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Introduction: World's population growth and limited water resources and needing to more food production led to interest farmers to use nitrogen fertilizer more than soil requires and subsequently Nitrate leaching causes groundwater and environmental pollution. Therefore, researches has concentrated on improvement of nitrogen use efficiency, which numerical simulation is the effective solutions to optimize the management of water and fertilizer in the field in order to achieve the maximal yield and minimal nitrate pollution of soil, groundwater and drainage in water deficiency crisis condition. For this reason, the evaluation of new user friendly models in correct estimation of soil moisture and nitrogen content distribution and recognition of water and solutes movement in the soil and choosing the best management option for increasing productivity and economic performance and also reduction of nitrate pollution of soil and ground water source with the least limitations and high accuracy is necessary. The Eu-Rotate-N model has been developed for simulation of nitrogen use and specifically for optimization of nitrogen use in variation of vegetables in a wide range of conditions, which without the need to calibration has presented satisfactory results in many areas. So this study was conducted to evaluate the efficiency of Eu-Rate-N model in assessment of moisture and nitrogen distribution and yield under different nitrogen fertigation management for pepper plant. Materials and Methods: Sweet pepper was planted at density of 8.33plant per m2 in a row planting method. 150kg per hectare per year of fertilizer was used during the season. Crop yield, soil water and nitrogen content were measured on a regular basis. The treatments consisted of three fertilizer level: zero (N0), the ratio of ammonium to nitrate 20:80 (N1) and 40:60 (N2), which was conducted in a completely randomized block with three replications in Isfahan. Irrigation based on daily monitoring of humidity was used with drip irrigation system. The irrigation Depth was calculated and applied with aim of replacing the water content deficiency in the root zone up to field capacity (FC) for the no water deficit treatment. Coefficients were modified only for plant coefficients and length of each growth stage according to the area. To compare simulated data with measured data in field, indices of statistical root mean square error (RMSE), normalized root mean square error (NRMSE), coefficient of determination (r2) and index of agreement Wilmot (d) were used. Results and Discussion: The NRMSE index for nitrate and soil water content was 11.45, 12.08, the RMSE was 0.89, 0.022, the r2 was 0.998, 0.996 and the d was 0.667, 0.66 respectively. All calculated indices for soil water and nitrate content were in the acceptable range. NRMSE index was less than 20 percent in all treatments which was indicating good ability of model in simulating soil water and nitrate content and r2 was more than 90 percent which pointed out to well process of simulation of the model. The simulation accuracy was greater at the end of the growing season. Comparing of RMSE statistical index for different depths showed that the simulation accuracy was increased by increasing depth which can be due to changes in surface evaporation and also the effect of environmental factors on surficial layers more than other layers. Generally the best simulation was related to the layer of 80 to 100 cm. And the average RMSE was 0.019 cm3 per cm3 for soil moisture content and 0.22 mg per kg for soil nitrate.In the layer of 80-100 cm the best simulation of soil moisture and nitrate content between treatments was related to N0 by the RMSE equal to 0.024 cm3 per cm3 and 0.21 mg per kg respectively and the weakest simulation was related to N3.The simulated yield in all treatments was less than its actual value. Comparison of simulations between three treatments demonstrated the usefulness of EU-Rotate N to examine the effects of management on, nitrate leaching. Conclusions: The Eu-rotate-n model without calibration for site location was well capable of estimating soil water and nitrate content under different fertilizer management for Isfahan climatic conditions nevertheless it is suggested to use to calibrate yield functions to improve the yield simulation. Generally we can use Eu-rotate-n model for simulation of water and nitrogen content and eventually approach to integrated and optimal management in the farm in the hot, dry conditions of Isfahan.

The article introduced an upgraded approach to assessing the groundwater vulnerability to nitrate pollution. By using the results of fild measurements and process-based models outputs, author takes into account effects of nitrogen biogeochemical processes, that were hitherto underestimated in the evaluation schemes. The upgraded methodological self-validated approach to vulnerability assessment in Lower Savinja Valley case study increases reliability and thus effectiveness of decision-making in the water management. This was achieved by using the process-based models outputs in the new pattern classifiation schemes with the predictions of pollution phenomena. Spatial prediction of groundwater nitrate pollution probability and vulnerability classifiation of the study area in Lower Savinja Valley was assessed by weights-of-evidence model (WofE). The increased degree of probability for the groundwater contamination with nitrates was determined for 62.5 percent of the aquifer area of the Lower Savinja Valley. About 27 percent of the most nitrate vulnerable areas in Lower Savinja Valley need groundwater nitrate mitigation through land-use measures and public sewage system construction.

Infant mortality in Kazakhstan is six times higher compared with the EU. There are several reasons for this, but a partial reason might be that less than 30% of Kazakhstan's population has access to safe water and sanitation and more than 57% uses polluted groundwater from wells that do not comply with international standards. For example, nitrate pollution in surface and groundwater continues to increase due to intensified agriculture and the discharge of untreated wastewater, causing concerns regarding environmental and human health. For this reason, drinking water samples were collected from the water supply distribution network in eight districts of Almaty, Kazakhstan, and water quality constituents, including nitrate, were analyzed. In several districts, the nitrate concentration was above the WHO and Kazakhstan's maximum permissible limits for drinking water. The spatial distribution of high nitrate concentration in drinking water was shown to be strongly correlated with areas that are supplied with groundwater, whereas areas with lower nitrate levels are supplied with surface water sources. Based on source identification, it was shown that groundwater is likely polluted by mainly domestic wastewater. The health risk for infants, children, teenagers, and adults was assessed based on chronic daily intake, and the hazard quotient (HQ) of nitrate intake from drinking water was determined. The non-carcinogenic risks increased in the following manner: adult < teenager < child < infant. For infants and children, the HQ was greater than the acceptable level and higher than that of other age groups, thus pointing to infants and children as the most vulnerable age group due to drinking water intake in the study area. Different water management options are suggested to improve the health situation of the population now drinking nitrate-polluted groundwater.

Water pollution by excessive amounts of nitrate (NO3−) has become a global issue. Technologies to clean up nitrate-contaminated water bodies include phytoremediation. In this context, this research aimed to evaluate four tree species (Salix alba L., Populus alba L., Corylus avellana L. and Sambucus nigra L.) to remediate nitrate-contaminated waters (100 and 300 mg L−1). Some physiological parameters showed that S. alba L. and P. alba L. increased particularly photosynthetic activity, chlorophyll content, dry weight, and transpired water, following the treatments with the above NO3− concentrations. Furthermore, these species were more efficient than the others studied in the phytodepuration of water contaminated by the two NO3− levels. In particular, within 15 days of treatment, S. alba L. and P. alba L. removed nitrate quantities ranging from 39 to 78%. Differently, C. avellana L. and S. nigra L. did not show particular responses regarding the physiological traits studied. Nonetheless, these species removed up to 30% of nitrate from water. In conclusion, these data provide exciting indications on the chance of using S. alba L. and P. alba L. to populate buffer strips to avoid NO3− environmental dispersion in agricultural areas.

