Assessment of the level and risk of radioactive hazards in coastal sediments in northern Vietnam.

Radioactivity in coastal sediments in northern Vietnam was examined using data from five sediment cores to assess radioactivity concentrations and radiation risk indices. Radiation risk indices included radium equivalent activity (Raeq), the absorbed dose rate (ADR), the annual effective dose equivalent (AEDE), the activity utilization index (AUI), the external hazard index (Hex), the representative level gamma index (Iγr), and the annual gonadal effective dose rate (AGDE). The radioactivity concentrations of 40K, 232Th, 226Ra, 238U, and 137Cs were 567, 56.1, 35.1, 37.9, and 1.18 Bq/kg, respectively. The average concentrations of 40K, 232Th, 226Ra, and 238U were above the global average at five sites, except for 137Cs, which was low. The Raeq, Hex, and AUI indices were below the recommended values, while the AEDE, ADR, AGDE, and Iγr indices were above the recommended values. Moreover, 40K, 232Th, 226Ra, and 238U had significant impacts on the radiation hazard indices Raeq, ADR, AEDE, Iγr, AUI, Hex, and AGDE. There are three coastal sediment groups on the northern coast of Vietnam: Group 1 has a higher radioactivity and radiation risk index than Group 2 but a lower value than Group 3. Group 3 had the highest radioactivity and radiation risk index. The values of 40K, 232Th, 226Ra, and 238U and the ADR, AUI, Iγr, and AGDE indices in the sediment threaten the living environment.

Microbial diversity and oil biodegradation potential of northern Barents Sea sediments.

The Arctic, an essential ecosystem on Earth, is subject to pronounced anthropogenic pressures, most notable being the climate change and risks of crude oil pollution. As crucial elements of Arctic environments, benthic microbiomes are involved in climate-relevant biogeochemical cycles and hold the potential to remediate upcoming contamination. Yet, the Arctic benthic microbiomes are among the least explored biomes on the planet. Here we combined geochemical analyses, incubation experiments, and microbial community profiling to detail the biogeography and biodegradation potential of Arctic sedimentary microbiomes in the northern Barents Sea. The results revealed a predominance of bacterial and archaea phyla typically found in the deep marine biosphere, such as Chloroflexi, Atribacteria, and Bathyarcheaota. The topmost benthic communities were spatially structured by sedimentary organic carbon, lacking a clear distinction among geographic regions. With increasing sediment depth, the community structure exhibited stratigraphic variability that could be correlated to redox geochemistry of sediments. The benthic microbiomes harbored multiple taxa capable of oxidizing hydrocarbons using aerobic and anaerobic pathways. Incubation of surface sediments with crude oil led to proliferation of several genera from the so-called rare biosphere. These include Alkalimarinus and Halioglobus, previously unrecognized as hydrocarbon-degrading genera, both harboring the full genetic potential for aerobic alkane oxidation. These findings increase our understanding of the taxonomic inventory and functional potential of unstudied benthic microbiomes in the Arctic.

A novel assessment of potentially toxic elements (PTEs) in water and sediment samples from the Indus River, Pakistan: An ecological risk assessment approach.

Pakistan, a country with limited water resources and highly vulnerable to the adverse effects of climate change, faces numerous challenges in managing its water supply. In this sense, this study assessed potentially toxic elements (PTEs) in the surface water and sediments of Pakistan's Indus River and its tributaries. Key water quality parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) were determined, with respective average values of 7.1, 40 µS/cm, and 208 mg L-1. The concentrations of Cd, Cr, Cu, Ni, and Zn in surface water samples averaged 26 µg L-1, 0.9 µg L-1, 1.4 µg L-1, 22 µg L-1, and 2.1 µg L-1, respectively. The general sediment PTE profile was Ni > Cd > Zn > Cu > Cr. Certain PTE levels exceeded recommended thresholds, indicating the establishment of environmental pollution. Calculated geo-accumulation index values suggested moderate to heavy pollution levels in sediment, with PERI (404) values reinforcing the ecological risk posed by elevated PTE concentrations. Furthermore, significant correlations were observed between specific PTE pairs in both water and sediment samples. This study contributes with novel insights into the distribution and ecological implications of PTE contamination in the Indus River and its tributaries, paving the way for ecological risk management efforts.

