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In this study, we observed natural methane (CH4) hydrate sediments, which are a type of unconventional natural gas resources, using x-ray computed tomography (CT). Because CH4 hydrates are formed by hydrogen bonding of water molecules with CH4, material decomposition becomes challenging when CH4 hydrates coexist with liquid or solid water in natural sediments. Tri-contrast (absorption, refraction, and scattering) imaging was performed via diffraction enhanced x-ray CT optics using monochromatic synchrotron x rays. The quantitative characterization of the contrast changes successfully enabled the decomposition of CH4 hydrates coexisting with frozen seawater (ice) in natural sediments obtained from the Okhotsk Sea. This study reveals complementary structural information about the microtexture and spatial relation among CH4 hydrates, ice, and pores by utilizing the distinct physical properties of x rays when passing through the materials. These results highlight the exceptional capabilities of high-resolution multicontrast x-ray tomography in materials science and geoscience applications. [ABSTRACT FROM AUTHOR]

Meandering channels are common in natural rivers, especially in lowland alluvial plains. In this research, a meandering channel was designed in order to explore the effect of sediment supply on the flow characteristics. The water level, three-dimensional (3D) instantaneous velocity and riverbed elevation were measured using a digital wave altimeter, a 3D acoustic Doppler velocimeter and a 3D laser scanner, respectively, and the flow characteristics with and without sediment supply were compared. Under the same discharge, the transverse slope of the water surface in the case with sediment was larger than that without sediment and the change was steep; the change in the longitudinal slope of the water surface was small in the upper half bend and large in the lower half bend. By increasing the water discharge, the number of secondary flow vortices at the apex of the meandering channel increased. The trends of the mainstream lines with and without sediment supply were roughly opposite and the difference between them decreased with increasing discharge. The lateral and vertical turbulence intensities of the flow near the outer bank were larger in both cases (with and without sediment). In the case with sediment, the turbulent kinetic energy of the cross-section was larger near the bed and the water surface. [ABSTRACT FROM AUTHOR]

The two most common oxidation states of iron can be determined by wavelength‐dispersive X‐ray fluorescence spectrometry relatively fast with an accuracy comparable to that of alternative methods. Main advantages for the analysis of sediments and soils are that organic matter does not interfere and solid samples can be analysed directly with minimal preparation effort. The limited availability of appropriate reference materials with certified data on their ferrous iron content turned out to be the major obstacle to implementing the method. For this reason and because no influence of the analysed geological materials on the intensity ratios of the closely adjacent Fe Kβ5 / Fe Kβ1,3 lines became evident, several rock types were selected in addition to sediments and soils to broaden and improve the calibration. Nevertheless, most reference data for calibration had to be determined by 57Fe Mössbauer spectroscopy. Plotting Fe Kβ5/Fe Kβ1,3 intensity ratios versus w FeO/w Fe2O3total ratios resulted in a correlation with R2 = 0.962 for the linear regression of all calibration data. [ABSTRACT FROM AUTHOR]

The potential application of conducting Scholte‐wave analysis using electroseismic pressure fields excited by an electric current source due to the electrokinetic effect in fluid‐saturated porous seabed sediments is investigated. First, we develop a numerical modelling algorithm by combining the Luco–Apsel–Chen generalized reflection and transmission method with the peak‐trough averaging method to simulate the electroseismic wave fields in stratified fluid/porous media. The modelling results show that the electroseismic pressure signals recorded on the seafloor are mainly composed of evanescent electroseismic waves, and Scholte waves are the dominant wave pattern. Their amplitudes are generally within the order of magnitudes capable of being detected by current seismic instruments. Then, the modified frequency–Bessel transform method is extended to extract the Scholte‐wave dispersion curves from electroseismic pressure fields. Results demonstrate that Scholte‐wave dispersion curves extracted from electroseismic records are superior to those extracted from conventional seismic wave fields excited by an airgun source under the same source–receiver geometry because they contain many overtones and are almost free from the interferences of dispersive guided waves. Furthermore, the Scholte‐wave dispersion inversion results obtained by employing the Levenberg–Marquardt method show that the shear‐wave velocity model inverted by Scholte‐wave dispersion curves extracted from the electroseismic pressure field is more accurate than those obtained by dispersion curves extracted from the seismic wave fields with the guided‐wave removal. The above results indicate that the electroseismic Scholte‐wave analysis method has the potential to evaluate the shear‐wave velocities of shallow‐water seabed sediments. [ABSTRACT FROM AUTHOR]

Strong rainfalls and river floods are becoming increasingly frequent and intense in southern Europe. Mediterranean coastal lagoons, due to their hydrological characteristics, could mitigate the consequences of such events, whose effects on sediment biogeochemistry are poorly studied, yet. To provide insights on this, we investigated short-term changes in organic matter quantity, composition, nutritional quality, degradation rates, and turnover time in a lagoonal benthocosm. Both flooding and recovery phases increased the sedimentary organic load and turnover time, whereas phytopigment contents and C degradation rates were not affected. The biochemical composition varied during both phases, with an increase in carbohydrate and lipid after the flooding, and an increase in protein and chlorophyll-a after its recovery. Our results suggest that even sudden changes in salinity caused by floods and their recovery can increase sedimentary organic loads, with minor effects on their nutritional quality. The observed effects of the flooding persist in the short-term also after the recovery of the salinity, when the substrates are pre-eminently of heterotrophic origin. Our results suggest that extreme, even if short-lasting, episodic events of flooding and recovery can severely alter the benthic trophic status of coastal lagoons, having possible effects on benthic trophodynamics. [ABSTRACT FROM AUTHOR]

The grain‐size distributions of sediments can yield important information about sediment provenance and sedimentary processes; however, grain‐size distributions are frequently polymodal, rendering analyses difficult. To improve analyses of polymodal grain‐size data, the present study decomposed the grain‐size distributions of bottom surface sediments from Lake Kitaura, a shallow lake in Japan, into lognormal distributions and performed logratio analysis of their mixing proportions. The polymodal grain‐size distributions of the studied samples were separated into four common components at most sites. This logratio analysis revealed clear differences in the characteristics of the spatial distributions of the separated grain‐size components. The logratio values indicated that the three finer components were uniformly deposited within the lake, whereas the coarsest component was spatially diverse, reflecting differences in their sources and sedimentary processes. These results demonstrate the effectiveness of decomposition and logratio analysis of polymodal grain‐size distributions for estimating sedimentary processes. This method can be applied to modern sediments and for palaeoenvironmental reconstructions using sediment cores. [ABSTRACT FROM AUTHOR]