Water-soluble inorganic ions (WSI), a major component of PM 2.5 , often increased rapidly during the haze event in Beijing. Sulfate (SO 4 2−), Nitrate (NO 3 −), and Ammonium (NH 4 +) are three main components of WSI. Since year 2015, sulfate concentrations in PM 2.5 has gradually decreased owing to the effective control of SO 2 emissions. However, the contribution of nitrate to PM 2.5 has significantly increased during haze events in Beijing at the same time. In this study, a highly time-resolved online analyzer (Monitor for Aerosols and Gases, MARGA) was employed to measure the WSI in PM 2.5 in Beijing from 5 February to 15 November 2017. Three typical haze events during this sampling period were investigated. During heavy pollution episodes in winter, nitrate concentrations increased from 7.5 μg/m3 to 45.6 μg/m3 (45.0% of WSI), while sulfate increased from 4.2 μg/m3 to 20.1 μg/m3 (19.8% of WSI). This indicated that nitrate is more important than sulfate as a driver for the growth of PM 2.5 during the period of heavy air pollution in winter. Nitrate also dominates the increase of WSI in the pollution episodes in autumn, with an average concentration of 52.5 μg/m3, and contributed up to 67% of WSI. The average concentration ratio of NH 4 + to SO 4 2− was higher in autumn (1.02) than that in summer (0.74) and close to that in winter (1.00). This is mainly because the emission control of coal combustion in Beijing and surrounding areas results in an NH 3 -rich and SO 2 -lean atmosphere, which promoted the formation of ammonium nitrate. Our study indicates that nitrate has become the most important component of WSI in PM 2.5 and is driving the rapid growth of PM 2.5 concentrations during heavy pollution episodes in Beijing. Therefore, more efforts shall be made to reduce the nitrogen oxide and ammonia emissions in Beijing and surrounding areas. Unlabelled Image • Nitrate become the main component of PM 2.5 than sulfate during the haze events in Beijing. • High NOx emission, low temperature and low aerosol acidity are the key factors to promote nitrate formation in Beijing. • Molar ratio of NH 4 + to SO 4 2- increased from 1.5 (before 2013) to 3.33 (2017) due to ammonia-rich atmosphere in Beijing. [ABSTRACT FROM AUTHOR]

Summary: Restoring plants to the riparian zone is regarded as management best practice in river restoration and has the potential to reduce the impact of nitrogen (N) pollution on aquatic organisms and improve water quality for human use. Plant characteristics and the interplay of hydrology and biogeochemistry control N retention in the riparian zone. The balance between processes such as denitrification and plant assimilation determines riparian N retention. Plant traits are likely to mediate these N removal processes through variations in root form, growth character, foliage production (quantity, quality and rate of return to the soil) and by altering conditions in the rhizosphere soil. Vegetation can slow N transfer via direct plant uptake of N (during periods of rapid vegetation growth) and changes induced to soil hydrology, nutrient cycling and microbial activity, principally denitrification. Few studies have focused on species‐dependent effects on N movement through soil and across boundaries. We propose a new framework, based on a literature review of plant traits with respect to N cycling, which can be used to select plant species with traits likely to maximise N removal during transport through the riparian zone. In the proposed framework, inter‐specific differences in traits known to influence N mobility: root form, growth rate, foliar characteristics and rhizosphere processes, are used to describe species' potential impact on N removal. Plant trait data may be drawn from studies outside the riparian zone; for example forest ecology, horticulture or forestry research, and candidate species are scored to predict N removal efficiency. We apply the framework to New Zealand's native riparian plant assemblages to demonstrate the trait‐based approach. This framework can guide restoration management decisions and investment in riparian revegetation in a manner that is not restricted to geographically specific or well‐studied species. [ABSTRACT FROM AUTHOR]

• Fe-exchanged nano-bentonite removed NO 3 − and HCO 3 − from contaminated water. • NO 3 − and HCO 3 − sorption reached equilibrium within 2 and 2.5 h, respectively. • Maximum adsorption of NO 3 − and HCO 3 − occurred at pH 6.0. • NO 3 − & HCO 3 − adsorption potentials were 64.76 mg g-1 & 9.73 meq g-1, respectively. • Lewis acid-base reaction, outer sphere complexation & ligand exchange were involved. Nitrate (NO 3 −) and bicarbonate (HCO 3 −) are harmful for the water quality and can potentially create negative impacts to aquatic organisms, crops and humans. This study deals with the removal of NO 3 − and HCO 3 − from contaminated wastewater using Fe-exchanged nano-bentonite and Fe 3 O 4 nanoparticles. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area measurement and particle size analysis revealed that the adsorbents fall under the nano-scale size range with high specific surface area, and Fe was successfully exchanged in the nano-bentonite clay. The kinetics of adsorption was well defined by pseudo-first order and pseudo-second order kinetic models for both NO 3 − and HCO 3 −. The Fe-exchanged nano-bentonite was a better performing adsorbent of the oxyanions than Fe 3 O 4 nanoparticles. According to the Sips isothermal model, the Fe-exchanged nano-bentonite exhibited the highest NO 3 − and HCO 3 − adsorption potential of 64.76 mg g-1 and 9.73 meq g-1, respectively, while the respective values for Fe 3 O 4 nanoparticles were 49.90 mg g-1 and 3.07 meq g-1. Thus, inexpensiveness and easy preparation process of Fe-exchanged nano-bentonite make it attractive for NO 3 − and HCO 3 − removal from contaminated wastewater with significant environmental and economic benefits. [ABSTRACT FROM AUTHOR]

Nitrate pollution of groundwater has increased dramatically worldwide due to increase of population and agricultural productivity. The resulting nitrate concentration in groundwater is usually a combination of various types of point and non-point pollutant sources. It is often difficult to distinguish between these sources since groundwater is formed in large and complex catchments with various natural processes and anthropogenic influence that contribute to a certain downstream nitrate concentration. For such conditions, this paper uses a methodology that can be used to inversely determine type and location of main nitrate pollutant source. The methodology builds on two state-of-the-art data mining techniques, boosted regression tree (BRT) and k-nearest neighbor (KNN). These techniques are used to produce a nitrate pollution vulnerability map. The methodology can mitigate effects of subjective judgement on determining importance of different sources and mechanisms for nitrate transport. The investigated mechanisms are hydrogeological, hydrological, anthropogenic, topography, and soil conditioning factors. Thus, the proposed methodology is used to separate between natural processes and anthropogenic effects on nitrate pollution. To calculate the groundwater vulnerability maps, a groundwater nitrate concentration of 40 mg/L (suggested by WHO with a 20% risk margin) was selected as a general threshold for identifying polluted areas that resulted in 96 polluted wells. Non-polluted locations were selected from well data with nitrate concentration less than 15 mg/L (96 non-polluted). The models were trained on 70% polluted and 70% non-polluted site data. The remaining data, 30% polluted and 30% non-polluted sites, were used to validate the simulation results. Results showed that the BRT produced outputs with higher performance than the KNN algorithm. The final ranking results based on the BRT model showed the higher importance of hydraulic conductivity, river density, soil, slope percent, net recharge, and distance from villages, in order, relative to other factors. [ABSTRACT FROM AUTHOR]

