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Nitrate pollution in groundwater and related human health risk assessment are crucial to ensure groundwater quality safety. In this study, the grey water footprint (GWF), DRASTIC model, and human health risk assessment (HHRA) model were used to investigate the status of nitrate pollution, analyze the effect of hydrogeological conditions on groundwater nitrate pollution, and evaluate the human health risk of nitrate in the Jiaokou Irrigation District, China. The results show that the maximum and average NO 3 − concentrations in the Jiaokou Irrigation District were 895 and 170.73 mg/L and the over-standard rate (>20 mg/L) was over 80% (82.09%). High NO 3 − concentration was mainly distributed in the cultivated land. The GWF results indicate that the wastewater absorption was insufficient to bear actual pollution in this region, requiring freshwater between 0.1 × 108 m3 and 105.8 × 108 m3 to dilute the nitrate to a safe concentration. The aquifers with high vulnerability levels were observed in the central and eastern parts, which are mainly related to depth to water table (D), net recharge (R), soil media (S), impact of vadose zone (I), and hydraulic conductivity (C). High NO 3 − pollution in an area is generally caused by high aquifer vulnerability. Additionally, the human health risk assessment shows that the health risks for pregnant women and breastfeeding women were higher than the health risks for children in the 10–16 years age group and > 16 years of age. This research provides a basis for policy-makers to take appropriate measures for protecting groundwater from nitrate pollution. [Display omitted] • GWF and WPL values indicates the study area has serious nitrate pollution with a maximum of 895 mg/L. • Aquifer vulnerability and its impact on groundwater nitrate pollution were assessed using DRASTIC model. • High nitrate pollution occurs in the central part of study area with high aquifer vulnerability. • Non-carcinogenic health risks of nitrate to different age groups were evaluated using HHRA model. • This study draws attention to the management of high nitrate groundwater to achieve sustainable development. [ABSTRACT FROM AUTHOR]

In face of the interdependencies between policy areas in the management of common pool resources, studying nexus challenges is insightful for the exploration of new governance strategies. This includes the co-occurrence of and the interaction between different governance modes. We put forward the argument that a promising approach to explore these dynamics over time is the method of discourse network analysis. By conducting a discourse network analysis of German agricultural and water policy in a region with intensive livestock farming and large surpluses of manure that exert pressure on water and soil resources, we analyse the development of discourses within and across policy areas. We show that the analysis of public discourses contributes to the understanding of coordination between actors. • The separation of policy areas presents a major challenge to the sustainable management of common pool resources. • The analysis of public discourses enables a new perspective on governance types beyond the trichotomy of cooperation, competition and coercion. • Hybrid governance strategies going beyond the analytical distinction between government, market and community have proven successful for sustainable environmental management. • External pressure leads to the rapprochement of discourse coalitions. [ABSTRACT FROM AUTHOR]

Water quality is an increasing concern in the dry regions of the world as it affects and reduces the quantity of available water. Our objective was to investigate the sources, drivers, spatiotemporal patterns of nitrate‑nitrogen (NO 3 –N) transport in the streamwater and groundwater in a dry and a wet season in seven large rivers located in the Loess Plateau of China (640,000 km2, 100 million population), which is a region with marked influence of human activities on streamflow and groundwater. We collected 510 streamwater and groundwater samples and found that NO 3 –N was significantly lower in the dry season (< 5.0 mg L−1) than the wet season (> 5.0 mg L−1). In the wet season, NO 3 –N was lower in the streamwater than groundwater; however, the spatial variation in the NO 3 –N was greater in streamwater, with higher concentrations in two rivers (Wei and Fen). The source characterization using stable isotopes of NO 3 from the Wei River showed that chemical N fertilizers and soil organic N contributed ~ 75% of NO 3 to streamwater and that soil organic N was the greatest contributor of NO 3 to groundwater (~ 60%) than streamwater (< 40%). The spatial pattern of NO 3 –N was dominated by fertilizer application and varied seasonally with rainfall-runoff and streamflow-groundwater connectivity. Our results showed the complicated patterns and sources of NO 3 pollution in streamwater and groundwater and highlight that more emphasis should be placed to prevent and restore the degraded water quality in the dry regions. Unlabelled Image • Wet-season nitrate contents in waters were higher than the dry season. • The spatial pattern of nitrate transport was controlled by land use structure. • Seasonality of hydrologic cycle influenced temporal variation in nitrate loss. • Major sources of nitrate in waters were chemical fertilizer and soil organic N. • Limited water quantity in the dry region was further reduced by water pollution. [ABSTRACT FROM AUTHOR]

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. [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. [ABSTRACT FROM AUTHOR]

