Sediment Fractions Research Articles

Effects of sediment fractions on slump-flow parameters of fine- and coarse-sediment suspensions

• Slump-flow parameters (slump and spread) of fine- and coarse-sediment suspensions are measured using a mini-slump cone. • Effects of fine- and coarse-sediment fractions on the slump-flow parameters are analyzed and empirically formulated by power-law and exponential relations, respectively. • The single- and double-layer models of Roussel and Coussot [22] and Pierre et al. [21], respectively are generalized for a conical-shaped mould in the range of 0 < α ≤ 1 . • The dimensionless slump and spread of fine- and coarse-sediment suspensions are strongly correlated and their empirical relation was compared to the theoretical relations. • The slump-flow parameters and Bingham yield stress exhibit good correlations in both theoretical and empirical analyses, indicating that the slump-flow test may be used to indirectly evaluate the rheology of sediment suspensions. Slump-flow tests on concentrated fine-sediment suspensions (mixtures of clay-silt-water) and coarse-sediment suspensions (mixtures of coarse sediments and a specified fine-sediment suspension) were performed to investigate the effects of sediment fractions on the slump-flow parameters (slump and spread). The slump and spread of fine- and coarse-sediment suspensions decrease with an increase in the sediment fractions, and their empirical equations were proposed. Both experimental and theoretical results show that the slump and spread of sediment suspensions are strongly correlated. Theoretical relations of the Bingham yield stress and slump-flow parameters were also presented for comparison. The slump-flow parameters exhibit a strong correlation with the rheological parameters measured using a conventional rheometer, indicating that the rheological parameters of the tested sample could be indirectly evaluated by a simple slump-flow test.

Distribution and origin of columbite and (Y,REE,U,Th)-(Nb,Ta,Ti) oxide minerals in alluvial soils and river sediments in the area of the Grantcharitsa tungsten deposit, Western Rhodopes, Bulgaria

Columbite-(Fe) and (Y,REE,U,Th)-(Nb,Ta,Ti) oxide minerals – ishikawaite (samarskite group), euxenite-(Y) and uranopolycrase (euxenite group) and minerals of the pyrochlore group (betafite subgroup) were found in the heavy fractions of alluvial soils and river sediments in the area of the Grantcharitsa tungsten deposit. Columbite-(Fe) is the most common mineral among them and is characterized by weak compositional variations (Ta/(Ta+Nb) = 0.04–0.21, Mn/(Mn+Fe) = 0.33–0.5) and lack of fractionation trends. All (Y,REE,U,Th)-(Nb,Ta,Ti) oxide minerals are metamict due to high uranium content (UO2 17–32 wt%). Preserved relationships between minerals in some grains, some features of their chemical composition (chemical similarity: Nb &gt;&gt; Ta, high content of Y, Ti, U) suggest their common origin from one rock source – NYF granitic pegmatites and/or genetically associated granitoids of mantle-dominated origin. It is shown that columbite-(Fe), ishikawaite, euxenite-(Y) and uranopolycrase form zoned crystals and are of magmatic origin, while the betafite subgroup minerals are secondary phases formed under hydrothermal conditions.

Response of modern fluvial sediments to regional tectonic activity along the upper Min River, eastern Tibet

Abstract. The deposition of fluvial sediments in tectonically active areas is mainly controlled by tectonics, climate, and associated Earth surface processes; consequently, fluvial sediments can provide a valuable record of changes in regional climate and tectonic activity. In this study, we conducted a detailed analysis of the grain-size distribution in modern fluvial sediments from the upper Min River, eastern Tibet. These data, combined with information on regional climate, vegetation, hydrology, geomorphology, lithology, and fault slip rate, indicate that modern regional tectonic activity along upper Min River can be divided into three segments. Specifically, fluvial sediments in the Minjiangyuan–Diexi segment are dominated by silts (&lt; 63 µm, 70.2 %), agreeing with low runoff, low rainfall, and high vegetation cover and revealing a windblown origin influenced by the arid and windy climate. These observations are consistent with the low hillslope angle and low relief, all indicating weak activity along the Minjiang Fault. The coarse-grained fraction (&gt; 250 µm) of fluvial sediments in the Diexi–Wenchuan and Wenchuan–Dujiangyan segments increases stepwise downstream, although runoff and rainfall do not change significantly. These patterns correlate well with increases in both regional relief and hillslope angles. Together, these observations imply that regional tectonic activity along the Maoxian–Wenchuan Fault becomes more pervasive downstream along the Min River. The occurrence of well-sorted and well-rounded pebbles of fluvial sediments downstream of Dujiangyan must be related to the long-time scouring and sorting by rivers. This study marks the first development of a new research approach that can characterize regional tectonic activity by analysis of grain-size distribution of fluvial sediments collected from tectonically active regions.