Autogenic feedbacks can produce large‐scale, organized stratigraphic patterns in alluvial fans, but autogenic depositional signatures of specific upstream boundary conditions remain challenging to interpret. Here, a combination of theory, experiment and field application is used to explore how autogenic lithofacies changes can be interpreted as stratigraphic indicators of upstream boundary conditions. Six experiments were conducted to test the effects of sediment supply and water discharge rates on autogenic advance and retreat of the lithofacies boundary (grain‐size transition) in an alluvial fan with two dominant grain sizes. Migration of the grain‐size transition caused a short‐term zigzag pattern in the grain‐size transition position in the dip‐directional deposit section. For each experiment, time‐lapse images and laser topographic scans of the fan surface and stratigraphic cross‐sections of the final deposits were used to quantify characteristic timescales of autogenic processes. Timescales for fan‐margin migration, surface wet‐fraction change and grain‐size transition migration generally shorten as sediment supply rate increases and water discharge rate decreases. Increasing the sediment supply rate shortens the duration of the fluvial sediment storage and release cycle, producing higher frequency zigzags in the grain‐size transition trajectory. Increasing the water discharge tends to widen channels and lengthens the duration of the fluvial sediment storage and release cycle, constructing lower frequency zigzags in the grain‐size transition trajectory. Increasing the water discharge also enables more sediment to transport further downstream during release events, leading to higher magnitude zigzags in the grain‐size transition trajectory. These relationships between upstream boundary conditions and the grain‐size transition trajectory demonstrate how autogenic stratigraphic signals could be used as a tool to infer relative changes in boundary conditions. [ABSTRACT FROM AUTHOR]

This is the first report on abundance and diversity of cultured filamentous fungi and on abundance of yeasts in the sediments of the Laptev and East Siberian seas. A total of 63 isolates of filamentous fungi belonging to 32 morphotypes were obtained from 35 sediment samples. Most morphotypes were represented by single colonies in individual samples; the most frequently occurring species were Pseudeurotiumzonatum, Pseudogymnoascuspannorum, and Cordycepsfarinosа. In both seas, the abundance of filamentous fungi (up to 12 colonies per 1 g wet sediment) was lower than that of yeasts (up to 68 colonies per 1 g wet sediment). In the Laptev Sea, yeast abundance was low at all stations, while in the East Siberian Sea higher values were found at near-estuarine stations. [ABSTRACT FROM AUTHOR]

The sources of thermophilic bacteria revealed in cold Lake Baikal sediments are considered. Comparative analysis of the taxonomic position of thermophilic microorganisms from four terrestrial hot springs at Lake Baikal coast and from the bottom sediments associated with hydrocarbon discharge was carried out. The sequences of thermophilic microorganisms with the same taxonomic position were revealed both in the hot springs and bottom sediments. Some microbial species occurred only in the hydrotherm samples or only in those from the sediments. Gas-saturated fluids from the hydrocarbon generation zone at the depth of 4‒6 km are the most probable source of thermophilic microorganisms in the bottom sediments. [ABSTRACT FROM AUTHOR]

Degradation of oil hydrocarbons artificially introduced into bottom sediments in a bioelectrochemical system of a membrane-free (silt) type was studied. Passive bioelectrochemical stimulation by means of electrodes connected by an external circuit with a resistance of 1 kΩ, with an average electric current of ~85 µA was found to cause an increase in degradation during two months from 23.0 to 57.9%. Contamination of bottom sediments with oil (1.32 g/kg) slightly decreased the current in the external circuit of the bioelectrochemical system. The relationship was revealed between the degree of oil degradation and predominant utilization of the lighter n-alkanes in the C14H30–C30H62 series, compared with both the original oil and the residual hydrocarbons of the control. An increase in the representation of the alkB alkane monooxygenase genes relative to the 16S rRNA gene in the total DNA isolated from the sediments was induced by the introduction of hexadecane, both in the case of electrochemical stimulation and in the control. The results may be of interest for the development of new methods of bioelectrochemical removal of organic pollutants from anaerobic environments. [ABSTRACT FROM AUTHOR]

Although tin mining activities in the southern part of Thailand have been abandoned for more than 40 years, arsenic contamination in old tin-mining areas continues to pose a health risk. Fortunately, natural adsorption of arsenic by sediment has reduced the arsenic concentration in water to the maximum allowable level within a 10-kilometre radius of the mine sources. This article attempts to characterize the arsenic adsorption properties of sediment along a water creek which passes through the old tin-mine areas in Ron Phibun district, Nakhon Si Thammarat province, Thailand, where the contamination has been most severe. It was found that Fe tends to be associated with the adsorption capacity of arsenic in sediment. However, pH 4 and pH 7 did not associate with adsorption capacity. At pH 12, the solubility of arsenic increases, making it less likely to be adsorbed into the sediment and more likely to dissolve in water. For the adsorption isotherms of the sediment, the so-called '2-step Langmuir/Freundlich models', with the advance of switching functions (Logistic or Arctan functions), were proposed. Then, based on the principle of parsimony, a stepwise model reduction approach was used to choose the optimal models. It was found that the isotherms were used successfully to describe the historical arsenic-contamination data of the past 14 years (2005 - 2019) and to predict future trends qualitatively. [ABSTRACT FROM AUTHOR]

In the geochemical review based on records from cruises of the International Deep Marine Drilling Project (DSDP, ODP, and IODP phases) and other literature data on the main types of Pleistocene sediments in the Atlantic, tables of average arithmetic chemical composition, mean weighted chemical composition, accumulation rates, and mass accumulation rates of chemical components are presented. These tables can be used for the comparative analysis with sediments of the same or other stratons in different oceanic basins, as well as with paleoceanic sediments on the continents. The terrigenous matrix dominates within the lithogenic matter. Using methods of mathematical statistics, we revealed the main geochemical associations and major factors determining the chemical composition of studied sediments. Masses of oxides of petrogenic elements and several trace elements have been calculated for Pleistocene sediments. Average chemical composition of Pleistocene sediments is proposed for the Atlantic. [ABSTRACT FROM AUTHOR]

Despite the significant discovery of hydrocarbon in the Cretaceous Deep-Water Tano Basin of Ghana, detailed molecular characteristics and paleo-depositional environment of the Basin are insufficiently documented in peer-reviewed works. Therefore, in our study, gas chromatography-mass spectrometric (GC-MS) and gas chromatographic (GC) analyses were used to characterize biomarkers obtained from organic matter (oils and rock extracts) to determine the organic matter source, the environment of deposition, and maturity. Sixteen (16) oil and ninety-eight (98) rock samples from seven wells were studied. The work has indicated that distributions of these biomarkers suggested that Cretaceous oils were derived from a mixed kerogen source (marine and terrestrial) deposited in anoxic to suboxic paleo depositional conditions. CPI, Ts/Tm and C29 ββ/(ββ + αα) sterane ratios plotted against C29 20S/(20S + 20R) sterane ratios indicates that the studied samples are relatively low to medium level maturity. [ABSTRACT FROM AUTHOR]

