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To date, seasonal dynamics of the denitrifying bacterial community in floodplain lakes is unknown. Here, we investigated the alpha diversity, abundance and composition of the sediment nirS-type denitrifying bacteria in Poyang Lake during the wet, mid-dry and dry seasons using Illumina MiSeq sequencing and quantitative polymerase chain reaction assay. The results showed that only a small part of the total operational taxonomic units (OTUs) were shared by the three seasons. OTU richness, Chao richness estimator and Shannon index exhibited higher values in the wet season than in the dry season. Some regular patterns of variation in the composition of the nirS-type denitrifying community at three classification levels (phylum, class and genus) were found among seasons. Community structures of nirS-type denitrifying bacteria were significantly different across seasons. In addition, the abundance of nirS gene showed no seasonal pattern. Total nitrogen, total phosphorous and pH were the most significant factors elucidating the compositional variation of the nirS-type denitrifying community. This study provided a new evidence for the ecological effects of seasonal water level fluctuations and improved our understanding of the nitrogen removal processes in floodplain lakes. [ABSTRACT FROM AUTHOR]

Paleoenvironmental archives in East Antarctica have revealed significant changes during the Holocene, marked by ice sheet retreat leading to the isolation of submarine basins. These basins offer valuable insights into past climate, glaciology, and oceanography shifts that impact sedimentary processes. In this study, environmental magnetism and biogeochemical proxies to investigate the Mid-to-Late-Holocene transitions in Pup Lagoon, a coastal isolation basin is presented. Our findings reveal distinct stratigraphic zones reflecting shifts from marine to lacustrine environments. The results reveal predominant mechanical weathering in the Stornes region, producing coarse-grained "soft" ferrimagnetic minerals. Notably, a period of warm oceanographic conditions between 6000 and 4722 cal. yr BP was characterized by mixed magnetic grain sizes and ultrafine superparamagnetic grains, indicating relatively oxic open waters in the basin. Subsequent shifts to reducing conditions coincide with persistent marine sea ice cover from 4722 to 2634 cal. yr BP, favoring the retention of coarse-grained ferrimagnets. Finer magnetic grain sizes between 2634 and 2185 cal. yr BP was attributed to the increased freshwater inputs associated with the Mid-Holocene Hypsithermal. Further, diagenetic changes under persistent sea ice cover between 2185 and 1970 cal. yr BP led to the selective dissolution of fine-grained ferrimagnets. Transitioning to freshwater isolated basin conditions between 1970 and 588 cal. yr BP, fine ferrimagnet precipitation indicate oxic to suboxic conditions alongside drier conditions. Biogenic productivity increased post-isolation, which was reflected in increased (Total Organic Carbon) TOC and (Total Nitrogen) TN percentages. Additionally, the presence of greigite in the isolated phase sediment indicates reducing conditions owing to organic matter decomposition. Notably, χfd% exhibits an inverse trend to sea ice concentration, potentially indicating anoxic-dysoxic conditions due to the presence of sea ice. These observations align with broader regional sea ice concentration changes, emphasizing the interconnected behavior of local and regional factors shaping Antarctic coastal environments. [ABSTRACT FROM AUTHOR]

AMS radiocarbon-dated palynological evidence from Embilikala Lagoon in Bundala National Park (one of the Ramsar wetland sites) on the southeast coast of Sri Lanka indicates palaeoenvironmental changes during the last 2,700 years. The persistence of fewer mangroves (eg Rhizophoraceae taxa) suggests that sea level low stands occurred between 2,700 and 1750 cal yr BP. From the later age, the relative sea level rose, and reached the present sea level at 950 cal yr BP as indicated by the mangrove maximum. At 2,250, 700–400 and 200–150 cal yr BP, the sudden increase in marine dinoflagellate cysts (eg Spiniferites mirabilis) and foraminifera (Globigerinoides ruber) suggests increased marine influence. This is consistent with a decrease in mangrove habitats. Between 2,700 and 950 cal yr BP, severely degraded dry monsoon forests and minimal levels mangrove suggest human and marine influences were the critical drivers for changing the major vegetation types along the southeastern coast. Vegetation changes have been drastic over the last millennia. [ABSTRACT FROM AUTHOR]

Seas worldwide are threatened by an emerging source of pollution as millions of tons of warfare materials were dumped after the World Wars. As their metal shells are progressively corroding, energetic compounds (EC) leak out and distribute in the marine environment. EC are taken up by aquatic organisms and pose a threat to both the marine ecosphere and the human seafood consumer because of their toxicity and potential carcinogenicity. Here, sediment samples and fish from different locations in the German North Sea of Lower Saxony were examined to determine whether EC transfer to fish living close to munition dumping areas. EC were found in sediments with a maximum concentration of 1.5 ng/kg. All analyzed fish muscle tissues/fillets and bile samples were positive for EC detection. In bile, the max. EC concentrations ranged between 0.25 and 1.25 ng/mL. Interestingly, while detected TNT metabolites in the muscle tissues were in concentrations of max. 1 ng/g (dry weight), TNT itself was found in concentrations of up to 4 ng/g (dry weight). As we found considerable higher amounts of non-metabolized TNT in the fish muscle, rather than TNT metabolites, we conclude an additional absorption route of EC into fish other than per diet. This is the first study to detect EC in the edible parts of fish caught randomly in the North Sea. [ABSTRACT FROM AUTHOR]

The potential threat of fisheries on seabed carbon is a topic of growing concern, yet existing literature presents inconsistencies leaving experts divided on the topic. We conducted a global meta‐analysis to synthesize the current knowledge and quantify how demersal fishing impacts various biogeochemical properties. Direct impact studies revealed overall reductions in chlorophyll‐a (Chl‐a, 17%), phaeopigments (24%), and proteins (32%). Effects on these reactive compounds were more pronounced on surface sediment (0–2 cm), where the impact on total organic carbon (TOC) also became significant, demonstrating the effect of gear penetration, and highlighting that sampling strategies combining sediment layers can mask observed effects. Current velocity and primary productivity significantly influenced the direction and magnitude of fishing impacts. Trawling‐induced subsurface reductions of TOC in low‐energy habitats may affect carbon sequestration due to the preferential removal of semi‐reactive carbon. Intriguingly, fishing intensity gradient studies showed an average increase in TOC in chronically fished areas, possibly reflecting fishing preferences for meso‐eutrophic grounds. We estimate a ~300‐day recovery period post‐fishing for Chl‐a, though values for other parameters are less certain. Limited data on seasonality, gear types, and an under‐representation of studies in tropical and deep‐sea areas pose challenges to quantifying global scale geochemical impacts of demersal fisheries. Knowledge gaps persist in understanding the fate of disturbed organic matter including its mineralization, transport, and sequestration. Nonetheless, our insights and estimates provide foundational knowledge that can contribute to science‐based approaches for spatial fisheries management while preserving natural carbon dynamics on the seabed. [ABSTRACT FROM AUTHOR]

Heavy metals (HMs) contamination in sediment presents a straightforward issue, particularly noticeable in developing nations. Addressing this problem requires an extensive inquiry into the present situation and potential remedies to keep safe environment. This document compiles statistical procedures concerning various heavy metals such as chromium (Cr), nickel (Ni), copper (Cu), cadmium (Cd), lead (Pb), and arsenic (As) that are available in sediments from Bangladesh spanning the years from 1998 to 2021. The average levels of Ni, Cu, Cd, Pb, and As in sediments of the available data exceeded the corresponding background values, upper continental crust values, and toxicity reference values, indicating severe contamination of sediment by heavy metals. Metal concentrations (Cr, Ni, Cu, and As) generally remained lower than the average shale values, except for Cd and Pb. By utilizing the Pearson correlation coefficient (CCA) and principal component analysis (PCA), it was evidenced that human activities, apart from natural ecological factors, stand as the primary sources of heavy metal pollution in sediment from Bangladeshi waterways. Cd emerged as the key contributor to heightened contamination levels in riverine sediments, as indicated by pollution indices, signifying an ecological hazard. Overall, the data underscored the significant ecological risk posed by the considered hazardous metals. To mitigate sediment heavy metal levels, strategies such as reducing heavy metal discharges at their origins and implementing phytoremediation techniques in sediment, along with improving effluent treatment facilities, could aid in alleviating the issue. [ABSTRACT FROM AUTHOR]

Sediment is the ultimate sink of environmental pollutants. A total of 128 surface sediment samples were collected from 8 rivers and 3 reservoirs in Maoming City, Guangdong Province. This study assessed the content and distribution of brominated flame retardants in sediments. The acute toxicity effects of tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDs) in sediments were evaluated using Caenorhabditis elegans as model organisms. The concentration of TBBPA in sediments ranged from not detected (ND) to 12.59 µg/kg and was mainly distributed in the central area, which was affected by the emission of TBBPA from residential and factory. The concentration of HBCDs ranged from ND to 6.31 µg/kg, and the diastereoisomer distribution was consistent, showing a trend close to the South China Sea. The composition pattern of HBCDs in the surface sediments from rivers were 41.73%–62.33%, 7.89%–25.54%, and 18.76%–40.65% for α-, β-, and γ-HBCD, respectively, and in the sediments from reservoirs were 26.15%–45.52%, 7.44%–19.23%, and 47.04%–61.89% for α-, β-, and γ-HBCD, respectively. When the sum of concentrations of TBBPA and HBCD in sediments were above high levels, reactive oxygen species in nematodes significantly increased, resulting in an oxidative stress response. Intestinal permeability was also enhanced, causing intestinal damage. In addition, in terms of this study, TBBPA had a greater impact on biotoxicity compared to HBCDs, and more attention should be paid to the toxic effects of the river ecosystem organisms in Maoming City, Guangdong Province. This study can complement the pollution database in the study area and provide basic data for pollution control. [Display omitted] [ABSTRACT FROM AUTHOR]