The identification of nitrate (NO 3 −) sources and biogeochemical transformations is critical for understanding the different nitrogen (N) pathways, and thus, for controlling diffuse pollution in groundwater affected by livestock and agricultural activities. This study combines chemical data, including environmental isotopes (δ2H H2O , δ18O H2O , δ15N NO3, and δ18O NO3), with land use/land cover data and a Bayesian isotope mixing model, with the aim of reducing the uncertainty when estimating the contributions of different pollution sources. Sampling was taken from 53 groundwater sites in Comarca Lagunera, northern Mexico, during 2018. The results revealed that the NO 3 − (as N) concentration ranged from 0.01 to 109 mg/L, with more than 32% of the sites exceeding the safe limit for drinking water quality established by the World Health Organization (10 mg/L). Moreover, according to the groundwater flow path, different biogeochemical transformations were observed throughout the study area: microbial nitrification was dominant in the groundwater recharge areas with elevated NO 3 − concentrations; in the transition zones a mixing of different transformations, such as nitrification, denitrification, and/or volatilization, were identified, associated to moderate NO 3 − concentrations; whereas in the discharge area the main process affecting NO 3 − concentrations was denitrification, resulting in low NO 3 − concentrations. The results of the MixSIAR isotope mixing model revealed that the application of manure from concentrated animal-feeding operations (∼48%) and urban sewage (∼43%) were the primary contributors of NO 3 − pollution, whereas synthetic fertilizers (∼5%), soil organic nitrogen (∼4%), and atmospheric deposition played a less important role. Finally, an estimation of an uncertainty index (UI90) of the isotope mixing results indicated that the uncertainties associated with atmospheric deposition and NO 3 −−fertilizers were the lowest (0.05 and 0.07, respectively), while those associated with manure and sewage were the highest (0.24 and 0.20, respectively). Image 1 • Sources, transformations and contributions of nitrate pollution in groundwater investigated. • Thirty-two percent the samples exceeded the WHO limit for safe drinking water. • Mainly the application of manure and sewage leaks drove the increase of nitrate concentration. • Mixing process among evaporated soil water and recirculated water from irrigation identified. • Different nitrate transformation processes in recharge, transition and discharge areas. The combined approach estimated a number of nitrate pollution sources and transformation processes in groundwater, whereby manure and sewage leakages were the main drivers. [ABSTRACT FROM AUTHOR]

• Multi-isotopic and molecular source tracking data show high agreement to identify nitrate sources. • ẟ 11B in effluents of wastewater treatment plant can be affected by livestock wastes. • Information obtained was employed by local authorities to establish new vulnerable zones. Nitrate (NO 3 -) pollution adversely impacts surface and groundwater quality. In recent decades, many countries have implemented measures to control and reduce anthropogenic nitrate pollution in water resources. However, to effectively implement mitigation measures at the origin of pollution,the source of nitrate must first be identified. The stable nitrogen and oxygen isotopes of NO 3 - (ẟ 15N and ẟ 18O) have been widely used to identify NO 3 - sources in water, and their combination with other stable isotopes such as boron (ẟ 11B) has further improved nitrate source identification. However, the use of these datasets has been limited due to their overlapping isotopic ranges, mixing between sources, and/or isotopic fractionation related to physicochemical processes. To overcome these limitations, we combined a multi-isotopic analysis with fecal indicator bacteria (FIB) and microbial source tracking (MST) techniques to improve nitrate origin identification. We applied this novel approach on 149 groundwater and 39 surface water samples distributed across Catalonia (NE Spain). A further 18 wastewater treatment plant (WWTP) effluents were also isotopically and biologically characterized. The groundwater and surface water results confirm that isotopes and MST analyses were complementary and provided more reliable information on the source of nitrate contamination. The isotope and MST data agreed or partially agreed in most of the samples evaluated (79 %). This approach was especially useful for nitrate pollution tracing in surface water but was also effective in groundwater samples influenced by organic nitrate pollution. Furthermore, the findings from the WWTP effluents suggest that the use of literature values to define the isotopic ranges of anthropogenic sources can constrain interpretations. We therefore recommend that local sources be isotopically characterized for accurate interpretations. For instance, the detection of MST inferred animal influence in some WWTP effluents, but the ẟ 11B values were higher than those reported in the literature for wastewater. The results of this study have been used by local water authorities to review uncertain cases and identify new vulnerable zones in Catalonia according to the European Nitrate Directive (91/676/CEE). Image, graphical abstract [ABSTRACT FROM AUTHOR]

