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The Lhasa River, as one of the major rivers on the Tibetan Plateau, is of great value for the study of climate and environmental changes on the Tibetan Plateau. In this paper, the grain size and the mineralogical and geochemical characteristics of the sediments from the Lhasa River were investigated. The results show the following: (1) The average grain size of the Lhasa River sediments is coarse (65.5% sand, 23.6% silt), and the sorting is overall poor; the skewness is mostly positive, and the kurtosis is wide, which reflects the obvious characteristics of river sand deposition. (2) The mineral composition of the Lhasa River sediments is dominated by quartz (38.4%), feldspar, and plagioclase feldspar, followed by clay minerals, and the content of carbonate minerals is relatively low; the content of clay minerals in the illite content is as high as 83.3%, while the chlorite content is slightly higher than kaolinite, and smectite content is very low. The chemical index of illite is less than 0.4, indicating that illite is mainly iron-rich magnesium illite. (3) The value of the chemical weathering index (CIA) of the sediments is low, implying that the sediments are in a weak–moderate chemical weathering state and dominated by physical weathering. Comprehensive analyses further revealed that the weathering process of the sediments in the Lhasa River was influenced by both climate and lithology, i.e., sediment composition is influenced not only by chemical weathering in a dry, cold climate but also by physical weathering of granites exposed over large areas. The results of this study can provide scientific references for further in-depth research on the environmental and climatic effects of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Alluvial sedimentary records in the North China Plain are essential in expanding flood history and understanding hazard patterns in the Yellow River basin where inundation risk exists and would probably increase under future global change. A detailed study of the Longwangmiao profile in the lower Yellow River floodplain reveals ancient flooding records over the late Holocene. Slackwater deposits are distinguished by typical sedimentary features and share similarities with those in the upper and middle Yellow River. This indicates that the traditional method can still be applied for paleoflood research beyond the gorge. However, unlike confined bedrock gorges, multiphase flood deposits of slackwater and overbank deposits represent different stages of flood events. These sedimentary assemblages recorded six flooding periods, further confirmed by the analysis of grain size and geochemistry. The profile was broadly subdivided into two flood-poor phases (3.7–6.7 ka, 0.8–1.7 ka) and three flood-rich phases (before 6.7 ka, 1.7–3.7 ka, after 0.8 ka) based on the dating results. Compared with the existing related research in the nearby area, the synchronous deposition cycles of floods and inter-floods are mainly controlled by the hydrodynamic conditions of the old Yellow River course. This study provides an analogue of paleoflood research in the lower Yellow River and similar alluvial plains. It explores the potential of interlinking paleoflood records in the whole Yellow River basin. [ABSTRACT FROM AUTHOR]

In Kosovo, the supply of potable water from water sources is represented by about 40%. This study represents the geochemical analyses of sediments, spatial and statistical analyses of major elements in sediments (fraction <63 µm) of water sources in Drini i Bardhë river basin. For better understanding of geochemical consistence of sediments ICP-MS was used and the amounts of P and S were determined by ICP-OES. By comparing the concentrations of Ba, Se and P elements with the existing criteria, it was found that 26 from 50 sample points exceed recommended norms, that cause low/significant toxic effects and 23 from 50 sample points include anomalies of analysed elements. In terms of statistical interpretation the average concentration of the studied elements have decreased in such order: Ca>Al>Mg>K>S>P>Na>Ba>Sr>Li>Rb>B>Ga>Cs>Be>Se. In terms of correlation analyses elements such as: Li, Be, Mg, P and Ba did not show significant positive correlation with any element. Cluster analysis of R-modality show a branch of dendogram linked with Ca, Al, Mg, S, K, P, Na, Ba, Sr, Cs, B, Ga, Se, Be, Rb and Li. Spatial distribution maps of major elements show that high concentration of Li, Ca and Ba were located mostly in the north part, high concentrations of B, Na, Mg, Sr and Cs were located in the north-east part, high concentrations of Be and Al were located in the north and south part and high concentrations of P, S, K and Rb were located mostly in the south-east part of the catchment basin. This high concentration of elements is impacted by the lithology of rocks and from minor influence of human activity (the case of P). [ABSTRACT FROM AUTHOR]

Typhoon is an important meteorological phenomenon that affects the living and development of human beings on the southern China coast. However, there is still lack of clarity in the paleo-typhoon history and its influence on the evolution of the ancient human settlement environment since the mid-Holocene. Here, we identify six typhoon-like deposits from a core retrieved from the northern South China Sea shelf, close to the Pearl River Estuary, based on accelerated mass spectrometry 14C dating, grain size, and geochemistry. The sand fractions, CaO, Sr, SiO2/TiO2, and SiO2/Al2O3 were used to indicate the typhoon-like deposits. Results show that the ages with high-frequency typhoons are present ~200–300 cal yr BP, ~800–1000 cal yr BP, ~1500–1700 cal yr BP, ~2000–2100 cal yr BP, ~2400–2500 cal yr BP, and ~2700–3000 cal yr BP. Our results are comparable to the records from adjacent regions. Significantly, the vast tides occurred in the duration of ~2700–3000 cal yr BP in southern China, which probably caused the ancestors' migration to the inland. Further studies are needed to deeply study the paleo-typhoon history in the southern China coast to verify our results. [ABSTRACT FROM AUTHOR]

