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In this study, Z-type ZnIn 2 S 4 @CuO composites with a core–shell structure were synthesized. Under visible light irradiation, ZnIn 2 S 4 @CuO generates electron-hole pairs, and the presence of an internal electric field (IEF) improves the charge transfer mechanism of the composites and promotes the separation of charge carriers. The electrons on the conduction band of ZnIn 2 S 4 combine with dissolved oxygen in water to generate •O 2 –, and the holes on the valence band of CuO combine with OH– and H 2 O in water to generate •OH, and the generated reactive substances attack atoms on the TC to cause its ring-opening degradation, and ultimately mineralize the TC into CO 2 and H 2 O. [Display omitted] • A novel method for efficient construction of binary composites is proposed. • Z-type heterostructure reduces the photogenerated carrier complexation efficiency. • Verification of the Z-structure charge transfer mechanism. • TC degradation pathways proposed in combination with HR-MC and FEDs. In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core–shell structure ZnIn 2 S 4 @CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn 2 S 4 @CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn 2 S 4 alone, respectively, the reason is because of the introduction of ZnIn 2 S 4 , Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn 2 S 4 @CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis of how the nanopore size of membranes and how the surface charge of nanobubbles responds to its pinch-off from the nanopore. This study also tested the hypothesis that nanobubbles that remain in solution after production may increase the dissolved oxygen content in water. The effect of membrane pore size, hydrodynamic conditions (gas and liquid flow rates), and physicochemical parameters (pH and temperature) on volumetric mass transfer coefficient (k L a) for oxygen nanobubbles formed by the nanopore diffusion technique was investigated. This study experimentally determined the k L a by carefully removing the dissolved oxygen by nitrogen purging from nanobubble suspension to examine the sole contribution of nanobubble dissolution in water to the reaeration. Scaling estimates indicate that the nanobubble pinch-off radius and nanopore radius have a power-law correlation and that nanobubble size declines with the nanopore size. This is in line with our experimental results. The surface charge of nanobubbles delays its pinch-off at the gas-liquid interface. Nanobubbles offered 3-4 times higher k L a than microbubbles. Standard oxygen transfer efficiency in water was found to be 78%, significantly higher than that in microbubbles. However, dissolving stable nanobubbles in water does not considerably increase dissolved oxygen levels. [ABSTRACT FROM AUTHOR]

A 24-h hypoxia exposure experiment was conducted to determine how hypoxia exposure induce liver angiogenesis in largemouth bass. Nitrogen (N 2) was pumped into water to exclude dissolved oxygen into 1.2 ± 0.2 mg/L, and liver tissues were sampled during hypoxia exposure of 0 h, 4 h, 8 h, 12 h, 24 h and re-oxygenation for 12 h. Firstly, the results showed that hypoxia exposure promoted the angiogenesis occurrence by immunohistochemical analysis of vascular endothelial growth factor receptor 2 (VEGFR2). Secondly, the concentration of vasodilation factor increased and it's activity was elevated during 8 h exposure, such as nitric oxide (NO) and nitric oxide synthase (NOS) (p < 0.05). Thirdly, hypoxia exposure promoted angiogenesis through up-regulation the expression of matrix metalloproteinase 2 (MMP-2), jagged, protein kinase B (AKT), phosphoinositide-3-kinase (PI3K), mitogen-activated protein kinase (MAPK) at 4 h; contrarily, the expression of inhibiting angiogenesis genes presented up-regulated at 8 h (p < 0.05), such as matrix metalloproteinase inhibitor-2 (TIMP-2), matrix metalloproteinase inhibitor-3 (TIMP-3). Finally, the genes and proteins that regulate angiogenesis presented obvious chronological order. Parts of them promoted the budding and extension of blood vessels were up-regulated during 4 h–8 h (p < 0.05), such as vascular endothelial growth factor a (VEGFA), VEGFR2, monocarboxylic acid transporter 1 (MCT1), CD147, prolyl hydroxylase (PHD), nuclear factor kappa-B (NF-κB); other part of them promoted blood vessel maturation were highly expressed during 12 h–24 h (p < 0.05), such as angiogenin-1 (Ang-1) and angiogenin-2 (Ang-2). In short, acute hypoxia can promote the liver angiogenesis of largemouth bass by HIF - dependent pathway. • Hypoxia promote the liver angiogenesis in largemouth bass. • Hypoxia modulate VEGF pathway and downstream genes. • MCT1 and HIF pathway are key factors regulating angiogenesis during hypoxia exposure. [ABSTRACT FROM AUTHOR]

Water temperature and dissolved oxygen are two important parameters which affect the ecosystem functions which estuaries provide. As such, we need to understand the long-term change of these parameters in English estuaries to better understand those areas which may be vulnerable in the present and future. Detecting these trends in monitoring data is difficult however, since temporally and spatially heterogeneous sampling has the potential to obscure any long-term component of change. In this study, we use a generalized additive model (GAM) approach to isolate the inter-annual change of water temperature and dissolved oxygen in spot sampled monitoring data across English estuaries. This technique can account for the potentially non-linear variability caused by temporal and spatial variations in sampling throughout the day and year. We find that water temperature in all modelled estuaries has warmed, with an average warming of 0.037 °C/yr between 1990 and 2022, in line with temperature change in rivers and the sea surface around England. For the same period, dissolved oxygen has increased for roughly half of modelled estuaries and decreased for the other half. The variation across English estuaries in these two conditions is best explained by the geographical location of an estuary. Many of the estuaries warming at the greatest rate are those where sea surface temperature increase has also been greatest. We suggest the observed distribution of changes in dissolved oxygen can be explained by three processes: (1) temperature driven change, (2) dissolved oxygen improvement (e.g., reduced nutrient inputs through wastewater management regulation) and (3) changes in the number of primary productivity-induced super saturation events. This study provides a comprehensive look at temperature and dissolved oxygen change across English estuaries over the past ∼30 years, which may provide information on the processes behind how these water quality parameters have changed and will continue to do so. • Temperature and dissolved oxygen change in English estuaries is determined. • Generalized additive models are used to remove seasonal and diurnal variations. • Extra value can be gained from monitoring data by using appropriate analysis. • All estuaries in England have warmed, at an average rate of 0.037 °C/yr. • Dissolved oxygen trends vary based on temperature, regulation or productivity. [ABSTRACT FROM AUTHOR]

[Display omitted] Herein, a novel metal-free catalyst consisting of multiporous oxygen-rich carbon–nitrogen graphene-like nanosheets (O LAA -CN NSs) is first developed through a staged temperature-programmed calcination of l -ascorbic acid (LAA)-modified dicyandiamide precursor. It is found that the oxygen species from l -ascorbic acid (O LAA) are introduced into the graphene-like basic matrix and replace partial N atoms to form the C O C-R structure, leading to the non-uniform distribution of electrons on the catalyst surface, and the formation of electron-rich centers around the C O C microareas according to a series of characterization techniques. As a result, O LAA -CN NSs exhibits excellent performance for refractory pollutant removal in the presence of peroxymonosulfate (PMS) and dissolved oxygen. Some pollutants with complex structures are even completely degraded within only 1 min. The interface reaction mechanism is further revealed that PMS mainly acts as an active inducer to drive the electron donation of pollutants over O LAA -CN NSs. These electrons are finally utilized by dissolved oxygen to generate reactive oxygen species (ROS) through the interface process. This reaction system results in pollutants that can either be cleaved directly by surface oxidation process or degraded by the attack of the generated ROS, such as singlet oxygen (1O 2) and superoxide radicals (O 2 •−), through oxygen activation, which significantly reduces the resource and energy consumption in advanced wastewater treatment by harnessing the energy of pollutants and dissolved oxygen in the water. [ABSTRACT FROM AUTHOR]

Normal dissolved oxygen in water is essential for maintaining the physiological functions of fish, but environmental pollution, such as eutrophication can lead to a decrease in oxygen content in water. How this reduction of dissolved oxygen in water affects the immune functions of fish and the potential regulatory mechanisms have not been thoroughly elucidated. In this study, we made full use of the aquatic model animal zebrafish to explore this question. In a model of LPS-induced inflammation, we found that hypoxia induced by infusing nitrogen into water increased the expression of pro-inflammatory cytokines, such as il-1β , il-6 , and il-8. In vivo imaging also showed that hypoxia significantly increased neutrophil migration to the site of caudal fin injury in the transgenic line. Subsequently, we found that the phosphorylation level of ERK protein was significantly activated upon hypoxia and proved the roles of ERK signaling in the expression of pro-inflammatory cytokines and neutrophil migration in zebrafish. This study indicated that reduced water oxygen significantly increases the inflammatory response of the zebrafish. [Display omitted] • Hypoxia increases the expression of pro-inflammatory cytokines. • Hypoxia increases neutrophil aggregation towards the injury site. • ERK mediates the regulation of inflammation by hypoxia. [ABSTRACT FROM AUTHOR]

