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For the Hessian river basins, an area-differentiated modeling of the nitrogen input to the groundwater and surface waters was carried out for six diffuse input pathways and six point source input pathways on the basis of the geodata available at the state level. In this context, extensive plausibility checks of the model results were carried out using the data from several official monitoring networks at the state level. These include the comparison of modeled runoff components and input pathways for nitrogen using the data from the network of discharge monitoring stations. For the validation of the modeled nitrate concentrations in the leachate, the data from groundwater monitoring wells for controlling the chemical status of groundwater were used. The validation of the modeled nitrate inputs to the groundwater and denitrification in the groundwater was carried out using the data from a special monitoring network of groundwater monitoring wells that include N2/Ar measurements. The data from the Surface Water Quality Monitoring Network were used to verify the plausibility of the modeled total N inputs to the surface waters from diffuse sources and from point sources. All of the model results evaluated by the plausibility checks prove that the nitrate pollution situation in Hesse is adequately represented by the model. This is a prerequisite for accepting the model results at the state level as a basis for developing and implementing regionally appropriate mitigation measures. The Hessian State Agency for Nature Conservation, Environment and Geology uses the model results in the broader context of the work on implementing the EU Water Framework Directive and the EU Nitrate Directive. [ABSTRACT FROM AUTHOR]

In recent years, groundwater vulnerability assessment has become a crucial step in effectively protecting groundwater resources against increasing groundwater pollution in recent years. Sustainable effectual management of groundwater sources in terms of quality has become a critical factor in the development of unplanned urbanization areas, especially in regions with intensive agricultural and industrial activities in the land use/land cover (LULC) models. In this study, the GIS-based DRASTIC model was used by modified to estimate the groundwater vulnerability of porous aquifers to nitrate and total dissolved solids (TDS). The DRASTIC and the modified DRASTIC models generate four different groundwater vulnerability zones: high (33.6, 37.8%), moderate (45.9, 42.3%), low (18.7, 18.3%), and very low (1.8,1.6%). DRASTIC_LULC index map provides four different vulnerability zones: low, moderate, high, and very high, covering 0.1%, 7.6%, 83.6%, and 8.7% of the Erbil Central Sub-Basin, respectively. The most important hydrogeological factors determining the DRASTIC vulnerability obtained from sensitivity analyses are depth to the water table and impact of vadose zone parameters with average effective weight values of 23.7% and 22.6%. For validating the DRASTIC_LULC model, the water quality parameters, nitrate and TDS, have been used with an accuracy of 68% and 79%, which indicates that the validation accuracy for this model is quite high. Maps obtained as a result of this study can be used to create a baseline map for the sustainable management of groundwater quality in vulnerable areas of the Erbil Central Sub-Basin and its planning. [ABSTRACT FROM AUTHOR]

A risk analysis framework is proposed for the optimum remediation of a contaminated aquifer under hydrogeological uncertainty. The limited information and the spatial variation of hydraulic conductivity in a real-world large-scale aquifer create uncertain conditions for decision-making when remediation schemes ought to be accompanied by the minimum possibility of failure. The primary concern is focused on safeguarding public health when groundwater is used for urban drinking purposes from a contaminated aquifer. The proposed framework is based on the conjunctive use of stochastic simulation–optimization modelling followed up by a risk analysis application on remediation trade-offs. The framework includes three main steps/procedures: (i) the model formulation of multiple realizations of groundwater flow and contaminant transport, (ii) the optimal positioning and operation of the clean-up wells determined by the method of stochastic optimization, and (iii) the risk analysis of the optimum remediation strategies through a proposed decision model, so as the one with the minimum cost and risk of failure is chosen as the most appropriate. The proposed framework is tested for two scenarios of nitrogen fertilizer application in the cultivated areas. The strategic target is the groundwater nitrate concentration minimization in an area where exceedances of nitrate concentrations have been observed and water supply wells have been operating for the last twenty years satisfying domestic needs. The results demonstrate that, when decision-making is under hydrogeological uncertainty, the combined use of stochastic optimization and risk-based decision analysis can commend the remediation strategy with the minimum cost and the highest possibility of success. [ABSTRACT FROM AUTHOR]

In this study, the hydrochemical characteristics of groundwater were assessed based on 64 shallow groundwater samples collected in the Guanzhong Basin, China, and the health risk of nitrate (NO3-) in drinking water was assessed. In addition, the spatial distributions of major water quality indicators were investigated, while bivariate plots, saturation index, and stable isotopes were used to reveal the processes controlling groundwater hydrogeochemistry. The results showed that groundwater in the study area was mostly fresh water. However, the maximum and average NO3– concentrations were 397.0 and 92.9 mg/L, respectively, indicating serious groundwater NO3– pollution. The percolation of contaminated river water exhibited considerable impacts on groundwater quality. Carbonate dissolution was the major process controlling the hydrochemical characteristics of groundwater, while human activities were responsible for the high concentrations of groundwater pollutants, especially NO3–. Evaporation fraction of groundwater in the study area revealed by stable hydrogen and oxygen isotopes ranged from 4 to 13% and 4 to 11%, respectively. High non-carcinogenic health risks of NO3– to adults and children were observed in about 46.88 and 75% of the collected groundwater samples, respectively. The risk value ranges were 0-6.00 and 0-14.06, with average values of 1.36 and 3.19, for adults and children, respectively. [ABSTRACT FROM AUTHOR]

Featured Application: Nitrate pollution in waterbodies is a topic of environmental and health concern. Being aware of the wide range of technologies available is a challenge of real interest that will facilitate the selection of an eco-friendly and affordable water treatment technology in terms of equipment investment and energy costs. Nitrate (NO3−) pollution of surface and groundwater bodies is a global problem of increasing concern, which has stimulated significant research interest. Nitrogen is crucial for life as a macronutrient for living organisms on Earth, but the global nitrogen cycle has been seriously altered by intensification of human activities, leading to eutrophication and hypoxic conditions of aquatic ecosystems. Due to nitrogen overfertilization, intensive agricultural practices generate huge nitrate fluxes that inadvertently deteriorate water quality. Different industrial processes also contribute to NO3− pollution in the environment. There are multiple technologies capable of achieving effective denitrification of waterbodies to ensure safe NO3− levels. Either separation-based or transformation-based denitrification technologies must address the challenges of by-product generation, increased energy demand, and reduced environmental footprint. This paper highlights the most used approaches, along with some promising alternatives for remediation of nitrate-polluted waters. [ABSTRACT FROM AUTHOR]

Nitrate in drinking water may cause serious health problems for consumers. Agricultural activities are known to be the main source of groundwater nitrate contaminating rural domestic and urban public water supply wells in farming regions. Management practices have been proposed to reduce the amount of nitrate in groundwater, including improved nutrient management practices and "pump and fertilize" with nitrate-affected irrigation wells. Here, we evaluate the feasibility and long-term impacts of agricultural managed aquifer recharge (Ag-MAR) in the source area of public water supply wells. A numerical model of nitrate fate and transport was developed for the Modesto basin, part of California's Central Valley aquifer system. The basin is representative of semi-arid agricultural regions around the world with a diversity of crop types, overlying an unconsolidated sedimentary aquifer system. A local public supply well in an economically disadvantaged community surrounded by farmland was the focus of this study. Model scenarios implemented include business as usual, alternative low-impact crops, and Ag-MAR in the source area of the public supply well. Alternative nutrient management and recharge practices act as remediation tools in the area between farmland and the public supply well. Improved agricultural source area management practices are shown to be an effective tool to maintain or even enhance groundwater quality in the targeted supply well while remediating ambient groundwater. Best results are obtained when lowering nitrate load while also increasing recharge in the source area simultaneously. This scenario reduced nitrate in the supply well's drinking water by 80% relative to the business as usual scenario. It also remediated ambient groundwater used by domestic wells between the source area farmlands and the supply well and showed 60% more reduction of nitrate after 60 years of application. Increasing recharge led to shorter initial response time (five years) and showed the most sustainable impact. Our analysis further suggests that Ag-MAR in a highly discontinuous, wide-spread pattern leads to slow water quality response and may not yield sufficient water quality improvements.