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Based on the virtual soil pile model, this study investigates the torsional vibration of rock-socketed piles while considering the influence of bottom sediment. First, the bottom sediment is perceived as a virtual soil pile, however, its parameters are still determined according to the characteristics of the sediment. The pile, along with the virtual soil pile, is partitioned vertically into numerous segments in accordance to the stratified characteristics of the rock and soil around the pile. To account for the radial inhomogeneity arising from construction disturbance, the surrounding soil is divided into multiple annular zones characterized by progressively varied soil properties in the radial direction. The governing equations which delineate the soil-pile system under torsional dynamic loading are subsequently formulated and solved to yield an analytical solution for pile complex impedance. After ensuring reliability, the established analytical solution is employed to examine the coupling effect of bottom sediment parameters, pile parameters, and construction disturbance on the torsional vibration characteristics of rock-socketed piles. [ABSTRACT FROM AUTHOR]

The Omo River flows through the town of Omorate, where domestic, municipal, and industrial wastes from the town and its surroundings, including agrochemicals, are discharged into the river. The present study was conducted to determine the levels of heavy metals and associated environmental and human health impacts from the Lower Omo River freshwater ecosystem (water and sediment) of the Lower Omo River. The mean concentrations of heavy metals detected in the river water were 0.439 mg/l for (Mn), 0.1 (Zn), 0.168 (Cu), 0.393 (Cr), 0.318 (Pb), 0.007 (Ni), 8.926 (Fe), and 0.06 (Co).The order for the mean concentrations of the heavy metals in the water was Fe > Mn > Cr > Pb > Cu > Zn > Cu > Co > Ni. The HPI value indicates that all water sampling sites were highly contaminated. Oral and dermal HQs for both children and adults were in the order of Cr > Pb > Mn > Fe > Cu > Co > Ni > Zn. The HQ value greater than 1 was investigated for Cr, Pb, and Mn in both children and adults by ingestion and dermal routes from the river water. The CRs for both children and adults by ingestion of the river water followed the order Cr > Pb. According to the CRI value, the river water could be classified as a very high environmental risk. The EI results for the heavy metals detected in the sediments also followed the order: Fe > Cr > Cu > Pb > Mn > Co > Zn > Ni. [ABSTRACT FROM AUTHOR]

The process of dredging reservoirs serves the purpose of preserving water storage capacity and ensuring the functionality of navigational channels. Additionally, it has the potential to mitigate the presence of pollutants and chemicals that pose risks to both the environment and human well-being. This review article examines the many ways of disposal and treatment of dredged sediment, as well as the ecological and economic advantages associated with these approaches. Algae and reed-based treatment methods have the potential to effectively and economically remediate and sustainably manage dredged sediments. Landfills and ocean dumping are widely utilized methods for the disposal of excavated materials. However, other approaches such as land reclamation, the use of fill material, and the preservation of wetlands can offer cost-effective solutions while also contributing to environmental conservation. The implementation of sediment cleaning, stabilization, and solidification techniques has the potential to effectively mitigate waste and improve the quality of sediment, hence facilitating its reuse. Algae and reed-based treatment systems have been found to effectively mitigate disposal costs and contribute to environmental enhancement. Additionally, the practice of reusing dredged sediments has been recognized as a valuable strategy in promoting a circular economy. [ABSTRACT FROM AUTHOR]

Vertical stratification in marine sediment profiles indicates physical and chemical sedimentary processes and, thus, is the first step in sedimentary research and in studying their relationship with global climate change. Traditional technologies for studying vertical stratification have low efficiency; thus, new technologies are highly needed. Recently, visible and near-infrared spectroscopy (VNIR) has been explored to rapidly determine sediment parameters, such as clay content, particle size, total carbon (TC), total nitrogen (TN), and so on. Here, we explored vertical stratification in a sediment column in the South China Sea using VNIR. The sediment column was 160 cm and divided into 160 samples by 1 cm intervals. All samples were classified into three layers by depth, that is, 0–50 cm (the upper layer), 50–100 cm (the middle layer), and 100–160 cm (the bottom layer). Concentrations of TC and TN in each sample were measured by Elementa Vario EL III. Visible and near-infrared reflectance spectra of each sample were collected by Agilent Cary 5000. A global model and several classification models for vertical stratification in sediments were established by a Support Vector Machine (SVM) after the characteristic spectra were identified using Competitive Adaptive Reweighted Sampling. In the classification models, K-means clustering and Density Peak Clustering (DPC) were employed as the unsupervised clustering algorithms. The results showed that the stratification was successful by VNIR, especially when using the combination of unsupervised clustering and machine learning algorithms. The correct classification rate (CCR) was much higher in the classification models than in the global model. And the classification models had a higher CCR using K-means combined with SVM (94.8%) and using DPC combined with SVM (96.0%). The higher CCR might be derived from the chemical classification. Indeed, similar results were also found in the chemical stratification. This study provided a theoretical basis for the rapid and synchronous measurement of chemical and physical parameters in sediment profiles by VNIR. [ABSTRACT FROM AUTHOR]

In this study, we reported a Gram-stain-negative, ovoid to rod-shaped, atrichous, and facultative anaerobe bacteria strain named YMD61T, which was isolated from the intertidal sediment of Yangma island, China. Growth of strain YMD61T occurred at 10.0–45.0 °C (optimum, 30.0 °C), pH 7.0–10.0 (optimum, 8.0) and with 0–3.0% (w/v) NaCl (optimum, 2.0%). Phylogenetic tree analysis based on 16 S rRNA gene or genomic sequence indicated that strain YMD61T belonged to the genus Fuscovulum and was closely related to Fuscovulum blasticum ATCC 33,485T (96.6% sequence similarity). Genomic analysis indicated that strain YMD61T contains a circular chromosome of 3,895,730 bp with DNA G + C content of 63.3%. The genomic functional analysis indicated that strain YMD61T is a novel sulfur-metabolizing bacteria, which is capable of fixing carbon through an autotrophic pathway by integrating the processes of photosynthesis and sulfur oxidation. The predominant respiratory quinone of YMD61T was ubiquinone-10 (Q-10). The polar lipids of YMD61T contained phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, five unidentified lipids, unidentified aminolipid and unidentified aminophospholipid. The major fatty acids of strain YMD61T contained C18:1ω7c 11-methyl and summed feature 8 (C18:1ω 7c or/and C18:1ω 6c). Phylogenetic, physiological, biochemical and morphological analyses suggested that strain YMD61T represents a novel species of the genus Fuscovulum, and the name Fuscovulum ytuae sp. nov. is proposed. The type strain is YMD61T (= MCCC 1K08483T = KCTC 43,537T). [ABSTRACT FROM AUTHOR]

Eriocheir sinensis is the main aquaculture species in China. With the continuous expansion of the aquaculture scale, the demand for E. sinensis seedlings was also increased. The water used in breeding has well-nourished and its discharge into the sea posed significant risks. This study sampled the wastewater discharge points of the E. sinensis seedlings in Sheyang County, Jiangsu Province, and the areas far from the discharge points that were not affected in March and May 2023, respectively. A large number of antibiotic resistance genes (ARGs) were found in the sediment of the wastewater discharge area, and the highest ARG was sulfonamide ARG-sul1 using qPCR analysis, while ARGs were almost undetectable in the areas not affected by wastewater discharge. The 16S rRNA sequence analysis results showed that the main bacterial phyla at the wastewater discharge point were Bacteroidetes, Proteobacteria, and Thermodesulfobacteria. In the control point, the main bacterial phyla were Proteobacteria, Chlorobacterium, and Thermodesulfobacteria. There were significant differences in the composition of microbial communities between the two points, and the samples at the wastewater discharge point were more clustered and had higher similarity. The correlation network and redundancy analysis indicated that the phyla Bacteroidetes, Firmicutes, and Proteobacteria at the wastewater discharge points were positively correlated with most ARGs. The wastewater discharge had no effect on heavy metals from the two points. This study sets a foundation for future research by identifying key microbial taxa as potential ARG carriers and examining the interactions between microbial communities, ARGs, and heavy metals. [ABSTRACT FROM AUTHOR]