Chemical analysis of mangrove land in north Aceh

This study aims to determine the condition of water quality and the type of sediment fraction in the mangrove area around North Aceh in terms of physical and chemical parameters. Chemical analysis was carried out to test the content of heavy metals Pb, Cu, Cd, Hg, Fe and NH3, DO and physically analyzed to see the type and structure of sediment in addition to temperature, pH, brightness, and salinity in the mangrove area. This study used 3 sampling locations, namely the mangrove area around Pupuk Iskandar Muda (PIM), Lasloka, and Krueng Manee, 12 chemical and physical test parameters with a depth of 1-2.3 m for each sampling. The assessment was carried out through 2 stages of testing, namely in situ test, namely temperature, brightness, salinity, DO, pH. Meanwhile, ex-situ tests were carried out on TSS parameters, lead (Pb), copper (Cu), cadmium (Cd), iron (Fe), mercury (Hg) and ammonia (NH3). The results showed that almost all study areas exhibited that heavy metals were still below the permissible threshold except in the Krueng Manee area where the NH3, Cd and Hg tests showed values above the permissible or in a polluted state. The sediment characteristic analysis informed that round PIM and Krueng Manee is sandy loam dominated by Avicennia Sp mangroves and Loslaka area is muddy sand dominated by Rhizophora Sp mangrove species.

Systematic changes in circumpolar dust transport to the Subantarctic Pacific Ocean over the last two glacial cycles

The input of the soluble micronutrients iron (Fe) and/or manganese (Mn) by mineral dust stimulates net primary productivity in the Fe/Mn-deficient Southern Ocean. This mechanism is thought to increase carbon export, thus reducing atmospheric CO2 during the Pleistocene glacial cycles. Yet, relatively little is known about changes in the sources and transport pathways of Southern Hemisphere dust over glacial cycles. Here, we use the geochemical fingerprint of the dust fraction in marine sediments and multiisotope mixture modeling to identify changes in dust transport to the South Pacific Subantarctic Zone (SAZ). Our data show that dust from South America dominated the South Pacific SAZ during most of the last 260,000 a with maximum contributions of up to ∼70% in the early part of the glacial cycles. The enhanced dust-Fe fluxes of the latter parts of the glacial cycles show increased contributions from Australia and New Zealand, but South American dust remains the dominant component. The systematic changes in dust provenance correspond with grain size variations, consistent with the circumpolar transport of dust by the westerly winds. Maximum contributions of dust from more proximal sources in Australia and New Zealand (up to ∼63%) paired with a finer dust grain size indicate reduced westerly wind speeds over the South Pacific SAZ during deglacial and peak interglacial intervals. These quantitative dust provenance changes provide source-specific dust-Fe fluxes in the South Pacific SAZ and show how their systematic changes in magnitude and timing influence the Southern Ocean dust-Fe feedback on glacial-interglacial to millennial time scales.

Heavy metal distribution, fractionation, and biotoxicity in sediments around villages in Baiyangdian Lake in North China

The effects of human activities on heavy metal distributions and fractionation in sediments from villages around Baiyangdian Lake (BYDL), North China, were assessed. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in sediments from five villages were determined, and the potential ecological risk index, risk assessment code, and Chironomus sp. larvae toxicity assay were used to assess the bioavailabilities and toxicities of the metals. The contribution of Cd to the potential ecological risk was 45.13-89.53%, the highest among the heavy metals investigated. The contributions of Cd, Pb, and Zn in the non-residual fractions to the total concentrations were 66.23-90.57%, 18.31-96.28%, and 8.89-76.84%, respectively, which indicated that these metals had important anthropogenic sources and were very bioavailable. The mean risk assessment codes decreased in the order of Cd (49.82%) > Zn (20.95%) > Cu (9.35%) > Pb (6.88%) > Ni (4.85%) > Cr (0.30%), and the toxicity of Cd and Zn to biota around BYDL is of concern. The mean survival rate of Chironomus sp. larvae in sediments from Dizhuang village was 44.02%, which indicated that there was a high degree of heavy metal toxicity, particularly in waterways around the village. Carboxylesterase and superoxide dismutase analysis results indicated that heavy metals could markedly increase or decrease enzyme activities in Chironomus sp. larvae. Overall, the results indicated that heavy metal pollution in villages around BYDL should be taken into consideration for its ecological management.