Abstract Groundwater (GW) is an important source of freshwater in arid and semiarid areas. Some important industrial activities, such as coal mining, also consume GW. There have been few studies evaluating GW quality in the Selian coal mining area of Inner Mongolia. This study aimed to identify the hydrochemical phases and the sources of main ions in the GW of the Selian coal mining area. Water quality analysis was performed on 20 shallow GW samples collected from the study area. Statistical correlation analysis was performed on these water quality data. The quality of irrigation water was evaluated based on water quality indices such as the sodium absorption rate and sodium percentage. The risk of nitrate pollution in the study area to human health was evaluated by GW nitrate content. The results show that the dominant GW chemistry types in the study area are the mixed and Ca–HCO3 types. Correlation analysis indicates that rock weathering and leaching are the main natural drivers of GW hydrochemistry in this area. The irrigation risk analysis shows that GW in this area can be used for irrigation, although some caution is needed. The human health risk assessment shows that GW nitrate pollution poses more risk to children than to adults by a factor of 1.168. It is recommended that centralized treatment of drinking water is the optimal approach to managing this risk. The results of this study can act as a reference for the rational use of GW and for control of nitrate pollution in this area.

A comprehensive hydrogeological report was conducted to determine the origin, occurrence and processes affecting nitrogen in a Mediterranean coastal aquifer-lagoon system. Water levels, hydrochemical and isotopic data was gathered during a 4-year period in the La Pletera salt marsh area (NE Spain). They were collected from the alluvial aquifer, two natural lagoons and four other permanent lagoons excavated during a restoration process (in 2002 and 2016), two watercourses (the Ter River and the Ter Vell artificial channel), 21 wells (considering six of them for groundwater sampling) and the Mediterranean Sea. Potentiometric surveys were carried out seasonally, however twelve-monthly campaigns (from November 2014 to October 2015), and nine seasonal campaigns (from January 2016 to January 2018) were conducted for hydrochemical and environmental isotopes analyses. The evolution of the water table was analysed for each well, and potentiometric maps were plotted to determine the relationship between the aquifer and the lagoons, sea, watercourses, and groundwater flow. Hydrochemical data included physicochemical data measured in situ (temperature, pH, Eh, dissolved oxygen, and electrical conductivity), major and minor ions (HCO3−, CO32−, Cl−, SO42−, F−, Br−, Ca2+, Mg2+, Na+, and K+), and nutrients (NO2−, NO3−, NH4+, Total Nitrogen (TN), PO43−, and Total Phosphorus (TP)). Environmental isotopes included stable water isotopes (δ18O and δD), nitrate (δ15NNO3 and δ18ONO3) and sulphate isotopes (δ34SSO4 and δ18OSO4). Water isotopes were analysed for all campaigns, however, nitrate and sulphate isotopes water samples were only analysed in some particular surveys (November and December 2014; January, April, June, July and August 2015). Additionally, two more surveys for sulphate isotopes were conducted in April and October of 2016. The data generated through this research may be used as a starting point to analyse the evolution of these recently restored lagoons, and their future responses to global change. In addition, this dataset may be used to model the hydrological and hydrochemical behaviour of the aquifer.

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Nitrate pollution of groundwater has become a global concern as it can affect drinking water quality and human health. In this paper, an extensive hydrochemical investigation was performed to assess the spatial distribution, source identification, and health risk of groundwater nitrate pollution in the Subei Lake basin. The prevalent pollutant, nitrate (NO3−), was identified based on descriptive statistical method and box plots, and most of the other parameters of groundwater samples met water standards and can be used for drinking purpose. The results showed that nearly 23.53% of groundwater samples displays the NO3− concentrations higher than the limit of 50 mg/L recommended by the World Health Organization, and the highest nitrate content (199 mg/L) is mainly distributed around the Mukai Lake. Piper triangle diagram demonstrated that the dominated anions of hydrochemical types exhibit a gradual evolving trend from HCO3− to SO42− and Cl− with increasing nitrate concentration. The correspondence analysis suggested that agricultural activities are identified as the most possible source of nitrate contamination, while the higher content of other parameters in individual groundwater samples may be controlled by natural factors. The impacts of pollutant NO3− on human health were quantified using human health risk assessment method, and results showed that the order of non-carcinogenic health risk values through drinking water intake is Infants>Children>Adult males>Adult females, and 65%, 53%, 41%, and 35% of samples exceed the acceptable risk level (hazard quotient=1), respectively. The main findings obtained from this study can provide valuable insight on drinking water safety and groundwater pollution prevention. [ABSTRACT FROM AUTHOR]

Nitrate pollution has become a serious environmental concern all over the world including in China due to the mismanagement of water resources and human activities. Agricultural runoff and industrial and nuclear waste are among the major sources of nitrate pollution. Consuming nitrate-rich water can cause many chronic diseases including digestive problems, which can lead to many types of cancer and other serious health issues. Denitrification is the natural process for nitrate reduction under aerobic conditions, but it cannot handle an excess of nitrate, so several methods have been adopted for nitrate removal, i.e., biological, chemical, physicochemical, and electrochemical reduction removal. Among all, electrochemical reduction removal is a cost-effective and environmental-friendly process. To obtain the maximal elimination efficiency ideal conditions of current intensity, pH, plate distance, initial nitrate concentration, and type of electrolyte solution should be studied for effective nitrate removal. Electrochemical reduction removal of nitrate involves the transfer of electrons and hydrogenation. Besides an efficient nitrate removal process, electrochemical reduction removal has some drawbacks like sludge formation, low selectivity for nitrogen, and production of brine that limit its long-term implementation. This review focused on nitrate pollution, previous nitrate removal strategies, and essential principles for understanding the mechanism of electrochemical reduction removal and controlling the products of the reaction. [ABSTRACT FROM AUTHOR]

Abstract Monitoring groundwater quality and analyzing geochemical processes are very crucial in dry environments, especially in areas with intense agriculture and inadequate irrigation management systems. A total of forty-one groundwater samples were collected from the study area and analyzed for major ions chemistry. The results of the geochemical analyses are used to investigate the geochemical processes and make groundwater assessments. The hydrogeochemical characteristics of the groundwater samples revealed a highly mineralized Na+–Cl− water type, implying that the majority of the samples are chemically unfit for human consumption. Based on the water quality parameters analyzed for the groundwater samples collected in this study, such as sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium hazard (MH), permeability index (PI), and Kelley's ratio (KR), the suitability of groundwater samples for irrigation purposes is good to moderately good. Also they may reflect some alkaline hazard threats to the soil as indicated by the SSP and KR. The salinity hazard is recognized as high and expected to increase with the expansion of irrigation; hence, special salinity control management for groundwater in the study area is required. Nitrate is widely recognized as a contaminant in the study area. The nitrate concentrations range from 0.1 to 256.8 mg/L, with more than 30% of the samples exceeding the safe drinking water limit of 50 mg/L. The main concern is that the average nitrate concentration will likely continue to increase in the groundwater of the study area. Groundwater monitoring, in terms of both quality and quantity, is essential for sustainable groundwater management.

