Long-term stability of the genome structure of the cyanobacterium, Dolichospermum in a deep German lake.

Dolichospermum is a cyanobacterial genus commonly associated with toxic blooms in lakes and brackish water bodies worldwide, and is a long-term resident of Lake Stechlin, northeastern Germany. In recent decades, shifts in the phosphorus loading and phytoplankton species composition have seen increased biomass of Dolichospermum during summer blooms from 1998, peaking around 2005, and declining after 2020. Cyanobacteria are known to rapidly adapt to new environments, facilitated by genome adaptation. To investigate the changes in genomic features that may have occurred in Lake Stechlin Dolichospermum during this time of increased phosphorus loading and higher biomass, whole genome sequence analysis was performed on samples of ten akinetes isolated from ten, 1 cm segments of a sediment core, representing a ∼45-year period from 1970 to 2017. Comparison of these genomes with genomes of extant isolates revealed a clade of Dolichospermum that clustered with the ADA-6 genus complex, with remarkable genome stability, without gene gain or loss events in response to recent environmental changes. The genome characteristics indicate that this species is suited to a deep-chlorophyll maximum, including additional light-harvesting and phosphorus scavenging genes. Population SNP analysis revealed two sub-populations that shifted in dominance as the lake transitioned between oligotrophic and eutrophic conditions. Overall, the results show little change within the population, despite diversity between extant populations from different geographic locations and the in-lake changes in phosphorus concentrations.

Effects of dissolved oxygen changes in the benthic environment on phosphorus flux at the sediment-water interface in a coastal brackish lake.

In semi-enclosed coastal brackish lakes, changes in dissolved oxygen in the bottom layer due to salinity stratification can affect the flux of phosphorus (P) at the sediment-water interface, resulting in short- and long-term water quality fluctuations in the water column. In this study, the physicochemical properties of the water layers and sediments at five sites in Saemangeum Lake were analyzed in spring and autumn for four years, and phosphorus release experiments from sediments were conducted for 20 days under oxic and anoxic conditions during the same period. Sediment total phosphorus (T-P) decreased in autumn compared to spring due to mineralization of organic bound phosphorus, which was the most dominant P fraction. This may be related to the increase in the ratio of PO4-P to T-P in bottom waters in autumn, when hypoxia was frequently observed. The difference in P fluxes between oxic and anoxic conditions indicated that during autumn, as compared to spring, the release of phosphorus could have a more immediate impact on the water column during the formation of hypoxia/anoxia. The main factors influencing changes in P fluxes from sediments were identified through redundancy analysis. Additionally, based on the results of multiple regression analysis, sediment TOC, sediment non-apatite phosphorus, porewater pH, and porewater PO4-P were determined to be the most significant factors affecting P fluxes from sediments, depending on the season or redox conditions. Recently, the increased influx of seawater into Saemangeum Lake has been shown to contribute to water quality improvements in the water column due to a strong dilution effect. However, the sediment environment has shifted towards a more reduced state, leading to increased P release under anoxic conditions. Therefore, for future water quality management within the lake, it is necessary to consistently address the recurring hypoxia and continuously monitor phosphorus dynamics.

[TWO CASES OF ALLERGIC VULVOVAGINITIS DIAGNOSED BY DIRECT MICROSCOPIC URINE SEDIMENT EXAMINATION].

Cedar pollen is known as a typical allergen that causes various allergic symptoms in the nasal mucosa, conjunctiva, and skin. However, inflammation of the vulvar mucosa due to sensitization to cedar pollen is not well-known. We experienced two cases in which the detection of cedar pollen during microscopic urine sediment examination led to the diagnosis of allergic vulvovaginitis caused by cedar pollen. The cases involved a 4-year-old girl and a 10-year-old girl. In both cases, the patients presented with chief complaints of pruritis in the vulva and insomnia due to frequent urination during the season of cedar pollen dissemination. Both patients were afebrile. No inflammatory skin changes such as erythema, swelling, or non-purulent discharge from mucous membranes of the vulva were observed. Microscopic urine sediment examination revealed large amounts of shed cedar pollen. The patients' conditions improved after treatment with oral antihistamines and instruction to dry their underwear indoors. Follow-up blood tests revealed high levels of specific anti-IgE antibodies to cedar pollen, thus confirming a diagnosis of allergic vulvovaginitis due to cedar pollen. Cedar pollen can cause allergic vulvovaginitis. Microscopic urine sediment examination is useful, and when combined with specific IgE antibody testing, leads to an appropriate diagnosis. This disease should also be considered in patients with complaints of vulvar discomfort during the season of cedar pollen dissemination.

