Water Sediment Research Articles

From small water bodies to lakes: Exploring the diversity of freshwater bacteria in an Alpine Biosphere Reserve

Small water bodies, although supporting high biodiversity, are often understudied in the Alpine region. In this work, we characterized the planktic and benthic bacterial communities, as well as the water chemistry, of a wide physiographic range of 19 freshwater bodies within an Alpine Biosphere Reserve, including ponds, pasture ponds, peat bogs, shallow lakes, and lakes. We collected both water and surface sediment samples, followed by metabarcoding analysis based on the V3-V4 regions of the 16S rRNA gene. We investigated the changes in biodiversity and the distribution of unique and shared amplicon sequence variants (ASVs) between water (11,829 ASVs) and surface sediment (19,145 ASVs) habitats, as well as across different freshwater typologies. The majority of ASVs (78 %) were unique to a single sample, highlighting the variability and uniqueness of bacterial communities in such freshwater bodies. Most freshwater environments showed higher α-diversity in sediment samples (median, 1469 ASVs) compared to water (468 ASVs). We found that water and sediment habitats harboured unique bacterial communities with significant differences in their taxonomic compositions. Benthic bacteria were associated with several biogeochemical and degradative processes occurring in the sediments, with no notable differences among freshwater typologies and with phylogenetically and ecologically similar species. Conversely, planktic communities showed greater heterogeneity: small water bodies and peat bogs were characterized by higher relative abundances of Patescibacteria (up to 33 %), while lakes and shallow lakes were dominated by Actinobacteriota (up to 36 %). Cyanobacteria (426 ASVs) were generally distributed at low abundances in both water and sediment habitats. Overall, our results provided essential insights into the bacterial ecology of understudied environments such as ponds and pasture ponds and highlighted the importance of further exploring their rich pelagic and benthic bacterial biodiversity.

Characterization of Mineralogical and Mechanical Parameters of Alkali-Activated Materials Based on Water Sediments Activated by Potassium Silicate

Characterization of Mineralogical and Mechanical Parameters of Alkali-Activated Materials Based on Water Sediments Activated by Potassium Silicate

Estimation of gas saturated sediments parameters in shallow water using vector receiver

A scheme for estimating parameters of gas-saturated sediments in shallow waters based on signals from moving noise source is proposed and tested on experimental data. Advantages of joint use of information about pressure and vertical component of particle velocity in solving the considered problem are discussed.

Evaluation and Optimization of Landscape Spatial Patterns and Ecosystem Services in the Northern Agro-Pastoral Ecotone, China

The alteration of landscape spatial patterns (LSPs) and ecosystem services (ESs) in watersheds can have detrimental effects on the local environment and community. However, a comprehensive understanding of the current state of LSPs and ESs in watersheds around Winter Olympic venues in China is limited. Here, we assessed current LSPs and ESs and developed optimization strategies for the Xigou watershed around Winter Olympic venues in the northern agro-pastoral ecotone of China. The results indicated that the main land use type was grassland in the Xigou watershed, and landscape types were relatively homogenous. All three ESs (water yield, sediment retention, and carbon storage) generally improved from 2004 to 2020. For ESs, there was the lowest total volume of water yield in 2004 (637.44 × 104 m3). But sediment retention (10.54 × 106 t, 18.13 × 106 t, 13.28 × 106 t, and 16.85 × 106 t) had an upward, then downward, then upward trend before and after ERP. Carbon storage grew steadily. Correlation analysis suggested that the three ESs were closely related to the landscape spatial indices of average patch area (AREA_MN), contagion index (CONTAG), and Shannon’s evenness index (SHEI). AREA_MN, CONTAG, and SHEI in the eastern part of the study area promoted sediment retention and carbon storage, while in the southwestern part of the study area, they inhibited water yield and sediment retention. The results suggest that improving sediment retention by optimizing land use and cover change (LUCC) and LSPs is the main approach to further enhance ESs in the study area. Our study suggests that the inclusion of multiple landscape pattern indices can provide a more comprehensive representation of regional ecosystem service.