Excessive nitrate in water systems is prevailing and a global risk of human health. Polluted river sediments are dominated by anaerobes and often the hotspot of denitrification. So far, little is known about the ecological effects of nitrate pollution on microbial dynamics, especially those in sulfide-rich sediments. Here we simulated a nitrate surge and monitored the microbial responses, as well as the changes of important environmental parameters in a sulfide-rich river sediment for a month. Our analysis of sediment microbial communities showed that elevated nitrate led to (i) a functional convergence at denitrification and sulfide oxidation, (ii) a taxonomic convergence at Proteobacteria , and (iii) a significant loss of biodiversity, community stability and other functions. Two chemolithotrophic denitrifiers Thiobacillus and Luteimonas were enriched after nitrate amendment, although the original communities were dominated by methanogens and syntrophic bacteria. Also, serial dilutions of sediment microbial communities found that Thiobacillus thiophilu s dominated 18/30 communities because of its capability of simultaneous nitrate reduction and sulfide oxidation. Additionally, our network analysis indicated that keystone taxa seemed more likely to be native auxotrophs (e.g., syntrophic bacteria, methanogens) rather than dominant denitrifiers, possibly because of the extensive interspecific cross-feeding they estabilished, while environment perturbations probably disrupted that cross-feeding and simplified microbial interactions. This study advances our understanding of microbial community responses to nitrate pollution and possible mechanism in the sulfide-rich river sediment. Unlabelled Image • Nitrate led to a functional convergence at sulfide oxidation and denitrification. • Resulting sediments were depleted of sulfide and Fe(II) after 1 month. • Resulting microbial communities underwent a significant loss of biodiversity • Microbial interactive networks were mostly sustained by cross-feeders. [ABSTRACT FROM AUTHOR]

Effluents from leather tanneries and other small-scale industries have caused groundwater contamination in one of the biggest industrial centers (i.e. Vellore) of south India. This study evaluated quality of 70 different open and tube wells for consumption and health risks by collecting groundwater samples in four different seasons between 2017−2018. We compared physicochemical parameters of the groundwater samples with international drinking water standards (World Health Organization) to know their suitability for human consumption. Piper's trilinear diagram classified most of them as Ca-Cl and mixed Ca-Mg-Cl types. Inverse Distance Weighted (IDW) spatial interpolation showed the spatial distributions of different groundwater quality parameters. These parameters, including the Water Quality Index (WQI), indicated that most of the samples collected during the non-rainfall seasons (post-NE monsoon: 82.8 %; pre-SW monsoon: 78.6 %) were 'poor' for consumption. However, the qualities of 40–44.3 % of samples collected during both the rainfall seasons (NE and SW monsoon) were "good". We evaluated non-carcinogenic health risks for children and adults from consumption of the nitrate-rich groundwater by estimating the Hazard Quotient (HQ). Our results did not suggest any health risk for children and adults during both the rainfall seasons. In the non-rainfall seasons, about 59–63 % of samples posed health risk to children and 37–39 % caused possible health risk to the adult population. [ABSTRACT FROM AUTHOR]

The geological conceptual model is considered a major source of uncertainty in groundwater modelling and well capture zone delineation. However, how to account for it in groundwater policy and management remains largely unresolved. We explore the drivers and barriers to account for geological conceptual uncertainty in groundwater protection amongst decision makers and stakeholders in an agricultural groundwater catchment in Denmark. Using a groundwater model, we analyze the impact of alternative geological conceptual models on capture zone delineation. A focus area, which covers multiple modelled capture zones, is defined and considered for groundwater protection. Model uncertainty and focus area are discussed at two workshops, one with local and national stakeholders and another with local farmers. The drivers to account for model uncertainty include: i) safer drinking water protection by considering a larger area for protection than identified from a single geological model; and ii) stability over time of management plans. The main barrier is the additional cost to the stakeholders for the protection of a larger area. We conclude that integration of geological uncertainty in groundwater protection plans may be improved through: i) better communication between the research community and the national water authority; ii) more constraining guidelines regarding the estimation of geological uncertainty; and iii) the development of a framework ensuring knowledge transfer to the local water authorities and detailing how to integrate uncertainty in management plans. Unlabelled Image • Groundwater management seldom accounts for geological conceptual uncertainty. • The study combines a hydrogeological and a stakeholder approach to model uncertainty. • The dominant barrier to account for geological uncertainty is financial costs. • The dominant driver is safer and more stable drinking water protection. • We propose measures to integrate geological uncertainty in groundwater management. [ABSTRACT FROM AUTHOR]