Distribution of selenium: A case study of the Drava, Danube and associated aquatic biotopes.

This paper presents the results of the research on the overall distribution of selenium (Se) in various aquatic compartments (water, sediment, plankton and macrophytes) at six selected sites of the Croatian part of the Drava and Danube rivers, the connected floodplain lake and the melioration channel system carried out in two sampling periods (flooding in June and the drought period in September). In addition, the physicochemical water properties, plankton composition and biomass were analysed. Our study revealed low mean Se contents in sediments and water, indicating Se deficiency in the studied freshwater systems. The physicochemical environment, including Se distribution, was primarily influenced by hydrology rather than site-specific biogeochemical and morphological characteristics. The flooding period was characterised by higher Se content in water and higher transparency, nitrate and total nitrogen concentrations than drought conditions. At the river sites, sediment Se content was the highest during the flood period, while at all other sites, higher concentrations were found during the drought, reaching the maximum in the lake. Although Se concentrations were below the threshold for aquatic ecotoxicity, they increased in the following order: water (0.021-0.187 µg Se L-1) < sediments (0.005-0.352 mg Se kg-1) < macrophytes (0.010-0.413 mg Se kg-1) < plankton (0.044-0.518 mg Se kg-1) indicating its possible biomagnification at the bottom of the food chain. Species known for high Se accumulation potential dominated the biomass of the main plankton groups and the composition of the macrophyte community, which may provide a more sensitive and accurate steady-state compartment monitor for Se assessment in freshwater biotopes.

Asynchronous application of modified biochar and exogenous fungus Scedosporium sp. ZYY for enhanced degradation of oil-contaminated intertidal mudflat sediment.

Intertidal mudflats are susceptible to oil pollution due to their proximity to discharges from industries, accidental spills from marine shipping activities, oil drilling, pipeline seepages, and river outflows. The experimental study was divided into two periods. In the first period, microcosm trials were carried out to examine the effect of chemically modified biochar on biological hydrocarbon removal from sediments. The modified biochar's surface area increased from 2.544 to 25.378 m2/g, followed by a corresponding increase in the hydrogen-carbon and oxygen-carbon ratio, indicating improved stability and polarity. In the second period, the effect of exogenous fungus - Scedoporium sp. ZYY on the bacterial community structure was examined in relation to total petroleum hydrocarbon (TPH) removal. The maximum TPH removal efficiency of 82.4% was achieved in treatments with the modified biochar, followed by a corresponding increase in Fluorescein diacetate hydrolysis activity. Furthermore, high-throughput 16S RNA gene sequencing employed to identify changes in the bacterial community of the original sediment and treatments before and after fungal inoculation revealed Proteobacteria as the dominant phylum. In addition, it was observed that Scedoporium sp. ZYY promoted the proliferation of specific TPH-degraders, particularly, Hyphomonas adhaerens which accounted for 77% of the total degrading populations in treatments where TPH removal was highest. Findings in this study provide valuable insights into the effect of modified biochar and the fundamental role of exogenous fungus towards the effective degradation of oil-contaminated intertidal mudflat sediments.

Risk and mechanisms of phosphorus release at the sediment-water interface of lakes in cold and arid regions during non-frozen seasons.

In recent years, the eutrophication of lakes has accelerated in cold arid regions; the release of nutrients from sediments is an important contributor. The sequential extraction method, high-resolution peeper (HR-Peeper), and diffusive gradients in thin films (DGT) techniques were used to study the occurrence characteristics, release risk, and release mechanism of phosphorus (P) at the sediment-water interface (SWI) of Ulanor Wetland in the Hulun Lake Basin, Inner Mongolia, China. The mean total P concentration in overlying water was lower in August than that in May. Dissolved organic P (DOP) or particulate P (PP) was the main form of P in the overlying water. PP dominates in May and DOP in August. Refractory P was the main form of P in sediments. The concentrations of soluble reactive P and DGT-active P in the pore water of the sediment column were higher than those in the overlying water, and the concentrations were higher in August than those in May. Release of P in the wetland sediments occurred during the non-frozen seasons, with a higher risk in August than in May. The good linear correlation between dissolved P, Fe, and Mn in the DGT profiles verified their co-release due to the anaerobic reduction of Fe/Mn oxides. Moreover, alkaline sediments are also conducive to the release of sediment P. This study can provide data and theoretical support for eutrophication control in Ulanor Wetland and other similar water bodies in cold and arid regions.