Eutrophication is a serious threat to water quality and human health, and chlorophyll- a (Chla) is a key indicator to represent eutrophication in rivers or lakes. Understanding the spatial-temporal distribution of Chla and its accurate prediction are significant for water system management. In this study, spatial-temporal analysis and correlation analysis were applied to reveal Chla concentration pattern in the Fuchun River, China. Then four exogenous variables (wind speed, water temperature, dissolved oxygen and turbidity) were used for predicting Chla concentrations by six models (3 traditional machine learning models and 3 deep learning models) and compare the performance in a river with different hydrology characteristics. Statistical analysis shown that the Chla concentration in the reservoir river segment was higher than in the natural river segment during August and September, while the dominant algae gradually changed from Cyanophyta to Cryptophyta. Moreover, air temperature, water temperature and dissolved oxygen had high correlations with Chla concentrations among environment factors. The results of the prediction models demonstrate that extreme gradient boosting (XGBoost) and long short-term memory neural network (LSTM) were the best performance model in the reservoir river segment (NSE = 0.93; RMSE = 4.67) and natural river segment (NSE = 0.94; RMSE = 1.84), respectively. This study provides a reference for further understanding eutrophication and early warning of algal blooms in different type of rivers. [Display omitted] • Chlorophyll-a in the reservoir river segment (RRS) were higher than the natural river segment (NRS) in August and September. • Temperature and DO were higher correlated with Chlorophyll- a , and the relationship was stronger in RRS than in NRS. • The successful application of machine learning algorithms enabled highly accurate predictions for water blooms. • XGBoost and LSTM were the best performance model in RRS and NRS, respectively. [ABSTRACT FROM AUTHOR]

Cyanobacterial bloom is a pressing issue affecting water supply security and ecosystem health. Phosphorus (P) released from cyanobacterial bloom during recession is one of the most important components involved in the lake P cycle. However, little is known about the consequences and mechanisms of the P cycle in overlying water and sediment due to the anthropogenic treatments of cyanobacterial blooms. In this study, treatment methods using hydrogen peroxide (H 2 O 2), polyaluminum chloride (PAC), and the feces of silver carp were investigated for their influence on the P cycle using microcosm experiments. Results showed that H 2 O 2 treatment significantly increased the internal cycle of sediment-related P, while PAC treatment showed minor effects. H 2 O 2 and PAC treatment suppressed the release of P from sediment before day 10 but promoted the release of P on day 20, while silver carp treatment suppressed the release of P during the whole experiment. The reductive dissolution of iron oxide-hydroxide was the major factor affects the desorption of P. Path analyses further suggested that overlying water properties such as dissolved oxygen (DO) and oxidation-reduction potential (ORP) play critical roles in the treatment-induced sediment P release. Our results quantify the endogenous P diffusion fluxes across the sediment-water interface attributed to cyanobacterial treatments and provide useful guidance for the selection of controlling methods, with silver carp being the most recommended of the three methods studied. [Display omitted] • H 2 O 2 , PAC, and silver carp treatments on P cycle in lake systems were studied. • H 2 O 2 and PAC inhibited P release initially but enhance P release at the end. • Filter-feeding and excretion of algae by silver carp reduced P release. • P release was related to reduction of NaOH–P and changes in DO and ORP. [ABSTRACT FROM AUTHOR]

Sand media filters are a key component of micro-irrigation systems since they help preventing emitter clogging, which greatly affects the system performance. Dissolved oxygen is an irrigation water quality parameter related to organic matter loading. Low values of dissolved oxygen can cause crop root hypoxia and, therefore, agronomic problems. Thus, an accurate prediction of dissolved oxygen values could be of great interest, especially if effluents are used in micro-irrigation systems. The aim of this study was to obtain a predictive model able to forecast the dissolved oxygen values at the outlets of sand media filters. In this study, a Gaussian process regression (GPR) model was used for predicting the output dissolved oxygen (DO o) from data corresponding to 547 filtration cycles of different sand filters using reclaimed effluent. This optimisation technique involves kernel parameter setting in the GPR training procedure, which significantly influences the regression accuracy. To this end, the height of the filter bed, filtration velocity and filter inlet values of the electrical conductivity, dissolved oxygen, pH, turbidity and water temperature were monitored and analysed. The significance of each variable on filtration performance is presented and a model for forecasting the outlet dissolved oxygen obtained. Regression with optimal hyperparameters was performed and a coefficient of determination of 0.90 for DO o was obtained when this new predictive GPR–based model was applied to the experimental dataset. Agreement between experimental data and the model confirmed the good performance of the latter. • Dissolved oxygen in sand filter outlets indicates organic matter load in irrigation. • Predictive model using Gaussian process regression and differential evolution. • Model predicted satisfactorily the sand filter outlet dissolved oxygen. • Correlation coefficient from this hybrid GPR–based model was 0.95. [ABSTRACT FROM AUTHOR]

Amongst a spectrum of benefits, Nature-based Solutions (NBS) are increasingly being advocated as improving the quality of aquatic environments in urban areas. Of these, a widely adopted measure is tree planting. Yet, because of the local complexities and spatial variability of urban hydrological response, it is difficult to predict to what extent improvements in water quality will arise. To overcome this barrier, a standardised approach to process-based model simulation of urban river quality is described (QUESTOR-YARDSTICK (QUESTOR-YS)). The approach eliminates the influence of point sources of pollution and harmonises the way in which river hydrodynamics and contributory catchment size are represented. Thereby, it focuses on differences in water quality between cities due solely to climate, river discharge and urban diffuse nutrient pollution factors. The relative sensitivity to NBS establishment between urban water bodies in different cities anywhere across the world can also potentially be quantified. The method can be readily extended to include wastewater effluents. The validity of the approach is demonstrated for a small river in Birmingham, UK; and thence demonstrated for the case of 10 km of riparian tree planting in Birmingham, Oslo (Norway) and Aarhus (Denmark). Modelling suggests that riparian tree planting can substantially improve water quality in each example city for three key indicators of water quality in sensitive summer conditions (water temperature, chlorophyll-a and dissolved oxygen). Results show the level of benefit achievable in response to a fixed amount of planting will depend on the existing level of riparian tree occupancy. • A standard approach to modelling river water quality in urban areas is presented. • Global between-city comparison of potential effectiveness of NBS is made possible. • Examples for riparian tree planting are shown for three European cities. [ABSTRACT FROM AUTHOR]

This study highlights a green approach for the reduction of graphene oxide (GO) using the ultraviolet/sulfite advanced reduction process (UV/sulfite process). X-ray photoelectron spectroscopy (XPS) provided a strong evidence on the efficient reduction of GO by increasing the C/O ratio from 2.0 to 4.8, and the successful reduction was also characterized by UV–Vis, XRD and Raman spectrometry. The reduction of GO was attributed to the hydrated electrons generated from both sulfite photolysis (major, contributed by 71.4%) and GO photolysis (minor, contributed by 21.6%) under UV irradiation. The dissolved oxygen in water exhibited inhibitory effect on GO reduction through scavenging of the hydrated electrons. Moreover, the reduction efficiency of GO decreased with the increasing UV wavelength from 254 nm to 365 nm, because of the reduced molar absorptivity of sulfite at higher UV wavelength. By using this green photo-reduction method, high-purity of reduced graphene oxide can be easily obtained by water-rinse, since soluble sulfite are the only by-products. In conclusion, the research outcomes provide mechanistic insights on the GO reduction by the hydrated electron-based advanced reduction processes, which has great potential for the environmental-friendly and cost-effective reduction of GO. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we investigate the large time behavior of strong solutions to a chemotaxis-fluids system in an unbounded domain with mixed boundary conditions. Based on the anisotropic L p technique, the elliptic estimates and Stokes estimates, we first establish the global existence of strong solution around the equilibrium state (0 , c satn , 0) with the help of the continuity arguments, where c satn is the saturation value of oxygen inside the fluid. Then we use De Giorgi's technique and energy method to show that such a solution will converge to (0 , c satn , 0) with an explicit convergence rate in the chemotaxis-free case. Our assumptions and results are consistent with the experimental descriptions and the numerical analysis. The novelty here consists of deriving some new elliptic estimates and Stokes estimates, and choosing a suitable weight in De Giorgi's technique to deal with the mixed boundary conditions. [ABSTRACT FROM AUTHOR]