The Mar Menor (SE Spain), the largest hypersaline coastal lagoon of the Mediterranean basin, suffers a severe eutrophication crisis due to the nutrients that receives from the Campo de Cartagena watershed, mainly nitrate from intensive agriculture. This paper updates the state of the art in relation with nutrient discharges to the Mar Menor, and summarizes results from different tested Nature-Based Solution (NBS). Specifically, we show i) results from a pilot plant with woodchip bioreactors for nitrate-enriched brine denitrification, and ii) the first results obtained in a pilot plant with bioreactors and constructed wetlands for treatment of agricultural drainage water and leachates, as well as other effluents. Nutrient discharges to the lagoon are highly variable and occur via drainage network, drains, stormwater pipes, direct groundwater discharges from the Quaternary aquifer, and others. For instance, between January 2017 and January 2018 measured daily superficial discharge (floods excluded) ofN-NO 3 − amounted from 119 kg d−1 to 1084 kg d−1. Estimations subsurface discharges ranged 815 to 3836 kg N-NO 3 − d−1 in 2018–2020. Field studies in coastal wetlands (e.g. inflow ≈20–30 mg N-NO 3 − L−1, removal ≈80–90%) and results from pilot plants with bioreactors (e.g. inflow ≈30–40 mg N-NO 3 − L−1, removal ≈90–95%) and constructed wetlands (e.g. inflow ≈30–40 mg N-NO 3 − L−1, removal ≈60–70%), showed the good performance of these systems for nutrient retention. Four strategies are considered for reducing nutrient inputs into the Mar Menor, which include a combination of nature-based solutions and best management practices. (i) Reducing the leaching of nitrate to the aquifer and export of nutrients and sediments following heavy rains by improving fertilization, and irrigation routines, and soil conservation measures in the agricultural fields. (ii) Development of effective and scalable tools for denitrification of nitrate-rich brine produced by on-farm desalination plants. (iii) Capture and treatment of polluted water discharged to the Mar Menor via hydrologic networks, subsurface flow, drainage ditches, and others. (iv) Preservation and restoration of coastal wetlands. Unlabelled Image • Mar Menor receives nutrients, mainly from agricultural discharges. • Coastal wetlands acts as buffers protecting the Mar Menor from nutrient inputs. • Bioreactors and CWs are recommended BMP for treatment of nutrient enriched discharges. • In the Campo de Cartagena BMP should be addressed on a watershed scale. • BMP should address fertilization and irrigation protocols and soil conservation. [ABSTRACT FROM AUTHOR]

• Vegetables are irrigated with waters of variable qualities. • Integrated irrigation, fertilization and salt management vital for sustainability. • Irrigation with water high in salts causes groundwater contamination. • Nitrate is the major pollutant in arid and semi-arid regions. • Desalination can promote strategies for sustainable irrigation. Water-scarcity in dry areas is driving agriculture towards increased utilization of marginal to poor quality water sources for irrigation. This includes groundwater and recycled wastewater that tend to be characterized by high levels of minerals and commonly of problematic salts. Israel has been a global leader in irrigation application efficiency, use of groundwater with relatively high concentrations of salts and recycled municipal wastewater, and recently, in the use of large-scale seawater desalination for human consumption and irrigation. Irrigation with water high in salts has been shown to be unsustainable in many dry regions, mostly due to increasing salinity of soil, subsoil, and groundwater resulting from the application and leaching of salts. We present a summary of the direct effects of salinity on crop production, of its management in vegetable crops, and of the environmental consequences of different salinity management practices. The objective of this review is to provide a fundamental understanding of the advantages and limitations of irrigating vegetable crops as a function of water quality, considering good quality surface and groundwater, saline/brackish water, treated wastewater and desalinated water. The long-term experience of irrigation of annual vegetable and other horticultural crops with diverse water qualities in Israel is reviewed. The environmental implications of irrigation as a function of water salinity, both on a national scale and using a local case study of irrigation with brackish groundwater of vegetables in Israel's Arava Valley, are discussed. Finally, possible management strategies are suggested to reduce environmental consequences of irrigation with water containing salts and address the fundamental question; "can irrigated arid zone vegetable production be sustainable?" [ABSTRACT FROM AUTHOR]

Denitrification in floodplain soils is one key process that determines the buffering capacity of riparian zones in terms of diffuse nitrate pollution. One widely used approach to measure the denitrification potential is the acetylene inhibition technique that requires fresh soil samples. We conducted experiments with air-dried soils using a time series analysis to determine the optimal rewetting period. Thus, air-dried soil samples from six different floodplain areas in Germany were rewetted for 1 to 13days to 100% water-filled pore space. We analyzed nitrogen accumulated as N2O in the top of anaerobic flasks with and without acetylene by gas chromatography after four hours of incubation. We observed an overall optimal rewetting of at least seven days for complete denitrification. We also saw the strong influence of pH and field capacity on the denitrification product ratio; in soils with pH < 7, we hardly assumed complete denitrification, whereas the treatments with pH > 7 achieved stable values after seven days of rewetting. This advanced method provides the opportunity to carry out campaigns with large soil sample sizes on the landscape scale, as samples can be stored dry until measurements are taken. [ABSTRACT FROM AUTHOR]