Changes in the transformation of nitrogen and phosphorus under different microbial communities in sewage pipes.

Microbial communities living in different environments can affect the transformation of nitrogen and phosphorus in sewage pipes. Two different environments were simulated to investigate the differences in the transformation of nitrogen and phosphorus under different microbial communities in the pipe. Results showed that the concentration of nitrogen and phosphorus changed greatly in the first 25-33 days and the first 21 days, respectively, and then remained stable. The decrease in amino acid nitrogen (AAN) concentration and the increase in ammonia nitrogen (NH4 + -N) concentration in the sediments were evident in the contrast group. The concentrations of total phosphorus (TP), dissolved total phosphorus (DTP), and dissolved reactive phosphorus (DRP) in the overlying water and interstitial water decreased, and that of TP in the sediment increased. Some microorganisms in the sediments of both groups are related to the transformation of nitrogen and phosphorus, such as Clostridium_sensu_stricto_1, Sporacetigenium, Norank_f__Anaerolineaceae, Norank_f__norank_o__PeM15, and Caldisericum. The relative abundance of these microorganisms was remarkably differed between the two groups, which partly caused the difference in nitrogen and phosphorus transformation among overlying water, interstitial water, and sediment in the two environments. PRACTITIONER POINTS: The concentration of N and P changed greatly in the first 20-30 days. AAN and NH4 + -N in sediments had greater concentration variation in contrast group. In two groups, TP, DTP, and DRP of water decreased, and TP of sediment increased. Microbe related to the transformation of N and P differed between the two groups.

Marinimicrococcus flavescens gen. nov., sp. nov., a new member of the family Geminicoccaceae, isolated from a marine sediment of the South China Sea.

A Gram-stain-negative, catalase-positive and oxidase-positive, nonmotile, aerobic, light yellow, spherical-shaped bacterial strain with no flagella, designated strain YIM 152171T, was isolated from sediment of the South China Sea. Colonies were smooth and convex, light yellow and circular, and 1.0-1.5×1.0-1.5 µm in cell diameter after 7 days of incubation at 28°C on YIM38 media supplemented with sea salt. Colonies could grow at 20-45°C (optimum 28-35°C) and pH 6.0-11.0 (optimum, pH 7.0-9.0), and they could proliferate in the salinity range of 0-6.0 % (w/v) NaCl. The major cellular fatty acids were summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), C18 : 1 ω7c 11-methyl, C16 : 0, C16 : 1 ω11c, C16 : 1 ω5c, C17 : 1 ω6c and C18 : 1 ω5c. The respiratory quinone was ubiquinone 10, and the polar lipid profile included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol mannoside, one unidentified phospholipid and one unidentified aminolipid. Phylogenetic analyses based on the 16S rRNA gene sequences placed strain YIM 152171T within the order Rhodospirillales in a distinct lineage that also included the genus Geminicoccus. The 16S rRNA gene sequence similarities of YIM 152171T to those of Arboricoccus pini, Geminicoccus roseus and Constrictibacter antarcticus were 92.17, 89.25 and 88.91 %, respectively. The assembled draft genome of strain YIM 152171T had 136 contigs with an N50 value of 134704 nt, a total length of 3 001 346 bp and a G+C content of 70.27 mol%. The phylogenetic, phenotypic and chemotaxonomic data showed that strain YIM 152171T (=MCCC 1K08488T=KCTC 92884T) represents a type of novel species and genus for which we propose the name Marinimicrococcus gen. nov., sp. nov.

Legacy coal mining impacts downstream ecosystems for decades in the Canadian Rockies.

Mountaintop removal coal mining leaves a legacy of disturbed landscapes and abandoned infrastructure with clear impacts on water resources; however, the intensity and persistence of this water pollution remains poorly characterized. Here we examined the downstream impacts of over a century of coal mining in the Crowsnest Pass (Alberta, Canada). Water samples were collected downstream of two historical coal mines: Tent Mountain and Grassy Mountain. Tent Mountain hosts a partially reclaimed surface mine that closed in 1983. Selenium concentrations downstream of Tent Mountain reached 185 µg/L in a lake below the mine spoil pile, and up to 23 µg/L in Crowsnest Creek, which drains the lake and the mine property. Further downstream, a well-dated sediment core from Crowsnest Lake records increases in sediment, selenium, lead, carbon, nitrogen, and polycyclic aromatic compounds that closely tracked the history of mining at Tent Mountain. In contrast, episodic discharge of mine water from abandoned underground adits at Grassy Mountain drive periodic (but short-term) increases in iron, various metals, and suspended sediment. These results underscore the lasting downstream impacts of abandoned and even reclaimed coal mines.