The surface water - groundwater interactions in a small anthropically affected mountain watershed (Salsipuedes River) in the Sierras Pampeanas (central Argentina) were analyzed and quantified by means of 222Rn mass balance modeling, and its implications in hydrochemistry and water quality were examined. Surface waters, springs and groundwater were sampled during the 2021–2022 hydrological year, and the major dissolved composition was determined. The studied waters are alkaline, showing an evolution from medium mineralized (1.5 < ∑+ < 3 meq L−1) to mineralized type (3 < ∑+ < 6 meq L−1) downstream. In general, waters are of the bicarbonate - calcium type with no spatial or seasonal variations. This composition is mainly controlled by silicates weathering. 222Rn modeling indicates that near the headwaters the Salsipuedes River recharges the aquifer, losing 1.2% and 2.4% of its discharge during the dry and wet seasons, respectively. Downstream, the system changes its hydrological behavior and the river acts as a gaining stream; i.e, it receives groundwater inflow. The magnitude of this inflow varies seasonally, being greater in the wet season (1.5–2.2% of the total flow) than in the dry season (less than 0.25%) due to a rise in the water table level as a result of direct recharge of the phreatic aquifer. Anthropic influence is noticeable in nitrate and chloride concentrations, which are derived from domestic wastes and septic tanks. The highest concentrations of these ions in surface waters are found in the urbanized area, where the river stretch corresponds to a gaining stream, reflecting that even small amounts of groundwater inputs can alter the chemical composition of streams. A temporal analysis also showed a variable response of the system to the increasing anthropic pressure and climatic events such as ENSO, which affect not only water availability but also its quality, highlighting the vulnerability of small mountain watersheds. • Hydrochemistry and water quality were examined in an urbanized mountain watershed. • Surface water - groundwater interactions were quantified using a222Rn mass balance. • Even slight groundwater inputs alter the chemical composition of the stream. • A temporal analysis showed a variable response to the increasing anthropic pressure. • Climatic events like ENSO affect water availability and quality. [ABSTRACT FROM AUTHOR]

Ulva lactuca is a versatile intertidal and blooming green macroalga with a global distribution, undergoing a lifecycle that consists of critical phases. The effects of surface physical properties and elevated nitrate concentrations on the growth of Ulva spores were evaluated using ATR-FTIR analysis, water contact angle measurements and fluorescence microscopy. The weathering process conducted with seawater led to the emergence of new functional groups such as C O, CH 3 (rock), and CH, alongside a reduction in existing groups on the polymers, as evidenced by ATR-FTIR. This resulted in a progressive increase in surface wettability, with contact angles decreasing on all substrates, particularly in PP which showed the highest contact angle, dropping from 94.8° ± 0.02 to 70.5° ± 0.03. It reflected on the rate of attachment of spores on each plastic. Moreover, the nitrate concentration collectively controlled the density and development of all substrates. Growth rate after 5 days of attachment, most notably on day 10 (N3 60 μM NO 3 : length 36.4 ± 2.495 µm) and day 20 (N3 60 μM NO 3 : length 181 ± 8.335 µm) increased drastically. Meanwhile, the density was altered in a decreased way throughout the experiment based on substrates. Spore density demonstrated a complex interaction among nitrate and plastics relative to length at all the periods of analysis. These findings can contribute to understanding the role of plastics and Ulva in the ecological phenomena. Consequently, increasing amounts of plastic debris and excessive load of nitrate effluents in marine environments could lead to more frequent algal blooms. [Display omitted] • Seawater-induced weathering on plastics caused a notable decrease in the contact angle. • Nitrate concentration dominated substrate properties during at initial stages. • PP and PVC were identified as potential carriers of Ulva spores • Increase proliferation risk with plastics at a nitrate concentration of 60 μM. [ABSTRACT FROM AUTHOR]

Reservoir dams alter the nutrient composition and biogeochemical cycle. Thus, dual isotopes of δ18O-NO3− and δ15N-NO−3 and geochemical signatures were employed to study the NO3− pollution and chemical weathering in the Three Gorges Reservoir (TGR), China. This study found that the TGR dam alters the δ15N-NO3− composition and is enriched in the recharge period. Values of δ15N-NO3− varied from 4.5 to 12.9‰ with an average of 9.8‰ in the recharge period, while discharge period δ15N-NO3− ranged from 3.2 to 12.5‰, with an average of 9.3‰. δ18O-NO3− varies (1.2–11.3‰) with an average of 6.5‰ and (2.4–12.4‰) with an average of 7.5‰, in the recharge and discharge periods, respectively. Stable isotopic values sharply decreased from upstream to downstream, indicating the damming effects. δ18O-NO3− and δ15N NO3− confirm that sewage effluents, nitrification of soil organic material, and NH4+ fertilizers were the primary sources of NO3− in the reservoir. Carbonate weathering mainly provides ions to the reservoir. HCO3− + SO42− and Ca2+ + Mg2+ represent 90% of major ions in the TGR. Downstream sampling sites showed low solute concentration during the recharge period, indicating the dam effect on solute concentration. Ca–Mg–Cl−, Ca–HCO3− and Ca–Cl− were the main water types in the TGR. The average percentage of solutes contribution revealed the carbonate weathering, evaporites dissolution, silicate weathering, and atmospheric input were 51.9%, 41%, 7.8%, and 1.7% for the recharge period. In contrast, the discharge period contributed 66.4%, 29.2%, 10%, and 4.3%, respectively. TGR water is moderately suitable for irrigation, and hardness is high in drinking water. This study provides new insight into the dual isotopic approach and geochemical signatures to interpret the NO3− cycle and chemical weathering process under dam effects in the TGR. However, this isotopic application has some limitations in source identification, isotope fractionation, and transformation mechanisms of nitrate. Thus, further studies need to be done on these topics for a better undestanding. [ABSTRACT FROM AUTHOR]

The increase in intensive agriculture and livestock farms is causing serious social and environmental impacts in a large part of the Spanish territory. The socioecological systems on which the agri-food industry depends need an effective legal response aimed at managing risks and providing a material response to the model of exploitation of so-called "extra-human nature" (water, soil and animals), aimed, in most cases, at generating large-scale "cheap food" for international markets to the detriment of local socio-ecosystems such as the Mar Menor. The lack of effective application of the legal system and of the principles of prevention, precaution and non-regression of environmental regulations (e.g. codes of good agricultural practice and declaration of areas vulnerable to nitrate pollution), puts the territory at risk and contributes directly to the deterioration and mistreatment of the environment due, among other things, to the pollution of bodies of water (especially groundwater, coastal and transitional waters), as a result of constant non-compliance with regulations on nitrate pollution from agricultural and livestock sources. [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. [ABSTRACT FROM AUTHOR]

Evolving groundwater vulnerability from DRASTIC to modified DRASTIC methods helps choose the most accurate areas that are most delicate toward pollution. This study aims to modify DRASTIC with land use and water quality index for groundwater vulnerability assessment in the Halabja-Khurmal sub-basin, NE/Iraq. The Halabja-Khurmal sub-basin groundwater vulnerability index is calculated from nine hydrogeological parameters by the overlay weighting method. As a result, 1.3% of the total area has a very high vulnerability value and 46.1% with high vulnerability. The regions with high groundwater vulnerability have a high-water table and groundwater recharge. Nitrate concentration was used to validate the result, and the Pearson correlation and recession analysis between the modified DRASTIC index and nitrate concentration depicted a strong relation with 0.76 and 0.7, respectively. [ABSTRACT FROM AUTHOR]