Pollution by NO 3 −-N seriously threatens the quality of shallow groundwater (SG) around Erhai Lake, which is the 2nd largest source of freshwater in the plateau area in southwest China; further, NO 3 −-N affects the lake water quality and human health. We collected SG samples during the dry and wet seasons in 2018 and 2019, and the potential NO 3 −-N sources and their fates were identified in SG by NO 3 − isotopes and hydrochemical methods. Our results showed that the NO 3 −-N concentrations in the SG in the wet season in farmland were far higher than those in the dry season in residential areas. The high variation in δ15N–NO 3 - and δ18O–NO 3 - (from −12.78‰ to +18.10‰ and −27.62‰ to +23.07‰, respectively, in the farmland and from −5.34‰ to +34.54‰ and −20.04‰ to +17.47‰, respectively, in the residential area) indicated multiple NO 3 −-N sources in the SG. The NO 3 −-N in the farmland mainly originated from chemical nitrogen fertilizer (NF, 36%), soil nitrogen (SN, 33%) and manure and sewage (M&S, 24%) in the dry season and from SN (61%) and NF (33%) in the wet season. The NO 3 −-N in the residential area mainly originated from M&S (57%), SN (23%) and NF (14%) in the dry season and from SN (50%), NF (25%) and M&S (24%) in the wet season. Nitrogen transformation was dominated by denitrification in the SG. The most polluted SG area was observed on the east bank of Erhai Lake, NO 3 −-N mainly originated from NF. But the NO 3 −-N pollution slowed down from high altitude to lakeside and had multiple NO 3 −-N sources on the west bank of Erhai Lake. The SG was contaminated by nitrogen from NF, SN and M&S along the flow path and flowed into Erhai Lake. Therefore, reducing soil nitrogen concentrations and chemical nitrogen fertilizer applications and improving sewage facilities are significant ways to mitigate nitrate pollution in the SG. Image 1 • Hydrogeology, land use and seasonal change were key factors affecting NO 3 −-N and dual isotopes in SG. • Sources and transformations of NO 3 −-N in SG were identified by δ15N, δ18O and hydrochemistry. • Spatiotemporal contributions from different NO 3 −-N sources were identified by SIAR model. • Main source and transformation process of NO 3 −-N were soil N and denitrification, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The application of chemical and organic fertilizers to agricultural lands increases nutrient pools and affects soil and water quality. Understanding changes in groundwater quality due to the anthropogenic activities over time is important to human and ecosystem health. In 2017, we resampled 58 wells monitored in the year 2000 to evaluate the rate of changes in groundwater quality and water quality indices over time in response to agricultural and industrial activities and climate changes. The groundwater in two sampling years was dominated by Ca–HCO3 water type. The mean groundwater pH, electrical conductivity (EC), calcium ( Ca 2 + ), magnesium ( Mg 2 + ), and sodium ( Na + ) concentrations did not significantly change over time, while a significant buildup in bicarbonate (HCO 3 -) (189–305 mg l−1), nitrate ( NO 3 - ) (41–56 mg l−1), chloride ( Cl - ) (57–77 mg l−1) and a significant decrease in sulfate ( SO 4 2 - ) (159–91 mg l−1) and potassium ( K + ) (3–2 mg l−1) was observed. In 2000, 45% of the water samples were classified as high salinity hazard, and this value increased to 52% by 2017, indicating that salinity of the water samples increased over 17 years. In 2000, only 25% of the total area had a NO 3 - value greater than 50 mg l−1; and this value increased sharply to 62% by 2017, indicating that NO 3 - concentrations significantly increased with approximately 2.2% annually in groundwater, over 17 years. Approximately, 55% of the groundwaters with NO 3 - concentration values of less than 40 mg l−1 in 2000 shifts one to four categories upward in 2017. The percentage of water samples which was shifted to the next category with NO 3 - concentration higher than 50 mg l−1 and approaching the limit of the World Health Organization was doubled in 2017 compared with 2000. High application of chemical and manure fertilizers in excess of crop needs should be avoided in the studied area to prevent continued increases in groundwater NO 3 - concentrations. [ABSTRACT FROM AUTHOR]