Characterization of phosphate solubilizing bacteria in the sediments of eutrophic lakes and their potential for cyanobacterial recruitment.

Microbes may induce endogenous phosphorus (P) migration from lacustrine sediment. This study focused on the role of phosphate-solubilizing bacteria (PSB) disturbance in affecting the sediment P release and further contributing to cyanobacterial recruitment in Meiliang Bay, Lake Taihu. Gluconic acid was the main mechanism of phosphate solubilizing by PSB. The dominant PSB (Burkholderia) isolated from eutrophic lake sediments was used as a representative to investigate the effects of disturbance on endogenous P release using diffusive gradients in thin films (DGT) and high-resolution dialysis (HR-Peeper). The results show that soluble reactive phosphorus (SRP) and iron (Fe (II)) concentrations could reach 0.51 mg L-1 and 33.56 mg L-1 in pore water, respectively. And the sediment DGT-P and DGT-Fe were relatively reduced by PSB. Subsequent the chlorophyll a (Chl a) concentrations reached peaks of 344.8 µg L-1 in overlying water. The abundance of the dominant PSB (Burkholderia-Caballeronia-Paraburkholderia) were significantly associated with Chl a (P < 0.05) and algal effective state phosphorus (AAP) (P < 0.05), respectively. PSB mainly regulates AAP leaching to pore water and then diffusing across the sediment-water interface to the overlying water, producing the effect of cyanobacteria recruitment. The results provide new insights into early management of cyanobacterial resuscitation in a large eutrophic lake.

New insight into identifying sediment phosphorus sources in multi-source polluted urban river: Effect of environmental-induced microbial community succession on stability of microbial source tracking results.

Identifying sediment phosphorus sources, the key to control eutrophication, is hindered in multi-source polluted urban rivers by the lack of appropriate methods and data resolution. Community-based microbial source tracking (MST) offers new insight, but the bacterial communities could be affected by environmental fluctuations during the migration with sediments, which might induce instability of MST results. Therefore, the effects of environmental-induced community succession on the stability of MST were compared in this study. Liangxi River, a highly eutrophic urban river, was selected as the study area where sediment phosphorus sources are difficult to track because of multi-source pollution and complicated hydrodynamic conditions. Spearman correlation analysis (P < 0.05) was conducted to recognize a close relationship between sediment, bacterial communities and phosphorus, verifying the feasibility of MST for identify sediment phosphorus sources. Two distinct microbial community fingerprints were constructed based on whether excluded 113 vulnerable species, which were identified by analyzing the differences of microorganisms across a concentration gradient of exogenous phosphorus input in microbial environmental response experiment. Because of the lower unknown proportion and relative standard deviations, MST results were more stable and reliable when based on the fingerprints excluding species vulnerable to phosphorus. This study presents a novel insight on how to identify sediment phosphorus sources in multi-source polluted urban river, and would help to develop preferential control strategies for eutrophication management.

Response of a submerged macrophyte (Vallisneria natans) to water depth gradients and sediment nutrient concentrations.

Submerged plants constitute a vital component of shallow lake ecosystems, where water depth and sediment nitrogen­phosphorus content are two key factors influencing their growth. This study focuses on Vallisneria natans and investigates the morphological and physiological changes of V. natans under the interaction of three water depth gradients and two different sediment nutrient levels. It explores the mechanisms through which varying sediment nutrient conditions under different water depths affect the growth of V. natans. The results indicate that both independent and interactive effects of water depth and sediment nutrient status significantly impact the morphology, antioxidant enzyme activity, and photosynthetic pigment content of V. natans, with water depth having a greater influence. To adapt to increased water depth-induced light stress, V. natans responds morphologically by increasing leaf length, leaf width, and decreasing maximum root length. Physiologically, it enhances its antioxidant regulation capacity and photosynthetic efficiency by increasing antioxidant enzyme activity, root vitality, and photosynthetic pigment content to counter weak light stress. However, these adaptations are insufficient to cope with excessively deep waters (200 cm). Sediment nutrient levels primarily control the growth of V. natans by affecting its root system. When sediment nitrogen and phosphorus content is lower, V. natans exhibits greater total root volume and surface area to enhance nutrient absorption efficiency. Water depth not only directly influences the growth of submerged plants but may also impact the migration and transformation of phosphorus in sediments, further exacerbating its effects on the growth of these plants, thus accelerating the regime shift of shallow lakes. Therefore, this study reveals V. natans' response strategies to varying water depths and sediment nutrient levels, determining suitable water levels and sediment nutrient conditions for its growth. These research findings provide a scientific basis for water level management and ecological restoration of submerged aquatic plants in shallow lakes.