Geostatistics was used in a typical alluvial fan to reveal its applicability to spatial distribution analysis and controlling mechanisms of groundwater chemistry. Normal distribution test and optimal geostatistical interpolation models for various groundwater quality indicators were discussed in this study. The optimal variogram model of each indicator was determined using prediction error analysis. The influences of human activities and structural factors on the groundwater chemistry were also determined by variability intensity and the sill ratio. The results showed that nitrate content can be served as groundwater quality indicator, which was most sensitive to human activities. The nitrate concentration of both shallow and deep groundwater showed a decreasing trend from the northwest to the southeast. In addition, the spatial distribution of groundwater nitrate was associated with the land-use type and the lithological properties of aquifer. Rapid urbanization in the northwestern part intensified groundwater extraction and aggravated the pollutant input. The central area showed little increase in nitrate content in the shallow and deep groundwater, and the effect of lateral recharge from the upstream water on the deep groundwater in the central area was greater than that of the vertical recharge from shallow groundwater. The present study suggests that geostatistics is helpful for analyzing the spatial distribution and distinguishing the influences of anthropogenic and natural factors on groundwater chemistry. [ABSTRACT FROM AUTHOR]

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Abstract Worldwide, excessive reactive nitrogen in groundwater and surface waters is a growing problem, especially in areas that face rapid urbanization and industrialization. One example for environmental nitrogen pollution is the Lake Tai, China's third largest freshwater Lake, located in the Yangtze River basin. Due to the rapid development of the surrounding area, nitrogen compounds like nitrate are discharged into the Lake. Consequently, eutrophication and harmful algae blooms increased and led to the production of toxins directly affecting water consumers through the water supply chain. Denitrification is the main process that attenuates nitrate by converting it into atmospheric nitrogen and represents an intrinsic natural process to compensate the excess reactive nitrogen. In this study, the methodology to detect nitrate reducing bacteria on a functional gene and transcriptional level was optimized and verified in laboratory experiments with a pure culture of Pseudomonas veronii , isolated from Lake Tai. We demonstrated that transcripts analysis (mRNA) did correspond with nitrate reduction activity. Subsequently, the abundance and the activity of nitrate reducing bacteria in Lake Tai were assessed using the developed methods. We demonstrated that nitrate reducing bacteria can be found throughout all sediment and water samples taken from the northern Lake Tai in September 2017. Measurements of narG transcripts also indicated the activity of the membrane-bound nitrate reductase in the water samples. However, the bioinformatic analysis of narG sequences showed varying binding efficiency of primer and gene sites in dependence of phylogenetic groups, which may lead to an underestimation in the qPCR method. Thus, it is important to point out the precautions and limitations of primer systems to monitor nitrogen transformation by qPCR in the environment. Based on this study, mRNA detection methods are suitable for improved microbiological monitoring of denitrification, as an intrinsic process in Lake Tai to mitigate the inflowing reactive nitrogen compounds. Graphical abstract Unlabelled Image Highlights • Presence of narG genes indicates the denitrification potential in Lake Tai. • In-silico analysis reveals varying primer efficiency for environmental detection of the narG gene. • Increase of mRNA gene copies corresponded with nitrate reduction activity by Pseudomonas veronii • Development and application of mRNA analysis with environmental samples • Specific detection of mRNA shows nitrate reductase gene transcription in Lake Tai water samples. [ABSTRACT FROM AUTHOR]

Highlights • Organic C and nutrient rich sludge is a valuable alternative to mineral fertilizer. • Palak yield and availability of primary nutrients enhanced by sludge application. • Sludge application increased potentially mineralizable N and biological properties. • Contamination of crop with E. coli is a major concern grown in sludge amended soil. • High nitrate content in post-harvest soil may lead to ground water contamination. Abstract Sewage sludge being a cheap source of plant nutrient is commonly applied by farmers and is being promoted for implementation of "waste to wealth" programme in India. It has diverse impact on soil microbial properties. The aim of this study was to assess the impact of application of sludge from three waste water treatment plants namely, Okhla (Sld-O), Keshopur (Sld-K) and Pappankallan (Sld-P) in National Capital Region (NCR), Delhi, India on various soil biological properties and bio-safety of crop produce. A pot culture experiment with eight treatment combinations (3 sludge × 2 doses [i.e. 11.2 mg kg−1 + 50% recommended NPK, 22.4 mg kg−1] + recommended dose of NPK + absolute control) was conducted. The sludge amendment significantly improved the microbial biomass carbon, potential mineralizable nitrogen, enzyme activities (dehydrogenase, acid and alkaline phosphatase) as well as yield of palak. However, excess nitrate concentration (∼100% higher than control) in post-harvest soils and contamination of palak leaves with Escherichia coli is a matter of great concern and should be monitored carefully for proper utilization of sludge in agriculture. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to determine the origin and processes of groundwater salinization in the Lebna coastal aquifer in northeastern of Cap Bon, Tunisia and to identify the main sources involved in the ecosystem alterations in this zone. To reach these goals, detailed geological and hydrogeological data were used in combination with geochemical and geophysical methods. The results show that the chloride, sodium and nitrate concentrations and electrical conductivity values exceed the World Health Organization WHO standard for drinking water. Further, the groundwater chemistry is classified into two main water facies: Na-Cl and Ca-Cl. Geochemical diagrams and the Saturation Index (SI) depicted two natural factors at the origin of salinization of the shallow aquifer, i.e., seawater intrusion by mixing processes and water-rock interaction by mineral dissolution and reverse cation exchange. Moreover, we showed that agricultural activities are the main source of NO 3 , SO 4 and K ions and contribute to groundwater contamination with increasing chloride and nitrate concentrations. Based on geophysical results, we found that the seawater intrusion reaches 2.5 Km in the longitudinal direction from the sea inland and approximately 100 m in the aquifer depth. In conclusion, we were found several groundwater salinization sources in Lebna coastal aquifer, whereas, the principal mineralization origin is the seawater intrusion. This salinization influences the ecosystem change. Unfortunately, the groundwater in Lebna area is unsuitable for human drinking and irrigation uses. Highlights • Hydrochemistry and geophysical methods are used to identify the mineralization processes. • The seawater intrusion is the main salinization source in Lebna aquifer. • Reverse cation exchange and water-rock dissolution, contribute to aquifer salinization. • Agricultural activities are contributed to the groundwater mineralization and pollution. • The groundwater is unsuitable for human drinking and irrigation use. [ABSTRACT FROM AUTHOR]

Abstract Agricultural practices have raised the level of nutrients reaching aquifers. In Europe, nitrate pollution is considered as one of the main threats for the quality of groundwater in agricultural areas. Treatment wetlands (TWs), also known as Constructed Wetlands, are used for groundwater treatment in areas with an important concentration of nitrogen compounds; total nitrogen removal depends on the type and operation scheme. Cork by-product from the industry has shown clear adsorbent properties to remove organic pollutants. The work is focused on the characterization of microbial communities involved in the nitrate‑nitrogen removal process in groundwater polluted from agricultural activities. The experimental design allowed the comparison of nitrate removal efficiency depending on the filter media material, cork by-product or gravel, used in two hybrid TWs (a vertical flow cell followed by a horizontal subsurface flow cell), installed in areas close to two irrigated agricultural plots at the Lleida plain area (Spain). Both physicochemical and microbial results were consistent and confirm the nitrate removal efficiency using cork as a filter media. A significant (p = 0.0025) higher removal in Bellvís TW using cork compared with the Vilanova de la Barca gravel system was observed, achieving a removal rate from 80 to 99% compared to the 5–46%, respectively. Regarding the community composition of the two different TWs, microorganisms were mainly related to the phylum Proteobacteria, and included members found to be key players in the nitrogen cycle, such as ammonia and nitrite oxidizers, as well as denitrifiers. Also, the group Bacteroidetes turns to be another abundant phylum from our bacterial dataset, whose members are suggested to be strongly involved in denitrification processes. Some groups showed to prevail depending on the type of media (cork or gravel); Firmicutes and Delta and Epsilonproteobacteria had a significant higher abundance in the TW with cork, while Acidobacteria and Planctomyces were prevalent in gravel. Therefore, cork could be an alternative material used by treatment wetlands to minimize the impact in the environment caused by nitrogen pollution in groundwater bodies. Graphical abstract Unlabelled Image Highlights • A higher nitrate removal efficiency (80-99%) using cork as substrate was observed. • Microbial community groups showed to prevail depending on the type of granular filter media. • The relative abundance of Firmicutes and Delta and Epsilonproteobacteria were significantly higher in the TW with cork. • The contribution of Acidobacteria and Planctomyces microorganism communities were superior in the TW with gravel • Cork treatment wetlands could be appropriate to treat nitrate polluted groundwater from agricultural activities. [ABSTRACT FROM AUTHOR]

