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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]

Mangrove forests are crucial wetland ecosystems located in tropical and subtropical intertidal zones, but they have become extensively degraded. As a viable ecological restoration strategy, the cultivation of native mangrove vegetation in these degraded areas has gained considerable attention. Mangroves' unique environmental conditions make them suitable habitats for diverse microbial communities, including Archaea - one of the main microbial communities in mangrove sediments - which plays a pivotal role in biogeochemical cycles.However, little is known about the dynamics of archaeal communities during mangrove restoration through phytoremediation. In this study, we investigated the physicochemical properties of sediment profiles from natural and artificially restored mangrove ecosystems in Tieshan Bay. We utilized quantitative polymerase chain reaction (qPCR) and 16S rRNA gene sequencing techniques to explore differences in abundance, community structure, and composition of archaeal communities between sediment profiles in natural and artificially restored mangrove ecosystems. We also examined correlations between archaeal communities and environmental factors. Our results revealed that Crenarchaeota, Thermoplasmatota, Asgardarchaeota, Nanoarchaeota, and Euryarchaeota were the predominant archaeal phyla, with significant variation in sediment composition observed for Crenarchaeota and Thermoplasmatota in different depths. We also found significant differences in archaeal abundance and community composition between natural and restored mangrove sediments. Furthermore, C/N ratio and pH emerged as primary drivers of archaeal communities in wet and dry season sediments, respectively. Additionally, the study revealed seasonal disparities in seasonal differences in the relative abundance of certain archaeal groups (such as Asgardarchaeota, Nanoarchaeota). Network analysis demonstrated stronger interconnections among archaeal communities in sediments from natural mangroves than from artificially restored ones. These findings enhance our knowledge of archaeal community succession patterns in mangrove restoration, as well as provide fresh perspectives for the sustainable management of mangrove ecosystems. [ABSTRACT FROM AUTHOR]

The observation on mangrove sediment variables along Bhayander creek of district Thane within Maharashtra coast was carried to analyze the deterioration level of mangrove sediment due to water pollution. Research was conducted during October 2016 to September 2017. Different sediment variables like sand, silt, clay, organic carbon, organic matter, total nitrogen and available phosphate were determined. Texture of sand, silt and clay was widely oscillated during the said period. Organic matter, Organic carbon, available phosphate, and total nitrogen were found significantly different seasonally throughout the study period. Observations showed noteworthy uncertainties in all the sediment variables found distinct within their limits. Study proposes the measures to mitigate contamination of Bhayander creek and anthropogenic restrictions. [ABSTRACT FROM AUTHOR]

Microplastics are plastic fragments measuring < 5 mm, microplastics that enter the water can damage the growth of coral reefs. The aim of this research is to obtain accurate data on the distribution of microplastics, as an initial step in conservation and mitigation of the impact of plastic waste pollution in the Ujong Pancu area. Sediment samples were taken using coring method. Microplastic identification was carried out at the Marine Chemistry Laboratory, Faculty of Maritime Affairs and Fisheries, Syiah Kuala University using a binocular microscope with zig-zag pattern identification. The results of this study are that there are three types of microplastic found in Ujong Pancu waters, namely fiber, film, and fragment types. The average abundance of microplastics in Ujong Pancu Waters ranges from 32-68 particles/kg. The highest average abundance of microplastics is in the northwestern part of Pulau Tuan and the lowest is in Lhok Mata Ie Beach. The highest type of microplastic found was film and the lowest type of microplastic found was fiber. The condition of coral reefs in Ujong Pancu waters is in the moderate category. The relationship between microplastic abundance and the percentage of live coral cover and environmental parameters was 85.01%. [ABSTRACT FROM AUTHOR]

Fine-grained cohesive sediments in estuaries play a critical role in sediment transport and biogeochemical cycles in estuaries. Due to the convergence of marine saltwater and freshwater runoff, combined with periodic tidal cycles, fine-grained sediments exhibit intricate flocculation processes that are challenging to simulate. A size-resolved flocculation module using a bin-based scheme aids in modeling these processes but is hindered by high computational costs. In this study, we develop a new spectrum-based scheme based on the spectral shape of floc size distribution from the original bin-based scheme to expedite modeling execution. This new scheme is implemented in the Stony Brook Parallel Ocean Model (sbPOM) and applied to simulate fine-grained sediment transport in the Hudson River estuary. The effectiveness of this spectrum-based scheme is assessed by comparing its simulations with observations and results from the original bin-based scheme. The findings indicate that the new scheme can simulate the evolution of suspended sediment concentration well at a specific point by comparisons with in-situ observations. Specifically, the results of the 50 paired experiments show an average percentage difference of 1.86% and an average speedup ratio of 4.51 times compared to the original bin-based scheme. In summary, the new spectrum-based scheme offers significant acceleration benefits for the size-resolved flocculation module and has the potential for widespread application in simulating fine-grained sediments in estuaries. [ABSTRACT FROM AUTHOR]

This study aims to investigate the hydrodynamic-morphological interactions on a microtidal intermediate-dissipative beach under low to moderate wave energy conditions using field measurements during two climatic seasons. The separate contributions of currents, sea-swell waves, and infragravity waves to high- and low-frequency sediment fluxes were analyzed. The infragravity wave energy was more relevant near the swash zone than in other areas. Although the currents are the primary suspended sediment transport mechanism, the results suggest that the waves are an important driver of sediment suspension from the seabed. The results indicate that Sea-Swell (SS) waves and cross-shore currents are the prevailing hydrodynamic factors in nearshore sediment transport, and the cross-shore suspended sediment transport rates are higher than those in alongshore transport. The submerged bar intensified during the wet season (1–4 November 2018) when the wave height intensities were lower, contrary to the dry season (24–25 March 2018). Significant accretion nearshore was identified (in the subaerial beach) during the wet season when the suspended sediments were greater, the SS-wave heights nearshore were lower, and sediment flux was directed onshore. A notorious erosion was distinguished during the dry season. The most representative volume changes occurred during the dry season (with high erosion), which is attributed to the high SS-wave energy. [ABSTRACT FROM AUTHOR]

Beach–dune systems are highly dynamic features of the coastal system, the evolution of which is influenced by several processes that occur at very different spatial and temporal scales. To mitigate shoreline retreat that threatens extensive coastal areas worldwide, coastal erosion mitigation measures are implemented, aiming to make coastal areas resilient to the effects induced by coastal erosion and the anticipated climate change related to storms, flood events and sea level rise. Numerical modelling can support planned and sustainable coastal management from a medium-to-long-term perspective (decades). This research focuses on presenting contributions regarding the numerical modelling of subaerial beach dynamics (berm width and dune systems interactions) from a medium-term perspective. The method applied is based on a combination of the results of two simplified numerical models (the LTC and CS-Model). The results demonstrate the potential of the proposed combined model for medium-term projections, allowing for the interpretation of beach–dune dynamics and the evaluation of the importance of longshore and cross-shore sediment transport processes. [ABSTRACT FROM AUTHOR]