Different pathways of accumulation and elimination of neurotoxicant Hg and its forms in the clam Atlantic rangia (Rangia cuneata)

Mercury (Hg) is one of the most hazardous environmental pollutants, negatively affecting the ecosystem. The pathways of Hg elimination are well recognized in organisms from higher trophic levels compared to invertebrates such as clams. The aim of this study was to identify pathways of Hg accumulation in an alien species clams: Rangia cuneata, which represented an unrecognized source of Hg into the trophic chain of the southern Baltic Sea. An important aspect of this study was to determine Hg detoxification processes based on physiological state and biometric parameters of the atlatntic rangia. Special consideration was given to the role of shell in this process and the form of Hg in which it occurred. The study was also considered in terms of geographical changes in the Hg concentration in clams and the factors involved.Sex did not determine the concentration of Hg and its fraction in clams soft tissue and shell. Clams detoxified xenobiotic effectively in summer when their metabolism was accelerated. As a result, clams grew faster in warmer water than they accumulated Hg. In addition, this process was intensified by their reproduction. The mass of accumulated mercury was higher in the shell mass than in the body mass in summer. Transfer of Hg from the body to the shell depended on the forms Hg, mostly HgS. Geographical changes in the mercury concentration in clams was related to the form of Hg in the sediment. In areas where were more fines sediment fraction and organic matter accumulated in the sediment, mercury was present in a less bioavailable form, which caused that clams had lower Hg concentrations in their body. With assumption that in the future, due to its increasingly frequent occurrence, atlatntic rangia will become more common component of fish diet, a smaller load of toxic mercury will be introduced to the marine trophic chain.

Distribution of organophosphate ester fractions in sediment of the Eastern China Marginal Seas and the influencing factors.

Organic pollutant fractions should be closely investigated because of their different ecological risks. In this study, we examined the distribution of organophosphate ester (OPE) fractions (labile, stable-adsorbed, and tight-adsorbed fractions) in sediments from Eastern China Marginal Seas (ECMSs) and assessed the influencing factor of the fractions. The mean values of total OPEs in ECMSs are 13.70 ± 6.16μg L-1 in seawater and 32.04 ± 14.31μgkg-1 in sediment. The results showed that OPE concentration decreased from the northern to the southern ECMSs, and tris(1-chloro-2-propyl) phosphate and tris(1,3-dichloro-2-propyl) phosphate were the primary OPEs. The mean contents of labile, stable-adsorbed, and tight-adsorbed fractions in the ECMSs were 9.50, 11.29, and 11.71μgkg-1, respectively. Labile OPEs were predominant in offshore waters; the percentage of stable- and tight-adsorbed fractions increased progressively with offshore distance in ECMSs. The specific surface area and surface functional groups of sediment were not consistent with the fraction concentrations from the correlation coefficient, but the gross domestic product per coastline agreed well with the fraction distribution. Based on this, we conclude that human activity, rather than physicochemical characteristics of sediments, may be the primary influencing factor of the relative distribution of different OPE concentration fractions in ECMSs.

The best-modified BCR and Tessier with microwave-assisted methods for leaching of Cu/Zn and their δ 65Cu/δ 66Zn for tracing sources in marine sediment fraction