Diffuse alveolar hemorrhage (DAH) is a life-threatening complication of systemic lupus erythematosus (SLE) and systemic vasculitis. Although initially described to have antibacterial properties, increasing evidence suggests that neutrophil extracellular traps (NETs) have a detrimental role in both autoimmune diseases and acute lung injury. We investigated whether NETs could be detected in a murine model of pristane-induced lupus DAH and contribute to lung injury. Such NETs might constitute a therapeutic target. NETs were characterized by immunofluorescence staining of DNA, neutrophil elastase and citrullinated histones. Evaluation of lung injury was performed by haematoxylin-eosin staining and a quantification program. Clinical status of the mice was assessed by measurement of arterial oxygen saturation and survival curves after recombinant human deoxyribonuclease-1 (Rh-DNase-1) inhalations or polymorphonuclear neutrophil (PMN) depletion. Pristane was found to promote NETs formation in vitro and in vivo. Treatment of mice with Rh-DNase-1 inhalations cleared NETs and reduced lung injury. Clinical status improved significantly, with increased arterial oxygenation and survival. Following PMN depletion, NETs were absent with a subsequent reduction of lung injury and improved arterial oxygenation. These results support a pathogenic role of PMNs and NETs in lung injury during pristane-induced DAH. Targeting NETs with Rh-DNase-1 inhalations could constitute an interesting adjuvant therapy in human DAH. • Pristane-induced diffuse alveolar hemorrhage (DAH) lupus model can be considered as a pulmonary model of NETosis. • Targeting NETs with recombinant human deoxyribonuclease reduced severity of DAH lesions and improves animal clinical status. • Recombinant human deoxyribonuclease could be an interesting adjuvant therapy in human DAH. [ABSTRACT FROM AUTHOR]

Abstract Barrier island lagoons are the most common type of estuary in the world and can be prone to eutrophication as well as the formation and closure of ocean inlets via severe storm activity. This study describes the biological, chemical, and physical changes that occurred along the south shore of Long Island, NY, USA, following the formation of a new ocean inlet in eastern Great South Bay (GSB) by Hurricane Sandy in October of 2012. Time series sampling and experiments were performed at multiple locations within GSB and neighboring Moriches Bay from 2013 through to 2018. Historical comparisons to prior water quality monitoring data, fecal coliform concentrations, and hard clam growth rates were also made. Measurements indicated that the New Inlet provided asymmetrical ocean flushing. Within locations north (Bellport Bay) and east (Narrow Bay, western Moriches Bay) of the New Inlet, water residence times, summer water temperatures, total and dissolved nitrogen, chlorophyll a , the harmful brown tide alga, Aureococcus anophagefferens , pigments associated with diatoms and dinoflagellates (fucoxanthin and peridinin), and fecal coliform bacteria levels all significantly decreased, while salinity, dissolved oxygen, and water clarity significantly increased. In contrast, waters west of the New Inlet within the center of GSB experienced little change in residence times, significant increases in chlorophyll a and harmful brown tides caused by A. anophagefferens , as well as a significant decrease in water clarity and summer dissolved oxygen levels. Growth rates of juvenile hard clams (Mercenaria mercenaria) near the New Inlet increased compared to before the inlet and were significantly higher than in central GSB, where growth rates significantly declined compared to before the inlet. Hence, while enhanced ocean flushing provided a series of key ecosystem benefits for regions near the New Inlet, regions further away (> 10 km) experienced more frequent HABs and poorer performance of bivalves, demonstrating that enhanced ocean flushing provided by the breach was not adequate to fully restore the whole GSB ecosystem. Graphical abstract Image 1 Highlights • In 2012, Hurricane Sandy breached Fire Island and formed the "New Inlet". • The New Inlet has decreased residence time within Great South Bay. • Increased flushing has significantly improved water quality near the New Inlet. • Despite the creation of the New Inlet, central Great South Bay was mostly unaffected. • The New Inlet may improve the growth and performance of bivalves. [ABSTRACT FROM AUTHOR]

Abstract Dissolved oxygen (DO) plays a major role in sustaining aquatic communities; its concentration and regulatory determinants are considered a key node predicting eutrophy, ecosystem health, and biogeochemical feedbacks. Here we report the status of dissolved oxygen deficit (DOD; hypoxia), and its mechanistic links with sediment oxygen demand (SOD) in the Ganga River. We conducted two independent but interlinked studies during summer low flows of three consecutive years (2016–2018) considering: 1) a 518 km middle segment of the Ganga River between Kanpur upstream and Varanasi downstream; and 2) trajectory analyses downstream two point sources, one flushing industrial effluents (Wazidpur drain) and the other with urban sewage (Assi drain). The concentration of DO at sediment-water interface (DO sw) did appear < 2.0 mg L−1 (hypoxia) at Jjmu; and up to 600 m and 800 m downstream Assi and Wazidpur drain respectively. The DOD at sediment-water interface (DOD sw) was highest at Jjmu and did not show a significant decrease up to 300 m downstream to point sources. The SOD which varied between 2.03 and 13.16 (main river stem); 4.39 and 16.81 (Wazidpur drain); and between 2.00 and 13.50 g O 2 m−2 d−1 (Assi drain), was found to be a major contributor of DOD. Principal component analysis (PCA) and non-metric multi-dimensional scaling (NMDS) separated DO and alkaline phosphatase (AP) opposite to oxygen-consuming processes and sediment-P release. Using a dynamic fit model, we tested the dependence of sediment-P release on DO sw and DOD sw. A large increase in the sediment-P release with increasing DOD sw and decreasing DO sw indicated that the system may compromise its resilience in long-term future in terms of self-fertilization and P-eutrophy if the similar magnitude of anthropogenic pressure is continued. The study advances our understanding towards DOD associated habitat fragmentation, ecosystem resilience and niche opportunities useful for recovery and management of the Ganga River. Highlights • Human-driven increases in SOD create mosaic of low oxygen zones in the Ganga River. • The COD seemed to be an important contributor to SOD. • There was a large increase in sediment-P release at DOD sw > 5.48 mg L−1. • The SOD-DOD-AP linkages emerged as a level determinant for assessing river ecosystem health. • If the drops in DO sw continue, the river may compromises its resilience. [ABSTRACT FROM AUTHOR]

Abstract Hypoxic water masses are usually formed in the bottom layer of stratified water columns. However, we found that hypoxia was formed throughout the water column in a well-mixed macrotidal estuary, the Rokkaku River Estuary, Japan. There was a spring-neap variation in the dissolved oxygen (DO) concentration where hypoxia developed during spring tides. Minimum DO concentration was observed 1 or a few days after the spring tide. When hypoxia developed, all the water column from bottom to surface became hypoxic (<2 mg l−1 or < 30% saturation). The hypoxic water mass was associated with the estuarine turbidity maximum (ETM). Oxygen demand of water in this area was very large (>2 mg l−1 day−1). Potential oxygen consumption by microorganisms was positively correlated with turbidity. Concentration of suspended solid (SS) at the ETM exceeded 1000 mg l−1. Furthermore, particulate organic carbon (POC) concentration in the estuary increased in spring tides. C/N ratio and δ13C of organic matter suggested that POC was transported from the sea into the estuary. These results suggest that the active resuspension of organic matter caused by the strong tidal current during spring tides enhanced the respiratory activity of microorganisms and the main source of the organic matter was detrital material from the sea. Such a large amount of organic matter should fuel microbial respiration effectively. Since microbial oxygen consumption was larger than the oxygen supply from the water surface even in the well mixed condition, a hypoxic water mass was formed in this estuary. [ABSTRACT FROM AUTHOR]

Abstract Measuring iron content has practical clinical indications in the study of diseases such as Parkinson's disease, Huntington's disease, ferritinopathies and multiple sclerosis as well as in the quantification of iron content in microbleeds and oxygen saturation in veins. In this work, we review the basic concepts behind imaging iron using T2, T2*, T2′, phase and quantitative susceptibility mapping in the human brain, liver and heart, followed by the applications of in vivo iron quantification in neurodegenerative diseases, iron tagged cells and ultra-small superparamagnetic iron oxide (USPIO) nanoparticles. Highlights • Basic concepts behind iron quantification using T2, T2*, T2′, phase and QSM are introduced. • Iron quantification applications in the brain, liver, heart and iron tagged cells are reviewed. • Recent studies investigating the correlation of R2* and QSM with iron are discussed. • Results of recent iron quantification studies in the brain using R2* and QSM on Parkinson's disease are summarized. [ABSTRACT FROM AUTHOR]

Abstract Desert springs are critical for wildlife and human subsistence, but poorly studied. The springs in the northern Chihuahuan Desert region of Mexico are no exception. While groundwater overexploitation and other anthropogenic activities have endangered these waters, little is known about their water quality or biodiversity. We monitored five springs on a monthly basis for one year, and two others sporadically, to determine their physicochemical characteristics and to study rotifer community composition as an assessment of biodiversity. Seasonal variation in temperature, dissolved oxygen (DO), and conductivity was observed in the five springs. DO was occasionally below the criterion for aquatic life (<4 mg/L) in some springs. Ca2+ (468–775.2 mg/L) was the dominant ion in all springs except Ojo de Santa María where Na+ (180–290 mg/L) dominated. Of 57 rotifer species identified, Lepadella patella (Müller, 1786), Lepadella triptera (Ehrenberg, 1830), and Philodina megalotrocha , Ehrenberg, 1832 were present in most springs. The rotifer community exhibited nestedness among the sites (supported by four null modes, p < 0.05) and was correlated with fall season, DO, and nitrate concentration. This work provides information that will aid in management practices and provide important baseline data on water quality and regional diversity of a major component of the zooplankton. Highlights • Physicochemical features and rotifer diversity were determined for 7 springs. • Temperature, conductivity and oxygen level varied seasonally among springs. • Sixty species of rotifers showed nestedness among the sites. • Species richness was correlated to dissolved oxygen, nitrate, and fall season. • Ten rotifer species were added to those reported in Chihuahuan Desert springs. [ABSTRACT FROM AUTHOR]