Sediments are natural reservoirs of organic carbon assisting in maintenance of natural carbon inventory. The present work was carried out with aims to assess the various labile (employing acid digestion method) and biochemical carbon fractions in sediments of Hirakud reservoir and study the impact of spatial variations on it. The results favor a distinct spatial influence on the distribution and concentration of various carbon fractions in sediments (p < 0.05). The average concentrations of very labile (2.09%) and recalcitrant (1.25%) fractions of total organic carbon dominated the sediments while the labile and less labile fractions shared 0.39 and 0.63% respectively. Similarly, the carbohydrate carbon (0.82 mg/g) and protein carbon (0.78 mg/g) conquered the biopolymeric carbon (BPC) with the lipid carbon being 0.67 mg/g only. While the available K and P ranged between 3.81 and 17.02, and between 6.31 and 27.57 kg/ha respectively, total nitrogen varied from 198.06 to 462.15 kg/ha. Significant spatial variations were observed concerning long-term carbon storage and productivity (eutrophic condition, BPC > 3 mg/g). The reservoir sites were mesotrophic to eutrophic in nature while the downstream displayed oligotrophic condition. Organic sediment index (OSI) value suggests that the reservoir sediment was under practically uncontaminated to moderately contaminated condition (OSI < 0.20). The principal component analysis also suggests that the carbon accumulation is primarily governed by the recalcitrant carbon fraction. Thus, it can be concluded that carbon fractions regulate the sediment quality by influencing its carbon storage, production capacity, and is affected by anthropogenic pressure along a spatial scale. [ABSTRACT FROM AUTHOR]

Sedimentary records of Ri-Yue Tang (Sun Moon Lake), which is the largest lake in Taiwan, provide valuable hydro-environmental information during the past 15,000 years. From the viewpoint of hydro-geomorphological conditions, the interval is roughly divided into four stages: (i) high water level with large artificial water inflow (1934 AD–present), (ii) low water level with a comparatively large catchment area (1919 AD–ca. 2800 years BP), (iii) frequent high water level with a small catchment area (ca. 2800–ca. 13,500 years BP), and (iv) low water level with a comparatively large catchment area (ca. 13,500–15,000 years BP). The changes in the conditions are mainly shown in the physical properties. A small mineral grain size and large grain density suggest enough water with high water level while large grain size and small density imply low water level and limited water discharge. Dam construction (1919–1934 AD) for more water supplies to the newly established power station greatly influences the hydro-geomorphological and environmental conditions in the Ri-Yue Tan lake-catchment system. Additional artificial water inflow with mineral material through the waterway from the Wujie Reservoir has transported more sediments (roughly twice) after the dam construction. The increase in water level due to the dam construction caused water-area enlargement and catchment-area shrinkage, resulting in changes in material production (erosion), transportation, and sedimentation in the original system. The increase in water amount supplied from the reservoir is also printed in the physical properties (small mineral grain size and large grain density) and chemical properties (organic, HCl soluble, and bi-SiO2 contents) of lacustrine sediments. [ABSTRACT FROM AUTHOR]

Biota and associated sediment samples were collected from the Ibeno river catchment and analyzed using the standard methods for investigation of the sources and the distribution of heterocyclic compounds in the area. The lipid content values of the biota varied from 10-29% dry weight (dw; mean = 15.8 + 7.79) in Large crab (LC) and ranged from 5-10% dw (mean = 7.6 + 1.82) in small crab (SC). Also, it ranged from 6-10% dw (mean= 7.6 + 1.52) in small shrimp (SS) and varied from 7-40% dw (mean = 23.6 + 1.47) in large shrimp (LS). High TOC (4.5%) and TIC (2.53%) were found for the associated sediment, and this was because of the silty nature of the sediment, having high adsorption capacity for organic matter. The high extractible organic matter (EOM) value recorded for the associated sediment may be linked to petroleum hydrocarbon discharge into the environment by Exxon Mobil. The biota-sediment accumulation factor (BSAF) values ranged from 0.0029-0.0059 (mean = 0.0047 + 0.00128) for LC and 0.0059-0.0085 (mean = 0.00724+0.001276) for SC. On the other hand, the values ranged from 0.0060-0.0160 (mean = 0.0037 + 0.002787) and 0.0018-0.0084 (mean = 0.0096 + 0.004079) for LS and SS respectively. This low result reviews that the contaminant uptake from the associated sediment by the biota was negligible, hence, the consumers exposed to this biota might not have experienced any serious health risk associated with the consumption of heterocyclic aromatic hydrocarbons. The aromatic fractions from column chromatography would subsequently be subjected to gas chromatography mass spectrometry analysis to identify and quantify the individual heterocyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Biomimetic pumps can effectively enhance the hydrodynamics of plain river networks, improve the water environment, and facilitate the transport of sticky bottom sediment. In this paper, a biomimetic pump equipped with an NACA0012 wing profile was used as the research subject, and a commercial CFD package was employed to investigate the impact of the pump's installation height (the vertical distance from the hydrofoil's pivot to the riverbed) and operating frequency on the incipient motion of riverbed sediment. The results indicate that the lowest maximum near-bed velocity is obtained at an installation height of 3 times the chord length (3 c) and operating frequency of 0.5 Hz, while the highest is reached at 4 c and 5 Hz. The maximum near-bed velocity point is the furthest from the biomimetic pump when the installation height is 3 c and the operating frequency is 0.5 Hz and the closest at 4 c and 0.5 Hz. At a fixed installation height, a quadratic relationship is found between the maximum near-bed velocity and the operating frequency. At installation heights of c, 2 c, and 4 c, the effect of operating frequency on the point of action is minimal, with only a sudden change followed by stability at 3 c as the frequency increases. When the operating frequency is fixed and the installation height is increased, the maximum near-bed velocity initially decreases and then rises, being the smallest at 3 c. The distance between the point of maximum near-bed velocity and the biomimetic pump initially increases and then decreases with increasing installation height, being the farthest at 3 c. Furthermore, in this paper, we fitted mathematical expressions for the maximum near-bed velocity relative to the operating frequency under different installation heights of the biomimetic pump and calculated the threshold frequencies for the incipient motion of sediment at installation heights of c, 2 c, 3 c, and 4 c to be 1.15 Hz, 1.64 Hz, 2.85 Hz, and 1.06 Hz, respectively, providing scientific guidance for the application of biomimetic pumps in various scenarios. [ABSTRACT FROM AUTHOR]