This study evaluate the Chemical classification of sediments in JVX well, Greater Ughelli Depo belt Niger Delta Basin. Samples collected from different intervals were analyzed using geochemical proxies. Agbada Formation was suggested for the sampled intervals due to the presence of shaleand sand intercalations. lithofacies units gotten from sampled intervals are Sand, Shale and Shaly sand facies. The sands are milky in colour, translucent to opaque, medium to coarse grain, subangular to subrounded and are moderately sorted while the shales are Grey in colour, fissile with the presence of lignite streak and calcareous materials. The geochemical studies of the sediments revealed that SiO2 is the dominant oxide followed by Al2O3 and Fe2O3 which constitutes over 90% while others like CaO, K2O, TiO2, Na2O and MgO constitute 10%. The sediments were classified as Fe-shale, Fe-sand and Quartz arenite. Samples that plotted in the quartz arenites region suggests an intense degree of weathering and reworking. The SiO2/Al2O3 ratios for the sediments in the well are appreciably high indicating that the samples have been heavily weathered, evidenced from the enrichment of quartz and depletion of feldspars. Also, the relatively high concentrations of Fe2O3 and TiO2 is an indication of iron-titanium minerals such as haematite and anatase retiles. [ABSTRACT FROM AUTHOR]

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Major (CaCO3, TOC, and Fe2O3), minor (MnO and TiO2) and trace (Zr, Cr, V, Zn, Cu, Ni, As, Pb, and Hg) elements from surface riverbed sediments were determined at 66 locations in deltaic environment, along St. George distributary and in the interdistributary depressions of the Danube Delta. The studied area is characterized by terrigeneous, either non-carbonated or low calcareous sediments, quite poor in organic matter. Most of the studied heavy metals showed high spatial variability, generally with higher concentrations in interdistributary depressions and adjacent canals, as well as on the meander Mahmudia (M1). Ni, Cu, and Cr showed concentrations frequently exceeding the quality criteria set in the Romanian legislation. Contamination Factor (CF) and Pollution Load Index (PLI) were used to assess the level of heavy metal pollution in the studied area. [ABSTRACT FROM AUTHOR]

The Turonian sediments of Yola Sub-basin(the Jessu Formation) formed part of the stratigraphic sequence of the Northern Benue Trough. The sediments were believed to have been deposited in shallow marine environment. Integrated molecular (biological markers) and elemental geochemistry (mineralogical, major and trace elements)were conducted on the Turonian sediments of Jessu Formation with the aim to determine the provenance (source origin) and paleodepositional conditions of organic matter within the sediments. Biomarker parameters such as n-alkanes, isoprenoids, tricyclic and tetracyclic terpanes, regular steranes and diasteranes suggests a significant contribution of both terrigenous and aquatic organic matter input and suboxic paleodepositional condition with low salinity stratified water column and moderate preservation. Elemental geochemistry shows quartz as the most dominant mineral followed by kaolinite, glauconite, montmorillonite, pyrite, illite, chlorite, hematite and calcite whilst major elements are dominated by SiO2, Al2O3, Fe2O3, K2O, CaO, MgO, Na2O, TiO, P2O and MnO suggesting terrigeneus origin and continental shallow marine environment. Trace elements concentration within the samples shows presence of Ba, V, Rb, Sr, Ni, Cr, Ga and Cu indicative of seawater and suboxic to relatively anoxic marine environment. However, the organic matter within the Turonian sediments of Jessu Formation were sourced mainly from terrigeneous and aquatic and, deposited under suboxic condition in marine setting. [ABSTRACT FROM AUTHOR]

Mineral dust released from the desert is one of the important components of atmospheric aerosols. Arid and semi-arid deserts, sandy lands in northern China and their adjacent Gobi Desert lands in northern China and neighboring Mongolia (hereinafter referred to as Gobi) are potential sources of mineral dust in Asia. However, there is currently a lack of systematic studies on the characteristics of major elements in the potential mineral dust source area. This study investigates the major elements of 310 surficial sand samples in the stabilized and semi-stabilized dune fields from 12 deserts/sandy land and Gobi in northern China and southern Mongolian Gobi and compiles published data. We identify four regions with distinct geochemical characteristics: (1) Taklimakan, Kumtag and Qaidam deserts in western China; (2) Badain Jaran, Tengger, Hobq, and Mu Us deserts in the central and western regions of northern China; (3) Hulun Buir, Onqin Daga and Horqin sandy lands in northeast China; and (4) Gobi and Gurbantunggut deserts. The spatial distributions of the SiO2 and CaO contents in Chinese deserts are highly variable. The average content of SiO2 generally reflects an increasing trend from west to east, while the average content of CaO shows a decreasing trend from west to east. We demonstrate that the spatial variation of major elements is likely controlled by two key scenarios: the composition of source rocks and the mineral maturity caused by the supply of fresh materials. The SiO2/(Al2O3+K2O+Na2O) ratio of desert sediments is relatively lower in western China and may be caused by high ferric-magnesia and high carbonate minerals; this ratio is relatively higher in the northeast sandy lands and may be linked to a lack of fresh material supply and the presence of high K-feldspar minerals in source rocks. The deserts can be further distinguished by ternary diagrams with SiO2/10-CaO-Al2O3, (K2O+Na2O)-CaO-Fe2O3 and CaO-Na2O-K2O. The comparison of major elements between desert sediments and loess suggests that the western and/or central deserts in China may be the potential provenances of loess on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Abstract Major and trace elements of sediments from two gravity cores (10YDY09 and 12I712) in the northeastern Indian Ocean have been analyzed for sediment provenance and the relationship of the sediments with climate change since 50 ka. The rare earth element (REE) compositions were analyzed, and the sediment contributions were estimated for the major potential sources, including the Ganges-Brahmaputra (G-B), Godavari-Krishna (G-K) and Mahanadi Rivers. Our results showed that the sediments in the study area were a mixture of sediments discharged from the above three rivers. The sediment contribution of the G-K Rivers increased notably during the Holocene when the rainfall increased, which may be caused by the strengthening of the East Indian Coastal Current (EICC) and the resulting large amounts of sediments supplied by the G-K Rivers. The higher sediment contribution from the G-B Rivers demonstrated the role of the Active Channel in transporting sediments to the distal Bengal Fan. During the last glacial maximum (LGM), especially in the late period, the Indian summer monsoon weakened, but the winter monsoon strengthened, resulting in a decrease in chemical weathering and elemental enrichment in the northeastern Indian Ocean. Conversely, when the rainfall was low, the chemical weathering strengthened and K 2 O/TiO 2 ratios were lowered due to the longer weathering time and resulting sediment potassium loss. However, when the sea level reached a certain height during the Holocene, the fluvial sediments could not easily enter deep-water environments through submarine channels, which were well developed in the Bengal Fan. Highlights • The major and trace elements of two cores were analyzed for sediment provenance. • The role of the Active Channel in the formation of the Bengal Fan was discussed. • The influence of the sea level fluctuations and rainfall changes over the past 50 ka was evaluated. • Coastal currents driven by the monsoon winds are key forces in sediment transport. [ABSTRACT FROM AUTHOR]