The optimum condition of modified BCR and Tessier with microwave-assisted (m-a) methods for leaching of Cu and Zn in the sediment Certified Reference Material (CRM) was investigated and then applied to those in marine sediments. Samples were leached by modified BCR and Tessier with (m-a) methods to perform Cu and Zn analysis in each sediment fraction (CRM) by means of ICP-MS. The irradiation power (336 watts) of 50%-2 min (fraction 1), 50%-3 min (fraction 2), 50%-1 min (fraction 3), and 50%-3 min (fraction 4) were observed in the optimum condition of the microwave. The best-modified BCR with (m-a) method was in the range 1.43–10.8% RSD (90.8% recovery) for Cu and 0.40–1.29% RSD (98.6% recovery) for Zn. The optimum condition in the modified Tessier with (m-a) method was also observed in the irradiation power (336 watts) of 50%-1 min (fraction 1), 30%-3 min (fraction 2), 30%-3 min (fraction 3), 50%-1 min (fraction 4), 30%-2 min (fraction 5). The best range precision (accuracy) in the optimized condition with (m-a) was recorded as leaching Cu in the range of 0.62–1.65% RSD (98.8% recovery) and Zn in the range of 1.35–6.06% RSD (92.7% recovery). Both of the best-modified methods were then applied to marine sediment of the Java Sea and measured their Cu and Zn isotopes fractionations by the recommended MC-ICP-MS. Considering treated Cu and Zn isotope fractionations by δ 65 Cu calculated in the range 3–4.5‰ reflecting the source of their Cu and Zn from natural sediments. • Cu and Zn concentrations and their isotopes were analyzed in the marine sediment. • Modified BCR and Tessier of leached Cu and Zn were applied using the microwave. • Both the best-modified BCR and Tessier were found in the optimum condition of CRM. • Those methods successfully leach Cu and Zn in the marine sediment of the Java Sea.

Characteristic regional differences in trace element pattern of 2014 German North Sea surface Wadden sediments - A judge and assessment.

The European Marine Strategy Framework Directive (MSFD) requires good ecological status of the marine environment. This also includes the Wadden Sea located in the southeastern part of the North Sea and its chemical status of sediments. Based on results from campaigns conducted in the 1980s, 32 surface sediment samples were taken in 2014 to check whether the sampling strategy required for characterizing the trace element content in sediments is representative and to determine the degree of pollution and potential changes over the last decades. For this purpose the elemental mass fractions of 42 elements were assessed in the ≤20μm grain size fraction of the surface sediments. Based on cluster analysis a clear correlation between the element distribution and the geographical location of the sampling locations of the German Wadden Sea could be found. As a result of the principal component analysis, three sub-catchments were significantly separated from each other by the characteristic element distributions in the sediments (Norderney and Weser, Elbe and offshore areas, and North Friesland). With the help of discriminant analysis, the classification was confirmed unambiguously. Small anomalies, such as potentially contaminated sites from WWII, could be identified. This proved that the sampling strategy for sediment characterization with reference to trace elements in the Wadden Sea of the German Bight is representative. The impact of regulation and changes on the overall sediment quality is most evident when looking at the environmentally critical elements such as As, Cd, Hg, and Cr. For these elements the mean mass fractions show a significant reduction over the last three decades. Current sediments feature only slightly elevated mass fractions of Ag, Cd, Ce, Cs, Nd, Pb and Se at some sampling locations.

Mobile trace elements in sediments from lakes Hawassa, Koka, and Ziway in the Ethiopian Rift Valley.

The present work focuses on total concentrations of trace elements such as chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb) and their operationally defined speciation in surface sediments from three Ethiopian Rift Valley Lakes (Hawassa, Koka, and Ziway). Total concentrations were determined using inductively coupled plasma-mass spectrometer (ICP-MS). A six-step sequential extraction was also applied to evaluate the mobilization potential of these elements. Compared with the consensus-based sediment quality guidelines (SQGs) developed for freshwater ecosystems, the total Zn concentration in sediments from Lakes Hawassa and Ziway, as well as Cr, Ni, and Zn in sediments from Lake Koka, was higher than the probable effect concentration (PEC), suggesting that these elements could have a negative effect on benthic organisms. The sequential extraction results showed that Cd, Mn, and Se were to a certain extent associated with the reversible fractions (F1-F3) in sediments, and thereby more mobile than the other investigated trace elements. Predictions of mobility of trace elements using the distribution coefficients (Kd) values were also in agreement with the sequential extraction results. Furthermore, multivariate statistical analyses showed that redox-sensitive fractions (F4 and F6) and the residual fraction (F7) were the dominant factors controlling most trace element mobility. Finally, applying the Risk Assessment Code (RAC) classification system, results showed that Mn in Lake Koka could pose a high risk, while Cd and Mn in Lake Hawassa as well as Cd, Mn, and Se in Lake Ziway sediments could pose medium risk to benthic organisms.