The study assesses the extent of nitrate pollution in the Densu Basin, because of its predominance in agriculture and urbanized vicinities, by employing robust techniques to estimate both the natural background and human-induced concentrations. Statistical methods used are the pre-selection method, graphical approach (probability plot), non-parametric approach (kernel density estimation), and parametric approach (Gaussian mixture model). The study shows that the Gaussian mixture model is robust enough in determining the spectral distribution and clustering of the NO3-N concentration in the basin. It estimated the natural background and human-induced concentration at 1.7 ± 1.3 and 9.8 ± 5.6 mg/L, respectively. The results show that the natural background concentration in the basin is more dominant and, hence, conducive for drinking. We found a 26% contribution from anthropogenic sources that had leaked into the natural groundwaters of the Basin. The data suggest multiple sources of NO3-N concentration in the groundwater. [ABSTRACT FROM AUTHOR]

Groundwater (GW) is an important source of freshwater in arid and semiarid areas. Some important industrial activities, such as coal mining, also consume GW. There have been few studies evaluating GW quality in the Selian coal mining area of Inner Mongolia. This study aimed to identify the hydrochemical phases and the sources of main ions in the GW of the Selian coal mining area. Water quality analysis was performed on 20 shallow GW samples collected from the study area. Statistical correlation analysis was performed on these water quality data. The quality of irrigation water was evaluated based on water quality indices such as the sodium absorption rate and sodium percentage. The risk of nitrate pollution in the study area to human health was evaluated by GW nitrate content. The results show that the dominant GW chemistry types in the study area are the mixed and Ca–HCO3 types. Correlation analysis indicates that rock weathering and leaching are the main natural drivers of GW hydrochemistry in this area. The irrigation risk analysis shows that GW in this area can be used for irrigation, although some caution is needed. The human health risk assessment shows that GW nitrate pollution poses more risk to children than to adults by a factor of 1.168. It is recommended that centralized treatment of drinking water is the optimal approach to managing this risk. The results of this study can act as a reference for the rational use of GW and for control of nitrate pollution in this area. [ABSTRACT FROM AUTHOR]

The groundwater resource is crucial to the urbanization and industrialization in the Guangdong coastal area; the rapid development of Daya Bay has presented a challenge for the management of the groundwater quantity and quality. Therefore, a novel approach to hydrochemical analysis, which, combined with the health risk model and the water quality index (WQI), was used to explain the hydrochemistry characteristics and risks to human health of groundwater in the Guangdong coastal areas in addition to investigating the factors controlling groundwater quality. The results showed that the average concentration of total dissolved solids (TDS) in groundwater was 1935.26 mg/L and the quality of water was weakly alkaline. The dominant hydrochemical types of groundwater were identified to be Mg-HCO3 and Na-Cl·HCO3. The main factor influencing the hydrochemical composition was rock weathering, while the result of principal component analysis (PCA) shows seawater intrusion and anthropogenic inputs also have an effect on the water quality. The conclusions of the water quality assessment indicated that most of the groundwater samples were acceptable for drinking. However, both WQI and the non-carcinogenic hazard quotient (HQ) values indicated unacceptable risks in any area of Maoming, Zhanjiang and Shantou, and, according to the hazard index (HI) value, children in the study area are at more danger to health risks than adults. It is suggested that both groundwater salinization and nitrate pollution should be paid attention to when improving groundwater quality and exploring the sustainable utilization of groundwater resources. [ABSTRACT FROM AUTHOR]

The Ingul megablock of the Ukrainian Shield contains a number of endogenous deposits of the sodium-uranium formation, which have been developed for more than 55-60 years. With the exception of the Kirovograd uranium ore region, the deposits of which are controlled by discontinuities in the fault zone of the same name, the Vatutinske and Novokostiantynivske ore fields occupy positions within the Novoukrainsky granite-gneiss dome and in close proximity to the later geostructural formation, the Korsun-Novomyrgorod pluton. Paying attention to the high degree of saturation of the Ingul megablock with endogenous uranium deposits, it is emphasized that they also contain an increased content of thorium minerals and, in combination with uranium, they produce ascending gas flows of radon. Therefore, studies of the dynamics of the upper horizons of the lithosphere and the closely related dynamics of the hydrosphere (underground and surface), as well as the gas sphere, are especially relevant both in the regions of uranium ore fields and in areas adjacent to mining enterprises. Beyond the direct influence on the radioecological situation of uranium mining enterprises, special attention should be paid to the study of the dynamics of the lithospheric surface, including fault-block structures and the kinematics of ruptures, affecting the spread of groundwater and, as a result, surface waters contaminated with uranium in the environment. In the areas of uranium ore fields, the kinematic characteristics of disjunctivals contribute to a more correct forecast of radon accumulation in natural weakly insulated underground decompressed structures and the accumulation of more long-lived products of its decay Po, Bi, and Pb with long periods of removal of biological objects from organisms. It is emphasized that in the mine workings of mining enterprises, the technological process is accompanied by nitrate pollution of groundwater due to the use of nitrate-based explosives. Thus, for the predictive assessment of radiation and nitrate pollution of the environment of industrial sites of mining enterprises and adjacent territories, the technological process of which also affects the dynamics of the litho-hydro- and gas sphere, the structural-geological, paleogeomorphological, lithological, hydrogeological, hydrographic and topographic features of the Vatutinske and Novokostiantynivske uranium ore fields. The directions of the advancement of the groundwater fronts from directly uranium mines to the nearest drains have been established. The levels of uranium pollution of surface and underground (well) waters within the Novokostiantynivske uranium ore field, as the most promising for increasing uranium mining in the coming decades, have been determined. The proposed areas and terms of complex radioecological monitoring of the Novokostiantynivske uranium ore field in order to take preventive measures to prevent the withdrawal of existing local recreational areas and water areas into the category of ecologically hazardous. On the example of the Novokostiantynivske uranium deposit, as one of the richest endogenous deposits in Ukraine, through the production shafts, which is planned to rise to the surface of uranium ore from the same type of deposits of the uranium ore field of the same name (Lisne, Litniy and Dokuchaivske) by transporting it by main drifts, the proposed optimal complex of geodynamic studies in the system of radio and general ecological monitoring of the state of the environment of such territories.

The alluvial plain of wadi Nador is a semi-arid coastal area where groundwater resources have been widely affected by marine saltwater intrusion. This phenomenon is probably not the only one responsible for the excessive salinity of the water. To better understand the origin of this mineralization, nineteen water samples were collected from the study area in October 2018, and physico-chemical analyzes were done. The results show that the electrical conductivity values vary between 1.4 and 4.2 mS/cm, as well as a clear dominance of chloride, calcium and sodium ions. Significant contamination by nitrates also occurs, since more than 42% of the samples exceed the potability standard of the World Health Organization (set at 50 mg/L). Statistical and hydrogeochemical studies have highlighted the existence of several natural and anthropogenic factors involved in the acquisition of the mineralization mechanisms of these waters, such as minerals dissolution (calcite, halite, gypsum, etc.), leaching of the unsaturated zone, the return of irrigation water as well as nitrate pollution, which can have multiple sources (natural, agricultural or domestic). [ABSTRACT FROM AUTHOR]

