Sediment Data Research Articles

Analysis of the evolution trends and influential factors of bankfull discharge in the Lower Yellow River

After the Xiaolangdi Reservoir (XLDR) was put into operation, new water and sediment conditions have improved the silting condition of the Lower Yellow River (LYR), but against this background, the flow capacity of the LYR has become more complex. In this research, the measured water and sediment data of seven hydrological stations in the LYR from 1950 to 2020 were systematically collated. The evolution trend and development period of the bankfull discharge in this area were studied based on the wavelet analysis method, and the main factors influencing the evolution of the bankfull discharge were explored. The results indicate that the evolution process of bankfull discharge in the LYR has experienced two phases in the last 70 years. XLDR has been impounded since October 1999. Before XLDR operation, the bankfull discharge of the LYR has a main time scale of about 26 years. After XLDR operation began, it has a time scale of about 10 years. The bankfull discharge of the LYR shows two phases of evolution, and these phases are mainly influenced by the factors of water and sediment conditions. This research is needed for a deeper understanding of flow-bed and river discharge and sediment transport capacity under the water and sediment conditions in the LYR.

Tracing mantle components and the effect of subduction processes beneath the northern Antarctic Peninsula

Understanding subduction processes is critical in assessing the long-term evolution of the upper mantle and continental crust. We present new geochemical data on glassy submarine lavas from the Bransfield Strait, the Phoenix and West Scotia ridges, and previously unpublished data of marine sediments from atop the Phoenix Plate. We combined new and published geochemical data from across the northern sector of the Antarctic Peninsula to unravel both large-scale mantle composition and flow across the region. The geochemistry of Phoenix and West Scotia Ridge basalts supports the hypothesis that both ridges are underlain by Pacific MORB mantle, brought into the region through the eastward expansion of the Scotia Plate. Comparisons among lavas from the Phoenix/West Scotia ridges, the South Shetland Islands volcanic arc, and the Bransfield Strait/Prince Gustav Rift back-arc region reveal that the Pacific upper mantle flowed into the mantle wedge and was subsequently modified by subduction processes. The compositions of Bransfield Strait lavas range from strongly subduction-influenced near the strait’s center to akin to Phoenix Ridge MORB toward the strait’s edges. This suggests that the Phoenix MORB mantle has flowed around the slab edges into the mantle wedge, diluting the subduction signal and focusing the subduction-modified mantle towards the center of the strait. Monte Carlo simulations indicate that mixing of Phoenix MORB mantle with 0 to 3 % subduction component having a fluid/sediment ratio of ∼1 can explain the compositional range in the Bransfield Strait. Furthermore, our modeling suggests the presence of a more depleted Phoenix MORB mantle beneath the South Shetland Islands modified by the addition of ∼3 % subduction component with a fluid/sediment ratio ranging from ∼0.18 to 4. The increase in fluid/sediment ratios in the South Shetland Island lavas corresponds to a spatiotemporal progression of volcanism from the southwest (40–140 Ma) to the northeast (30–60 Ma). Finally, we have identified a set of lavas with unique trace element and isotope compositions typical of alkaline volcanism found across other parts of the Antarctic Peninsula. Surprisingly, we find occurrences of these lavas on both sides of the South Shetland Trench, suggesting the presence of a distinct enriched source in the upper mantle throughout the region.

Mesophotic bioclastics and bioconstructions at the continental shelf of Santos Basin, Brazil

The Santos Basin mesophotic zone comprises one area of 104,915 km2, occupying 78% of the entire basin. Santos Basin is one of the most under stress and sensitive marine regions in the Brazilian territory due to several major ports, Oil & Gas industry, and coastal marine environmental management areas. Scientific literature recognizes that rhodolith beds and biogenic rigid-bottom patches occur on the shelf, but because lack of high-resolution seismic data, these seabed features are not yet wholly mapped at Santos Basin. However, an unprecedented gathering of historical depth sounding points and surface sediment data collection, in conjunction with an extensive field campaign of seabed sampling and sub-bottom shallow seismic records, points out new evidence of biogenic sediment distribution reefal structures in the Santos Basin. The patches of calcareous algae crusts, terraces mounds, pinnacles, and free-living rhodolith beds compose the carbonate facies on the outer shelf. Rugged bottom relief and pinnacles up to 10 m in height correlate with carbonate gravels and sandy areas. Bioconstructions are more common northward and gradually decrease southward. Geomorphological features such as rugged bottom relief might indicate the occurrence of mesophotic bioconstructions off Paraná, and Santa Catarina State coast. The mesophotic bioconstructions have evolved through four stages: 1- LGM fully sposed shelf, 2- sea-level transgression and bioconstrutions pioneers, 3- influence of the La Plata plume at the southern sector, and 4- establishment of mud patches in the northern sector due to local input.

