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Previous studies have demonstrated that vegetation‐generated turbulence can enhance erosion rate and reduce the velocity threshold for erosion of non‐cohesive sediment. This study considered whether vegetation‐generated turbulence had a similar influence on natural cohesive sediment. Cores were collected from a black mangrove forest with aboveground biomass and exposed to stepwise increases in velocity. Erosion was recorded through suspended sediment concentration. For the same velocity, cores with pneumatophores had elevated turbulent kinetic energy compared to bare cores without pneumatophores. However, the vegetation‐generated turbulence did not increase bed stress or the rate of resuspension, relative to bare cores. It was hypothesized that the short time‐scale fluctuations associated with vegetation‐generated turbulence were not of sufficient duration to break cohesion between grains, explaining why elevated levels of turbulence associated with the pneumatophores had no impact on the erosion threshold or rate. Plain Language Summary: Mangrove habitat grows by retaining sediment. To restore these systems, it is necessary to understand how vegetation influences the transport and retention of sediment. This study used sediment cores collected from the interior of a mangrove forest to study how the aboveground roots, called pneumatophores, influence hydrodynamic conditions and sediment transport, and in particular the onset and rate of sediment erosion. Individual pneumatophores generate eddies that enhance turbulence, compared to conditions without pneumatophores. In sandy soil, vegetation‐generated turbulence can enhance erosion. However, in this study, vegetation‐generated turbulence did not increase the rate of erosion for natural cohesive (muddy) sediment, suggesting that the mangrove forest interior has naturally greater resistance to erosion and sediment loss. Key Points: For the same velocity, cores with pneumatophores had higher turbulent kinetic energy (TKE) compared to cores without pneumatophoresUnlike sands, the inception of erosion and erosion rates for cohesive sediment were better predicted by bed shear stress than by TKEModelers should parameterize erosion within vegetation differently for cohesive and non‐cohesive sediment [ABSTRACT FROM AUTHOR]

Mediterranean high-mountain lakes are being increasingly affected by strong Saharan dust deposition events. However, the ecological impacts of these severe atmospheric episodes remain largely unknown. We examined the effects of a strong Saharan dust intrusion to the Iberian Peninsula in 2022 on the physicochemical parameters and prokaryotic communities in sediments of nine high-mountain lakes of Sierra Nevada (Spain) located above 2800 m.a.s.l and in different orientations (north vs. south). A previous year (2021), with lower Saharan dust deposition with respect to 2022, was used for interannual comparisons. The strong dust deposition to the high-mountain lakes resulted in a significant increase in sediment nutrient availability which was linked to changes in the composition of prokaryotic communities. Decreases in alpha diversity and changes in beta diversity of prokaryotic communities were mainly observed in lakes located in the south compared to the north orientation likely because the former was more affected by the atmospheric dust deposition episode. Dust intrusion to the high-mountain lakes resulted in significant changes in the relative abundance of specific genera involved in important nutrient cycling processes such as phosphate solubilization, nitrogen fixation, nitrification, and denitrification. Saharan dust deposition also increased predicted microbial functionality in all lakes. Our findings show that severe atmospheric dust inputs to remote high-mountain lakes of Sierra Nevada can have significant biogeochemical and biodiversity consequences through changes in nutrient availability and prokaryotic communities in sediments of these freshwater ecosystems. This information contributes to understanding how Mediterranean high-mountain lakes of Sierra Nevada face strong intrusions of Saharan dust and their ecological consequences. [ABSTRACT FROM AUTHOR]

Reactive iron (FeR) serves as an important sink of organic carbon (OC) in marine surface sediments, which preserves approximately 20% of total OC (TOC) as reactive iron-bound OC (FeR-OC). However, the fate of FeR-OC in subseafloor sediments and its availability to microorganisms, remain undetermined. Here, we reconstructed continuous FeR-OC records in two sediment cores of the northern South China Sea encompassing the suboxic to methanic biogeochemical zones and reaching a maximum age of ~100 kyr. The downcore FeR-OC contributes a relatively stable proportion of 13.3 ± 3.2% to TOC. However, distinctly lower values of less than 5% of TOC, accompanied by notable 13C depletion of FeR-OC, are observed in the sulfate-methane transition zone (SMTZ). FeR-OC is suggested to be remobilized by microbially mediated reductive dissolution of FeR and subsequently remineralized, the flux of which is 18–30% of the methane consumption in the SMTZ. The global reservoir of FeR-OC in microbially active Quaternary marine sediments could be 19-46 times the size of the atmospheric carbon pool. Thus, the FeR-OC pool may support subseafloor microorganisms and contribute to regulating Earth's carbon cycle. This study shows that iron-bound organic carbon (FeR-OC) is generally persistent but can be remobilized during iron reduction and utilized by microbes in subseafloor sediments. This sedimentary FeR-OC pool may contribute to regulating Earth's carbon cycle. [ABSTRACT FROM AUTHOR]

Invasive Spartina alterniflora (S. alterniflora) has significant impacts on sediment biogeochemical cycling in the tidal wetlands of estuaries and coasts. However, the impact of exotic Spartina alterniflora invasion on greenhouse gases (GHGs) production dynamics in sediments remain limited. Here, we investigated the dynamics of sediment physicochemical properties, GHGs production rates, and microbial gene abundances in a native Cyperus malacensis habitat and three invasive S. alterniflora habitats (6-, 10-, and 14-year) in the Minjiang River Estuary, China. The methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) production rates varied both spatially and seasonally, while microbial gene abundances (bacterial and fungal gene abundances) and organic matter (TOC and TN) only varied spatially. GHGs production rates were also characterized by higher values in surface sediment (0-10 cm) compared to subsurface sediment (10-20 cm) and by seasonal variations with higher values in summer than in winter. S. alterniflora invasion can significantly increase CH4 and CO2 production rates, organic matter, and microbial gene abundances (p < 0.05). Temperature, organic matter and microbial gene abundances were the most dominating factor controlling the spatio-temporal variations of CH4 and CO2 production rates. Overall, our findings highlighted the significant role of S. alterniflora invasion in regulating GHGs production rates in coastal wetland sediments and provided fundamental data for estimating GHGs emissions and carbon sequestration in the complex tidal wetlands. [ABSTRACT FROM AUTHOR]

Endolithic sponges are key players in carbonate cycling on coral reef systems. While their bioerosion of reef framework is relatively well studied, their role in biogenic sediment generation is poorly understood. In this study, the sedimentary attributes and production rates of eight Caribbean endolithic sponge species were characterized. The findings revealed notable species‐specific variations in sediment production rates (range: 1.0–6.3 kg CaCO3 m−2 yr−1), alongside consistency in sediment characteristics (modal sizes ranging from 39 to 48 μm). The species‐specific rates were used to explore reef‐scale variations in sponge‐derived sediment generation across 50 reef sites in the Mexican Caribbean. Significant between‐site variability was observed, with estimated annual sediment production ranging from < 0.01 to 0.84 kg m−2 of reef. Production was primarily driven by sponge abundance, with discernible spatial variations in the contributions of different species, which could be related to variability in local environmental conditions. The rapidity at which these sediment producers can utilize dead coral substrates, coupled with their positive response to the changing marine environment, highlights the growing importance of these sponges in modern degraded Caribbean reef systems. [ABSTRACT FROM AUTHOR]

The Qicheng city wall is located in Puyang, Henan Province, China, and it is an important archaeological site from the Neolithic period in the North China Plain region. A trench across the northwest corner of the city wall revealed an 11 m thick sediment sequence, closely associated with human activities, which provides valuable records for the dating and environmental evolution of the site. In this study, we have applied field geological investigation, grain size analysis, optically stimulated luminescence (OSL) dating, and radiocarbon (14C) dating to reveal the history and changes in the site. The ancient city wall was built on the sedimentary sequence (U1) of the high terrace of the Ancient Yellow River. The upper 11 m thick sedimentary sequence (U2) recorded early moat sedimentation (U2 L) and was followed by three cycles of paleosol-flooding deposits (U2 U). The quartz OSL signals of the U2 silts are extremely bright, indicating high sensitivity. Partial bleaching was observed as well. The quartz OSL single-grain SAR dating results are consistent with that of charcoal 14C dating and are closer to the 'true' burial ages of the sediments than those obtained with multiple grains. By using a Bayesian statistical model, a chronological framework for the U2 sedimentary sequence was established. The earliest construction date of the Qicheng city wall is dating to 2100–1300 BC, during the late Longshan period, which is consistent with archaeological evidence (Li et al., 2015). The Qicheng city was not significantly affected by paleo-flooding prior to 870–960 AD, but experiences frequent flooding thereafter. [ABSTRACT FROM AUTHOR]