The recent expansion of the aquaculture industry into the offshore marine environment is perceived to have a comparatively low environmental impact coupled with a high growth potential as a sustainable, large‐scale source of healthy protein. This study assessed changes in sediment characteristics and infauna assemblages following the development of the first large‐scale offshore longline mussel farm in the United Kingdom. By evaluating the effects of the farm on the sediment ecosystem and by studying infaunal sediment environmental parameters along a distance gradient away from the farm, the first before–after control–impact (BACI) study of an offshore shellfish farm is presented. Sediment grabs from the farm and control sites were analysed for sediment parameters (organic matter content (OM), particle size (PS), oxidation–reduction or redox potential (ORP) and trace elements) and infauna assemblages. There was no difference in sediment organic matter levels between the farm and control sites. Within the farm, the mean sediment grain size and ORP increased over time. Trace element concentrations were the lowest within farm sites compared to outside; concentrations increased with increasing distance from the farm. A total of 76 benthic macrofauna taxa were identified, with polychaetes being the dominant class. Over time, the number of taxa significantly increased within the farm while remaining relatively constant in control samples. Biodiversity metrics, including abundance and Shannon and Pielou's index, were all greater within the farm compared to control areas. Overall, measures of assemblage health were higher within the farm than outside. This study demonstrates the long‐term aquaculture–environment interactions that offshore shellfish farming can have on the seabed and its significance in terms of ecosystem services. [ABSTRACT FROM AUTHOR]

The presence of polycyclic hydrocarbons (PAHs) and microplastics (MPs) in aquatic environments affects the ecosystems and threatens human health. In this study, the abundance, composition, and morphological characteristics of MPs were determined for the first time in the inland freshwater resources of the Konya Closed Basin, Turkey. The abundance of MPs ranged from 1139 to 23,444 particles/m3 and 150 to 3510 particles/kg in the surface water and sediment, respectively. Fragments and fibers were the most abundant MP shapes in the surface waters (51%, 34%) and sediments (29%, 40%), followed by films, pellets, and foams. Transparent and white MPs were present at the highest percentage in surface waters (72%) and sediments (69%), followed by blue, grey, black, brown, and green. In addition, polyethylene, polypropylene, and cellophane were identified as the main polymers in surface waters (34%, 25%, 24%) and sediments (37%, 17%, 31%). In the Konya Closed Basin, 35% of the surface water samples and 54% of the sediment samples were exposed to very high contamination (CF ≥ 6). Surface waters (PLI: 2.51) and sediments (PLI: 1.67) in the basin were contaminated (PLI > 1) with MPs. The 16 PAHs sorbed on MPs in the surface water and sediment ranged from 394 to 24,754 ng/g and from 37 to 18,323 ng/g, respectively. Phenanthrene and fluoranthene were the most abundant PAHs sorbed on MPs in all surface waters and sediments. Two to three-ring PAH compounds sorbed on MPs were also dominantly detected in surface waters and sediments, accounting for 68% and 78% of the total 16 PAHs, respectively. The source of PAHs carried by MPs in the Konya Closed Basin was mainly of petrogenic origin. Incremental lifetime cancer risk (ILCR) results indicated that the maximum ILCR values were higher than the EPA acceptable level (10−6) for child (2.95 × 10−5) and adult (1.46 × 10−4), indicating a potential cancer risk. [ABSTRACT FROM AUTHOR]

Submerged plants and related disturbances can affect both the phosphorus (P) release and the microbial communities in sediments. In this study, a sediment resuspension system was constructed, and P variability characteristics influenced by Vallisneria natans (V. natans) and the response mechanism of the microbial community were studied. The results indicated that the total phosphorus (TP) content increased from 678.875 to 1019.133 mg/kg and from 1126.017 to 1280.679 mg/kg in sediments and suspended solids (SSs) during the sediment resuspension process, respectively. Organic P (OP) increased by 127.344 mg/kg and 302.448 mg/kg in sediments and SSs after the disturbance, respectively. The microbial communities in the sediments and the leaves of V. natans had higher Chao values after the disturbance, while Shannon values decreased after the disturbance compared to the control in SSs. Proteobacteria had the highest abundance with the value of 51.1% after the disturbance in the sediments and SSs, and the abundance values of Proteobacteria in rhizomes and leaves of V. natans could reach 73.2% on average. Chloroflexi, Acidobacteria, and Firmicutes were also the main phyla in the sediment resuspension system. Sodium hydroxide extractable P (NaOH-P) in sediments could reduce the bioavailability of this P fraction under disturbance conditions. The decrease in the abundance of Bacteroidetes and Nitrospirae indicated that they were more sensitive to the disturbance, and the rotational speed changed the survival conditions for the Bacteroidetes and Nitrospirae. The response mechanism of microbial community during the sediment resuspension process could reflect the influence of the microbial community on the changing characteristics of P and could provide a theoretical foundation for P control at the micro level. [ABSTRACT FROM AUTHOR]

Clostridioides difficile is an intestinal pathogen of humans and animals. In community-associated infections, the environment is suggested to play a significant role in overall transmission routes. Although the prevalence of C. difficile in freshwater and soil has been widely studied, little is known about its presence in sediments. In this study, we tested 15 sediment samples collected from various freshwater sources. C. difficile was isolated from all sampled sites, yielding a total of 171 strains grouped into 26 ribotypes, with 001/072 and 014/020 being the most prevalent. Genome sequencing of 37 isolates from 17 PCR ribotypes confirmed the presence of highly related strains in the geographically distant and unlinked water samples. Eight divergent PCR ribotypes from clades C-II and C-III were found in six samples. In each sample, the unbound fraction (supernatant after sediment wash) and bound fraction (sonicated sediment sample) were subjected to enrichment. Sonication was only slightly better than washing in terms of sample positivity (14 positive samples with sonication and 11 with washing). However, sonication substantially increased the diversity of the PCR ribotypes obtained (23 in sonicated samples vs nine in washed samples). In conclusion, sediments are a rich source for investigating the diversity of environmental C. difficile, including isolates from divergent lineages. Selection of the isolation method can significantly impact the diversity of captured PCR ribotypes. IMPORTANCE Clostridioides difficile, a pathogenic bacterium that can cause intestinal infections in humans and animals, thrives in the gut but also disperses widely through spores found in the environment. Clinical and environmental strains often overlap with common PCR ribotypes, which are consistently isolated worldwide. Environmental studies have mostly focused on water and soil, but sediments have been very poorly studied. In this study, we investigated the presence of C. difficile in various freshwater sediments and evaluated the effectiveness of two different isolation approaches on positivity rates and strain diversity. C. difficile was found to be highly prevalent in sediments, with an isolation rate of 100%. Sonication proved to be more effective than simple washing for capturing a greater diversity of PCR ribotypes. Overall, this study underscores the widespread presence of C. difficile in freshwater sediments and emphasizes the importance of continued surveillance and monitoring to understand its ecology and transmission dynamics. [ABSTRACT FROM AUTHOR]

As sand moves across Earth's landscapes, the shapes of individual grains evolve, and microscopic textures accumulate on their surfaces. Because transport processes vary between environments, the shape and suite of microtextures etched on sand grains provide insights into their transport histories. For example, previous efforts to link microtextures to transport environments have demonstrated that they can provide important information about the depositional environments of rocks with few other indicators. However, such analyses rely on 1) subjective human description of microtextures, which can yield biased, error-prone results; 2) nonstandard lists of microtextures; and 3) relatively large sample sizes (>20 grains) to obtain reliable results, the manual documentation of which is extremely labor intensive. These drawbacks have hindered broad adoption of the technique. We address these limitations by developing a deep neural network model, SandAI, that classifies scanning electron microscope images of modern sand grains by transport environment with high accuracy. The SandAI model was developed using images of sand grains from modern environments around the globe. Training data encompass the four most common terrestrial environments: fluvial, eolian, glacial, and beach. We validate the model on quartz grains from modern sites unknown to it, and Jurassic-Pliocene sandstones of known depositional environments. Next, the model is applied to two samples of the Cryogenian Bråvika Member (of contested origin), yielding insights into periglacial systems associated with Snowball Earth. Our results demonstrate the robustness and versatility of the model in quickly and automatically constraining the transport histories recorded in individual grains of quartz sand. [ABSTRACT FROM AUTHOR]

The current study describes the development of simple, low-cost, and high-throughput digital image colorimetric methods to determine the total iron concentration in river sediment using the spot-test reactions of iron with 1,10-phenanthroline and thiocyanate. The colorimetric assay was done on 96-microzone plates, and a flatbed scanner was applied to acquire the images. The proposed methods offered a linear range from 0.2 to 14.0 mg/L, with a detection limit of 0.11 mg/kg for the 1,10-phenanthroline method, and, for the thiocyanate method, the linear range comprises 2.0–10.0 mg/L, with a detection limit of 0.28 mg/kg. It was observed that both proposed digital image colorimetric methods (1,10-phenanthroline and thiocyanate) yielded statistically similar results to the reference procedures at a 95% confidence level. A standard reference material (NIST 8704) also was utilized for accuracy assessment and the results were statistically equivalent to the certified values within the 95% confidence level. The digital image colorimetric methods can be an alternative method for iron determination in sediment samples, allowing fast sample screening at a low cost. [Display omitted] [ABSTRACT FROM AUTHOR]