Dissolved oxygen concentration and pH are controllable and cost-effective variables that determine the success of microalgae-related processes. The present study compares different control strategies for pH and dissolved oxygen in pilot-scale microalgae production systems. Two 80 m2 raceway reactors were used, one operated with freshwater plus fertilizer and the other with wastewater as the nutrient source. Both were in semi-continuous mode at a fixed dilution rate of 0.2 day−1. A comparison between the classical On-Off and more advanced pH control strategies, such as PI and Event-based control, was performed, focusing on biomass productivity and the influence of all the process parameters on microalgae growth; "No control" of pH was also assayed. The results show that Event-based control was the best algorithm when using freshwater plus fertilizer. In contrast, no significant differences were observed using the different control strategies when wastewater was the nutrient source. These experiments were performed through selective control strategy, prioritizing pH over dissolved oxygen; however, it was demonstrated that they did not allow to achieve satisfactory dissolved oxygen removal results, especially for the fertilizer system. After modifying the gas diffuser configuration and improving the mass transfer, independent on-off strategies have been developed, permitting effective control of both variables and increasing productivity by up to 20% in both systems. Concluding, a detailed analysis of the energy demand for each strategy implemented in terms of gas consumption and gas flow to biomass ratio is provided. • Optimal pH and dissolved oxygen control strategies for pilot-scale raceway reactors • Improved gas-liquid mass transfer in raceway reactors • Comparing control strategies for microalgal cultivations in wastewater and freshwater • Analysis of energy demand for pH and dissolved oxygen control in microalgal cultivations [ABSTRACT FROM AUTHOR]

The spatial and temporal distributions of trace metals in dissolved forms mainly result from anthropogenic and lithogenic contributions. Surface water samples (∼0.5 m) were collected monthly at respective stations from Setiu Wetland. In this study, the behaviour of trace metals in the dissolved phases along the water column from sampling sites in the Setiu Wetland, Malaysia was investigated. In addition, dissolved organic carbon (DOC) and physical parameters such as salinity, temperature, pH and dissolved oxygen (DO) of the surface water were measured in order to evaluate the relationship between trace metals fractionation with different water quality parameters. Size fractionation study of dissolved trace metals using ultrafiltration technique were also carried out and analysed using inductively coupled plasma mass spectrometry (ICP-MS). Correlation of trace metals with other measured parameters was made to furthermore understand the dynamics of trace metals and its fractionated components in this area. The concentration of dissolved trace metals was in the range of 0.001–0.16 μg/L for Cd, 0.12–2.81 μg/L for Cu, 0.01–1.84 μg/L for Pb, 3–17 μg/L for Fe and 1–34 μg/L for Zn, suggesting the input of anthropogenic sources for trace metals such as municipal, industrial, agricultural and domestic discharge. The periodic monitoring and evaluation of trace metals in wetlands and protected tropical areas is highly recommended. • Composition and fate of trace metals in the wetlands were compared. • Distribution and concentration of trace metals were evaluated ‏. • Origin and sources of trace metals was identified. • Fractionation study of trace metals was evaluated. [ABSTRACT FROM AUTHOR]

China is conducting ecological restoration work in urban water bodies. Under anoxic and anaerobic conditions, pollutants transform and produce odorous and black substances, deteriorating the water quality, which is a significant problem in urban water bodies. Vallisneria natans has received widespread attention for its applications in water treatment and restoration. However, the efficiency by which V. natans reduces water pollution and allows sediment remediation requires further improvement. Therefore, in this study, we investigated the effect of V. natans coupled with carbon fiber on the restoration of water bodies and sediment compared with the control group that grew V. natans without carbon fiber. The oxidation-reduction potential (ORP) was selected as the main evaluation index for the water and sediment. Dissolved oxygen in the water and total organic carbon and total nitrogen (TN) in the sediment were also evaluated. V. natans coupled with carbon fiber significantly increased the ORP; that of surface sediment increased by 50 % and that of the water body increased by 60 % compared with the sediment without any bioremediation. Chemical oxygen demand, total phosphorous, and TN in water decreased by 61.2 %, 22.9 %, and 48.3 %, respectively. These results indicate that planting V. natans with carbon fiber can reduce pollutants in water (including humus) and sediments, effectively improving ORP in water and sediment. [Display omitted] ● We examined the sediment remediation effects of V. natans and carbon fibers. ● When coupled with carbon fibers, V. natans increased the oxygen-reduction potential. ● Biodiversity increased in the samples with carbon fibers versus those without. ● The reactor was operated in long time operation (over 250 days) to verify the system performance. [ABSTRACT FROM AUTHOR]

Municipal sledge water is a combination of residential wastewater, industrial effluent, and precipitation water. The water quality parameters analyses results demonstrated that most of the parameters (pH: 5.6 ± 0.3, Turbidity: 102.31 ± 2.8 mg L−1, TH: 946.38 ± 3.7 mg L−1, BOD: 295.63 ± 5.4 mg L−1, COD: 482.41 ± 4.9 mg L−1, Ca: 278.74 ± 1.8 mg L−1, SO 4 2−: 559.64 ± 11.4 mg L−1, Cd: 18.56 ± 1.37 mg L−1, Cr: 31.25 ± 1.49 mg L−1, Pb: 21.45 ± 1.12 mg L−1, and Zn: 48.65 ± 1.56 mg L−1) were considerably increased in quantities with slightly acidic in condition. The in-vitro phycoremediation study was carried out for two weeks with pre-identified Scenedesmus sp. Biomass in different groups of treatments (A, B, C, and D). Interestingly, most of the physicochemical parameters were significantly reduced in group C (4 × 103 cells mL−1) treated municipal sludge water in a shorter treatment period than in the other treatment groups. The phycoremediation percentage of group C were found as pH: 32.85%, EC: 52.81%, TDS: 31.32%, TH: 25.58%, BOD: 34.02%, COD: 26.47%, Ni: 58.94%, Ca: 44.75%, K: 42.74%, Mg: 39.52%, Na: 36.55%, Fe: 68%, Cl: 37.03%, SO 4 2−: 16.77%, PO 4 3−: 43.15%, F: 55.55%, Cd:44.88%, Cr:37.21%, Pb:43.8%, and Zn:33.17%. These findings suggest that increased biomass from Scenedesmus sp. can be used to significantly remediate municipal sludge water and that the obtained biomass and treated sludge can be used as feedstock's for bio fuel as well as bio fertilizer, respectively. • Municipal sledge water contain extensive quantity of most of the parameters. • The dissolved oxygen level of municipal sledge water is considerably very low. • The increased biomass of Scenedesmus sp. Showed fine phtoremediation potential. • Phycoremediation treatment group C showed considerable pollutants removal. • 2 weeks of phycoremediation effectively reduced the pollutants from sledge water. [ABSTRACT FROM AUTHOR]

Abstract Direct human interference has been shaping todays estuaries for centuries, and depletion of dissolved oxygen (DO) frequently occurs in such anthropogenically impacted estuaries. Whereas the role of nutrient input as a major human impact driving DO depletion is clear, the effect of bathymetric modifications as another human impact is less well-known. Here, we aim at a better understanding of how DO dynamics are influenced by bathymetric modifications and changed nutrient input. Therefore, we introduce a coupled hydrodynamic-biogeochemical model (Untrim-Delwaq) and develop an idealized one-dimensional set-up of a vertically well-mixed, funnel-shaped estuary with strong human impact. The set-up dimensions are inspired by the Elbe Estuary (Germany) and model results show good agreement in comparison to observational hydrodynamic and water quality data. In particular, the model reproduces the dynamics of the summer oxygen minimum which regularly develops in the estuarine freshwater part. Analysis of our model runs shows that the estuarine biogeochemistry is dominated by heterotrophic degradation processes rather than primary production because of severe light limitation. A scenario analysis indicates that a reduction in input load scales down all biogeochemical processes. In contrast, a bathymetric change affects the estuarine system and its DO in a more complex way. In particular, the interplay between surface-to-volume ratio and the degradability state of the organic material is the most important factor which determines the capacity to recover high DO mineralization losses by atmospheric input. Thus, our study demonstrates the relevance of bathymetric factors during the assessment of human interference on DO dynamics and biogeochemical processes in estuaries. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

