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To determine ecological and health risk assessment of the Berdan and Göksu river waters, principal physical and biochemical variables were measured monthly between September 2021 and August 2022 in the Berdan and Göksu river basins. Ecological risk assessment of the studied river basins indicated that both the Berdan and Göksu river waters were contaminated by phosphorus. Potential health risk assessment of the Berdan and Göksu river basins showed that the calculated Health Quotient values in the two visited stations in the Berdan river exceeded 0.1 indicating low cancer risk for both adults and children whilst one visited station in the Göksu River basin showed low cancer risk for children. The health risk assessment also indicated that the Health Quotient values calculated for children were consistently higher than those calculated for adults, showing that children were potentially at higher risk for health hazards from nitrate. [ABSTRACT FROM AUTHOR]

Groundwater is the main water supply source especially in arid/semiarid regions, whose quality has been widely concerned. To clarify the spatial distribution, occurrence and the impacts of fluoride (F−) and nitrate (NO3−) in groundwater, 26 groundwater samples were collected from domestic water wells and agricultural irrigation wells in Xilinhot city, a famous tourist city on the Xilin Gol grassland of China. The integration of statistical analysis and hydrochemical diagrams and the model of health risk assessment recommended by the USEPA were carried out in the study. The analysis reveals that the groundwater is weakly alkaline, and the hydrochemical facies are mainly HCO3‐Ca·Mg and SO4·Cl‐ Na + K, which are controlled by natural processes and anthropogenic factors in the study area. Groundwater with high fluorine is chiefly located in the west of the study area, and high‐nitrate groundwater is chiefly located in the middle and southern parts of the study area. Fluoride in groundwater is predominantly derived by the weathering and dissolution of fluoride‐bearing minerals and ion exchange. The values of hazard index (HI) of 65.38% groundwater samples were greater than the recommended limit for noncarcinogenic risk (HI = 1) for children, followed by 38.46% for adult females and 30.77% for adult males. The water quality of the urban water supply should be treated. At the same time, contaminant filters and other instruments should be supplied to residents in pastoral area to reduce fluoride and nitrate concentration in drinking water, which will mitigate health risks and ensure the safety of drinking water in the study area. [ABSTRACT FROM AUTHOR]

Groundwater nitrate pollution is a serious environmental problem worldwide, which is demonstrated influenced by land use/land cover (LULC) patterns. The current study was carried out to investigate the effects of LULC patterns to the nitrate pollution of shallow groundwater in the north piedmont plain of the Qinling Mountain (NPQM) using an ensemble machine learning method named random forest. Groundwater nitrate data and existing LULC patterns datasets were utilized to conduct the study. LULC patterns were quantified using a curved streamline shaped contributing area stratagem, and subsequently used to create training and test datasets together with the groundwater nitrate data for construction of random forest model. The results of this study indicated arable and urban land were the main LULC types in the NPQM, and urbanization induced the occupation of arable land by urban land from 2015 to 2019. Shallow groundwater in the NPQM was polluted by nitrate in both 2015 and 2019, with area of groundwater nitrate concentration exceeding the standard limitation recommended by the WHO (50 mg/L as NO3—) reduced from 2762.2 km2 in 2015 to 2184.3 km2 in 2019, showing an alleviating trend. Arable and urban land were the main LULC types contributing to groundwater nitrate pollution. Nitrate accumulated in the soil from manure and chemical fertilizer was the main source for groundwater nitrate pollution in arable land, while manure and sewage were the main source in urban land. The study provides scientific insights for sustainable groundwater protection in the NPQM. [ABSTRACT FROM AUTHOR]

The Arborea plain in Sardinia (Italy) is classified as a nitrate vulnerable zone (NVZ). In the present study, the individual work steps that are necessary to progress from the existing 3D hydrogeological model to a 3D numerical groundwater model using the interactive finite-element simulation system FEFLOW 7.4 are shown. The results of the transient flow model highlight the influence of the drainage network on the overall groundwater management: the total water volume drained by the ditches accounted for approximately 58% of the annual outflow volume. The numerical transport simulations conducted from 2012 to 2020 using hypothetical field-based nitrate input scenarios globally underestimated the high concentrations that were observed in the NVZ. However, as observed in the field, the computed nitrate concentrations in December 2020 still varied strongly in space, from several mg L−1 to several hundreds of mg L−1. The origin of these remaining local hotspots is not yet known. The modeling of rainfall fluctuations under the influence of climate change revealed a general long-term decline in the groundwater level of several tens of centimeters in the long term and, in conjunction with a zero-nitrate scenario, led to a significant decrease in nitrate pollution. Although hotspots were attenuated, the concentrations at several monitoring wells still exceeded the limit value of 50 mg L−1. [ABSTRACT FROM AUTHOR]

Abstract Determining situation of groundwater vulnerability plays a crucial role in studying the groundwater resource management. Generally, the preparation of reliable groundwater vulnerability maps provides targeted and practical scientific measures for the protection and management of groundwater resources. In this study, in order to evaluate the groundwater vulnerability of Kerman–Baghin plain aquifer, two developed indicators including composite DRASTIC index (CD) and nitrate vulnerability index (NVI) based on DRASTIC index were considered. Soft computing methods, including Gene Expression Programming (GEP), Evolutionary Polynomial Regression (EPR), Multivariate Adaptive Regression Spline (MARS), and M5 Model Tree (MTM5) have been used to provide formulations for prediction of NVI. Soft computing techniques were fed nine input parameters: depth to water level, net recharge, aquifer environment, soil environment, topography, effect of unsaturated area, hydraulic conductivity, land use, and potential risk related to land use. After calculating the vulnerability by soft computing methods, the results showed that the EPR model with Correlation Coefficient (R) of 0.9999 and Root Mean Square Error (RMSE) = 0.2105 has the best performance in the testing stage in comparison with MARS (R = 0.9966 and RMSE = 2.408), M5MT (R = 0.9956 and RMSE = 2.988), and GEP (R = 0.9920 and RMSE = 3.491). Although the EPR and GEP models have more complex mathematical computations than other soft computing models, the MARS and MT model that have quadratic polynomial and multivariable linear structures respectively, can be considered as the best alternative. According to the MARS model, the vulnerability of the region is divided into two categories: very low vulnerability (73.06%) and low vulnerability (26.94%). Overall, the statistical results of soft computing techniques were indicative of effective formulations for evaluating the DRASTIC index.