The post-Infrared Infrared Stimulated Luminescence (pIRIR) protocol has been successfully applied to date Quaternary sediments using the K-rich feldspar fraction (density ＜2.58 g/cm3). However, during the extraction of K-feldspar grains, Na-feldspar particles (density 2.58–2.62 g/cm3) may be included, especially within the medium grained fraction. However, the possible influence of Na-feldspar contamination on K-feldspar IRSL dating results has not been investigated in detail. In this study, we applied the pIRIR dating protocol to measure the coarse- and medium-grained K-and Na-feldspar fractions of eight aeolian samples from various regions. Blue-violet and yellow-green detection windows were used for derived the signals of K- and Na-feldspar, respectively, and we attempted to evaluate the influence of the contamination by Na-feldspar grains on feldspar pIRIR dating. Comparison of the three signals (K-feldspar blue, Na-feldspar blue, Na-feldspar yellow) from each sample showed that the influence of the IRSL blue signal from Na-feldspar grains on the signal of the K-feldspar fraction was < 1–3%. Because of high fading rates, the D e s or pIRIR ages obtained from the Na-feldspar yellow signal were underestimated. The Na-feldspar blue pIRIR D e s and ages were nevertheless consistent with their corresponding K-feldspar blue D e values and ages. This is because the few K-feldspar grains included within the Na-feldspar fraction emitted the greater part of the blue signals. From these observations, we conclude that the influence of Na-feldspar grains within the K-feldspar fraction on K-feldspar IRSL dating results can be ignored. [ABSTRACT FROM AUTHOR]

As a response of the coastal oceans to more severe anthropogenic disturbance, increasing coastal primary production has been more frequently observed in recent years. This raises the question of howthis progressive change reshapes the long-term carbonsequestration in thecoastal oceans. With this question inmind, we investigated the sediment organic matter (OM) preserved on the shelf of the northern SouthChina Sea (NSCS) where high primary production has been observed. Across this sediment core, relatively lowtotal organic carbon content of around 0.60%was observed. Fatty acids with less carbon numbers exhibit exponential decreases downward with degradation rate constants ranging from 0.10 to 0.17 y-1, no matter they were from single sources (14:0 presumably from marine OM and ai-15:0, i-15:0, 15:0 from bacterial OM) or mixed sources (16:0). Meanwhile fatty acids with more carbon numbers, either 18:0 and 24:0 from mixed sources, or 26:0 and 28:0 presumably fromterrestrial input, were less varied inconcentrationswithdepth. Thisdemonstrates a preferential decomposition of labile fatty acids during the early diagenesis of coastal sediment organicmatter. A decrease of labile fatty acids δ13Cvalueswas observed with the decomposition, from which kinetic isotope fractionations were predicted ranging from 0.7 to 1.5‰. This provides an isotopic constraint of the mixing model to quantify labile organicmatter from terrestrial input and local phytoplankton production, from which declined contribution of local phytoplankton production to labile fatty acids was identified in more recent sediment. This finding together with the low organic carbon content and rapid removal of fatty acids in the top sediment, demonstrates the poor preservation of labile organic matter on the shelf of NSCS, implying that the increasing primary production has not enhanced the coastal carbon sequest ration yet, but rather leads tomore intensified respiration with a potential risk toincrease the CO2 outgassing fromthe coastal oceans. [ABSTRACT FROM AUTHOR]

Sediment grain size characterization is one of the main components of aeolian geomorphology research. Sand particle size can determine the basic form of sand movement. The distribution and form of grain size parameters of different types of sediments were calculated using six surface types of sediments around Qixing Lake in the Kubuqi Desert: Mobile dune Semi-fixed dune Fixed dune Lakeshore terrace Wetland and Grassy flat wetland The results showed that the surface sediments were mainly composed of medium sand and fine sand, and all types were negatively skewed. The differentiation pattern of the saltation component and suspended component of the surface sediment is characterized by a twostage pattern. The percentage contribution of suspended components in lakeshore terraces, wetlands, and Grassy flat wetlands (total average 21.07%) is more than twice that of mobile dunes, semifixed dunes, and fixed dunes (total average 9.47%). This suggests that mobile dunes, semi-fixed dunes, and fixed dunes are not the main contributing surface type of suspended material in the Qixing Lake area. [ABSTRACT FROM AUTHOR]

The polar regions are the fastest warming places on earth. Accelerated glacial melting causes increased supply of nutrients such as metal oxides (i.e., iron and manganese oxides) into the surrounding environment, such as the marine sediments of Potter Cove, King George Island/Isla 25 de Mayo (West Antarctic Peninsula). Microbial manganese oxide reduction and the associated microbial communities are poorly understood in Antarctic sediments. Here, we investigated this process by geochemical measurements of in situ sediment pore water and by slurry incubation experiments which were accompanied by 16S rRNA sequencing. Members of the genus Desulfuromusa were the main responder to manganese oxide and acetate amendment in the incubations. Other organisms identified in relation to manganese and/or acetate utilization included Desulfuromonas, Sva1033 (family of Desulfuromonadales) and unclassified Arcobacteraceae. Our data show that distinct members of Desulfuromonadales are most active in organotrophic manganese reduction, thus providing strong evidence of their relevance in manganese reduction in permanently cold Antarctic sediments. [ABSTRACT FROM AUTHOR]

The object of this research is the polychlorinated biphenyls (PCBs) in sediments along Shatt Al-Arab estuary, Iraq. The study examines the problem of river PCB pollution. PCB effects on humans include cancer, impaired reproduction, neuro-developmental effects in infants, immunotoxicity and endocrine disruption. PCBs lead to liver damage and stimulate changes in the DNA sequence. The Shatt Al-Arab Estuary is formed in southern Iraq near Al-Qurna city after the confluence of the Tigris and Euphrates Rivers. The Shatt Al-Arab Estuary region is shared between Iraq and Iran. The Estuary receives pollutants when it is passing during Basrah City regions, due to industrial, agricultural and human activities which discharge the pollutants to the Estuary without treatment. The concentrations of Σ13 PCBs compound in sediment samples were determined and analyzed at each site by using gas chromatography-mass spectrometry (GC-MS, Agilent). Six sites were chosen along Shatt Al-Arab Estuary. They are Al-Qurna (S1), Al-Deer (S2), Al-Qarma (S3), Al-Ashar (S4), Abi Al-Khasib (S5) and Al-Fao (S6), at Basrah city, south of Iraq. Sediment samples were collected seasonally, starting from Autumn season on September 2019 to summer season on July 2020. The Σ13 (PCB-18, PCB-29, PCB-31, PCB-28, PCB-44, PCB-52, PCB-101, PCB-141, PCB-149, PCB-138, PCB-153, PCB-189, and PCB-194) concentrations at the sediment samples ranged from 4.48 ng/g in Al-Deer site during summer season to 27.75 ng/g in Al-Ashar site during winter season for all selected sites. The Al-Deer site were found to have the lowest mean of PCBs its 0.345 ng/g and Al-Ashar site were found to have the highest mean of PCBs its 2.135 ng/g. PCBs concentrations in sediment samples during autumn, winter, spring and summer seasons ranged from 7.75 to 21.68 ng/g, 16.25 to 27.75 ng/g, 7.28 to 22.01 ng/g and 4.48 to 14.41 ng/g, respectively. The congener distribution patterns in these samples indicate the dominance highly chlorinated congeners (tri- and hexa-PCBs) in comparison with remaining others PCBs congeners. This project is the first of its kind in Basrah and all Iraq that reports PCB concentrations in the region and is considered a baseline study and can be used for subsequent studies. [ABSTRACT FROM AUTHOR]

This study aims to classify seafloor sediments using physics‐inspired and data‐driven soil models combined with machine learning algorithms and oversampling techniques. The field data used for the input variables include porosity, S‐ and P‐wave velocities and depth. The soil information reported in the original literature and the "six reference sediments" and effective stress‐versus‐depth models proposed by the previous study confirm the sediment type across all of the input variables. We use three machine learning algorithms and four oversampling methods to enhance the performance accuracy and overcome data imbalance in the minority class. The results show that the averaged accuracy of sediment classification with original data corresponds to 0.88 for porosity, 0.61 for S‐wave velocity, and 0.97 for P‐wave velocity. In particular, the enhanced accuracy with oversampled input variables becomes more pronounced when the depth data are considered in a dataset. The class‐oriented grouping method newly proposed in this study appears to be a robust approach to enhancing performance. Surprisingly, model‐based input variables lead to the best performance in all cases. The proposed analyses conducted using machine learning algorithms and oversampling techniques within the physics‐inspired models could be extended to obtain a first‐order assessment of marine sediment properties. [ABSTRACT FROM AUTHOR]