Eelgrass meadows have attracted much attention not only for their ability to maintain marine ecosystems as feeding grounds for marine organisms but also for their potential to store atmospheric and dissolved CO2 as blue carbon. This study comprehensively evaluated the bacterial and chemical data obtained from eelgrass sediments of different scales along the Japanese coast to investigate the effect on the acclimatization of eelgrass. Regardless of the eelgrass habitat, approximately 1% Anaerolineales, Babeliales, Cytophagales, and Phycisphaerales was present in the bottom sediment. Sulfate-reducing bacteria (SRB) were present at 3.69% in eelgrass sediment compared to 1.70% in bare sediment. Sulfur-oxidizing bacteria (SOB) were present at 2.81% and 1.10% in the eelgrass and bare sediment, respectively. Bacterial composition analysis and linear discriminant analysis revealed that SOB detoxified H2S in the eelgrass meadows and that the larger-scale eelgrass meadows had a higher diversity of SOB. Our result indicated that there were regional differences in the system that detoxifies H2S in eelgrass meadows, either microbial oxidation mediated by SOB or O2 permeation via the physical diffusion of benthos. However, since bacterial flora and phylogenetic analyses cannot show bias and/or causality due to PCR, future kinetic studies on microbial metabolism are expected. [ABSTRACT FROM AUTHOR]

Methane release from marine sediments strongly influences the local seafloor environment and ecosystems, and may impact Earth's climate system. Recent studies revealed anomalous molybdenum (Mo) enrichment in seep sediments, which was linked to methane release events. Marine seep sediments are a potential sink of Mo for the global ocean, while the mechanisms leading to local Mo enrichment are not fully understood. The sediments from a gas hydrate-bearing area of the South China Sea analyzed herein reveal authigenic Mo (Mo auth) contents ranging from 0 and 31.4 µg/g and δ98Mo auth values ranging from 0.18 ‰ to 3.31 ‰. The range of δ98Mo auth values of seep sediments is therefore similar to values of modern iron-rich sediments with low concentrations of dissolved porewater hydrogen sulfide and sediments deposited under weakly euxinic sediments. Among the obtained South China Sea data, the more positive δ98Mo auth values (>ca. 1.5 ‰) are interpreted to reflect diffusion of seawater Mo into the sediment at moderate seepage rates and Mo isotope fractionation during the formation of thiomolybdates in the sulfidic seep environment. The lower δ98Mo auth values (

Oxygen minimum zones (OMZ) represent ~8% of the ocean, with the Pacific as the largest and top expanding area. These regions influence marine ecosystems, promoting anaerobic microbial communities. Nevertheless, only a fraction of microbial diversity has been studied, with fungi being the less explored component. So, herein we analyzed fungal diversity patterns in surface and subsurface sediments along a bathymetric transect using metabarcoding of the ITS1 region in the OMZ of the Mexican Pacific off Mazatlán. We identified 353 amplicon sequence variants (ASV), within the Ascomycota, Basidiomycota, and Rozellomycota. Spatial patterns evidenced higher alpha diversity in nearshore and subsurface subsamples, probably due to temporal fluctuations in organic matter inputs. Small-scale heterogeneity characterized the community with the majority of ASV (269 ASV) occurring in a single subsample, hinting at the influence of local biogeochemical conditions. This baseline data evidenced a remarkable fungal diversity presenting high variation along a bathymetric and vertical transects. [ABSTRACT FROM AUTHOR]

It is necessary to predict the critical transition of lake ecosystems due to their abrupt, non-linear effects on social-economic systems. Given the promising application of paleolimnological archives to tracking the historical changes of lake ecosystems, it is speculated that they can also record the lake's critical transition. We studied Lake Dali-Nor in the arid region of Inner Mongolia because of the profound shrinking the lake experienced between the 1300 s and the 1600 s. We reconstructed the succession of bacterial communities from a 140-cm-long sediment core at 4-cm intervals and detected the critical transition. Our results showed that the historical trajectory of bacterial communities from the 1200 s to the 2010s was divided into two alternative states: state1 from 1200 to 1300 s and state2 from 1400 to 2010s. Furthermore, in the late 1300 s, the appearance of a tipping point and critical slowing down implied the existence of a critical transition. By using a multi-decadal time series from the sedimentary core, with general Lotka-Volterra model simulations, local stability analysis found that bacterial communities were the most unstable as they approached the critical transition, suggesting that the collapse of stability triggers the community shift from an equilibrium state to another state. Furthermore, the most unstable community harbored the strongest antagonistic and mutualistic interactions, which may imply the detrimental role of interaction strength on community stability. Collectively, our study showed that sediment DNA can be used to detect the critical transition of lake ecosystems. [ABSTRACT FROM AUTHOR]

This study aimed to assess the influence of pollution on the quality of sediments and the risks associated with El-Qusier and Safaga Cities, Red Sea, Egypt, during 2021, divided into four sectors, using multiple pollution indices. To achieve that, we evaluated the metal pollution index (MPI), contamination factor (Cf), pollution load index (PLI), contamination security index (CSI), and anthropogenicity (Anp%). Moreover, carcinogenic and non-carcinogenic risks are used for human health hazards. Results indicated that Mn and Fe recorded the highest concentrations, whereas Cd had the lowest. El-Quseir City sediments were found the following metal ions: Fe > Mn > Ni > Zn > Cu > Co > Pb > Cd, where the order in the Safaga City was: Fe > Mn > Zn > Ni > Cu > Pb > Co > Cd. MPI > 1, this is alarming in the study area due to heavy metal pollution. In addition, Cf < 1 in all metals except Cd with contamination degree CD ranged from low to considerable contamination in El-Qusier city. In contrast, contamination ranged from significant to very high in Safaga city. PLI < 1 is lower than the reference at all monitored stations. CSI values ranged from relatively low to moderate. Besides Cd, data reflect each element's low environmental danger (EriMe40). This study's risk index (RI) is low to moderate in Sector 1 and high to extremely high in Sector 2. HQ and HI index < 1 means it is safe for human health in order: HI ingestion > HI dermal. CSR for different pathways was recorded as dermal > ingestion, in which total CSR for all paths is considered harmful, and the cancer risk is troublesome and higher than the reference ranges of 1 × 10–6–1 × 10–4. In conclusion, the examined heavy metals provide environmental hazards across the assessed locations. [ABSTRACT FROM AUTHOR]

Hydropower, although an attractive renewable energy source, can alter the flux of water, sediments, and biota, producing detrimental impacts in downstream regions. The Mekong River illustrates the impacts of large dams and the limitations of conventional dam regulating strategies. Even under the most optimistic sluicing scenario, sediment load at the Mekong Delta could only recover to 62.3 ± 8.2 million tonnes (1 million tonnes = 109 kilograms), short of the (100 to 160)-million tonne historical level. Furthermore, unless retrofit to reroute sediments, the dams are doomed to continue trapping sediment for at least 170 years and thus starve downstream reaches of sediment, contributing to the impending disappearance of the Mekong Delta. Therefore, we explicitly challenge the widespread use of large dead storages--the portion of the reservoirs that cannot be emptied--in dam designs. Smaller dead storages can ease sediment starvation in downstream regions, thereby buffering against sinking deltas or relative sea level rises. [ABSTRACT FROM AUTHOR]

