表水だけでなく地下水の影響を受けやすい環境であるのに対し，湖心付近のSiteK-2は地下水の影響はほとんど受けない環境であったと考えられる。

The effect of fish stocking on mountain lake plankton communities identified using palaeobiological analyses of bottom sediment cores

The artificial introduction of fish into a naturally fishless lake can effectively modify the food web and trophic status of that lake. We observed changes in the zooplankton community after stocking fish in Przedni Staw Polski, an oligotrophic mountain lake in the Tatra Mountains (Poland). Results were compared with observations about a stocked lake that naturally contained fish (Morskie Oko), and with two fishless lakes that served as reference sites. The main change observed in the cladoceran community of Przedni Staw Polski was the elimination of large-bodied Daphnia ~10 years after stocking fish. The introduction of fish also affected the phytoplankton community and resulted in an increase in diatom species related to higher trophic state, most likely due to the fish-induced alteration of the phosphorus cycle. Moreover, all of the studied lakes have been influenced by global and regional climatic and environmental changes, including intensive tourism and acid deposition. Changes in diatom communities were observed after fish stocking even in the lake with a natural fish population, while the zooplankton did not reflect higher fish density. These findings suggest that the natural balance between fish and phytoplankton was destroyed by fish stocking, and although it caused eutrophication in the lake, the higher fish density did not strongly modify the species composition of Cladocera.

Influence of meteorological conditions on the geochemistry of modern bottom sediments exemplified by deposits of Donguz-Orun Lake, Caucasus

Cores of bottom sediments from epiglacial Donguz-Orun Lake (Cis-Elbrusian, Northern Caucasus) have been studied. Here we present descriptions of the sampling techniques, sample preparation, and analytical procedures by the X-ray fluorescence method. The sedimentation rate, estimated by calculation of peaks of the Rb/Sr ratio as well as employing isotope concentrations of 137Cs and 210Pb in the upper parts of the core, permitted us to assume the annual character of the regularly laminated sediment. A statistically significant correlation between the concentration variations of certain chemical elements and their groups in the sediment against normalized meteorological data from the Terskol meteorological station has been revealed. This makes the studied object applicable for development of high resolution palaeoclimate reconstructions.

Spatial and seasonal changes of phosphorus internal loading in two lakes with different trophy

Two lakes with different trophy, Strzeszyńskie Lake and Uzarzewskie Lake (Western Poland), were studied in ex situ experiments with the aid of intact bottom sediment cores in order to analyse the internal loading as well as the spatial and seasonal changes of total phosphorus (TP) release from bottom sediments. It was stated that the TP release from a hypereutrophic Lake Uzarzewskie, despite its earlier restoration using iron treatment, was over 6 times higher than in a mesotrophic one. The observed values in both lakes were higher in the deepest part of the lake than in the littoral zone. TP release in Strzeszyńskie Lake was very similar in all four seasons of the year with the maximum value of 2.8mgPm−2d−1 in winter. TP release did not exceed 1.3mgPm−2d−1 in the littoral zone and in winter its accumulation prevailed over release from bottom sediments. TP release in Uzarzewskie Lake was 44.7mgPm−2d−1 in autumn in the profundal zone and 6.8mgPm−2d−1 in the littoral zone. A domination of P accumulation in sediments over release was observed at both stations in winter (0.33mgPm−2d−1 in the deepest place and 0.62mgPm−2d−1 in the littoral). Knowledge of the internal loading of P in lakes allows managers to compare changes in human impact on the ecosystem and to design practical treatments for limiting their trophy and approaches to the management of restoration measures.

137Cs in sediments of deep lakes

Sedimentation rate of suspensions (0.3–18.2 mm/yr) was determined on the basis of layer-by-layer distribution of 137Cs (global and Chernobyl) in the cores of bottom sediments (BS) from 16 lakes located in the high and moderate latitudes of the Northern Hemisphere. Profiles of 137Cs concentration in the BS cores were analyzed. Sedimentation rates in the limnic zones of deep-water lakes were calculated using 137Cs accumulated in the finely-dispersed component of mineral suspension.