Background: Myxococcota, characterized by their distinct social lifestyles, are widely distributed micro-predators in global sediments. They can feed on a wide range of bacterial, archaeal, and fungal prey. Myxococcota are capable of producing diverse secondary metabolites, playing key roles in microbial food webs, and regulating the microbial community structures in different ecosystems. However, Myxococcota are rarely pure cultured due to the challenging and stringent culturing conditions. Their natural distribution, niche differentiation, and predator–prey relationships in a specific habitat are poorly understood. Results: In this study, we conducted a comprehensive analysis of the 16S rRNA gene sequence data from public databases and our collection. We compared the abundance, diversity, and distribution patterns of Myxococcota in various habitats, with a specific focus on mangroves. We found that Myxococcota accounted for 1.45% of the total prokaryotes in global sediments based on the abundance of 16S rRNA genes. Myxococcota are abundant and diverse in mangrove sediments. They tend to be more generalistic in mangroves than in other habitats due to their wide niche breadth. Besides, the deterministic processes (variable selection) influenced the assembly of mangrove Myxococcota communities significantly more than stochastic processes. Further, we determined that environmental factors explained a greater amount of total community variation in mangrove Myxococcota than geographical variables (latitude and sediment depth). In the end, through the analysis of microbial co-occurrence networks, Myxococcota emerges as a key component and functions as a connector in the mangrove microbial community. Conclusions: Our study enhances comprehension of mangrove Myxococcota's biogeography, assembly patterns, driving factors, and co-occurrence relationships, as well as highlights their unique niche and ecological importance in mangrove sediments. [ABSTRACT FROM AUTHOR]

The Skagerrak basin represents the main sink area for fine-grained sediment in the North Sea region and constitutes a natural deposition center for sediments that are supplied from the Atlantic, the Baltic Sea and the surrounding continental margins and coasts. However, the exact sources and their proportional contributions to the North Sea sediments and to the Skagerrak deposits are not well understood. To trace the predominant sources of the sediment and to gain a better understanding of the sedimentary processes in the North Sea and the Skagerrak basin, radiogenic Sr, Nd, and Hf isotope signatures and clay mineral compositions of the detrital clay fraction of surface sediment samples from the North Sea, the Scandinavian margins and the Baltic Sea were measured. The results indicate that the major source for Skagerrak clay-size sediments is the northern North Sea but Scandinavia as well as the southern North Sea including the southern England coast also contribute material. Seabed and coastal erosion in the northern North Sea are enhanced by the inflowing Atlantic Currents, which provide the Skagerrak with high amounts of clay size sediments. In contrast, the southern North Sea, the Baltic Sea and mid-European rivers such as Weser, Elbe and Ems are only minor contributors. As Skagerrak deposits are dominated by clay sized material (up to 60%), the reconstructed sediment processes in this study deviate from findings in previous sediment budget studies, which were based on both clay and silt fraction and indicated predominant influences from the southern North Sea. These results highlight that coastal and seabed erosion in the North Sea is a previously underestimated source of fine-grained sediments for depocenters in the entire North Sea. With regard to climate change, the global sea-level rise will likely enhance erosional processes and can therefore significantly influence the sediment budget of the entire North Sea. [ABSTRACT FROM AUTHOR]

The efficiency of beach recovery during a time of moderate waves following storm waves is closely related to the interaction between dynamics, sediment, and the landform. The existing studies mainly focus on the description of erosion and accretion characteristics, while the response and feedback mechanism of beach berm sediment have not been elucidated. The main controlling factors of recovery efficiency are not clear. In this paper, field observation and the XBeach numerical model are utilized on the sandy beach in Puqian Bay, China, to capture high-frequency cross-shore data during the post-storm recovery period. The variation characteristics and rules of berm elements, including berm ridge height and slope on two sides of the berm ridge, are analyzed. It is observed that the berm constantly changes to adapt to dynamic conditions. Additionally, a correlation between volume change and certain landform parameters is proposed, leading to the identification of a new relationship in wave run-up. The new forum reflects berm influence and considers the berm ridge and berm width. [ABSTRACT FROM AUTHOR]

Fine sediment infiltration and subsequent clogging in a gravel bed affect several fluvial, ecological, and biological processes, resulting in the degradation of the river ecosystem. Despite many experimental and a few numerical studies, the process is yet to be entirely understood. We employed a pure Lagrangian framework, called the Discrete Element Method (DEM), to numerically investigate the infiltration process. Special attention is given to tackling the issue of non-spherical and irregular particle shapes and particle size distributions (PSDs) in numerical simulations. Due to computational limitations, these aspects were either not considered or simplified in previous numerical studies. We implicitly included non-spherical and irregular shape effects through rolling resistance models, which do not cause excessive computational overhead. Our study shows that rolling resistance models greatly influence packing and fine sediment infiltration. However, they may also lead to unphysical particle behavior; thus, they should be carefully used in numerical simulations. Oversimplified PSDs do not mirror natural systems, and full PSDs pose computational challenges. Sufficient grain classes are needed to mimic the non-homogeneity and poly-dispersity found in natural fluvial sediments. The infiltrating characteristics of sand concerning PSD and shape effects are linked to size ratio D15,Gravel/D85,Sand, assuring physical and realistic modeling of the infiltration process. [ABSTRACT FROM AUTHOR]

This study aimed to measure spatial and temporal distributions of total phenolic compounds and their ecological and health hazards using UV-vis spectrophotometers as a low-cost, fast, simple method in water and sediments collected from Timsah Lake, Suez Canal, Egypt, 2022. Also, assessing highly adaptive fungal species associated with contamination is designed. Due to human and environmental activities and industrial waste discharges, Timsah Lake is increasingly threatened by all kinds of pollutants. The results indicated that the seasonal concentration means of the phenolic compounds were winter (0.229) > spring (0.161) > summer (0.124) > autumn (0.131) mg/l and winter (3.08) > summer (2.66) mg/g in water and sediment samples, respectively. The result has shown that the phenol concentrations in all stations were more than 0.005 and 0.1 mg/l for Egyptian National Standards and World Health Organization (WHO) for drinking water but less than the limits of 1 mg/l for wastewater. Notably, the fungi recorded the highest counts during spring, totaling 397 colonies/100 ml of water and 842 colonies/gram of sediment. Four isolates of fungi were identified and deposited in the GenBank database by Aspergillus terreus, Aspergillus terreus, Penicillium roqueforti, and Penicillium rubens under accession numbers OR401933, OR402837, OR402878, and OR424729, respectively. Moreover, ecological risk (RQ) for the total phenolic compounds was > 1 in all investigated stations for water and sediments. The hazard quotient is HQ < 1 in all seasons in water and sediments except winter. The hazard index (HI) in water and sediments for children is higher than for adults. It can be concluded that the low-cost, fast, simple method for determining phenolic content in water and sediment samples, using UV-vis spectrophotometry, was useful for predicting the reactivates of a wide variety of phenol and their derivatives. Furthermore, it can be concluded that Periodic assessments of water quality and strict regulations are necessary to safeguard this vital resource from pollution and ensure the well-being of future generations. Finally, policymakers and water treatment specialists might use the information from this research to reduce these chemical pollutants in Egypt. [ABSTRACT FROM AUTHOR]

In the Tsitsa River catchment of the Eastern Cape Province, South Africa, concerns regarding the sedimentation of a proposed large, multipurpose, in-channel water storage scheme prompted investigations of sub-catchment suspended sediment loads and yields. Confluence-based fingerprinting and source apportionment was undertaken to explore whether this simple approach could identify relative sub-catchment contributions to downstream sediment loads, supplementing modelling and direct sampling. In November 2018, fine sediment sequestered in bed substrates was sampled above and below confluences, using a resuspension technique. The < 63 µm sample fraction underwent analysis of mineral magnetic properties, gamma emitting radionuclide activities and geochemistry to identify suitable tracers. Conservatism and range tests were used to select different combinations of composite fingerprints at seven confluences. Bivariate source apportionment using an unmixing model showed that the approach could be used as a preliminary means of determining relative sub-catchment sediment contributions. Catchment characteristics such as geology and land cover, as well as land tenure and management, were considered as explanatory factors for the difference in sediment contributions. The results for most sub-catchments were broadly similar to those from other studies. Shortcomings of this approach included the reliance on a single sampling effort, and uncertainty associated with sub-catchment sediment transport and residence times. [ABSTRACT FROM AUTHOR]

This study aimed at assessing the long term impacts of watershed management interventions and scenarios on sediment export reduction in the data-scarce region of the Yezat watershed in north-west Ethiopia. The modified ecosystem services valuation model (InVEST) was employed to evaluate the amount of sediment export in the watershed. Different watershed management intervention scenarios were applied to evaluate the effectiveness of watershed management interventions on sediment export reduction. The results of the study showed that the mean annual sediment yield was 35 tons ha yr in 20000, due to the expansion of cultivated land and built-up area. Conversely, it decreased from 35 ton ha yr in 2000 -18.4 ton ha yr in 2021 due to watershed management interventions. On the contrary, moderate, severe, and very severe categories of sediment export intensity were high in 2000. But it decreased in 2021 due to watershed management interventions. The mean annual sediment export in the baseline scenario (BS) was 35 tons per year, which was reduced to 13.39 tons per year, 3.46 tons per year, and 1.17 tons per year in the reforestation scenario, soil/stone bund, and integrated scenarios, respectively. The result revealed that areas covered by high sediment severity classes were reduced. [ABSTRACT FROM AUTHOR]