Sporadic rainfall and limited surface water sources have increased dependency on groundwater in semi-arid region of Punjab. The present paper is comprehensive study carried out in an intensive agricultural region of southwest Punjab to examine the quality and extent of contamination due to trace elements and nitrate in the aquifer system. Total 15 toxic elements are analyzed in groundwater samples (N = 129) covering both the shallow (<60 m) and deeper aquifers (>60 m). Elements such as As, B, Cd, Li, Mn, Pb, Sr, and Se exceed the prescribed limits. Overall, 68 and 13% of samples exceed the NO3− permissible limit (45 ppm) in shallow and deep aquifers, respectively. Contaminants concentration increases toward groundwater flow direction, that is, from northeast to southwest possibly due to arid climatic conditions. Relatively, shallow aquifer is more contaminated than deeper aquifer due to fertilizers input and irrigation return flow. Drinking water quality indices (DWQI) reveal that groundwater is unfit for drinking at most locations. Further, health risk indicate that comparatively, children are at higher risk in terms of non-carcinogenic risk posed by nitrate, and higher carcinogenic risk for As, Cr, and Cd is seen in all age groups. Multivariate analysis reveals the influence of anthropogenic activities on NO3−, Mn, Ni, and Zn levels, while geogenic factors control the, As and Mo concentrations. Present findings suggest regular monitoring of wells to lower the public health risk. [ABSTRACT FROM AUTHOR]

A coupled methodology of nitrogen isotopes, hydrogeochemical characterization, multivariate statistical analysis, and SIAR Bayesian modeling has been employed to identify the sources of NO3− and N transformation processes in three alluvial aquifers (Schinos, Thiva, and Central Evia) located in central Greece where geogenic Cr(VI) co-occurs with agricultural activity and rural development. Hexavalent chromium concentrations exceed 50 μg/L in many sampling stations of the studied groundwater bodies, while nitrate contamination is evident in all three study areas with concentrations well over 50 mg/L. The mean δ15N-NO3– and δ18Ο-NO3− values are 6.67 ± 1.77‰ and 2.68 ± 1.77‰ in C. Evia, 8.72 ± 4.74‰ and 3.96 ± 4.57‰ in Schinos and 4.44 ± 1.71‰ and 2.91 ± 1.02‰ in Thiva, respectively. Domestic sewage and N-bearing fertilizers are contributing in various degrees to the observed nitrification which is the dominant transformation process of N in the studied aquifers. Multivariate statistics indicated that the main processes identified in the study areas are salinization, silicate dissolution, and groundwater contamination due to fertilizer use. It is suggested that ultramafic rock–related alluvial aquifers must be closely monitored in terms of nutrient inputs as an effective measure for controlling Cr(VI) release in groundwater. [ABSTRACT FROM AUTHOR]

articulate nitrate (NO3-) is the one of the dominant components of fine particles in China, especially during pollution episodes, and has a significant impact on human health, air quality and climate. Here a comprehensive field campaign which focus on the atmospheric oxidation capacity and aerosol formation, and their effects in Yangtze River Delta (YRD) had been conducted from May to June, 2019 at a regional site in Changzhou, Jiangsu province in China. The concentration of NO3-, OH radical, N2O5, NO2, O3 and relevant parameters were measured simultaneously. We showed a high NO3- mass concentration with 10.6 ± 8.9 μg m-3 on average, which accounted for 38.3 % of water-soluble components and 32.0 % total PM2.5, and followed by the proportion of sulfate, ammonium and chloride by 26.0 %, 18.0 % and 2.0 %, respectively. This result confirmed the heavy nitrate pollution in eastern China not only happened in winter but also summer time. High nitrate oxidation ratio (NOR) during this study emphasizes the fast nitrate formation capacity in YRD. It is found that OH + NO2 at daytime dominates nitrate formation on clean days while N2O5 hydrolysis largely enhanced and become comparable with that of OH + O2 during polluted days (47.1 % and 52.9 %). An updated observed-constrain Empirical Kinetic Modeling Approach (EKMA) was used to assess the kinetic controlling factors of both local O3 and NO3- productions, which indicated that O3-targeting scheme (VOCs: NOx = 2:1) is effective to mitigate the O3 and nitrate pollution coordinately during summertime in this region. Our results promote the understanding of nitrate pollution mechanisms and mitigation based on field observation and model simulation, and call for more attentions to nitrate pollutions in summertime. [ABSTRACT FROM AUTHOR]

Anthropogenic influences and the excessive input of reactive nitrogen compounds into the environment have already severely destabilized the natural nitrogen cycle. Especially in northwestern Germany, many water bodies are polluted by nitrate, inducing negative effects on the ecosystem and drinking water as well as possible risks to human health. In cooperation with almost 600 citizens and 200 students, this issue was addressed in a citizen science project carried out by the Universities of Osnabrück and Oldenburg, gathering 8754 nitrate measurements at 545 monitoring sites from September 2019 to March 2021. The data were used to evaluate the potential of citizen science for research on nitrogen pollution of water bodies. In a pre-investigation, we proved that nitrate test strips are suitable as a measurement method for the citizen science approach to provide an overview of nitrate pollution. We then analyzed whether the citizen science approach can be used to establish an area-wide representative measurement network, to what extent the data can be used for spatial and temporal analyses, and whether the data are consistent with the results of other monitoring initiatives. For this purpose, geoprocessing tools, such as spatial joins and heatmaps, were combined with descriptive statistics and nonparametric statistical tests. Although it was not possible to establish a representative monitoring network due to the uneven spatial distribution of monitoring sites, a large part of the intended area was covered by monitoring sites. Thus, the data provide a good overview of the nitrate pollution in the region and shed light on influencing factors. Spatial impacts, such as land cover and use and hydrogeological conditions, as well as seasonal impacts were statistically evidenced with the citizen science data. Furthermore, the consistency of the data with the measurement results of established measurement initiatives confirm the quality of the citizen science dataset. Accordingly, citizen science can be used to investigate spatial and temporal factors influencing nitrogen pollution, and thus contributes to water conservation research as an innovative approach. [ABSTRACT FROM AUTHOR]

Owing to the significant reductions in streamflow and an increase in human activities in recent years, the quality of surface water in Weihe River continues to pose environmental health concerns. We utilized hydrochemistry and nitrogen and oxygen isotopes to elucidate the status and identify sources of nitrate pollution in the south and north banks for three seasons (flood, dry, and mean-flow periods) in the Weihe River watershed. A Bayesian isotope mixing model was applied to estimate the contributions of four potential N O 3 − sources to river pollution (manure and sewage, soil nitrogen, inorganic fertilizer, and nitrate in precipitation). The U.S. Environmental Protection Agency (USEPA) evaluation model was implemented to evaluate the health risks associated with nitrate pollution in the surface water. Nitrate pollution was most severe during the dry period because the river flow was small. Due to the influence of the topography and land use type of the Weihe River, the pollution in the main stream was greater than that of the tributaries, and the pollution of the south bank was greater than that of the north bank. During the flood and mean-flow periods, δ15N and δ18O were mainly distributed in the N H 4 + of the fertilizer and soil nitrogen. During the dry period, δ15N and δ18O were mainly distributed in domestic sewage and manure regions. According to the Stable Isotope Analysis in R (SIAR) model, manure and sewage were the major nitrate sources during the dry period (73%). However, a decrease in the contribution from domestic sewage and manure was observed during the flood period (45%) compared to the dry period, but with a significantly increased contribution from soil nitrogen (23%) and inorganic fertilizer (21%). The health risk value in the dry period was higher than that in the wet and mean flow periods, and children are more susceptible to nitrate pollution than adults. Therefore, reducing the discharge of domestic sewage and manure and improving the utilization rate of nitrogen fertilizers may be effective measures to improve water quality in the watershed. [ABSTRACT FROM AUTHOR]