Identifying potential porphyry copper mineralization at the Zhu’nuo ore-cluster district in western Gangdese, southern Tibet: Insights from shortwave infrared (SWIR) spectrometry and geochemical anomalies

The Zhu’nuo ore-cluster district in the western Gangdese belt, southern Tibet, is characterized by a significant Cu geochemical anomaly, where the Zhu’nuo super-large porphyry Cu deposit (PCD) was discovered by stream sediment geochemical method. However, due to the extended coverage of volcanic rocks of the Linzizong group and the large area of ore-forming element anomalies, it is quite difficult to locate the concealed PCDs only by geochemical method. Therefore, the application of new technical methods is urgently needed to guide the exploration breakthroughs in the Zhu’nuo district. Recently, our studies have shown that the wavelength variation of diagnostic absorption peaks of alteration minerals measured by shortwave infrared (SWIR) spectrometry is closely related to the mineralization temperature in the Zhu’nuo PCD, which can be footprints to trace the hydrothermal and/or mineralization (H/M) centers of porphyry ore systems. Hence, we carried out SWIR studies in the Luobuzhen-Cimabanshuo areas with high Cu geochemical anomaly. In this study, sixteen alteration minerals were identified by SWIR, consisting mainly of white mica, chlorite, epidote, and kaolinite. Among them, the white mica and chlorite were widely distributed in the study area, and the Al-OH wavelength position of white mica (∼2200 nm; Pos2200) and Fe-OH wavelength position of chlorite (∼2250 nm; Pos2250) varied between 2191–2219 nm and 2239–2260 nm, respectively. Moreover, there is an increasing trend of Pos2200 from porphyry center to periphery, whereas Pos2250 shows the opposite tendency. When combined with geochemical anomalies of stream sediments and geological characteristics and SWIR features in the Zhu’nuo PCD in study area, three potential H/M centers, namely Cimabanshuo, South Luobuzhen and Ya’nuri, were determined, which are dominated by short wave anomalies (Pos2200, 2191–2206 nm; Pos2350, 2243–2250 nm). Significantly, we showed that the Dongshibu-Hongshan-Luobuzhen may belong to the same porphyry system by SWIR. And SWIR implies that the true center is located in South Luobuzhen (H/M II), which has great prospecting potential in its depth, rather than the previously recognized Dongshibu Cu prospect delineated by stream sediment data. We found that the Dongshibu Cu prospect does not show any alteration information associated with porphyry mineralization as reflected by SWIR, consistent with the barren Cu results from the late drilling validation. This decoupling may be caused by the long-term migration and weathering of stream sediment samples, during which the obtained geochemical anomaly do not represent their in-situ information. Therefore, caution must be taken when using stream sediment data to delineate prospecting targets. Instead, SWIR is a potentially powerful vectoring tool to aid exploration for porphyry systems, especially in the western regions where the level of prospecting work is extremely low.

Evaluating color parameters calculated from digital photographs of sediment cores as a tool in paleoenvironmental reconstruction—A case study using IODP Site U1502 from the South China Sea

Qualitative color data of sediments contain rich information on sediment compositions and have been widely used in paleoenvironmental reconstructions. Digital photographs can produce ultra-high resolution color data of sediment sequences. The characteristics of such data, however, are not yet explored adequately, hindering their use in practice. To fill this gap, in this study we calculated color data from digital photographs of sediment cores from Hole U1502A drilled during International Ocean Discovery Program Expedition 368 in the South China Sea, and compared them with their counterparts measured using a Diffuse Reflectance Spectrophotometer (DRS). We found that the luminance parameter L could be influenced by multiple factors, leading to its behavior being transient, while the chromaticity parameters a* and b* are relatively stable. The down-core patterns of photograph-derived L, a* and b* are comparable with their counterparts derived from DRS measurement, although their absolute values can diverge significantly from those DRS-measured ones. The color of the studied core sediments alternates between grayish-brown and greenish-gray, being pelagic deposits and earthquake-induced turbidite deposits, respectively. Such color cycles had been present since ~13 Ma, revealing a dramatic increase in submarine earthquakes due to subduction of the SCS Plate toward the Philippine Plate. Overall, our study demonstrates that color parameters calculated from sediment photographs could be developed as promising tools for studies relating to paleoenvironmental reconstructions.