To establish the depositional environment of the surface sediments in the Central Indian Basin, Indian Ocean, major and trace element compositions of different sediment types were studied. The study area composed of terrigenous–siliceous transition, calcareous, siliceous, and red clay sediments. The sediment type changed due to various physico‐chemical conditions with varying proportions of biogenic, hydrogenetic, early diagenetic, and detrital inputs. An oxidative environment is present throughout the basin with variable intensity. The terrigenous input was variable in all sediment types, while its signature was traceable up to 15.30°S latitude. The variable distribution pattern of Mnexcess and Feexcess indicate that apart from continental source, there were additional sources of supply for both these elements, with which most of the trace metals like nickel, copper, chromium, vanadium, yttrium, rubidium, and thorium were associated. The Al/Ti ratios of the sediments indicate a terrestrial influence of fluvial nature up to as far as 14°S latitude while, in the calcareous zone, the influence of volcanic precursors was observed. The present study envisages that Alexcess in the sediments adjacent to the ridges and fracture zones might indicate that Al in these areas is not entirely derived from the continental source. [ABSTRACT FROM AUTHOR]

Organic-rich sapropel sediments were repeatedly deposited in the eastern Mediterranean Sea (EMS), in response to insolation-driven freshwater forcing. However, the exact freshwater sources and causal associated paleoclimate-related processes remain unresolved. Sapropel S5, formed during the insolation maximum of the last interglacial, is one of the most intensely developed sapropels of the Late-Quaternary. Here, detrital sediments of sapropel S5 obtained from 8 cores, together with 13 EMS surface samples, are analyzed for major elements, rare earth elements (REE), and Sr and Nd isotopes. This permits a basin-wide investigation of the source and distribution of river-borne material to the EMS for sapropel S5, and its comparison to the present-day and the Holocene sapropel S1 period. During the sapropel S5, there was minor Saharan dust input. The marked east–west geochemical gradient in S5 detrital sediments across the EMS is therefore attributed to mixing between fluvial contributions, being Nile discharge, Aegean/Adriatic riverine inputs, and Libyan-Tunisian paleodrainage fluxes. The offshore distribution of Nile sediments during sapropel S5 was comparable to those during S1 and the present. The Nile sediment contribution appears to be only dominant for the Levantine Basin, decreasing to negligible values south of Crete. This rather limited sediment delivery, despite inferred increased runoff during S5, is related to denser vegetation cover on the Ethiopian Highlands. By contrast, small rivers around the Aegean (and Adriatic) Sea brought large amounts of detrital material into the EMS. This is particularly noticeable around Crete and the northern Ionian Sea. The enhanced riverine input is probably due to strong precipitation seasonality over the northern EMS borderlands, particularly for the early phase of the last interglacial maximum. Furthermore, there are substantial fluvial contributions from the Libyan-Tunisian margin to the Ionian Sea sediments, in particular during the last part of sapropel S5. The inferred river-borne material was transported via paleodrainage systems reactivated by intensified monsoon precipitation, and derived from central-Saharan mountains. Compared to sapropel S1, these S5-related paleodrainage fluxes were not only stronger, but also had a more predominant provenance from eastern rather than western Libya. In addition, a similar, averaged endmember of Saharan dust sources is revealed by REE signatures. [ABSTRACT FROM AUTHOR]

The present study aimed to geochemical speciation of metals in the surface sediments of the northern Persian Gulf. Metal contents in the sediment were observed in the order: Al > Fe > Cr > Ni > V > Zn > Cu > Co > As > Pb > Cd. The results of sequential extraction procedure revealed that all metals were predominantly associated with the residual fraction. Among the metals, Cu and As exhibited higher bioavailability. The risk assessment code (RAC) indicated that Cu, As and Cd had medium environmental risk at some sampling sites. Based on enrichment factor (EF), Cd and As had moderate to significant enrichment. [ABSTRACT FROM AUTHOR]

Heavy metals, which may result from chemical leaching of bedrock, water drainage, and runoff from banks, the discharge of urban industrial and rural agricultural wastewaters, are widely present in water and sediments. Metal concentrations in aquatic ecosystems are usually monitored by determining their concentrations in water and sediment samples. The main purpose of this study was to examine the levels of eight heavy metals (Cr, Cd, Cu, Mn, Fe, Pb, Zn, and Ni) in surface water and sediments in the Chah Nimeh reservoir. Seven sampling sites were predefined in different locations of the reservoir. The concentrations of heavy metals were measured in the surface water and sediments of Chah Nimeh reservoir. A preliminary study of heavy metals in the surface water and sediments was determined. The obtained results showed that, in general, the heavy metal concentrations in water and sediments did not exceed WHO guidelines (except Cd). The concentrations of heavy metals in sediments were found to be considerably higher than those obtained in reservoir water. Generally, heavy metal concentrations of the sediments were found to decrease in the sequence of Fe > Mn > Zn > Ni > Pb > Cr > Cd > Cu. The findings of this study indicated a general absence of serious pollution in the Chah Nimeh reservoir. [ABSTRACT FROM PUBLISHER]