Introduction: In the past few decades, nitrate contamination in water resources has become a global environmental problem often caused by urban and agricultural activities. In the past two decades, the capital of Afghanistan, Kabul has experienced rapid urbanization. This rapid urbanization has caused groundwater storage depletion and contamination of nitrate in the Kabul Plain. In the Kabul Plain, groundwater is the only source of drinking water for Kabul city residents. This study aims to determine the different sources of nitrate pollution, investigate the nitrogen transformation processes, and estimate the proportional contribution of various sources of nitrate pollution in groundwater of the Eastern Kabul Plain. Material and Methods: Eighteen groundwater samples were collected from the Eastern Kabul Plain aquifer in November 2020. In-situ parameters such as electrical conductivity (EC), pH, dissolved oxygen (DO), and temperature were measured in the sampling sites. The collected samples for analysis of nitrate and nitrate were transported to the Green Tech Laboratory in less than six hours, and the concentrations of mentioned ions were measured on the same day. The collected samples for analysis of major ions were transported to the Regional Water Organization Laboratory of Tehran, Iran. Nitrate samples for isotopic analysis were shipped to the UFZ laboratory in Germany, where isotopic measurements were carried out using the bacterial denitrifier method. The proportional contribution of nitrate sources was determined using the BSIMM model. Results and Discussion: Kabul city does not have a central sewage collection system, and sewage is disposed of mostly through septic and absorption wells. The groundwater nitrate concentration varied from 4 mg/L to 120.4 mg/L with an average value of 21 mg/L. The values ​​of δ15N-NO3̄ varied from 4.8 ‰ to 20.8 ‰ and the values ​​of δ18O-NO3̄ varied from 0.7 ‰ to 18.6 ‰. The composition diagram of δ18O-NO3̄ and δ15N-NO3̄ was employed to determine the main sources of nitrate in the aquifer. Considering that most of the samples are plotted on sewage and manure area, therefore, urban sewage plays a major role in increasing the concentration of nitrate in the groundwater of Eastern Kabul Plain. Since chloride is a conservative ion and is not affected by environmental factors, the diagram of NO3̄/Cl‾ molar ratio versus Cl‾ was used to identify potential sources of nitrate in the Kabul Plain aquifer. The plot indicated that urban sewage is the primary source of nitrate in the aquifer. The high concentration of dissolved oxygen and nitrate in the groundwater samples indicated the dominance of aerobic conditions in the aquifer and the absence of denitrification. Sewage plays a major role in nitrate pollution of groundwater. Therefore, the rapid urbanization and population growth in the Kabul Plain in the past two decades have caused groundwater nitrate pollution. The uncertainty in nitrate sources estimation has been quantitatively assessed using the uncertainty index (UI90). The results of this study display a relatively high uncertainty for the contribution of nitrate sources, particularly sewage and manure (0.49) and soil organic nitrogen (0.44). Conclusion: Sewage and manure, soil organic nitrogen, and chemical fertilizers are potential sources of nitrate in the Kabul Plain. The Bayesian stable isotope mixing model showed that sewage and manure (69.5%) are the main sources of nitrate pollution in the aquifer. The results indicated that nitrification is the main biogeochemical nitrogen transformation process in the Kabul Plain.

Groundwater nitrate contamination is a worldwide water environment problem with few phased summaries in this field. Here, 14 407 articles were selected from the Web of Science database for the years 1968—2022 to analyze the development trends and current hotspots in the field of groundwater nitrate contamination research with bibliometric visualization analysis software (VOS viewer). The results showed that: (1) The number of relevant publications has been exponentially increasing. The published journals are mainly related to environmental science and water resources, indicating an important role in this field. (2) The results from the publication institutions and funding institutions show that more than half of the total number of articles from the top ten publication institutions and funding institutions are from the United States and China. (3) The main issues in groundwater nitrate contamination research can be summarized as four subsets: source tracing, migration and transformation mechanisms, pollution remediation, and risk assessment. Among them, pollution remediation has the most keywords, demonstrating the importance of this research area. (4) From 1990 to 2014, the research hotspots in groundwater nitrate research were mainly focused on source tracing and migration and transformation mechanisms. Specifically, the main topic was the identification of nitrate pollution sources during the stage from 1990 to 1998, while the focus shifted to the methods for identifying nitrate pollution sources from 1999 to 2014, with isotopes and models being particularly effective. For the recent stage from 2015 to 2022, the research hotspots have shifted to risk assessment. The bibliometric analysis results in the field of groundwater nitrate pollution can provide some reference for the direction of this field.

Nitrate pollution and global warming are ubiquitous stressors likely to interact and affect the health and survival of wildlife, particularly aquatic ectotherms. Animal health is largely influenced by its microbiome (commensal/symbiotic microorganisms), which responds to such stressors. We used a crossed experimental design including three nitrate levels and five temperature regimes to investigate their interactive and individual effects on an aquatic ectotherm, the European common frog. We associated health biomarkers in larvae with changes in gut bacteria diversity and composition. Larvae experienced higher stress levels and lower body condition under high temperatures and nitrate exposure. Developmental rate increased with temperature but decreased with nitrate pollution. Alterations in bacteria composition but not diversity are likely to correlate with the observed outcomes in larvae health. Leucine degradation decreased at higher temperatures corroborating accelerated development, nitrate degradation increased with nitrate level corroborating reduced body condition and an increase in lysine biosynthesis may have helped larvae deal with the combined effects of both stressors. These results reinforce the importance of associating traditional health biomarkers with underlying microbiome changes. Therefore, we urge studies to investigate the effects of environmental stressors on microbiome composition and consequences for host health in a world threatened by biodiversity loss. [ABSTRACT FROM AUTHOR]

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Groundwater nitrate (NO3−) contamination is a global concern. The distribution patterns, enrichment mechanisms, and human health risks of NO3− contaminated groundwater were investigated using 144 groundwater samples collected from domestic and irrigation wells in the piedmonts of the North China Plain (Beijing and Shijiazhuang areas). The results showed that the groundwater was neutral to weakly alkaline, and 47% of the groundwater samples had NO3− concentrations exceeding 50 mg/L, a threshold proposed by world health organization to threaten infants up to 3 months. Groundwater NO3− concentrations were generally higher in the Beijing piedmont than in the Shijiazhuang piedmont and decreased with depth in both piedmonts. High-NO3− (> 50 mg/L) groundwater was distributed sporadically spatially and mainly was of Ca–Mg–HCO3 hydrochemical facies. Stable isotopes (D and 18O) compositions and NO3−/Cl− ratios indicated that NO3− accumulation in groundwater was primarily due to use of N-fertilizers under agricultural practices, and was associated with groundwater recharge sources such as septic tank leakage and re-infiltration of reclaimed irrigation water. Water quality evaluation showed that groundwater quality was highly dependent on NO3− concentration, with entropy-weighted water quality index values increasing linearly with increasing NO3− concentrations. The potential health risk of high-NO3− groundwater was the most serious for infants in both the piedmonts. Therefore, reducing NO3− input from sources and drinking water intake is recommended to minimize the human health risk. [ABSTRACT FROM AUTHOR]