Distribution of 137Cs specific activity in river sediments of the Barents Sea basin (Nenets Autonomous Okrug, Russian Arctic).

This article focuses on the study of the distribution of 137Cs in the bottom sediments of Arctic rivers of the Barents Sea basin (using the example of the Nenets Autonomous Okrug, Russian Arctic). This research is relevant due to the poorly studied region and the significant number of radiation-hazardous facilities in the Arctic zone of Russia, both those currently in operation and those that are "nuclear heritage sites". The study of 137Cs specific activity in bottom sediments was carried out in the period from 2020 to 2023 in the rivers Chizha, Nes, Vizhas, Oma, Pechora (river delta), as well as the rivers Kolva and Usa (first and second order tributaries, respectively, of the Pechora River). A total of 199 samples were collected. In addition to 137Cs specific activity, the samples were analysed for sediment particle size distribution, organic matter content, carbonate content and ash content. The 137Cs specific activity mainly ranged from the minimum detectable specific activity to 5.4 ± 0.8 Bq·kg-1. In the Nes River basin (Kaninskaya tundra), the 137Cs content in bottom sediments reached 36.0 ± 3.2 Bq·kg-1 (in the case of lake sediments) and 22.9 ± 3.7 Bq·kg-1 (in the case of river sediments), values that are higher than those of the North-West of Russia. Considering the large area of the study area (Kaninskaya tundra, Pechora river delta, southern part of Bolshezemelskaya tundra) and the similarity of physical and chemical parameters of the studied rivers, it is possible to assume the existence of a zone of increased radionuclide content in the Nes river basin. This may be due to the runoff from the Nes River catchment area, its hydrological features, and the accumulation of 137Cs in the small fractions of bottom sediments. The results confirm the conclusions of previous soil studies in the Nes river basin. The main sources of elevated 137Cs content are global atmospheric deposition and the Chernobyl Nuclear Power Plant accident.

Divergent marine anaerobic ciliates harbor closely related Methanocorpusculum endosymbionts.

Ciliates are a diverse group of protists known for their ability to establish various partnerships and thrive in a wide variety of oxygen-depleted environments. Most anaerobic ciliates harbor methanogens, one of the few known archaea living intracellularly. These methanogens increase the metabolic efficiency of host fermentation via syntrophic use of host end-product in methanogenesis. Despite the ubiquity of these symbioses in anoxic habitats, patterns of symbiont specificity and fidelity are not well known. We surveyed two unrelated, commonly found groups of anaerobic ciliates, the Plagiopylea and Metopida, isolated from anoxic marine sediments. We sequenced host 18S rRNA and symbiont 16S rRNA marker genes as well as the symbiont ITS region from our cultured ciliates to identify hosts and their associated methanogenic symbionts. We found that marine ciliates from both of these co-occurring, divergent groups harbor closely related yet distinct intracellular archaea within the Methanocorpusculum genus. The symbionts appear to be stable at the host species level, but at higher taxonomic levels, there is evidence that symbiont replacements have occurred. Gaining insight into this unique association will deepen our understanding of the complex transmission modes of marine microbial symbionts, and the mutualistic microbial interactions occurring across domains of life.

Partitioning of metals in the tissues and cytosolic fraction of Cerastoderma edule.

The concentrations of Cd, Cu and Zn have been determined in the tissues and the cytosolic fraction of the common cockle, Cerastoderma edule, collected from sediments in the Tamar, Plym and Avon estuaries (South West, England). Metal concentrations in the tissues of C. edule from the Avon were lower than those from the Tamar and Plym, except for Cu in the digestive gland. Significant statistical relationships were only obtained between the total sedimentary metal concentrations and Cd in the body of C. edule and Cu in the digestive gland. The cytosolic fraction was extracted from each of the tissues and separated for protein analysis thereby allowing determination of the metal contents in high molecular weight (HMW) compounds, metallothionein-like proteins (MTLP) and very low molecular weight (VLMW) compounds. The digestive glands of C. edule from the Avon had relatively low concentrations of MTLP, whereas MTLP concentrations in the digestive gland of cockles from the Tamar and Plym were higher. The cytosolic fraction of C. edule had relatively low total Cd and Cu concentrations associated with MTLP, whereas Zn was preferentially associated with the HMW and the VLMW components. The results are relevant to metal distributions in C. edule and the role of cytosols in the management of metals by C. edule and other invertebrates.