The escalating issue of microplastic (MP) pollution poses a significant threat to the marine environment due to increasing plastic production and improper waste management. The current investigation was aimed at quantifying the MP concentration on 25 beaches on the Maharashtra coast, India. Beach sediments (1 kg) were collected from each site, with five replicates to evaluate the extent of MPs. The samples were homogenized, and three 20 g replicas were prepared for subsequent analysis. Later, the samples were sieved, and MPs were extracted using previously published protocols. The abundance of MPs found as 1.56 ± 0.79 MPs/g, ranges from 0.43 ± 0.07 to 3 ± 0.37 MPs/g. Fibers were found as the most abundant shape of MPs. Size‐wise classification revealed dominance of <1 mm and 1–2 mm‐sized MPs. Blue‐ and black‐colored MPs were recorded dominantly. Polymer identification of MPs revealed polyurethane, polypropylene, polyvinyl chloride, acrylic or polymethyl methacrylate, and rubber. The findings revealed that MPs were found to be higher at highly impacted sites, followed by moderately impacted sites and low‐impacted sites, possibly due to a different degree of anthropogenic pressure. The study recommended the urgent need for effective policy to prevent plastics accumulation in the coastal environment of Maharashtra State, India. Practitioner Points: The study investigated the abundance and distribution of microplastics in the marine environment, specifically in sediments.The most common type of microplastic found was fibers, followed by fragments and films.Microplastics were found to pose a potential risk to the marine ecosystem, although further research is needed to fully understand their ecological impact.Future research should focus on expanding the sample size, assessing long‐term effects, exploring sources and pathways, and considering size and shape of microplastics.The findings recommended urgent action to mitigate plastic pollution in Maharashtra coast. [ABSTRACT FROM AUTHOR]

Disposal of dredged sediment from rivers and lakes is an important environmental management issue. Reuse of amended dredged sediment as planting medium for urban greening (PMUG) is a potentially valuable resource management approach. However, risks associated with heavy metals in dredged sediment, as well as its poor permeability and water retention capacity, limit its potential for reuse. In this study, we used dredged sediment to prepare PMUG by alternating aerobic and anaerobic processes, using dredged sediment from Chaohu Lake (China) as raw material. Straw, peat, and biochar were added as auxiliary materials and zeolite and superabsorbent resin as water-retaining agents. Changes in physical and chemical indices of the amended sediment were determined during planting medium preparation. Compared with the original dredged sediments, the addition of straw significantly increased the organic matter, nitrogen, and phosphorus content (p < 0.05). The resulting pH, conductivity, cation exchange capacity, available phosphorus, and available nitrogen of the amended sediments met Standard CJ/T 340-2016, China. The added materials also effectively stabilized the heavy metals in the sediments; the immobilization rates of Cr, Ni, Zn, As, Cd, Pb, Hg, and Cu in the amended sediments were 73–84%, 38–55%, 61–62%, 66–76%, 73–77%, 75–86%, 73–90%, and 43–51%. The addition of peat also significantly increased seed germination. The seed germination index of the amended sediments was >119%, ranging up to 173%. This study provides guidance for preparation of amended dredged sediments for use in urban greening. [ABSTRACT FROM AUTHOR]

Uranium concentrations in the water and bottom sediments along the Uzynbulak creek at the Semipalatinsk Test Site are high, possibly implying anthropogenic contamination. These concentrations were measured by ICP-MS and the environmental mobility of uranium was determined by sequential extraction. Activity concentration in bottom sediments ranged from 20 to 6000 Bq/kg with a median of 156 Bq/kg, while that of water did not exceed 0.4 Bq/l. Uranium accumulated in sedimentary environments, up to 73% of which was bound to Fe and Mn oxides and hydroxides, while isotopic compositions indicated natural uranium. Anthropogenic uranium was not observed in the samples. [ABSTRACT FROM AUTHOR]

This article extracts the Qiantang River tidal bore, analyzing the water environment characteristics in front of the tidal line of the Qiantang River tidal bore and behind it. The Qiantang River tidal bore Index (QRI) was established using HY-1C, HY-1D, and Gao Fen-1 wide field-of-view (GF-1 WFV) satellite data to precisely determine the location and details of the Qiantang River tidal bore. Comparative analyses of the changes on the two sides of the Qiantang River tidal bore were conducted. The results indicate the following: (1) QRI enhances the visibility of tidal bore lines, accentuating their contrast with the surrounding river water, resulting in a more vivid character. QRI proves to be an effective extraction method, with potential applicability to similar tidal lines in different regions. (2) Observable roughness changes occur at the tidal bore location, with smoother surface textures observed in front of the tidal line compared to those behind it. There is a discernible increase in suspended sediment concentration (SSC) as the tidal bore passes through. (3) This study reveals the mechanism of water environment change induced by the Qiantang River tidal bore, emphasizing its significance in promoting vertical water body exchange as well as scouring the bottom sediments. This effect increases SSC and surface roughness. [ABSTRACT FROM AUTHOR]

This article reviews research on sediment flux impacts on the receiving estuary, ports, and society in Cartagena, Colombia. The city hosts both the country's largest touristic and coastal industrial sectors and is home to vulnerable coastal communities whose health and livelihoods are impacted by pollution. These marginalized artisanal fishing communities lack basic water and health services but have finally been recognized in a new intersectoral committee for Cartagena Bay's environmental management. To support the governance of these complex socioenvironmental challenges, the Cartagena Bay Observatory has been developed as a scientific tool to monitor the bay's conditions and forecast the effects of future sediment remediation plans. Cartagena Bay receives large freshwater discharges from the Dique Canal, draining from the 260,000 km2 Magdalena River watershed where 80% of the national population resides. This runoff transports sediment loads of 2.3 Mt/year, dispersing large plumes that affect the marine ecosystems and tourism and make the bay one of the Caribbean's largest sediment‐receiving estuaries. Following decades of watershed deforestation and erosion, the upward trending sediment inputs and accretion of the Dique delta have resulted in deposition rates of 1.8 cm/year, and the need for frequent dredging. Mercury dumped by a chemical industry in the 1970s can be found in concentrations as high as 18.8 μg/g buried below the bay's bottom. Mercury has also been found in the bay's biota and human populations, and so the dredging needed for the port's sustainability thereby presents a health risk by allowing this trapped mercury to surface. This article is categorized under:Science of Water > Hydrological ProcessesScience of Water > Water QualityScience of Water > Water and Environmental Change [ABSTRACT FROM AUTHOR]