In order to identify and effectively control the impact of NO3− pollution on human health, on the basis of investigation, sampling, analysis and testing, statistical analysis software (SPSS19), groundwater pollution analysis software, Nemera comprehensive index method, correlation analysis method and human health risk assessment model are applied for analysis and research. The results indicate that the groundwater in the study area is mainly Class II water, with overall good water quality. The main influencing factors for producing Class IV are NO3−, Fe, F− and SO42−. The use of agricultural fertilizers is the main source of NO3− exceeding standards in groundwater in this area. There are significant differences in the health hazards caused by NO3− pollution in groundwater among different populations, and infants and young children are more susceptible to nitrate pollution. The division of pollution areas and high-risk groups plays an important guiding role in preventing health risks. The new achievements will help people improve their awareness of risk prevention, caring for the environment, respecting nature and implementing precise policies, promoting society to step onto the track of scientific and healthy development. HIGHLIGHTS Scientific evaluation of groundwater quality was conducted and the main factors affecting water quality were analyzed.; Scientific evaluation was conducted on NO3− pollution in the research area and the main sources of NO3− were identified.; The significant differences in the health hazards of NO3− pollution were identified.; The research results have an important guiding role in preventing health risks.;

Though groundwater is one of the most significant natural water sources, its quality is deteriorating due to the anthropogenic pressures that poses health risks for people. In this study, potential health risk assessment for nitrate pollution in groundwater of Mersin Province was determined by commonly using health indices. Study findings indicated that the calculated Hazard Index (HI) values varied between 0.001 and 17.89 for the adults whilst the HI values ranging from 0.001 to 29.87 for the children. The HI values in the groundwater of Erdemli, Göksu and Anamur regions showed low chronic health risk for the adults and children (HI=1). However, the calculated health risk indices indicated significant health hazards for the children inhabited between Tarsus and Çeşmeli regions (HI=4.00) due to severe nitrate contamination originated from terrestrial sources. The findings of this study performed in the Mersin Province showed the sustainable management of groundwater policies is needed to reduce nitrate contamination and potential health hazards of the groundwater of studied and other regions in Türkiye. [ABSTRACT FROM AUTHOR]

The current research objective is to evaluate the appropriateness of groundwater for irrigation use and identify the sources of nitrate (NO3−) contamination in groundwater using stable isotopic signatures (N15 and O18). Groundwater samples (n = 50) from Southwest Delhi were analyzed pre- and post-monsoon for irrigation quality. The pH, electrical conductivity (EC), total dissolved solids (TDS), sodium adsorption ratio (SAR), sodium percentage (Na%), and other parameters were measured. EC exceeded 3000 μS/cm in 32% of pre-monsoon and 58% of post-monsoon samples. TDS categorized 32%, 52%, and 16% pre-monsoon and 68%, 28%, and 4% post-monsoon samples as non-saline, slightly saline, and moderately saline, respectively. SAR classified 72%, 20%, 6%, and 2% pre-monsoon and 62%, 12%, and 26% post-monsoon samples in low, medium, high, and very high sodium categories. Na% was unsuitable in 4% pre-monsoon and 4% post-monsoon samples. Kelly’s ratio showed 6% pre-monsoon and 20% post-monsoon samples unfit for use. The magnesium ratio indicated 34% pre-monsoon and 32% post-monsoon samples exceeding the limit. On Gibbs plots, 80% pre-monsoon and 67% post-monsoon samples indicated the dominance of evaporation and mineral dissolution processes influencing the resulting chemistry of irrigation water. Piper diagram suggested the majority of the samples belonged to mixed Ca-Mg type, Na-Cl type, and Ca–Mg–SO4–Cl, representing temporary hard water and permanent hard water type in both seasons. Additionally, the isotopic signature serves as additional confirmation that the primary contributors of NO3− in the groundwater within the study area are a combination of ammonium fertilizers, soil nitrogen, and manure/septic waste in both seasons. [ABSTRACT FROM AUTHOR]

Groundwater vulnerability assessment using DRASTIC is an important tool for groundwater pollution prevention and management. However, traditional DRASTIC methods are not suitable for accurate assessment of groundwater vulnerability in hilly and mountainous regions of southern China. The improved method in this paper retains the basic structure of DRASTIC, and obtains more accurate evaluation results by adding parameters and modifying parameter rating Scale and weights. Comparison of the modified DRASTIC-LY vulnerability map with the map of original DRASTIC-LY method revealed differences in 28.6% of the study area. The risk map shows that the very high vulnerability area decreased from 3.6% to 2.1%, while the high vulnerability area increased from 9.4% to 5.6%. Areas with low vulnerability increased by 10.7%, while areas with medium vulnerability increased by 4.9%. The areas with very high groundwater vulnerability are mainly distributed at the confluence of the Han River and Baojiang River, the areas with high groundwater vulnerability are mainly distributed in the southeast of Mian County, Nanzheng County, Chenggu County and Yang County, while the areas with low groundwater vulnerability are distributed in the northern part of the basin. The Pearson's correlation factor was 0.55 in the original DRASTIC model, 0.58 in the DRASTIC-LY method, and 0.65 in the modified DRASTIC-LY model, which indicated that the revised DRASTIC-LY model was more appropriate than that constructed by the original model. The vulnerability map of the DRASTIC-LY model can assist government planning and decision-making departments to facilitate water resource protection and water quality control. [ABSTRACT FROM AUTHOR]

Agricultural run‐off exposes recipient water bodies to nitrate (NO3−) pollution. Biological denitrification is a suitable method for removing NO3− in water resources that can be induced by the use of industrial organic liquid waste as an electron donor source. In light of this, batch and column laboratory experiments were performed to assess the potential of two industrial wine residues (lías and vínico) to induce biological denitrification of NO3− contaminated water from a constructed wetland and to evaluate the efficiency of these treatments using chemical and isotopic tools. In batch experiments (performed at a C/N ratio of 1.25), vínico was not efficient enough in removing N species, attenuating only 35% NO3− and was not used in column experiments. In similar experimental conditions, lías completely removed N species from water in both batch and column experiments. The calculated isotope fractionation (ε15NNO3 and ε18ONO3) was the same in both batch and column experiments biostimulated with lías and differed from those for vínico. The isotopic data confirmed that denitrification was the principal NO3− attenuation pathway in all the experiments. The isotopic fractionation can be later applied to field studies to quantify the efficiency of biologically enhanced denitrification. A numerical geochemical model that accounts for the changes in nitrate, nitrite concentration and isotopic composition due to the degradation of lías and vínico, including transport in the case of the column experiment, was performed to simulate the experimental results and can be up‐scaled in field treatments. Plain Language Summary: Groundwater nitrate pollution is a significant global concern resulting from excessive fertilizer use in agriculture. This pollution poses health risks to humans and ecosystems by contaminating drinking water supplies and aquatic ecosystems. Sustainable remediation of nitrate is necessary to safeguard human health and the environment. Successful field‐scale remediation requires laboratory feasibility studies to find the appropriate compounds to reduce nitrate (electron donors) and the best application measures to remove nitrate at a minimum cost. In our research, laboratory experiments were carried out using two industrial wine wastes as electron donors to evaluate their potential to remove nitrate from nitrate‐polluted water. Chemical, isotopic, and numerical modeling tools have been used to quantify the amount of nitrate removed. The results indicate that one product successfully removed nitrate and can be implemented in the field as a mitigation strategy, while the other was ineffective and cannot be used. The isotopic fractionation from the laboratory experiments and the numerical model would be subsequently applied in the field to quantify the efficiency of nitrate removal. Key Points: Wine industry residues induced nitrate attenuation in laboratory batch and column experimentsDenitrification efficiency varied with the wine residue type, showing ε15N between −16.5–−32.0‰ and ε18O between −12.1–−27.6‰A geochemical model describing the trends of the experimental results has been developed and can be used for field applications [ABSTRACT FROM AUTHOR]