In shrimp aquaculture, overcrowded farming causes fluctuations in dissolved oxygen concentrations. Low-oxygen conditions (hypoxia) affect shrimp growth. Hypoxia-inducible factor (HIF) is a transcriptional factor in the basic helix-loop-helix/PAS family and is activated in response to hypoxic stress. However, little is known about HIF and other inhibitors of the HIF pathway in crustaceans. In this study, we cloned MjHIF-1α , an inhibitory factor, MjFIH-1 (factor inhibiting HIF-1α), and MjVHL (Von Hippel-Lindau tumor suppressor) from kuruma shrimp ( Marsupenaeus japonicus ). MjVHL is the first crustacean VHL ortholog to be cloned. MjHIF-1α , MjFIH-1 , and MjVHL exhibit significant sequence similarity and share key functional domains with previously described vertebrate and invertebrate genes. As a result of gene expression analysis in various tissues, MjHIF-1α and MjVHL were more highly expressed in the intestine than in any other organ tissues. In hypoxia experiments, HIF-induced expression levels of MjHIF-1α in the hypoxic group increased significantly for 24 h after initiating hypoxia stimulation and expression of MjVHL decreased significantly for 6 h after hypoxia stimulation ( P  < 0.05). [ABSTRACT FROM AUTHOR]

The Bzura-7 pond (Łódź, Poland) is a typical shallow and shady urban reservoir situated on the Bzura River that is exposed to pollutants introduced mainly by internal loads and the supply from the catchment. In 2010–2012, the following characteristics were observed in the pond: a high allochthonous input of organic matter, high concentration of ammonium, low concentration of dissolved oxygen and low diversity of zooplankton, dominated mainly by Daphnia spp. From January to June 2013, restoration measures were performed, including sediment removal, increasing light access to the pond and construction of a sequential sedimentation-biofiltration system (SSBS). The aim of the present study was to investigate how the water quality in the Bzura-7 pond was affected by the restoration process, which included reducing pollutant inflows and enhancing habitat potential, thus increasing the diversity of this ecosystem. Restoration efforts improved the chemical and physical parameters of the water. The oxygen concentration increased, and the concentrations of TN and ammonium significantly decreased. Despite the increase in pond lighting, the growth of cyanobacteria was limited. However, we observed increased abundance of green algae and diatoms but less than adequate changes in the zooplankton community structures. Although we observed a significant increase in the zooplankton species richness after restoration, this increase was related to the small-bodied groups of zooplankton, rotifers and bosminiids, characteristic of eutrophic ecosystems. In addition, a planktivorous fish – sunbleak ( Leucaspius delineatus ) – was identified as an unintended side effect of the restoration effort. Further conservation efforts in the Bzura-7 pond and monitoring of results are still needed. [ABSTRACT FROM AUTHOR]

Degradation of particulate organic carbon (POC) such as leaf litter might deplete dissolved oxygen within the upper layers of bank filtration, an efficient and robust barrier for pathogens and for various organic micro-pollutants (OMP) in water supply systems worldwide. The degradation of OMP during bank filtration depends on the redox conditions. The present study aimed at identifying the impacts and fates of different local leaves on the oxygen consumption and the possible biological degradation of indicator OMP. Oxygen concentrations initially decreased within the columns from around 8 mg/L in the influent to low concentrations indicating extensive consumption within a short travel distance. Still a substantial oxygen consumption was observed after 250 days. OMP concentrations were not significantly affected by the microbial processes. A layer of calcium carbonate crystallites was observed on the POC layer. Some leaf fragments appeared to be persistant towards degradation and the carbon content relative to nitrogen and sulfur contents decreased within 250 days. The results demonstrate that trees at bank filtration sites might have a strong long-term impact on the subsurface redox conditions. [ABSTRACT FROM AUTHOR]

We examine the current status of dissolved oxygen (DO) and its trend over the past 25 years in the lower Pearl River Estuary, a large eutrophic estuary located in Southern China and surrounded by large cities including Hong Kong, Shenzhen and Guangzhou. Monthly cruises conducted from April 2010 to March 2011 clearly show that DO depletion began to emerge in the bottom layer of the lower estuary off Hong Kong in June, and became fully developed in July and August when oxygen-deficient water occupied ∼1000 km 2 before gradually becoming re-oxygenated in September and October. The development of the low oxygen zone was closely coupled with phytoplankton blooms in the surface water, which was supersaturated with respect to DO suggesting the importance of autochthonous organic matter in fueling bottom DO consumption after settling through the pycnocline. Long-term monitoring data collected in the study area adjacent to Hong Kong by the Hong Kong Environmental Protection Department showed a decreasing trend of ∼2 ± 0.9 μmol kg −1 yr −1 in the annual minimum DO concentration in bottom water over the past 25 years. Associated with the decrease in DO was an increase in the annual maximum surface concentration of dissolved inorganic nitrogen (DIN) at a rate of ∼1.4 ± 0.3 μmol kg −1 yr −1 , suggesting again that eutrophication is the most plausible driver of oxygen deficiency in this region. Therefore, our monthly cruises, along with the decadal monitoring data, reveal a large low oxygen zone, likely developing into a large hypoxic zone driven primarily by anthropogenic eutrophication. This new development suggests environmental stressors such as eutrophication may have a cascading effect, with important and expensive consequences for the regional environment. [ABSTRACT FROM AUTHOR]

Bioremediation is one of the general methods to treat pollutants in soil, sediment, and groundwater. However, the low concentration and restricted dispersion of dissolved oxygen (DO) in these areas have limited the efficiency of remediation especially for microorganisms that require oxygen to grow. Calcium peroxide (CaO 2 ) is one of the oxygen-releasing compounds and has been applied to magnify the remediation efficacy of polluting areas. In this study, CaO 2 nanoparticles (NPs) were synthesized and evaluated by wet chemistry methods as well as dry and wet grinding processes. The characteristics of CaO 2 particles and NPs were analyzed and compared by dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and X-ray powder diffraction. Our results showed that wet-grinded CaO 2 NPs had an average particle size of around 110 nm and were more stable compared to other particles from aggregation and sedimentation tests. In addition, we also observed that CaO 2 NPs had better DO characteristics and patterns; these NPs generated higher DO levels than their non-grinded form. Accordingly, our results suggested that wet-grinding CaO 2 particles to nanoscale could benefit their usage in bioremediation. [ABSTRACT FROM AUTHOR]

Two phase bioreactor was constructed, designed and developed to evaluate the chlorpyrifos remediation. Six biotic and abiotic factors (substrate-loading rate, slurry phase pH, slurry phase dissolved oxygen (DO), soil water ratio, temperature and soil micro flora load) were evaluated by design of experimental (DOE) methodology employing Taguchi's orthogonal array (OA). The selected six factors were considered at two levels L-8 array (2^7, 15 experiments) in the experimental design. The optimum operating conditions obtained from the methodology showed enhanced chlorpyrifos degradation from 283.86 µg/g to 955.364 µg/g by overall 70.34% of enhancement. In the present study, with the help of few well defined experimental parameters a mathematical model was constructed to understand the complex bioremediation process and optimize the approximate parameters upto great accuracy. [ABSTRACT FROM AUTHOR]

Both a low concentration of dissolved oxygen and the toxicity of a high concentration of BTEX inhibit the bioremediation of BTEX in groundwater. A novel method of preparing encapsulated oxygen-releasing beads (encap-ORBs) for the biodegradation of BTEX in groundwater was developed. Experimental results show that the integrality and oxygen-releasing capacity of encap-ORBs exceeded those of ORBs. The use of polyvinyl alcohol (PVA) with high M.W. to prepare encap-ORBs improved their integrality. The encap-ORBs effectively released oxygen for 128 days. High concentration of BTEX (480 mg L −1 ) inhibited the biodegradation by the free cells. Immobilization of degraders in the encap-ORB alleviated the inhibition. Scanning electron microscope analysis reveals that the BTEX degraders grew on the surface of encap-ORB after bioremediation. The above results indicate that the encap-ORBs were effective in the bioremediation of BTEX at high concentration in groundwater. [ABSTRACT FROM AUTHOR]

Dissolved oxygen fluctuations in a river over a short period of time were assumed to be caused by the microbial growth dynamics, and a stochastic model was built for oxygen uptake. As a case study, biochemical oxygen demand (BOD) was measured in water from the Ura River, Oita River, and Otozu River flowing through the urban district of Oita, Japan. Water samples were taken from each river and partitioned into BOD bottles. BOD was measured in five of these bottles on each of nine days. The experimental results show that the average daily BOD decreased exponentially as expressed by the Streeter-Phelps equation. A wide range of the measured five daily BOD-values was expressed by the difference between the maximum and minimum BOD-values on each day for each river. After the first few days the range became smaller. The proposed stochastic model describes the observed experimental fluctuation of BOD over time. Eighty to ninety percent of the experimental BOD plots are within the 80% probability range given by the model. The uncertainty of BOD prediction can be expressed by the error which is the non-dimensional ratio of the range to the median. Modeled and experimental results reveal that the error is about 0.5–1 (50–100% of expected value) after a few days. This suggests that the BOD predicted by deterministic water quality models can include uncertainty, i.e. the actual BOD can be a quarter or double of the simulated value, for the time scale of a few days. For a longer period, e.g. more than a week, the error can become even more significant. [ABSTRACT FROM AUTHOR]