Authigenic Formation of Clay Minerals in the Abyssal North Pacific

AbstractPresent estimates of the biogeochemical cycles of calcium, strontium, and potassium in the ocean reveal large imbalances between known input and output fluxes. Using pore fluid, incubation, and solid sediment data from North Pacific multi‐corer cores we show that, contrary to the common paradigm, the top centimeters of abyssal sediments can be an active site of authigenic precipitation of clay minerals. In this region, clay authigenesis is the dominant sink for potassium and strontium and consumes nearly all calcium released from benthic dissolution of calcium carbonates. These observations support the idea that clay authigenesis occurring over broad regions of the world ocean may be a major buffer for ocean chemistry on the time scale of the ocean overturning circulation, and key to the long‐term stability of Earth's climate.

Comparative Study on Three Autoencoder‐Based Deep Learning Algorithms for Geochemical Anomaly Identification

AbstractDeep autoencoder (AE) networks show a powerful ability for geochemical anomaly identification. Because of little contribution to the AE network, small probability samples (again, please check this) having comparatively high reconstructed errors can be recognized by the trained model as anomalous samples. However, different autoencoder networks have different abilities for anomaly identification. To test these methods for geochemical anomaly identification, we based our study on stream sediment data of the Cu‐Zn‐Ag metallogenic area in southwest Fujian province as samples. Three unsupervised deep learning models: the autoencoder (AE), multi‐convolutional autoencoder (MCAE), and fusion convolutional autoencoder (FCAE), were used to extract the combined structural, spatial distribution, and mixed features of multiple‐elements. The results showed that the anomalous area delineated by the FCAE model had the best consistency with the known copper mineral occurrences, followed by the MCAE and AE models, with area under the curve values (AUC) of 0.80, 0.78, and 0.61, respectively. FCAE and AE were insensitive to changes in convolution window size, while MCAE extracted more spatial distribution or mixed features. Overall, FCAE focused more on structural distribution or mixed features, combining the advantages of both MCAE and AE. Therefore, FCAE performed best among the three deep learning methods. This study provides a practical basis for selecting and constructing geochemical anomaly recognition models based on deep learning algorithms.

Mixing and partially non-conservative behavior of molybdenum, uranium and vanadium along the salinity gradients of the Amazon and Pará estuaries and associated plume

The Amazon and the Pará are two major rivers that carry dissolved and suspended particulate trace metals to the Atlantic Ocean. In the dynamic mixing zone of the estuary, competing processes of trace metal sorption and release play a role, which might affect transport to the open ocean. Here we investigate the behavior of dissolved (<0.2 μm), soluble (<0.015 μm) and truly dissolved (<10 kDa and < 1 kDa) molybdenum (Mo), uranium (U), and vanadium (V) during estuarine mixing between river water (S < 1) and seawater (S > 35) end members during the high discharge period, as well as during aging of the plume in its northward flow along the coast. Molybdenum behaved conservatively during estuarine mixing and showed no colloidal fraction, suggesting Mo is solely present in the soluble or even truly dissolved fraction. Uranium behaved mostly conservatively but showed removal in the low salinity range (ca. S < 9). This is potentially due to colloidal flocculation at low salinities, as indicated by colloidal (0.015–0.2 μm) fractions of up to 30% for U but decreasing with increasing salinity until no significant difference could be discerned at S > 10. Vanadium shows a general conservative mixing, but with more scatter in the data than for Mo and U and potential removal at low to mid-salinities. Removal of V to the sediments is also indicated by surface sediment data from the mid-salinity region of the estuary but no size fractionation in the dissolved phase could be observed. Hence, V seems to be predominantly present in the soluble or even truly dissolved phase and export to the sediments might take place through particles >0.2 μm. No considerable removal or release of Mo, U and V was observed in their water column depth profiles, indicating a conservative behavior in the water column of the estuaries studied here. Additionally, we present a comparison of differential pulse adsorptive stripping voltammetry and inductively coupled plasma – mass spectrometry analyses for Mo and V, which showed excellent agreement within analytical uncertainty in this challenging sample material covering the full salinity range from freshwater to seawater.