This study investigates enclosed water bodies to understand the intricate interactions among physical, chemical, and biological processes. A one-dimensional model, integrating sediment and ecosystem components, was developed to analyze oxygen depletion, nutrient dynamics, and the influence of sediment organic matter on oxygen concentrations due to stratification. Oxygen and nutrient concentrations were derived by combining results from a one-dimensional vertical diffusion model with the ecosystem model. The dissolution, adsorption, and desorption of inorganic substances in bottom mud react differently under anaerobic and aerobic conditions, necessitating separate formulations for reduction and oxidation reactions in the bottom mud model. In Lake Biwa, Japan's largest lake, dissolved oxygen levels have decreased despite regulatory efforts since the 1970s, prompting an investigation into the causes of oxygen-depleted water masses. The model was thus applied to examine oxygen consumption in Lake Biwa's deep sediments, shedding light on anoxia in enclosed water bodies. This study emphasizes the significance of bottom sediments in water quality models and their implications for ecosystems. Furthermore, the adaptive nature of this model allows for its application in various water bodies, including freshwater reservoirs, lakes, and saltwater bays. [ABSTRACT FROM AUTHOR]

Silicon (Si) is one of the main biogenic elements in the aquatic ecosystem of lakes, significantly affecting the primary productivity of lakes. Lake sediment is an important sink of Si, which exists in different Si forms and will be released and participate in the recycling of Si when the sediment environment changes. Compared to carbon (C), nitrogen (N) and phosphorus (P), the understanding of different Si forms in sediments and their biogeochemical cycling is currently insufficient. Dianchi Lake, a typical eutrophic lake in southwest China, was selected as an example, and the contents of different Si forms and biogenic silicon (BSi), as well as their correlations with total organic carbon (TOC), total nitrogen (TN), and chlorophyll a in the surface sediments, were systematically investigated to explore Si's recycling characteristics. The results showed that the coupling relationship of the four different Si forms in the surface sediments of Dianchi Lake was poor (p > 0.05), indicating that their sources were relatively independent. Moreover, their formation may be greatly influenced by the adsorption, fixation and redistribution of dissolved silicon by different lake substances. The contents of different Si forms in the surface sediments of Dianchi Lake were ranked as iron-manganese-oxide-bonded silicon (IMOF-Si) > organic sulfide-bonded silicon (OSF-Si) > ion-exchangeable silicon (IEF-Si) > carbonate-bound silicon (CF-Si). In particular, the contents of IMOF-Si and OSF-Si reached 2983.7~3434.7 mg/kg and 1067.6~1324.3 mg/kg, respectively, suggesting that the release and recycling of Si in surface sediments may be more sensitive to changes in redox conditions at the sediment–water interface, which become the main pathway for Si recycling, and the slow degradation of organic matter rich in OSF-Si may lead to long-term and continuous endogenous Si recycling. The low proportion (0.3~0.6%) and spatial differences of biogenic silicon (BSi) in the surface sediments of Dianchi Lake, as well as the poor correlation between BSi and TOC, TN, and chlorophyll a, indicated that the primary productivity of Dianchi Lake was still dominated by cyanobacteria and other algal blooms, while the relative abundance of siliceous organisms such as diatoms was low and closer to the central area of Dianchi Lake. Additionally, BSi may have a faster release capability relative to TOC and may participate in Si recycling. [ABSTRACT FROM AUTHOR]

This study examines the spatial pattern of fractional sediment mobility and assesses the influence of morphologic units on bedload transport in a small pool‐riffle reach with limited supply. Using a 2D hydraulic model and a subsurface‐based sediment transport model, shear stresses, fractional sediment mobility, and bedload transport were examined for flow events ranging in magnitude between 0.2Qbf and 1.5Qbf. Results reveal that while spatial variations in shear stress decrease as discharge increases, only a small proportion of the bed experiences high transport rates. At the reach scale, riffles are the primary morphological unit contributing to fully mobile sediment for all size fractions. However, at a subunit scale, there is evidence of sediment transport reversal for grains >32 mm at flows near or exceeding bankfull discharge in association with shear stress reversal. These transport reversals are important for maintaining pools despite their infrequent occurrence in the study reach. Sediment transport maps indicate that bed morphology considerably influences sediment transport at low to moderate flows. During these events, the shear stress is sensitive to local bed topography and partial mobility is the dominant transport process. In contrast, variations in bedload transport rates decrease during high flows when the flow is less sensitive to variations in bed topography and the bed becomes fully mobile. Key Points: A scaled version of a subsurface‐based model was utilized to evaluate the impact of morphologic units on fractional sediment mobilityRiffles were found to be the main source of fully mobile sediment of all sizes, with local transport reversal observed for grains >32 mmThe impact of morphologic units on bedload transport is more pronounced during low and moderate flows and diminishes during high flows [ABSTRACT FROM AUTHOR]

Geometric characteristics of subaqueous bedforms, such as height, length and leeside angle, are crucial for determining hydraulic form roughness and interpreting sedimentary records. Traditionally, bedform existence and geometry predictors are primarily based on uniform, cohesionless sediments. However, mixtures of sand, silt and clay are common in deltaic, estuarine, and lowland river environments, where bedforms are ubiquitous. Therefore, we investigate the impact of fine sand and silt in sand‐silt mixtures on bedform geometry, based on laboratory experiments conducted in a recirculating flume. We systematically varied the fraction of sand and silt for different discharges, and utilized an acoustic Doppler velocimeter to measure flow velocity profiles. The final bed geometry was captured using a line laser scanner. Our findings reveal that the response of bedforms to an altered fine sediment percentage is ambiguous, and likely depends on, among others, bimodality‐driven bed mobility and sediment cohesiveness. When fine, non‐cohesive material (fine sand or coarse silt) is mixed with the base material (medium sand), an increased dune height and length is observed, possibly caused by the hiding‐exposure effect, resulting in enhanced mobility of the coarser material. However, weakly cohesive fine silt suppresses dune height and length, possibly caused by reduced sediment mobility. Finally, in the transition from dunes to upper stage plane bed, there are indications that the bed becomes unstable and dune heights vary over time. The composition of the bed material does not significantly impact the hydraulic roughness, but mainly affects roughness via the bed morphology, especially the leeside angle. Plain Language Summary: Underwater bedforms, such as dunes, are often found on the bed of rivers and deltas. These rhythmic undulations have specific shapes and sizes, and they affect how water flows. When the bed of the river is made up of sand, we can predict the dune height and length. However, mixtures of different‐sized sediments are common in rivers, and it is unknown how this impacts the geometry of the dunes. Therefore, we did experiments in a flume, a laboratory facility to simulate a river, and we tested different sediment bed mixtures. We found that replacing part of the base material with non‐cohesive fine particles leads to longer dunes, likely caused by increased mobility of the base material. However, for weakly cohesive fine particles, the effect was the opposite, and the dunes became shorter, probably due to the limited mobility of the sediment. Finally, we observed that under high flow conditions, the bed became unstable and different dune shapes occurred. We found that the friction the water experiences is not directly impacted by the sediment bed mixtures, but is mostly affected by the shape of the bedforms. Key Points: An increased dune length due to a larger fraction of finer, non‐cohesive material in a sand bed, implies an increased mobility of the sandA decreased dune size due to a larger fraction of finer, weakly cohesive silt in a sand bed, implies a decreased mobility of the sandSediment bed composition indirectly affects hydraulic roughness by altering bedform geometry [ABSTRACT FROM AUTHOR]