Multivariate Statistical Approach and Assessment of Pollution of Water and Sediments in Karstic Springs of Transboundary Aquifer Žumberak–Samoborsko Gorje Mountain (Croatia/Slovenia)

This study highlights the geochemistry of water and sediments of the karstic springs of the transboundary aquifer (TBA) Žumberak–Samoborsko Gorje Mt. (NW Croatia). After calculating pollution indices, the analysis showed that the sediments are unpolluted. The geo-accumulation index (Igeo) showed only the elements Ba and Rb, indicating moderate levels of pollution, with the highest values in springs Vapnik and Bistrac. Statistical analysis confirmed their natural origin. The water of these springs is under possible anthropogenic influence as indicated by elevated concentrations of total nitrogen (TN) and total phosphorus (TP). According to a principal component analysis (PCA) for elements in sediments, PC1 described a combined lithogenic and oxidative–reductive influence, PC2 described a combined geological background including total organic carbon (TOC) content and oxidative–reductive influence, while TOC had the greatest influence on PC3. Depending on element composition, the factor scores related to PC1 and PC2 resulted in two different groups of sites, while the factor scores concerning PC1 and PC3 did not show separation in two groups. The hierarchical cluster analysis showed three clusters in relation to the content of the elements. The correlation coefficient between the sediment and related water samples showed that the springs placed in a low-permeability formation (dolomite) had a strong positive coefficient of correlation.

Analysis and probabilistic health risk assessment of vertical heavy metal pollution in the water environment of reservoir in the west coast new area of Qingdao, China

The West Coast New Area is a typical city in China where water supply is predominantly sourced from reservoirs. Heavy metal pollution in these reservoirs directly impacts the safety of drinking water and human health. Therefore, this study comprehensively evaluated the status of heavy metal pollution in the water environment and sediment of the main water supply reservoir in the study area, revealing the interaction relationship and pollution sources, as well as assessing the probabilistic health risks to human beings. The results show that there are different degrees of pollution in the main water supply reservoirs in the study area, and the pollution increases with the increase of water depth. The heavy metal pollution index was up to 2681, indicating heavily pollution. The main polluting elements were Mn and Fe, and the maximum contents were 4.11 mg L−1 and 0.68 mg L−1, respectively, which far exceeded the Class III standard limit of drinking water in China. The main source of pollution is human activities, and Mn release from sediment aggravates deep water pollution. The non-carcinogenic risk index of heavy metals in the reservoir, ranging from 4% to 14%, is higher than 1, indicating a potential non-carcinogenic threat. Furthermore, heavy metals have a much greater impact on children compared to adults, among which Mn is the main contributor to human non-carcinogenic risk, contributing more than 60%. Therefore, controlling the content of Mn and Fe can effectively reduce the heavy metal pollution of reservoir and human health risk. The research results are of great significance for the utilization of reservoir water resources and the protection of the ecological environment in the study area.

The effect of Sesuvium portulacastrum for reducing inorganic nitrogen pollution in coastal mariculture wetland

Mariculture ponds are essential components of the coastal wetland, which are often criticized by eutrophication risk for the dissolved inorganic nitrogen (DIN) input to the coastal zone by the culture tailwater. However, the reduce of this DIN pollution was difficult because the tailwater is hard to collect and the treatment is inefficient and expensive. Sesuvium Portulacastrum is a coastal vegetation which has high efficiency in DIN absorption from the seawater and sediment. In this study, we use Sesuvium Portulacastrum as a tool species to study the control behavior of the DIN in mariculture ponds wetland. The change trend of DIN in pond water and benthic species in pond sediment was investigated. The results showed that Sesuvium Portulacastrum reduced NH4+, NO3-, and NO2- in the pond water by 83.21%, 95.22%, and 91.32%, respectively. The species number of benthic organisms was enhanced from 2 to 5 and the species structure was more optimized in Sesuvium Portulacastrum pond than control pond. At the end of the experiment, eutrophication indicator species (Capitella capitata) was disappeared in the Sesuvium Portulacastrum pond. Those suggest that the coastal vegetation (Sesuvium Portulacastrum) have great potential to eliminate DIN pollutants in mariculture pond wetland.