Multi-proxy analysis of two marine sediment cores (MS27PT and MD04-2726) from the Nile continental slope provides evidence of changes in Nile sediment discharge related to changes in Ethiopian African Monsoon (EAM) precipitation, and allows us to reconstruct changes in Nile River runoff, vegetation and erosion in the Nile headwaters. Sediment element composition and neodymium isotopic composition reveal significant changes in clastic sediment provenance, with sources oscillating between a Saharan aeolian contribution during the Last Glacial Maximum/deglacial transition and during the Late Holocene, and a Blue/Atbara Nile fluvial contribution during the African Humid Period (AHP). This study provides a new understanding of past environmental changes. Between 14.6 and 14.13 ka there was a major input of sediments from the Ethiopian Highlands, consistent with a stronger EAM at that time. Climate in the Nile basin was wetter between 14.8 and 8.4 ka, with a corresponding increase in Blue Nile water and sediment discharge via the main Nile into the Eastern Mediterranean. The gradual climatic transition from the AHP to the present-day dry climate was reflected in a decrease in Blue Nile sediment deposition and flood discharge between 8.4 and 3.7 ka, with aridity at a maximum between 3.7 and 2.6 ka. The onset of drier conditions in the Blue Nile basin seems to have begun before the 8.2 ka cooling event in the North Atlantic. We speculate that the climatic change from the wet AHP to the dry late Holocene may have been a result of a break in the low latitude dynamic equilibrium between climate, vegetation and erosion, which may in turn have affected the climate in higher latitudes. Reduced Nile flow may also have had an impact on Levantine Intermediate Water originating in the Eastern Mediterranean through an increase in intermediate water formation. [ABSTRACT FROM AUTHOR]

For the first time, the occurrence and spatial distribution of several elements, including some toxic metals, have been investigated in sediments of the estuary of the Cávado River (Esposende, Portugal). The pseudo total concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V and Zn in sediments collected at 24 sites covering the tidal part of the estuary were determined. According to the concentrations measured, the Cávado estuary can be considered as non-contaminated. For most of the elements, the concentrations tended to be higher upstream. Only a moderate enrichment in Cr and Ni was detected in a few sites. An important decrease in concentration was observed for the most toxic metals compared to historical data reported in the literature. Several hotspots were identified, but even in those cases the amount of metals stored in the sediments does not represent a toxicological threat to living organisms. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate major elements and heavy metal concentrations of Arsenic (As), Copper (Cu), Chromium (Cr), Cobalt (Co), Vanadium (V), Nickel (Ni), lead (Pb) and Zinc (Zn) in surface sediments of the southern Caspian Sea. Metal contents in the sediment were observed in the order of: V > Cr > Zn > Ni > Co > Cu > Pb > As. Correlations between elements showed that sediment TOM, grain size and chemical composition are the main factors that influence the distribution of heavy metals. According to the pollution load index (PLI), sediments from some sampling sites were polluted. Concentrations of Ni, As, Cr and Cu were higher than sediment quality guidelines at some sampling sites, implying potential adverse impacts of these metals. [ABSTRACT FROM AUTHOR]

The Meihe Basin is a Paleogene pull-apart basin. Long-flame coal, lignite and oil shale are coexisting energy resources deposited in this basin. Ninety-seven samples, including oil shales, coals, brown to gray silt and mudstone, have been collected from the oil shale- and coal-bearing layers to discover the rare earth element geochemistry. The total REE contents of oil shales and coals are 137–256 μg/g and 64–152 μg/g respectively. The chondrite-normalized patterns of oil shales and coals show LREE enrichments, HREE deficits, negative Eu anomalies and negligible Ce anomalies. The chemical index of alteration (CIA) as well as some trace elements is often used to reflect the paleoenvironment at the time of deposition. The results show that fine-grained sediments in both layers were deposited in dysoxic to oxic conditions and in a warm and humid climate, and coals were deposited in a warmer and more humid climate than oil shales. Oil shales and coals are both in the early stage of diagenesis and of terrigenous origin. Besides, diagrams of some major, trace and rare earth elements show that the fine-grained sediments of both layers in the Meihe Basin are mainly from the felsic volcanic rocks and granite, and that their source rocks are mostly deposited in the continental inland arc setting. The analysis of major elements shows that Si, Al, K and Ti, in both layers, are found mainly in a mixed clay mineral assemblage and that Si is also found in quartz. Sodium occurs primarily in clay minerals, whereas Ca is found mainly in the organic matter. In the coal-bearing layer, iron is mainly controlled by organic matter rather than detrital minerals. In contrast, in the oil shale-bearing layer, neither detrital minerals nor organic matter exert a control on the iron content. Analyzing the relationship between rare earth elements and major elements shows that REEs in the oil shales and the coals are both of terrigenous origin and are mainly controlled by detrital minerals rather than by organic matter. In both layers, REEs have no relationship with fine-grained phosphates, and during the weathering process, the REEs were not very mobile and were resistant to fractionation. [ABSTRACT FROM AUTHOR]