Fluoride and nitrate enriched groundwater are potential threats to the safety of the groundwater supply that may cause significant effects on human health and public safety, especially in aggregated population areas and economic hubs. This study focuses on the high F– and NO3– concentration groundwater in Tongzhou District, Beijing, North China. A total of 36 groundwater samples were collected to analyze the hydrochemical characteristics, elucidate genetic mechanisms and evaluate the potential human health risks. The results of the analysis indicate: Firstly, most of the groundwater samples are characterized by Mg‐HCO3 and Na‐HCO3 with the pH ranging from 7.19 to 8.28 and TDS with a large variation across the range 471–2337 mg/L. The NO3– concentration in 38.89% groundwater samples and the F– concentration in 66.67% groundwater samples exceed the permissible limited value. Secondly, F– in groundwater originates predominantly from water‐rock interactions and the fluorite dissolution, which is also regulated by cation exchange, competitive adsorption of HCO3– and an alkaline environment. Thirdly, the effect of sewage disposal and agricultural activities have a significant effect on high NO3– concentration, while the high F– concentration is less influenced by anthropogenic activity. The alkaline environment favors nitrification, thus being conducive to the production of NO3–. Finally, the health risk assessment is evaluated for different population groups. The results indicate that high NO3– and F– concentration in groundwater would have the largest threat to children's health. The findings of this study could contribute to the provision of a scientific basis for groundwater supply policy formulation relating to public health in Tongzhou District. [ABSTRACT FROM AUTHOR]

Purpose: Human activities have increased the amount of reactive inorganic nitrogen (RIN) in the biosphere. Recently, the effect of RIN on lake ecosystems (e.g., stress to aquatic organisms) has received increasing attention, while only a few studies have investigated the effect of RIN on phosphorus (P) dynamics, which is considered a key element in eutrophication. This study aimed to test the effect of high RIN on sediment P release. Materials and methods: We conducted a two-month RIN-addition experiment in nine 150 L tanks with three treatments: controls (without N addition), nitrate addition treatments (+ NO3−), and ammonium-addition treatments (+ NH4+). NaNO3 and NH4Cl were added at a concentration of 10 mg L−1. Results and discussion: We found that the total phosphorus concentrations (TP) of the water were significantly higher in the + NO3− treatments than in the controls but lower than the TP in + NH4+ treatments. Meanwhile, labile P at the sediment‒water interface indicated minor and significant P release in the + NO3− and + NH4+ treatments, but P uptake in the control. Stimulated alkaline phosphatase activity was likely the dominant mechanism underlying the N-induced sediment P release. The magnitude of P release was higher in the + NH4+ treatment than in the + NO3− treatment, likely because nitrate enhances the oxidation of sediment, counteracting to some degree the P-releasing effect. Conclusions: The findings imply that high ammonium pollution may cause increased risks of eutrophication than the same amount of nitrate; this is important for decision-making to control internal P loading under the scenario of continuous N amplification. [ABSTRACT FROM AUTHOR]

Nitrate pollution in groundwater is a global environmental problem that poses risks to human health. We investigate the health risks of nitrate in rural drinking groundwater in Rucun Township and surrounding areas of Wutai County, and provide a basis for healthy drinking water. By using statistical analysis software (SPSS19) and hydrogeochemical analysis software (AqQA), a qualitative and quantitative evaluation of nitrate health risks was conducted among populations of different ages and genders through water sample collection, chemical analysis, and construction of a human health risk model (HHRA). Through research, it was found that the average concentration of nitrate in the study area is 43.99 mg/L. Groundwater is severely polluted by NO3−, and nitrate pollution areas are mainly concentrated in the main human activity areas, especially in the main agricultural production areas. The Quaternary loess layer, as a permeable layer, cannot prevent groundwater from being polluted by NO3−. Through evaluation, it is believed that there is a health risk of nitrate pollution in rural drinking groundwater in Rucun Township and surrounding areas. Health risk level: infants>children>adult females>adult males. The discovery and evaluation results can provide a basis for the prevention and control of nitrate pollution in groundwater. HIGHLIGHTS This study determined the distribution pattern of nitrate in rural drinking groundwater in Rucun Township and surrounding areas.; The chemical characteristics of groundwater in the study area were reflected and described through the Durov diagram.; HHRA for the first time in Rucun Township and surrounding areas was established to assess the level of health risks in the study area.;

Assessing groundwater geochemical formation processes and pollution circumstances is significant for sustainable watershed management. In the present study, 58 shallow groundwater samples were taken from the Dongwen River Basin (DRB) to comprehensively assess the hydrochemical sources, groundwater quality status, and potential risks of NO3– to human health. Based on the Box and Whisker plot, the cation's concentration followed the order of Ca2+ > Mg2+ > Na+ > K+, while anions' mean levels were HCO3− > SO42− > NO3− > Cl−. The NO3− level in groundwater samples fluctuated between 4.2 and 301.3 mg/L, with 67.2% of samples beyond the World Health Organization (WHO) criteria (50 mg/L) for drinking. The Piper diagram indicated the hydrochemical type of groundwater and surface water were characterized as Ca·Mg-HCO3 type. Combining ionic ratio analysis with principal component analysis (PCA) results, agricultural activities contributed a significant effect on groundwater NO3−, with soil nitrogen input and manure/sewage inputs also potential sources. However, geogenic processes (e.g., carbonates and evaporite dissolution/precipitation) controlled other ion compositions in the study area. The groundwater samples with higher NO3− values were mainly found in river valley regions with intense anthropogenic activities. The entropy weight water quality index (EWQI) model identified that the groundwater quality rank ranged from excellent (70.7%) and good (25.9%) to medium (3.4%). However, the hazard quotient (HQ) used in the human health risk assessment (HHRA) model showed that above 91.38% of groundwater samples have a NO3− non-carcinogenic health risk for infants, 84.48% for children, 82.76% for females, and 72.41% for males. The findings of this study could provide a scientific basis for the rational development and usage of groundwater resources as well as for the preservation of the inhabitants' health in DRB. [ABSTRACT FROM AUTHOR]