Spatial dynamics and risk assessment of phosphorus in the river sediment continuum (Qinhuai River basin, China).

This study investigated the concentration and fractionation of phosphorus (P) using sequential P extraction and their influencing factors by introducing the PLS-SEM model (partial least squares structural equation model) along this continuum from the Qinhuai River. The results showed that the average concentrations of inorganic P (IP) occurred in the following order: urban sediment (1499.1 mg/kg) > suburban sediment (846.1-911.9 mg/kg) > rural sediment (661.1 mg/kg) > natural sediment (179.9 mg/kg), and makes up to 53.9-87.1% of total P (TP). The same as the pattern of IP, OP nearly increased dramatically with increasing the urbanization gradient. This spatial heterogenicity of P along a river was attributed mainly to land use patterns and environmental factors (relative contribution affecting the P fractions: sediment nutrients > metals > grain size). In addition, the highest values of TP (2876.5 mg/kg), BAP (biologically active P, avg, 675.7 mg/kg), and PPI (P pollution index, ≥ 2.0) were found in urban sediments among four regions, indicating a higher environmental risk of P release, which may increase the risk of eutrophication in overlying water bodies. Collectively, this work improves the understanding of the spatial dynamics of P in the natural-rural-urban river sediment continuum, highlights the need to control P pollution in urban sediments, and provides a scientific basis for the future usage and disposal of P in sediments.

Aging properties and cadmium remediation mechanism of biochar in sediment from phosphorus-rich water.

Cadmium (Cd) is the main heavy metal pollutant in sediments from East China. The biochar-sediment nexus can provide carbon sequestration and pollution control. In this work, an in situ study was conducted to investigate the long-term effects and control mechanism of biochar and the effect of biochar aging on Cd stabilization in overlying water-pore water-sediment. The Cd2+ concentration in the overlying water was positively correlated with total nitrogen (0.960, P < 0.05), total organic carbon (0.983, P < 0.05), and total phosphorus (0.993, P < 0.01) in pore water. Biochar stabilized Cd2+ by increasing the pH and oxidation-reduction potential of the sediment environment and promoting the formation of Cd1.25Ca0.75(P2O7) on the biochar surface in sediment from phosphorus-rich water. These changes were closely related to the Brunauer-Emmett-Teller surface area and average pore size of the biochar. Within 60 days, the biochar in the sediment underwent aging, which was closely related to the preparation temperature of the biochar. The organic composition of biochar prepared at a low temperature (≤ 300 °C) and the surface structure of biochar prepared at a high temperature (≥ 500 °C) were altered. The biochar parameter changes were in the order of pore volume > Brunauer-Emmett-Teller surface area > pore size. Our results show that biochar modification can enhance the remediation capacity of biochar, but may be unfavorable to biochar anti-aging. This knowledge will support policymakers and researchers when exploring long-term biochar use in contamination control and strengthen future research.

Simultaneous immobilization of sediment internal phosphorus, arsenic and tungsten by lanthanum carbonate capping.