Nitrate is a common pollutant in most of Asian countries, notably in underdeveloped countries like Afghanistan. From the very first hydrochemical studies, high nitrate level was of great concern. Also, multiple investigations have approved the concern as they showed dangerous content of nitrate in water resources in Afghanistan. Water projects have so far focused mainly on Kabul and then its chemical composition more defined rather than other main cities. The major source of nitrate in Kabul city is domestic sewage, including cesspits and latrines. Moreover, growing population is another major concern because more than 5 million live in the city, while the city's potential is less than 2 million. Kabul city has suffered from an ineffective sewage network, and this imposed a high load of nitrate into the Kabul's groundwater system. Studies showed that high percentage of samples—on average approx. 30%—had nitrate concentrations exceeding World Health Organization and Afghanistan National Drinking Water Standard limits, which is 50 mg/L. Then, this leads to a set of public health problems in Kabul's residents. Hydrogeochemically, NO3 formation processes and following hydrogeochemical reactions are completely explained. In terms of denitrification, based on Kabul city condition and comprehensive assessments, permeable reactive barrier technique is highly recommended. The review provides a solid and knowledge-based framework for further projects and researchers. It increases public and global awareness concerning the extent of nitrate pollution in Kabul city and can serve as valuable reference for similar areas around the globe. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ru-Pd/CeO 2 achieves near 100% ammonia selectivity in nitrate hydrogenation. • Oxygen vacancies and hydrogen spillover from Pd enhance Ru catalyst performance. • Complete conversion of 2000 ppm nitrate to ammonia in 80 min using Ru-Pd/CeO 2. • Ammonia yields up to 16440 mg·h-1·g Ru -1, 3.6 wt% ammonia obtained after enrichment. • The proposed approach remediates nitrate while yielding ammonia solution sustainably. Elevated nitrate levels in natural water bodies significantly disrupt the global nitrogen cycle and pose a substantial environmental and human health risk. This study investigates the selective conversion of nitrate to ammonia via catalytic hydrogenation. This highly efficient and selective process offers a sustainable alternative to traditional ammonia production methods while simultaneously addressing nitrate pollution. Ruthenium (Ru) catalysts supported on ceria (CeO 2), titania (TiO 2), and tin dioxide (SnO 2) were synthesized using a simple impregnation method, incorporating oxygen vacancies and low Palladium (Pd) loadings (0.25–0.5 wt%) to enhance catalytic performance. Ru-Pd/CeO 2 exhibited superior activity and selectivity, maintaining near 100 % ammonia selectivity across various nitrate concentrations. At 75 °C, complete conversion of 2000 ppm nitrate to ammonia was achieved within 80 min using Ru-Pd/CeO 2 , and the yield of ammonia can reach up to 16440 mg•h−1•g Ru -1. Subsequent ammonia enrichment through evaporation yielded pure ammonia solutions up to 3.6 wt%. Characterization and theoretical calculations suggest that abundant oxygen vacancies on the CeO 2 surface and efficient hydrogen spillover from Pd nanoparticles synergistically contribute to the Ru-Pd/CeO 2 catalyst's superior performance. The catalyst exhibited excellent stability and reusability, maintaining high activity and selectivity over four cycles. This research presents a promising strategy for addressing nitrate pollution in water bodies while offering a sustainable and environmentally friendly route for ammonia synthesis. The findings of this study lay the foundation for further advancing and potentially implementing catalytic hydrogenation technology for nitrate pollution remediation and ammonia synthesis. [ABSTRACT FROM AUTHOR]

Nitrate is one among the necessary substance in the biosphere as its presence is pivotal to ensuring healthy vegetation and human health while its excess causes serious adversities. In this work, we utilized the electrified liquid-liquid interface (eLLI) and voltammetry to develop an alternative approach that enables onsite periodic monitoring of nitrate ions in cyanobacteria growth medium. The signal attributed to nitrate detection was directly related to its interfacial ion transfer behavior and not the redox properties. The ion transfer voltammograms of nitrate at eLLI delivered useful analytical parameters of linear detection range from 20 to 500 μM paired with detection and quantification limits of 1.5 and 14.6 μM, respectively. Further, the influence of chloride ions, and other anionic species present in the algae grow media were studied towards the determination of nitrates. We also optimized an in-situ chemical precipitation strategy to eliminate the influence of chloride ions that significantly improved the accuracy of the eLLI-based nitrate sensor. eLLI-based nitrate sensor delivered a remarkable analytical performance to determine nitrate levels in Z8 medium composed of nitrate and other nutrients (medium serving as the optimal environment for algae growth). eLLI based nitrate sensor was successful towards periodic monitoring of nitrate levels in Microcystis aeruginosa cyanobacteria samples cultured in Z8 medium. [Display omitted] • Nitrate can be detected at the ITIES in the presence of chlorides. • Chloride ion removal methodology is proposed. • Nitrate concentration can be followed in the cyanobacteria growth medium. • Nitrate ion transfer is followed with voltammetry. • Chemical constituents present in the cyanobacteria growth medium do not interfere. [ABSTRACT FROM AUTHOR]

Due to rapid economic growth and over-exploitation of groundwater, nitrate pollution in groundwater has become very serious. The main objective of this study is to modify the DRASTIC model to identify groundwater vulnerability to nitrate pollution. The DRASTIC model was firstly used to analyze the intrinsic vulnerability. The DRASTIC model with the inclusion of a land-use factor (DRASTIC-LU) was put forward to map the specific vulnerability of groundwater. Furthermore, the support vector machine (SVM) was introduced to avoid the drawback of the overlay and index methods, and the improved integrated models of DRASTIC + SVM and DRASTIC-LU + SVM were built. Moreover, 103 groundwater samples were collected for building and validating the models. The Root Mean Squared Error (RMSE) of DRASTIC, DRASTIC-LU, DRASTIC + SVM, and DRASTIC-LU + SVM was found to be 0.853, 0.755, 0.631, and 0.502, respectively. The model DRASTIC-LU was more precise than the original one. The results also showed that the integrated model using SVM exhibited better correlation between the vulnerability value and the nitrate pollution. The study indicated that the modified models including the land-use factor as well as SVM in the DRASTIC model were more suitable to assess the groundwater vulnerability to nitrate. HIGHLIGHTS The improved DRASTIC-LU model was put forward to delineate groundwater specific vulnerability.; Support vector machine was introduced to further build the novel integrated model to analyze the intrinsic and specific vulnerability of groundwater.;

Emulsified vegetable oil (EVO), as a novel green slow-releasing substrate, has performed great potential in subsurface bioremediation due to its slow release and longevity. Nevertheless, the long time it takes to initiate this process still exposed some limitations. Herein, multiple enzyme-based EVOs (EN-EVOs) were developed to enhance the quick-acting effect in nitrate-contaminated bioremediation. This study demonstrated that EN-EVOs loaded with cellulose (c-EVO) and protein enzymes (p-EVO) performed best, not only did not change the advantages of traditional EVO, but also optimized the stability and particle size to the level of 0.8–0.9 and 247.95–252.25 nm, respectively. Nitrate (NO 3 –N) degradation further confirmed the superiority of c-EVO in rapidly initiating degradation and achieving stable denitrification. Compared with traditional EVO, the maximum start-up efficiency and the rapid achieving stable denitrification efficiency were improved by 37.6% and 1.71 times, respectively. In such situation, the corresponding NO 3 –N removal efficiency, kinetics rate constant (k 1), and half-life period (t 1/2) reached as high as 85.39%, as quick as 1.079 d−1, and as short as 0.64 d after 30-day cultivation. Meanwhile, the rapid conversion efficiency of NO 2 –N was observed (k 2 = 0.083 d−1). High-throughput 16S rRNA gene sequencing indicated that the quick-acting process of NO 3 –N reduction coupled to c-EVO was mediated by microbial reducers (e.g., Ralstonia , Gulbenkiania , and Sphingobacterium) with regulations of narG, nirS and norB genes. Microorganisms with these genes could achieve quick-acting not only by enhancing microbial activity and the synthesis and metabolism of volatile fatty acids, but also by reducing the production and accumulation of loosely bound-extracellular polymeric substances (LB-EPS). These findings advance our understanding on fast-acting of NO 3 –N degradation supported by c-EVO and also offer a promising direction for groundwater remediation. • Multiple EN-EVOs are successfully prepared to make up for the deficiency of EVO. • EVO loaded with cellulose can enhance the rapid start-up of nitrate bio-reduction. • c-EVO can enhance microbial activity and reduce LB-EPS for accelerating initiation. • New-emerged functional genera with regulations of nirS genes are essential reasons. [ABSTRACT FROM AUTHOR]