The seafloor environment is prone to rapid changes caused by landslides, which can result in significant human, financial, and environmental consequences. Previous research efforts have primarily focused on studying rigid submerged landslides using physical experiments and mesh-based numerical simulations. However, there is a need to investigate deformable soil masses due to their inherent complexity. In the current study, a smoothed particle hydrodynamics (SPH) method was developed to examine the behavior of submerged landslides. Three rheological models, namely Bingham, Herschel–Bulkley (H–B), and μ (I), were applied to characterize the properties of the sediment materials. The SPH governing equations were modified at the interface between the water and sediment phases to account for the density discontinuity between them. The viscosity term at this interface was determined using the Owens equation. The effective pressure, a crucial parameter in rheological models, was appropriately modified to reflect the influence of the water column on the sediment particles, utilizing a simple algorithm. For the μ (I) rheology, separate equations were applied to describe the behavior of dry and saturated conditions. Additionally, the Mohr–Coulomb criteria were utilized in the Bingham and H–B models to determine the yield stress. To validate the effectiveness of the proposed modeling approach, a column failure scenario was first simulated. Subsequently, a rigid submerged landslide was investigated to assess the capability and validity of the proposed framework in accurately capturing surge wave generation and calibrating the boundary friction factor. Finally, two deformable submerged landslides involving different materials, namely sand and glass beads, were simulated and compared with previous experimental and numerical studies at different time steps. Through these comprehensive investigations, the current understanding of the complex behavior exhibited by submerged landslides is enhanced, and valuable insight into landslide dynamics is provided. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) and nanoplastics (NaPs) in coastal regions, particularly in sediments, have gained increasing attention. However, in Türkiye, research on sediment pollution by MPs and NaPs is still limited. To fill this knowledge gap, the distribution, composition, and ecological impact of MPs and NaPs were investigated for the first time in the literature over a one-year period at three sampling stations on the south coast of Istanbul. The average total particle concentration was 1364.17 ± 600.51 particles.kg−1 dw sediment. Most of the MPs detected in the sediments were in the form of fibers with a size of 100–250 µm and were black and transparent. The study found that NaPs accounted for only 17%, 13.8% and 11.8% of the particles collected at stations S1, S2 and S3, respectively. According to the FTIR results, polyethylene and polyethylene terephthalate were the most abundant compared to polypropylene, polyamide and other polymers. The hazard index was classified as level V with a value of 17,261. This classification emphasizes the urgent need for further comprehensive studies on the risk assessment of MPs and NaPs. Scanning electron microscopy results showed microorganisms on the particle surface, indicating the MP-associated passing-through mechanism. Moreover, energy dispersive spectroscopy detected several unexpected elements such as Nb, Sr, Mo, Bi, Ta and Rn on MP and NaP surfaces. The results indicate that MP and NaP pollution in Istanbul’s coastal sediments may pose a major risk to the environment through the leaching of inherent/adsorbed elements and therefore requires future investigation. [ABSTRACT FROM AUTHOR]

Soil erosion and subsequent sedimentation pose significant challenges in the Sikkim Himalayas. In this study, we conducted an assessment of the impact of rainfall-induced soil erosion and sediment loss in South Sikkim, which falls within the Teesta Basin, employing Revised Universal Soil Loss Equation (RUSLE) and Sediment Yield Index (SYI) models. Leveraging mean annual precipitation data, a detailed soil map, geomorphological landforms, Digital Elevation Models (DEMs), and LANDSAT 8 OLI data were used to prepare the factorial maps of South Sikkim. The results of the RUSLE and SYI models revealed annual soil loss >200 t ha−1 yr−1, whereas mean values were estimated to be 93.42 t ha−1 yr−1 and 70.3 t ha−1 yr−1, respectively. Interestingly, both models displayed similar degrees of soil loss in corresponding regions under the various severity classes. Notably, low-severity erosion <50 t ha−1 yr−1 was predominantly observed in the valley sides in low-elevation zones, while areas with severe erosion rates >200 t ha−1 yr−1were concentrated in the upper reaches, characterized by steep slopes. These findings underscore the strong correlation between erosion rates and topography, which makes the region highly vulnerable to erosion. The prioritization of such regions and potential conservation methods need to be adopted to protect such precious natural resources in mountainous regions. [ABSTRACT FROM AUTHOR]

Purpose: The information about mercury (Hg) fractions obtained by simple thermodesorption screening techniques has not been compared with that from chemical extraction methods. Here, we examined Hg fractions in the surface sediments by a simple thermodesorption method and by a sequential selective extraction method to better understand the biogeochemical reactivity and mobility of Hg in the Changjiang Estuary wetlands. Materials and methods: The concentrations of Hg fractions in sediments were analyzed by DMA-80 at different heating temperatures of 175, 225, 325 and 750 °C. Hg compounds in selected sediments were determined by sequential chemical extractions with 0.5 M HCl followed by 1 M KOH. Results and discussion: The results showed that the proportions of labile Hg fractions released at 175 ℃ were less than 5% of the total Hg, which could correlate with highly reactive and poorly crystalline iron oxides that have high biogeochemical reactivity in sediments. Furthermore, more than 74% (of the total, on average) of Hg in the sediments was released at temperatures between 175 and 325 ℃, which corresponded well to the amount of organic-chelated Hg in the sediments as determined by extraction with 1 M KOH. These results suggested that Hg bound to humic substances or to organomineral complexes could play a key role in controlling the thermal release of different Hg species from the sediments. Conclusions: The thermal decomposition method could serve as a fast and reliable screening method for the identification of different Hg compounds to help assess Hg mobility and bioavailability in aqueous (e.g., estuarine wetlands) sediments. [ABSTRACT FROM AUTHOR]

Purpose: The river-lake ecotone in lake ecosystems can strongly influence sediment nitrate dissimilatory reduction processes. However, the mechanisms underlying these processes in river-lake ecotone ecosystems are still poorly understood. This study aims to investigate the rates of sediment nitrate dissimilatory reduction processes in Poyang Lake and clarify the mechanisms and environmental implications of these processes. Materials and methods: Sediment samples from five river-lake ecotones and lake ecosystems were collected from Poyang Lake, China. Sediment nitrate reduction and N2O production rates were measured using 15N isotope tracing experiments. The abundance of denitrifiers, anammox 16S rRNA bacteria, and nrfA genes was quantified using the polymerase chain reaction method. Correlation analysis, redundancy analysis, and stepwise linear regression were used to evaluate the mechanisms of sediment nitrate reduction processes. Results and discussion: Sediments in the river-lake ecotone showed significantly higher denitrification (DEN), N2O production, dissimilatory nitrate reduction to ammonium (DNRA), and anammox rates compared to lake ecosystems. DEN was the dominant process contributing to nitrate reduction, accounting for 73.36% and 74.13% in the river-lake ecotone and lake ecosystem, respectively. DEN, N2O, and DNRA rates were significantly positively correlated with TOC, sulfide, and Fe2+ contents, which control the abundance of denitrifying and nrfA genes, ultimately increasing these rates. Conclusion: The annual input of reactive N to the lake from the watershed is almost equivalent to the annual N removal. However, higher DNRA and N2O production rates indicate that approximately 23.59% of the annual N input to the lake may be transformed to NH4+ or N2O. N retention and N2O production in the river-lake ecotone significantly exceed those in the lake ecosystem, highlighting the ecotone as a hotspot for eutrophication risk and N2O emissions. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are increasingly recognized as environmental contaminants with complex impacts on fish and other aquatic organisms. This study determined the microplastics abundance and the induced-ecological risks of microplastics in water, sediment, and commonly harvested fishes of a Ramsar site, Deepor Beel of Assam, India. Six samples of water and sediment were collected with nine individuals of two commonly harvested fish species Puntius sophore (Pool Barb) and Gudusia chapra (Indian River Shad). The abundance of microplastics in water and sediments were analyzed through organic matter digestion using hydrogen peroxide (H2O2, 30%) and sodium chloride (NaCl) for density separation. Potassium hydroxide (KOH, 10%) was used for digestion of fish gut. The microplastics were identified visually and chemically characterized through micro-Raman spectroscopy. Total 467 microplastic particles in water and sediment, and 62 particles in fish were identified. An average concentration of 0.55 ± 0.06 particles/L in water, 4.03 ± 0.41 particles/100 g in sediment samples, 3.83 ± 2.26 particles/individual in Puntius sophore, and 6.5 ± 3.40 particles/individual in Gudusia chapra were detected. Fibers accounted to the major shape of microplastic in water (54%) and sediment (50%), whereas fragments (65%) were the major shapes detected in both fishes. The color composition includes blue, black, red, green, brown, yellow, and transparent. Fiber particles size ranged between 150 and 1782 µm, fragments within 85–325 µm, and sphere within 85–220 µm. Chemical characterization of microplastics revealed polymer types including polypropylene (PP = 27%), polyvinyl chloride (PVC = 25%), acrylonitrile–butadiene–styrene (ABS = 18%), polycarbonate (PC = 13%), polyethylene (12%), and polystyrene (PS = 5%). PHI levels were at hazard level III and V for water and sediment samples and at level IV for both fish species. The PLI at hazard level I indicated low pollution levels, whereas the PERI were within danger and extreme danger levels. This study is the first report in abundances of microplastics and the ecological risk assessment of microplastics in surface waters, sediments and fishes of Deepor Beel wetland. [ABSTRACT FROM AUTHOR]