Extreme precipitation is increasing the risk of dam breaks and formation occurring debris dams. Accurate prediction of dam‐break wave propagation is critical to disaster emergency management. Intense bed‐load transport by dam‐break floods can result in a dramatic change of topography, which in turn may affect flood propagation. However, only a very few studies have investigated the thin intense bed‐load layer under dam‐break floods. In this paper, a meshless two‐phase mathematical model is utilized to examine the water velocity, sediment velocity and volumetric fraction, and bed‐load transport flux as well as energy dissipation in bed‐load layer. The model is applied to simulate two‐ and three‐dimensional laboratory experiments of dam‐break wave over erodible beds. For the two‐dimensional experiment, the relative root mean square errors in computed water surface are all below 3.60% and those in profiles of bed‐load layer and static bed are mostly below 13.40%. For the three‐dimensional case, the relative error in computed highest water level is lower than 5.9%. Sediment stream‐wise velocity in bed‐load layer follows a power‐law vertical distribution while sediment volumetric fraction decreases linearly upwards. Accordingly, a formulation of the vertical distribution of bed‐load transport flux, contradictory to the parabolic law in existing studies, is proposed. Most of the water mechanical energy transferred to the sediment is dissipated due to the shear stress in the intense bed‐load layer while only a limit part is kept by the sediment grains. Energy dissipation due to sediment shear stress dominates the consumption of total mechanical energy in the two‐phase system. Key Points: The thin intense bed‐load layer transported by dam‐break floods is numerically examined using a meshless two‐phase mathematical modelA power‐law profile of sediment streamwise velocity and a linear one of sediment volumetric fraction in the thin bed‐load layer are proposedA new formulation of the sediment transport flux in the bed‐load layer is proposed [ABSTRACT FROM AUTHOR]

Copyright of Tropelías: Revista de Teoría de la Literatura y Literatura Comparada is the property of Prensas Universitarias de Zaragoza and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Advances in Earth Science (1001-8166) is the property of Advances in Earth Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ingeniería del Agua is the property of Universidad Politecnica de Valencia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Co-composting efficiently reclaims dredged sediments (S) and green waste (GW), creating stable products for agricultural applications. However, the use of S-GW co-composts can be limited by legislative thresholds, especially for co-composts with a high S percentage. The evaluation of S-GW co-compost stability by biological assessment can allow for a better understanding of S and GW recycling, as well as the S-GW co-compost application. For this purpose, the microbial biomass, composition, respiration, and eco-enzyme stoichiometry (EST) were assessed, coupled with chemical analysis, in the co-composting of S and GW in different ratios. The Photinia x fraseri and Viburnum tinus L. growth was monitored in a plant trial, comparing the studied co-composts with a control substrate. The EST approach was applied as an indicator of the co-composting stability during the process and after the plant cultivation. The chemical and biological parameters confirmed the suitability of co-composting in the GW and S recovery and the EST approach highlighted a better stability for the 3S:1GW co-compost at the end of the process and after plant cultivation. Viburnum tinus showed a similar growth to the control, while Photinia x fraseri resulted in being more sensitive to the co-compost. The biological assessments were good indicators of the S-GW compost stability for their application in crop cultivation. [ABSTRACT FROM AUTHOR]

The forest headwater streams are important hubs for connecting terrestrial and aquatic ecosystems, with plant litter and sediments as the major carriers for material migrations; however, until now we knew little about the dynamics of trace elements such as iron (Fe) and aluminum (Al) in forest headwater streams. Here, we quantitatively identified the spatiotemporal dynamics of Fe and Al storages in plant litter and sediments and their influencing factors in a subtropical forest headwater stream, and assessed the potential pollution risk. The results showed that: (1) the mean concentrations of Fe and Al in plant litter (sediments) were 5.48 and 8.46 (7.39 and 47.47) g·kg−1, and the mean storages of Fe and Al in plant litter (sediments) were 0.26 and 0.43 (749.04 and 5030.90) g·m−2, respectively; (2) the storages of Fe and Al in plant litter and sediments significantly fluctuated from January to December, and showed a decreasing pattern from the source to mouth; and (3) storages of Fe and Al had no significant correlation with riparian forest type and the present of tributary and the Fe and Al storages in plant litter were mainly affected by water temperature and water alkalinity, and their storages in sediments were mainly affected by water temperature and frequency of rainfall; and (4) there were no anthropogenic pollution in Fe and Al in the forest headwater stream. Our study revealed the primary factors of concentrations and storages of Fe and Al in plant litter and sediments in a forest headwater stream, which will improve our understanding of the role of headwater streams in forest nutrient storage and cycling along with hydrological processes. [ABSTRACT FROM AUTHOR]