The Cambrian pre-salt dolomite sequence in the Tarim Basin is a target zone of great strategic significance for hydrocarbon exploration in the basin. Using the results of the interpretation of 3D seismic data from Lunnan and 2D seismic data covering the whole basin, and based on a synthesis of outcrop data, drilling data, well logs, core data, and thin-section data, and the findings from previous studies, this paper studies the characteristics of the facies of the Middle–Lower Cambrian in the platform area in the Tarim Basin, the formation and evolution of platform margins, and the sedimentary characteristics, lithofacies, and paleogeographic characteristics of the Middle–Lower Cambrian series. Based on the types of lithofacies and the seismic facies analysis, the sedimentary facies of the Middle–Lower Cambrian strata can be classified into the five types. From bottom to top, the Middle–Lower Cambrian have experienced several development stages, including the deposition of continental shelf sediments of the Yuertusi Formation, gently sloping non-rimmed platform margin sediments of the Xiaoerbulake Formation, weakly rimmed platform margin sediments of the Wusongger and Shayilike formations, and strongly rimmed platform margin sediments of the Awatage Formation. In each stage, the platform margin shifted further east relative to its location in the previous stage. Based on these results and previous studies, the lithofacies and paleogeography maps of the Middle–Lower Cambrian in the Tarim Basin are modified, and the implications for hydrocarbon exploration in this area are discussed. [ABSTRACT FROM AUTHOR]

Digesta were collected from the intestines of seven species of bottom‐feeding fish to better understand the role of incidental ingestion of sediment in exposing fish to inorganic contaminants. A composite sediment tracer variable, based on concentrations of Co, Cr, Ni, Ti, V, and Y in digesta and in sediment, was calculated to estimate sediment content of digesta. Concentration factors (mg/kg in digesta divided by mg/kg in sediment) of eight elements of interest were linearly regressed on this tracer variable. The relative importance of sediment ingestion to oral exposure was quantified. Zinc, Cd, and Cu were ingested mainly from sediment‐free food. Arsenic, Cr, Ni, Al, and Pb, in contrast, were ingested mainly from sediment. As an example, 93% of the Ni in digesta from a brown bullhead (Ameiurus nebulosus) was from sediment and only 7% from food. Regressions of Al and Pb in digesta of suckers (Catostomidae) suggested an additional oral source, possibly from oxides coating biotic or abiotic surfaces. Overall, concentrations of 12 of 21 elements studied were positively correlated with sediment content (p < 0.005). Including sediment ingestion as a pathway for bottom‐feeding fish is essential for accurately estimating exposures in toxicological studies. Environ Toxicol Chem 2024;43:1036–1046. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Benthic protist communities, including sand-dwelling dinoflagellates, are still poorly characterized worldwide and there is a lack of knowledge on their diversity and spatiotemporal dynamics. In this study, sediments were obtained from several coastal locations of the German Wadden Sea during the summer months of 2017 and 2018 to determine the diversity and spatiotemporal distribution of sand-dwelling dinoflagellates. The analyses consisted of light microscopy and the metabarcoding of small subunit (SSU) rRNA gene V4 region amplicons. Additionally, SSU rRNA sequences were newly obtained for 15 observed taxa included in a reference database and were used to taxonomically assign the obtained amplicon sequence variants (ASVs). The combination of morphological and molecular approaches allowed a deep characterization of dinoflagellate communities. Seventy-three morphospecies were detected by microscopy, while metabarcoding ASVs (amplicon sequence variants) were assigned to 116 species, resulting in a more comprehensive biodiversity inventory than achieved with either method alone. Pfiesteriaceae, Togula compacta and Thecadinium yashimaense predominated in the different sampling locations. Communities from Wilhelmshaven diverged from the others, consistent with its muddier sediment. A high level of resemblance was determined for the communities from each location, regardless of the sampling month and year, indicating a high summertime stability of benthic communities. Further efforts will be needed to characterize benthic protist diversity, as a first step in obtaining a complete picture of the habitat characteristics and physico-chemical conditions that influence benthic community composition. Metabarcoding and microscopy observations provide complementary results. Much of the diversity of sand-dwelling dinoflagellates is uncharacterized. Benthic dinoflagellate communities were stable at each location in summer. [ABSTRACT FROM AUTHOR]

Polychlorinated Biphenyls (PCBs) are mutagenic, carcinogenic, and persistent organic pollutants of the marine and coastal environment. No previous research has precisely used barnacles as potential PCBs bioindicators in the Caspian sea. The present survey was done to add the PCBs concentrations amongst the barnacle and sediment samples collected from 5 important Iranian ports besides the Caspian sea. Barnacle and sediment samples were collected from Astara, Anzali, Caspian, Kiashahr, and Chamkhaleh ports. Samples were transferred to the laboratory and analyzed for the presence and concentration of PCBs using GC-MS. Eighty different types of PCB were detected in the examined samples. PCBs concentration ranged from 02.00±00.10 to 53.00±00.60 ng/g. PCB-77 (53.00±00.60 ng/g in Chamkhaleh, 53.00±01.20 ng/g in Caspian, 53.00±02.40 ng/g in Anzali, and 53.00±2.7 ng/g in Astara ports) had the highest concentration in barnacle samples. PCB-52 (53.00±00.70 ng/g in Chamkhaleh port) had the highest concentration in sediment samples. PCB-114 had the lowest concentration amongst the barnacle (02.00±00.10 ng/g in Astara port) and sediment (03.00±00.20 ng/g in Anzali port) samples. This study is the first report evaluating the presence and concentration of PCBs in barnacle in the Caspian Sea. The role of barnacles and sediments as biomonitors of PCBs was determined. It seems necessary to set strict rules to prevent pollutants from entering the Caspian Sea. [ABSTRACT FROM AUTHOR]