Ice sheet models must be able to accurately simulate palaeo ice sheets to have confidence in their projections of future polar ice sheet mass loss and resulting global sea-level rise, particularly over longer timescales. This requires accurate reconstructions of the extent and flow patterns of palaeo ice sheets using real-world data. Such reconstructions can be achieved by tracing the detrital components of offshore sedimentary records back to their source areas on land. For Antarctica, however, sediment provenance data and ice sheet model results have not been directly linked, despite the complimentary information each can provide on the other. Here, we present a computational framework (Tracing Antarctic Sediment Provenance, TASP) that predicts marine geochemical sediment provenance data using the output of numerical ice sheet modelling. The ice sheet model is used to estimate the spatial pattern of erosion rates and to trace ice flow pathways. Beyond the ice sheet margin, approximations of modern detrital particle transport mechanisms using ocean reanalysis data produce a good agreement between our predictions for the modern ice sheet/ocean system and seabed surface sediments. These results show that the algorithm could be used to predict the provenance signature of past ice sheet configurations. TASP currently predicts neodymium isotope compositions using the PSUICE3D ice sheet model, but thanks to its design it could be adapted to predict other provenance indicators or use the outputs of other ice sheet models. [ABSTRACT FROM AUTHOR]

Riverbed sediments have been identified as temporary and long-term accumulation sites for microplastic particles (MPs), but the relocation and retention mechanisms in riverbeds still need to be better understood. In this study, we investigated the depth-specific occurrence and distribution (abundance, type, and size) of MPs in river sediments down to a depth of 100 cm, which had not been previously investigated in riverbeds. In four sediment freeze cores taken for the Main River (Germany), MPs (≥ 100 µm) were detected using two complementary analytical approaches (spectroscopy and thermoanalytical) over the entire depth with an average of 21.7 ± 21.4 MP/kg or 31.5 ± 28.0 mg/kg. Three vertical trends for MP abundance could be derived, fairly constant in top layers (0–‍30 cm), a decrease in middle layers (30–60 cm), and a strong increase in deep layers (60–100 cm). The dominant polymer types were polyethylene (PE), polypropylene (PP), and polystyrene (PS). Polyethylene terephthalate (PET) and PP were also found in deep layers, albeit with the youngest age of earliest possible occurrence (EPO age of 1973 and 1954). The fraction of smaller-sized MPs (100–500 µm) increased with depth in shallow layers, but the largest MPs (> 1 mm) were detected in deep layers. Based on these findings, we elucidate the relationship between the depth-specific MP distribution and the prevailing processes of MP retention and sediment dynamics in the riverbed. We propose some implications and offer an initial conceptual approach, suggesting the use of microplastics as a potential environmental process tracer for driving riverbed sediment dynamics. [ABSTRACT FROM AUTHOR]

Ivermectin (IVM) is a widely used antiparasitic. Concerns have been raised about its environmental effects in the wetlands of Río de la Plata basin where cattle have been treated with IVM for years. This study investigated the sublethal effects of environmentally relevant IVM concentrations in sediments on the Neotropical fish Prochilodus lineatus. Juvenile P. lineatus were exposed to IVM-spiked sediments (2 and 20 µg/Kg) for 14 days, alongside a control sediment treatment without IVM. Biochemical and oxidative stress responses were assessed in brain, gills, and liver tissues, including lipid damage, glutathione levels, enzyme activities, and antioxidant competence. Muscle and brain acetylcholinesterase activity (AChE) and stable isotopes of 13C and 15N in muscle were also measured. The lowest IVM treatment resulted in an increase in brain lipid peroxidation, as measured by thiobarbituric acid reactive substances (TBARs), decreased levels of reduced glutathione (GSH) in gills and liver, increased catalase activity (CAT) in the liver, and decreased antioxidant capacity against peroxyl radicals (ACAP) in gills and liver. The highest IVM treatment significantly reduced GSH in the liver. Muscle (AChE) was decreased in both treatments. Multivariate analysis showed significant overall effects in the liver tissue, followed by gills and brain. These findings demonstrate the sublethal effects of IVM in P. lineatus, emphasizing the importance of considering sediment contamination and trophic habits in realistic exposure scenarios. [ABSTRACT FROM AUTHOR]

The paper presents research results obtained during the exploration of copper and silver deposits on the southern rim of the Wolsztyn–Pogorzela High in terms of identification of the regional geological structure of Permian and Mesozoic sediments, with particular focus on tectonic zones. It discusses a new methodology of developing seismic and gravimetric data in the form of sections of effective reflection coefficients (ERC) and vertical gravimetric cross-sections, which in combination with borehole logging allowed for the identification or an update of the knowledge about regional tectonic zones which are missing from the maps of the sub-Zechstein substrate prepared to date. The discussion of the methodology uses the example of two tectonic zones: the Rawicz and Oleśnica grabens. Conversion of seismic sections into ERC cross-sections made it possible to trace strata of smaller thickness and facilitated the identification of low-amplitude dislocations. Vertical gravimetric cross-sections confirm the credibility of the interpreted faults and grabens, also showing whether the faults are deeply rooted. Historical geophysical materials developed in this manner constitute an important supplement to the identification of the geological structure of the Lower Silesian Basin and in particular, the tectonic zones which may provide ways of migration and circulation of solutions, as well as the ore generation zones. The collected materials may be used to supplement the structural and tectonic maps of the sub-Zechstein substrate in the Lower Silesian Basin, and the applied methodology and data analysis may be used in other regions of Poland. [ABSTRACT FROM AUTHOR]

Landslides influence fluvial suspended sediment transport by changing sediment supply and grain size, which alter suspended sediment concentrations and fluxes for a period of time after landsliding. To investigate the duration and scale of altered suspended sediment transport due to landsliding, we analyzed suspended sediment concentration and water discharge measurements at 87 gauging stations across Taiwan over an 11-year period after Typhoon Morakot, which generated nearly 20 000 landslides in 2009. At each gauging station, we computed annual rating curves to quantify changes over time in the sensitivity of suspended sediment concentrations to water discharge. Among the 40 stations in basins that were impacted by landsliding, the discharge-normalized rating curve coefficient ã was higher than that before Morakot by a factor of 5.1±1.1 (mean ± standard error) in 2010, the first year after Morakot. The rating curve exponent b did not decrease at most stations until a year later (2011), when the average b value was lower than that before Morakot by 0.25±0.05. Across the compilation of gauging stations, post-Morakot changes in discharge-normalized sediment concentration (ã) were positively correlated with landslide intensity for 7 years after Morakot, while post-Morakot changes in the exponent of the discharge–concentration relationship (b) were negatively correlated with landslide intensity from 2011 to 2014. This reflects a tendency for larger changes in ã and b to occur in basins with more intense landsliding. At 26 of these 40 stations, elevated values of ã declined after the initial post-Morakot peak, consistent with a gradual return to pre-Morakot suspended sediment transport conditions. Exponential regressions to these ã values reveal a median characteristic decay time of 8.8 years (interquartile range: 5.7–14.8 years). Values of ã increased more and declined faster in basins with more intense landsliding, with a mean characteristic decay time of 6 years in the basins hit hardest by landsliding. Furthermore, changes in ã and b tended to be larger in basins with more intense landsliding. At stations that were not impacted or only minimally impacted by landsliding, neither ã nor b exhibited systematic responses to Morakot. To quantify the effect of landsliding on sediment discharge, we compared the measured sediment discharges after Morakot to the hypothetical sediment discharges that would have occurred if Morakot had induced no landslides, calculated by applying each station's pre-Morakot rating curve to its post-Morakot water discharge history. This analysis suggests that Morakot-induced landsliding increased sediment discharge by as much as > 10-fold in some basins in the 1–2 years after Morakot. Together, these results indicate that the influence of Morakot-induced landsliding on rating curves was large shortly after Morakot but diminished in less than a decade in most of the study rivers and will be imperceptible in another few decades in all of the study rivers. To the extent that these results are applicable to other landscapes, this suggests that periods of elevated sediment transport efficiency after landsliding should persist for years to decades, even if the landslide deposits persist for centuries to millennia. [ABSTRACT FROM AUTHOR]