Oil components in the mouth area of the Don R. and in the Sea of Azov: Results of many-year studies

The data given are the results of many-year studying the distribution of the concentrations of main oil components (hydrocarbons, surfactants, and asphaltene-tarry substances) in the water mass, vertically settling particulate matter, and bottom sediment cores taken from the section Lower Don-The Gulf of Taganrog-Russian sector of the Sea of Azov in summer and autumn periods in 2006–2011. Spatial and seasonal regularities in the distributions of the total concentration of oil components and the values of their ratios in water, as well as the spatial and annual features of their accumulation in bottom sediments have been established. Radiological methods have been used for layer-by-layer dating of bottom sediment cores and determine the thickness of the layer that had formed under the maximal anthropogenic impact on ecosystems. The presence of considerable amounts of hydrocarbons of modern biological origin has been revealed in all components of examined aquatic complexes.

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.

Paleomagnetic data on the sedimentation rate near the Mendeleev Rise (Arctic Ocean)

Seven cores of bottom sediments were collected during the cruise of R/V Akademik Fedorov in 2000 along the latitudinal profile crossing the Mendeleev Rise near 82° N, and then studied. The length of cores varies from 240 to 334 cm. In all cores, the boundary of the changing remanent magnetization vector corresponding to the Brunhes-Matuyama boundary was established reliably. In five cores, this boundary is at a depth of 86–102 cm; in two cores, collected to the west of the Mendeleev Rise, at depth levels of 188 and 208 cm. The correlation of paleomagnetic and lithological data demonstrates that the upper boundary of a bench of speckled pelites, overlapped by a bench of variegated pelites, is confined to the Olduvai episode or horizons lying slightly below. The average sedimentation rate of sediments from the Mendeleev Rise during the last 2–2.5 Ma have not exceeded 1–1.3 mm/ka, increasing towards the shelf seas of northeast Russia.

Erosion-accumulative activity of the bottom currents on the continental rise of Brazil

Several high-resolution “SES 2000 deep” seismic profiles and a core of bottom sediments were obtained in cruises 33, 35, and 37 of the R/V Akademik Ioffe in the area of the Columbia channel (continental rise of Brazil, South America). The analysis of seismic facies and direct correlation of acoustic and lithological data indicates that sedimentation in this area is mostly controlled by the contour current of the Antarctic Bottom Water (AABW). The gravity flows from seamounts and continental slope only episodically contributed coarser material to the deposition of the muddy contourites. The mixed gravitite-contourite systems consisting of accumulative bodies (drifts) and erosion channels are the results of interaction of these sedimentation processes.

Clarification of the Properties of Fluctuation of Bottom Sediment Based on Long-Term Monitoring Around the Mouth of the Tama River in Tokyo Bay

With the focus on the characteristics of temporal and spatial fluctuations of the bottomsediment properties and their vertical distributions around the mouth of the Tama River in Tokyo Bay, the properties of surface sediments, such as grain-size distributions and water contents, had been monitored by taking bottom-sediment core samples from several sampling stations around the river mouth with the intervals of 3 month for a period of five years from 2006 through 2010. Based on the monitored data, the impact of flood events which occurred during the survey period on bottom sediment properties and the recovery processes after the flood event were evaluated. This study clarified that seasonal fluctuations of surface bottom sediment qualities clearly appear on river mouth shoals and tidal wetlands and the impact of the river flood was relatively slight and the damages were restored over relatively short period of time after the flood event. On the other hand, the flood event remarkably caused rapid decline of the water content of bottom sediments at offshore of the river mouth, and it took about three years for their bottom sediments to return to its normal as before the flood event. This paper also discusses the recovery process of the sediment properties at the offshore region and shows that the long-term evolution of the sediment properties was caused by the constant settling of new deposition of suspended particles from the water column and accumulation rate was estimated at 2.5 cm per year.