Around the world the Earth's crust is blanketed to various extents by sediment. For continental regions, knowledge of the distribution and thickness of sediments is crucial for a wide range of applications including seismic hazard, resource potential and our ability to constrain the deeper crustal geology. Excellent constraints on the sediment thickness can be obtained from borehole drilling or active seismic surveys. However, these approaches are expensive and impractical in remote continental interiors such as central Australia. Recently, a method for estimating the sediment thickness using passive seismic data, the collection of which is relatively simple and low cost, was developed and applied to seismic stations in South Australia. This method uses receiver functions, specifically the time delay of the P -to- S converted phase generated at the sediment-basement interface, relative to the direct- P arrival, to generate a first-order estimate of the thickness of sediments. In this work, we expand the analysis to the vast array of over 1500 seismic stations across Australia, covering an entire continent and numerous sedimentary basins that span the entire range from Precambrian to present day. We compare with an established yet separate method to estimate the sediment thickness, which utilizes the autocorrelation of the radial receiver functions to ascertain the two-way traveltime of shear waves reverberating in a sedimentary layer. Across the Australian continent the new results match the broad pattern of expected sedimentary features based on the various geological provinces. We are able to delineate the boundaries of many sedimentary basins, such as the Eucla and Murray Basins, which are Cenozoic, and the boundary between the Karumba Basin and the mineral rich Mount Isa Province. Contrasts in seismic delay time across these boundaries are upwards of 0.4  |$\, \mathrm{s}$|⁠. The delay signal is found to diminish to <0.1  |$\, \mathrm{s}$| for older Proterozoic basins, likely due to compaction and metamorphism of the sediments over time. As an application of the method, a comparison with measurements of sediment thickness from local boreholes allows for a straightforward predictive relationship between the delay time and the cover thickness to be defined. This offers future widespread potential, providing a simple and cheap way to characterize the sediment thickness in underexplored areas from passive seismic data. [ABSTRACT FROM AUTHOR]

This study aimed to explore the spatial distribution, sources, contamination status, speciation, and risks of vanadium (V) in sediments and water from Yundang Lagoon (YL) at Xiamen in China. The concentration of V in YL water exhibited a similar distribution pattern, with an average concentration lower than the Chinese drinking water limit value. The V content in the sediments of various YL sampling sites varied significantly. The average V concentration in sediments was 108.28 mg/kg, ranging from 77.38 mg/kg to 151.20 mg/kg. Speciation investigations revealed that the largest amount of V was bound in the residual fraction, while the acid-soluble fraction had the lowest concentration in sediments. On average, the residual and acid-soluble fractions were 51.82% (ranging from 16.09% to 76.13%) and 1.22% (ranging from 0.16% to 2.60%), respectively. Enrichment factor values suggested minor anthropogenic enrichment of V in sediments. Correlation analysis indicated a weak correlation between silt and clay, while carbonate and Fe showed significant correlations with total V in sediments. This correlation suggests that concentrations of Fe and carbonate could favour V accumulation in YL sediments. Potential ecological risk values suggested no risk of V to aquatic biota in the study area. [ABSTRACT FROM AUTHOR]

• Sediment OP and OC during the outbreak and decline of algal blooms were studied. • The changes in OC and OP in the sediment were synchronous. • Mono-P was the main component of OP during the decline of algal blooms. • The impact of the algal blooms on active OC in sediment was significant. In this study, sediment organic phosphorus (OP) and organic carbon (OC) in Lake Taihu, China, as well as their relationships, were analyzed during the outbreak and decline of algal blooms (ABs) over a five-month field study. The results showed synchronous temporal changes in the sediment OP and OC contents with the development of ABs. In addition, there was a significant positive correlation between the sediment OP and OC (p < 0.01), suggesting simultaneous deposition and consumption during the ABs outbreak. The sediment OP and OC contents decreased significantly at the early and last stages of the ABs outbreak and increased at the peak of the ABs outbreak and during the ABs decline. These temporal variation patterns suggest that the sediment OC and OP contents did not consistently increase during the ABs outbreak, even though algae are an important source of organic matter in sediments. The depletion or enrichment of OC and OP in sediments may also depend on the scale of the ABs outbreak. The obtained results revealed significant differences in the sediment OC and OP contents between the months (p < 0.05). In addition, OP in the sediments was dominated by orthophosphate diester (phospholipids and DNA-P) and orthophosphate monoester during the ABs outbreak and decline, respectively. The active OC contents and proportions in the sediments in the ABs outbreak were significantly lower than those observed in the ABs decline period, demonstrating the significant impacts of the ABs outbreak and decline on the sediment OC and OP in Lake Taihu. [ABSTRACT FROM AUTHOR]

Elemental ratios (δ13C, δ15N and C/N) and carbon and nitrogen concentrations in macrophytes, sediments and sponges of the hypersaline Al-Kharrar Lagoon (KL), central eastern Red Sea coast, were measured to distinguish their sources, pathways and see how they have been influenced by biogeochemical processes and terrestrial inputs. The mangroves and halophytes showed the most depleted δ13C values of –27.07±0.2 ‰ and –28.34±0.4 ‰, respectively, indicating their preferential 12C uptake, similar to C3-photosynthetic plants, except for the halophytes Atriplex sp. and Suaeda vermiculata which showed δ13C of –14.31±0.6 ‰, similar to C4-plants. Macroalgae were divided into A and B groups based on their δ13C values. The δ13C of macroalgae A averaged –15.41±0.4 ‰, whereas macroalgae B and seagrasses showed values of –7.41±0.8 ‰ and –7.98 ‰, suggesting uptake of HCO3– as a source for CO2 during photosynthesis. The δ13C of sponges was –10.7±0.3 ‰, suggesting that macroalgae and seagrasses are their main favoured diets. Substrates of all these taxa showed δ13C of –15.52±0.8 ‰, suggesting the KL is at present a macroalgae-dominated lagoon. The δ15N in taxa/sediments averaged 1.68 ‰, suggesting that atmospheric N2-fixation is the main source of nitrogen in/around the lagoon. The heaviest δ15N (10.58 ‰) in halophytes growing in algal mats and sabkha is possibly due to denitrification and ammonia evaporation. The macrophytes in the KL showed high C %, N %, and C/N ratios, but this is not indicated in their substrates due possibly to a rapid turnover of dense, hypersaline waters carrying most of the detached organic materials out into the Red Sea. The δ13C allowed separation of subaerial from aquatic macrophytes, a proxy that could be used when interpreting paleo-sea level or paleoclimatic changes from the coastal marine sediments. [ABSTRACT FROM AUTHOR]

Carbonate and silicate natural sediments from the gulf of Aqaba-Jordan have been used to study adsorption of nickel(II), lead(II) and cadmium(II) ions, separately, from aqueous solutions. Both sediment types were characterised by FTIR, XRD and SEM. Adsorption of these metal ions were investigated using batch technique as a function of initial concentration of metal cations, adsorbent dosage, initial pH, contact time and temperature. The metal uptake enhanced with increasing pH until a maximum removal at pH 8.0 for Ni, 5.0 for Pb and 6.0 for Cd. Kinetic study shows that the adsorption obeys a pseudo-second-order kinetic model. The adsorption isothermal behaviour of the metal ions uptake onto carbonate and silicate sediments were examined using Langmuir, Freundlich and Dubinin–Radushkevich (D-R) adsorption isotherms. The maximum adsorption capacity obtained by Langmuir isotherm model (25°C) onto carbonate sediments was 2.64, 4.41 and 4.15 mg/g for Ni(II), Pb(II) and Cd(II), respectively. While the adsorption onto silicate sediments was 2.57, 3.56 and 3.15 mg/g, respectively. These adsorption values on carbonate sediments comparing to silicate sediments were attributed to some physical and chemical properties of both sediments, especially the higher permeability and porosity for carbonate sediments. Thermodynamic functions, ΔG*, ΔH* and ΔS* were determined. Negative ΔG* values show that the adsorption process of these metal ions onto both sediments is spontaneous. While the positive ΔH* values indicate that adsorptions are endothermic, and the positive values of entropy ΔS* suggest that the adsorption is driven by increasing of randomness. Conservative calculations using the data in this study and some other from the literature shows that the shallow sediments would adsorb roughly 7 × 10 16 kg of heavy metals that may be introduced into the sea through different anthropogenic activities. [ABSTRACT FROM AUTHOR]