Distribution and co-occurrence of microplastics and co-existing pollutants in bottom water and sediment of the East China Sea

Microplastics (MPs) contamination in marine environment has been an emerging issue worldwide, notably due to the potential ecological risks of MPs with co-existing environmental contaminants and released toxic plastic additives. To verify the co-occurrence characteristics of MPs and co-existing pollutants in the benthic boundary layer (BBL), the distribution characteristics of MPs, and selected heavy metals (HMs) and halogenated flame retardants (Polybrominated diphenyl ethers, PBDEs, and Dechlorane Plus) in the bottom water and sediment were comprehensively investigated in the East China Sea (ECS). The sampling sites were selected along the coast of ECS, where might be significantly affected by terrigenous inputs and anthropogenic sources. MPs were abundant in the bottom water (62.8–480.2 items/L) and sediment (80.1–1346.7 items/kg d.w.) with polyester, polyethylene, and polypropylene being as the most abundant types and characterized as fiber/line, particle size 200–500 μm, and transparent/white. The abundance and characteristics of MPs demonstrated strong correlations within the bottom water and sediment, which might be due to the frequent exchange of materials. In addition, the abundance of MPs was significantly positively correlated with HMs (Cd, Cr, Pb) in the bottom water and PBDEs in sediment, respectively. According to the scanning electron microscopy/energy dispersive X-ray spectrometry analysis, MPs might act as carriers to transport and co-sediment the co-existing pollutants in water, and physically adsorb or chemically bind with pollutants in sediment. These results could help to elucidate the sources, migration, and fate, and verify the occurrence and potential risks of MPs and their co-existing pollutants in BBL, thus realize the management and control of MPs contamination in marine.

Primary risk assessment of microplastic pollution in spineless cuttlefish (Sepiella inermis) from the North-East Bay of Bengal: A tissue-based analysis

Microplastic pollution has a significant threat to marine ecosystems, yet its impact on spineless cuttlefish (Sepiella inermis) remains under-researched. This study aims to address this gap by analysing microplastic contamination in Sepiella inermis from the North-East Bay of Bengal. This species is widely consumed and transported globally as food, thus holding significant health concerns. A total of 40 adult female cuttlefish were collected from two sampling sites (18°36′31.35″N 87°48′10.63″E and 15°43′35.37″N 88°12′07.01″E) in the Bay of Bengal. Tissue samples from tentacles, gut, and nidamental glands were analysed for microplastic content, alongside sediment and surface water samples. Parameters such as microplastic abundance, size, shape, and colour were recorded. The average abundance of microplastic particles was measured at 2.003 particles per gram in tentacle tissue, 2.31 particles per gram in gut tissue, and 0.99 particles per gram in nidamental gland tissue. The gut tissue exhibited the highest abundance of microplastics per gram. Chemical characterization using FT-IR and confocal Raman spectroscopy identified 11 types of microplastic polymers. Of the 11 types of plastic polymers identified, PVC was the most prevalent, accounting for 17.64 % of the microplastics found across all tissues. PVC microplastics can cause significant harm to marine life and human health by accumulating in the food chain and releasing harmful chemicals like phthalates, which can lead to endocrine disruption. ABS, PET, PP, PE, and PA microplastic polymers are highly persistent in environment, leading to long-term pollution in oceans. When ingested by marine organisms, they can disrupt entire ecosystems. In humans, the accumulation of these microplastics can impair the immune system and contribute to chronic diseases. The Pollution Load Index (PLI) was calculated for each tissue type, revealing that gut tissue is more prone to microplastic pollution compared to the nidamental gland and tentacles. The average PLI per gram of gut tissue was 2.26, which was significantly higher than 1, indicating substantial pollution. This research highlights the urgent need for comprehensive strategies to mitigate microplastic pollution, given the potential health risks associated with the consumption of contaminated marine species.