This study explores the impact of a novel approach on the levels of SWI (saltwater intrusion) and NO3− (nitrate) contamination. Some numerical simulations were conducted utilizing a coupled model that incorporates variably saturation and density, as well as convection diffusion reaction within a sandy coastal aquifer. We verified the reliability of the model for SWI based on comparison lab experiments and for chemical reactions based on a comparison of previous in situ observations. Cutoff walls and subsurface dams cannot simultaneously control SWI and reduce NO3− contamination. A novel approach that combines subsurface dams and permeable CH2O (organic carbon) walls (PC-Wall) is proposed. Subsurface dams are utilized to prevent SWI, while PC-Walls are employed to mitigate NO3− pollution. Results demonstrate that the construction of a PC-Wall with a concentration of 1.0 mM facilitated a transition from nitrification (Ni)-dominated to denitrification (Dn)-dominated. An increase in CH2O concentration to 1.0 mM caused a significant 1942.5 % rise in mDn (the mass of NO3− removed through Dn). Increment of the distance between the PC-Wall and the ocean from 35 to 45 m could result in a 103.7 % mDn increase and reduce mN (the compound mass of NO3− remaining in the aquifer) by 11.7 %. The study offers a detailed comprehension of the intricate hydrodynamics of SWI and NO3− pollution. In addition, it provides design guidance for engineering to mitigate contamination by NO3− and controlling SWI, thus fostering the management of groundwater quality. [ABSTRACT FROM AUTHOR]

This study presents the projected future evolution of water resource balance and nitrate pollution under various climate change scenarios and climatic models using a holistic approach. The study area is Almyros Basin and its aquifer system, located in Central Greece, Thessaly, Greece. Almyros Basin is a coastal agricultural basin and faces the exacerbation of water deficit and groundwater nitrate pollution. Using an Integrated Modeling System (IMS), which consists of the surface hydrology model (UTHBAL), the nitrate leachate model (REPIC, an R-ArcGIS-based EPIC model), the groundwater hydrology model (MODFLOW), and the nitrates' advection, dispersion, and transport model (MT3MDS), the projected values of the variables of water quantity and quality are simulated. Nineteen climatic models from the Med-CORDEX database were bias-corrected with the Quantile Empirical Mapping method and employed to capture the variability in the simulated surface and groundwater water balance and nitrate dynamics. The findings indicate that future precipitation, runoff, and groundwater recharge will decrease while temperature and potential evapotranspiration will increase. Climate change will lead to reduced nitrogen leaching, lower groundwater levels, and persistent nitrate pollution; however, it will be accompanied by high variability and uncertainty, as simulations of IMS under multiple climatic models indicate. [ABSTRACT FROM AUTHOR]

This study utilized the DRASTIC approach combined with GIS technology to assess groundwater vulnerability and contamination risks in a research area. The DRASTIC simulation generated a risk assessment map, categorizing locations based on vulnerability levels. The analysis revealed varying vulnerability levels, with areas of significant industrial activity and high population density exhibiting elevated nitrate levels in nearby wells. The model's outcomes were validated against field measurements of nitrate concentrations, demonstrating a high degree of consistency. The R-index technique was employed to assess sensitivity to nitrate contamination, identifying areas at greater risk. The study highlights the importance of considering hydrogeological characteristics and agricultural practices for groundwater protection and management. Overall, the DRASTIC approach proves valuable in assessing groundwater risks and informs decision-making for sustainable resource management. [ABSTRACT FROM AUTHOR]

Agricultural practices have a significant impact on stream water quality in rural landscapes; however, there is still little empirical evidence of how different types of cultivation alter the hydrochemistry of running water. Thus, the current study explored the spatial dynamics of selected ion concentrations and their land cover dependence in lowland agricultural catchments. From November 2021 to October 2022, water samples were collected from 30 sites located across small tributaries of the rivers Bzura, Pilica, and Radomka for chemical analysis of their NO3, NO2, NH4, Ca, Mg, K, Na, As, Ba, Sr, and V concentrations. The results indicated a clear spatial heterogeneity of water quality, related to lithology and dominant land cover evaluated with the CORINE Land Cover 2018 dataset. Overall, sites representing agricultural land promoted increased concentrations of major and trace elements, while those with pepper cultivation were additionally contaminated with NO3 and NO2. The correlation performance for nitrogen compounds was the highest for narrower buffer zones, which was not documented for major and trace elements, which were linked more strongly with land cover at larger scales. Such new insights into the water quality dynamics of lowland agricultural catchments, being a simultaneous reflection of lithology, agricultural practices, and several municipal impacts, have significant implications for appropriate water management in rural landscapes. [ABSTRACT FROM AUTHOR]

With the intensification of human activities, nitrate pollutants in groundwater are receiving increasing attention worldwide. Especially in the arid Nile Delta of Egypt, groundwater is one of the most valuable water resources in the region. Identifying the source of nitrate in groundwater with strong human disturbances is important to effective water resource management. This paper examined the stable isotopes (δ15N/δ18O-NO3 and δ2H/δ18O-H2O) and the hydrogeochemical parameters of the shallow groundwaters in the arid southeast of the Nile Delta to assess the potential sources and transformation processes of nitrate under severe urban and agricultural activities. The results revealed that the groundwaters were recharged by the Nile River. Meanwhile, the infiltration of irrigation water occurred in the west, while the mixing with the deep groundwater occurred in the east regions of the study area. The TDS, SO42−, NO3−, and Mn2+ concentrations of groundwaters (n = 55) exceeded the WHO permissible limit with 34.6%, 23.6%, 23.6%, and 65.5%, respectively. The NO3− concentrations in the shallow groundwaters ranged from 0.42 mg/L to 652 mg/L, and the higher levels were observed in the middle region of the study area where the unconfined condition prevailed. It extended to the deep groundwater and eastward of the study area in the groundwater flow direction. The δ15N-NO3 and δ18O-NO3 values suggested that the groundwater NO3− in the west and east regions of semi-confined condition were largely from the nitrification of soil organic nitrogen (SON) and chemical fertilizer (CF). In contrast, wastewater input (e.g., domestic sewage and unlined drains) and prevalent denitrification were identified in the middle region. The denitrification might be tightly coupled with the biogeochemical cycling of manganese. This study provides the first report on the groundwater NO3− dynamics in the Nile Delta, which generated valuable clues for effective water resource management in the arid region. [ABSTRACT FROM AUTHOR]

The continued input of nitrate (NO3) into groundwater is a global problem, mainly associated to excess fertilizer and improper disposal of human and livestock waste. Nitrate accumulation in oxic aquifers of semiarid areas makes these zones especially susceptible to pollution. Nitrate in Meoqui- Delicias aquifer, located in an important irrigation district in Chihuahua, Mexico, was quantified in 2021 in 63 drinking water wells. Samples collected were analyzed in laboratory and results were compared to 2003 and 2006 data available for those wells. Nitrate values varied from 0.7 to 23.2 mg/L and 22 % of the wells contained NO3 above drinking water guidelines (10 mg NO3-N/L). A low to moderate nitrate pollution index (NPI) and a slight NO3-N variation with time was observed for most wells. Values of NO3-N/Cl < 1.0 support an anthropogenic origin of nitrate. No association was found between NO3-N and well depth. The most susceptible areas to nitrate contamination were identified as those areas with high NO3-N and increasing concentration with time. The lack of a pattern of contamination suggested leakage of manure leachate at a few points as the most likely contamination source. The consistently high NO3-N content (>10 mg/L) in three deep wells constitutes a serious concern. DOI: https://doi.org/10.54167/tch.v18i1.1415