Nitrate pollution of surface and groundwater resources is a major worldwide environmental problem. In this study nitrogen isotopes of water, soil, fertilizer and manure were analyzed to determine the pollution sources of nitrate in the groundwater and surface waters of Anthemountas basin. The SIAR model and multivariate statistical analysis were used to determine and quantify the contribution of different NO 3 ̄ sources in groundwater and surface water. Additionally, a detailed literature overview was carried out to identify the origin of nitrate pollution in surface and ground waters based on ΝΟ 3 − isotopes. The Piper diagram identified the dominant water types as Mg-Ca-HCO 3 and Ca-Mg-HCO 3. Nitrate concentrations reached 162.0 mg/L in groundwater and 39.0 mg/L in surface waters. The main source of nitrate in groundwater was mainly nitrified ammonium-based synthetic urea and less nitrate-based synthetic fertilizers. The correlation of SIAR results with other trace elements revealed a negative correlation between hexavalent chromium and a) nitrate-based synthetic fertilizers, and b) nitrification of urea synthetic fertilizers. However, a positive correlation was observed between hexavalent chromium and anthropogenic organic matter. The literature overview provided the basis to design a novel management protocol for nitrate pollution that includes three steps: a) fundamental research, b) management tools, c) monitoring and preservation actions. However, an integrated management protocol for nitrate pollution requires a deeper understanding of the hydro-system and the full participation of local farmers and stakeholders. Unlabelled Image • Nitrate concentrations in groundwater reach 162.0 mg/L in the study area. • Nitrate pollution mainly originates from synthetic fertilizers. • A negative relationship was determined between fertilizer application and Cr(VI) in groundwater. • A surface and groundwater resource management protocol for nitrate pollution is proposed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nutrient effluents from urban and agricultural inputs have resulted in high concentrations of nitrate in freshwater ecosystems. Exposure to nitrate can be particularly threatening to aquatic organisms, but a quantitative synthesis of the overall effects on amphibians, amphipods and fish is currently unavailable. Moreover, in disturbed ecosystems, organisms are unlikely to face a single stressor in isolation, and interactions among environmental stressors can enhance the negative effects of nitrate on organisms. Here, the effects of elevated nitrate on activity level, deformity rates, hatching success, growth and survival of three taxonomic groups of aquatically respiring organisms are documented. Effect sizes were extracted from 68 studies and analysed using meta-analytical techniques. The influence of nitrate on life-stages was also assessed. A factorial meta-analysis was conducted to examine the effect of nitrate and its interaction with other ecological stressors on organismal survival. Overall, the impacts of nitrate are biased towards amphibians (46 studies) and fish (13 studies), and less is known about amphipods (five studies). We found that exposure to nitrate translates to a 79% decrease in activity, a 29% decrease in growth, and reduces survival by 62%. Nitrate exposure also increases developmental deformities but does not affect hatching success. Nitrate exposure was found to influence all life-stages except embryos. Differences in the sensitivity of nitrate among taxonomic groups tended to be negligible. The factorial meta-analysis (14 amphibians and two amphipod studies) showed that nitrate in combination with other stressors affects survival in a non-additive manner. Our results indicate that nitrate can have strong effects on aquatic organisms and can interact with other environmental stressors which compound the negative effects on survival. Overall, the impacts of nitrate and additional stressors are complex requiring a holistic approach to better conserve freshwater biodiversity in the face of ongoing global change. Image 1 • Nitrate pollution on top of other stressors threaten the persistence of aquatic taxa. • Across studies, nitrate exposure tends to reduce activity, growth, and survival of aquatic taxa. • Elevated nitrate influences all life stages (larvae, juveniles and adults) except embryos. • Nitrate in combination with other stressors affects survival in a non-additive manner. Nitrate pollution reduces the activity, growth, and survival of aquatic taxa and, when combined with other stressors, affects survival in a non-additive manner. [ABSTRACT FROM AUTHOR]

• Nearly 41% groundwater in Chenghai Lake basin exceed the nitrate concentration of 50 mg/L of drinking water threshold (WHO and China). • Soil nitrogen is the prime source for groundwater nitrate pollution, while landfill/sewage leachate contributes considerably to aquifers. • Intensified farmlands and residential area result in different isotopic fractional signatures of nitrate in groundwater along the altitudinal gradient. In recent decades, multiple occurrences of algal blooms have substantially deteriorated water quality, especially for the nutrient budget in plateau lakes. Specifically, NO 3 − pollution has critically threatened groundwater quality, thus increasing human health risk if groundwater serves as a drinking source. To identify the origin and fate of NO 3 − in a plateau lake basin, we utilized nitrate isotope natural abundance and water chemistry information under land use frameworks and groundwater flow information. In December 2018, we collected water samples from aquifers (n = 33), rivers (n = 2), soil (n = 7), and lakes (n = 4) in Chenghai Lake basin, Southwest China. Our results showed that nearly 41% of groundwater samples failed to meet the drinking water standard of WHO and China (GB/T 5749-2006) of 50 mg/L for NO 3 − during the dry season. The high variation of δ15N-NO 3 − (from −3.3 to +41.3‰) and δ18O-NO 3 − (from −6.4 to +13.6‰) indicated multiple N sources and N cycling processes. Our analysis revealed that 16%–80% of nitrate in groundwater was derived from accumulated soil N, whereas 13%–76% was contributed from manure/landfill leachate. The contribution from atmospheric nitrogen deposition to aquifers was less than 3%. Manure/landfill and soil nitrogen were the primary N sources, contributing for 38.9% and 35.3% to N loading in lake. As for river water, soil nitrogen contributed for 69.7% and 37.2% in R1 and R2, respectively. The denitrification process significantly affects nitrate attenuation of N sources in aquifers. An increasing trend in NO 3 − concentration was noticed along the groundwater flow path (A-A') from mountain area to lake. Among different pathways, distinct nitrate sources loading downwards to the aquifers were observed in massive farmlands and residential areas. Thus, the information on both land-use and groundwater flow pathways is indispensable for modelling nitrate sources and transformation processes using the dual isotope approach. [ABSTRACT FROM AUTHOR]