The Environmental Protection Agency of the Campania region in Italy (ARPAC) manages a groundwater quality monitoring network. For almost all the polluted waters, the key parameter driving the classification is the concentration of nitrate; hence, the Campania region, in coherence with the EU regulations, outlined the vulnerable areas and undertook remediation policies. The best groundwater quality is recorded for carbonate aquifers of the Apennine chain; on the contrary, the Tyrrhenian coastal plains are affected by severe contamination, with a locally very contaminated groundwater of the shallow and also the deeper aquifers. The study is especially focused on a large coastal plain of Campania region, where nitrate concentration sometimes exceeds 200 mg/L. The study, based on almost 200 sampling points for the whole region during the period 2003-2015 (approx two samples per year), verified the effectiveness of the groundwater monitoring network, the present distribution of nitrate in groundwater, and the evolution of nitrate trends at different scales: regional, groundwater body, and single well, using spatial and time series statistical approaches. Significant variations in contamination evolution within the study area have been observed and the correlation with land use has been highlighted. [ABSTRACT FROM AUTHOR]

Abstract Although ubiquitous elements of agricultural landscapes, the interest on ditches and canals as effective filters to buffer nitrate pollution has been raised only recently. The aim of the present study was to investigate the importance of in-ditch denitrification supported by emergent aquatic vegetation in the context of N budget in agricultural lands of a worldwide hotspot of nitrate contamination and eutrophication, i.e. the lowlands of the Po River basin (Northern Italy). The effectiveness of N abatement in the ditch network (>18,500 km) was evaluated by extrapolating up to the watershed reach-scale denitrification rates measured in a wide range of environmental conditions. Scenarios of variable extents of vegetation maintenance were simulated (25%, 50% and 90%), and compared to the current situation when the natural development occurs in only 5% of the ditch network length, subjected to mechanical mowing in summer. Along the typical range of nitrate availability in the Po River lowlands waterways (0.5–8 mg N L−1), the current N removal performed by the ditch network was estimated in 3300–4900 t N yr−1, accounting for at most 11% of the N excess from agriculture. The predicted nitrate mitigation potential would increase up to 4000–33,600 t N yr−1 in case of vegetation maintenance in 90% of the total ditch length. Moreover, a further significant enhancement (57% on average) of this key ecosystem function would be achieved by postponing the mowing of vegetation at the end of the growing season. The simulated outcomes suggest that vegetated ditches may offer new agricultural landscape management opportunities for effectively decreasing nitrate loads in surface waters, with potential improved water quality at the watershed level and in the coastal zones. In conclusion, ditches and canals may act as metabolic regulators and providers of ecosystem services if conservative management practices of in-stream vegetation are properly implemented and coupled to hydraulic needs. Graphical abstract Unlabelled Image Highlights • The role of ditch networks in watershed-scale N-NO 3 − mitigation remains understudied. • N-NO 3 − removal rates were scaled-up to the ditch network of the Po River lowlands. • In-ditch denitrification was assessed in the context of agricultural N surplus. • In-stream vegetation maintenance may efficiently control agricultural N excess. • Predictive tools and management guidelines are needed to maximize ditch N removal. [ABSTRACT FROM AUTHOR]

This paper examines the interaction of different policies used to control two types of agricultural pollution. Pollution control policy is efficient when both pollution types are controlled by taxes, although a tax increase on one type of pollution can increase the quantity of another type of pollution if farm inputs are substitutes. However, if one of the pollutions is controlled by a local emissions trading scheme, and another pollution type is taxed, then the pollution type which is taxed becomes less responsive to a change in its own tax levels. This policy scenario results in inefficient levels of environmental pollution outcomes unless the cap for the local emissions trading scheme is constantly being shifted in response to the tax. [ABSTRACT FROM AUTHOR]

This study aims to modify the SINTACS and DRASTIC models with a land-use (LU) layer and compares the modified-DRASTIC, modified-SINTACS and SI methods for groundwater vulnerability assessment (GVA) in the southern Tehran aquifer, Iran. Single parameter sensitivity analysis (SPSA) served to determine the most significant parameters for the modified-DRASTIC, modified-SINTACS and SI approaches, and to revise model weights from "theoretical" to "effective." The inherent implementation of LU in the SI model may explain its better performance compared to unenhanced versions of DRASTIC and SINTACS models. Validation of all models, using nitrate concentrations from 20 wells within the study area, showed the modified-SINTACS model to outperform other models. The SPSA showed that the vadose zone and LU strongly influenced the modified-DRASTIC and modified-SINTACS models, while SI was strongly influenced by aquifer media and LU. To improve performance, models were implemented using "effective" instead of "theoretical" weights. Model robustness was assessed using nitrate concentrations in the aquifer and the outcomes confirmed the positive impact of using "effective" versus "theoretical" weights in the models. Modified-SINTACS showed the strongest correlation between nitrate and the vulnerability index (coefficient of determination = 0.75). Application of the modified-SINTACS while using "effective" weights, led to the conclusion that 19.6%, 55.2%, 23.4%, and 1.6% of the study area housed very high, high, moderate and low vulnerability zones, respectively. [ABSTRACT FROM AUTHOR]

This research was carried out to delineate the spatial distribution of shallow groundwater quality in Yan'an City, an important cultural city on the Chinese Loess Plateau, and to estimate the health risks induced by nitrate exposure in drinking water in this city. For this study, 36 shallow groundwater samples were collected from shallow pumping wells/dug wells. The entropy-weighted water quality index (EWQI) was used to evaluate the overall groundwater quality, and the spatial distribution of the groundwater quality was discussed. The potential health hazards due to nitrate intake through drinking water were also assessed. The results of the study demonstrate that the main hydrochemical facies are governed by natural processes and anthropogenic activities. Over half of the groundwater samples require treatment of different degrees before being consumed. TH, TDS, SO42–, and NO3– are the most prevalent contaminants affecting the groundwater quality in this area. Poor-quality water is prevalent in the region along the main river. Residents in almost half of the study area face noncarcinogenic health risks with children being the more susceptible group to groundwater nitrate contamination. Reducing the concentration of NO3– in drinking water by regulating excessive fertilizer application and issuing regulations supervising the domestic sewage are important to reduce the health risks. Integrated management of groundwater and surface water as well as rainwater is recommended for the groundwater quality management. [ABSTRACT FROM AUTHOR]