Increasing farmers' adoption of sustainable nitrogen management practices is crucial for improving water quality. Yet, research to date provides ambiguous results about the most important farmer-level drivers of adoption, leaving high levels of uncertainty as to how to design policy interventions that are effective in motivating adoption. Among others, farmers' engagement in outreach or educational events is considered a promising leverage point for policy measures. This paper applies a Bayesian belief network (BBN) approach to explore the importance of drivers thought to influence adoption, run policy experiments to test the efficacy of different engagement-related interventions on increasing adoption rates, and evaluate heterogeneity of the effect of the interventions across different practices and different types of farms. The underlying data comes from a survey carried out in 2018 among farmers in the Central Valley in California. The analyses identify farm characteristics and income consistently as the most important drivers of adoption across management practices. The effect of policy measures strongly differs according to the nitrogen management practice. Innovative farmers respond better to engagement-related policy measures than more traditional farmers. Farmers with small farms show more potential for increasing engagement through policy measures than farmers with larger farms. Bayesian belief networks, in contrast to linear analysis methods, always account for the complex structure of the farm system with interdependencies among the drivers and allow for explicit predictions in new situations and various kinds of heterogeneity analyses. A methodological development is made by introducing a new validation measure for BBNs used for prediction.

Because of the excessive use of nitrogen fertilizers, most of the groundwater resources are contaminated in the upstream of the Zayandehrud basin. This study set out to investigate the effect of different levels of water and nitrogen on yield, soil nitrogen, as well as water productivity indices of winter wheat and barley. The experimental treatments were of three nitrogen levels: no nitrogen fertilizer (N0), 50 kg N ha−1 (N1), and 150 kg N ha−1 (N2), as well as two irrigation levels containing deficit irrigation (I1) and full irrigation (I2). Each treatment was repeated three times. Wheat yield for I2 was 5,640 kg ha−1 and for I1 was 3,720 kg ha−1. The yield for barley was 5,620 and 3,850 kg ha−1 for I1 and I2, respectively. The irrigation water productivity (WPi) was increased by 55% for wheat and 83% for barley under deficit irrigation level. We recommend the use of 50 kg ha−1 (instead of 150 kg ha−1), knowing that it reduces the yield and water productivity for wheat by 11.7 and 10.9%, and by 14.5 and 12.6% for barley, respectively. In contrast, the soil nitrogen residual for wheat and barley was reduced by 56.6 and 66.1%, respectively, thus greatly reducing the risk of contamination of groundwater resources. HIGHLIGHTS NO3− concentration in water from 120 wells was measured.; Using high N fertilizer by farmers caused the increase in nitrate in groundwater.; Deficit irrigation is a good strategy to increase WP in a water-scarce arid area, for wheat and barley.; Using 50 kg N ha−1 instead of 150 kg N ha−1 is a good strategy to protect the environment; however, it may slightly reduce yields.;

This study retains the basic structure of DRASTIC model and obtains more specific evaluation results by adding land-use type and groundwater resource yield parameters, modifying the rating scale and weight of nine parameters. Comparison of the modified DRASTIC-LY vulnerability map with the map of the original DRASTIC-LY method revealed differences in 40.49% of the study area. The risk map shows that the very high vulnerability area decreased from 2.79 to 1.67%, while the high vulnerability area increased from 18.70 to 28.86%. Areas with low vulnerability increased by 10.15%, while areas with medium vulnerability decreased by 15.01%. The areas with very high groundwater vulnerability are mainly distributed in the Hanbin area on the north bank of the Han River, the areas with high are mainly concentrated on both sides of the Fujia River, while the areas with low are distributed in most areas in the west of the basin. The Pearson's correlation factor was 0.0583 in the original DRASTIC model, 0.1113 in the DRASTIC-LY method and 0.8291 in the modified DRASTIC-LY model, which indicated that the revised DRASTIC-LY model was more appropriate than the original model. The results can help the government with the protection of water resources. HIGHLIGHTS Improve the DRASTIC model.; Determine the weight, grade and category of each parameter.; Based on the sensitivity analysis and model validation results, construct the best model suitable for groundwater vulnerability assessment.; The results of this study will help government managers improve the composition of water use and strengthen the protection of vulnerable aquifers.;

In order to investigate the health risks of NO3− in rural drinking groundwater in Suihua, China and provide a basis for healthy drinking water, 40 sets of groundwater samples were collected in the Suihua area, and the average concentration of nitrate in the study area was 71.66 mg/L, statistical analysis software (SPSS19), Hydrogeochemical Analysis Software (AqQA) and groundwater pollution analysis software were used. Through water sample collection, chemical analysis and construction of human health risk model (HHRA), a qualitative and quantitative assessment of NO3− health risk was carried out for people of different ages and sexes, and it was concluded that there was NO3− pollution health risk in rural drinking groundwater in Suihua. Health risk level: infants > children > adult females > adult males. The evaluation provides a scientific basis for the prevention and control of NO3− pollution in groundwater and new ideas for preventing human health risks. HIGHLIGHTS The study identified the distribution pattern of nitrate in rural drinking groundwater in the Suihua area, providing a basis for preventing excessive use of fertilizers and pesticides.; The chemical characteristics of groundwater in the study area were reflected and described through the Durov plot.; A HHRA was first constructed in the Suihua area to evaluate the level of health risk in the study area.;

As the problem of eutrophication of water bodies and nitrate pollution of surface and groundwater is becoming more and more prominent, deep denitrification of wastewater can effectively reduce the amount of nitrate nitrogen (NO3−-N) discharged into natural water bodies. To solve this problem, in this research, the autotrophic denitrifying bacteria were incorporated in an autotrophic denitrification simulator equipped with magnetic pyrite to remove NO3−-N and total nitrogen (TN) from wastewater. The purified strains were inoculated into municipal sewage. When the ratio of magnetic pyrite to quartz sand was 1:1 and the particle size of the filler was 0.5–1 mm, the removal rate of NO3−-N and TN was optimized, at 93.52% and 83.22%, respectively. Sulphate (SO42−) concentrations will level off during stable system operation, and SO42− concentrations show a positive correlation with NO3−-N and TN removal. The 16s rDNA sequencing analysis of the screened sludge showed that the main phyla in the screened and purified sludge were Epsilonbacteraeota and Proteobacteria, with an abundance of 65.83% and 26.88%, and the final enriched products were dominated by Sulfurimonas and Thiobacillus, with an abundance of 64.91% and 9.32%, respectively. The results showed that autotrophic denitrifying bacteria could be screened and purified using thiosulfate as a substrate, and that the use of magneto pyrite as an electron donor reduced most of the NO3−-N to N2, while reducing the TN content. [ABSTRACT FROM AUTHOR]