Bottom sediments as an indicator of the restoration potential of lakes-a case study of a small, shallow lake under significant tourism pressure.

The study covered a small, shallow lake, intensively used for recreation (sailing, tourist services and port infrastructure). This study aimed to determine the spatial differentiation of bottom sediments and the potential for phosphorus release in five zones, differing mainly in the type of recreation, depth, direct catchment management, shoreline management and macrophyte presence. The results were used to propose protective and restoration measures to improve the water quality of the studied lake. The innovation in the study was the detailed analysis of bottom sediments, which can be a significant source of pollution besides the external load from the catchment and tourist pressure, in the planned management of this ecosystem. Examination of the physicochemical properties of the bottom sediments showed a clear variation in both composition and potential for internal phosphorus loading. The sediments from the profundal zone, where the most boating activity was observed, together with the sediments from the shallow zone where the boats dock (mooring zone), had the highest potential to supply phosphorus to the bottom waters. This fact was demonstrated by the highest total phosphorus (TP) concentrations in sediments (up to 1.32 mgPg-1 DW) and the content of the most mobile fractions (up to 33%). The other zones associated with the marina, fuel zone, tributary and canal were not significant sources of phosphorus to the ecosystem. Based on the above results, a restoration method involving the removal of bottom sediments from the bottom zone was proposed, supported, of course, by protective measures in the catchment (maintaining a buffer zone around the lake and limiting the inflow of pollutants with tributary waters). The proposed measures with sustainable tourist pressure should improve water quality and thus contribute to protecting this valuable natural landscape.

Study on the diversity and germination of dinoflagellate cysts in the sediments of foreign ships in Shanghai Port.

The dinoflagellate cysts present in the ballast water sediment of foreign ships in Shanghai Port have not been previously studied. Therefore, sediment samples were collected from the ballast water of 16 foreign ships in Shanghai Port, and the types of dinoflagellate cysts were identified and their abundance was calculated, with a specific focus on the analysis of toxic and harmful dinoflagellates. Moreover, simulations of temperature and salinity conditions throughout the year in the Shanghai port waters were conducted to carry out dinoflagellate cyst germination experiments, with analyze and compare the germinated dinoflagellate cysts under different conditions. Dinoflagellate cysts were found in 100 % of the ship sediment samples, including a total of 9 species of toxic and harmful dinoflagellate cysts. In the germination experiment, 15 °C was found to be the optimal temperature for the germination of dinoflagellate cysts in ballast water sediment, and high salinity is more favorable for cyst germination.

Dewatering and valorizing lake sediments by electroosmotic dewatering for lakes restoration.

Dredging eutrophic lake sediments can improve water quality, but it also requires dewatering and valorizing the dredged material to avoid wasting resources like phosphorus. This study experimentally investigated the basic mechanism and performance of electroosmotic dewatering of 1-L dredged sediments using different electric currents (20 mA, 40 mA, and 60 mA) after gravity filtration. The dewatering performance, moisture content and distribution, effect of electrochemical reaction on dewaterability, energy consumption, and changes in metals and phosphorus (P) distribution and pH values were analyzed. The results indicated that electroosmotic dewatering effectively decreased sediment mass by predominantly eliminating free and a portion of interstitial water, with reductions ranging from 7 to 20%. The optimal duration and current should, however, be considered to balance water removal and energy consumption. Higher moisture removal occurred with 40 mA for 24 h and 60 mA for 6 h, while the energy consumption obtained with 60 mA (0.201 kWh/kg water removed) was significantly lower than that of applying 40 mA for 24 h (0.473 kWh/kg water removed), with the assistance of ohmic heating, resulting in reduced viscosity and water release from capillaries. The tested conditions did not significantly extract heavy metals or P from the sediments, which may facilitate the disposal of the removed water back into the lake and the utilization of the treated sediments for different purposes. This technology is easy to operate and suitable for the treatment of dredged sediments, and the dewatering result is comparable to low pressurized filtration but at low energy consumption.