Environmental Fragility in Commercial Forest Plantations Aiming at Sustainable Management

Objective: The objective of this study is to investigate the environmental fragility of two landscapes in which there is a predominance of commercial forest plantations, with the aim of analyzing this fragility through multicriterial evaluation, focusing on the planning of forest roads. Theoretical Framework: The theory of environmental fragility, multi-criteria evaluation methods, and principles of landscape management stand out, providing a solid basis for understanding the context of the investigation. These frameworks are crucial for analyzing the impact of forest roads on environmental variables such as water dynamics, sediment production, and soil erodibility. The integration of these theories allows for a comprehensive assessment of environmental fragility, essential for effective forest planning and road maintenance in forested areas Method: The methodology adopted involves a multi-criteria evaluation approach to assess environmental fragility in forest landscapes. Key criteria, including slope, distance from water bodies, soil erodibility, and topographic humidity, were integrated to create fragility maps. Data were collected through geographical and environmental analysis, processed with spatial analysis tools, and supplemented by principal component analysis to identify influential criteria. This approach enabled a detailed assessment of forest roads' environmental impact, supporting informed decisions in road planning and landscape management. Results and Discussion: The results revealed notable variations in environmental fragility. The analysis of forest roads highlighted their varying impact on environmental fragility. These results are framed within the context of environmental fragility and multi-criteria evaluation, emphasizing the role of criteria such as slope, proximity to water bodies, soil erodibility, and topographic humidity in assessing landscape degradation. The study underscores the need for careful forest road planning to mitigate environmental impacts and promotes the use of comprehensive evaluation methods in sustainable landscape management. Research Implications: The practical and theoretical implications of this research are discussed, providing insights into how the results can be applied or influence practices in the field of forest management and environmental conservation. These implications could encompass forest road planning, sustainable landscape management, and the development of environmental policies aimed at mitigating the impact of infrastructure on natural ecosystems.The study's findings emphasize the need for incorporating multi-criteria evaluation methods into forest planning processes to identify and mitigate areas of high environmental fragility. This approach can guide decision-makers in prioritizing areas for road maintenance, rehabilitation, or even rerouting to minimize ecological damage. Furthermore, the research underscores the importance of integrating environmental fragility assessments into broader forest management strategies, enhancing the sustainability of commercial forestry operations while preserving essential ecosystem services. Originality/Value: This study contributes to the literature by introducing an innovative application of multi-criteria evaluation in assessing environmental fragility within forest landscapes, specifically in the context of forest road planning. The research combines various environmental criteria into a comprehensive fragility map, offering a nuanced understanding of landscape vulnerability that is less commonly addressed in existing studies. Notably, this methodology focused on forest roads has not been previously explored in the literature, highlighting the unique contribution of this research to the field.The relevance and value of this research are evidenced by its potential to influence forest management practices, particularly in the sustainable planning and maintenance of forest roads.

From reduction to rebalancing: Insights into the long-term effects of sediment dredging on nitrogen transformations in river ecosystems

Although sediment dredging is a widely employed water management and restoration technique for the removal of internal nitrogen (N), the long-term effects of dredging on N transformation in dredged rivers remain largely undetermined. In this study, we investigated the effects of dredging on N transformation processes spanning three years at ten sites in the purple-soil watershed within the middle reaches of the Fu River Basin. We combined isotopic and molecular techniques to provide novel insights into the interactions associated with microbial utilization capacities between sediment and river water before, during, and after dredging. Initially, dredging was found to significantly reduce the total nitrogen content by approximately 75 %, although over time, there was a slight increase in concentrations. Secondly, significant reductions in microbial richness and diversity were detected in both river water and sediment, with 39 classes reduced, 12 new classes emerging, and an increase in archaea, reshaping the microbial community. Lastly, dredging was found to promote a significant shift in functional contributions, with increases in the abundance of key enzyme activities (1.7.5.1 and 1.7.2.5) and denitrification genes (nirK, norB, and nosZ). This enhancement notably promoted denitrification and dissimilatory nitrate reduction to ammonium (DNRA), accompanied by significant environmental changes in sediment and river water. These changes facilitated the removal of nitrates in the Xiangshuitan watershed. Our study overcomes the limitations associated with watershed and microenvironment scales, providing insights into the mechanisms where by dredging activities influence the interplay between external and internal N transformations.