The coastal plain aquifer down gradient of Wad Essaquia Elhamra (WEE), is the main source of groundwater in the arid region of Laayoune Essaquia El Hamra located in south of Morocco. The over-exploitation of this aquifer over the last decade for water supply, agriculture and industry led to deterioration of groundwater quality, including seawater intrusion. The objective of this study is to investigate the spatial variation of groundwater quality, and to assess the influence of sea water intrusion on the groundwater quality using hydro-chemical tools. Several measurement campaigns of physico-chemical parameters of the groundwater were performed, which shows a very high mineralization ratios versus chloride, confirming the double influence of mixing mechanisms of fresh and saline waters and the water-rock interactions. Computed seawater fraction for sampled water shows that the average mixing rate of seawater intrusion reached 10.5%, confirming the marine intrusion in the aquifer. The highest values were registered in coastal wells. In the upstream around Laayoune and the spreading area, nitrate concentrations exceed 50 mg/L which is the threshold set by the World Health Organization, revealing a high level of contamination by domestic sewage. The combination of ionic ratios and seawater fraction is a useful tool to assess marine intrusion. This study reveals that the phenomenon of marine intrusion is not the only process that dominates hydrochemistry of ground water. The high groundwater mineralization is also due to rockwater interaction associated with reverse ion exchange with clay material and anthropogenic pollutants. [ABSTRACT FROM AUTHOR]

The contamination of NO3− in groundwater is a global concern, requiring the identification of biogeochemical transformations and sources of nitrate (NO3−) to understand the different nitrogen (N) pathways. This is necessary for the regulation of dispersed pollution of groundwater caused by livestock and agricultural activities. Jinan, located in eastern China, serves as a suitable case study due to its reliance on karst groundwater as a water source and its significant population, industrial, and agricultural development, which pose a substantial risk of nitrogen pollutants in groundwater. Therefore, this study aims to investigate NO3− concentrations and isotopic compositions of N and oxygen in karst groundwater in Jinan City, Shandong province, eastern China, to determine the most significant sources and transformations of NO3−. Approximately 86% of the groundwater samples exceed the NO3−–N standard for drinking water proposed by the World Health Organization (WHO). Furthermore, chemical indicators (Cl−, HCO3−, and TDS) and the oxygen and nitrogen isotopic compositions of NO3− indicate that soil organic nitrogen, manure, and urban sewage are the main sources of NO3− in the groundwater. Isotopic analyses also suggest that various biogeochemical transformations, such as nitrification and volatilization, occur throughout the study area, with microbial nitrification being the dominant process in water resource areas with high NO3− concentrations. To reduce NO3− pollution in the Changqing–Xiaolipu water supply, several suggestions have been proposed. [ABSTRACT FROM AUTHOR]

Developing an accurate map to control groundwater pollution is becoming increasingly important to fulfill requirements of the Algerian water directives. Evaluating groundwater vulnerability to nitrate contamination in the eastern Mitidja aquifer has become crucial for water resource control and preservation. In this research, some of the commonly used ensemble methods namely Categorical Boosting, Adaptive Boosting and Random Forest were employed to model the spatial groundwater vulnerability to nitrate concentration based on the maximum acceptable concentration in drinking water according to the Algerian directives (50 mg/L). The study were carried out on the evaluation of different possible influencing parameters including depth to groundwater, permeability, rainfall, vadose zone, distance to river, drainage density, land use land cover, Normalized Difference Vegetation Index, slope, topographic wetness index and elevation. The proposed approach aims to understand and control the vulnerability and pollution process of the groundwater aquifers with the smallest available dataset to assess vulnerability predictive mapping. The best results based on the receiver operating characteristic and area under the curve (ROC-AUC) showed that the Categorical boosting indicated the highest accuracy of 94% then the adaptive boosting algorithm with 92%, and the Random forest algorithm with 89%. It revealed that climatic and hydrogeological factors are the key factors determining groundwater vulnerability to NO3 concentration in the eastern Mitidja. It is concluded that the risk of groundwater pollution covers a large area of the groundwater resources in the city of Algiers, Blida, and Boumerdas in northern Algeria. [ABSTRACT FROM AUTHOR]

The Chakari alluvial aquifer is the primary source of water for human, animal, and irrigation applications. In this study, the geochemistry of major ions and stable isotope ratios (δ2H–H2O, δ18O–H2O, δ15N–NO3̄, and δ18O–NO3̄) of groundwater and river water samples from the Chakari Plain were analyzed to better understand characteristics of nitrate. Herein, we employed nitrate isotopic ratios and BSIMM modeling to quantify the proportional contributions of major sources of nitrate pollution in the Chakari Plain. The cross-plot diagram of δ15N-NO3̄ against δ18O–NO3̄ suggests that manure and sewage are the main source of nitrate in the plain. Nitrification is the primary biogeochemical process, whereas denitrification did not have a significant influence on biogeochemical nitrogen dynamics in the plain. The results of this study revealed that the natural attenuation of nitrate in groundwater of Chakari aquifer is negligible. The BSIMM results indicate that nitrate originated mainly from sewage and manure (S&M, 75‰), followed by soil nitrogen (SN, 13‰), and chemical fertilizers (CF, 9.5‰). Large uncertainties were shown in the UI90 values for S&M (0.6) and SN (0.47), whereas moderate uncertainty was exhibited in the UI90 value for CF (0.29). The findings provide useful insights for decision makers to verify groundwater pollution and develop a sustainable groundwater management strategy. [ABSTRACT FROM AUTHOR]

Physical barrier has been proven to be one of the most effective measures to prevent and control seawater intrusion (SWI) in coastal areas. Mixed physical barrier (MPB), a new type of physical barrier, has been shown to have higher efficiency in SWI control. As with conventional subsurface dam and cutoff wall, the construction of MPB may lead to the accumulation of nitrate contaminants in coastal aquifers. We investigated the SWI control capacity and nitrate accumulation in the MPB using a numerical model of variable density flow coupling with reactive transport, and performed sensitivity analysis on the subsurface dam height, cutoff wall depth and opening spacing in the MPB. The differences in SWI control and nitrate accumulation between MPB and conventional subsurface dam and cutoff wall were compared to assess the applicability of different physical barrier. The numerical results show that the construction of MPB will increase the nitrate concentration and contaminated area in the aquifer. The prevention and control efficiency of MPB against SWI is positively correlated with the depth of the cutoff wall, reaching the highest efficiency at the minimum effective dam height, and the retreat distance of the saltwater wedge is positively correlated with the opening spacing. We found a non-monotonic relationship between the change in subsurface dam height and the extent of nitrate accumulation, with total nitrate mass and contaminated area increasing and then decreasing as the height of the subsurface dam increased. The degree of nitrate accumulation increased linearly with increasing the height of the cutoff wall and the opening spacing. Under certain conditions, MPB is 46–53% and 16–57% more efficient in preventing and controlling SWI than conventional subsurface dam and cutoff wall, respectively. However, MPB caused 14–27% and 2–12% more nitrate accumulation than subsurface dam and cutoff wall, respectively. The findings of this study are of great value for the protection of coastal groundwater resources and will help decision makers to select appropriate engineering measures and designs to reduce the accumulation of nitrate pollutants while improving the efficiency of SWI control. [ABSTRACT FROM AUTHOR]