A physicochemical model for the formation of gas hydrates of different structural types in K-2 mud volcano (Kukui Canyon, Lake Baikal)

Earlier, the coexistence of spatially separated layers of gas hydrates of cubic structures I and II (CS-I, CS-II) in the bottom sediment cores from K-2 mud volcano (Kukui Canyon, Lake Baikal) was described. The layers of gas hydrates of different structural types were situated at different depths and overlain by the lacustrine sediments. Hydrate of CS-II contained 13–15 mol.% ethane, whereas CS-I hydrate contained only 3–4 mol.% ethane. We present a physicochemical model explaining the formation of such an unusual natural object. The model suggests that only CS-I hydrate was originally present at the sampling site. Some geologic event (tectonic shifts, landslide, etc.) stopped natural-gas emanation from the mud volcano or increased the heat flow in the hydrate pool. As a result, CS-I hydrate began to dissolve in interstitial water. We assume that the ethane-enriched CS-II hydrate is an intermediate product of the dissociation (dissolution) of CS-I hydrate.

Chloritoid in the bottom sediments of the Akademichesky Ridge of Lake Baikal, an indicator of eolian transportation

We present results of study of Holocene and Late Pleistocene deposits recovered on the underwater Akademichesky Ridge in Lake Baikal. The change in mineral composition and grain size in the bottom sediment core is closely consistent with the change of major diatom complexes marking the Holocene–Late Pleistocene boundary. A high content of chloritoid (up to 14.6%) has been found among the heavy minerals of the sand fraction of Late Pleistocene clays. The concentration of chloritoid in Holocene mud is no higher than 1.2%. The source of chloritoid is chloritoid shales of the Anaya Formation (Upper Proterozoic), widespread in the watershed of the Primorsky Ridge in the upper reaches of the Lena and Anaya Rivers. Chloritoid was transported to the area of the Akademichesky Ridge by predominant western and northwestern winds, which is also evidenced from the absence of mechanical impacts on the surface of its grains. The high contents of chloritoid in the Late Pleistocene sediments are due to the more intense eolian transportation at that time as compared with the Holocene.

Estimation of modern sedimentation rate in Zun-Torei Lake (East Trans-Baikal Region) by 137Cs

On the basis of bottom sediment core dating performed by the technogenic isotope 137Cs, the rate of sedimentation in periodically drying Zun-Torei Lake (water area is up to 300 km2) is estimated at 2.88 mm per year over the last 59 years. This value is in agreement with the data of palinological determinations (3.44 mm per year). High sedimentation rates are attributed to intensive evaporite sedimentation and probable eolian addition of terrigenous material.

Preliminary paleomagnetic studies of lake sediments in Eastern Canada

Nine lake bottom sediment cores from small lakes in Eastern Canada, three of which were oriented to an azimuth, have been analyzed magnetically in an attempt to delineate the paleomagnetic character of the late-Pleistocene and Holocene sediments as an aid to stratigraphy and chronology. Secular variations are discernable in mineral sediments and in overlying organic sediments when intensities are strong enough to produce reliable results. Where organic content was high and intensities low, erratic results were obtained. Short segments of some cores, involving at most several centimetres, showed negative values for inclination, but whether or not these can be related to magnetic reversals or excursions or are spurious results, cannot be determined at this time.

Sedimentation in Proval Bay (Lake Baikal) after earthquake-induced subsidence of part of the Selenga River delta

The paper presents the results of a comprehensive investigation into the recent sediments of Proval Bay. This bay formed during catastrophicflooding of a big block of land as a result of an earthquake in 1862. Comparison of the sketch map of the bay for 1862 with its modern mapshows that the boundary of the Selenga River delta has shifted considerably eastward. The sediments of Proval Bay are sands, silty pelite,and pelitic silt. Terrigenous material is predominant and consists of mineral grains and land plant remains, admixed with diatom frustules andsponge spicules. In the southwestern part of the bay, turbidites and a soil layer have been found. The latter was buried when the water levelin Lake Baikal rose after the construction of the Irkutsk dam in 1959–1964. In the northeastern part of the bay, a peatlike layer has beenfound in the bottom sediment core. It formed in Lake Beloe, which existed in the Tsagan steppe before the 1862 earthquake. According todiatom analysis, this lake was shallow and eutrophic. The sedimentation rates in different parts of Proval Bay differ greatly and directly dependon proximity to the Selenga River. Variations in the geochemical indicators which reflect the ratio of organic to clastic components in thebottom sediments of the bay are controlled by temperature and water level variations in Lake Baikal.