This study analyzed how environmental, temporal, and spatial variables influenced the distribution and diversity of waterbird assemblages during the dry and rainy seasons in a subtropical estuarine complex in southern Brazil, a world heritage site. From March 2020 to February 2021, we determined the alpha and beta diversities of waterbird in the Paranaguá Estuarine Complex (PEC), southern Brazil, by sampling 36 transects distributed in three bays. Altogether we recorded 46 species distributed in 17 families and eight genera. Despite the similar species richness observed in the dry versus rainy season (41 and 39 species, respectively), we found a weak seasonal influence on the composition of the waterbird assemblage due to the presence of migratory species. Species richness was positively related with water temperature and dissolved oxygen during the wet season. While in the dry season, we recorded a negative relationship between species diversity and turbidity. Despite the great diversity of waterbird species recorded in the PEC, we did not detect a consistent pattern of alpha and beta diversity responses. Balanced variation in abundance was the component that most contributed to total beta diversity, which is consistent for highly mobile species that roam heterogeneous landscapes. Due to their high mobility, waterbird quickly track dynamic features in time and space. The lack of apparent patterns in species distribution and alpha and beta diversity may reflect this dynamic. Our findings reinforce the need to use robust, long-term databases to understand and monitor beta diversity, providing information to support practical actions to protect local and regional biodiversity. Therefore, strategic management plans that use integrated protection networks and aim at biodiversity conservation at different scales must consider these results. [Display omitted] • Subtropical estuaries are dynamic environments with well-defined environmental gradients; resources vary in time and space, driving the movement of waterbirds. • The abundance of resources, the detection capacity and accessibility of them are equaly important. • Balanced variation in abundance is the dominant beta diversity component for waterbird assemblages in a subtropical estuarine system. • Understanding beta diversity is essential for protecting waterbird diversity at many scales and can directly assist in conservation planning. [ABSTRACT FROM AUTHOR]

Constructed wetlands have been used globally for wastewater treatment owing to low energy inputs and operating costs. However, the impact of their long-term operation on groundwater microbial communities is still unclear. This study aims to investigate the effects and further reveal the linkage between a large-scale surface flow constructed wetland (in operation for 14 years) and groundwater. Changes in the characteristics of groundwater microbial communities and their potential influencing factors were studied based on hydrochemical analysis, Illumina MiSeq sequencing, and multivariate statistical analysis methods. Results show that the long-term operation wetland significantly elevated groundwater nutrient levels and increased the risk of ammonia nitrogen pollution compared to background values. An apparent heterogeneity of microbial communities exhibited in the vertical direction and a similarity in the horizontal direction. Wetland operations substantially altered the structure of microbial communities at 3, 5, and 12 m depths, particularly a reduced abundance of denitrifying and chemoheterotrophic functional genera. The formation and evolution of groundwater microbial community structure mainly subjected to the contributions of dissolved oxygen (33.70%), total nitrogen (21.40%), dissolved organic carbon (11.09%), and pH (10.60%) variations resulted from the wetland operation and largely differed in depths. A combined effect of these factors on the groundwater should be concerned for such a long-term running wetland system. This study provides a new insight into the responses of groundwater microbial community structure driving by wetland operation and a better understanding of corresponding variation of microbial-based geochemical processes. • Wetland operation caused NH 4 +-N contamination in shallow groundwater. • Wetland operation led to changes in microbial communities at 3, 5, and 12m depth. • Abundance of denitrifying and chemoautotrophic bacterial genera was reduced. • DO, TN, DOC, and pH are the main drivers of change in the microbial community. [ABSTRACT FROM AUTHOR]

Oxygen availability in different media during heat treatment (8 h at 80 °C) and the related vitamin C loss was assessed. Dissolved oxygen in water containing 3 mmol kg −1 of ascorbic acid decreased initially and seemed to be replaced by oxygen from the headspace in the course of time, as oxygen values increased again. In apple purée and carrot purée in contrast, oxygen was depleted within 60 min. Vitamin C in ultrapure water was stable even in the presence of oxygen. A trigger seemed to be crucial to launch vitamin C degradation. Fe 3+ ions added to water, but also the media Mc Ilvaine citrate-phosphate buffer (pH 3.5) or apple purée, initiated degradation. Adding Fe 3+ ions to apple purée did not accelerate vitamin C degradation but shifted the equilibrium between ascorbic acid and dehydroascorbic acid to the latter. Oxygen deprivation stabilized completely vitamin C, independently of the medium tested. A temperature decrease to 70 or 60 °C, in contrast, had no effect on the degradation extent of vitamin C in water containing 20 μmol kg −1 Fe 3+ ions but led to complete stability in apple purée. [ABSTRACT FROM AUTHOR]

Little is known about levels of dissolved oxygen fish are exposed to daily in typical urbanised tropical wetlands found along the Great Barrier Reef coastline. This study investigates diel dissolved oxygen (DO) dynamics in one of these typical urbanised wetlands, in tropical North Queensland, Australia. High frequency data loggers (DO, temperature, depth) were deployed for several days over the summer months in different tidal pools and channels that fish use as temporal or permanent refuges. DO was extremely variable over a 24 h cycle, and across the small-scale wetland. The high spatial and temporal DO variability measured was affected by time of day and tidal factors, namely water depth, tidal range and tidal direction (flood vs ebb). For the duration of the logging time, DO was mainly above the adopted threshold for hypoxia (50% saturation), however, for around 11% of the time, and on almost every logging day, DO values fell below the threshold, including a severe hypoxic event (<5% saturation) that continued for several hours. Fish still use this wetland intensively, so must be able to cope with low DO periods. Despite the ability of fish to tolerate extreme conditions, continuing urban expansion is likely to lead to further water quality degradation and so potential loss of nursery ground value. There is a substantial discontinuity between the recommended DO values in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality and the values observed in this wetland, highlighting the limited value of these guidelines for management purposes. Local and regional high frequency data monitoring programs, in conjunction with local exposure risk studies are needed to underpin the development of the management that will ensure the sustainability of coastal wetlands. [ABSTRACT FROM AUTHOR]

The effects of different aeration strategies including tidal flow (TF), effluent recirculation (ER) and artificial aeration (AA) on performance of vertical flow constructed wetland (VFCW), horizontal flow constructed wetland (HFCW) and hybrid constructed wetland (HCW) are comprehensively and critically reviewed in this paper. The removal efficiencies of nine types of intensified constructed wetlands (CWs) were examined in detail and their mean and standard deviation were estimated at 89 ± 11%, 84 ± 12%, 81 ± 17% and 63 ± 20% for total suspended solids (TSS), chemical oxygen demand (COD), ammonium-nitrogen (NH 4 + N) and total nitrogen (TN), respectively. From the studied CWs, ER-HCW, TF-HCW, AA-VFCW and ER-VFCW emerged as the four best performing systems. The overall removal efficiency of TSS, COD, NH 4 + N and TN by ER-HCW was 98 ± 2%, 85 ± 11%, 83 ± 15% and 73 ± 11%, respectively. Specifically, the ER enhances the interactions between pollutants and micro-organisms, consequently, the efficient removal of NH 4 + N and TN has been achieved in ER-HCW. The TF has a positive effect in refreshing the wetland with fresh air to enhance the dissolved oxygen (DO) in the system. In case of AA, intermittent aeration is more effective than continuous aeration, as it facilitates the establishment of aerobic and anaerobic conditions suitable for nitrification and denitrification. Statistical analysis shows that DO, organic loading rate and specific surface area requirement are the most significant factors that influence the performance of intensified CWs. [ABSTRACT FROM AUTHOR]

Freshwater bodies are increasingly affected by reductions in water quantity and quality and by invasions of exotic species. To protect water quantity and maintain the ecological integrity of many water bodies in central Florida, a program of adopting Minimum Flows and Levels (MFLs) has begun for both lentic and lotic waters. The purpose of this study was to determine whether there were relationships between discharge and stage, water quality, and biological parameters for Volusia Blue Spring, a first magnitude spring (discharge > 380,000 m 3 day −1 or 100 mgd) for which an MFL program was adopted in 2006. Over the course of fourteen years, we assessed fish density and diversity weekly, monthly, or seasonally with seine and snorkel counts. We evaluated annual changes in the assemblages for relationships with water quantity and quality. Low discharge and dissolved oxygen combined with high stage and conductivity produced a fish population with a lower density and diversity in 2014 than in previous years. Densities of fish taxonomic/functional groups also were low in 2014 and measures of water quantity were significant predictors of fish assemblage structure. As a result of the strong relationships between variation in discharge and an array of chemical and biological characteristics of the spring, we conclude that maintaining the historical discharge rate is important for preserving the ecological integrity of Volusia Blue Spring. [ABSTRACT FROM AUTHOR]