Флюидный режим образования вторичных доломитов в палеозойских карбонатных коллекторах Хасырейского месторождения (вал Гамбурцева)

The search for hydrocarbon deposits in the sediments of the Lower Paleozoic complex of the Timan-Pechora oil and gas province, which are associated with the main prospects for increasing reserves, is a relevant topic for research. It is necessary to understand the formation processes of carbonate reservoirs within the complex under consideration to develop a strategy for predicting the structure of the complex reservoirs. Obtaining data on the parameters of the fluid regime of the formation of secondary dolomites in the Paleozoic carbonate reservoirs of the Khasyrey field (Gamburtsev swell) was the aim of the study. We studied primary fluid inclusions in dolomite and anhydrite cements filling vuggy voids in reservoir rocks. We showed that the inclusions contained up to 10 vol. % of the gas phase, which was represented by methane and water vapor. The liquid phase was characterized by a substantially chloride-calcium composition, the salinity is 13.5–23.5 wt. % NaCl-eq. These data might indicate the formation of cavities and cements of secondary dolomites from moderate-temperature solutions of high salinity, which were formed as a result of mixing sedimentation (primary marine) waters and brines of hydrothermal vents. The products of evaporite dissolution in the presence of hydrocarbons and sulfate reduction processes were the most likely source and supplier of the fluids, both the formation of leaching caverns in the rock and the cements performing them. Fluids could enter the upper floors of the section from hydrothermal sources in the basement zones and lower horizons of the sedimentary cover through a system of faults and cracks during tectonic activation.

Distribution of Np, Pu and Am in water, suspended matter, and bottom sediments of Peter the Great Bay

The content of237Np,239,240Pu, and241Am in seawater, suspended matter, and bottom sediment cores of the Ussuri and Amur Bays, sampled in July 2021 and August 2022, was analyzed. The activity concentrations of237Np,239,240Pu, and241Am in the water of Peter the Great Bay were determined for the first time and were found to be equal to (19–105) × 10–3, 2.0–5.3, and 24.1–33.5 mBq/m3, respectively. The activity concentrations as well as the239Pu/240Pu isotope ratio (~0.18) in the bottom sediments definitely indicate that global fallout is the main source of plutonium in the investigated territory. The sedimentation rates were determined for the Amur Bay (in the Razdolnaya River estuary), 0.9 mm/year, and for the Ussuri Bay, 4.1 mm/year. Actinide transfer coefficients were determined for Peter the Great Bay in the system dissolved forms, including colloids–suspended matter–bottom sediment.

Seasonal and annual variations of sediment trapping and particulate organic carbon burial in Yellow River reservoirs

The Yellow River is distinguished by the highest sediment load in mainland China and significant siltation in artificial reservoirs along its main channel, reducing water availability, sediment trapping, and carbon burial in the hydrological project. Since 2002, the Water Sediment Regulation Scheme (WSRS) has been progressively implemented as a hydraulic management strategy to mitigate reservoir sedimentation in the middle-lower basin reservoirs. However, this substantial release of sediment and water has also affected river morphology, carbon burial, and sediment trapping.This research assesses the evolution of particulate organic carbon burial and sediment trapping in eight Yellow River reservoirs from 2002 to 2018, covering the upper and middle-lower basins and two reservoirs in the Yiluo River sub-basin. We calculated the annual and seasonal variations using hydrological data from 11 stations along the Yellow River. A hydrological framework was developed to calculate sediment trapping, and a Monte Carlo analysis was performed to estimate particulate organic carbon burial across all the evaluated reservoirs.We found that sediment trapping and carbon burial in upper basin reservoirs are most influenced by shifts in the precipitation regime, particularly by natural events such as severe droughts or heavy rainfall. A strong correlation was observed between annual precipitation variations and sediment load. In middle-lower basin reservoirs, the major artificial sediment regulation is strongly linked to a significant reduction in sediment trapping and particulate organic carbon burial. This impact is especially notable in the Yiluo River Sub-basin reservoirs, which have experienced a >90 % reduction compared to levels before the WSRS implementation.Finally, we highlight the consequences of climate change and artificial water management strategies in reservoirs, demonstrating how both affect their capacity for sediment trapping and impact their role as significant carbon sinks.