Low Bacterial Diversity and Nitrate Levels in Cores from Deep Boreholes in Pristine Karst.

This study investigates the nitrate gradients within the deep biosphere of karst carbonate rocks and their resident microbiota. Samples were taken from borehole cores at depths down to 350 m below the surface, collected during geological site investigations for proposed railway tunnels and analysed using 16S rRNA amplicon sequencing. 16S rRNA amplicon sequencing analysis revealed relatively low microbial diversity, which can serve as a reliable indicator of the pristine nature of deep karst. However, some local hotspots of diversity are independent of depth. Pseudomonadota dominated the samples, with Gammaproteobacteria dominating at the class level. The low nitrate content in deep karst, in contrast to higher values closer to the surface, serves as an additional marker of its undisturbed and unpolluted status. Based on the prediction of functional profiles from 16S rRNA sequencing data, nitrates remain low due to indigenous microbial denitrification and assimilatory nitrate reduction. Pathways related to nitrogen fixation, ammonia assimilation, and nitrification were not confirmed. When elevated nitrate levels are observed in karst, they are most probably related to anthropogenic activities. Environmental factors other than depth and nitrate content play an important role in shaping bacterial communities.

Development of Multiplex RT qPCR Assays for Simultaneous Detection and Quantification of Faecal Indicator Bacteria in Bathing Recreational Waters.

In this study, we designed and validated in silico and experimentally a rapid, sensitive, and specific multiplex RT qPCR for the detection and quantification of faecal indicator bacteria (FIB) used as microbiological references in marine bathing water regulations (Escherichia coli and intestinal enterococci). The 16S rRNA gene was used to quantify group-specific enterococci and Escherichia/Shigella and species-specific such as Enterococcus faecalis and E. faecium. Additionally, a ybbW gene encoding allantoin transporter protein was used to detect E. coli. An assessment of marine coastal systems (i.e., marine water and sediment) revealed that intestinal enterococci were the predominant group compared to Escherichia/Shigella. The low contribution of E. faecalis to the intestinal enterococci group was reported. As E. faecalis and E. faecium were reported at low concentrations, it is assumed that other enterococci of faecal origin are contributing to the high gene copy number of this group-specific enterococci. Moreover, low 16S rRNA gene copy numbers with respect to E. faecalis and E. faecium were reported in seawater compared to marine sediment. We conclude that marine sediments can affect the quantification of FIBs included in bathing water regulations. Valuing the quality of the marine coastal system through sediment monitoring is recommended.

Development of High Surface Area Organosilicate Nanoparticulate Thin Films for Use in Sensing Hydrophobic Compounds in Sediment and Water.

The scope of this study was to apply advances in materials science, specifically the use of organosilicate nanoparticles as a high surface area platform for passive sampling of chemicals or pre-concentration for active sensing in multiple-phase complex environmental media. We have developed a novel nanoporous organosilicate (NPO) film as an extraction phase and proof of concept for application in adsorbing hydrophobic compounds in water and sediment. We characterized the NPO film properties and provided optimization for synthesis and coatings in order to apply the technology in environmental media. NPO films in this study had a very high surface area, up to 1325 m2/g due to the high level of mesoporosity in the film. The potential application of the NPO film as a sorbent phase for sensors or passive samplers was evaluated using a model hydrophobic chemical, polychlorinated biphenyls (PCB), in water and sediment. Sorption of PCB to this porous high surface area nanoparticle platform was highly correlated with the bioavailable fraction of PCB measured using whole sediment chemistry, porewater chemistry determined by solid-phase microextraction fiber methods, and the Lumbriculus variegatus bioaccumulation bioassay. The surface-modified NPO films in this study were found to highly sorb chemicals with a log octanol-water partition coefficient (Kow) greater than four; however, surface modification of these particles would be required for application to other chemicals.

Antibiotics in Surface Sediments from the Anning River in Sichuan Province, China: Occurrence, Distribution, and Risk Assessment.