This study assessed the impacts of the land use/cover (LULC) and climate changes on the runoff and sediment flows in the Megech watershed. The Geospatial Water Erosion Prediction Project (GeoWEPP) was used to assess LULC and climate changes' impact on runoff, soil loss, and sediment yield. The QGIS 2.16.3 plugin module for land use change evaluation (MOLUSCE) tool with the cellular automata artificial neural network (CA-ANN) was used for LULC prediction based on historical data and exploratory maps. Two commonly used representative concentration pathways (RCPs)—4.5 and 8.5—were used for climate projection in the 2030s, 2050s, and 2070s. The LULC prediction analysis showed an expansion of cropland and settlement areas, with the reduction in the forest and rangelands. The climate projections indicated an increase in maximum temperatures and altered precipitation patterns, particularly with increased wet months and reduced dry periods. The average annual soil loss and sediment yield rates were estimated to increase under both the RCP4.5 and RCP8.5 climate scenarios, with a more noticeable increase under RCP8.5. By integrating DEM, soil, land use, and climate data, we evaluated runoff, soil loss, and sediment yield changes on only land use/cover, only climate, and the combined impacts in the watershed. The results revealed that, under all combined scenarios, the sediment yield in the Megech Reservoir was projected to substantially increase by 23.28–41.01%, showing a potential loss of reservoir capacity. This study recommends strong climate adaptation and mitigation measures to alleviate the impact on land and water resources. It is possible to lessen the combined impacts of climate and LULC change through implementing best-management practices and adaptation strategies for the identified scenarios. [ABSTRACT FROM AUTHOR]

The composition of the trilobite fauna from the Devonian Paraná Basin in Brazil is still not fully elucidated. Although rich literature on the southern portion of this basin, the northwestern part has been poorly explored. In this study, we reveal new taxa and provide a comprehensive taxonomic composition of malvinoxhosan trilobites collected from the PragianEmsian sediments of Alto Garças Subbasin, Brazil. We report Burmeisteria notica, Metacryphaeus australis, Pennaia pauliana, Calmonia signifer and Kozlowskiaspis subseciva, well known elements from the southern portion of the Paraná Basin. Metacryphaeus meloi, unprecedented in the Paraná Basin, reveals itself here in the oldest biostratigraphic position in relation to other specimens reported from the Cabeças Formation (Frasnian-Famennian, Parnaíba Basin). We reveal a new species of Bainella, here described as Bainella (Belenops) sulmatogrossensis sp. nov. We discuss the biostratigraphic position of components of this fauna and their correlation with other Devonian units. Taking all together, our work provides a new picture about the trilobite taxonomic composition in the northwestern portion of the Paraná Basin, and can help our understanding of speciation pulses and dispersion patterns among the different Devonian basins in Gondwana. [ABSTRACT FROM AUTHOR]

The study records the extent of microplastics distribution in the surficial sediments of the Southern Ocean. This represents the first study of microplastics in the sediments of Prydz Bay, Southern Ocean. Prydz Bay is the largest embayment located in the Indian Ocean Sector of the Southern Ocean and receives sediments supplied by the Lambert Glacier/Amery Ice Shelf, draining approximately 10% of the total ice volume of Antarctica. It is an important site of circumpolar deep water (CDW) and Antarctic bottom water (AABW) formation. This study focuses on the distribution of microplastics in the sediments of the Prydz Bay, Southern Ocean with special reference to the ecological risk factor of these microplastics. The type distribution of microplastics revealed percent content as bead > fiber > fragment. Ecological risk factors (CF and PLI) of microplastics in sediment samples revealed a minor to major risk of these pollutants in the analyzed environment. Statistical analyses such as principal component analysis (PCA), ANOVA, Tukey's HSD test, and correlation analysis were performed to highlight the interrelationship of MPN with CF, PLI, pH, TOC, and sediment texture. The levels of microplastic pollution in the Prydz Bay are significant on a local scale, particularly around research stations. This report underlines the immediacy of microplastic pollution management in the Southern Ocean to maintain the serenity of this pristine marine habitat. So further research on the information of microplastics policy discussions to develop appropriate management responses. [ABSTRACT FROM AUTHOR]

The seabed of the Gunneklev Fjord in south-eastern Norway is covered with exceptionally soft contaminated sediment containing mercury and dioxins. The sediments have an undrained shear strength less than 1 kPa and a variable thickness of up to 2.5 m. To reduce the potential for leaching of contaminants from these sediments, Hydro Energy AS developed a remediation plan involving capping of the sediment. Significant uncertainties are associated with the sediment's undrained shear strength and the cap thickness. An unfortunate combination of low shear strength and thick cap could cause slope failure (e.g. translational sliding of the sediment and/or bearing capacity failure (e.g. punching through). Failure, particularly slope failure, can cause spreading of the contaminants in the fjord causing serious consequences. This paper presents an assessment of the probability of slope failure associated with the contaminated sediment before and after the cap placement. Probability of bearing capacity failure is considered to have more local effect and is also discussed briefly. The study used the Monte Carlo method with random undrained shear strength and sediment thickness. The simulations show high slope failure probability when the seabed inclination was ≥ 1:50 combined with an average undrained shear strength ≤ 0.4 kPa. Based on the probabilistic analyses, a pilot field testing campaign was carried out (after this study) with 20-cm thickness cap in the "gentle" sloping area and 5-cm thickness in the "steep" areas to avoid causing a failure. The analyses were used to support evidence-based decision-making on the cap design and implementation for further field testing. [ABSTRACT FROM AUTHOR]

In order to investigate the impact of marine propeller wake fields on sediment siltation in shallow water channels, this study employs the unsteady RANS approach and the Volume of Fluid model. A full-scale numerical self-propulsion test was conducted on a 50,000 DWT oil tanker under the influence of a free surface. The research includes forecasting the effect of propeller wakes on sediment redeposition following the dredging of the approach channel to Jiaxing Port in the China Sea. Initially, uncertainty research was carried out on the full-scale ship and propeller system, and the credibility of the computational results was quantified. The simulated results based on the sediment transport numerical model were then compared and validated against actual data from monitoring stations. The self-propulsion performance and the velocity distribution of the propeller wake were examined under three different propeller speeds. Scenarios simulated included no ship navigation, daily single-ship navigation, and daily two-ship navigation, evaluating the siltation distribution within the channel over one month. The results demonstrate that ship propeller wakes positively influence the reduction of channel sedimentation, with the maximum monthly siltation reduction reaching 0.108 m during single-ship tidal navigation and 0.11 m during two-ship tidal navigation. [ABSTRACT FROM AUTHOR]

Background and aims: Nitrogen (N) mineralization and immobilization are two important N biogeochemical processes in estuarine and coastal sediments. However, the changes of those two processes in sediment following Spartina alterniflora (S. alterniflora) invasions into mangrove wetlands under aerobic and anaerobic conditions remain limited. Methods: We used a 15N stable isotope dilution technique to investigate sediment gross N mineralization (GNM) and NH4+ immobilization (GAI) under aerobic and anaerobic conditions in mangrove communities, mangrove communities mixed with S. alterniflora, and pure S. alterniflora communities in the Zhangjiang Estuary, China. Results: GNM and GAI rates varied spatially and seasonally. Summer N mineralization and immobilization rates under aerobic and anaerobic conditions were both significantly higher than those in winter, and the high rates were observed mainly in mangrove sediments and decreased with S. alterniflora invasion. GNM rates in aerobic conditions were significantly higher than those in anaerobic conditions, while GAI rates in aerobic conditions were less than those in anaerobic conditions. GNM and GAI rates were related closely to temperature, water content and organic matter. S. alterniflora invasion can weaken GNM and GAI rates by reducing organic matter accumulation, and S. alterniflora invasion could have reduced sediment N mineralization (2.10 × 103 t N yr−1) and immobilization (1.46 × 103 t N yr−1) in mangrove wetlands of China from 1980 to 2020. Conclusions: Our results highlight the importance of S. alterniflora invasion and hydrological conditions in controlling N mineralization and immobilization processes in mangrove sediments and are essential for the evaluation of N-balance in this N-limited ecosystem. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the flux of CH4 gas in the sediments of mangrove and seagrass ecosystems in Tanjung Tiram, Ambon Bay. The research was conducted in May – June 2024. The mangrove and seagrass ecosystems at this location get inputs from the organic matter originating from litter production and domestic waste from people living around the ecosystem area. In each ecosystem, three observation points were determined based on the sediment type: sand, muddy sand, and sandy mud, each coded M1, M2, and M3 for mangrove and L1, L2, and L3 for seagrass ecosystems. Gas sampling was carried out by placing cylinder covers on each sediment type. Furthermore, 10ml of gas was taken seven times with an interval of 30s, namely 0, 30, 60, 90, 120, 150, and 180s. The gas was put into a vial, and then the gas concentration was analyzed using chromatography (GC-MS), flux, and global warming potential. The single factor ANOVA and t-test (α = 0.05) were carried out to determine the difference in each sediment's average gas concentration. The results showed that the average comparison of CH4 gas concentrations in mangrove and seagrass ecosystems (M:L) showed no significant difference with P = 0.0637 (P> 0.05). The average CH4 flux in mangrove sediments was 0.1476mg/ m ² / hour, more significant than that in seagrass sediments, which was 0.1424mg/ m 2 / hour. M1 and L1 recorded the most significant CH4 fluxes in each ecosystem sediment, which were 0.1794 and 0.1509mg/ m 2 / hour. Meanwhile, the most minor flux was found in M2, which was 0.1005mg/ m ² / hour, and L3, which was 0.1320mg/ m ² / hour. The GWP of mangrove sediments was 3.6907mg CO2e /m² / hour, more significant than the seagrass GWP of 3.5590mg CO2e/ m ² / hour. The flux of CH4 gas was significantly affected by the sediment type, especially in sandy sediments. It is related to the level of porosity of sediment, which acts as a circulating space for methane gas produced from the degradation process of organic matter contained in each type of sediment. The flux and GWP values of methane gas released from sediments of mangrove and seagrass ecosystems should not be ignored in climate change mitigation, especially in areas with very low-density levels and high organic waste inputs. [ABSTRACT FROM AUTHOR]