To synthetically realize the character of major-element compositions as well as its significance for provenance and paleoenvironment recorded in core sediments of the West Philippine Sea over the last 700 ka, grain size and major elements of 221 bulk sediments, together with major-element compositions in the detrital phase of 16 typical samples, in core MD06-3047 collected from the Benham Rise were analyzed. Both discrimination plot and R-mode factor analysis indicate that vertical changes of major elements are mainly controlled by the sedimentation of nearby volcanic matter and the eolian dust input, whereas influences from marine biologic deposition and hydrothermal activity are minor. In particular, AlO and KO are representative of an eolian dust factor. The variation in the eolian dust factor score is characterized by the obviously glacial-interglacial periodicity and can be well compared with the paleotemperature record of the Antarctic ice core and the evolution of the East Asian winter monsoon (EAWM) recorded in the Chinese loess sequence, and then offers a new proxy for the evolution history of eolian dust input into the study area that is controlled by the EAWM intensity and aridity in the continental source regions of atmospheric dust. [ABSTRACT FROM AUTHOR]

Abstract: A high-resolution study of clay mineralogy and major element geochemistry has been carried out on a high sedimentation rate deep-sea core recovered off the Taitao Peninsula in southern Chili (46°S) to investigate climate and environmental changes in Northern Patagonia since the Late Glacial period (the last 22ka BP). The chronology is based upon stable oxygen isotopes of planktonic foraminifera and AMS radiocarbon dating. Smectite/(illite+chlorite) and Ti/K ratios reveal strong changes of the sedimentary sources between the crustal rocks of the Coastal Range and the volcanic rocks of the Andean Cordillera over the last 22ka BP. Compared to the Holocene, the Late Glacial period was characterized by reduced input of detrital material derived from the high relief of the Andean Cordillera, in agreement with a greater extension of the North Patagonian ice cap that prevented chemical weathering of basalt (smectite production) and induced physical erosion of illite and chlorite from glacial scours. The Glacial period is also characterized by rapid changes of smectite/(illite+chlorite) and Ti/K ratios indicating short-term (centennial-scale) glacier fluctuations. These changes could be the results of southern westerly shifts in the Aysen region alternating periods when glaciers were probably less fed by precipitation (mostly located in the North) and consequently less active to ice accumulation periods. The deglaciation was characterized by a trend towards warmer and more humid conditions, punctuated by a cold and arid period partly coeval with the Antarctic Cold Reversal event. Finally, the Holocene presents warmer and more humid conditions even though short term changes in the smectite/(illite+chlorite) ratio and the δ18O record could be attributed to Neoglacial events in the studied region. [ABSTRACT FROM AUTHOR]

Major, trace and rare earth elements have been measured in sediments of different layers to determine the controls of constituent minerals on the distribution of elements and sediment deposition environment in the Meghna river delta. The geochemical composition of sediments was enriched in SiO2, Ca, Mg and Ba and depleted in Al, Fe, Ti, Mn, and Sr relative to PAAS (Post-Archaen Average Shale) value. The X-ray diffraction and elemental analyses demonstrate the dominant presence of quartz, micas, feldspar, chlorite, amphibole and clay minerals in sediments. The very low contents of trace elements suggest that the oxic condition was more prevalent during sediment deposition of Pleistocene-Holocene period and reflect the massive chemical weathering by biogeochemical reactions. The enrichment of light rare earth elements and La/Yb ratio reflect the intense silicate weathering of crustal materials and the high sediment depositional rate in the Meghna river delta. [ABSTRACT FROM AUTHOR]

Sedimentological, geochemical and particle-size analyses were used to reconstruct the evolution of both trophic state and hypolimnetic anoxia in Lake Bourget (French Alps) during the last century. Radionuclide dating (210Pb, 137Cs and 241Am) confirmed the annual rhythm of laminations in the upper sediment profile. In Lake Bourget, biochemical varves are triplets composed of a diatom layer (spring lamina), a bio-precipitated calcite-rich layer (spring/summer lamina), and a layer rich in organic matter and detrital particles (winter lamina). The onset of eutrophication and the first appearance of an anoxic facies occurred simultaneously and were dated by laminae counting to AD 1943±1 year. Persistent anoxic conditions began in AD 1960. Eutrophication is characterised by drastic increases in the flux of biogenic silica (mostly diatoms), lacustrine organic matter, and larger calcite crystals (15–30 μm). The increase of organic matter also represents a marker of the onset of anoxic conditions in the hypolimnion. Our results show that eutrophication was the main factor controlling anoxia in the hypolimnion. This eutrophication was caused mostly by the inflow of untreated sewage effluents, and to a lesser extent, by input of fertilizer-derived phosphorus during floods of the Rhone River and run-off from the lake catchment. The Rhone River, however, can also be a source of re-oxygenation via underflows that originate during flood events. Oxygenation of the hypolimnion is also controlled by low winter temperatures, which enable turnover of the lake. Thus, global warming, associated with a forecasted reduction in precipitation, might reduce the efficiency of hypolimnetic re-oxygenation in Lake Bourget. [ABSTRACT FROM AUTHOR]