Paleoceanographic interpretations of Plio-Pleistocene climate variability over the past 5 million years rely on the evaluation of event timing of proxy changes in sparse records across multiple ocean basins. In turn, orbital-scale chronostratigraphic controls for these records are often built from stratigraphic alignment of benthic foraminiferal stable oxygen isotope (δ18 O) records to a preferred dated target stack or composite. This chronostratigraphic age model approach yields age model uncertainties associated with alignment method, target selection, the assumption that the undated record and target experienced synchronous changes in benthic foraminiferal δ18 O values, and the assumption that any possible stratigraphic discontinuities within the undated record have been appropriately identified. However, these age model uncertainties and their impact on paleoceanographic interpretations are seldom reported or discussed. Here, we investigate and discuss these uncertainties for conventional manual and automated tuning techniques based on benthic foraminiferal δ18 O records and evaluate their impact on sedimentary age models over the past 3.5 Myr using three sedimentary benthic foraminiferal δ18 O records as case studies. In one case study, we present a new benthic foraminiferal δ18 O record for International Ocean Discovery Program (IODP) Site U1541 (54°13 ′ S, 125°25 ′ W), recently recovered from the South Pacific on IODP Expedition 383. The other two case studies examine published benthic foraminiferal δ18 O records of Ocean Drilling Program (ODP) Site 1090 and the ODP Site 980/981 composite. Our analysis suggests average age uncertainties of 3 to 5 kyr associated with manually derived versus automated alignment, 1 to 3 kyr associated with automated probabilistic alignment itself, and 2 to 6 kyr associated with the choice of tuning target. Age uncertainties are higher near stratigraphic segment ends and where local benthic foraminiferal δ18 O stratigraphy differs from the tuning target. We conclude with recommendations for community best practices for the development and characterization of age uncertainty of sediment core chronostratigraphies based on benthic foraminiferal δ18 O records. [ABSTRACT FROM AUTHOR]

Accretionary complexes in the Japanese Islands preserve material from parts of the oceanic plates of Panthalassa that have subducted and are now lost. The age of the oceanic plate that is incorporated into the Jurassic accretionary complex of Japan has been previously estimated from scant data on Carboniferous bedded chert. In this study, we investigated a Carboniferous to Permian basalt-chert sequence in the Jurassic accretionary complex of the North Kitakami-Oshima belt in Northeast Japan. The sequence is composed of basaltic rocks, red bedded chert and grey bedded chert in ascending order. The basaltic rocks at the base contain red cherty nodules that yielded conodonts indicating the Bashkiran to early Moscovian, the latter age being more likely (late Carboniferous). The red bedded chert yielded middle Sakmarian (early Permian) radiolarians. The grey bedded chert yielded conodonts indicating the latest Kungurian to earliest Roadian. Thus, our study section demonstrates a formation of the oceanic plate in the late Carboniferous and a following deposition of pelagic siliceous sediments. This is the first time that basaltic rocks within the Jurassic accretionary complex of Japan are directly dated. While previous data need careful reviewing, our results demonstrate that the oldest part of the oceanic plate within the Jurassic accretionary complex is Serpukhovian or older and the youngest part may be as young as the Sakmarian. [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]

Mapping the sedimentary character of the seafloor in large water‐filled basins is fundamental for understanding landform dynamics to inform research, management, intervention and conservation actions. Seabed mapping methods have undergone considerable development in the last two decades, including the uptake of machine learning approaches for sediment size prediction and classification. However, predictions of surficial sediment characteristics are often hindered by the availability of ground truthing data, their arrangement in space and the modelling approach chosen. Spatially informed sampling designs provide an opportunity to significantly improve the accuracy and uncertainty of predicted sediment distributions. In this study, we apply a machine learning algorithm to predict sediment distributions across Port Phillip Bay, a large (1930 km2) structurally controlled estuary on the southeast coast of Victoria, Australia. Surface sediment samples (n = 252) were collected using a spatially balanced design, ensuring that sampling effort was spread evenly within the embayment with increased sampling intensity placed in more heterogeneous areas. Surficial textural metrics were modelled using the random forest algorithm with bathymetric and hydrodynamic predictor variables. Models highlighted trends in sediment grain size, sorting and composition consistent with predicted wave‐ and current‐induced sediment mobilisation. Model predictions were accurate (normalised‐root mean squared error [NRMSE]: 0.14–0.16); however, standard error was not homogeneous across the study area. Uncertainty maps highlighted areas where additional sampling effort may be needed, including areas where transitional bathymetry impacted surficial sediment character and areas of anthropogenic modifications to the seabed. This study shows the benefits of undertaking spatially informed sample design, block cross‐validation during model fitting and quantifying spatial uncertainty in predictive maps to accurately quantify the fundamental boundary conditions of sediment size. The results of this study are intended to inform local coastal management, including beach renourishment activities. However, approaches outlined are applicable to any study where the seafloor grain size is a fundamental variable in understanding landscape change. [ABSTRACT FROM AUTHOR]

Extreme precipitation events in small alpine catchments trigger hazardous hydro‐geomorphic processes that cause considerable damage to settlements and infrastructure. In summer 2011 and 2017, two flood events mobilizing large amounts of sediments struck the town of Oberwölz (Styria, Austria) located at the outlet of the Schöttlbach catchment. We used data from local weather stations and precipitation radar to analyse the meteorological settings that caused the flooding. We compiled a consistent sediment budget for the 2017 event by combining geomorphic mapping, connectivity analysis, high‐resolution airborne LiDAR (ALS) and uncrewed aerial vehicle (UAV)‐borne LiDAR (ULS), data from other authors for the 2011 event and external information (e.g., event analysis and excavation data). The 2017 event mobilized higher sediment volumes than the 2011 event (131 000 m3 vs 90 000 m3) even though 24‐h precipitation and peak discharges were lower in 2017. First assumptions that the larger sediment output was caused by the reworking of the 2011 flood deposits proved to be incorrect. The impacts of the 2011 event affected the resilience of the geomorphic system resulting in a significantly higher hillslope sediment supply. We conclude that sediment transport in alpine catchments can increase disproportionately when recurrence intervals fall below a critical level. [ABSTRACT FROM AUTHOR]

Sediment management is an important aspect of dam removal projects, often driving costs and influencing community acceptance. For dams storing uncontaminated sediments, downstream release is often the cheapest and most practical approach and can be ecologically beneficial to downstream areas deprived of sediment for years. To employ this option, project proponents must estimate the sediment quantity to be released and, if substantial, estimate how long it will take to erode, where it will go and how long it will stay there. We investigated these issues when the Bloede Dam was removed from the Patapsco River in Maryland, USA, in 2018. The dam was about 10 m high, and its impoundment was nearly filled with an estimated 186 600 m3 of sediment composed of 70% sand and 30% mud. After removal, using elevation surveys generated by traditional methods as well as structure‐from‐motion (SfM) photogrammetry at high temporal resolution, we documented rapid erosion of stored sediments in the first 6 months (~60%) followed by greatly reduced erosion rates for the next two and a half years. A stable channel developed in the impoundment during the rapid erosion phase. These results were predicted by a two‐phased erosion response model developed from observations at sand‐filled impoundments, thus expanding its applicability to include impoundments with a sand‐over‐mud stratigraphy. A similar two‐phase erosion response has been reported for sediment releases at other dam removals in the United States, France and Japan across a range of dam and watershed scales, indicating what practitioners and communities should expect in similar settings. Downstream, repeat surveys combined with discharge and sediment gaging showed rapid transport of eroded sediments through a 5‐km reach, especially during the first year when discharges were above normal, and little overbank storage. [ABSTRACT FROM AUTHOR]