The shift from rainfed to irrigated agriculture is associated with a change in the fertilization rates due to increases in expected production and the fact of growing more N demanding crops. In addition, the circulation of irrigation return flows (IRF) mobilizes soluble salts stored in soils or geological materials. As a consequence, it implies severe modifications in the dynamics and total amount of soluble salts and nitrogen exported, especially in semi-arid watersheds. In this study, long-term data collected by the regional authorities was used to assess the effects of irrigation implementation on salinity (using electrical conductivity, EC, as a proxy) and nitrate concentration (NO 3 −) after the transformation of ca. 77 km2 from rainfed to irrigated agriculture in the Cidacos River (CR) watershed. The results indicate that water quality in the lower reaches of the CR was significantly modified after the diffuse incorporation of IRF. In contrast, neither EC nor NO 3 − were different in those monitoring stations whose contributing watersheds did not include transformed area. In addition, the temporal dynamics in the analysed variables shifted from a rainfed land signal typical in the region to an irrigated land signal, and the hydrochemical type of the CR shifted from mixed-to-Na+-mixed-to-HCO 3 – to mostly Na+-mixed type, typical of waters affected by IRF in the region. Groundwater EC and NO 3 − also increased in those wells located within the irrigated area. Although there are great uncertainties in the actual amount of salt and N reaching the CR via IRF, the expected contribution of waste water spilled into the CR is minor in comparison to other sources, mostly agricultural sources in the case of N. The observed changes have promoted the designation of the lower reaches of the CR as "affected" by NO 3 − pollution, and the whole CR watershed as a Nitrate Vulnerable Zone, with the emergent question about whether irrigation implementation as carried out currently in Spain is against the environmental objectives of the Water Framework Directive. Unlabelled Image • Irrigation increased salinity and nitrate in the lower reaches of Cidacos River. • Irrigation shifted the seasonal pattern of variation in water quality. • Compositional data of river water changes into return flows chemistry. • Irrigation promotes new nitrate vulnerable zone in the study area. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Nitrate pollution distribution in surface water was studied. • A methodology using fecal sterols is proposed to identify source of pollution. • Dominant nitrate sources are chemical fertilizer and livestock wastes. • Fecal sterols showed potential for source identification of nitrate pollution. Coprostanol was tested as ecological indicator to trace domestic and manure effluents and to investigate possible pollution sources in surface water. Pollution assessment was performed by analysing NO 3 −, NO 2 −, coprostanol (5β(H)-Cholestan-3β-ol), and cholestanol (5α(H)-Cholestan-3β-ol) in water samples from 42 sites along rivers in Shimabara and Unzen City, Japan. NO 2 -N concentration exceeded 0.04 mg L−1 at 2 sampling sites during winter and 6 sampling sites during summer. NO 3 + NO 2 -N concentration exceeded 10 mg L−1 at 19 sampling sites during winter and 7 sampling sites during in summer. The highest concentration was 82.4 mg L−1 in summer. Detectable NO 3 -N concentration was observed in northern parts of the study area. Coprostanol concentration exceeded 700 ng L−1 (Australian Drinking Water Standard) at 8 sampling points during winter and 6 sampling sites during summer. At 10 and 5% of the sampling sites, both nitrate and coprostanol concentration exceeded drinking water standard during winter and summer, respectively. The percentage of sampling sites where either concentration was above drinking water standard was 45% during winter and 22% during summer season. However, depending on sampling site, the relationships between nitrate and coprostanol concentrations showed different patterns. The sterol ratio exceeded 0.5 at 17 sampling sites during winter and 14 sampling sites during summer. Thus, it was confirmed that fecal pollution is present in the studied surface water. A method to distinguish between principal pollution sources was developed by separating four areas in a nitrate concentration and sterol ratio plot. Results show that sampled data could be reasonably classified into appropriate polluted/non-polluted groups. Thus, coprostanol and sterol ratio can be used as indicators to distinguish between different nitrate pollution sources in surface water. [ABSTRACT FROM AUTHOR]

Groundwater resources are of utmost importance in sustaining water related ecosystems, including humans. The long-lasting impacts from anthropogenic activities require early actions, owing to the natural time lag in groundwater formation and renewal. The European Union (EU) policy, within the implementation of the Water Framework Directive (WFD), requires Member States to identify and reverse any significant and sustained upward trend in the concentration of pollutants, defining specific protection measures to be included in the River Basin Management Plans (RBMP). In Italy, official guidelines for trend and trend reversal assessment have been published recently. Statistical methods, such as the Mann-Kendall test for trend analysis and the Sen's method for estimating concentration scenarios, should be applied at the fixed terms stated by the WFD implementation cycles to identify upward trends, while the Pettitt test is proposed for the identification of trend reversal. In this paper, we present an application of a slightly modified version of the Italian Guidelines to a groundwater body in Northern Italy featuring nitrate pollution and discuss its advantages and limitations. In addition to Pettitt test, for the trend reversal analysis, we apply the Mann-Kendall test in two sections and compare the results. We conclude that this method seems more reliable than Pettitt test to identify a reversal point in quality time series. The overall procedure can be easily applied to any groundwater body defined at risk across Europe, for the assessment of the upward trends of pollutants and their reversal, even with little chemical monitoring data. Although focused on the EU legislative framework, this procedure may be relevant for a wider context, allowing to individuate upward trend as early warning for contamination processes in an integrated water resources management context.