Due to increasing intensive agricultural activities, the importance of water quality for drinking is increasing over time. Especially, high concentrations of nitrate (NO 3 –) can cause severe health problems such as cyanosis in infants. This article reviewed the general plant biochemical responses to NO 3 – contamination and examined case studies currently used for NO 3 – removal and phytoremediation of most common tree species and confirmed whether conifer tree species have been conducted for nitrogen pollution research and compiled currently available 117 publications in forest tree species in phytoremediation study. It was explored how intensive agricultural activity can cause nitrate pollution and documented that 89% of the New Zealand's plantation forests are Pinus radiata species, consisting of 1.63 million hectares and the N uptake potential by P. radiata ranged from 3 to 109 kg ha−1 y−1 based on literature review. Also, it was discussed that if it is necessary to pay attention to the role of Pinus radiata in farmlands and streams to develop novel ideas that can positively affect New Zealand's environmental policy in the post-Paris Agreement era. I propose to consider choosing and exploiting Pinus radiata for several reasons: (1) to foster Pinus radiata research in nitrogen pollution research, finding new biological functions including the benefits of NO 3 – removal with conifer tree species; (2) to attract the attention to conduct the study of NO 3 – toxicity to plants and (3) to improve the attention of agroecosystem resilience based on fast-growing conifer trees' regulating services. This article aims to re-evaluate our understanding of whether New Zealand's Pinus radiata can deal with environmental stress conditions similar to more commonly studied fast-growing broad-leaved tree species. [ABSTRACT FROM AUTHOR]

[Display omitted] • s-ZVI-coupled Myriophyllum aquaticum- derived biochar favors C storage more than I.H. • Biochar nature or feedstock may control C trap and N removal gains from Fe-C coupling. • Biochars trigger C dynamics depending on trade-offs between priming and increased MBC. • Enhanced iron gate contributes to synergistic C sequestration and C sink augmentation. • β -glucosidase activity and Fe-OC increases jointly drive C cumulation in Fe-C ditches. Carbon dioxide (CO 2) is a more powerful greenhouse gas due to its enhanced instantaneous radiative forcing. Since agricultural ecological ditches (eco-ditches) controlling agricultural non-point source pollution are potential CO 2 hotspots, carbon capture technologies must be deployed immediately to sequester carbon and combat climate change. Zero-waste biochar, a negative-carbon technology, remains contentious regarding C sequestration. Iron (Fe) enhances long-term organic carbon (OC) preservation, but the cascading effects of Fe-biochar interactions on the promotion of C accumulation are unclear in eco-ditches. In this paper, we fill these research gaps and employ sponge iron (s-ZVI) and biochar coupling (Fe-C) to enhance the iron gate C protection in eco-ditches. The results reveal that Myriophyllum aquaticum(M.A.) -derived biochar prepared by low-temperature pyrolysis (Biochar_M.A.) enjoys the highest FI, the lowest SUVA254 and SUVA280 and moderate dissolution stability. The coupling of s-ZVI and environmentally compatible Biochar_M.A. achieve a triple benefit situation of C sequestration, C sink, and pollutant removal. Overall carbon gain is jointly determined by abiotic controls and biotic controls. The carbon burial effects of biochar-amended eco-ditches are mainly controlled by the trade-offs between Fe-bound OC mineralization via the biochar-induced prime effect and preservation of OC derived from microbial biomass. The unique Fe-C boosts the rusty sink and yields a negative priming as a result of the dominance of Fe-OC. The upregulated β -glucosidase activity and new-formed Fe-OC indirectly and directly contribute to overall C gain in Fe-C-filled eco-ditches, respectively. These findings provide novel insights into the coupled biotic-abiotic contribution mechanisms underlying the iron gate and reverse enzyme latch phenomenon and advance more robust and prospective theoretical knowledge of C dynamics that are not restricted to eco-ditches, soil, constructed wetlands C storage. [ABSTRACT FROM AUTHOR]

Agricultural activities have become a major source of groundwater nitrate contamination. In this context, this study aims to analyse nitrate concentrations in a shallow aquifer of Mahdia-Kssour Essef in central-eastern Tunisia, identify the assignable sources, and predict the future levels using artificial neural network (ANN) and autoregressive integrated moving average (ARIMA) models. The results showed that nitrate concentrations measured in 21 pumping wells across the plain ranged from 17 to 521 mg L−1. A total of 67% of the monitoring points greatly exceed the standard guideline value of 50 mg L−1. The main relevant anthropogenic and natural factors, such as soil texture, land use, fertilizers application rates, livestock waste disposal, and groundwater table, are positively correlated with groundwater nitrate concentration. The ANN model showed good fitting between measured and simulated results with coefficient of determination (R2), root-mean-square error (RMSE), and mean absolute error (MAE) values of 0.88, 53.95, and 39.64, respectively. The ARIMA applied on annual average nitrate concentrations from 1998 to 2017 revealed that the best fitted model (p, d, q) is (1, 2, 1). The R2 value is approximately 0.36, and the Theil inequality coefficient and bias proportion values are small and close to zero. These results proved the ARIMA model's adequacy in forecasting annual average nitrate concentrations of 116 mg L−1 in 2025. These findings may be useful in making groundwater management decisions, particularly in rural and semi-arid areas, and the proposed ARIMA model could be used as a managed tool to monitor and reduce the nitrate intrusion into groundwater. [ABSTRACT FROM AUTHOR]

The present study examines the groundwater quality of the Bengal Basin and its surrounding areas of India. The quality (corrosion and scaling potential) has been assessed on 161 groundwater samples using Langelier saturation index (LSI), Ryznar stability index (RSI), Puckorius scaling index (PSI), Aggressive index (AI), and Larson-Skold index (LS). The results portray that the average concentrations of the selected cations are in the sequence of Ca2+ > Mg2+ > Na+ > K+and anions of HCO3− > Cl− > SO42−. Besides, 70% of the water samples portray that the alkaline earth (Ca2+ + Mg2+) surpasses the alkalies (Na+ + K+). The major hydro-chemical facies identified in the groundwater samples are Ca2+ − Mg2+ − HCO3− and Ca2+ − Mg2+ − Cl−. Moreover, the LSI, RSI, PSI, AI, and LS indices for corrosion and scaling potential exhibit a higher scaling potential than the corrosion tendency. For example, about 60% of the water samples for LSI, PSI, and AI indicate scale type of water. Besides, the indices show a significant spatial variation of groundwater quality in the study region where the southern part of the study region depicts higher corrosion potential while the eastern part portrays a higher scaling tendency. The factors and mechanisms controlling the groundwater hydro-chemistry in the study area include the weathering of Na+ containing minerals, dissolution of carbonate minerals, seawater intrusion, and anthropogenic influx mainly from agricultural fertilizers, industrial, and municipal sewage. The study identifies corrosion and scaling problem regions that would be of great help for the society for adopting an appropriate strategy in the water distribution system for reducing the economic stress on agriculture and improving drinking water quality for human health. [ABSTRACT FROM AUTHOR]