The impact of pollution on the Ologe Lagoon was assessed by comparing physicochemical properties, hydrocarbon concentrations and microbial community structures of the sediments obtained from distinct sites of the lagoon. The locations were the human activity site (OLHAS), industrial-contaminated sites (OLICS) and relatively undisturbed site (OLPS). The physicochemical properties, heavy metal concentrations and hydrocarbon profiles were determined using standard methods. The microbial community structures of the sediments were determined using shotgun next-generation sequencing (NGS), taxonomic profiling was performed using centrifuge and statistical analysis was done using statistical analysis for metagenomics profile (STAMP) and Microsoft Excel. The result showed acidic pH across all sampling points, while the nitrogen content at OLPS was low (7.44 ± 0.085 mg/L) as compared with OLHAS (44.380 ± 0.962 mg/L) and OLICS (59.485 ± 0.827 mg/L). The levels of the cadmium, lead and nickel in the three sites were above the regulatory limits. The gas chromatography flame ionization detector (GC-FID) profile revealed hydrocarbon contaminations with nC14 tetradecane > alpha xylene > nC9 nonane > acenaphthylene more enriched at OLPS. Structurally, the sediments metagenomes consisted of 43 phyla,75 classes each, 165, 161, 166 orders, 986, 927 and 866 bacterial genera and 1476, 1129, 1327 species from OLHAS, OLICS and OLPS, respectively. The dominant phyla in the sediments were Proteobacteria, Firmicutes, Actinobacteria, and Chloroflexi. The principal component ordination (PCO) showed that OLPS microbial community had a total variance of 87.7% PCO1, setting it apart from OLHAS and OLICS. OLICS and OLHAS were separated by PCO2 accounting for 12.3% variation, and the most polluted site is the OLPS. [ABSTRACT FROM AUTHOR]

We evaluated the post‐fire sediment dynamics in beaver ponds to examine these ponds' contributions to sediment storage following disturbance. Beaver dams and beaver mimicry structures impound water and sediment, a function that is of growing interest in wildfire‐prone landscapes. Wildfires typically lead to high sediment loading into rivers in the years following fire, constituting a disturbance to aquatic ecosystems and a challenge to water resource managers. Previous work establishes that beaver dams trap substantial volumes of sediment, but sedimentation appears spatially and temporally heterogeneous and it remains unclear the extent to which short‐term pulses of sediment are attenuated by these structures. We examine the conditions under which beaver dams and beaver mimicry structures store post‐fire sediment by quantifying the sediment volume of 40 ponds, about half of which were burned in large wildfires in the Colorado and Wyoming Rocky Mountains in 2020. The median relative volume of burned ponds is 85%, which is greater than the median for unburned ponds (58%), meaning that burned ponds store higher relative volumes of sediment when pond size is accounted for. Furthermore, sediment accumulated at a median rate of 3.0 cm/year over the entire history of the pond. Post‐fire sedimentation rates, with a median of 20.4 cm/year, were an order of magnitude higher than pre‐fire rates with a median of 1.8 cm/year. In addition, vegetation and geomorphic characteristics correlated with sediment storage in ponds. Sediment surveys confirmed that ponds with greater surface areas contain higher volumes of sediment. Additionally, older ponds and ponds abandoned by beavers stored higher volumes of sediment compared to recently constructed ponds, ponds actively maintained by beaver, and beaver mimicry structures. These findings demonstrate that beaver ponds and mimicry structures may function as sediment sinks capable of attenuating post‐fire sediment. The biogeomorphic context, defined across multiple scales from the pond to the catchment, provides additional explanation for the wide range of sediment storage observed and remains an important consideration for beaver‐based restoration, catchment sediment management, and resilience evaluation. [ABSTRACT FROM AUTHOR]

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The environmental fate of a plant growth regulator cyclanilide was studied in this paper. The degradation, adsorption, and migration behaviors of cyclanilide were detailly measured in the laboratory. The results showed that the DT50 of cyclanilide degradation in the Jiangxi red, Taihu paddy, Changshu wushan, Shaanxi tide, and Dongbei black soils was 42.3 d, 31.9 d, 14.4 d, 30.4 d as well as 27.4 d under aerobic conditions and 32.3 d, 37.4 d, 29.3 d, 48.9 d as well as 27.0 d under water anaerobic conditions, respectively, with the main metabolite being 2,4-dichloroaniline (2,4-D). The DT50 of 2,4-D ranged from 5.26 to 27.1 days under aerobic conditions, and from 10.6 to 54.1 days under anaerobic conditions. The adsorption of cyclanilide by the soils was well fitted by the empirical linear adsorption isotherm, and the adsorption constant (Kd, H) values in the Jiangxi red, Taihu paddy, Changshu wushan, Shaanxi tide, and Dongbei black soils were 7.08, 4.49, 4.05, 3.20, and 1.41, respectively. The results of a mobility test showed that cyclanilide had strong mobility in the most test soils. Furthermore, soil pH is the dominant element affecting the adsorption of cyclanilide in the soils. Under aerobic environment, the DT50 of total cyclanilide in river and lake water-sediment systems were 30.7 d and 34.0 d, respectively; under anaerobic environment, their DT50 were 30.8 d and 31.4 d, respectively. In water-sediment systems, 2,4-D mainly exists in aqueous phase and the DT50 ranged from 5.23 to 8.76 days. This work demonstrated that cyclanilide has the potential risk to contaminate environment and attention should be paid to its application. [ABSTRACT FROM AUTHOR]

Ice formation is generally considered to exclude many particles and most solutes and thus be relatively pure compared to ambient waters. Because river ice forms by a combination of thermal and mechanical processes, some level of sediment entrainment in the ice column is likely, though reports of sediment in river ice are limited. We observed high and sporadic levels of silt and sand in ice of the Kuskokwim and Tanana rivers (Alaska, the United States) during routine field studies. These observations led us to make a more comprehensive survey of sediment entrainment in river ice of the Kuskokwim and Yukon rivers and several of their tributaries. We collected and subsampled 48 ice cores from 19 different river locations in March 2023, which included concurrent measurements of water turbidity, velocity, and depth. Approximately 60% of cores contained detectable levels of sediment, averaging 438 mg/L with median concentrations exceeding 1000 mg/L in three cores from the Yukon and Kuskokwim main stems. Many cores had even higher concentrations at certain intervals, with seven cores having subsamples exceeding 2000 mg/L; these were often located in the middle or lower portion of the ice column. Jumble ice, formed mechanically by frazil‐pan jamming during freeze‐up, was generally the best predictor of higher sediment entrainment, and these locations often had higher under‐ice velocities and depths. Our observation of high and widespread sediment entrainment in northern river ice, particularly in jumble‐ice fields, may have implications for sediment transport regimes, ice strength and transportation safety, and how rivers break up in the springtime. [ABSTRACT FROM AUTHOR]

Lake Zminje Jezero (1535 m a.s.l.) in Montenegro was studied for chironomid and other aquatic invertebrate remains in a sediment sequence dating back to 12,000 calibrated 14C years before present (cal yr BP), providing, to our knowledge, the first lake-sediment record studied for chironomids and other associated chitinous aquatic invertebrate remains in the Dinaric Alps. Changes in chironomid and other invertebrate remains along the record make it possible to constrain changes of relevant environmental variables for aquatic invertebrates in the lake including temperature, oxygen availability, trophic status and water depth. The results suggest moderate changes in trophic conditions with chironomid assemblages indicating meso- to eutrophic conditions during the analysed interval. Invertebrate assemblages were typical for lakes with relatively high oxygen availability with a minor trend during the middle to late Holocene to conditions observed in lakes that are more hypoxic. A change in temperature is suggested in the earlier part of the record when the share of chironomid taxa adapted to warmer conditions increased, at the Younger Dryas to Holocene transition, whereas later no particularly pronounced shifts in temperature-sensitive taxa were observed. July air temperatures were estimated based on chironomid assemblages using a transfer function based on calibration data consisting of 117 lakes sampled in the Swiss Alps and northern Switzerland. The results suggest that temperatures rapidly increased by 5 °C at the onset of the Holocene (11,500 cal yr BP) leading to a relatively warm early to mid-Holocene and thereafter slightly decreased during the late Holocene. Reconstructed temperatures are discussed together with a previously published pollen record for our study site and are broadly consistent with other chironomid-based temperature reconstructions from Central, Eastern and Southern Europe. From ca. 3000 cal yr BP sedimentation rates increased and from ca. 500 cal yr BP onwards pollen data suggest that the vegetation and lake catchment were affected by human activities, possibly influencing chironomid and other invertebrate assemblages in the lake and thereby also reconstructed temperatures. Overall, our results show that combining analyses of chironomid and other invertebrate assemblages can provide valuable insights into long-term environmental changes and can provide temperature reconstructions for small mountain lakes in the Balkans, such as Zminje Jezero. [ABSTRACT FROM AUTHOR]