Investigation the grain size effect on multi-element concentration using statistical analysis of INAA and laser-diffraction data for estuarine sediments of Hau River, Vietnam

Investigation the grain size effect on multi-element concentration using statistical analysis of INAA and laser-diffraction data for estuarine sediments of Hau River, Vietnam

Morphological Evolution Characteristics of River Cross-Sections in the Lower Weihe River and Their Response to Streamflow and Sediment Changes

River cross-section morphology and water and sediment conditions are deeply connected. In recent years, the lower Wei River has experienced regular flooding and drastic changes in river channel shape, causing significant harm to the economy and development of the lower reaches. This research investigated the morphological evolution features based on annual extensive cross-section data and water and sediment data from the hydrological stations of Xianyang, Lintong, and Huaxian in the lower Weihe River from 2006 to 2018 of river cross-sections and the reaction to water and sediment variations. The findings indicated that the lower Wei River’s cross-sectional alterations between 2006 and 2018 exhibited a trend of “flushing at both ends and siltation in the middle” while continuing to exhibit “non-flood flushing and flood siltation” features. The incoming sediment coefficient in the lower Weihe River declined dramatically, whereas the median diameter of suspended sediment particles grew significantly at the Lintong station. The average elevation of the river channel was highly synchronized with the change in the coming sediment coefficient, and the impact of big floods dramatically influenced the shape of the river cross-section. Human activities such as river management have directly affected the morphology of the river cross-section at Lintong station and caused a significant increase in the median diameter of suspended sediment particles, resulting in siltation in the Lintong river. The study’s findings can serve as a theoretical foundation for water and sediment regulation and river training in the lower Weihe River, reducing flooding damage.

A Gap-Filling Tool: Predicting Daily Sediment Loads Based on Sparse Measurements

Sediment load in streams is known as both a carrier and a potential source of contaminants, while sediment deposition can alter stream flow, stage and morphology, and thereby has broad impacts on stream hydrology, aquatic life, and recreation activity. For vast amounts of watersheds around the world, sparse daily measured sediment data may exist, but continuous and multi-year daily measured sediment data are largely unavailable because of time-consuming and budget constraint for measurements. However, when developing total maximum daily load (TMDL) and calibrating/validating watershed models for sediments, such continuous and multi-year datasets are inevitably required. This study extended the flow-weighted method, developed by Ouyang (Ouyang, Y. Environ. Monit. Assess. 193, 422 (2021)) to predict the continuous and multi-year daily sediment loads based on sparse, limited, and discontinuous measured data. This daily sediment load gap-filling tool was validated using measured data from six different US Geological Survey (USGS) gage stations across US. Results showed that the flow-weighted method well predicted daily sediment loads when a good linear correlation existed between measured seasonal sediment loads and measured seasonal stream discharges, which is a prerequisite to apply the flow-weighted method. Five out of six selected USGS gage stations used in this study met this prerequisite. The flow-weighted method (along with an example R script for implementing the method) is a useful tool for filling the daily sediment load gaps.

Sources of polychlorinated biphenyls to Upper Hudson River fish post-dredging

Polychlorinated biphenyls (PCBs) are persistent, bioaccumulative, and toxic chemicals that are the dominant contaminant in the Upper Hudson River (UHR) in New York State where two General Electric (GE) plants historically discharged PCBs to the river. Portions of the UHR were dredged from 2009 to 2015 to address PCB contamination. In 2017, the first post-dredging survey of yearling feeder fish and sediment PCB contamination was conducted to establish a baseline for the recovery of the river. Prior analysis of the sediment data from the 2017 survey indicated that ∼2% of the PCBs in the surface sediment were higher in molecular weight than the formulation used by GE and therefore arose from non-GE sources. In this work, the fish PCB data from the 2017 survey were analyzed using Positive Matrix Factorization (PMF). Empirical Bayesian Kriging (EBK) was used to estimate PCB concentrations in the sediment at the locations where fish were collected. The results suggest that PCBs that are the products of microbial dechlorination bioaccumulate in the fish and represent 7% of the PCB mass in the fish data set. Further, the results suggest that about 13% of the PCBs in the fish may have come from non-GE sources. This is higher than the percentage of non-GE PCBs in the sediment, but can be explained by the higher molecular weight of the non-GE mixture which causes it to bioaccumulate more effectively than GE PCBs. Concentrations of the non-GE PCBs averaged about 240 ppb wet weight (whole body) in yearling feeder fish. The remedial goals range from 50 to 400 ppb ww in fillet for fish including piscivorous species that are likely to have higher PCB concentrations than feeder fish.