Nitrate pollution in surface water has become an environmental problem of global concern. The effective way for controlling the nitrate pollution of surface water is to identify the pollution source and reduce the input of nitrate. In recent decades, nitrogen (δ15N) and oxygen (δ18O) isotopes of nitrate has been used as an effective approach for identifying the source and fate of nitrate pollution in surface water. However, owing to the complexity of nitrate pollution source and the influence of isotopic fractionation, the application of this method has some limitations. In this work, we systematically discussed the fundamental principle of using nitrogen and oxygen isotopes to trace the nitrate source, the fate identification of nitrate, and the major testing techniques. Subsequently, the applications of nitrogen and oxygen isotopes for source identification of surface water were illustrated. However, there are still significant gaps in the application of the source identification and transformation mechanisms to nitrate and many research questions on these topics need to be addressed. [ABSTRACT FROM AUTHOR]

Nitrate pollution in groundwater is a serious problem in Shimabara Peninsula, Nagasaki, Japan. A better understanding of the hydrogeochemical evolution of groundwater in vulnerable aquifers is important for health and environment. In this study, groundwater samples were collected at 12 residential and 57 municipal water supply wells and springs in July and August 2018. Nitrate (NO3−N) concentration at eight sampling sites (12%) exceeded Japanese drinking water standard for NO3 + NO2−N (10 mg L−1). The highest nitrate concentration was 19.9 mg L−1. Polluted groundwater is distributed in northeastern, northwestern, and southwestern areas, where land is used for intensive agriculture. Correlation analysis suggests that nitrate sources are agricultural fertilizers and livestock waste. Dominant groundwater chemistry is (Ca+Mg)−HCO3 or (Ca+Mg)−(SO4+NO3) type. Groundwater with higher nitrate concentration is of (Ca+Mg)−(SO4+NO3) type, indicating nitrate pollution affecting water chemistry. Principal component analysis extracted two important factors controlling water chemistry. The first principal component explained dissolved ions through water–rock interaction and agricultural activities. The second principal component explained cation exchange and dominant agricultural effects from fertilizers. Hierarchical cluster analysis classified groundwater into four groups. One of these is related to the dissolution of major ions. The other three represent nitrate pollution.

Overuse or mistimed application of nitrogen fertilizer can cause nitrate contamination in groundwater and surrounding surface waters. Previous greenhouse studies have explored the use of graphene nanomaterials, including graphite nano additive (GNA), to reduce nitrate leaching in an agricultural soil while growing lettuce crops. To investigate the mechanism of GNA addition in suppressing nitrate leaching, we conducted soil column experiments using native agricultural soils under saturated or unsaturated flow conditions to simulate varied irrigation. We investigated the effects of temperature (4 °C compared with 20 °C) on microbial activity and dose effect of GNA was also explored (165 mg/kg soil and 1650 mg/kg soil) for biotic soil column experiments whereas a single temperature condition (20 °C) and GNA dose (165 mg/kg soil) was employed for abiotic (autoclaved) soil column experiments. Results showed GNA addition had minimal effects on nitrate leaching in saturated flow soil columns due to short hydraulic residence times (∼3.5 h). In comparison, longer residence times (∼3 d) in unsaturated soil columns reduced nitrate leaching by 25–31% relative to control soil columns without GNA addition. Furthermore, nitrate retention in the soil column was found to be suppressed at 4 °C compared with 20 °C, suggesting a bio-mediated mechanism for GNA addition to reduce nitrate leaching. In addition, the soil dissolved organic matter was found to be associated with nitrate leaching, where less nitrate leaching occurring when higher dissolved organic carbon (DOC) was measured in leachate water. Following studies of adding soil-derived organic carbon (SOC) resulted in greater nitrogen retention in the unsaturated soil columns only when GNA was present. Overall, the results suggest that GNA-amended soil reduces nitrate loss through increased N immobilization in the microbial biomass or loss of N in gaseous phase through enhanced nitrification and denitrification process. [Display omitted] • Graphene nanomaterials (GNA) added with fertilizers to soil reduced nitrate leaching by up to 31%. • Higher temperatures and GNA addition reduced nitrate leaching, indicating an important biological mediated mechanism. • Solubilization of soil organic matter plays a crucial role in preventing nitrate leaching. • GNA-amended soil enhance nitrogen retention through microbial processes, reducing nitrate loss significantly. [ABSTRACT FROM AUTHOR]

The groundwater quality is severely impacted by Nitrate (NO 3 −-N) pollution worldwide. Effective lake quality management depends on understanding the origin and fate of nitrogen (N) in the groundwater around lakes. This study combined data for multiple stable isotopes (δ2H–H 2 O and δ18O–H 2 O, δ15N–NO 3 and δ18O–NO 3) and hydrochemistry with the hydrodynamic monitoring profile and a Bayesian isotope mixing (MixSIAR) model to clarify the sources and transformation of N within shallow groundwater around Shahu Lake in the arid area plain of Northwest China. In May 2022, multiple water samples were collected from aquifers (n = 33), drainage water (n = 1), channel water (n = 1), and lake water (n = 7). The results showed that 57% of groundwater samples had high NO 3 −-N concentrations exceeding the World Health Organisation threshold for drinking water (10 mg/L). The high variation in δ15N–NO 3 (from −9.21‰ to +27.57‰) and δ18O–NO 3 (from −8.32‰ to +19.04‰) revealed multiple N sources and conversion processes. According to nitrate isotopes and the MixSIAR model, N fertilizer, soil organic N and manure, and sewage are the main sources of nitrogen in groundwater and lake water, which account for 40.61%, 35.86%, and 21.55% of groundwater NO 3 −-N, respectively, and 35.07%, 34.43%, and 27.49% of lake water NO 3 −-N. Hydrodynamic monitoring combined with water isotopes showed that upper groundwater (5–10 m) within 1.22 km of the adjacent lake shore strongly interacted with the lake. In groundwater, nitrification predominated, while local denitrification remained a possibility. In conclusion, this research offers a comprehensive approach to determining the sources and conversion of N in contaminated groundwater. [Display omitted] • 57% groundwater exceed NO 3 −-N concentration of 10 mg/L of drinking water threshold. • N fertilizer was the main sources of N in groundwater and lake water. • Nitrification was the dominant N conversion process in groundwater. [ABSTRACT FROM AUTHOR]