Floodplains constitute a vital and integrated component of the riverine network ensuring the connectivity and continuity of the river with the upland watershed areas. However, the sediment trapping efficiency of floodplains has not been well investigated. The purpose of this experimental study was to evaluate the functionality of floodplains to act as either sources or sinks for fine sediments and sediment‐bound nutrients (e.g., total phosphorus) during floods of various return periods. Thus, we hypothesized that (i) soil texture, in terms of topsoil erodibility and (ii) the magnitude of the incoming flood, in terms of the applied shear stress, are the two key parameters govern river floodplains' ability to store or release fine sediments and total phosphorus, during major flood conditions. Topsoil erodibility experiments were coupled with site‐specific flood inundation maps to estimate the eroded fine sediment mass and the total phosphorus release rates per unit area per unit time of each flood condition considered. Results suggested that the floodplain soils of the upstream reaches act as net sources, the floodplains of the midstream reaches have a dual functionality; during low magnitude flood events (up to 10‐year return periods), they act as net sinks, while during higher flood events, they act as sources; and the floodplains of the downstream reaches largely act as sinks. This study results are applicable for watershed managers to identify floodplain areas vulnerable to erosion and sources of nutrient pollution. [ABSTRACT FROM AUTHOR]

The main aim of this study was to investigated background levels of radioisotopes 137Cs (Cesium), 232Th (Thorium), 40K (Potassium), and 226Ra (Radium) in all samples taken from two important rivers of the Sinop province prior to the nuclear power plant. The sediment samples were taken from the Karasu (80 km) and Kabalı (51.3 km) rivers at 2 km distances in July 2019, the month with the least precipitation, and in December 2018, the month with the most precipitation, before the nuclear power plant built in the Sinop province became active. The concentrations of 226Ra, 232Th, 137Cs and 40K in the collected sediment samples were measured using a high purity germanium detector (HPGe). The activity concentrations of 226Ra, 232Th, 137Cs and 40K in the sediment samples taken from the Karasu River in December and in July were in the range of 3.08–29.40 Bq/kg, 2.95–19.10 Bq/kg, 0.35–61.13 Bq/kg and 54.83–495.02 Bq/kg, respectively. In the sediment samples collected from the Kabalı River in December and in July, 226Ra, 232Th, 137Cs and 40K activity concentrations were in the range of 5.79–25.65 Bq/kg, 3.35–19.55 Bq/kg, 0.97–7.23 Bq/kg and 141.66–446.77 Bq/kg, respectively. Some risk parameters were also calculated to assess radiological hazards. These values were found to be lower than the world averages recommended by international organizations. Based on all the results obtained, it can be concluded that the examined samples do not pose a radiological risk. [ABSTRACT FROM AUTHOR]

Purpose: Hyporheic biofilms are the central site for biogeochemical cycling in streams and rivers. In view of global warming and increasing human pressures, this study aimed to compare the response of hyporheic biofilm biomass and activities from an unpolluted reference stream reach surrounded by forest with those from a stream reach exposed to agricultural and urban land use using a mesocosm experiment in which the water temperature and dissolved organic carbon (DOC) contents were manipulated. Methods: Hyporheic sediments collected in the field from the two study reaches (i.e. reference and impacted) were incubated in the laboratory at two different temperatures (10 °C, 14 °C) and wetted with three types of synthetic water (control [C] – 0 mg L−1; low DOC – 5 mg L−1; high DOC – 30 mg L−1) for four weeks. The responses of the hyporheic biofilms were measured weekly using structural (total protein content [TPC] as a proxy for biofilm biomass) and functional measures (electron transport system activity [ETSA] and community-level physiological profiling [CLPP]). Results: The response of hyporheic biofilms to temperature changes and DOC enrichment was site-specific for all studied measures (TPC, ETSA and CLPP, including measured average well colour development [AWCD]). The addition of DOC to biofilms from the pristine stream reach significantly heightened the responses at 10 °C, a temperature within the normal environmental temperature ranges of the reference location, but not at 14 °C, which was here, a temperature outside normal environmental range. On the other hand, biofilms from the impacted stream reach exhibited increased responses following DOC enrichment under both temperature regimes, with a particularly pronounced response at 14 ºC, in this case, both experimental temperatures were within the normal environmental temperature ranges of the study locations. Conclusion: Hyporheic biofilms were shown to be, like benthic biofilms, sensitive to temperature changes and organic enrichment, but their response to temperature changes and enrichment caused by climate change and/or other anthropogenic pressures (i.e. point and non-point pollution, removal of the riparian zone, hydromorphological modifications, etc.) was not simply linear but site-specific. The intensity of the response, characterized by increased activity and biomass production, appears to be constrained within the temperature ranges prevalent in the environment from which the biofilms originate. These findings emphasize the importance of site-specific considerations in predicting the impacts of climate change and anthropogenic pressures on these critical components of river and stream ecosystems. [ABSTRACT FROM AUTHOR]

Spatangoid heart urchins are dominant bioturbators in marine soft-sediment ecosystems worldwide. Their repeated sediment reworking prevents biogeochemical sediment stratification and colonization by other species, with implications for sedimentary reaction processes that affect the local sediment–seawater solute exchange. Here, we used a simple exclusion experiment to investigate how a subtidal Echinocardium cordatum population (18.2 ± 6.7 individuals m−2), foraging at an individual speed of ~45 cm per day affects the sediment–seawater solute exchange. To do so, we removed all heart urchins from eight one-meter-diameter areas of the 10-m deep seafloor of Man O'War Bay, Hauraki Gulf, New Zealand, and prevented recolonization and thus sediment reworking for 56 days. Subsequently, we measured the sediment–seawater exchange of O2, NO3–, NO2–, NH4+, and N2 both within and outside the exclusion areas, under light or dark conditions, and found no difference. The absence of a legacy effect of foraging E. cordatum after their removal suggests that, at least in this habitat, their influence on the sediment–seawater solute exchange may be limited to sediment being displaced in the immediate surrounding of the urchin. This unexpected result underlines the importance of evaluating the influence of bioturbators on the sediment–seawater solute exchange in the context of local environmental conditions, animal behavior, and population characteristics. [ABSTRACT FROM AUTHOR]