In this study, lanthanum carbonate (LC) was selected as a capping agent to examine its effectiveness in immobilizing sediment internal phosphorus (P), arsenic (As) and tungsten (W). With a 180-day incubation experiment, it was determined that LC capping efficiently reduced the concentrations of soluble reactive P (SRP), soluble As and soluble W in pore water, with the highest reduction rate of 83.39%, 56.21% and 68.52%, respectively. The primary mechanisms involved in the adsorption of P, As and W by LC were precipitation reactions and ligand exchange. Additionally, P, As and W were immobilized by LC capping through the transformation of fractions from mobile and less stable forms to more stable forms. Furthermore, LC capping led to an increase in the Eh value, which promoted the oxidation of soluble Fe (Ⅱ) and soluble Mn. The significantly positive correlation and synchronized variations observed between SRP, soluble As, soluble W, and soluble Fe (II) indicated that the effects of LC on Fe redox played a crucial role in immobilizing sediment internal P, As and W. However, the oxidation of Mn, promoted by LC, played a more significant role in immobilizing sediment internal As than P and W. These effects resulted in LC capping achieving the highest reduction of SRP, soluble As and soluble W flux at 145.22, 22.19, and 0.58 µg m-2d-1. It is of note that LC capping did not lead to an elevated release hazard of Co, Ni, Cu, and Pb, barring Cd. Besides, LC capping did not modify the entire microbial communities in the sediment, but altered the proportional representation of specific microorganisms. Generally, LC has potential as a capping agent capable of simultaneously immobilizing sediment internal P, As and W.

Changes in microcystin concentration in Lake Taihu, 13 years (2007-2020) after the 2007 drinking water crisis.

Since the 2007 water crisis occurred in Lake Taihu, substantial measures have been taken to restore the lake. This study evaluates the effectiveness of these restoration activities. We examined the physicochemical parameters and the distribution of microcystin and Microcystis in both the water column and sediment during the bloom period of May 2020 to October 2020. The mean value of extracellular and intracellular microcystin content was 0.12 µg L-1 and 16.26 µg L-1, respectively. The mean value of microcystin in sediment was 172.02 ng g-1 and peaked in August. The concentration in the water and sediment was significantly lower than the historical average concentration. The abundance of toxigenic Microcystis and total Microcystis in the water column ranged from 2.61 × 102 to 2.25 × 109 copies·L-1 and 8.28 × 105 to 2.76 × 109 copies·L-1, respectively. The proportion of toxic Microcystis in the sediment ranging from 31.2% to 19.12%. The highest and lowest region was Meiliang Bay and Grass-algae type zone, respectively. The copy number of the 16S rRNA gene was 1-4 orders of magnitude higher than that of mcyA gene in populations of Microcystis, indicating that non-toxic Microcystis was the dominant form in the majority of the lake. The abundance of toxic Microcystis in the water column was positively correlated with total phosphorus, PO43--P and pH, while the water temperature played distinct role to the distribution of toxic Microcystis in sediment. Our research indicated phosphorus remains a key factor influencing the toxic Microcystis and microcystins in the water column. pH played distinct roles in the distribution of microcystins in sediment and water column. The increasing water temperature is a threat. Explicit management actions and policies, which take into account nutrient concentrations, pH, and increasing temperatures, are necessary to understand and control the distribution of microcystin and Microcystis in Lake Taihu.

Risk surveillance with spatial distribution of Organochlorine Pesticides (OCPs) from sedimentary samples of Chenab River.

A pioneering study employed a holistic geostatistical approach to predict the spatial variability of a non sampled area in the Chenab River, Pakistan, using kriging interpolation for organochlorine pesticide (OCP)-polluted risk zones. The Present research intended to investigate the carcinogenic and non-carcinogenic human health risks, contamination levels, and spatial variation of OCPs in the Chenab River, Pakistan. The residual OCP content in sediment samples (n = 120) ranged from 0.056 to 32.14 ng/g. DDE and α-HCH were prevalent among all the samples analyzed, with mean concentrations of 15.84 ± 8.02 and 12.45 ± 6.72 ng/g, respectively. The order of magnitude of OCPs in sediment samples was DDTs > α-HCH > chlorothalonil > heptachlor > endosulfan > aldrin > dieldrin. The findings of the single (SPI) and Nemerow (Nel) pollution index of α-HCH, heptachlor, and aldrin depicted the Chenab River as a serious pollution risk zone. The outcomes of the Pearson correlation coefficient analysis represent the positive correlation among all OCPs, revealing the common origin. Distribution trends showed substantially higher (p < 0.05) contents of analyzed OCPs along the downstream zone. With regards to USEPA human health hazard assessment model, the estimated non-carcinogenic (ΣHI) and non-carcinogenic (ΣTCR) risk ranged from 1.1 × 10-5 to 1.0 × 10-1, 4.0 × 10-8 to 3.2 × 10-4 respectively. TCR >10-4 illustrated a substantial cancer health risk posed by α-HCH, heptachlor, aldrin, and dieldrin in the downstream zone. We recommend the urgent cessation of the ongoing discharge of OCPs into the Chenab River, which needs to be highlighted owing to the significant cancer risk to public health to ensure the good health and wellbeings.