Waterways in urban areas often act as repositories for sewage, industrial waste, and environmental contaminants. In response, inhabitants of these watersheds undergo physiological adaptations specific to their respective environments. Effects of these stressors can be assayed by quantification of various well-documented biomarkers in sentinel species such as the Atlantic Ribbed mussel, Geukensia demissa , a native to the Bronx River Estuary, Bronx, NY, USA. Heat shock protein 70 (Hsp70) is a universally expressed biomarker for an array of environmental stressors including toxins and low dissolved oxygen. To better understand the mechanisms by which organisms tolerate their contaminated environments, we monitored the constitutive and heat shock-induced levels of two proteins: Hsp70 and acetylcholinesterase (AChE) in natural populations of G. demissa from differentially impacted sites: the Bronx River and Greenwich Cove estuaries. We show that G. demissa from the Bronx River exhibits a higher level of constitutive Hsp70, and launches a more rapid and robust heat shock response than does its Greenwich Cove counterpart. In addition, AChE levels are recovered more quickly in Bronx River mussels. Based on response pattern investigations from heat stress as well as constitutive expression, we suggest that the Hsp70/AChE chaperone/client relationship exemplifies the unique adaptive mechanisms utilized by organisms in order to tolerate environmentally impacted habitats. Results from this study offer important insights from an ecological perspective into the molecular and cellular basis of stress response and provide valuable information regarding adaptation to the increased demands of challenging environments. [ABSTRACT FROM AUTHOR]

Mangrove sites are constantly under tidal regimes, where there is variation of dissolved oxygen and saline content in water. This study evaluated the effects of varying salinity in Avicennia schaueriana , an abundant species in the sea-mangrove-river interface. Seedlings of A. schaueriana were harvested at the riverbank and placed in different saline and nutrient solutions in a greenhouse in order to simulate a saline flow. After 7 acclimatization days, plants were exposed to the following saline concentrations: 0, 50, 170 and 250 mM NaCl, for a period of 30 days. After this, leaf gas exchange, chlorophyll a fluorescence, Falker chlorophyll index, leaf ultrastructure and micromorphology were evaluated. The highest saline concentration affected mainly the CO 2 assimilation, internal CO 2 concentration and the intrinsic efficiency of water use. The chlorophyll a fluorescence and Falker index were not significantly affected by any of the saline conditions, however chloroplast was damaged. Concomitantly, leaf salt glands clearly evidenced a higher salt secretion, when plants were submitted to the greatest saline concentration. The results indicated that A. schaueriana tolerates different salt concentration in the mangrove and excretes salt excess by salt gland, and this can attenuate the saline stress. However, when exposed to longer periods of higher salt fluxes the plant growth can be affected. [ABSTRACT FROM AUTHOR]

At Lough Hyne Marine Reserve in SW Ireland, shallow subtidal, under-rock biodiversity was investigated to assess (i) any deleterious effects of scientific sampling and (ii) quantitative baseline community patterns. Comparisons were made between 10 sites with annual rock-turning disturbance and 10 with multi-decadal (historical) disturbance. At each site, shallow subtidal rocks (N = 1289 total) were lifted, organisms recorded, and rocks replaced in their original position. Biodiversity indices were calculated to evaluate how diversity varied with location within the lough, frequency of sampling disturbance, degree of hypoxia/anoxia, dissolved oxygen (DO) concentration, and number of rocks turned. The richness of solitary invertebrates surveyed in situ averaged 21 taxa per site with significantly more in the South Basin (near the lough's connection to the ocean) than in the North Basin. The Shannon-Wiener Index did not differ significantly with variables investigated. However, evenness was higher at annually disturbed sites than at historical ones where anemones with algal symbionts often dominated. Several sites were hypoxic to anoxic under the shallow subtidal rocks. Cup corals were most abundant in the South Basin; DO was a crucial explanatory variable of these sensitive species. Solitary ascidians were most abundant at South-Basin annual sites with DO levels being a highly significant explanatory variable. [ABSTRACT FROM AUTHOR]

Campylobacter jejuni survival in aerobic environments has been suggested to be mediated by biofilm formation. Biofilm formation by eight C. jejuni strains under both aerobic and microaerobic conditions in different broths (Mueller-Hinton (MH), Bolton and Brucella) was quantified. The dissolved oxygen (DO) content of the broths under both incubation atmospheres was determined. Biofilm formation for all strains was highest in MH broth under both incubation atmospheres. Four strains had lower biofilm formation in MH under aerobic as compared to microaerobic incubation, while biofilm formation by the other four strains did not differ under the 2 atm. Two strains had higher biofilm formation under aerobic as compared to microaerobic atmospheres in Bolton broth. Biofilm formation by all other strains in Bolton, and all strains in Brucella broth, did not differ under the 2 atm. Under aerobic incubation DO levels in MH > Brucella > Bolton broth. Under microaerobic conditions levels in MH = Brucella > Bolton broth. Levels of DO in MH and Brucella broth were lower under microaerobic conditions but those of Bolton did not differ under the 2 atm. Experimental conditions and especially the DO of broth media confound previous conclusions drawn about aerobic biofilm formation by C. jejuni . [ABSTRACT FROM AUTHOR]

This work proposes an on-line hybrid intelligent control system based on a genetic algorithm (GA) evolving fuzzy wavelet neural network software sensor to control dissolved oxygen (DO) in an anaerobic/anoxic/oxic process for treating papermaking wastewater. With the self-learning and memory abilities of neural network, handling the uncertainty capacity of fuzzy logic, analyzing local detail superiority of wavelet transform and global search of GA, this proposed control system can extract the dynamic behavior and complex interrelationships between various operation variables. The results indicate that the reasonable forecasting and control performances were achieved with optimal DO, and the effluent quality was stable at and below the desired values in real time. Our proposed hybrid approach proved to be a robust and effective DO control tool, attaining not only adequate effluent quality but also minimizing the demand for energy, and is easily integrated into a global monitoring system for purposes of cost management. [ABSTRACT FROM AUTHOR]

This study investigated the geochemical processes and the suitability for irrigation purposes of surface water and groundwater in the Yarkant River Basin, northwest China. The results showed that the surface water was moderately alkaline and neutral to slightly alkaline in the groundwater. The mean values for most ions in the groundwater were higher than those in the surface water. Geochemical method and hydrogen and oxygen isotope revealed that hydrochemical were mainly affected by dissolved evaporite minerals, ion exchange processes, and anthropogenic activities. Still, the geochemical processes of in surface water and groundwater were different. Additionally, three and four factors were extracted by factor analyses of surface water and groundwater, respectively, which distinguished the hydrochemical from natural origins and anthropogenic activities in more detail. The surface water and some groundwater in the south of the study area were suitable for irrigation processes. However, many groundwaters in the north were unsuitable for irrigation, because of their high sodium levels and salinity. The study results provide a theoretical basis for the sustainable utilization of regional water resources. • Significantly different hydrochemistry characteristics and factors were seen among sites and groups. • Sources of elements were estimated by three and four factors for surface water and groundwater, respectively. • All surface water samples were suitable for irrigation, but the groundwater was very different. [ABSTRACT FROM AUTHOR]

Hydrated salts are thought to be a surface component of many different solid bodies in the solar system such as the icy-world satellites, especially the large ones of Jupiter and Saturn. In this context, three hydrated salts of interest in planetary sciences – natron (Na 2 CO 3 ·10H 2 O), mirabilite (Na 2 SO 4 ·10H 2 O), and epsomite (MgSO 4 ·7H 2 O) – were selected and their NIR (0.8–3.6 μm) reflectance properties were studied as a function of temperature after diluting them in water. The main goal of these experiments is to characterize the evolution induced in the hydrated salt NIR spectra by the mixing and melting with water followed by freezing of the samples down to 95 K. Our results show that mixing of hydrated salts with water induces a complex phenomenology characterized by the formation of new bonds and absorption features. In addition, the shape and minimum position of the NIR spectral features here analyzed are temperature-dependent. The present laboratory study will be extremely useful to interpret the high-resolution data of Jupiter's icy satellites surfaces which will be available in the next future thanks to the MISE and MAJIS instruments aboard NASA Europa Clipper and ESA JUICE spacecraft, respectively. • selected hydrated salts of interest in planetary sciences - natron, mirabilite, and epsomite - are considered in this study. • NIR reflectance properties of these salts were studied after mixing with water followed by freezing down to 95 K. • a complex phenomenology characterizes these experiments, inducing the formation of new bonds and new NIR absorption features. • the shape and minimum position of the NIR spectral features are temperature-dependent. • these laboratory study will be useful to interpret the new HR data of Jupiter's icy satellites surfaces available thanks to the Europa Clipper and JUICE missions. [ABSTRACT FROM AUTHOR]