The occurrence, distribution, and ecological risk assessment of 36 antibiotics from five groups, including macrolides (MLs), fluoroquinolones (FQs), tetracyclines (TCs), amphenicols (APs), and sulfonamides (SAs), were investigated for the first time in the Anning River, Sichuan Province, China. The results show that antibiotics were widely present in the sediments of the Anning River, with a total of 22 antibiotics detected. FQs were among the most abundant antibiotics, followed by TCs, MLs, APs, and SAs. The total concentrations of antibiotics in surface sediments varied from 0.05 to 53.35 ng/g, with an average of 8.09 ng/g. Among these groups, MLs, FQs, and TCs emerged as the predominant classes of antibiotics. The midstream sediments showed the highest residual levels of antibiotics, with lower levels observed in the downstream and upstream sediments. Anthropogenic activities, such as human clinical practices and animal breeding, might be sources of antibiotics released into the river. An ecological risk assessment revealed that trimethoprim from the SA group exhibited high risks, and MLs showed medium risks in the Anning River, whereas most antibiotics presented minimal to low risks. This study provides valuable information on antibiotic pollution in the upstream region of the Yangtze River, and future management measures are needed for the Anning River.

Macroplastic and Microparticle Pollution in Beach Sediments from Urias Coastal Lagoon (Northwest Mexico).

This study investigates the occurrence and characteristics of macroplastic and polymer microparticles in the Urias coastal lagoon's beach sediments, in northwest Mexico. Coastal lagoons, productive and vulnerable ecosystems, are impacted significantly by anthropogenic activities, leadings to their pollution by various contaminants, including plastics. Our research involved sampling sediments from four sites within the lagoon that were influenced by different human activities such as fishing, aquaculture, thermoelectric power plant operations, industrial operations, and domestic wastewater discharge. Our methodology included collecting macroplastics and beach sediment samples, followed by laboratory analyses to identify the plastic debris' size, shape, color, and chemical composition. The results indicated a notable presence of macroplastic items (144), predominantly bags, styrofoam, and caps made of polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). The polymer microparticles were mainly fibers, with cotton and polyester as the most common polymers, suggesting a significant contribution from clothing-related waste. The dominant colors of the microparticles were blue and transparent. High densities were observed in areas with slower water exchange. Our findings highlight the urgent need for better waste management practices to mitigate plastic pollution in coastal lagoons, preserving their ecological and economic functions.

Relationship between human activities and environmental changes in the southern Tibetan Plateau since the Little Ice Age.

The Tibetan Plateau (TP) is one of the most challenging areas for human long-term settlement due to its extreme living environment. Understanding the relationship between human activities and environmental changes in this extreme environment is important and can provide a historical reference for adapting to future climate change. In this study, we took the Angren Basin in the southern TP as a case study to elucidate the relationship since Little Ice Age (LIA). Using fecal stanol in feces, lake and river surface sediments, surface soils, and sediment core, we found that specific indices S1 and S2 from the composition of coprostanol, epicoprostanol, 5ß-ethylcoprostanol and 5ß-ethylepicoprostanol can reflect changes in human population and herbivores, respectively. Through the comparison between environmental changes determined by grain size, elements, sedimentation rate, and other climate records, the relationship between human activities and environmental changes was interpreted. Our results indicate that: (i) during 1480-1820 CE, the fecal stanols in lake sediments mainly originated from livestock, and the human population was low. In contrast, during 1820-2021 CE, the proportion and flux of S1 have been continuously increasing, indicating significant population growth. (ii) During the middle LIA, the cold-dry climate inhibited the development of agriculture and farming. However, the increased precipitation during the late LIA promoted that development, resulting in an increase in human population and livestock in a short term. (iii) Since 1951, people have reclaimed wasteland and developed husbandry, leading to increased soil erosion. (iv) Over the past 40 years, with a warm-humid climate and good policy support, human activities, such as agriculture and husbandry, have rapidly increased, but soil erosion has declined in the recent 20 years due to good soil-water conservation efforts. This study sheds light on the relationship between human activities and environmental changes and provides insights into future climate change responses.

Utilities of environmental radioactivity tracers in assessing sequestration potential of carbon in the coastal wetland ecosystems.