In this investigation, the geochemical progression of a total of 31 groundwater samples of pre-monsoon season was assessed with categorization based on entropy weight water quality index and risk assessment on public health in the semi-arid area of Godavari basin, Maharashtra, Central India. Graphically, the major groundwater types identified were Ca-HCO 3 , mixed Ca-Mg-Cl, and mixed Ca-Na-HCO 3 . Based on [Mg 2+ /Na + ] with [Ca 2+ /Na + ] and [HCO 3 - /Na + ] with [Ca 2+ /Na + ] plots, carbonate and silicate weathering were identified as a major geochemical process governing groundwater chemistry. The presence of reverse ion exchange process was authenticated by (Ca 2+ + Mg 2+ ) vs. (HCO 3 - + SO 4 2- ) and Na + + K + -Cl - vs. (Ca 2+ + Mg 2+ )-(HCO 3 - + SO 4 2- ) plots. The saturation index values for calcite and dolomite showed that these minerals were in dissolution state. The dissolution of gypsum, dolomite, and anhydrite increased Ca 2+ load in groundwater which accelerated the precipitation of calcite. The high toxic level of NO 3 - (> 45 mg/L) was identified in 64.5% of the 31 groundwater samples, whereas F - concentration exceeded the threshold value in 12.9% of samples. Based on the entropy weight water quality index values, 70% of the samples were found to have moderate quality for drinking. In addition, health risk evaluation showed that the total hazard, due to fluoride and nitrate through oral pathways, was much higher than that through the dermal pathway. Children were found to be at high risk due to the consumption of NO 3 - and F - contaminated water. The calculated irrigation water quality index (IWQI) diverge from 7.4-89.2, expressing excellent to good quality for irrigation. Based on the irrigation water quality index, 90.3% of samples were found excellent for irrigation and 6.4% of good quality for irrigation. Authors recommend that continuous water quality monitoring programs along with effective management practices should be developed to avoid excessive extraction of groundwater.

Nitrate contaminant degrades groundwater quality and threatens the health of the humans, livestock, and the environment. Damaneh-Daran aquifer is located at upstream of the Zayandehrood reservoir in west-central Iran. This aquifer has been highly contaminated by nitrate and is still rapidly being contaminated. Thus, its quality needs to be remediated. This paper is focused on the quantity-quality modeling to predict the average nitrate concentration of the aquifer. Several remediation scenarios are presented in a period beginning from fall 2019, ending in spring 2024. These scenarios address several ways to mitigate the injection of the major sources of contamination in the region, such as equipping the urban regions with wastewater collection and treatment plants and reducing the fertilizers' use. The decreased use of the fertilizers may be achieved through two strategies: directly reducing the amount of the fertilizers by several specific and predefined rates of reduction and indirectly decreasing the amount of the fertilizers used by crop pattern modification. The latter strategy is evaluated to replace all or a part of the areas allocated to the more fertilizer-demanding crops with those of the less fertilizer-demanding crops. Furthermore, some of these scenarios are hybridized to more mitigate groundwater quality degradation. The results of performing the proposed scenarios are once compared together and then compared with the trend scenario letting current case study conditions and facilities be held in the future. The results suggest that the scenario hybridizing the effects of the wastewater treatment plants-equipping scenario with those of the quality-enhancing crop pattern modification scenario is evaluated as the most effective and best-performing scenario, implementation of which offers 20% and 30% reduction of the nitrate concentration for the agricultural and urban areas, respectively.

Globally occurring nitrate pollution in groundwater is harming the environment and human health. In situ hydrogen addition to stimulate denitrification has been proposed as a remediation strategy. However, observed nitrite accumulation and incomplete denitrification are severe drawbacks that possibly stem from the specific microbial community composition. We set up a microcosm experiment comprising sediment and groundwater from a nitrate polluted oxic oligotrophic aquifer. After the microcosms were sparged with hydrogen gas, samples were taken regularly within 122 h for nitrate and nitrite measurements, community composition analysis via 16S rRNA gene amplicon sequencing and gene and transcript quantification via qPCR of reductase genes essential for complete denitrification. The highest nitrate reduction rates and greatest increase in bacterial abundance coincided with a 15.3-fold increase in relative abundance of Rhodocyclaceae, specifically six ASVs that are closely related to the genus Dechloromonas. The denitrification reductase genes napA, nirS and clade I nosZ also increased significantly over the observation period. We conclude that taxa of the genus Dechloromonas are the prevailing hydrogenotrophic denitrifiers in this nitrate polluted aquifer and the ability of hydrogenotrophic denitrification under the given conditions is species-specific., (© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS.)