Deep learning methods, which have strong capabilities for mapping highly nonlinear relationships with acceptable calculation speed, have been increasingly applied for water quality prediction in recent studies. However, it is argued that the practicality of deep learning methods is limited due to the lack of physical mechanics to explain the prediction results of water quality changes. A knowledge gap exists in rationalizing the deep learning results for water quality predictions. To address this gap, an interpretable deep learning framework was established to predict the spatiotemporal variations of water quality parameters in a large spatial region. Mereological, land-use, and socioeconomic variables were adopted to predict the daily variations of stream water quality parameters across 138 sub-catchments in a total of over 575,250 km2 in southern China. The coefficients of determination of chemical oxygen demand (COD), total phosphorus (TP), and total nitrogen (TN) predictions were over 0.80, suggesting a satisfactory prediction performance. The model performance in terms of prediction accuracy could be improved by involving land-use and socioeconomic predictors in addition to hydrological variables. The SHapley Additive exPlanations method used in this study was demonstrated to be effective for interpreting the prediction results by identifying the significant variables and reasoning their influencing directions on the variation of each water quality parameter. The air temperature, proportion of forest area, grain production, population density, and proportion of urban area in each sub-catchment as well as the accumulated rainfall within the previous 3 days were identified as the most significant variables affecting the variations of dissolved oxygen, COD, ammoniacal nitrogen(NH 3 –N), TN, TP, and turbidity in the stream water in the case area, respectively. [Display omitted] • An innovative interpretable deep learning method on water quality predictions. • The SHapley Additive exPlanations method could interpret the prediction results. • Economic categorical data could explain water quality variations at a large scale. • The prediction accuracy could be improved by involving land-use predictors. [ABSTRACT FROM AUTHOR]

Bar-built estuaries (BBEs) or intermittently closed/open lagoons (ICOLs) are common to coastal regions experiencing episodic river flows and seasonal precipitation changes along the US West Coast. Unique to Mediterranean climates, BBEs have a hydrologic mixing regime and variation in water chemistry characteristics resulting from seasonal breaches and closures of their mouth and watershed inputs. This study observes spatiotemporal variability in dissolved oxygen (DO) in a small bar-built estuary in Carmel, CA during variable morphological states. For this study, field measurements were collected using dissolved oxygen loggers during a seasonal transition from fully open to fully closed states to determine the spatiotemporal variability of dissolved oxygen within the three main branches of Carmel River Lagoon. The data collected spanned a 6-month (February to August 2020) period, covering several transitions from fully open to intermittently closed to fully closed mouth state. This study did not document any periods within the lagoon when dissolved oxygen concentrations were uniformly below water quality objective levels (5 mg/L) suggesting that during the entire period of this investigation, portions of the lagoon supported high oxygen conditions while also supporting a variety of other water chemistry characteristic zones, unique to BBEs. The dissolved oxygen fluctuations were closely tied to the temporal effects of environmental forcing (river discharge) on the seasonal transition of river mouth morphological state from fully open to fully closed. The main conclusion is that during open mouth states, relative DO variability in the bottom of the main channel is low and more similar to surface waters, indicating mixing, and during closed mouth states vertical location in the water column matters more. Furthermore, variability between sites suggests single point observations of DO cannot accurately represent the distribution of DO within a BBE. • Bar-built estuarine dissolved oxygen levels depend on mouth morphological state (open vs. closed) in well-connected regions. • Locations with less connectivity to the river channel have low dissolved oxygen periods even when river discharge is high. • Low variance in dissolved oxygen is associated with well-connected regions of the lagoon. • Despite small separation distances (<325 m), there is spatial variability of dissolved oxygen levels within the lagoon system. [ABSTRACT FROM AUTHOR]

Urban and agricultural development of the South Florida peninsula has disrupted historic freshwater flow in the Everglades, a hydrologically connected ecosystem stretching from central Florida to the Gulf of Mexico, USA. Current system-scale restoration efforts aim to restore natural hydrologic regimes to reestablish pre-drainage ecosystem functioning through increased water availability, quality and timing. Aquatic transport of carbon in this ecosystem, primarily as dissolved organic carbon (DOC), plays a critical role in biogeochemical cycling and food-web dynamics, and will be affected both by water management policies and climate change. To better understand DOC dynamics in South Florida estuaries and how hydrology, climate and water management may affect them, 14 years of monthly data collected in the Shark River estuary were used to examine DOC flux dynamics in a broader environmental context. Multivariate statistical methods were applied to long-term datasets for hydrology, water quality and climate to untangle the interconnected environmental drivers that control DOC export at monthly and annual scales. DOC fluxes were determined to be primarily controlled by hydrology but also by seasonality and long-term climate patterns and episodic weather events. A four-component model (salinity, rainfall, inflow, Atlantic Multidecadal Oscillation) capable of predicting DOC fluxes (R 2 = 0.84, p < 0.0001, n = 155) was established and applied to potential climate change scenarios for the Everglades to assess DOC flux response to climate and restoration variables. The majority of scenario runs indicated that DOC export from the Everglades is expected to decrease due to future changes in rainfall, water management and salinity. [ABSTRACT FROM AUTHOR]

Water is an important component to human life. The major aims of the present work are to assess the quality of the ground water and its impact in Villupuram District of Tamilnadu. The present study focus to bring an awareness among the people about the quality of ground water by taking water samples from various locations for Physico – Chemical analysis of the ground water . This analysis result was compared with the WHO, ICMR, USPH and European standards of drinking water quality parameters with the following water quality parameters namely pH , Electrical conductivity, Cl, , Na, K, Ca , Mg, Total dissolved solids, Total hardness, Dissolved oxygen, Fluoride etc. Various chemical methods have been employed to investigate the extent level of pollution in ground water. [ABSTRACT FROM AUTHOR]

Global distribution and health threats of microcystins (MCs) have received much more attention, but there are still significant knowledge gaps in the peak periods and driving factors of MC in different phases of freshwater ecosystems. Thus, we systematically analyzed the annual variation of different MC congeners (-LR, -RR, and -YR, where L, R, and Y respectively represent leucine, arginine, and tyrosine) in particulates, dissolved water, and sediments in three eutrophic bays of Lake Taihu, China. The results indicated that particulate MCs concentration was the highest, followed by dissolved and sediment MC, with the mean concentration of 7.58 μg/L, 1.48 μg/L, and 0.15 μg/g (DW), respectively. Except for particulate MC, the concentrations of the other two types of MC showed significant differences among the three bays. The dominant congeners of the three types of MCs were different, with the highest proportion of MC-LR being observed in sediment MCs and the lowest in particulate MCs. The peak period of the three types of MC was also different, with particulate MCs reaching their peak in July and October, dissolved MCs in May to July and October, and sediment MCs reaching their peak in September. Consistent with our hypothesis, the dynamics of different types of MCs were driven by different environmental factors. Particulate MCs were primarily related to biological parameters, followed by TP and dissolved carbon. By contrast, dissolved MCs strongly correlated with water temperature and dissolved oxygen. While sediment MCs were primarily driven by properties of sediments, followed by different forms of nitrogen in the water column. Our results suggested that particulate and dissolved MCs in northern Lake Taihu pose high health threats, especially in the peak period. Moreover, a more detailed and targeted risk management strategy should be designed to prevent the possible hazards posed by different types of MC. [Display omitted] • Particulate MC concentration was highest, followed by dissolved and sediment MCs. • The peak periods of three types of MC were different. • Particulate MC was mainly related to the dynamics of phytoplankton density. • Dissolved MC was positively related to water temperature and negatively related to DO. • Sediment MC was strongly related to sediment properties and TN in water column. [ABSTRACT FROM AUTHOR]

The aquatic environment, linked to the sustainable development of human existence and ecological environment, is influenced comprehensively by anthropogenic and natural activities. In light of the continuously low concentration of dissolved oxygen (DO) in surface water in plain river networks and the phenomenon of delay in the improvement of surface water quality, this research aims to introduce a method that may be utilized in identifying the critical driving forces of DO in surface water and their lagging characteristics, which will contribute to the assessment and adjustment of water quality drivers and/or policies. The research analyzes a typical small watershed in a river network region of the Yangtze River Delta plain as the study area, collecting 35-year (1986–2020) data on several water quality parameters, decades of anthropogenic activities, and two natural factors. The time series methods of vector autoregressive model, Granger causality tests, forecast error variance decompositions, and impulse response functions (hereinafter referred to as VAR+), which are rarely applied in related research, were employed in this study and proved helpful for screening out pivotal drivers and capturing the lagging responses of DO level to driving forces at each lagged time. Results show that there exists a fluctuating drop in DO level in surface water from 1986 to 2008 and a steady climb from 2008 to 2020, with the lowest DO level being present in 2008. The impulsive perturbations of phosphate fertilizer consumption (PFC), motor vessel number, and precipitation minimally increase DO concentration, while the impulsive perturbation of gross domestic product (GDP) causes the sharpest drop in DO level. With these perturbations, the driving force of PFC persists for approximately seven years, and the driving forces of water temperature, permanent population, and GDP persist for only five years. Future research could be conducted with spatial hysteresis, selection of lag order and variable quantity within the model, as well as intermediate variables between drivers and DO level for exploring driving pathways and mechanisms. [Display omitted] • VAR based method captures the lagging responses of DO level to driving forces. • The driving force of phosphorus fertilizer on DO level lasts for 7 years. • Phosphorus fertilizer and rainfall are key drivers of DO level in surface water. [ABSTRACT FROM AUTHOR]