Lake sediment is an effective archive containing information about past climate change, and accurately determining the deposition age of lake sediment is crucial to investigating past environmental variation. To elucidate the historical climate change modes in the northeastern Qinghai-Tibet Plateau (QTP), the sedimentary profile of a paleolake deposit on the western Qilian Mountains was examined. However, the profile exhibits notable age reversals due to the reservoir effect, as determined by analyzing 46 accelerator mass spectrometry carbon-14 (AMS 14C) dates of bulk organic matter. We therefore conduct a comprehensive examination of carbon-related indicators, including total organic carbon content (TOC), carbon/nitrogen ratio (C/N), and organic carbon isotope (δ13C). And combining with the changing patterns of them in topsoil samples around the northeastern QTP, this study determines that the formation age of the lacustrine sedimentary profile is 16278∼20662 cal a BP, corresponding to the Last Glacial Maximum (LGM) and the last deglaciation. The results of sedimentary facies identified by grain size and carbonate oxygen isotope (δ18O) suggest that this profile was developed near the paleolake shoreline, resulting from a transition in lake environment from deep to shallow during the LGM and the last deglaciation. The corresponding reconstructed lake area and precipitation are 642 km2 and 238 mm, respectively, indicating a wet and cold climate mode in the northeastern QTP during this time. Furthermore, the wetter state in the northeastern QTP can be attributed to a combination of reduced evaporation caused by colder conditions and enhanced precipitation driven by stronger southerly westerly jet streams. [ABSTRACT FROM AUTHOR]

The upper layer of bottom sediments in the northeastern Kara Sea is studied. It is shown that the sediment composition is dominated by silt, while the percentage of sand increases towards the coast. The organic carbon content (average value 1.1 wt %) is close to the average content in Kara Sea sediments, increasing at deep-sea stations. The linear correlation found between the organic carbon content and surface area of sediments shows adsorption on particle surfaces and is the predominant form of organic matter (OM) accumulation in the sediments. The average n-alkane concentration in the analyzed samples is 1.1 μg/g of sediment; the distribution spectrum is dominated by odd high-molecular homologues of terrigenous origin. [ABSTRACT FROM AUTHOR]

The sources of supply and transformation of organic matter (OM) as it transitions from dissolved form to particulate matter, fluffy layer, and bottom sediments were investigated along a meridional transect from the Lena River delta to the continental slope (in the depth range of 10 to 2390 meters, cruise 63 of the R/V Akademik Mstislav Keldysh, September 2015). The study of OM molecular markers showed that dissolved and particulate organic matter of marine and terrigenous origin biodegrades in the water column and accumulates insignificantly in bottom sediments. Thus, OM from Lena River runoff does not contribute to the formation of OM in bottom sediments in summer. An area of influence of under-ice blooms on the sedimentation process was identified on the outer shelf. [ABSTRACT FROM AUTHOR]

Sediment movements on the riverbeds are crucial in fluvial processes. Therefore, studying incipient sediment motion is valuable for predicting changes in sediment behavior. In this study, the influence of aquatic vegetation is introduced into the momentum balance equation under the condition of a bare bed. The presented model for incipient sediment motion in open channels covered by vegetation is derived, in consideration of vegetation density and relative submergence. This study simplifies the model format. The model and its coefficients demonstrate good applicability to various working conditions without requiring numerous changes. The predicted velocity determined by the proposed model is validated against experimental data. Results show excellent agreement between the two in various scenarios, including combinations of rigid or flexible conditions and submerged or emergent states. Additionally, the velocity for incipient sediment motion is observed to decrease with increasing vegetation density. However, a further increase in vegetation density may amplify vegetation resistance, hindering incipient sediment motion. Meanwhile, sediment movement becomes challenging as water depth increases, assuming that flow discharge and vegetation conditions remain constant. [ABSTRACT FROM AUTHOR]

Summary: The order Boraginales of the Lamiids clade encompasses a diverse group of plants that currently has a global distribution. Its fossil record is scanty. Herein we report a fossil wood of Cordia L. of the family Cordiaceae from the Tipam Sandstone (late Miocene) sediments of Assam, northeast India. This finding not only throws light on the phytogeography and diversification of the Cordiaceae, but also provides valuable insights into the Neogene vegetation of the region. [ABSTRACT FROM AUTHOR]

Gases from bottom sediments of the Laptev–Siberian Sea zone contain methane (up to 8.3047 cm3/kg) and its homologues (up to pentane including) totaling 0.0259 cm3/kg. The established values of the carbon isotope composition of methane (δ13С), the molecular weight of the hydrocarbon fraction, the weight concentrations of С1–С5 hydrocarbons and their ratios, the "wetness" and "transformation" coefficients of the hydrocarbons fraction indicate the presence of various syngenetic and epigenetic gases in different source rocks: bottom sediments, peatlands, coal, gas, and gas hydrate? deposits, solid bitumen, igneous rocks, and inferred oil and gas reservoirs. It has been established that the vertical and lateral distribution of hydrocarbon gases in sediments depends on the influence of a complex of geological factors: fold and fault tectonics, magmatism and seismic activity in the region, coal, oil and gas potential and bitumen content, organic saturation and lithological composition, hydrogeological, geocryological, and other conditions for accumulation of gases or their degassing. [ABSTRACT FROM AUTHOR]

Recent research has produced data useful in inferring burial depths for sandstones from compaction microtextures. Burial depths can also be inferred from erosional remnants and coal rank, among other means. These methods are especially useful over generally horizontal plains when other methods are unavailable to provide minimum overburden depths. That immense amounts of erosion occurred in the study area has long been recognized, but no effective lithification model has been available whereby to estimate burial depths or diagenetic environments. In this paper, we present research from the northern Great Plains focused on sandstones in an effort to develop a semi-quantitative lithification model for estimating initial overburden thickness (burial depth) and conditions of lithification. While development of such a model eludes us, approximations are possible and can be very helpful in studying Earth history. [ABSTRACT FROM AUTHOR]