A 12.87-m-long sediment core was retrieved from closed-basin Lake Daihai in the monsoon–arid transition zone of north-central China. Oxides of major elements and their ratios normalized to Al in the AMS-14C-dated core were employed to evaluate chemical weathering intensity (CWI) in the lake drainage basin, which reflects hydrothermal conditions in the study area. Lower CWI periods occurred prior to 14.5 ka BP, and during the intervals ca. 11.7–10.3, 3.5–3.2, 2.6–1.7 ka BP, and 1.2–0 ka BP, indicating relatively low temperatures and moisture availability. Greater CWI during the intervening periods ca. 14.5–11.7, 10.3–9.0, 3.2–2.6, and 1.7–1.2 ka BP, with the maximum CWI at ca. 6.7–3.5 ka BP, imply ameliorated hydrothermal conditions in the lake basin, i.e. higher temperatures and precipitation. Exceptionally low CWI, associated with high CaO/MgO ratio during ca. 9.0–6.7 ka BP, suggests higher evaporation rates in the area under warmer temperature. Overall, CWI displays in-phase variations with changes in organic matter (TOC, TN), carbonate (CaCO3) and pollen assemblages, all of which are related to variations in monsoon effective precipitation. High CWI indicates strong monsoon-induced precipitation, whereas low CWI reflects a weak precipitation regime. The optimum hydrothermal status, recorded by the strongest CWI and maximum monsoon effective precipitation during ca. 6.7–3.5 ka BP defines the Holocene climate optimum (HCO) in the Lake Daihai region. These results indicate that the HCO prevails after the early Holocene in the monsoon–arid transition zone of north-central China. Temperature and precipitation variations during most of the Holocene, inferred from the lake sediments, are due largely to insolation forcing. Dry but warm conditions ca. 9.0–6.7 ka BP, however, probably reflect the complex interactions between insolation and geography (e.g. altitude and local topography). [ABSTRACT FROM AUTHOR]

In 1991, the U.S. Geological Survey (USGS) began the first cycle of its National Water Quality Assessment (NAWQA) Program. The Program encompassed 51 river basins that collectively accounted for more than 70% of the total water use (excluding power generation), and 50% of the drinking water supply in the U.S. The basins represented a variety of hydrologic settings, rock types (geology), land-use categories, and population densities. One aspect of the first cycle included bed sediment sampling; sites were chosen to represent baseline and important land-use categories (e.g., agriculture, urban) in each basin. In total, over 1200 bed sediment samples were collected. All samples were size-limited (<63 µm) to facilitate spatial and/or temporal comparisons, and subsequently analyzed for a variety of chemical constituents including major (e.g., Fe, Al,) and trace elements (e.g., Cu, Zn, Cd), nutrients (e.g., P), and carbon. The analyses yielded total (≥95% of the concentrations present), rather than total-recoverable chemical data. Land-use percentages, upstream underlying geology, and population density were determined for each site and evaluated to asses their relative influence on sediment chemistry. Baseline concentrations for the entire U.S. also were generated from a subset of all the samples, and are based on material collected from low population (≤27 p km−2) density, low percent urban (≤5%), agricultural or undeveloped areas. The NAWQA baseline values are similar to those found in other national and global datasets. Further, it appears that upstream/underlying rock type has only a limited effect (mostly major elements) on sediment chemistry. The only land-use category that appears to substantially affect sediment chemistry is percent urban, and this result is mirrored by population density; in fact, the latter appears more consistent than the former. [Copyright &y& Elsevier]

Large hydropower dams have major impacts on flow regime, sediment transport and the characteristics of water and sediment in downstream rivers. The Gabcikovo and Iron Gate dams divide the studied Danube transect (rkm 1895–795) into three parts. In the Gabcikovo Reservoir (length of 40km) only a part of the incoming suspended sediments were deposited. Contrary to this, in the much larger Iron Gate backwater zone and reservoir (length of 310km) all riverine suspended sediments were deposited within the reservoir. Subsequently, suspended sediments were transported by tributaries into the Iron Gate backwater zone. Here they were modified by fractional sedimentation before they transgressed downstream via the dams. Compared with undammed Danube sections, Iron Gate reservoir sediment and suspended matter showed higher clay contents and different K/Ga and Metal/Ga ratios. These findings emphasize the importance of reservoir–river sediment-fractionation. [Copyright &y& Elsevier]

Basement rocks in the catchment of the Kando River in southwest Japan can be divided into two main groups. Paleogene to Cretaceous felsic granitoids and volcanic rocks dominate in the upstream section, and more mafic, mostly Miocene volcanic and volcaniclastic rocks occur in the downstream reaches. Geochemically distinctive Mount Sambe adakitic volcanic products also crop out in the west. X-ray fluorescence analyses of major elements and 14 trace elements were made of two size fractions (<180 and 180–2000 µm) from 86 stream sediments collected within the catchment, to examine contrasts in composition between the fractions as a result of sorting and varying source lithotype. The <180 µm fractions are depleted in SiO2 and enriched in most other major and trace elements relative to the 180–2000 µm fractions. Na2O, K2O, Ba, Rb and Sr are either depleted relative to the 180–2000 µm fractions, or show little contrast in abundance. Sediments from granitoid-dominated catchments are distinguished by greater K2O, Th, Rb, Ba and Nb than those derived from the Miocene volcanic rocks. Granitoid-derived <180 µm fractions are also enriched in Zr, Ce and Y. Sediments derived from the Miocene volcanic rocks generally contain greater TiO2, Fe2O3*, Sc, V, MgO and P2O5, reflecting their more mafic source. Sediments containing Sambe volcanic rocks in their source are marked by higher Sr, CaO, Na2O and lower Y, reflecting an adakitic signature that persists into the lower main channel, where compositions become less variable as the bedload is homogenized. Normalization against source averages shows that compositions of the 180–2000 µm fractions are less fractionated from their parents than are the <180 µm fractions, which are enriched for some elements. Contrast between the size fractions is greatest for the granitoid-derived sediments. Weathering indices of the sediments are relatively low, indicating source weathering is moderate, and typical of temperate climates. Some zircon concentration has occurred in granitoid-derived <180 µm fractions relative to 180–2000 µm counterparts, but Th/Sc and Zr/Sc ratios overall closely reflect both provenance and homogenization in the lower reaches. [ABSTRACT FROM AUTHOR]