Long-chain alkenones (LCAs) have been widely used as important biomarkers in palaeoceanographic studies. However, the commonly used LCAs proxies are mainly based on C37 alkenones, and it is still lack of the studies about the distribution and indications of LCAs with different chain lengths other than C37 alkenones. Here, the composition and distribution of LCAs were analyzed in surface sediments from the southern Yellow Sea (SYS) and a sedimentary core (A02-C) from the central Yellow Sea (YS) mud area. The results showed that C37, C38 and C39 alkenones were the major LCAs in surface sediments of the SYS, and the relative contents of C38:2Et, C37:2Me, C37:3Me, C38:2Me, C38:3Et, C38:3Me, C39:2Et and C39:3Et were 18.3%–59.8%, 22.6%–41.2%, 7.4%–23.0%, 6.6%–15.4%, 3.8%–13.3%, 3.6%–8.7%, 2.8%–6.0% and 0.7%–3.0%, respectively. Then the relationships of U38MeK-U38EtK and U37K′-U38EtK indicate that LCAs are mainly derived from Emiliania huxleyi (E. huxleyi). High ratios of total C37 alkenones to total C38 alkenones (K37/K38) (1–1.2) were found in the central SYS, corresponding to the relatively high abundance of E. huxleyi; while low ratios of K37/K38 (0.7–0.9) were observed at nearshore area of the SYS where Gephyrocapsa oceanica (G. oceanica) has relatively high abundance. The spatial distribution of K37/K38 ratio is also consistent with that of coccolithophores nannofossil in the sediments. In addition, K37/K38 ratio in core A02-C varied from 0.7 to 1.1 with a gradual decreasing trend during the past 5.5 kyr. This suggests that the relative abundance of E. huxleyi decreased gradually, caused by the changes in the Yellow Sea Warm Current (YSWC) and the East Asian Winter Monsoon (EAWM) during this period. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFASs) are emerging persistent organic pollutants (POPs). In this study, 47 surface sediment samples were collected from the Yellow River Delta wetland (YRDW) to investigate the occurrence, spatial distribution, potential sources, and ecological risks of PFASs. Twenty-three out of 26 targeted PFASs were detected in surface sediment samples from the YRDW, with total ∑23PFASs concentrations ranging from 0.23 to 16.30 ng g−1 dw and a median value of 2.27 ng g−1 dw. Perfluorooctanoic acid (PFOA), perfluorobutanoic acid (PFBA) and perfluorooctanesulfonic acid (PFOS) were the main contaminants. The detection frequency and concentration of perfluoroalkyl carboxylic acids (PFCAs) were higher than those of perfluoroalkanesulfonic acids (PFSAs), while those of long-chain PFASs were higher than those of short-chain PFASs. The emerging PFASs substitutes were dominated by 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA). The distribution of PFASs is significantly influenced by the total organic carbon content in the sediments. The concentration of PFASs seems to be related to human activities, with high concentration levels of PFASs near locations such as beaches and villages. By using a positive matrix factorization model, the potential sources of PFASs in the region were identified as metal plating mist inhibitor and fluoropolymer manufacturing sources, metal plating industry and firefighting foam and textile treatment sources, and food packaging material sources. The risk assessment indicated that PFASs in YRDW sediments do not pose a significant ecological risk to benthic organisms in the region overall, but PFOA and PFOS exert a low to moderate risk at individual stations. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: A major function of mangroves is carbon sequestration in sediment. This study aimed to determine differences in carbon content in sediments in various types of mangroves and environmental parameters. METHODS: This study was carried out in Pesawaran as a natural mangrove and in South Lampung as rehabilitated mangrove in Indonesia. Purposive sampling method was used by considering the types of mangroves at the locations. Sediment sampling was taken using a polyvinyl chloride pipe with a diameter of 47.46 milimeters and a height of 30 centimeters. The sediment parameters measured were bulk density, carbon stock, and sequestration. Environmental parameters measured included sediment texture, potential of hydrogen, temperature, salinity, and total dissolved solids. A statistical analysis was conducted using the principal component analysis to determine the relationship between the organic carbon stock and the environmental parameters. FINDINGS: The study results showed that natural mangroves (Pesawaran) had a higher organic carbon value at 2.2 ± 0.32 percent than rehabilitated mangroves (South Lampung) at 0.9 ± 0.25 percent. The principal component analysis results revealed that organic carbon, carbon dioxide equivalent, carbon stock, and carbon sequestration had positive correlation characteristics influenced by salinity, silt, and clay, while negative correlation characteristics were affected by temperature, total dissolved solids, and sand. The distribution of sediment texture tended to show more silt in rehabilitated mangroves, while natural mangroves tended to have the same composition between sand and silt. The potential of hydrogen conditions in natural and rehabilitated mangroves showed no significant differences in values. The salinity in Pesawaran, which was classified as a natural mangrove, was higher due to the influence of the tides and was directly facing the shoreline. Meanwhile, in South Lampung, which was categorized as a rehabilitated mangrove, the salinity was lower due to the long dry season and the canals being unable to support the water entering the mangroves. CONCLUSION: The organic carbon content at the research locations was influenced by the older age of the Rhizophora stylosa compared to that of the Rhizophora mucronata and Ceriop tagal types of mangroves. The carbon sequestration rate values showed 1.65-3.14 for natural mangroves and 0.29-1.25 for rehabilitated mangroves, thus establishing that the rate is higher (2-3 times) in natural mangroves than in rehabilitated mangroves. [ABSTRACT FROM AUTHOR]

Plastics are manufactured for various purposes but result in microplastic pollution in aquatic ecosystems. Riverine microplastic occurrence, spatial distribution, and impact have been globally documented but not well understood in Africa. We quantified 36 984 microplastics in riverbed sediment and river water along the Olifants and Sabie rivers, Kruger National Park (KNP), South Africa. These rivers have independent catchments. The microplastic profiles (size, polymer, morphotype, and colour) differed significantly between rivers. Riverbed sediment microplastic (mostly beads) concentrations ranged between 2022 to 9971 n/kg dm, and 2237 to 27 259 n/kg dm, for the Olifants and Sabie rivers respectively. Microplastic (mostly fragments) concentrations in river water ranged between 11 to 50 n/L in the Olifants River, and 4.0 n/L to 41 n/L in the Sabie River. Polyethylene terephthalate (PET) was prevalent in sediment (39%) and water (32%). Concentrations varied along both river stretches but the expected concentration decrease downstream was not observed. This raises transboundary concerns, as all the KNP rivers cross into Mozambique and from there into the Indian Ocean. Given the pervasive plastic pollution already present, there is a need for significant upstream and in-park interventions to reduce the concentration of microplastic in rivers flowing through conservation areas. [ABSTRACT FROM AUTHOR]

Aluminum-based P-inactivation agent (Al-PIA) is a highly effective material for phosphorus removal, which has great potential to restore eutrophic water bodies. In this study, active capping plate (ACP) was formed by mixing Al-PIA with cement and fly ash. The scour resistance coefficient of the prepared ACP was 98.01 % and the water permeability coefficient was 0.139 cm/s, which meet the requirements of strength and water permeability. Exogenous phosphorus was used as an input in the indoor dynamic experiment to examine the effectiveness of ACP capping to control phosphorus in sediment-water system. The indoor dynamic experiment lasted for 110 days. After experiment, the effect of dissolved oxygen (DO) and pH was explored, the change of phosphorus concentration in the overlying water was examined, and the changes of phosphorus in ACP and sediments were also analyzed. After ACP capping, the pH eventually maintained below 8 and was slightly higher than that of the control system. The DO concentration initially decreased, then increased, and finally remained in the range of 7 to 8 mg/L. Compared to the control system, the average reduction rates of total phosphorus (TP), dissolve total phosphorus (DTP) and dissolve inorganic phosphorus (DIP) in the overlying water were 90.57%, 91.69%, and 92.80%, respectively. ACP promotes the conversion of unstable phosphorus in sediments to stable phosphorus, and calcium-bound phosphorus (Ca-P) is the main form of phosphorus fixed by ACP. In addition, ACP was found to have a limited effect on reducing the risk of release of biologically available phosphorus from sediments. [ABSTRACT FROM AUTHOR]

Bagega community is an artisanal mining community with a history of Pb poisoning. The community is served by a small lake as an important source of water for cattle watering, irrigation, washing, and fishing among other uses. The concentration of Cd, Cr, and Pb in soil and plants at the bank, surface water, sediment, and fish of the lake were analysed using Agilent 4210 MP-AES machine after microwave digestion using the Advanced Microwave Digestion System model (Ethos easy). The concentrations of Pb and Cr in water from Bagega Lake were found to be above the WHO acceptable limits. This presents a health risk to humans and other animals that utilize directly or indirectly utilize the water in the lake. Catfish (Clarias anguillaris) and Tilapia (Oreochromis niloticus) had higher Pb and Cr concentrations in the gills than in the liver and h muscle (flesh). The concentrations of Cr, Cd and Pb of soils in the bank and sediment of Bagega Lake were below the WHO acceptable limits. A total of thirteen (13) plant species belonging to seven (7) families were identified to be dominant around the Bagega Lake during the time of study and they all show the potential of bioaccumulation of Cr and Pb based on their BCF. [ABSTRACT FROM AUTHOR]

This research paper investigates the photodegradation of Malachite Green (MG) using a new composite of river sediment (Sd) and synthesized TiO2 (Sd-TiO2-X%). TiO2 powder was synthesized using the sol–gel method and catalyst composites Sd-TiO2-X% (X = 10%, 15%, and 20%) were obtained using the wet impregnation. The photocatalytic performance of the composites was investigated using Box–Behnken design and results in the optimal parameters of %TiO2 (%) = 19.73, [MG] (ppm) = 42.25, and pH 9.58. Furthermore, Sd-TiO2-20% demonstrated exceptional stability and performance after undergoing five cycles. The scavenging tests for free radicals strongly confirmed the activity of superoxide ions (O2⋅−) and hydroxyl radicals (⋅OH) as the primary species responsible for degrading MG. The findings highlight the synergetic effect between river sediment and TiO2 in the photodegradation of organic pollutants-contaminated wastewater. This confirms the potential of valorizing sediments for promising and sustainable depollution applications using sediment-based materials. [ABSTRACT FROM AUTHOR]