Overfertilization prevails in developing apple-producing countries, but its long-term effects on regional water resources are scarcely documented. In this study, a total of 114 water samples, including groundwater, river water, and tap water, were collected from rainfed and irrigated apple-planting regions on China's Loess Plateau. The primary objectives were to (1) systematically evaluate changes in hydrochemistry using hydrochemical indices and major ion ratios, (2) quantify NO 3 −-N pollution and its driving factors using δ15N- and δ18O-labeled nitrate and a Bayesian isotope mixing model (MixSIAR), and (3) identify water suitable for drinking using an entropy water quality index and for irrigation by integrating electrical conductivity and Na%. All water samples contained Ca-Mg-HCO 3 facies, except for low-elevation water samples in the irrigated region with Na-HCO 3 facies. Hydrochemistry changed considerably from the 2000–2020 s in both rainfed and irrigated regions, primarily associated with agricultural activities (e.g., fertilization). Although absent in the rainfed region, NO 3 −-N pollution was severe in the irrigated region, with 40.0 % of tap water, 25.0 % of river water, and 32.7 % of groundwater samples exceeding the World Health Organization limit of 10 mg L−1. MixSIAR indicated the contribution of chemical fertilizer to NO 3 − was higher in irrigated than in rainfed regions, regardless of the water source. With the exception of sewage/manure-derived NO 3 –-N in the rainfed region's groundwater, chemical fertilizer was the highest contributor to NO 3 −-N in river water and groundwater, whereas sewage/manure was the most important nitrate source in tap water, whether irrigated or rainfed region. Regression analysis revealed N-fertilizer inputs and water level and well depths were key factors affecting groundwater NO 3 −-N in the irrigated region compared with those in the rainfed region. Notably, all water samples in the rainfed region were suitable for drinking and irrigation, whereas in the irrigated region, 27.3 % of groundwater samples were unsuitable for drinking and 40.0 % of tap water, 75.0 % of river water, and 63.6 % of groundwater samples were doubtful-to-unsuitable for irrigation. Collectively, overfertilization in long-term apple cultivation changed regional hydrochemistry, with flood irrigation aggravating nitrate pollution and water degradation. The study provides new insights into optimum water–nitrogen management of apple production systems in China and other developing countries with similar problems. [Display omitted] • Long-term apple production affected water–rock interactions at a regional scale. • Changes in regional hydrochemistry were mainly associated with overfertilization. • Nitrate pollution was more severe in irrigated than rain-fed regions. • Chemical fertilizer led to NO 3 −-polluted groundwater in the irrigated region. • Overfertilization and flood irrigation combined to markedly degrade water quality. [ABSTRACT FROM AUTHOR]

A significant rise of groundwater pollution has been registered worldwide, where nitrate has been recognized as the most widespread pollutant. In this context, the groundwater vulnerability assessment and more specifically the delineation of “Nitrate Vulnerable Zones” represents a reliable cost-effective tool for groundwater management. In this study, the Agricultural Nitrate Hazard Index (ANHI) method was applied to two case histories in southern Italy: the Lete River catchment and the eastern sector of the Campania Plain. The first area is characterized by agricultural activities and a low anthropic influence while the eastern part of the Campania Plain, around Caserta city, is strongly urbanized and developed on an extensive alluvial plain filled with volcaniclastic deposits. The parametric method applied suggests moderate hazard for the more natural setting highlighting how the intensive crop farming and livestock activities that characterized the area negatively influenced the results. For the eastern part of the Campania Plain, where a strong urbanization and widespread industrial crops are dominant, a low to very low hazard has been identified. The groundwater quality value, in contrast with the methodology results underlines the importance of further risk evaluations based on accurate aquifer characterization. A multiple year assessment based on land use change and climate variation could further highlights the difference between the study areas.

Nitrate pollution remains an unsolved issue worldwide, causing serious effects on water quality and eutrophication of freshwater and brackish water environments. Its economic costs are still underestimated. To reduce nitrogen excess, constructed wetlands are usually recognized as a solution but, in recent years, interest has been raised in the role of ditches and canals in nitrogen removal. In this study, we investigated the environmental and economical sustainability of nitrogen removal capacity, using as a model study a lowland agricultural sub-basin of the Po River (Northern Italy), where the role of aquatic vegetation and related microbial processes on the mitigation of nitrate pollution has been extensively studied. Based on the Life Cycle Assessment (LCA) approach and costs and benefits analysis (CBA), the effectiveness of two different scenarios of vegetation management, which differ for the timing of mowing, have been compared concerning the nitrogen removal via denitrification and other terms of environmental sustainability. The results highlighted that postponing the mowing to the end of the vegetative season would contribute to buffering up to 90% of the nitrogen load conveyed by the canal network during the irrigation period and would reduce by an order of magnitude the costs of eutrophication potential.

The Gaza Strip is in a chronic state of water shortage and the coastal aquifer as the only freshwater source is increasingly depleted and polluted, especially by nitrate. Assessment of groundwater vulnerability to pollution is essential for adequate protection and management. In this study, the assessment of the aquifer vulnerability to contamination is derived by applying the DRASTIC procedure, firstly with original default weights and ratings and, secondly, improved by estimating rating values by multiple linear regression of observed log-transformed nitrate concentration in groundwater, with DRASTIC factors extended to land-use. The results are very different because high and low vulnerability areas shift considerably. Subsequently, a geostatistical analysis of the spatial distribution of the nitrate concentration is performed, firstly by ordinary kriging interpolation of the observed nitrate concentration and secondly by regression kriging using DRASTIC factors and land-use as indicators of the spatial variation in nitrate occurrence. These maps differ because the map obtained by regression kriging interpolation shows much more details of environmental factors such as dunes, ridges, soil types and built-up areas that affect the presence of nitrate in groundwater. The results of this study can be used by the Palestinian authorities concerned with sustainable groundwater management in the Gaza Strip.

Although representing a paramount mechanism against nitrogen excess in agricultural landscapes, soil denitrification is still a largely unknown term in nitrogen balances at the watershed scale. In the present work, a comprehensive investigation of nitrogen sources and sinks in agricultural soils and waters was performed with the aim of gaining insights into the relevance of soil denitrification in a highly farmed sub-basin of the Po River delta (Northern Italy). Agricultural statistics, water quality datasets, and results of laboratory experiments targeting nitrogen fluxes in soils were combined to set up a detailed nitrogen budget along the terrestrial−freshwater continuum. The soil nitrogen budget was not closed, with inputs exceeding outputs by 72 kg N·ha−1·year−1, highlighting a potential high risk of nitrate contamination. However, extensive monitoring showed a general scarcity of mineral nitrogen forms in both shallow aquifers and soils. The present study confirmed the importance of denitrification, representing ~37% of the total nitrogen inputs, as the leading process of nitrate removal in heavily fertilized fine-texture soils prone to waterlogged conditions.

The protection of water resources and development of mitigation strategies require large-scale information on water pollution such as nitrate. Machine learning techniques like random forest (RF) have proven their worth for estimating groundwater quality based on spatial environmental predictors. We investigate the potential of RF and quantile random forest (QRF) to estimate redox conditions and nitrate concentration in groundwater (1 km × 1 km resolution) using the European Water Framework Directive groundwater monitoring network as well as spatial environmental information available throughout Germany. The RF model for nitrate achieves a good predictive performance with an R ^2 of 0.52. Dominant predictors are the redox conditions in the groundwater body, hydrogeological units and the percentage of arable land. An uncertainty assessment using QRF shows rather large uncertainties with a mean prediction interval (MPI) of 53.0 mg l ^−1 . This study represents the first nation-wide data-driven assessment of the spatial distribution of groundwater nitrate concentrations for Germany.