Organic carbon (OC) in permafrost interacts with the mineral fraction of soil and sediments, representing < 1% to ~80% of the total OC pool. Quantifying the nature and controls of mineral–OC interactions is therefore crucial for realistic assessments of permafrost‐carbon‐climate feedbacks, especially in ice‐rich regions facing rapid thaw and the development of thermo‐erosion landforms. Here, we analyzed sediment samples from the Batagay megaslump in East Siberia, and we present total element concentrations, mineralogy, and mineral–OC interactions in its different stratigraphic units. Our findings indicate that up to 34 ± 8% of the OC pool interacts with mineral surfaces or elements. Interglacial deposits exhibit enhanced OC–mineral interactions, where OC has undergone greater microbial transformation and has likely low degradability. We provide a first‐order estimate of ~12,000 tons of OC mobilized annually downslope of the headwall (i.e., the approximate mass of 30 large aircrafts), with a maximum of 38% interacting with OC via complexation with metals or associations to poorly crystalline iron oxides. These data imply that over one‐third of the OC exposed by the slump is not readily available for mineralization, potentially leading to prolonged OC residence time in soil and sediments under stable physicochemical conditions. [ABSTRACT FROM AUTHOR]

In this study examining the effects of temperature and dissolved oxygen (DO) on arsenic (As) release at the sediment–water interface (SWI), it was found that an increase in temperature promoted the formation of an anaerobic environment and the reduction and desorption of As fractions within the sediments. A temperature of 32 °C was the most favorable condition for As release at the SWI, and low DO conditions aggravated this process. Even under high DO conditions, the release of sediment As was significantly accelerated under high-temperature conditions, allowing dissolved As to rapidly migrate to the overlying water. In this process, the release of As from sediments was a consequence of the transformation of As fractions in the sediments. [ABSTRACT FROM AUTHOR]

Phthalic acid esters (PAEs), recognized as endocrine disruptors, are identified as predominant organic pollutants in the Three Gorges Reservoir (TGR). Di-n-butyl phthalate (DBP), a representative PAE, has been extensively studied for its sources, distribution and ecological risks. However, there are few studies on the adsorption of DBP by sediment from the TGR, and the adsorption characteristics of surface sediment on DBP are not clear. Therefore, based on the actual sediment contents and particle sizes in the TGR, the kinetics and isothermal adsorption characteristics of surface sediment on DBP were investigated in this study. The results showed that the equilibrium time was 120 min, the adsorption kinetics were more in line with the pseudo-second-order kinetic model, and the sediment in water from the Yangtze River exhibited a higher adsorption rate and maximum adsorption amount on DBP than that observed in deionized water. Additionally, a decrease in DBP adsorption was observed with increasing sediment content, while sediment particle size and specific surface area had a slight influence. Analysis using SEM, TGA and FTIR revealed that organic matter on the sediment surface significantly contributed to DBP adsorption. This study contributes valuable insights into the adsorption characteristics of DBP by the surface sediment from the TGR, providing a scientific foundation for understanding the migration and transformation of DBP in this critical reservoir in China. [ABSTRACT FROM AUTHOR]

Balancing between sediment removal discharge and dam reservoir storage loss considering river environmental impact is of major and practical concern. The paper presents indices for evaluating the sediment removal performance of a Vertical Multi-hole Hydrosuction System (VMHS) in view of environmental impacts. A new hole arrangement on the vertical pipe of VMHS was experimentally examined. The compiled data of the temporal variations of the sediment concentration and the cumulative volume of removed sediment demonstrated that the arrangement of the holes on the vertical pipe of VMHS has profound impact on the speed of sediment removal and on the reservoir water loss. The high concentration of the outflow from the reservoir, however, might affect the downstream water course environment. The proposed indices could be applied to determine the proper duration for terminating the hydrosuction process in order to obtain a balance between the storage capacity and the downstream water course environment. [ABSTRACT FROM AUTHOR]

Seagrass meadows are known as hot spots for carbon accumulation, but there is limited field data on the variability of sediment accumulation across time and space. We developed a method to assess spatial and temporal heterogeneity in net sediment accumulation in seagrass meadows using small, inexpensive samplers, allowing for over 200 unique measurements across multiple transects within our study site. Using this method, we assessed sediment accumulation across seagrass meadow edges, and in varying weather conditions. We found the greatest accumulation of sediment 5 m outside of seagrass meadow edges, with sediment accumulation rates averaging just under 100 g m−2 day−1, though rates were highly variable. Carbon accumulation from settled sediment was generally greater outside of seagrass meadow edges than within the bed, especially at sites undergoing recent expansion. Measurements made during tropical storms showed both scouring of sediment away from sites, and increased accumulation, depending on site properties as well as individual tropical storm characteristics. In the storm that had a measurable storm surge, scouring of sediment was a more dominant mechanism, whereas deposition dominated in the storm that had high winds but no associated storm surge. Our data demonstrate the necessity of including measurements that characterize both spatial and meteorological variability to develop a more holistic understanding of the movement of sediment and particulate organic carbon associated with seagrass meadows, especially as meadow area becomes increasingly fragmented with human activity and global change. [ABSTRACT FROM AUTHOR]

The sea bottom acts as a key natural archive where the memory of long-term timescale environmental changes is recorded. This study discusses some ecological and chemical features of fjord sediments that were explored during the AREX cruise carried out in the Svalbard archipelago in the summer of 2021. The activity rates of the enzymes leucine aminopeptidase (LAP), beta-glucosidase (GLU), and alkaline phosphatase (AP) and community-level physiological profiles (CLPPs) were studied with the aim of determining the functional diversity of the benthic microbial community, while bacterial isolates were screened for their susceptibility to antibiotics in order to explore the role of these extreme environments as potential reservoirs of antibiotic resistance. Enzyme activity rates were obtained using fluorogenic substrates, and CLPPs were obtained using Biolog Ecoplates; antibiotic susceptibility assays were performed through the standard disk diffusion method. Spatial trends observed in the functional profiles of the microbial community suggested variability in the microbial community's composition, presumably related to the patchy distribution of organic substrates. Complex carbon sources, carbohydrates, and amino acids were the organic polymers preferentially metabolized by the microbial community. Multi-resistance to enrofloxacin and tetracycline was detected in all of the examined samples, stressing the role of sediments as a potential reservoir of chemical wastes ascribable to antibiotic residuals. This study provides new insights on the health status of fjord sediments of West Spitsbergen, applying a dual ecological and biochemical approach. Microbial communities in the fjord sediments showed globally a good functional diversity, suggesting their versatility to rapidly react to changing conditions. The lack of significant diversification among the three studied areas suggests that microbial variables alone cannot be suitable descriptors of sediment health, and that additional measures (i.e., physical–chemical characteristics) should be taken to better define environmental status. [ABSTRACT FROM AUTHOR]