Abstract: Organic carbon-rich sediments are enriched in several redox-sensitive and stable sulfide-forming trace metals (TM) and form an important sink in global TM cycles. In today''s ocean such sediments are deposited in coastal upwelling areas like those in the Gulf of California, off Peru or off the Namibian coast and euxinic basins like the Black Sea. In an attempt to distinguish both environments by their specific TM patterns, some important conclusions may be drawn: 1) The TM enrichment seen in both environments broadly is rather similar. 2) Upwelling sediments are often enriched in Cd and P and depleted in Co and Mn. 3) Sapropels have a tendency towards higher enrichments in Ba and Mo, S, Re, As, Cu, Ni, Sb, and Fe, reflecting the strong sulfidation in an anoxic water column. 4) Upwelling systems cover a broad range of environmental settings where the steepness of the slope, the proximity of H2S to the sediment seawater interface and the intensity of bio-accumulation and regeneration play an important role for TM accumulation. 5) The TM content of anoxic basins is mainly controlled by TM availability in the water column and sedimentation rate. 6) Enhanced bio-productivity is the main switch turning an oxygenated into an anoxic environment. Cretaceous black shales (OAE 2) exhibit TM signatures of both, coastal upwelling areas and sapropels. The strong enrichments in Cd, Mo, Tl, V, Cu, Ni, (Bi), and Sb demonstrate that bio-accumulation and presence of H2S in the water column and associated sulfidation processes persisted during this time interval in large parts of the Proto-Atlantic. The usefulness of Ba as a paleoproductivity-proxy is obscured by diagenesis. The extreme accumulation in Ag and Zn requires either an additional TM source, for instance hydrothermal input, or a different TM seawater composition during the Cretaceous. The geochemical data suggest, that the major driving force for the widespread occurrence of C/T black shales seems to be the increase in volcanic activity and associated CO2-input throughout the Cretaceous. The ocean-atmosphere system operated in a mode different from today during this time interval. After conversion of the “nutrient” CO2 into organic matter the system switched back into the “normal” operational mode. [Copyright &y& Elsevier]

Abstract: Holocene sediments of Lake Steisslingen record sedimentation under different redox conditions. This is proven by the changing depth of the chemocline and the resulting varying extension of laminated sediments from the deepest part of the lake to shallower water depths. Redox fluctuations are additionally reflected by colour changes between red and green and the quality of the nonglacial varves. Major and trace elements were analysed on bulk sediment samples (period between 8200–6200 and 2650–2000 cal a BP) to test their response to the observed changes in past depositional environments. Mn, Mo, U, Fe and S were found to be redox-sensitive elements in Lake Steisslingen. Fe and S are almost entirely fixed in pyrite, because pyrite formation is limited by Fe availability. A parallel distribution of Mo, U, Fe and S between 8200–7200 cal a BP is interpreted as a signal for syngenetic pyrite formation from anoxic and sulfidic hypolimnetic waters. Since bioproductivity was low this must have been caused by conditions favouring a longterm stable stratification of the lake (i.e. high water level, high summer temperatures, ice cover, wind protection and/or low storm activity). Between 6000–2000 cal a BP frequently changing redox conditions from anoxic to dysoxic are assumed. Mo and U curves are mirror images of the Fe, S and Mn variations. This is interpreted as showing diagenetic pyrite formation from pore waters, which is enhanced during times of high Fe availability under rather oxygenated conditions, i.e. when high input of Fe oxy-hydroxides is possible, but when U and Mo cannot necessarily be fixed in the sediments. Changes from slightly disturbed lamination (dysoxic, restricted mixis) to homogenous sediments (oxic conditions, holomixis) cannot be traced within the geochemical record. The observed redox fluctuations between 6000 and 2000 cal a BP are not correlated to changes in bioproductivity, detrital input or cultural influences and must therefore be of a natural, probably climatic origin. The North Atlantic Oscillation is discussed as a possible cause. [Copyright &y& Elsevier]

A total of 39 sediment samples were collected from the El-Kabir River and its major tributaries during the low-flow period of August/September 2001. Of these samples, six were selected for a scan for pesticide residues, polychlorinated biphenyls and polycyclic aromatic hydrocarbons (PAHs). An additional seven samples were analysed for major elements and trace elements. Despite the limited number of samples analysed, it can be concluded that major elements reflect the distribution and chemistry of major rock types in the watershed, the sodium oxide concentrations indicate an early onset of salinization in the coastal plain, dichlorodiphenyltrichloroethane is currently in use in the watershed despite being a banned substance, the PAH contamination is directly linked to an old, disused railway track, and chromium and nickel are the two trace elements showing anthropogenic enrichment, being attributed to leather tanning and metal plating by small-scale industries in the watershed. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility (MS) was measured with high resolution (5 mm) on a 9 m long, 14C dated core from Lake Le Bourget (Savoie, France), spanning the last 7200 years. The strong correlation (R = 0.85) of the MS with the silicate-borne suite of elements (Si, Al, Fe, Mg, K) and anti-correlation with the carbonate content (R = -0.87) allows it to be used as a proxy for the fluctuations of the abundance of riverborne clastic fraction versus authigenic carbonates in sediment. As the Rhône is the only river bringing a significant amount of silicate minerals to the coring site, the MS downstream is interpreted as a proxy of the Rhône suspended load discharge in Lake Le Bourget. This is confirmed over the last 3000 years by the good match with the evolution of hydrological activity of the Rhône as it is known through geomorphological studies of well-dated archaeological sites. Over the last 7200 years, the record is consistent with the regional record of lake water-level fluctuations. While the intensity of the MS signal might be widely affected by the human impact on soil stability, the timing of the period of enhanced hydrological activity appears to be mostly climate-related, and should thus constitute a first step toward a high-resolution (<8 yr) continuous history of hydrological conditions in the NW Alps. [ABSTRACT FROM AUTHOR]