New archaeomagnetic directions from Late Neolithic sites in Shandong province, China

SUMMARY Archaeomagnetism provides important constraints to help us understand the past behaviour of the geomagnetic field. For archaeologists, archaeomagnetic dating has become a potential supplement to traditional dating methods (e.g. radiocarbon dating). Although China has a long history with numerous archaeological discoveries, the collection of archaeomagnetic data remains scarce. In this paper, we provide new archaeomagnetic directions from four late Neolithic (c. 2000 BC) sites in Shandong province, China. After a careful characterization of magnetic mineralogy and a detailed alternating-field demagnetization of the oriented samples, a total of nine archaeomagnetic directions (each with both declinations and inclinations) were obtained, which fill the large gap at c. 2000 BC in the Chinese palaeomagnetic secular variation (PSV) curve. Combining these new results with previously published data, we updated the Chinese PSV curve for the last 7 kyr. We have compared the updated curve with several global geomagnetic models (e.g. pfm9k.1a, ARCH10k.1, CALS10k.1b). Comparisons show that the CALS10k.1b model does not yield a reasonable fit of the data, and the fit becomes worse for older intervals. This poor fit could be explained by the fact that the CALS10k.1b model consists of a large amount of sedimentary data. Therefore, the PSV pattern is difficult to determine due to the strong aliasing effect. On the contrary, the ARCH10k.1 model gives a much better fit than other models because its data are mostly from archaeological materials and the data are mainly from the Northern Hemisphere. The field intensity and PSV are potentially correlated, with a weak field corresponding to an enhanced PSV. However, due to the lack of data for certain time intervals, the proposed correlations need to be further tested. To explore if PSV exhibits longitudinal symmetric or latitudinal antisymmetric patterns like those of the geocentric-axial-dipole (GAD) model, we compiled and compared data from three East Asia countries (China, Korea and Japan) and from four areas (East Asia, North America, Europe and the Middle East, and Australia and New Zealand) of which the latitudes are between 30° and 40°. In the East Asia region, the PSV patterns shown in each data set are consistent because of the geographic proximity of these three countries. However, when comparing the PSV curves from the four global areas, we suggest a potential declinational minimum between 0 AD and 2000 AD. Although further confirmation and investigation are needed, this declination minimum could be diachronous, sweeping from East Asia to Australia and New Zealand, and then North America. Future studies should focus on adding more reliable and precisely dated data to better delineate the PSV trends. Archaeomagnetic dating is promising when a PSV curve can be continuously reconstructed.

Paleoenvironmental changes during the early Toarcian Oceanic Anoxic Event: Insights into organic carbon distribution and controlling mechanisms in the eastern Tethys

• Unlike N Europe, TOC contents are significantly varied in lower Toarcian sediments of the eastern Tethys . • Anoxic, but non-sulfidic conditions prevailing during the T-OAE. • Humid climates promoted moderate continental weathering during the T-OAE. • Marine productivity was commonly high during the T-OAE in the eastern Tethyssouthern Qiangtang Basin. • Organic carbon burial and oil shale accumulation sustained by increased primary productivity. The Toarcian Oceanic Anoxic Event (T-OAE; Early Jurassic, ca. 183 Ma) represents an intense Mesozoic organic carbon burial event that was associated with the formation of oxygen-deficient conditions at paleo-shelf seas, as well as in lacustrine settings. Global scale increase in organic carbon accumulation occurred in connection with profound changes in climate conditions and perturbations of biogeochemical cycles. This study presents geochemical data for lower Toarcian and Bajocian-Bathonian sediments exposed in the Bilong Co section, located in the southern Qiangtang Basin of central Tibet. During Early and Middle Jurassic times, the study site was located in the north-eastern marine of the Tethys Ocean. A total of 83 rock samples, spanning the Quse (lower Toarcian) and Sewa formations (upper Bajocian-Bathonian), were analyzed for their total organic carbon (TOC) content, carbon isotopes of bulk carbonate and kerogen, as well as major and trace elements. Data allowed to assess changes in the environmental conditions in the eastern Tethys Ocean and further allowed to reconstruct changes in paleo-weathering conditions, marine primary productivity, and redox regimes that occurred in association with the T-OAE. In addition, factors that controlled the accumulation of organic material in the sediment are discussed. Enrichment factors (EF) of redox-sensitive trace elements, their relationship with TOC, and C org /P total molar ratio attest to predominantly anoxic pore and bottom waters in southern Qiangtang Basin during the T-OAE. On the contrary, oxic conditions prevailed during pre- and post-T-OAE times. During the T-OAE, the development of anoxic conditions were most likely linked to an increase in marine primary productivity, as revealed by C org /P total molar ratio, as well as Al-normalized Ba, and Zn concentrations, and their relationship with TOC. Data further attest to a moderate to low marine primary productivity during pre- and post-TOAE times. During the T-OAE, an increase in the marine primary productivity was linked to intensified continental weathering, facilitated by semi-humid climate conditions. Compilation of TOC data from various depositional settings in the eastern Tethys Ocean revealed a high spatial variability, highlighting the importance of local intrabasinal processes on organic matter accumulation.