Mercury is a highly toxic element present in water, soil, air, and biota. Anthropogenic activities, such as burning fossil fuels, mining, and deforestation, contribute to the presence and mobilization of mercury between environmental compartments. Although current research on mercury pathways has advanced our understanding of the risks associated with human exposure, limited information exists for remote areas with high diversity of fauna, flora, and indigenous communities. This study aims to deepen our understanding of the presence of total mercury in water, sediments, and fish, within aquatic ecosystems of two indigenous territories: Gomataon (Waorani Nationality) and Sinangoé (Ai´Cofán Nationality) in the Ecuadorian Amazon. Our findings indicate that, for most fish (91.5%), sediment (100%) and water (95.3%) samples, mercury levels fall under international limits. For fish, no significant differences in mercury levels were detected between the two communities. However, eight species exceeded recommended global limits, and one surpassed the threshold according to Ecuadorian legislation. Piscivore and omnivore fish exhibited the highest concentrations of total mercury among trophic guilds. Only one water sample from each community's territory exceeded these limits. Total mercury in sediments exhibited greater concentrations in Gomataon than Sinangoé. Greater levels of mercury in sediments were associated with the occurrence of total organic carbon. Considering that members of the communities consume the analyzed fish, an interdisciplinary approach, including isotopic analysis, methylmercury sampling in humans, and mercury monitoring over time, is imperative for a detailed risk assessment of mercury exposure in Amazonian communities. [ABSTRACT FROM AUTHOR]

Using relative reflectance measurements from the Mastcam‐Z and SuperCam instruments on the Mars 2020 Perseverance rover, we assess the variability of Fe mineralogy in Noachian/Hesperian‐aged rocks at Jezero crater. The results reveal diverse Fe3+ and Fe2+ minerals. The igneous crater floor, where small amounts of Fe3+‐phyllosilicates and poorly crystalline Fe3+‐oxyhydroxides have been reported, is spectrally similar to most oxidized basalts observed at Gusev crater. At the base of the western Jezero sedimentary fan, new spectral type points to an Fe‐bearing mineral assemblage likely dominated by Fe2+. By contrast, most strata exposed at the fan front show signatures of Fe3+‐oxides (mostly fine‐grained crystalline hematite), Fe3+‐sulfates (potentially copiapites), strong signatures of hydration, and among the strongest signatures of red hematite observed in situ, consistent with materials having experienced vigorous water‐rock interactions and/or higher degrees of diagenesis under oxidizing conditions. The fan top strata show hydration but little to no signs of Fe oxidation likely implying that some periods of fan construction occurred either during a reduced atmosphere era or during short‐lived aqueous activity of liquid water in contact with an oxidized atmosphere. We also report the discovery of alternating cm‐scale bands of red and gray layers correlated with hydration and oxide variability, which has not yet been observed elsewhere on Mars. This could result from syn‐depositional fluid chemistry variations, possibly as seasonal processes, or diagenetic overprint of oxidized fluids percolating through strata having variable permeability. Plain Language Summary: The oxidation states of the atmosphere and waters (whether rich or poor in oxidants such as oxygen) of Mars and their evolution are poorly constrained but can be recorded in the iron (Fe) mineralogy of rocks. Using data from the Perseverance rover, we analyzed the Fe mineralogy of ∼4–3 Ga old rocks from an ancient lake at Jezero crater. Oxidized Fe is found in igneous rocks and lowermost portions of sedimentary rocks, carried by clays and poorly crystalline oxides in the former and by sulfates and crystalline oxides in the latter, pointing to past action of oxidizing fluids, affecting more intensely the sedimentary rocks. Fe shows poor to no signs of oxidation in the uppermost strata, which might be evidence for a reducing atmosphere during sediment deposition or that the aqueous environment was too cold or too short‐lived to oxidize minerals. We also report Fe mineralogy variability at the cm‐scale in alternating colored layers, which has not been observed previously on Mars and could possibly mean that seasonal processes are recorded at Jezero crater. Key Points: In situ reflectance data measured with Mars 2020 show variable Fe mineralogy in sedimentary rocks at Jezero craterStrata exposed at the fan front experienced stronger oxidative water‐rock interactions compared to the upper fan and igneous crater floorWe identify cm‐scale color banding correlated with Fe‐oxide variability that likely indicates time variation in redox [ABSTRACT FROM AUTHOR]

A power law velocity profile for engineering application was obtained based on the field data set of flow velocity and sediment concentration in coastal areas of Jinzhou, Nantong, and Zhoushan. Using theoretical analyses, van Rijn's formula for sediment concentration profile was modified. Tests of the new power-law velocity profile and the modified formula of suspended sediment concentration against a large data set were performed. The results show a good fit to the data and that these two formulae could demonstrate the basic principles of vertical distribution of flow velocity and suspended sediment concentration, respectively. [ABSTRACT FROM AUTHOR]

Burullus lagoon is part of Egypt's protected area network. The lagoon serves as a reservoir for drainage water discharged from agricultural areas, and the lake's sediments provide a unique opportunity to record environmental behavior and reconstruct of the heavy metal contamination history. In the present study, the sediment chronology, sedimentation rates, and metal accumulation fluxes were estimated in four sediment cores using 210Pb dating models to evaluate how human activities have affected the coastal environment. Using the radioisotopes 210Pb and 137Cs, radiometric dating was carried out using gamma-ray spectrometry. At the Egypt Second Research Reactor (ETRR-2), the element concentrations were determined using the instrumented neutron activation analysis (INAA- k0 method). Our findings show that the constant rate of supply (CRS), which has been verified with the peak of artificial radionuclide 137Cs, is the best model performed for the chronology of Burullus Lagoon. The average sedimentation rate, according to 210Pb dating models, is 0.85 cm/year. The large variation in sedimentation rates, especially after the 1990s, is consistent with an increase in the anthropogenic flux of heavy metals. This may be led into a significant environmental problem such as reducing the size of the lake and degrading the quality the water in Burullus Lagoon. Enrichment factor (EF) of the studied elements displayed the following order: Cl > Ca > Na > Br > Zn > Ta > Ti > V > Cr > Sc > Mg > Mn > Fe > Hf which is higher than unity. Furthermore, the Nemerow pollution index (PI Nemerow) revealed that pollution was increasing in the direction of the drains and slightly polluted. Consequently, pollutant indices showed that urbanization and industrial development may have increased the depositional fluxes of the metals in sediments over time. [ABSTRACT FROM AUTHOR]