Concentration of heavy metals and natural gross radioactivity were measured in the surface water and sediment of Hazar Lake (Elazıg˘, Turkey). Eight sampling sites were pre-defined in different locations of the lake. A preliminary study on heavy metals (Zn, Fe, Mn, Ni, Cu, Cr, Co and Pb), major elements (Na, K, Ca, Mg) concentrations and natural radioactivity related to 226Ra, gross-α and gross-β radiations in the surface water and deep sediments were determined. The obtained results showed that, in general, the heavy metals (Zn, Fe, Mn, Ni, Cu and Pb) and major elements (Na, K, Ca, Mg) concentrations in water did not exceed WHO (World Health Organization, 1999), EC (Europe Community, 1998), EPA (Environment Protection Agency, 2002) and TSE-266 (Turkish Standard, 1997) guidelines. Generally, heavy metals and major elements concentration of the sediments were found decrease in sequence of Fe > Mg > Ca > Mn > Zn > Ni > Cr > Cu > Co > Pb. The results of this study indicated that a general absence of serious pollution in the Hazar Lake. The results obtained from the radioactivity determination indicate that the surface water radioactivity concentration of 226Ra, gross-α and gross-β were ranging from 0.52 ± 0.02 to 2.02 ± 0.06 Bq/l and from 0.65 ± 0.03 to 2.52 ± 0.07 Bq/l and from 0.01 ± 0.01 to 0.14 ± 0.01 Bq/l, respectively. Deep sediment radioactivity concentrations of 226Ra is ranging from 0.07 ± 0.03 to 0.32 ± 0.07 Bq/g. [Copyright &y& Elsevier]

An intercomparison concerning the concentrations of 23 major and trace elements in recent lacustrine sediments, as determined by Instrumental Neutron Activation Analysis, has been performed by using epithermal neutrons at the Joint institute of Nuclear Research, Dubna, (Russia) and thermal neutrons at the National Institute for Physics and Nuclear Engineering, Bucharest, (Romania). Sc, La, Tb, Yb, Th, Na, Rb, Cs, Ba, As, Sb, Hf, Cr, Fe, Co, and Zn concentrations agreed within one standard deviation, Ce, Sm, Lu, Ca, Br, and Ta concentrations agreed within two standard deviation. The results were interpreted in the framework of the Upper Continental Crust model. The Factor Analysis has shown that all elements form a single cluster, irrespective of the laboratory where the analysis was performed. [ABSTRACT FROM AUTHOR]

The abundance of major components (Fe, Ca, K, and organic carbon) and trace elements was analyzed in surface sediments and core samples from the Colorado River delta (CRD) and the Upper Gulf of California (UGC) using instrumental neutron activation analysis.The spatial distribution patterns of the elements studied are consistent with the model of sedimentary dynamics proposed for this area [Mar. Geol. 158 (1999) 125]: intense tidal resuspension of sediments in the delta with subsequent transport of suspended particulate matter in a southerly direction, followed by sedimentation of fine-grained material in a depocenter near the southwestern margin of the UGC. Concentrations of most of the elements are higher in the surface sediments of this depocenter. The gradual mixing of terrigenous and marine biogenic materials, normally expected for the estuarine sediments, was not detected in the CRD–UGC system because of homogenization of the sediments by tides and wind.Vertical profiles of element contents in samples of the sediment core collected in the depocenter area revealed (i) almost no anthropogenic contamination of the area by environmentally important trace elements such as Cr, Co, Sb, and As; (ii) a twofold decrease of Fe, Sc, Cr, and Co in upper core sediments; and (iii) the enrichment of the sediments at 60–62 cm depth in the core, in calcium carbonate, Ca, Sr, and the Eun/Smn shale-normalized ratio along with a depletion in this layer of Fe, Sc, Cr, Co, light rare-earth elements (REEs), and some other elements of terrigenous origin, presumably caused by the dilution of fluvial terrigenous material by biogenic carbonates, which were probably introduced at this level in the sediments by the action of a strong episodic winter storm, followed by the advective transport of shell fragments from the coastal clam banks or as a result of strong planktonic bloom. [Copyright &y& Elsevier]

South China Sea (SCS) sediments have multiple sources. The quantitative assessment of the potential sources is crucial to understanding the source-to-sink transport processes in the SCS. In this study, 1987 surface sediments were collected from the entire SCS (excluding the Gulf of Thailand). Major elements were measured, and the co-occurrence relationships among the major elements and grain sizes were investigated by utilizing network analysis. Positive matrix factorization (PMF) was used for the identification of potential sources and the quantitative assessment of their relative contributions. Only nine elements (SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, MgO, K 2 O, Na 2 O, TiO 2 , and loss on ignition (LOI)) were chosen for the PMF analysis. The calculated signal-to-noise ratios of MnO and P 2 O 5 were extremely low, making these two elements unsuitable for analysis. Four potential sources were identified from the combined PMF factor profiles and factor contributions, representing a northern and western terrigenous source, a southeastern terrigenous source, a biogenic carbonate source, and a source of sandy sediment on the shelf. The PMF factor profiles correspond to the four communities detected based on the co-occurrence relationships. These results support the validity of the four-factor PMF model. In addition, the spatial trends of the relative contributions of terrigenous elements (TiO 2 , Fe 2 O 3 , Al 2 O 3 , K 2 O, and MgO) are comparable to the pattern of the oceanic currents in the SCS. Therefore, the transport of the terrigenous elements in the SCS is controlled by hydrodynamic conditions. • PMF identified terrigenous and non-terrigenous source of major elements in the SCS. • Network analysis visualized the co-occurrence relationship between major elements. • An agreement is observed between PMF factor profiles and co-occurrence network. • The transport of terrigenous elements is comparable to oceanic currents in the SCS. [ABSTRACT FROM AUTHOR]