Sediment transport and morphological responses of a silty coast to a cold front event in the southwest Bohai Bay of China

Silty coast, as a transitional state between muddy coast and sandy coast, possesses a considerable percentage of the overall coast in China. Huanghua-Binzhou coast in the southwest Bohai Bay in the northeastern China is a typical silty coast which is vulnerable to cold fronts when its seabed is prone to suffer suddenly drastic erosion and deposition due to the sediment there with relatively low incipient velocity and high settling velocity. In this study, a multi-sediment fraction model was established and two-way coupled with the wave-tide-surge model to investigate the responses of the sediment transport and morphodynamics of Huanghua-Binzhou coast to a cold front event during 10–13th Oct. 2003. The model results demonstrate that three sediment fractions, i.e. mud, silt and sand, showed different responses to the storm due to their different spatial percentages and distinct physical properties. The silt fraction, as the primary fraction, played a leading role in the suspension and transport of the total sediment, and showed a pattern of “deposition-erosion-deposition” in the cross-shore direction like the total morphological change. The fine sediment was transported westward and offshore during the storm, which indicated the sediment coarsening in the study area. The depth-induced wave modulation considerably enhanced the resuspension ability of the nearshore waves for sediment and thus played a critical role in intensifying the erosion. The Huanghua waterway siltation mainly resulted from the resuspension of the offshore sediment by the strong wind waves and its westward transport by the wind-induced currents during the storm. The construction of two long jetties in 2006 can significantly reduce the deposition in the waterway by 75%, and the additional large-scale construction in 2016 can further lessen the waterway siltation by intercepting the westward sediment transport and reduce the suspended sediment concentration by 30% by the land reclamation in the study area.

Influence of mangrove forestation on heavy metals accumulation and speciation in sediments and phytoremediation capacity of mangrove species of an artificial managed coastal Lagoon at Xiamen in China

ABSTRACT This study investigates the heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb) accumulation and speciation in the mangrove and lagoon sediments in the Yundang Lagoon. This also investigates the phytoremediation capacity of the mangrove species in the forestation areas. The result showed that significantly (P < 0.05) higher amount of organic carbon in the mangrove forestation sediments than lagoon sediments. Mangrove forestation increased the accumulation of Cr, Mn, Cu, As, and Zn in the mangrove sediments than lagoon sediments. According to chemical speciation, it revealed that acid-soluble fraction decreased and oxidisable fraction increased in the mangrove sediments than lagoon sediments. Cu, Ni, Cr, and As has considerably increased in oxidisable fraction, and Cd and Pb have increased in the reducible fraction in the mangrove sediment. The bio-concentration factor and translocation factor values indicate that these species of mangroves are not efficient accumulators of heavy metals from the surrounding environment but potential metals translocators. These results suggest that mangrove forestation can increase the circulation of heavy metals resulting in stabilise the polluted environment. Moreover, this study suggests that mangrove forestation has enhanced metals accumulation but decreased their bioavailability and mobility in the sediment.

Cadmium chemical fractions in sediments: effect of grain size, pH, organic acids, and inorganic ions

Cadmium chemical fractions in sediments: effect of grain size, pH, organic acids, and inorganic ions

Research on the Relationship between Sediment Concentration and Centrifugal Pump Performance Parameters Based on CFD Mixture Model

To study the relationship between sediment concentration and the performance parameters of centrifugal pumps, Jiamakou water supply pumping station with total installed capacity of 30,880 kW was selected to analyze characteristics of the centrifugal pump in this paper. Based on a CFD mixture model, the effects of different sediment concentrations on the movement of solid–liquid two-phase flow and the performance parameters of the centrifugal pump were obtained. Then, fitting equations were established between performance parameters (head, flow rate, shaft power, and efficiency) of the centrifugal pump and sediment concentration at three working conditions (0.8 Q = 2 m3/s, Q = 2.5 m3/s, 1.2 Q = 3 m3/s) by the polynomial least-square method. Calculated values of fitting equations were compared with the measured values in centrifugal pump operation. The results show that, as the sediment concentration increases from 0.1% to 1%, the maximum volume fraction of sediment at blade outlet increased from 0.14% to 1.14%, and the maximum volume fraction of sediment at blade outlet increased from 0.7% to 2.29%. The turbulent kinetic energy inside the centrifugal pump increased from 8.74 m2/s2 to 10.78 m2/s2. The calculated values of fitting equation are in good agreement with the measured values in centrifugal pump operation, and the maximum errors of head, flow rate, and efficiency are 6.48%, 3.54%, and 2.87%, respectively. Therefore, the reliability of the fitting equations is verified. The research method can provide a reference for the calculation of performance parameters for centrifugal pumps in other water supply pumping stations with sediment-laden flow.