Generation of Geochemical Exploration Targets from Regional Stream Sediment Data Using Principal Component and Factor Ana

A regional-scale stream sediment geochemical sampling was carried out with an averagesampling density of one sample per nine square-kilometre in Kiteto District, Manyara Region.A total of 358 stream sediment samples were collected and analysed for major and traceelements by X-ray fluorescence (XRF) and fire assay with atomic absorption spectrometry(AAS) finish methods. In this study, Factor and Principal Component Multivariate (FPCM)analyses have been used to the stream geochemical data to delineate potential mineralizationzones by plotting correlated factors as geochemical anomaly maps. Four factors that accountfor 73.7% of the total variance of the stream sediment geochemical data were established.Factor 1: Ni–Ba–Co–Cu–Sr which possibly defines the underlying metamorphosed graniticunits with some contribution from mafic and ultramafic rocks. Factor 2: Cr–Zn–Mn whichdefines crustal forming elements reflecting the mafic rocks. Factor 3 which entails Rb and Pbprobably attributed to metamorphosed granitic lithology. Factor 4 is arsenic, a chalcophileelement with affinity to sulfide phases. The FPCM analyses have been successfully indelineating potential target areas for gold, nickel and copper exploration in the study area.&#x0D; Keywords: Stream sediment; principal component; factor analysis; exploration targets;Kibaya-Kiteto, Manyara.

Erosion Risk Assessment for Prioritization of Conservation Measures in the Watershed of Genale Dawa-3 Hydropower Dam, Ethiopia

Sedimentation is a leading global problem that affects the environment and dams by reducing the live storage capacity of reservoirs and the life expectance of dams. Hence, prioritizing watersheds according to the risk of soil loss is crucial for extending the useful life of dams and reservoirs. The objectives of this study were to assess sediment flow in the Genale Dawa-3 reservoir, identify subbasins that are prone to soil erosion, and evaluate the impact of different management practices on minimizing sediment yields by using the Soil and Water Assessment Tool (SWAT) model. The SWAT model was calibrated and validated by observed streamflow and sediment data based on the SUFI-2 algorithm by SWAT-CUP, and its performance was assessed. The model simulated the average annual sediment yield; the input to the reservoir was 16.83 ton/ha/yr for the period of 1990–2015. From a total of 31 subbasins, 12 were categorized from high to very severe (11–60 ton/ha/yr) sediment-yielding subbasins and selected for sediment management. The simulated scenarios showed that the average annual sediment reductions at critical erosion hot spots in subbasins after the application of filter strips, soil/stone bund, terracing, and contour farming were 35.03%, 66.54%, 80.88%, and 53.11%, respectively. Therefore, this study concluded that reducing sediment yield by implementing terracing in critical areas at risk of soil erosion was more effective than other soil conservation measures. Overall, this research can help planners and decision-makers to implement appropriate soil conservation measures in the most erosive subwatersheds in order to extend the useful life of the Genale Dawa-3 hydropower dam and reservoir.