Pharmaceuticals and personal care products and heavy metals in the Ganga River, India: Distribution, ecological and human health risk assessment

In the present study, pharmaceuticals and personal care products (PPCPs), endocrine disrupting compounds (EDCs), and heavy metals (HMs), were measured in water and sediment of the Ganga River during summer and winter seasons for two consecutive years. Additionally, this study estimated the ecological and human health risks associated with PPCPs, EDCs, and HMs. HMs detected in the range of not detected (n.d.) to 23.59 μg/L and 0.01–391.44 μg/g in water and sediment samples, respectively. All studied HMs were within the permissible limits, except for As in water, and Cr and Ni in sediment. The geo-accumulation index (Igeo) indicated that Cr (0.71–5.98) and Pb (0.90–3.90) had high Igeo compared to other metals in sediment samples. Pb showed the highest ecological risk, followed by Cd, Co, Ni, Cu, Cr, As, and Zn. The maximum potential ecological risk index was observed at site G8. The hazard index (HI) value for water (0.08–0.89) and sediment (0.02–0.29) intake by adults remained within the acceptable limits, except at sites G8 (1.27) and G9 (1.34) for water intake. However, for children, the HI value was above the acceptable limit for water intake at sites G4 to G13 and for sediment at site G8. Among the studied compounds, metformin, triclosan, triclocarban, diclofenac, and methylparaben were the most abundant compounds present in the Ganga River. PPCPs and EDCs detected in the range of n.d. to 5850.04 ng/L and n.d. to 1080.41 ng/g in water and sediment samples, respectively. The environmental risk assessment identifies the maximum ecological risk in water exhibited by triclocarban followed by 17α-ethinylestradiol (EE2), diclofenac, and triclosan, while in sediment, the maximum ecological risk exhibited by triclocarban, followed by EE2, 17 β-estradiol (E2), triclosan, and diclofenac. However, none of the compounds showed human health risk, except for EE2, E2, and atenolol.

Microplastic Concentrations in Sediments and Waters Do Not Decrease in Two Rivers Flowing Through the Kruger National Park, South Africa

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.

Determination of microplastics in sediment, water, and fish across the Orange-Senqu River basin

Microplastics are increasingly recognised as posing a significant environmental threat across systems. Their pervasive presence in freshwater poses a serious concern, given the heavy reliance of both humans and biodiversity on healthy, functioning freshwater ecosystems. Acknowledgment of the potential risks led the transboundary Orange-Senqu River Commission (ORASECOM) to include sampling for microlitter (primarily microplastics) in riverine sediment, surface water, and fishes, across Southern Africa as part of the third Joint Basin Survey (JBS3) in 2021. The aim was to establish a first, basin-wide estimate of microlitter contamination across compartments, setting a baseline for further monitoring. The survey showed that the abundance of microlitter in riverine sediment (0 – 4000 particles.kg-1 dry weight (dw)) and riverine water (1.00 ± 0.71 – 69.75 ± 68.55 SD items.L-1) varied considerably between sample sites, with no correlation between the two. The abundance of microlitter in fishes was low (average of 0.7 ± 0.4 items.individual-1). Course resolution analyses suggested that microlitter concentrations in riverine sediment and riverine water at each site did not correlate with land use directly upstream, though variation in microlitter abundance did isolate some hotspots of contamination. Discharge data collected from nine gauging stations near sampling sites confirmed that low flows prevailed in the system during the study, with high flows occurring approximately 5 months prior during the summer months. There is some variation in river flow across the catchment which is a likely driver of microlitter transport. This was evident in the polymer composition for sediment and water samples. Based on the average discharge at each gauging station and microlitter concentrations measured in riverine water, the estimated microlitter load ranged from ∼889 particles.s-1 to ∼17.9 million particles.s-1, with a substantial amount ending likely up in the mudbelt adjacent to the Orange River mouth. This assessment provides a first insight into the characterisation and distribution of microlitter in multiple compartments across the Orange-Senqu River basin. Overall, the findings highlight the need for continued monitoring across compartments at catchment scales to improve our understanding of microplastic pathways into and within riverine systems.