Potentially toxic elements (PTEs) pose a significant threat to aquatic ecosystems. This study investigated the content and potential sources of PTEs (Cr, Mn, Ni, Cu, Zn, Cd, Pb) in water, sediment, and dominant aquatic plants (Hydrilla verticillata and Spirogyra varians) in the Xiaojiang River, located near the Zhaiying manganese mine in Guizhou Province, China. Correlation analysis, principal component analysis (PCA), and cluster analysis were employed to assess PTE distribution and potential sources. Water PTE concentrations complied with the Class II standard (GB3838-2002), indicating no water pollution. However, sediment PTE levels exceeded background values, particularly Mn, which exhibited moderate to strong contamination. Cd also showed moderate contamination, posing a considerable ecological risk. Cd was the main potential pollutant with the highest contribution rate. Mn and Cd were therefore identified as priority pollutants requiring targeted abatement strategies. Mining activities likely represent the primary source, but combined pollution from vehicle traffic and agriculture might also contribute. Hydrilla verticillata demonstrated a higher capacity for PTE enrichment from sediment compared to Spirogyra varians, suggesting its potential for sediment remediation (except for Cu). A significant correlation existed between both plant species and sediment PTE content. PCA supported the association between S. varians and sediment PTEs. Linear regression analyses revealed better correlations between S. varians and sediment Mn, Ni, Cu, and Zn (0.77, 0.68, 0.82, and 0.79, respectively). Taken together, these findings suggest that S. varians serves as an effective bioindicator for monitoring sediment contamination with PTEs. [ABSTRACT FROM AUTHOR]

Nanomaterials, with their small size, surface characteristics, and antibacterial properties, are extensively employed across environmental, energy, biomedical, agricultural, and other industries. This study examined the antibacterial efficacy of magnesium hydroxide (Mg(OH)2) nanoparticles (NPs) against sulfate-reducing bacteria (SRB) within sediments. The inhibitory effects of two types of Mg(OH)2 NPs with distinct particle sizes (20.3 and 29.6 nm) and concentrations (0–10.0 mg/mL) were examined under optimal treatment conditions. The antibacterial mechanisms of Mg(OH)2 NPs through direct contact and dissolution effects were determined. The results revealed a correlation between the concentration, particle size, and inhibitory activity, with the smallest NPs (20.3 nm) at the highest concentration (10.0 mg/mL) substantially reducing SRB counts from 8.77 ± 0.18 to 6.48 ± 0.13 log10 colony forming units/mL after 6 h treatment. Treatment with high concentrations of Mg(OH)2 NPs induced cellular damage, reduced intracellular lactate dehydrogenase activity, and elevated intracellular catalase activity and H2O2 content, suggesting that the contact effect of NPs stimulated SRB. This leads to oxidative stress response and structural damage to the cell membrane, which has emerged as the primary driver of the antibacterial action of Mg(OH)2 NPs. This study presents a novel nanomaterial that can inhibit and control SRB in natural sedimentary environments. [ABSTRACT FROM AUTHOR]

Channel networks have been widely used to model sediment transport and accumulation. Extracting channel networks in the check dam region from digital elevation models on the Loess Plateau can facilitate effective decision‐making and planning for soil and water conservation. Three methods are generally used to ensure the continuity of channel networks by removing check dams as hydrological barriers: filtering, filling and breaching. However, these methods may still cause disruption and displacement of the channel network owing to the existence of check dams. This study presents the development of an integrated method (improved regional growth and linear feature detection [iRG‐LFD]) for extracting natural continuous channel networks and locating check dams. First, a proposed improved region growth method based on channel and check dam terrain features was used to extract the complete channel network. Subsequently, the line segment detector for extracting straight lines was then improved to separate lines with different slopes. Finally, by combining the channel network and line segment detector results, a cross model was proposed for extracting check dams of different sizes. The experimental results for the Wangmaogou and Zhoutungou catchments showed minimal errors when the proposed method was used to extract the channel network, and F1‐scores of 86.67% and 86.95% were obtained for the predicted check dam samples in the two catchments, respectively. The results indicate that this method can be effectively used to extract continuous natural channel networks and accurately identify check dams and can thus be used to design soil and water conservation measures. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are colonized by biofilm-forming microbes. Biodegradable plastics, popular replacements for traditional plastics, still have unknown biofilm formation characteristics. We conducted a 60-day indoor experiment, where sediment was exposed to traditional MPs (polypropylene, PP), biodegradable MPs (polylactic acid, PLA), and glass beads (GLASS). The microbial communities in the MPs-biofilm were analyzed using high-throughput sequencing. Results indicated that Proteobacteria was the dominant phylum on all substrates, followed by Actinobacteria, and Firmicutes. At the genus level, the majority of microorganisms colonizing PP possessed nitrification and denitrification capabilities, while the dominant bacteria on PLA were capable of degrading lignin, cellulose and carbon metabolism. The genus Sphingomonas, a promising bacteria capable of degrading biodegradable microplastics, was particularly discovered on the PLA biofilm, meanwhile, bacterial colonization of PLA indirectly increased the potential for human transmission of pathogens. Redundancy analysis revealed that the pH and moisture significantly affected the bacterial communities. Pearson correlation heatmap indicated that the abundance of the majority of dominant bacterial genera of two MPs biofilms is negatively correlated with the physicochemical parameters of sediment (pH, moisture, TN, TP), except for salinity. The microbial communities associated with PP and PLA exhibited distinct differences caused by the combined effects of changes in physicochemical properties of sediment and different material substrates. This study provides further evidence of the significant selective features exhibited by microbial colonization on these two MPs when exposed to the same source community, offering insights into the exploration of promising bacteria for MPs degradation. [ABSTRACT FROM AUTHOR]

Estuarine sediments serve as significant reservoirs for mercury (Hg) and methylmercury(MeHg), which can also interconvert in the external environment. The release of Hg in response to human activities raises concerns about its potential ecological and human health effects. Sediment samples were collected in December 2021 from four locations (sites), and Hg cycling by measuring the concentrations of, and controls on, the spatial distribution of total Hg (THg) and methylmercury (MeHg) in high-tidal zone (HTZ) and mid-tidal zone (MTZ) sediments of a mangrove forest (MF) and oyster farm (OF) was examined in northwestern Zhanjiang Bay, including simultaneous determination of sediment particle size, oxidation-reduction potential (Eh), pH, total organic carbon (TOC), sulfide concentration (S2-), and sulfate reducing bacteria (SRB). The research results indicated that concentrations of both THg and MeHg ranged between 20.0–104.0 ng/g and 0.011–0.277 ng/g in the sediments, respectively. The highest methylation potentials within the MF and OF were in sediments located approximately 10–15 cm below the surface. MeHg in the HTZ of the OF was likely derived from exogenous inputs as Hg methylation appears limited, and the formation of MeHg depended not only on the amount of inorganic mercury available for methylation in SRB, but also on the TOC, pH, Eh and S2- content in the sediment. A risk assessment of MeHg during the anthropogenic disturbance of this estuaries conducted on individuals eating oysters demonstrated that health risks are low. [ABSTRACT FROM AUTHOR]

Microplastic pollution has raised significant concerns among scientific communities and society in recent years due to its increase and lesser-known effects on the environment. To improve the knowledge of microplastic pollution in freshwater, we investigated microplastics in Anzali Wetland, a Ramsar site in northern Iran, as well as its nine main entering rivers. The extracted microplastics were characterized via visual identification, SEM–EDX, and μ-Raman methods. Microplastics (size range: 50–5000 μm) were found in all water and sediment samples with concentration of fibrous particles as well as polypropylene and polyethylene polymers. The mean concentration of microplastics in bottom sediment and surface water samples of the wetland was 301 ± 222 particles∙kg−1 d.w. and 235 ± 115 particles∙m−3 (0.23 particles∙L−1), respectively. The microplastic concentration in the central and eastern parts of the wetland was higher than in other areas; however, the mean concentrations revealed homogeneity across the wetland area. Water properties (dissolved oxygen, pH, temperature, electrical conductivity, and salinity in water) did not affect the concentration of microplastic particles, though correlational analysis revealed a strong positive association between microplastic quantity and turbidity. There was a significant positive relationship between microplastic concentration and the percentage of clay in sediment samples. The quantity of microplastics in river water was higher than in wetland water, but the difference between the results was not significant. However, the quantity of microplastics in the river's littoral sediment was higher than in the bottom sediment of the wetland where the difference between the results was significant. Microplastic ecological risk assessment showed high potential ecological risk. The findings underscore the importance of effective management strategies and the implementation of policies to mitigate the negative impact of MP pollution on ecosystems and human health. [ABSTRACT FROM AUTHOR]