Shallow aquifers of coastal and internal alluvial plains of developed countries are commonly characterized by the challenging management of groundwater resources due to the intense agricultural and industrial activities that determine a high risk of groundwater contamination. Among the principal origins of pollution in these areas are agricultural practices based on the amendment of soils by nitrate fertilizers, which have been recognized as one of the most severe environmental emergencies for which specific policies and regulations have been issued (e.g., EU Directive 2006/118/EC). In such a framework, the results of research aimed at assessing the specific vulnerability of shallow alluvial aquifers to nitrate fertilizer pollutants by coupled process-based and empirical approaches are here proposed. The research focused on assessing the specific vulnerability to nitrate pollution of a shallow alluvial aquifer of the Campania region (southern Italy), which was selected due to its representativeness to other recurrent hydrogeological settings occurring in alluvial plains of the region and worldwide. In this area, 1D hydro-stratigraphic models of the unsaturated zone were reconstructed and applied for simulating the transport of nitrate pollutants at the water table and estimating the associated travel times. Numerical modeling was carried out by the finite differences VS2TDI code and considered a 10-year time series of rainfall and evapotranspiration as well as typical local farming practices of nitrate fertilizer input. Results of the travel time calculated for the 1D hydro-stratigraphic models considered and at different depths were recognized as a proxy to assess the specific vulnerability to nitrate fertilizer pollution. Among the principal outcomes is an empirical multiple correlation between the travel time of the nitrate fertilizer pollutant, water table depth, and equivalent saturated hydraulic conductivity of the unsaturated zone or hydraulic resistance, which was used to assess the travel time at the distributed scale over the whole area studied as well as the related specific vulnerability. Given such results, the coupled process-based and empirical approach is proposed as generally applicable for assessing and mapping groundwater vulnerability in shallow aquifers, for which detailed stratigraphic and piezometric data are available.

Irrigation, one of the 28 agri-environmental indicators defined in the European Common Agricultural Policy, is often neglected in agricultural nitrogen (N) budgets, while it can be a considerable source of N in irrigated agriculture. The annual N input from irrigation water sources (NIrrig) to cropping systems was quantified for Europe for 2000-2010 at a resolution of 10 × 10 km, accounting for crop-specific gross irrigation requirements (GIR) and surface- and groundwater nitrate concentration. GIR were computed for 20 crops, while spatially explicit nitrate concentration in groundwater was derived using a random forest model. We show that although GIR were relatively stable (46-60 km3 yr-1), the Nirrig in Europe increased over the 10-year period (184 to 259 Gg N yr-1), approximately 68 % of which occurred in the Mediterranean region. The main hotspots appeared in areas with both high irrigation requirements and high groundwater nitrate concentration, reaching up to averaged values of 150 kg N ha-1 yr1. These were mainly located in Mediterranean Europe (Greece, Portugal and Spain) and to a lesser extent in Northern Europe (The Netherlands, Sweden and Germany). By not including NIrrig, environmental and agricultural policies are underestimating the real extent of N pollution hotspots in European irrigated systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Nitrate (NO 3 - ) 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 NO 3 - 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 (N 2 ) via the action of several bacteria species. The WBR has been suggested as one of the most cost-effective NO 3 - -removing strategy among several edge-of-field practices, and has been shown to successfully remove NO 3 - in several field studies. NO 3 - removal in the WBR primarily occurs via the activity of denitrifying microorganisms via enzymatic reactions sequentially reducing NO 3 - to N 2 . 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 NO 3 - pollution cases originating from intensive farming practices and N-cycling microbial metabolisms which is one biological solution to remove NO 3 - from agricultural wastewater. Moreover, here we review the current knowledge on the physicochemical and operational factors affecting microbial metabolisms resulting in removal of NO 3 - in WBR, and perspectives to enhance WBR performance in the future., (© 2023. The Author(s), under exclusive licence to Microbiological Society of Korea.)

Highlights • The first study was carried out to show how setting WF benchmarks may help alleviate groundwater scarcity and pollution. • Iran's groundwater will be saved by 32% when reducing WFs of crops to 25th percentile benchmark levels. • Nitrogen-related grey ground WF will be lowered by 23% through setting WF benchmarks. • A significant increase in economic groundwater productivity is acheived when setting benchmark levels at 25th percentile. • The introduced methodology here is a promising way to alleviate overexploitation of aquifers and increase national food security. Abstract The formulation of water footprint (WF) benchmarks in crop production – i.e. identifying reference levels of reasonable amounts of water consumption and pollution per tonne of crop produced – has been suggested as a promising strategy to counter inefficient water use and pollution. The current study is the first to show how setting WF benchmarks may help alleviate groundwater scarcity and pollution, in a case study for Iran. We advance the field of WF assessment by developing WF benchmark levels for crop production, which we successively use to assess potential groundwater saving, quality improvement and economic water productivity gains. First, we calculate climate-specific WF benchmark levels for both total blue water footprints and nitrogen-related grey groundwater footprints for 26 crops, for all years in the period 1980–2010, at 5 × 5′ spatial resolution. Second, we estimate the water saving potential for total blue water resources and for groundwater resources specifically, as well as the grey groundwater footprint reduction potential. Finally, we compare mean economic water productivities of crop production in the past with productivities if WFs are reduced to benchmark levels. We find that groundwater comprises up to 83% of total blue water consumption of irrigated crops, with the highest share in arid areas and in cereals. Aquifers are under significant to severe stress, except in the dry sub-humid zone, where irrigation mainly relies on surface water. Reducing WFs of crops to 25th percentile benchmark levels can save 32% of groundwater compared to the reference year 2010, and lower the nitrogen-related grey groundwater footprint by 23%. Moreover, it would increase average economic groundwater productivity in Iran by 20% for cereals, and 59% for nuts. We conclude that reducing WFs to climate-specific benchmark levels in a water-stressed country is a promising way to alleviate overexploitation of aquifers and increase national food security. [ABSTRACT FROM AUTHOR]

Distributed models and a good knowledge of the catchment studied are required to assess mitigation measures for nitrogen (N) pollution. A set of alternative scenarios (change of crop management practices and different strategies of landscape management, especially different sizes and distribution of set-aside areas) were simulated with a fully distributed model in a small agricultural catchment. The results show that current practices are close to complying with current regulations, which results in a limited effect of the implementation of best crop management practices. The location of set-aside zones is more important than their size in decreasing nitrate fluxes in stream water. The most efficient location is the lower parts of hillslopes, combining the dilution effect due to the decrease of N input per unit of land and the interception of nitrate transferred by sub-surface flows. The main process responsible for the interception effect is probably uptake by grassland and retention in soils since the denitrification load tends to decrease proportionally to N input and, for the scenarios considered, is lower in the interception scenarios than in the corresponding dilution zones. [ABSTRACT FROM AUTHOR]

In recent years DRASTIC method has been used to map groundwater vulnerability to pollution in very areas. As this method is used in different places without any evolution, it cannot bring up the effects of pollution type and characteristics. Hence, the method needs to be calibrated and reformed for a specific aquifer and pollution. In the present resent research, the rates of DRASTIC parameters have been reformed so that the vulnerability potential to pollution can be determine more exactly. The new rates were calculated using the relationships between each parameter and the nitrate concentration in the groundwater. The suggested methodology was applied to Asadabad aquifer located in western of Iran. The measured nitrate condensation values were used to correlate the pollution potential in the aquifer to DRASTIC index. The results showed that the modified DRASTIC is better than the original method for nonpoint source pollutions in agricultural zones. Application of the new rates, a new DRASTIC map was expanded that shows that 2.1 percent of the area fall in high vulnerability class. This percentage was 2.5 before the modification. The assessed area was 34.2% and 58.19% for moderate class and, for low vulnerability class, 63.7% and 31.39% respectively, before and after using of the new rates. [ABSTRACT FROM AUTHOR]