Early Late Triassic retro-foreland basin in response to flat subduction of the Paleo-Tethyan oceanic plate, SE Tibet

Syn-subduction basins bear significant implications to understand tectonic evolution of any fossil subduction zone. The late Paleozoic to early Mesozoic (Paleo-Tethyan) tectonics of the eastern and southeastern Tibetan Plateau (i.e., the Sanjiang Orogenic Belt) is featured by ocean-continent subduction systems. A huge pile of volcanic-absent sedimentary succession developed in the middle segment of the Sanjiang orogenic belt, its age and tectonic nature remain unclear. Detailed geological mapping and zircon U-Pb dating results demonstrate that the early Late Triassic volcanic-absent succession comprises the nonmarine Maichuqing Formation in the lower part and the shallow marine Sanhedong Formation in the upper part. The Maichuqing Formation consists of coarse to fine-grained sandstone, siltstone and mudstone with abundant basal erosional surfaces, trough and planar cross-beddings, ripples, mudcracks, and plant fragments. The Sanhedong Formation comprises predominantly bioclastic limestones interlayered with marl, calcareous-muddy siltstone, and calcareous sandstone with abundant bivalve fossils. Syn-sedimentation deformation structures, such as slump folds and associated normal faults are common, suggesting intense tectonism during deposition. Synthesizing sedimentary data, paleocurrent and provenance results, combined with other available data, demonstrate that the volcanic-absent succession deposited within a retro-foreland basin along the rear part of the Permian-Triassic Jomda-Weixi-Yunxian arc in response to flat-subduction of the Paleo-Tethyan Ocean during the early Late Triassic time.

Ecogeochemistry of Mercury in Aquatic Organisms and their Habitat on the Territory of Moscow

The issue of technogenic mercury pollution of aquatic ecosystems in urban areas of Moscow was considered based on the sampling data of aquatic plants, amphibians and bottom sediments of the water bodies under study. Quantitative assessments of the mercury distribution in wild life and inorganic nature components of 33 water bodies of Moscow in both protected areas and beyond. Information was provided on the average percentage of mercury in some components of freshwater ecosystems. An excess of the average ecotoxicant concentration values in the in duckweed family (24 ng/g dry wt), amphibians (177 ng/g dry wt) and bottom sediments (57 ng/g dry wt) in the territory of Moscow was revealed versus bulk earth and background values. A significant correlation of mercury concentration for the natural components under study (R&gt;0.4) was identified.

Identifying the acute toxicity of contaminated sediments using machine learning models

Ecological risk assessment of contaminated sediment has become a fundamental component of water quality management programs, supporting decision-making for management actions or prompting additional investigations. In this study, we proposed a machine learning (ML)-based approach to assess the ecological risk of contaminated sediment as an alternative to existing index-based methods and costly toxicity testing. The performance of three widely used index-based methods (the pollution load index, potential ecological risk index, and mean probable effect concentration) and three ML algorithms (random forest, support vector machine, and extreme gradient boosting [XGB]) were compared in their prediction of sediment toxicity using 327 nationwide data sets from Korea consisting of 14 sediment quality parameters and sediment toxicity testing data. We also compared the performances of classifiers and regressors in predicting the toxicity for each of RF, SVM, and XGB algorithms. For all algorithms, the classifiers poorly classified toxic and non-toxic samples due to limited information on the sediment composition and the small training dataset. The regressors with a given classification threshold provided better classification, with the XGB regressor outperforming the other models in the classification. A permutation feature importance analysis revealed that Cr, Cu, Pb, and Zn were major contributors to toxicity prediction. The ML-based approach has the potential to be even more useful in the future with the expected increase in available sediment data.

Seabed Classification Using Multibeam Echosounder Measurement Data

Multibeam Echosounder (MBES) utilizes acoustic waves emitted to the seafloor through a transmitter or transducer and records its reflective. The information obtained by MBES are depth data and the scattering value of the acoustic signal reflected by the object or the seabed, called backscatter. Acoustic backscatter can be used to classify objects or the seabed such as shipwrecks or seabed sediments. This study focuses on seabed classification using an acoustic backscatter obtained from the measurement at Alur Pelayaran Barat Surabaya (APBS). The data used in this research are acoustic backscatter from bathymetry data extraction and ground truth data of sediments. This study found the fine sand sediments with backscatter value −15.56 dB, and clayey silt sediments with backscatter value −24.36 dB. The correlations between backscatter and seabed sediments in study area were classified into four classes, clay class sediments with backscatter intensity range [(−33.81) – (−28)] dB, clayey silt class sediments with backscatter intensity range [(−27.99) – (−23)] dB, sandy silt backscatter intensity range [(−22.9) – (−18)] dB, and sand class sediments with backscatter intensity range [(−17.99) – (−10)] dB. Based on the results data are known in the study area of seabed conditions dominated by sediments type sandy silt.