Influence on the release of arsenic and tungsten from sediment, and effect on other heavy metals and microorganisms by ceria nanoparticle capping.

In this study, ceria nanoparticle (CNP) was used as a capping agent to investigate the efficiency and mechanism of simultaneously controlling the release of sediment internal Arsenic (As) and tungsten (W). The results of incubation experiment demonstrated that CNP capping reduced soluble As and W by 81.80% and 97.97% in overlying water, respectively; soluble As and W by 65.64% and 60.13% in pore water, respectively; and labile As and W in sediment by 45.20% and 53.20%, respectively. The main mechanism of CNP controlling sediment internal As and W was through adsorption via ligand exchange and inner-sphere complexation, as determined through adsorption experiments, XPS and FIRT spectra analysis. Besides, CNP also acted as an oxidant, facilitating the oxidation of AsⅢ to AsV and thereby enhancing the adsorption of soluble As. Additionally, sediment As and W fractions experiments demonstrated that the immobilization of As and W with CNP treatment via transforming mobile to stable fractions was another mechanism inhibiting sediment As and W release. The obtained significant positive correlation between soluble As/W and Fe/Mn, labile As/W and Fe/Mn indicated that iron (Fe) and manganese (Mn) oxidation, influenced by CNP, serve as additional mechanisms. Moreover, Fe redox plays a crucial role in controlling internal As and W, while Mn redox plays a more significant role in controlling As compared to W. Meanwhile, CNP capping effectively prevented the release of As and W by reducing the activity of microorganisms that degrade Fe-bound As and W and reduced the release risk of V, Cr, Co, Ni, and Zn from sediments. Overall, this study proved that CNP was a suitable capping agent for simultaneously controlling the release of As and W from sediment.

Experimental research on the effect of water velocity on phosphorus release from sediments of a plateau cold water type river.

The release of phosphorus from sediment is an important source of endogenous phosphorus in water bodies and is an important factor affecting the total phosphorus content in river system. Water velocity is key factor affecting the rate of phosphorus release from sediments. In this paper, the effects of water velocity on the release of phosphorus from sediments in a plateau cold water type river were investigated. The ecological environment of plateau cold water rivers is sensitive and fragile. The changes in environmental conditions can easily lead to changes in the overall water quality of rivers. Therefore, exploring the release process of phosphorus in plateau cold water rivers under changes in hydrodynamic conditions is important for protecting the ecological environment of plateau rivers. The results showed that the release of total phosphorus from sediments followed a first-order kinetic process, when the flow velocity was lower than the threshold velocity of sediments. The total phosphorus release coefficient of sediment linearly increased with increases in water flow velocity. The total phosphorus release coefficient of sediment was related to the flow velocity by kTP20=3.03v/vc+0.08v

Benthic primary production decreases internal phosphorus loading from lake sediments under light supplement.

In aquatic ecosystems, light penetrating the sediment surface in shallow lakes may regulate the internal phosphorus (P) release through benthic primary production, which subsequently affects oxidation, pH levels, and alkaline phosphatase activity in the upper sediment. To study the effects of light exposure on the P dynamics at the sediment-water interface under eutrophic conditions, a two-month mesocosm experiment was conducted in twelve cement tanks (1000 L each). The tanks were equipped with Light-Emitting Diode (LED) lights, and surface sediments collected from eutrophic Lake Nanhu (China) were exposed to four different light intensities (0, 50, 100, 200 µmol m-2 s-1). The results revealed that: 1) Both the total phosphorus concentration and the phosphorus release flux from the sediment were lower in the light treatments (mean value, 0.59-0.71 mg L-1 and 0.00-0.01 mg m-2 d-1, respectively) than in the control treatment (0.77 mg L-1 and 0.01 mg m-2 d-1, respectively), indicating that light supplement could decrease the internal P release. 2) Benthic primary production promoted by light directly absorbed soluble reactive phosphorus and decreased the internal P release. The resulting improved production could also increase dissolved oxygen concentrations at the sediment-water interface, thus indirectly inhibiting internal P release. 3) The relative contributions of direct absorption and indirect inhibition on the internal P release ranged between 23% to 69% and 31% to 77% depending on the light intensity.