Nitrate is a prominent pollutant in surface and groundwater bodies worldwide. Isotopes in nitrate provide a powerful approach for tracing nitrate sources and transformations in waters. Given that analytical techniques for determining isotopic compositions are generally time-consuming, laborious and expensive, alternative methods are warranted to supplement and enhance existing approaches. Hence, we developed a support vector regression (SVR) model and explored its feasibility to predict nitrogen isotopic composition of nitrate (δ15N-NO3-) in a rural-urban river system in Southeastern China. A total of 16 easily obtained hydro-chemical variables were measured in the wet season (September 2019) and dry season (January 2020) and used to develop the SVR prediction model. The grading method utilized ~75% (35) of the samples for model building while the remaining 11 samples assessed model performance. Principal component analysis (PCA) extracted 7 principal components for SVR model inputs as PCA reduces superfluous variables. We optimized tuning parameters in the SVR model using a grid search technique coupled with V-fold cross-validation. The optimized SVR model provided accurate δ15N-NO3- predictions with a determination coefficient (R2) of 0.88, Nash-Sutcliffe (NS) of 0.87, and mean square error (MSE) of 0.53‰ in the testing step, and performed much better than the corresponding multivariate linear regression model (R2 = 0.60, NS = 0.58 and MSE = 1.76‰) and general regression neural network model (R2 = 0.66, NS = 0.65 and MSE = 1.45‰). Overall, the SVR model provides a potential indirect method to predict environmental isotope values for water quality management that will complement and enhance the interpretation of direct measurements of δ15N-NO3-.

• Cd2+ and NO 3 − co-exposure caused exacerbated liver damage in flounders. • Adverse effects on inflammation, redox status and apoptosis were observed. • The combination of NO 3 − amplifies Cd2+-induced deleterious effects. Due to the discharge of industrial wastewater, urban domestic sewage, and intensive marine aquaculture tailwater, nitrate (NO 3 −) pollution has emerged as a significant issue in offshore waters. Nitrate pollution affects aquatic life and may interact with other pollutants, leading to comprehensive toxicity. Cadmium (Cd2+) is the most widespread metal contaminant, adversely affecting aquatic life in the coastal waters of China. Despite this, few studies have focused on the synergistic toxicity of NO 3 − and Cd2+ in marine organisms. This study conducted a 30-day exposure experiment on marine Japanese flounder (Paralichthys olivaceus) to explore the synergistic toxicity of NO 3 − and Cd2+. Our results demonstrated that the exposure to Cd2+ alone induced slight histopathological changes in the liver. However, malformations such as hepatic vacuolar degeneration and sinusoid dilatation were exacerbated under co-exposure. Moreover, co-exposure induced the downregulation of antioxidants and the upregulation of the product malonaldehyde (MDA) from lipid peroxidation, indicating potent oxidative stress in the liver. The increased mRNA expression of IL-8, TNF-α, and IL-1β , along with the decreased expression level of TGF-β , indicated a synergistic inflammatory response in the organisms. Furthermore, the co-exposure led to an abnormal expression of P53, caspase-3, caspase-9, Bcl-2, and Bax , and disturbed the apoptosis in the liver through TUNEL staining analysis. Overall, our results imply that co-exposure synergistically affects inflammation, redox status, and apoptosis in flounders. Therefore, the findings from this study provide valuable perspectives on the ecological risk assessment of marine teleosts co-exposure to NO 3 − and Cd2+. [Display omitted] [ABSTRACT FROM AUTHOR]

Nitrate (NO3−) is highly water-soluble and considered to be the main nitrogen pollutants leached from agricultural soils. Its presence in aquatic ecosystems is reported to cause various environmental and public health problems. Bioreactors containing microbes capable of transforming NO3− have been proposed as a means to remediate contaminated waters. Woodchip bioreactors (WBRs) are continuous flow, reactor systems located below or above ground. Below ground systems are comprised of a trench filled with woodchips, or other support matrices. The nitrate present in agricultural drainage wastewater passing through the bioreactor is converted to harmless dinitrogen gas (N2) via the action of several bacteria species. The WBR has been suggested as one of the most cost-effective NO3−-removing strategy among several edge-of-field practices, and has been shown to successfully remove NO3− in several field studies. NO3− removal in the WBR primarily occurs via the activity of denitrifying microorganisms via enzymatic reactions sequentially reducing NO3− to N2. While previous woodchip bioreactor studies have focused extensively on its engineering and hydrological aspects, relatively fewer studies have dealt with the microorganisms playing key roles in the technology. This review discusses NO3− pollution cases originating from intensive farming practices and N-cycling microbial metabolisms which is one biological solution to remove NO3− from agricultural wastewater. Moreover, here we review the current knowledge on the physicochemical and operational factors affecting microbial metabolisms resulting in removal of NO3− in WBR, and perspectives to enhance WBR performance in the future. [ABSTRACT FROM AUTHOR]

In order to investigate the main factors that caused the Nitrate increasement in Huixian Wetland, 15N-NO3 and 18O-NO3 analysis were conducted. SIAR model was applied to quantitatively test the contribution proportions of kinds of pollutants. Health risk assessment (HRA) was taken to study ten heavy metals of 96 groups samples in the four main waters in Huixian Wetland: Surface River, Subterranean Stream, Blue Hole and Well Water. The main sources of Nitrate were domestic sewage and animal feces, chemical fertilizer, and soil, with the contribution proportions of 39.1%, 32.2%, and 28.5%, respectively. The heavy metals concentration order is that of Mn > Al > Cr > Zn > As > Pb > Cu > Fe > Cd > Hg. The HRA showed that the average annual total health risks-through drinking and skin penetration-order was: Well Water > Blue Hole > Subterranean Stream > Surface River. The drinking water from Well and Blue Hole can cause the cancer risks in children of 7.08 × 10−5 a−1 and 7.01 × 10−5 a−1, respectively. Both were higher than the recommendation standard (5.0 × 10−5 a−1) from ICRP. As the main element contributed to the health risk of adults and children, the Cr in all the four waters were also over the standard (1 × 10−6 a−1) recommended by the Swedish Environmenta1 Protection Agency and the Dutch Ministry of Construction and Environment and the British Royal Society. The health risk levels of non-carcinogenic metals were 1 × 10−16–1 × 10−10, which were 5–11 order of magnitude lower than the acceptable level.