Microplastics (MP) are one of the most significant pollutants in the marine environment. For the first time along the Alexandria coast from the eastern to the western side, Egypt, the study recorded MP in surface water and sediment (bed, and beach) from five stations covering two seasons in 2020. In addition, the study evaluated the potential ecological risk of MP using the polymer hazard index (PHI) and potential ecological risk index (PERI). Results indicated the fluctuation of MP abundance in water samples (1.3MP/ l). The wet season showed a higher abundance of MP. The MP content of beach sediment (446.9MP/ Kg) was more than that of the bed sediment (170.6MP/ Kg). Most MP particles were fiber-shaped, blue, and transparent, with sizes larger than 1mm. The chemical identification showed that polyamide and rayon were the most common polymers in most samples. The ecological risk indices indicate that Sidi Bishir area is classified as V level of risk, and the bed and beach sediments are subjected to extreme danger of MP pollution. The study recommends a deeper interest in the chemical analysis of polymers and standardizing the sampling and identification methods. Clear management strategies to control MP aquatic pollution with MP should be addressed. [ABSTRACT FROM AUTHOR]

The assessment of the radioactivity level and associated risks has been performed for the mangrove plants. Twenty-five mangrove samples were collected from the Abu Fasi, Marsa Shaab, and Sowmaa mangroves in the Marsa Shaab area of the Egyptian Red Sea coast. The activity concentration values of the nuclides 226Ra, 232Th, and 40K for samples collected from sediments associated with the mangrove environments were measured. The specific activities in mangrove samples obtained in the Abu Fasi region varied as follows: 15± 0.8 Bq.kg-1 to 42± 2.1 Bq.kg-1 for 226Ra, 10± 0.5 Bq.kg-1 to 39± 1.9 Bq.kg-1 for 232Th, and 103± 5.2 Bq.kg-1 to 340± 17 Bq.kg-1 for 40K. Additionally, the activity concentrations of the mangrove samples collected from Marsa Shaab and Sowmaa mangrove areas ranged as follows: 28± 1.4 to 56± 2.8 Bq.kg-1 for 226Ra, 18± 0.9 to 58± 2.9 Bq.kg1 for 232Th, and 164± 8.2 to 531± 26.5 Bq.kg-1 for 40K. Moreover, the mangrove samples collected from the Sharm el El Madfea area showed activity concentrations ranging as follows: 25± 1.3 to 52± 2.6 Bq.kg-1, 15± 0.8 to 61± 3 Bq.kg-1, and 250± 9.1 to 583± 29.2 Bq.kg-1 for 226Ra, 232Th, and 40K, respectively. The highest average values were observed in samples collected from Marsa Shaab and Sowmaa mangroves for the 226Ra and 232Th. However, the highest average value for 40K was measured in samples collected from the Sharm El Madfea area. The radiation hazard calculations for the collected mangrove samples showed much lower values than the criterion and worldwide recommended limits. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are produced by incomplete combustion of biomass and fossil fuel, yet PAHs have been rarely analyzed in coastal sediment cores as a tracer for human activities before industrialization. The aim of this study was to assess if the historical trend of PAHs can be related to past human activities. To this end, we have determined the concentrations of PAHs in a 9 m-long sediment core from Osaka Bay, which records history of the last 2400 years. The concentration of PAHs before the beginning of the 17th century CE, the beginning of the peaceful Edo period, was consistently low (<100 ng g−1) and mainly comprised of smoke-derived PAHs reflecting the natural background. A relative higher abundance of 4−6 ring PAHs from the early 17th century CE and a higher PAH concentration from the early 18th century CE until approximately 1800 CE agreed with a population increase, Cu smelting activities and increasing combustion of charcoal. The constant PAH concentration until the late 19th century CE overlapped with a decline in the population in the Osaka area. An increasing PAH concentration from the late 19th century CE marked the beginning of industrialization in the Modern age. The peak in PAH concentration in 1945 CE was likely caused by burning of wooden structures due to air raids on Osaka City. A second peak around 1980 CE indicated the introduction of cleaner energies. We conclude that PAHs in coastal sediment cores can be used to reconstruct past human activities. [ABSTRACT FROM AUTHOR]

This study reconstructs recent changes (1880–2017) in sea-ice conditions, using biomarkers (IP 25 and phytoplankton sterols) from three sediment cores located in a transect across Belgica Trough, on the Northeast Greenland continental shelf. These results are evaluated using instrumental and historical data from the same region and time period. Over the entire study period, IP 25 concentrations are highest at the inner shelf (site 90R) and decrease towards the mid-shelf (site 109R), with lowest values found at the outer shelf (site 134R). The PIP 25 index yields the highest sea-ice cover at sites 109R and 90R and the lowest at 134R, in agreement with observational records. A decline in sea-ice concentration, identified visually and using change-point analysis, occurs from 1971 in the observational sea-ice data at sites 90R and 109R. A change in sea-ice concentration occurs in 1984 at site 134R. Sea-ice conditions in these years aligns with an increase in sterol biomarkers and IP 25 at all three sites and a decline in the PIP 25 index at sites 90R and 134R. The outcomes of this study support the reliability of biomarkers for sea-ice reconstructions in this region. [ABSTRACT FROM AUTHOR]

Seismic refraction tomography is a commonly used technique to characterise rock glaciers, as the boundary between unfrozen and ice-bearing layers represents a strong impedance contrast. In several rock glaciers, we observed a reversed polarity of the waves refracted by an extended ice-bearing layer compared to direct-wave arrivals. This phase change may be related to the presence of a thin low-velocity layer (LVL), such as fine- to coarse-grained sediments, above a thicker ice-rich layer. Our results are confirmed by the modelling and analysis of synthetic seismograms to demonstrate that the presence of a low-velocity layer can produce a polarity reversal on the seismic gather. [ABSTRACT FROM AUTHOR]

Geotechnical sediment properties, morphological change, and hydrodynamics were measured as part of the During Nearshore Event Experiment (DUNEX) in October 2021 at the sandy Atlantic side beach in Duck, North Carolina. In this study, direct relationships were explored between in situ soil properties and direct erodibility measurements in the context of morphological change. Moisture content, grain size, total density, relative density, void ratio, and sediment strength were compared to bed-level change using ground-based LiDAR and erodibility parameters from laboratory jet erosion tests (JETs) conducted along a cross-shore transect stretching from the dune toe to the lower intertidal zone. Directly relating changes in sediment properties to changes in morphology from LiDAR proved inconclusive due to the complex interactions between sediments, hydrodynamics, and morphology, even on a local scale, but initial observations and possibly impacting factors were discussed. Void ratio and total unit weight correlated well with the detachment rate coefficient from JETs, with denser sediments testing as less erodible. In situ sediment strength measurements related—as expected—to total unit weight, void ratio, and water content, with increases in firmness factor associated with increases in total unit weight, void ratio, and water content. These strength measurements were also found to have a correlation with the detachment coefficient from the JET, with stronger/firmer sediments being less erodible than weaker ones. [ABSTRACT FROM AUTHOR]

To better understand stream‐fish sensitivity to fine sediment, we documented assemblage‐wide responses by selected traits along a sedimentation gradient. We then discuss the management implications of these 'dose–response' relations in the contexts of biotic assessments and conservation of sediment‐sensitive species. We identified a spatial gradient in sediment deposition among streams within the upper Piedmont of the Roanoke River basin in North Carolina and Virginia. We assessed fine‐sediment sensitivity of 81 species based on eight species traits stratified by four attributes: food preference, feeding location, spawning substrate and spawning behaviour. We then ranked each trait and scored each species with respect to its sediment sensitivity. Using data from electrofishing surveys during 2018–2019, we calculated proportional abundances of traits observed at 30 sites throughout the study area and grouped species by their aggregate sensitivity scores. We assessed relations between embeddedness and silt cover and occurrences of species and traits using a combination of regression and ordination approaches. All traits tested responded to embeddedness or silt cover, or both. Feeding traits exhibited the strongest responses to embeddedness, while reproductive traits exhibited the strongest responses to silt cover. Our findings indicate that negative responses of the probability of presence for high‐sensitivity traits to embeddedness and silt cover were linear, with no apparent thresholds. Additionally, proportional abundances of species with multiple high‐sensitivity traits were inversely related to embeddedness and silt cover. Overall, our findings regarding population‐level responses to sedimentation were consistent with our findings for trait‐specific responses. Our analysis of species sensitivity to fine sediment corroborated the patterns we saw in our trait‐specific analyses, indicating that population responses to sedimentation can be predicted from combinations of species traits. The 'dose–response' relations we documented may be applicable to managing sediment impacts on fishes, especially in the contexts of biotic assessments and conservation of sediment‐sensitive species. [ABSTRACT FROM AUTHOR]