Seabird colonies with long-term monitoring records, i.e., > 50 years, are rare. The population data for northern gannets (Morus bassanus) in Cape St. Mary's (CSM) Ecological Reserve (Newfoundland and Labrador, Canada) is robust, extending back to 1883 when the colony was presumed established. We inferred the colony's historical population shifts by measuring ornithogenic proxies in a dated sediment record collected from a nearby pond. Our record extended to the early eighteenth century, but the proxy data only began to show significant signs of seabird presence between ca. 1832 and 1910, aligning with the period gannets were first observed at CSM. Through the twentieth century, we observed significant increases in δ15N, P, Zn, Cd, and chlorophyll a, coeval with a shift in the dominant diatom species, indicating rapid colony growth. The proxies were overall highest in ca. 2005, corresponding to the reported historical maximum of the gannet colony in 2009. Our results validate that paleo-reconstructions using ornithogenic proxies can accurately reflect population trends and provide a stronger understanding of the colony's establishment and growth. This study highlights the value of applying paleolimnological methods in seabird population studies to frame the history of a colony's dynamics and inform conservation efforts. [ABSTRACT FROM AUTHOR]

The widespread presence of microplastics (MPs) in freshwater systems as an emerging environmental pollutant has caused a global environmental problem. The present study investigates the distribution and abundance of source pathway and abundance of microplastics in surface sediment samples from rivers discharging into the Gorgan Bay, southeast of the Caspian Sea. A total of 57 surface sediment samples were taken from 19 stations to investigate the potential hot spots of pollution in the four rivers leading to the Gorgan Bay. The average level of microplastics was 333 ± 268 particles/kg. The highest amount is in the estuary of the Qarasu River (1080 ± 380 particles/kg) due to the accumulation of fishing, boating and tourism activities and the lowest amount in the forest area (80 ± 19 particles/kg) in the Klak River. The most common type of microplastic was fiber (68%). Microplastic pollution in the studied rivers is mostly black and gray (75.39%), and about 53% of them were sized less than 1000 μm. Spectroscopic analysis (Fourier Transform Infrared (FT-IR) of the MP showed that 37% were polyethylene, polyethylene (37%) and polypropylene (27%) were the dominating groups. The sediments’ size was significantly correlated (p>0.05) with the presence of microplastics. Sediments with a coarse grain (sand) demonstrated a great potential to store microplastics. The results of this study can be used for the management and protection policies of Gorgan Bay. [ABSTRACT FROM AUTHOR]

Sexual dimorphisms are generated by divergent processes, such as natural or sexual selection and niche convergence. Males and females of the lesser guitarfish, Zapteryx brevirostris, present morphological differences in their discs, and the relationships with the species biology and ecology were unrecognized. Analysing the morphometry of 201 specimens and the influence of bottom features on the frequencies of 188 specimens among life stages and sexes, we found strong evidence that gonadal maturation leads to dimorphisms on discs, validating a concavity on male pectoral fins as a secondary sexual dimorphism and rejecting the hypothesis that such dimorphisms were related to ecological pressures. The principal component analysis (PCA) and permutational MANOVA (PERMANOVA) analyses revealed that males and females shared similar body aspects until they reached maturity, mainly due to lower variations in WD, WR, LD, DPRO, and LSC at younger life stages. The relationships of these variables with LT corroborate the former results, showing a changing point around LT > 30 cm where females started to attain larger measurements than males. Moreover, we revealed ontogenetic shifts, with adults from both sexes exploring different habitats than juveniles and subadults. Differences in frequencies of each life stage were best explained by organic matter (OM) with the adults exploring bottom habitats of higher concentrations of OM than juveniles and subadults, strengthening the assumption that body differences between sexes are not related to ecological pressures. These results bring not only new insights about the possible advantages that those morphometric differences provide to males while mating but also information about the abiotic influences on species distribution, which, along with knowledge of local oceanographic dynamics and benthic community patterns, would inform actions for species conservation. [ABSTRACT FROM AUTHOR]

Introduction The amount of sediment production, the manner and time of sedimentation, the size and composition of sediment grains, and transport among the waterways network are important features of the sedimentation regime of Watersheds; Because changes in each of these factors cause changes in Watershed performance. Therefore, sediment production is a reflection of the importance and amount of erosion processes and sediment sources in the upstream parts of the Watershed and how sediment is transported and deposited from the moment of movement of erosion materials from the point of separation to the exit of it. Sediment connectivity indicators indicate the spatial changes of connectivity patterns in different parts of the Watershed and provide a suitable estimate of the contribution of sediment sources and sediment transport routes. For this purpose, investigating the spatial pattern of sediment flux at the Watershed scale is of particular importance in developing comprehensive management plans and measures to control erosion and sedimentation. Although various indicators and models have been developed in this field, their performance has not been evaluated based on observational data and statistical methods. This research aims to analyze the sediment flux pattern of the Neyriz Watershed located in the east of Fars Province, based on sediment connectivity and sediment transfer capacity indicators, and compare their performance based on field sediment evidence. Materials and Methods At first, a digital model of the ground elevation of the Neyriz Watershed with a spatial resolution of 12.5 m was prepared and its drainage network was extracted. Then, the sediment connectivity index was calculated by considering the upstream and downstream features of the Watershed and by considering the roughness factor as the sediment movement resistance factor, and the sediment connectivity map of the Watershed was made. Then, the sediment transport capacity index map was also prepared based on the concept of topography and using the digital model layer of land height. For this purpose, the sediment transport capacity index was calculated for each pixel of Neyriz Watershed in SAGA-GIS software, and a sediment transport map was prepared. Based on field visits to different parts of the Watershed, 30 positions that had evidence of sediment transfer were recorded as observation points of the sediment transfer event. Also, 30 other positions that did not have signs and evidence of sediment transfer were added to the validation database as observation points of no sediment transfer event. The corresponding values of each index were also extracted in the geographic information system and based on the available information, using evaluation methods based on the error matrix including true skill statistic (TSS), efficiency (E), and F score (F-score), the validation of the mentioned indicators was done quantitatively. Results and Discussion The value of the sediment connectivity index of the Neyriz Watershed in Fars Province varied from -7.24 to 2.43 and its median value was -4.36. The spatial pattern of the sediment connectivity index in this Watershed is such that the middle and western parts have a low amount and the northern, southern, and eastern parts have more amounts. In this research, the drainage network of the Watershed was introduced as the target of receiving the sediment; Parts of the slopes of the Watershed level, which had the conditions of sediment production and transfer were connected to the drainage network in terms of the transfer path, have shown a higher value of connectivity index. This index provides valuable information for land management by considering the upstream characteristics of each point as well as the characteristics of the transfer path to the sediment-receiving target. The value of the sediment transfer capacity index varied from 7.2 to 23.16 and the average value was 10.19. The value of this index is high in the marginal parts of the Watershed where there are sloping lands, and the middle parts of the Watershed have a small value. Based on the findings, the index of sediment connectivity with the true skill statistic (TSS) of 0.833, the efficiency value (E) of 0.916, and the F score of 0.915 is a better performance than the sediment transport capacity index (TSS= 0.633, E=0.816, F-score=0.825). In addition, based on the values of the false positive component in the error matrix, the sediment transport capacity index predicts high sediment flux potential in many situations; While in the field observations, it was not true. Conclusion Based on statistical evaluation criteria, the sediment connectivity index has been able to better describe the state of sediment flux and is more consistent with field realities. So that the sediment connectivity index, in addition to considering the characteristics of the upstream area of each point of the Watershed, is possible to consider the path of the sediment particle to the target location of the receiver (such as the nearest branch of the network drainage) has made it possible. Based on the findings obtained in this research, although the sediment transfer capacity index in some parts of the Neyriz Watershed of Fars Province was in line with the sediment connectivity index; However, due to the energy-based nature of the flow, this index only considers the local conditions of the points and ignores the features of the upstream area as well as the process of transporting sediment particles to the downstream. Therefore, it is suggested to use the sediment connectivity index in the erosion and sedimentation studies of Watersheds. Because when information about the amount of sediment production is not available; the Sediment connectivity index can provide useful information about the sediment transfer process in the Watershed. [ABSTRACT FROM AUTHOR]

Microplastic distribution surveys centered on Korea's Gwangyang Bay and southern coastal waters. Gwangyang Bay seawater averaged 3.17 ± 1.23 particles/L, and sediments averaged 462.4 ± 143.9 particles/kg. The southern coastal seawater averaged 0.10 ± 0.09 particles/L, and the sediments averaged 50.6 ± 29.7 particles/kg. Microplastics flowing from land, through physical modeling of ocean currents in Gwangyang Bay and southern coastal waters, pass through the Yeosu Strait and flow into the southern coastal waters. At the same time, it is judged that the southern coastal waters showed somewhat lower abundance than the Gwangyang Bay waters because they move toward the Korean Strait due to the Jeju warm current water and Tsushima current water, strongly generated in summer. In addition, the seawater microplastic abundance showed a higher abundance than that on the site adjacent to the land in the southern coastal waters, which is the study area. On the other hand, the results for sediment microplastic abundance were opposite to the surface seawater microplastic results. Therefore, it is judged that entering one source of pollution does not affect the distribution of microplastics in Gwangyang Bay and southern coastal waters, but rather this occurs in different forms. [ABSTRACT FROM AUTHOR]