Macro- and microelements in the interstitial water of deep-water areas of the Southern and Middle Caspian Sea

The results of determinations of macro- and microelement concentrations (Mn, Fe, Ba, Sr, Rb, Si, Pb, and U) in the interstitial water in four cores of bottom sediments sampled in the deep-water areas of the Southern and Middle Caspian Sea are compared with the concentrations of these elements in the free water of the Caspian Sea. The data obtained amplify the present-day concept on the geochemical and ecological states of the sea.

The organic carbon in the water, the particulate matter, and the upper layer of the bottom sediments of the west Kara Sea

In three sections in the Kara Sea, the contents of the dissolved and particulate organic carbon (the DOC and POC, respectively), as well as of the organic carbon of the bottom sediments (Corg) were determined. The contents of varied from 6.3 to 2400 μg/l for the DOC and from 0.84 to 12.2 mg of C/l for the POC. The average concentrations for all the samples tested amounted to 200 μg/l for the DOC (n = 78, σ = 368) and 2.7 mg/l for the POC (n = 92, σ = 2.7). The concentrations of Corg in the samples of the upper layer of the bottom sediments of the area treated varied from 0.13 to 2.10% of the dry substance at an average value of 0.9% (n = 21, σ= 0.49%). It is shown that the distribution of the different forms of organic matter (OM) is an indicator of the supply and spreading of the particulate matter in the Kara Sea and that the DOC and POC of the Kara Sea are formed under the impact of the runoff of the Ob and Yenisei river waters. It is found that the distribution of the OM of the bottom sediments in the surveyed area of the Kara Sea is closely related to their grain-size composition and to the structure of the currents in the area studied. The variations in the Corg content in the bottom sediment cores from the zone of riverine and marine water mixing represent the variability of the OM burial.

Temporal Interpretation of Environmental Pollution around Landfill Site Using Core of Bottom Sediments from Pond

Temporal Interpretation of Environmental Pollution around Landfill Site Using Core of Bottom Sediments from Pond

Hydrological changes in the White Sea during the historical period inferred from analysis of dinocysts

According to available historical evidence, colonization of the White Sea region began in the 9th‐8th centuries B.C. [2]. This unique region with ancient residence sites experiences progressively increasing anthropogenic load against the background of natural climatic changes. The intense economic development of the region requires complex ecological and paleogeographic studies aimed at detailed reconstruction of past sedimentation settings. The analysis of dinocysts, which makes it possible to reconstruct various parameters of water masses washing the Arctic shelf, has become a promising method in paleohydrological studies, widely used in recent years [10, 11]. Dinoflagellates, which represent one of the main phytoplankton groups in the Arctic Seas, the White Sea included, form cysts with biopolymer envelopes, which are preserved in sediments. Thus, information on glacial‐hydrological conditions is recorded in marine sediments. In the White Sea, this method was first used for the study of bottom sediments only in 2003 [3, 15]. In this communication, we present the first results obtained during the thorough study of dinocysts in bottom sediment cores from the White Sea, which cover the last 250 years. The study of this microfossil group made it possible to reconstruct in detail changes in glacial‐hydrological settings in the sea and reveal their relations with known climatic‐hydrological events that occurred in neighboring regions during the historical period.

Alpha track analysis and fission track analysis for localizing actinide-bearing micro-particles in the Yenisey River bottom sediments

Distribution of actinides in bottom sediment and flood land soil cores collected from the Yenisey River near the Krasnoyarsk Mining and Chemical Combine (MCC) were analyzed. Actinide-bearing micro-particles were localized using alpha track analysis (ATA) and fission track analysis (FTA). Different types of radioactive micro-particles were found by analysis of the ratios of fission tracks to α -tracks from single particles. The different origin of these particles was confirmed by scanning electron microscopy with energy dispersed microanalysis (SEM-EDX), secondary ion mass-spectrometry (SIMS) and single-particle α -spectrometry. It is established that for most of the radioactive micro-particles ATA and FTA are the only possible techniques to obtain information concerning their origin. For the studied samples of bottom sediments and flood land soils, it was established that 80–90% of alpha radioactivity is attributed to hot-particles with 238Pu and 239,240Pu as the major radionuclides. According to the sequential extraction data most of 238Pu and 239,240Pu is found in the residual low-soluble fraction.