The in situ acoustic measurement of seafloor sediment is an important technical means to obtain the acoustic parameters of seafloor. The time‐of‐flight method is commonly used to calculate the sound speed in seafloor sediment. Accurate identification of signal feature points is essential for determining travel time or travel time difference of acoustic signals. However, the precise identification of feature points, such as the take‐off point of the first wave of a sound wave signal, is challenging. The conventional manual identification method is inefficient and prone to errors. The development of a feature point auto‐identification method is imperative for accurately calculating the travel time of acoustic signals. In this study, we employed the cross‐correlation method, the level threshold method and the short window‐long window energy ratio method to extract the acoustic travel time differences and calculate the sound speeds in seawater and in seafloor sediment. We then analysed the effectiveness of these calculated results. The sound speeds in seawater obtained through the aforementioned methods were compared with the sound speeds measured using a sound velocity profiler. The comparison revealed that these processing methods exhibit a high level of accuracy. The sound speed results in sediments show that the programme‐based auto‐identification methods significantly reduce the standard deviation compared to the manual identification method. This study successfully assessed the processing accuracy of different methods and expanded the processing methods for in situ acoustic signals of seafloor sediments. [ABSTRACT FROM AUTHOR]

The potential for polycyclic aromatic hydrocarbon (PAH)‐related effects in benthic organisms is commonly estimated from organic carbon‐normalized sediment concentrations based on equilibrium partitioning (EqP). Although this approach is useful for screening purposes, it may overestimate PAH bioavailability by orders of magnitude in some sediments, leading to inflated exposure estimates and potentially unnecessary remediation costs. Recently, passive samplers have been shown to provide an accurate assessment of the freely dissolved concentrations of PAHs, and thus their bioavailability and possible biological effects, in sediment porewater and overlying surface water. We used polyethylene passive sampling devices (PEDs) to measure freely dissolved porewater and water column PAH concentrations at 55 Great Lakes (USA/Canada) tributary locations. The potential for PAH‐related biological effects using PED concentrations were estimated with multiple approaches by applying EqP, water quality guidelines, and pathway‐based biological activity based on in vitro bioassay results from ToxCast. Results based on the PED‐based exposure estimates were compared with EqP‐derived exposure estimates for concurrently collected sediment samples. The results indicate a potential overestimation of bioavailable PAH concentrations by up to 960‐fold using the EqP‐based method compared with measurements using PEDs. Even so, PED‐based exposure estimates indicate a high potential for PAH‐related biological effects at 14 locations. Our findings provide an updated, weight‐of‐evidence–based site prioritization to help guide possible future monitoring and mitigation efforts. Environ Toxicol Chem 2024;43:1509–1523. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

There is a growing need to understand the potential ecological impacts of contaminants in offshore oil and gas infrastructure, especially if that infrastructure is to be left in situ as a decommissioning option. Naturally occurring radioactive material (NORM) is one type of contaminant found in solid deposits on internal surfaces of infrastructure that poses potential ecological harm if released into the marine environment. Microbes are important components of marine sediment ecosystems because they provide ecosystem services, yet the impacts of NORM contamination to these communities are not well understood. The present study aimed to investigate the response of benthic microbial communities to NORM‐contaminated scale, collected from an offshore oil and gas system, via controlled laboratory microcosm studies. Changes to microbial communities in natural sediment and sediments spiked with NORM at radium‐226 activity concentrations ranging from 9.5 to 59.8 Bq/kg (in partial equilibria with progeny) over 7 and 28 days were investigated using high‐throughput sequencing of environmental DNA extracted from experimental sediments. There were no significant differences in microbial community composition between control and scale‐spiked sediments over 7 and 28 days. However, we observed a greater presence of Firmicutes in the scale‐mixed treatment and Chloroflexi in the scale‐surface treatments after 28 days. This could suggest selection for species with contaminant tolerance or potential resilience to radiation and metal toxicity. Further research is needed to explore microbial tolerance mechanisms and their potential as indicators of effects of radionuclide‐contaminated sediments. The present study demonstrated that microcosm studies can provide valuable insights about the potential impacts of contamination from oil and gas infrastructure to sediment microbial communities. Environ Toxicol Chem 2024;43:1648–1661. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

In recent decades, interest in the measurement of 10Be has increased due to its relevance in various fields of science. Trace amounts of 10Be produced from meteoric sources require sensitive accelerator mass spectrometry (AMS) measurements and robust sample preparation. The extraction, separation, and preparation of the appropriate oxide form for AMS require extensive and careful laboratory processing and certified reference materials to validate the chemical performance of the protocols used and the calibration of the AMS system in the measurement. In this work, the meteoric 10Be concentrations in two certified reference materials are characterized to establish their suitability as internal control standards for laboratory chemical preparation and AMS measurements of this radioisotope in our laboratory and the whole AMS community. [ABSTRACT FROM AUTHOR]

The promotion of drip irrigation technology has been severely constrained by the emitter clogging caused by sediment deposition when using high-sediment loaded water. To fill this gap, a novel solution to the emitter clogging issue has been developed by allowing fine sediment particles to drain as much through the emitter as possible. The sediment deposition and discharge ratio, the sediment discharge rate, and the control threshold for particle size were used to determine the sediment discharge capacity (SDC) of the emitter. The result shows that almost all (> 99%) the fine-grained sediment (< 100 µm) can be discharged from the flow path of eight emitters, which varied greatly in different emitters. Specifically, pressure-compensating emitters (PCE) had higher SDC than non-pressure-compensating emitters (NPCE), with relative average flow rate increased by 16.9–33.0%. Meanwhile, the emitter flow path structure significantly affects SDC. The side wall of the flow path could be changed from a toothed structure to a swirl wash wall optimized structure, which would significantly improve the SDC. Furthermore, the SDC of NPCE was primarily affected by the flow path length (L) and the ratio of the cross-sectional area to the length ( A / L ). Lastly, stronger emitter SDC closely related to both smaller particle size and concentration of water source. This study presents a fresh idea of sediment treatment for drip irrigation systems with high sediment content water and may contribute to the design of emitters with high sediment discharge capacity, and the effective management and filtration treatment of high-sediment loaded water. [ABSTRACT FROM AUTHOR]

Recent studies show that near-bed turbulence may be better scaled using a mixed velocity scale u*U , where u* is the shear velocity and U denotes the characteristic bulk flow velocity. This implies that the classical scaling consideration for sediment transport rates could be improved by redefining the Shields number based on the mixed velocity scale. To investigate this potential improvement, a series of analyses was performed with laboratory data from 25 sources of sediment discharge studies. The data were carefully selected by minimizing effects of some factors including sidewall, particle gradation, particle density, and fluid viscosity. The findings indicate that the relationship between sediment discharges and flow conditions can be enhanced significantly when the analysis is carried out based on the redefined Shields number. The new relationship does not depend on the type of bedforms, and therefore facilitates the prediction of sediment discharge. Finally, by comparing with previous studies, it shows that the proposed formula markedly improves the prediction of bed-material sediment discharges. [ABSTRACT FROM AUTHOR]

Microplastic occurrence in the aquatic ecosystem has become of great concern worldwide because of its persistence, durability, and toxicity. Microplastics are found ubiquitous in freshwater environments, including rivers. Thus, our study assesses microplastic pollution in water, sediment, and fish of the Kahayan River, Indonesia. We first evaluated microplastics' occurrence, abundance, and characteristics in Central Kalimantan, Indonesia. The average abundance of microplastic in water was 2.92 ± 2.62 items/L, while in sediment was 6.93 ± 3.15 items/Kg dry weight. We found 53 out of 90 fish (58.89%) had microplastics in their digestive tracts with an average abundance of 2.03 ± 3.416 items/Ind. The predominant characteristics in water were fragment and fibre and size of 150-<300 µm. Microplastics present in the sediment and the digestive tract of fish have similar dominant fibre. In terms of size, sediments and fish were dominated by 150-<300 µm, 1000–5000 µm, and 500-<1000 µm respectively with different order of proportions. The infrared spectroscopic analysis confirmed the most common polymer type to be polyvinyl chloride in water and sediment, while polyethylene was predominant in fish. Our study provides the current status of microplastic contamination for further evaluation and management of the Kahayan River, Indonesia. [ABSTRACT FROM AUTHOR]