The impact of river sand mining on remobilization of lead and cadmium in sediments – A case study of the Jialing River

Due to the fast pace of urbanization worldwide, industrial sand mining activities have imposed great pressure on the environment, and consequently, these activities have led to serious environmental problems in aquatic ecosystems. However, the current understanding of the effect of sand mining on heavy metal remobilization in river sediments remains incomplete. The present study employed sediment quality guidelines (SQGs) and the sequential extraction (SE) and diffusive gradients in thin films (DGT) techniques to comprehensively investigate the effect of sand mining on the remobilization process of heavy metals in the aquatic system of the Jialing River. The SQGs results indicated that stations (S1 to S4) with sand mining disturbance exhibited Pb and Cd accumulation in surface sediments. Both Ctotal-Pb (61.78–122.04 mg·kg−1) and Ctotal-Cd (0.85–3.96 mg·kg−1) were higher than CSQGI (60 mg·kg−1 for Pb and 0.5 mg·kg−1 for Cd) and TEC (35.8 mg·kg−1 for Pb and 0.99 mg·kg−1 for Cd) limitation in most of sand mining stations. Pb and Cd were mainly bounded in the acid-soluble/exchangeable fraction (F1) and oxidizable fraction (F3) of the surface sediments. At the four stations with sand mining disturbance, about 5–10 folds of DGT-labile Pb and Cd were released in deep sediments (−9 to −12 cm), and Pb and Cd exhibited a transport trend from the sediments into the overlying water, while the above phenomenon was not observed at the two stations without sand mining activities. Correlation analysis revealed that DGT-labile Pb and Cd were suitably correlated with the F1 and F3 fractions, indicating that the acid-soluble/exchangeable and oxidizable fractions were the main sources leading to Pb and Cd remobilization in the sediments. A potential mechanism explanation may be that (1) intense sediment stirring could result in remobilization of the weakly bound fraction, which is related to the contribution of the F1 fraction, and (2) Cd/Pb experienced a corelease process with sulfur due to O2 introduction (elevation of the dissolved oxygen level) attributed to sediment evacuation, which is related to the contribution of the F3 fraction. The above results suggested that sand mining in the Jialing River should be paid high attention to prevent heavy metal pollution in aquatic ecosystem.

An in situ study of abyssal turbidity-current sediment plumes generated by a deep seabed polymetallic nodule mining preprototype collector vehicle

An in situ study to investigate the dynamics of sediment plumes near the release from a deep seabed polymetallic nodule mining preprototype collector vehicle was conducted in the Clarion Clipperton Zone in the Pacific Ocean 4500-m deep. The experiments reveal that the excess density of the released sediment-laden water leads to a low-lying, laterally spreading turbidity current. At the time of measurement, 2 to 8% of the sediment mass were detected 2 m or higher above the seabed and were not observed to settle over several hours, with the remaining 92 to 98% below 2 m and some fraction of that locally deposited. Our results suggest that turbidity current dynamics sets the fraction of sediment remaining suspended and the scale of the subsequent ambient sediment plume. The implications of this process, which is characteristically overlooked in previous modeling efforts, are substantial for plume modeling that will lie at the heart of environmental impact statements for regulatory consideration.

Origin of organic matter and depositional characteristics of early Cambrian Niutitang Formation from South China: New insights using molecular fossils

The early Cambrian Niutitang Formation is broadly developed in South China, especially in the Yangtze region. This research explains the nature of hydrocarbons through bitumen fractions of the early Cambrian sediments of the Niutitang Formation. For this purpose, source rock samples from two diverse outcrop sections are utilized for total organic carbon content (TOC), solvent extraction, and gas chromatography–mass spectrometry (GC–MS). Results show a lower quantity of extractable organic matter in these older sediments because of higher maturation history. The presence of monomethyl alkanes suggests the contribution of prokaryotic organisms, whereas the presence of hopanoids and C27–C29 steranes shows the occurrence of eukaryotic algal sources in organic matter. Likewise, C30‐4‐methyl sterane, dinosteranes, and ß‐carotene also suggested incorporating prokaryotic and eukaryotic sources during the early Cambrian period. Various hopanoid parameters, alkylated aromatic isomers, triaromatic steroids, and vitrinite reflectance via methyl‐phenanthrene index reveal mature to higher thermal evolution levels of these lower Palaeozoic sediments. Similarly, a higher abundance of polyaromatic pyrene and fluoranthene indicates mature organic matter, and their presence could be due to hydrothermal action. The higher gammacerane index, lower pristine/phytane, and the presence of C30 dimethyl steranes indicate the anoxic saline sedimentary condition throughout the deposition of these lower Palaeozoic Niutitang Formation. The early Cambrian Niutitang Formation is deposited in an oxygen‐deficient environment and contains an adequate amount of mature‐high mature organic matter that could have the potential to produce gaseous hydrocarbons.