Nitrate (NO 3 − ) pollution in rivers caused by intensive human activities is becoming a serious problem in irrigated agricultural areas. To identify NO 3 − sources and reveal the impact of irrigation projects on NO 3 − pollution in rivers, the hydrochemistry and isotopes of irrigation water from the Yellow River (IW) and river water (RW), and potential source samples were analyzed. The mean NO 3 − concentrations in the IW and RW were 24.4 mg/L and 49.9 mg/L, respectively. Approximately 45.2% of RW samples (n = 31) exceeded the Chinese drinking water standard for NO 3 − (45 mg/L). The δ 15 N and δ 18 O values, combined with the Cl − /Na + , SO 4 2− /Ca 2+ ratio distributions, indicate that the NO 3 − in the RW mainly originated from chemical fertilizers, manure and sewage. A Bayesian model showed that manure and sewage contributed the most to the overall NO 3 − levels of the IW. In the RW, chemical fertilizers and IW contributed the most to the overall NO 3 − levels. The mean nitrate contribution to the RW from the combination of chemical fertilizers and IW is estimated to be 51.6%. Nitrogen from manure and sewage, soil N and precipitation also contributed. The NO 3 − pollution in rivers was largely influenced by the irrigation regime, with a large amount of nitrogen in chemical fertilizer lost because of low utilization efficiency and subsequent transfer, via irrigation runoff, into the rivers. This study suggests that with a detailed assessment of the sources and fate of NO 3 − , effective reduction strategies and better management practices can be implemented to control NO 3 − pollution in rivers. [ABSTRACT FROM AUTHOR]

The Wudalianchi scenic area in NE China has been named an UNESCO “Global Geopark” and “Biosphere Reserve.” During this investigation, the sources of nitrate and the hydrologic system through which it is dispersed were assessed using geochemical data and a multiple isotopic approach. The cold waters from the south and north springs originated from the deep subsurface. Isotopically, these waters exhibited relatively negative δD and δ18O values and nitrate in the water was substantially depleted 15N, suggesting that the mineral water was primarily derived from depth. Lakes within the Wudalianchi region were primarily composed of water from these deep mineral springs and precipitation. Chemical fertilizers were the primary source of nitrate to the Wudalianchi lakes. Groundwater was found in shallow mineral springs and wells plotted above the local meteoric water line, implying that shallow groundwater was primarily derived from precipitation. Elevated concentrations of nitrate in shallow mineral springs and well waters during the summer, autumn, and winter suggest that shallow groundwater within the Yaoquan volcanic area was also polluted by nitrate from human activities. Denitrification of shallow groundwater is slow, reducing the potential for “self-remediation”. The concentration data are supported by nitrogen (N) isotope data; wells and springs exhibited N isotopic ratios between − 5‰ and + 5‰ (typical of fertilizers and precipitation) and exhibited higher oxygen (O) isotope values than water in the Wudalianchi lakes. These relationships suggest that nitrate in shallow mineral springs, wells, and lakes near the Yaoquan volcano was derived from the mixing of chemical fertilizers with local summer rainfall. [ABSTRACT FROM AUTHOR]

The EU directive has addressed ambitious targets concerning the quality of water bodies. Predicting water quality as affected by land use and management requires using dynamic agro-hydrogeological models. In this study, an agronomic model (STICS) and a hydrogeological model (MODCOU) have been associated in order to simulate nitrogen fluxes in the Seine-Normandie Basin, which is affected by nitrate pollution of groundwater due to intensive farming systems. This modeling platform was used to predict and understand the spatial and temporal evolution of water quality over the 1971-2013 period. A quality assurance protocol (Refsgaard et al. Environ Model Softw 20: 1201-1215, 2005) was used to qualify the reliability of STICS outputs. Four iterative runs of the model were carried out with improved parameterization of soils and crop management without any change in the model. Improving model inputs changed much more the spatial distribution of simulated N losses than their mean values. STICS slightly underestimated the crop yields compared to the observed values at the administrative district scale. The platform also slightly underestimated the nitrate concentration at the outlet level with a mean difference ranging from −1.4 to −9.2 mg NO3 L−1 according to the aquifer during the last decade. This outcome should help the stakeholders in decision-making to prevent nitrate pollution and provide new specifications for STICS development. [ABSTRACT FROM AUTHOR]

High levels of nitrates in groundwater pose a risk to human health. Hence, groundwater-human health risk assessment and sources analysis are essential. The article aims to assess risk level and identify sources of nitrate in shallow groundwater of the Liujiang basin by using a human health risk assessment (HHRA) model, Factor analysis (FA) and GIS spatial analysis. The results indicated that the most serious pollution was distributed in southern region of the basin; about 60% of the samples exceeded the recommended limit of nitrate as per the World Health Organization limit. Moreover, ingants' health risk were greater than those of adults and children, and about 56% of the groundwater samples will put the infants at risk of health. FA was used to identify various underlying natural and anthropogenic processes that created these distinct risk levels. The FA results can be categorized by two major factors: (1) Organic fertilizers and sewage discharge contamination in central region. (2) Blocking effect of granite and redox conditions in southern parts. This study demonstrates that the great variation of nitrate risk levels in the basin should be attributed to both natural and anthropogenic processes. [ABSTRACT FROM AUTHOR]

Exploring how land use change (LUC) influences the amount and quality of recharge water is important for groundwater sustainability and land use planning. With loess of up to 200 m in thickness and unsaturated zones up to 100 m below the surface, the loess tablelands in China can store abundant groundwater resources. However, groundwater depletion and substantial LUC have been simultaneously observed. It is thus necessary to investigate the relationship between LUC and groundwater. We sampled 10-m soil profiles for three land use types (farmlands, apple orchards of 10 and 20 years old). After measuring the chloride and nitrate concentration in soil pore water, the LUC effects on the amount and quality of recharge water quality were quantified based on the mass balance method. Results showed that soil moisture in aged (20-year-old) apple orchards was significantly reduced relative to that measured in farmlands and younger (10-year-old) orchards, where measured soil moistures were roughly equal. The accumulated nitrate‑nitrogen and the depth below which nitrate is stable was smallest in farmlands, intermediate in 10-year-old apple orchards, and largest under 20-year-old apple orchards. The diffuse recharge was 33.0 ± 17.9 mm year −1 , accounting for 7.3 ± 1.8% of mean annual precipitation under farmlands; however, the conversion from farmlands to 20-year-old apple orchards reduced recharge by 42%. The nitrate infiltrating to groundwater annually was 4.9 ± 2.9 kg hm −2 and 4.1 ± 3.1 kg hm −2 under farmlands and 20-year-old apple orchards, respectively. The impacts of LUC over the past decades have not yet reached groundwater because of low recharge rates; further, the primary factor influencing groundwater quality is recharge rate rather than pollutant concentration. As such, the LUC from farmland to apple orchard has little impact on short-term groundwater recharge and quality; long term impact, however, may be significant. [ABSTRACT FROM AUTHOR]

Yangzhuang basin is rich in groundwater resources. In recent years, the nitrate pollution of groundwater in the basin has been aggravating. Based on the Visual Modflow, the numerical model of groundwater flow- and solute transport in the basin was established, the nitrate migration and diffusion in groundwater at Yangzhuang fault block were simulated by this model which predicted the distribution of nitrate in groundwater and the variation trend of concentration after 5a and 10a.The predicted results show that the nitrate concentration in groundwater presents an obviously rising trend through the forecast period and the high nitrate concentration areas are mainly distributed in Lulujing. Under the influence of groundwater flow direction, the high nitrate concentration area mainly extends toward the southwest. The continuous increase of nitrate concentration in groundwater of Yangzhuang basin is mainly caused by farmers' excessive use of nitrogen fertilizer and the random discharge waste water from farms. [ABSTRACT FROM AUTHOR]