Tailwater recovery system (TWR) sediment quality in Mississippi, USA, was evaluated seasonally within the storage reservoir and drainage ditch system from 2016 to 2019 for pesticide contamination, effects and bioavailability to Hyalella azteca (Saussure). Sediment bioassays (28-day) measured H. azteca survival and growth and tissue residue risks from sediment pesticide exposure. Sediment pesticide contamination comprised six current-use herbicides, three current-use insecticides, three legacy insecticides and one metabolite (p,p'-DDE). Sediment clomazone, bifenthrin and ΣDDT concentrations were greatest in drainage ditch sites during summer and fall. H. azteca tissue pesticide residues comprised three current-use herbicides and insecticides, as well as two legacy insecticides. Tissue residue clomazone, Ζ-cypermethrin and ΣDDT concentrations were greatest in drainage ditch sites during fall and winter. H. azteca survival and growth varied seasonally and spatially with lowest survival during fall and winter and lowest survival in the storage reservoir relative to drainage ditch sites during winter. Growth decreased during winter and spring with lowest growth in drainage ditches relative to the storage reservoir during spring. Patterns of associated survival and growth with tissue pesticide residues indicate increased risk during fall in TWR and where system water flows mobilise sediment pesticides increasing the risk of ecological impairment. [ABSTRACT FROM AUTHOR]

Astronomical cycles reliably identified in the sedimentary record are useful for their paleoclimatic interpretations and construction of astrochronology. However, the depositional response and burial-diagenesis processes play a crucial role in distorting the time scales of geological records and introducing noise to orbital signals. How to evaluate the response of varied depositional environments to astronomical forcing remains a challenge. We developed the random-length average orbital power ratio calculation (RAOPR) method to evaluate average orbital power ratio distributions within a specific time interval and applied this new method to the theoretical eccentricity-tilt-precession (ETP) plus noise series and an astronomically tuned Cretaceous terrestrial stratigraphic record spanning ~24 m.y. (92-65 Ma, except for an ~3.8 m.y. gap from ca. 79.9 Ma to 76.1 Ma). Using the merged ETP plus noise series, we observed different orbital power ratio distributions for different background noise intervals. For the Cretaceous terrestrial Songliao Basin, we retrieved long-term orbital variations and used the RAOPR method to calculate the average orbital power ratios in different depositional environment intervals. Our results suggest that unusually high precession power in the Yaojia Formation resulted, in part, from autogenic processes, and unusually low precession power in the Nenjiang Formation can be attributed to marine incursion events. The eccentricity power of the meandering river facies was much higher than observed in other facies intervals. Conversely, the lowest precession power in the meandering facies may be attributed, in part, to the erosion "clipping" effect, which decreases the high-frequency precession band power and increases low-frequency eccentricity band power. [ABSTRACT FROM AUTHOR]

The Mesoarchean to Neoarchean period (ca. 3.0-2.5 Ga) is the most important stage during the emergence and evolution of plate tectonics. However, plate subduction at this time may have been less stable and perhaps more susceptible to the lubrication effect of sediments than the modern counterpart. Such predictions have not yet been verified by field-based investigations. In this work, we identified two types of rock units (i.e., sanukitoids and associated adakitic suites, exposed in the Eastern Hebei Complex of the North China Craton) and illustrated their petrogenesis and tectonic context through field, geochronologic, geochemical, and isotopic investigations. Laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb analyses suggest that the two magmatic suites formed within a relatively short time span of ca. 2596-2544 Ma and ca. 2559-2533 Ma, respectively. The sanukitoids are composed of meta-andesites and diorite porphyrites and characterized by relatively high MgO (3.94-5.62 wt%), Mg# (50-61), Cr (73-343 ppm), and Ni (37-111 ppm) values. The adakitic rocks are composed of granodioritegranite gneisses and have relatively high Sr (316-1001 ppm) and low Y (7-13 ppm) and Yb (0.83-1.37 ppm) contents, and relatively high Sr/Y (36-89) and La/Yb (16-45) ratios. Rocks from both suites exhibit depletions of Nb, Ta, and Ti and have similar Sr-Nd-Hf-Zn isotopes: variable (87Sr/86Sr)i (0.7002-0.7053), weakly positive eNd(t) (+0.3 to +1.7) and eHf(t) (+1.8 to +6.8), and slightly heavy d66Zn (0.30‰-0.36‰). These geochemical characteristics indicate that the sanukitoids were derived from the melting of subducted sediments followed by melt-mantle interaction, whereas the adakitic rocks were produced by direct partial melting of subducted plate (including tonalite-trondjhemite-granodiorite melts) under a garnet stability field with minor sediments. Such distinct magmatic rock associations, together with the coeval charnockites and tholeiites with diverse compositions in the adjacent area, can be best explained by a slab breakoff model. Further, events associated with slab breakoff are likely to represent a transition of a quasi-plate tectonic regime, characterized by multiple, continuous, and stagnant attempts to start the modern-style subduction on Earth. In addition, the emergence of sanukitoids and associated magmas symbolized the onset of supracrustal recycling into the mantle. Combined with the Nd-Hf-Zn isotopes of diverse magmatic rocks in the North China Craton that are comparable to other Precambrian magmatic rock suites worldwide, we suggest that supracrustal recycling symbolized the onset of plate tectonics since ca. 3.0 Ga, and by inference played a key role in the development of subduction-driven plate tectonics in addition to Earth's secular cooling. [ABSTRACT FROM AUTHOR]

Sediment Bypass Tunnels (SBTs) are proven to be an effective measure to reduce or even stop reservoir sedimentation by bypassing sediment laden flows around reservoir dams to the downstream river reach. They are mostly used in Switzerland, Japan, and Taiwan. However, hydraulic and sedimentological operating conditions and the resistance of the invert materials against hydroabrasive erosion affect their cost-effectiveness. Hydroabrasion is a pressing issue at SBTs, other hydraulic structures and steep bedrock rivers exposed to high sediment transport rates under supercritical flow conditions. The present study was therefore conducted to address this issue by aiming at improving knowledge on abrasion mechanics and calibrating a mechanistic saltation abrasion model enhanced by Demiral-Yüzügüllü (2021). To this end, the abrasion resistance of fourteen different invert materials installed at Solis, Pfaffensprung and Runcahez SBTs in Switzerland was quantified by annual 3D laser scanning and the hydraulic conditions and sediment transport rates were regularly monitored between 2017 and 2021. The analysis of invert scans and hydraulic conditions revealed that Prandtl's first and second kinds of secondary currents occurring in the bends and straight sections of the SBTs, respectively, and the observed abrasion patterns were strongly interrelated. The tested potassium aluminate cement and steel fibre concretes, granite, cast basalt and steel plates had better abrasion resistance against impact of sediment-laden flows compared to other materials. Sediment mineralogical composition i.e., bulk hardness relative to the invert material properties significantly affected hydroabrasion. The enhanced abrasion prediction model was calibrated with the present data and a quasi-constant abrasion coefficient of k v = (4.8 ± 2.2) × 104 was obtained. The enhanced model is well-suited for both laboratory and field scales. The present findings will contribute to the sustainable utilization and operational safety of hydraulic structures, optimization of SBT and reservoir operations regarding bypassing efficiency and reservoir lifetime and modelling of bedrock river erosion. [ABSTRACT FROM AUTHOR]

The effect of microplastics on the environment is currently one of the hotspots in environmental research. Biodegradable plastics will inevitably replace most of the traditional plastics. However, there are few reports on the effect of their natural degradation process on freshwater sediment. This study constructed a water column reactor indoors to simulate the environment of shallow freshwater lake, and investigated the effects of two commonly used biodegradable plastics, PLA and PBAT, on sediment at different time periods (90 and 365 days). The analysis of physicochemical parameters showed that the two degradable plastics significantly increased the total organic carbon (TOC) and total nitrogen (TN) concentrations of interstitial water in the short term (90 days) (P<0.05). PLA and PBAT significantly promoted the α diversity of bacterial communities over a long period of time (365 days) and increased the relative abundance of Proteobacteria. The number of denitrifying nirS genes in PLA and PBAT during the 90-day period was (2.33±0.33)x108 copies/g sediment and (2.16±0.09)x108 copies/g sediment respectively and the number of denitrifying nirK gene was (1.24±0.18)x107 copies/g sediment and (1.37±0.23)x107 copies/g sediment respectively, both of them were significantly higher than the control group (P<0.05). However, within 365 days, the number of nirS and nirK genes and anammox bacteria in degradable plastic groups were all significantly lower than the control group (P<0.05). Besides, the number these two kinds of bacteria in PBAT group was significantly lower than those of PLA group. Redundancy analysis revealed that the number of nirS and nirK genes was positively correlated with NH4+-N, TN, and TOC, and negatively correlated with total phosphorus. The correlation between anammox bacteria and environmental factors was completely opposite to that of denitrifying genes. This study preliminarily investigates the effects of different biodegradable plastics on sediment at different time periods, which may play an important role in further understanding the environmental effects and effect mechanisms of biodegradable plastics. [ABSTRACT FROM AUTHOR]