Monitoring groundwater quality and analyzing geochemical processes are very crucial in dry environments, especially in areas with intense agriculture and inadequate irrigation management systems. A total of forty-one groundwater samples were collected from the study area and analyzed for major ions chemistry. The results of the geochemical analyses are used to investigate the geochemical processes and make groundwater assessments. The hydrogeochemical characteristics of the groundwater samples revealed a highly mineralized Na+–Cl− water type, implying that the majority of the samples are chemically unfit for human consumption. Based on the water quality parameters analyzed for the groundwater samples collected in this study, such as sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium hazard (MH), permeability index (PI), and Kelley's ratio (KR), the suitability of groundwater samples for irrigation purposes is good to moderately good. Also they may reflect some alkaline hazard threats to the soil as indicated by the SSP and KR. The salinity hazard is recognized as high and expected to increase with the expansion of irrigation; hence, special salinity control management for groundwater in the study area is required. Nitrate is widely recognized as a contaminant in the study area. The nitrate concentrations range from 0.1 to 256.8 mg/L, with more than 30% of the samples exceeding the safe drinking water limit of 50 mg/L. The main concern is that the average nitrate concentration will likely continue to increase in the groundwater of the study area. Groundwater monitoring, in terms of both quality and quantity, is essential for sustainable groundwater management. [ABSTRACT FROM AUTHOR]

Affected by excessive fertilizer application and livestock breeding, the problem of nitrate pollution in the groundwater in the Mihe alluvial–diluvial fan area is becoming increasingly prominent, which poses a great threat to human production and life. Given this, the risk of nitrate pollution in the shallow groundwater of the Mihe alluvial–diluvial fan is evaluated by introducing a data envelopment analysis (DEA) method. Using this model, 28 groundwater sampling points are selected as the decision-making unit (DMU); the nitrogen and pesticide application rate, livestock and poultry stock, groundwater burial depth, aquifer water abundance, and vegetable planting area are taken as the model input; and the nitrate content is taken as the model output to quantitatively calculate the pollution risk index to form a spatial distribution map of pollution risk. The calculation using the model shows that the average pollution risk index of the study area is 0.382, the spatial variation is 1.12, the pollution risk index gradually decreases from south to north, and agricultural planting and livestock and poultry breeding are the main pollution sources. The calculation of nitrate pollution risk using this model not only enriches the nitrate pollution evaluation model but also provides a basis for further implementing the action of reducing fertilizer use by increasing its efficiency and strengthening the prevention of agricultural diffused pollution. [ABSTRACT FROM AUTHOR]

This paper reports on the data on the quality of fresh groundwater in the foothills of Crimea, including the waters that are used for the water supply of the Crimean Base of St. Petersburg State University and the Bogdanov Crimean Geological Scientific-Educational Center, Moscow State University. The results of the long-term monitoring of the chemical composition of potable fresh waters have been presented and the high-priority pollutants have been identified. Hydrochemical modeling was carried out to calculate the transport forms of chemical elements and to assess their toxicity. The study area is located in an area of the active water exchange. Therefore, most of the chemical elements in the groundwater are present in concentrations below the level of biologically significance. [ABSTRACT FROM AUTHOR]

In the recent years, the vulnerability of groundwater aquifers to pollution is one of the major issues. The fast growth of industrialization, deforestation and agricultural activities are the potential sources for groundwater pollution. Assessment of groundwater vulnerability in a region is necessary for any groundwater management and developmental activities. The present study assess the aquifer vulnerability to contamination along a limited stretch of Cauvery River (Kumarapalayam to Kokkarayanpettai) in Namakkal and Erode district, in the state of Tamil Nadu, India, using modified DRASTIC model. The textile dyeing units and other small-scale industries are located along Kumarapalayam to Kokkarayanpettai stretch on the bank of the Cauvery River. The river course is highly polluted due to disposal of effluent from a number of dyeing industries. In the first step, the ranks and weights were assigned for the DRASTIC parameters including groundwater depth (D), net recharge (R), aquifer media (A), soil media (S), topography (T), impact of vadose zone (I) and hydraulic conductivity (C). These parameters were integrated and reclassified into five categories such as very low (1.88%), low (9.33%), moderate (24.23%), high (52.57%) and very high (11.99%) vulnerability zones. The results revealed that about 64% of the study area was affected by groundwater vulnerability as per DRASTIC index. Further, the lineament density and land use/land cover were incorporated in the DRASTIC model. The integrated results also show the major groundwater aquifer zone in the study area vulnerable to pollution. Finally, the modified DRASTIC model was validated with nitrate (NO3) concentration in the groundwater samples and it shows 82.42% accuracy in the result. It confirms that the modified DRASTIC model is one of the essential tools to estimate the groundwater pollution risk. The overall results revealed that the groundwater aquifer in the study area is facing contamination due to sewage disposal and dyeing industry. Immediate attention is required for maintaining groundwater aquifer free from contaminations. [ABSTRACT FROM AUTHOR]

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The Songnen Plain in Northeast China is the only remaining black soil agricultural area in the world and is an important food base for China. The groundwater resources in this area are abundant, but human activities have caused them polluted. This paper established a groundwater vulnerability assessment to characterize the influence of human activities which used an entropy weight method. The index was tested using the nitrate pollution distribution in the groundwater to verify the effectiveness of this method. The results showed that areas with high specific vulnerability were distributed in the northern and eastern parts of the Songnen Plain and were consistent with areas that showed serious nitrate pollution of the groundwater. The correlation coefficient between these areas was 0.2536, which greatly improved the vulnerability assessment without superimposing human activities in the model. The results clearly showed that human activities increased groundwater vulnerability on the Songnen Plain. The evaluation method provided a reference for similar evaluations and a basis for the protection and management of groundwater resources in this region. HIGHLIGHTS Establishing a groundwater vulnerability assessment method to characterize the influence of human activities using an entropy weight method.; Entropy weight method coupled with an improved DRASTIC model to evaluate the special vulnerability of groundwater for water management.;

Nitrate (NO3−) pollution of surface and groundwater bodies is a global problem of increasing concern, which has stimulated significant research interest. Nitrogen is crucial for life as a macronutrient for living organisms on Earth, but the global nitrogen cycle has been seriously altered by intensification of human activities, leading to eutrophication and hypoxic conditions of aquatic ecosystems. Due to nitrogen overfertilization, intensive agricultural practices generate huge nitrate fluxes that inadvertently deteriorate water quality. Different industrial processes also contribute to NO3− pollution in the environment. There are multiple technologies capable of achieving effective denitrification of waterbodies to ensure safe NO3− levels. Either separation-based or transformation-based denitrification technologies must address the challenges of by-product generation, increased energy demand, and reduced environmental footprint. This paper highlights the most used approaches, along with some promising alternatives for remediation of nitrate-polluted waters.

Nitrate (NO3−) contamination has become a dominant international problem in the aquatic environment, so identifying the sources and transformations of NO3− is the basis for improving water quality. Since the Jing River is the largest tributary of the Wei River, to understand its water quality, this study collected surface water samples from the Shaanxi section of the Jing River during the dry season. The potential sources of NO3− were analyzed by hydrochemical and bi-isotopic methods, and the SIAR model was used to estimate the proportional contribution of each source. Results indicated that NO3−-N was the main form of inorganic nitrogen in this area, and the average total nitrogen content was 10.23 mg·L−1, which showed that nitrogen pollution was highly serious; the transformation process of nitrogen in this study area was mainly nitrification; The results of Bayesian model showed that manure and sewage contributed to the most NO3− (64.39%) in the dry season, followed by soil nitrogen, which was 26.35%. These results help to adopt better nitrogen management measures to meet the national environmental quality standards for surface water. [ABSTRACT FROM AUTHOR]