Demand for accurate estimation of coastal blue carbon sequestration rates in a regular interval has recently surged due to the increasing awareness of nature-based climate solutions to alleviate adverse impacts stemming from the recent global warming. The robust estimation method is, however, far from well-established. The international community requires, moreover, to quantify its effect of "management." This article tries to provide the environmental isotope community with basic biophysical features of coastal blue carbon ecosystems to identify a suitable set of environmental isotopes for promoting coastal ocean-based climate solutions. This article reviews (i) the primary biophysical characteristics of coastal blue carbon ecosystems and hydrology, (ii) their consequential impact on the accumulation and preservation of organic carbon (OC) in the sediment column, (iii) suitable environmental isotopes to quantifying the sedimentary organic carbon accumulation, outwelling of the carbon-containing byproducts of decomposition of biogenic organic matter and acid neutralizing alkalinity produced in situ sediment to the offshore. Above-ground biomass is not cumulative over the years except for mangrove forests within coastal blue carbon systems. Non-gaseous carbon sequestration and loss occur mainly as a form of sediment organic carbon (SOC) and dissolved carbon in an intertidal and subtidal bottom sediment body in a slow, patchy, and dispersive way, on which this article focuses. Investigating environmental radionuclides is probably the most cost-effective effort to contribute to defining the offshore spatial extent of coastal blue carbon systems except for seagrass beds (e.g., Ra isotopes), to quantify millimeter per year scale carbon accretion and loss within the systems (e.g., 7Be, 210Pb) and a liter per meter of coastline per a day scale water movement from the systems (Ra isotopes). A millimeter-scale spatial and an annual (or less) time-scale resolution offered by the use of environmental isotopes would equip us with a novel tool to enhance the carbon storage capacity of the coastal blue carbon system.

Transoceanic ships as a source of alien dinoflagellate invasions of inland freshwater ecosystems.

Ships' ballast water and sediments have long been linked to the global transport and expansion of invasive species and thus have become a hot research topic and administrative challenge in the past decades. The relevant concerns, however, have been mainly about the ocean-to-ocean invasion and sampling practices have been almost exclusively conducted onboard. We examined and compared the dinoflagellate cysts assemblages in 49 sediment samples collected from ballast tanks of international and domestic routes ships, washing basins associated with a ship-repair yard, Jiangyin Port (PS), and the nearby area of Yangtze River (YR) during 2017-2018. A total of 43 dinoflagellates were fully identified to species level by metabarcoding, single-cyst PCR-based sequencing, cyst germination and phylogenetic analyses, including 12 species never reported from waters of China, 14 HABs-causing, 9 toxic, and 10 not strictly marine species. Our metabarcoding and single-cyst sequencing also detected many OTUs and cysts of dinoflagellates that could not be fully identified, indicating ballast tank sediments being a risky repository of currently unrecognizable invasive species. Particularly important, 10 brackish and fresh water species of dinoflagellate cysts (such as Tyrannodinium edax) were detected from the transoceanic ships, indicating these species may function as alien species potentially invading the inland rivers and adjacent lakes if these ships conduct deballast and other practices in fresh waterbodies. Significantly higher numbers of reads and OTUs of dinoflagellates in the ballast tanks and washing basins than that in PS and YR indicate a risk of releasing cysts by ships and the associated ship-repair yards to the surrounding waters. Phylogenetic analyses revealed high intra-species genetic diversity for multiple cyst species from different ballast tanks. Our work provides novel insights into the risk of bio-invasion to fresh waters conveyed in ship's ballast tank sediments and washing basins of shipyards.

Characteristics and risk assessment of potentially toxic elements pollution in river water and sediment in typical gold mining areas of Northwest China.