Sedimentary Response to Climate Change in the Central Bay of Bengal since the Last Glacial Maximum

Abstract As the largest submarine fan, the Bay of Bengal (BoB) captures the abundant environment and climate fingerprints on different time scales. To investigate the sedimentary response to climate change since the Last Glacial Maximum (LGM), an integrated survey was performed to study grain size, major, and trace elements (Al2O3, CaO, K2O, Na2O, TiO2, Sr, and Rb) of core BoB-24 sediments from the central BoB. The (K/Al)-TiO2 (%) relationship of the sediments was taken for the discrimination of provenance, which indicated that sediments from core BoB-24 in 24~6.5 cal ka BP were primarily from terrigenous material input from the Himalayas. In contrast, the material contribution from the Indian subcontinent increased distinctly since 6.5 cal ka BP. The rising sea level severed direct material supply, thus causing the evolution of sediment provenance of the central BoB. Meanwhile, the strengthened Indian summer monsoon (ISM) in the Holocene affected detrital material transport from offshore to the central BoB. After understanding the sediment provenance in the study, we choose the sensitive grain-size fraction to show the evolution of hydrodynamic conditions. The chemical index of alteration (CIA) and Ti/Ca and Rb/Sr ratios are calculated to indicate the change in terrigenous input and weathering intensity. The contents of sediment fraction from 11.05 to 15.63 μm, CIA, and ratios of Ti/Ca and Rb/Sr in core BoB-24 showed the same trends, which were low during the last deglaciation and late Holocene but high in the Early Holocene. The trends were strongly correlated with the variation of the Indian summer monsoon, indicating the possible impact of Indian monsoon on sediment transport in the Bay of Bengal. Alternative indicators such as the contents of ratios of Ti/Ca and Rb/Sr, CIA, and sensitive grain-size content in sediments of core BoB-24 jointly record the evolution history of ISM since 24 ka BP in the Bay of Bengal. Although the sensitivity and response of each indicator to the paleoenvironment and paleoclimate change are slightly different, on the whole, the change trend is the same. Specifically, four warm-cold alternating periods (Heinrich Event 1, Bølling/Allerød, Younger Dryas, and Early Holocene Climatic Optimum) had a strong signal in these proxies that indicated that the millennial-scale climate controls the terrigenous input to the Bay of Bengal, where a high value occurs in warm events and low value in cold events. The sedimentary pattern of the northeastern Indian Ocean provides scientific evidence for an insight into the regional response to global climate change and the long-term climate change trend of the human environment across the monsoon region.

Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

Abstract. Substantial uncertainties in bedload transport predictions in steep streams have encouraged intensive efforts towards the development of surrogate monitoring technologies. One such system, the Swiss plate geophone (SPG), has been deployed and calibrated in numerous steep channels, mainly in the Alps. Calibration relationships linking the signal recorded by the SPG system to the intensity and characteristics of transported bedload can vary substantially between different monitoring stations, likely due to site-specific factors such as flow velocity and bed roughness. Furthermore, recent flume experiments on the SPG system have shown that site-specific calibration relationships can be biased by elastic waves resulting from impacts occurring outside the plate boundaries. Motivated by these findings, we present a hybrid calibration procedure derived from flume experiments and an extensive dataset of 308 direct field measurements at four different SPG monitoring stations. Our main goal is to investigate the feasibility of a general, site-independent calibration procedure for inferring fractional bedload transport from the SPG signal. First, we use flume experiments to show that sediment size classes can be distinguished more accurately using a combination of vibrational frequency and amplitude information than by using amplitude information alone. Second, we apply this amplitude–frequency method to field measurements to derive general calibration coefficients for 10 different grain-size fractions. The amplitude–frequency method results in more homogeneous signal responses across all sites and significantly improves the accuracy of fractional sediment flux and grain-size estimates. We attribute the remaining site-to-site discrepancies to large differences in flow velocity and discuss further factors that may influence the accuracy of these bedload estimates.