Carbonate-bearing sediments, containing calcite, dolomite or magnesite as major carbonate components, are important constituents of sedimentary sequences deposited on passive margins through Earth's history. When involved in collisional orogenic processes, these sediments are metamorphosed at variable temperatures and pressures, and undergo decarbonation reactions. While the orogenic metamorphism of some of these lithologies (i.e. impure limestones and dolostones, marls sensu stricto and calcareous pelites) is relatively well understood, very little is known about the metamorphic evolution and decarbonation history of mixed carbonate–silicate rocks in which either dolomite or magnesite is the dominant carbonate component. Here we present the results of a petrologic study of representative samples of metasediments from Central Nepal, derived from Proterozoic dolomitic and magnesitic protoliths metamorphosed during the Himalayan orogeny. The main metamorphic assemblages developed in sediments originally containing different amounts of dolomite or magnesite are characterised in detail. Forward thermodynamic modelling applied to seven samples allows constraints to be placed on (i) the main decarbonation reactions, (ii) the P–T conditions under which these reactions took place, (iii) the composition of the fluids, and (iv) the amounts of CO2 released. We conclude that the CO2 productivity of dolomitic and magnesitic pelites and marls originally containing 15–40% carbonate is significant (>5.5 ± 1.0 CO2 wt% and up to 10.5 ± 1.5 CO2 wt%), whereas for carbonate contents above 60–70%, CO2 productivity is negligible unless aqueous fluids infiltrate from the outside and trigger decarbonation reactions. Since the dolomitic and magnesitic protoliths are significantly abundant in the sedimentary sequences involved in the still active Himalayan orogen, the decarbonation processes described here could contribute to the diffuse CO2 degassing currently observed at the surface. Furthermore, we propose for the first time that the peculiar magnesium-rich assemblages investigated in this study may derive from evaporitic protoliths, and that the whole Upper Lesser Himalayan Sequence may therefore represent the metamorphic product of a Proterozoic sequence consisting of alternating layers of carbonatic, evaporitic and pelitic sediments. [ABSTRACT FROM AUTHOR]

The isotopic ratio 18O/16O of dissolved O2 in aquatic systems is affected by the preferential biological uptake of 16O (ε). Studies over the past six decades reveal that during incubation experiments, the isotopic effect of microorganism respiration (εorganism) varies in the range of −18‰ to −22‰. In contrast, natural variations in the deep‐ocean O2 concentration and δ18O levels show a considerably weaker effect (~ −10‰). The differences between these observations have been explained to result from either O2 uptake by sediments or organic particles that, due to diffusion‐limited respiration, are expected to weakly fractionate oxygen isotopes, by mixing processes or by weak fractionation at low temperatures. To gain better insight, we studied oxygen demand and δ18O in the deep, cold hypolimnion of Lake Stechlin between 2018 and 2021 as well as in various laboratory incubations. Our incubation results demonstrate an εorganism of about −24‰. Simple model calculations demonstrate a sediment O2 demand isotope effect (εSOD) of about −8.4‰, and a variated water‐column O2 demand isotope effect (εWOD) which is lower than εorganism, ranging from −13.9‰ in 2019 to −23‰ in 2021. Accompanying experiments indicate that the lower magnitude of εWOD may be related to respiration at organic particles lending to a weaker fractionation effect. Thus, variations in εWOD may reflect a changing partitioning of hypolimnion oxygen uptake between suspended particles and their containing microorganisms. Based on own incubation experiments with Daphnia carcasses, we discuss how possible changes of particle rigidity might influence εWOD. [ABSTRACT FROM AUTHOR]

Feeds based on small (trash) fish contain much persistent phosphorus (P), such as Ca bound (Ca-P) and refractory P (Ref-P), which accumulates in high concentrations in the bottom sediments immediately below fish farms using this type of feed. This study designated three sampling locations based on their history concerning yellowtail fish farming (current, formerly or never) to investigate the sediment vertical distribution of phosphorus fractions and to test for detection of P impact on the bottom sediment. The aquaculture-free site was relatively low in Ca-P and Ref-P compared with continuous and previous aquaculture sites. The latter had high Ca-P and Ref-P content only in the depth range 17–29 cm, coinciding with the period during which aquaculture was conducted (1960–1998). The techniques used are expected to be useful to indicate bottom condition improvements and as a tracer of the effects of previous aquaculture farming. [ABSTRACT FROM AUTHOR]

Infilled lakes are a prevalent geomorphic feature in the intricate high mountain landscape of the Cordillera Blanca, Peru. Despite their apparent geomorphic, hydrological, and ecological importance, a systematic inventory of these areas has been lacking. This study presents an inventory of infilled lakes in the Cordillera Blanca. A total of 962 infilled lake polygons have been manually mapped, covering an area of nearly 90 km2 (the area of individual mapped polygons ranges from 0.001 km2 to 1.760 km2), more than double the area of existing lakes (40 km2) and the majority of flat areas (62% of areas with slope ≤5°). The study reveals that infilled bedrock-dammed lakes are the most common type (42%), while moraine-dammed lakes account for the majority of the infilled lake area (52%) and sediment volume (52% to 57%). Considering high uncertainty of infilled basins' morphology, the estimated sediment volume of infilled lakes ranges between 0.9 km3 and 2.3 km3 (compared to 0.79 km3 to 1.15 km3 of water stored in existing lakes). The case study of Lake Aguascocha catchment reveals a mean sediment yield of 0.64 to 1.63∙106 m3∙km−2 during the past 10.7 ± 0.3 ka, that is, a mean annual sediment yield of 58.5 to 156.4 m3∙km−2∙yr−1. Furthermore, 65 locations where preserved geomorphic evidence indicates possible outburst floods in the past are identified. These areas are particularly important for understanding patterns of lake outburst occurrence on longer timescales than traditionally considered in lake outburst flood hazard studies. The dataset presented in this study is intended to serve as a basis for identifying sites suitable for further site-specific paleo-geographical, sedimentological, geochronological as well as broader mountain landscape evolution studies. [ABSTRACT FROM AUTHOR]

The study investigated the sorption behaviour of 99Tc and 125I on bottom sediments from the Japan Sea, Khanka Lake and commercially available sapropel. It was determined that organic matter can have an impact on the iodine sorption process. After a 20-day period, sapropel reached an equilibrium state with a sorption value of up to 100%. In real systems of bottom sediment–water in the Far East region, iodine sorption was found to be superior on marine bottom sediments with a sorption value reaching 85% within 20 days, as opposed to freshwater sediments which only reached up to 35% within the same period. Tc(VII) in the form of pertechnetate anion exhibits no sorption under either aerobic or anaerobic conditions in the pH range of 4–11. Under aerobic conditions at pH 11 Tc(IV) is sorbed up to 15% only on sapropel; under anaerobic conditions at pH 7 the sorption reaches 25% for lake sediments, 10% for marine sediments and when the pH is 11, the sorption value of Tc by sapropel is as high as 100%. [ABSTRACT FROM AUTHOR]