To assess the concentration characteristics and ecological risks of potential toxic elements (PTEs) in water and sediment, 17 water samples and 17 sediment samples were collected in the Xiyu River to analyze the content of Cr, Ni, As, Cu, Zn, Pb, Cd and Hg, and the environmental risks of PTEs was evaluated by single-factor pollution index, Nemerow comprehensive pollution index, potential ecological risk, and human health risk assessment. The results indicated that Hg in water and Pb, Cu, Cd in sediments exceeded the corresponding environmental quality standards. In the gold mining factories distribution river section (X8-X10), there was a significant increase in PTEs in water and sediments, indicating that the arbitrary discharge of tailings during gold mining flotation is the main cause of PTEs pollution. The increase in PTEs concentration at the end of the Xiyu River may be related to the increased sedimentation rate, caused by the slowing of the riverbed, and the active chemical reactions at the estuary. The single-factor pollution index and Nemerow pollution index indicated that the river water was severely polluted by Hg. Potential ecological risk index indicated that the risk of Hg in sediments was extremely high, the risk of Cd was high, and the risk of Pb and Cu was moderate. The human health risk assessment indicated that As in water at point X10 and Hg in water at point X9 may pose non-carcinogenic risk to children through ingestion, and As at X8-X10 and Cd at X14 may pose carcinogenic risk to adults through ingestion. The average HQingestion value of Pb in sediments was 1.96, indicating that the ingestion of the sediments may poses a non-carcinogenic risk to children, As in the sediments at X8-X10 and X15-X17 may pose non-carcinogenic risk to children through ingestion.

Effects of acid mine drainage and sediment contamination on soil bacterial communities, interaction patterns, and functions in alkaline desert grassland.

Acid mine drainage and sediments (AMD-Sed) contamination pose serious ecological and environmental problems. This study investigated the geochemical parameters and bacterial communities in the sediment layer (A) and buried soil layer (B) of desert grassland contaminated with AMD-Sed and compared them to an uncontaminated control soil layer (CK). The results showed that soil pH was significantly lower and iron, sulfur, and electroconductivity levels were significantly higher in the B layer compared to CK. A and B were dominated by Proteobacteria and Actinobacteriota, while CK was dominated by Firmicutes and Bacteroidota. The pH, Fe, S, and potentially toxic elements (PTEs) gradients were key influences on bacterial community variability, with AMD contamination characterization factors (pH, Fe, and S) explaining 48.6 % of bacterial community variation. A bacterial co-occurrence network analysis showed that AMD-Sed contamination significantly affected topological properties, reduced network complexity and stability, and increased the vulnerability of desert grassland soil ecosystems. In addition, AMD-Sed contamination reduced C/N-cycle functioning in B, but increased S-cycle functioning. The results highlight the effects of AMD-Sed contamination on soil bacterial communities and ecological functions in desert grassland and provide a reference basis for the management and restoration of desert grassland ecosystems in their later stages.

Examining the source and composition of organic matter through saturated hydrocarbons, δ13C, and δ15N in a subtropical water reservoir.

The sources of organic matter in the sediments of the Passaúna reservoir, an important water supply for the local population, were thoroughly investigated. The objective was to identify the origins of organic matter through the analysis of saturated hydrocarbons, elemental composition (total organic carbon and total nitrogen), and the content of δ13C and δ15N isotopes. This comprehensive approach allowed us to trace the sources of organic matter and discerns indicating heightened primary productivity within the reservoir. To achieve this, two sediment cores spanning a 140-year interval (1880-2020) were retrieved from the reservoir. Core 2 accumulates the majority of sediments, particularly near the dam area. In these parts, sediment deposits can reach up to 1 m above the pre-impoundment soil. Sediments near the area where core 1 was collected contain more sand, resulting in lower thickness compared to core 2. Sediment core 1 primarily reflects terrestrial sources of organic matter, as supported by stable isotope values of δ13C and δ15N. The δ13C values ranged from -23.0 ‰ to -25.7 ‰ in core 1 and from -28.4 ‰ to -29.2 ‰ in core 2. Meanwhile, the δ15N values ranged from 6.6 ‰ to 10.8 ‰ in core 1 and from 3.8 ‰ to 7.6 ‰ in core 2. The distribution of saturated hydrocarbons revealed that organic matter originates from both allochthonous and autochthonous sources. Periods of intense primary productivity were indicated by the presence of n-C16, n-C17, n-C18, and n-C19 alkanes. Additionally, we observed periods characterized by high primary productivity, indicative of elevated nutrient input likely resulting from increased urbanization and industrial activity in the area.