Spatiotemporal evolution and driving mechanism of Dongting Lake based on 2005–2020 multi-source remote sensing data

As one of the largest inland lakes in China, Dongting Lake has attracted widespread attention owing to its rich natural resources, unique geographical landscape, and important ecological functions. Recently, Dongting Lake has experienced phenomena such as an early dry season and backflow during the flood season. Multi-source remote sensing data and the normalised difference water index (NDWI) threshold method were used to systematically analyse the water area of the lake from 2005 to 2020. Additionally, it employed a centre of gravity migration model and a geographic detector model to investigate the lake's evolution patterns and driving mechanisms. The research identified notable fluctuations in Dongting Lake's water area during this period, with a particularly sharp decline in 2006—from 1509.74 km2 to 815 km2, marking a decrease of 694.74 km2 and a shrinkage rate of 46.01 %. Spatial analysis indicated that the centre of gravity of these water areas changed primarily between Nandashan Town, the Dongting Lake Management Committee, Wanzihu Township, and Qingtan Township, underscoring their significant influence on lake dynamics, including runoff, surface water availability, sediment deposition, and precipitation, all of which displayed strong positive correlations (Pearson coefficients of 0.57, 0.68, and 0.63, respectively), whereas population density showed a negative correlation (Pearson coefficient of −0.56). Furthermore, the study highlighted the substantial impact of the Digital Elevation Model (DEM) and its interaction with slope and aspect on Dongting Lake's evolution, with Q values of 0.537 and 0.543, respectively, emphasising their critical roles in shaping lake area changes and providing a crucial scientific basis for enhancing the understanding and effective management of water resources in the Dongting Lake Basin through comprehensive analysis of its spatiotemporal evolution and driving mechanisms.

Study on the effect of modified Fe3O4@SiO2@PAC magnetic seeds on magnetic flocculation separation of ballast water sediments

ABSTRACT In this study, modified Fe3O4@SiO2@PAC magnetic seeds were prepared to explore the separation efficiency and mechanism of algae and particles in high-turbidity ballast water under different influencing factors. The results showed that when the mass ratio of Fe3O4@SiO2 and PAC was 1:3, the removal rate of algae and turbidity was increased by 20 and 15.7% compared with the unmodified magnetic seed. When the dosage of magnetic seed was 217.5 mg/L, the stirring time was 129.2 s, the stirring speed was 211.6 r/min, and the pH was 8, the removal rates of turbidity and algae were 83.23 and 97.85%, respectively. The removal rates of algae and turbidity by the secondary magnetic seeds after compounding reached 97.8 and 96.57% of the first utilisation. Through scanning electron microscopy, transmission electron microscopy, and the adsorption kinetics model, it was found that the magnetic seed removed algae and turbidity through electrostatic adsorption generated by PAC. Among them, the role of SiO2 as an intermediate layer is to make PAC a better composite on the magnetic seed so that it can play the greatest role.

Consequences of intense drought on CO2 and CH4 fluxes of the reed ecosystem at Lake Neusiedl

Reed (Phragmites australis) dominated wetlands are commonly known as strong carbon (C) sinks due to the high productivity of the reed plant and C fixation in the wetland soil. However, little is known about the effects of drought on reed-dominated wetlands and the possibility of Pannonian reed ecosystems being a source of greenhouse gases (GHG). The drought at Lake Neusiedl had a particular impact on the water level, but also had consequences for the reed belt. Therefore, we investigated the drought-influenced C fluxes and their drivers in the reed ecosystem of this subsaline lake over a period of 4.5 years (mid-2018 to 2022). We applied eddy covariance technique to continuously quantify the vertical turbulent GHG exchange between reed belt & atmosphere and used vegetation indices to account for reed growth. Methane emissions decreased by 76% from 9.2 g CH4-C m-2a-1 (2019) to 2.2 g CH4-C m-2 a-1 (2022), which can be explained by the falling water level, the associated drying out of the reed belt and its consequences. Carbon dioxide emissions initially decreased by 85% from 181 g CO2-C m-2 a-1 (2019) to 27 g CO2-C m-2 a-1 (2021), but then increased to twice the 2019 level in 2022 (391 g CO2-C m-2 a-1). Due to the drying reed belt, the reed initially grew into formerly water-covered areas within the reed belt, especially in 2021, leading to higher photosynthesis through 2021. This development stopped and even reversed in 2022 as a consequence of the sharp decrease in sediment water content from about 65 to 32 Vol-% in mid-2022. Overall, drought led to a decoupling of the reed ecosystem from the open lake area and developed the wetland into a strong C source.