Groundwater nitrate contamination and agricultural land use: A grey water footprint perspective in Southern Apulia Region (Italy)

Groundwater nitrate contamination in China: Spatial distribution, temporal trend, and driver analysis

China's groundwater is facing a significant threat from nitrate pollution. Here we analyzed 2348 regional surveys of groundwater nitrate levels in China from 1990 to 2020, examining distribution, trends, and drivers. This study uncovers a concerning rise in nitrate pollution, with estimated median nitrate levels climbing from 3.84 mg/L in 1990 to 6.94 mg/L in 2020. A stark contrast is observed between regions: the northern areas have a median nitrate concentration of 8.54 mg/L, significantly higher than the southern regions, where the median is just 7.15 mg/L. From 1990 to 2020, agricultural activity consistently emerges as the dominant driver of changes in groundwater nitrate concentrations, while groundwater exploitation, domestic pollution, and industrial production also contribute to varying degrees. This analysis highlights the urgency for region-specific policies and interventions to address the escalating nitrate pollution in China's groundwater.

Investigating pollution input to coastal groundwater-dependent ecosystems in dry Mediterranean agricultural regions

The insufficient taking into account of groundwater as a basis for implementing protection measures for coastal wetlands can be related to the damage they are increasingly exposed to. The aim of this study is to demonstrate the pertinence of combining hydrogeological tools with assessment of pollutant fluxes and stable isotopes of O, H and N, as well as groundwater time-tracers to identify past and present pollution sources resulting from human activities and threatening shallow groundwater-dependent ecosystems. A survey combining physico-chemical parameters, major ions, environmental isotopes (18O, 2H, 15N and 3H), with emerging organic contaminants including pesticides and trace elements, associated with a land use analysis, was carried out in southern Italy, including groundwater, surface water and lagoon water samples. Results show pollution of the shallow groundwater and the connected lagoon from both agricultural and domestic sources. The N-isotopes highlight nitrate sources as coming from the soil and associated with the use of manure-type fertilizers related to the historical agricultural context of the area involving high-productivity olive groves. Analysis of EOCs has revealed the presence of 8 pesticides, half of which have been banned for two decades and two considered as pollutant legacies (atrazine and simazine), as well as 15 molecules, including pharmaceuticals and stimulants, identified in areas with human regular presence, including rapidly degradable compounds (caffeine and ibuprofen). Results show that agricultural pollution in the area is associated with the legacy of intensive olive growing in the past, highlighting the storage capacity of the aquifer, while domestic pollution is sporadic and associated with regular human presence without efficient modern sanitation systems. Moreover, results demonstrate the urgent need to consider groundwater as a vector of pollution to coastal ecosystems and the impact of pollutant legacies in planning management measures and policies, with the aim of achieving 'good ecological status' for waterbodies.

Green manure application improves insect resistance of subsequent crops through the optimization of soil nutrients and rhizosphere microbiota

Green manure (GM) enhances organic agriculture by improving soil quality and microbiota, yet its effects on plant resistance are unclear. Investigating the GM crop hairy vetch-maize rotation system, a widely adopted GM practice in China, we aimed to determine maize resistance to fall armyworm (FAW), Spodoptera frugiperda (Smith), a major pest. Greenhouse experiments with three fertilization treatments (chemical fertilizer, GM, and a combination) revealed that GM applications significantly improved maize resistance to FAW, evidenced by reduced larval feeding preference and pupal weight. GM also enriched soil nutrients, beneficial rhizobacteria, and resistance-related compounds, such as salicylic acid, jasmonic acid, and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), in maize. The results suggest that GM-amended soils and microbial communities may have an underestimated role in regulating host plant adaptation to pests by increasing plant resistance. This study can provide information for developing and implementing environmentally friendly and sustainable cropping systems with enhanced resistance to pests and diseases.

Will structural adjustment and financial support affect low-carbon agricultural production in the Yellow River Basin?

Based on the panel data of 75 cities in the Yellow River Basin from 2000 to 2020, this manuscript measures the agricultural low-carbon production efficiency scientifically through the Super-SBM model. In addition, the deviation degree of agricultural industry is used as the index of structural adjustment. Finally, the spatial Durbin model is used to analyze the effect direction and degree of structural adjustment, financial support, and their synergistic effect on agricultural low-carbon production efficiency. The results show that ① the agricultural low-carbon production efficiency in the Yellow River Basin shows a trend of fluctuating downward and a spatial distribution pattern of "high in the east and low in the west". ② Structural adjustment in local region and adjacent areas has a significantly negative impact on agricultural low-carbon production, and the inhibitory effect in adjacent areas is more obvious, and the negative spatial spillover effect is strong. Financial support has a significantly positive impact on agricultural low-carbon production, but the spatial spillover effect of adjacent areas is not obvious. ③ By region, structural adjustment has a significantly negative impact on low-carbon agricultural production in the midstream and downstream regions, while financial support has a significantly positive impact on low-carbon agricultural production in the upstream region. The impact of control variables on agricultural low-carbon production varies from region to region. ④ The synergistic effect of structural adjustment and financial support in the whole and midstream region shows a significantly positive impact on agricultural low-carbon production, indicating that financial support has a certain correction effect on structural adjustment. The coefficient between the upstream and downstream regions is positive but not significant. The conclusions have important reference significance for promoting the ecological protection and high-quality development and agricultural low-carbon development in the Yellow River Basin.

Integrating machine learning models with cross-validation and bootstrapping for evaluating groundwater quality in Kanchanaburi province, Thailand

Exploring the potential of new models for mapping groundwater quality presents a major challenge in water resource management, particularly in Kanchanaburi Province, Thailand, where groundwater faces contamination risks. This study aimed to explore the applicability of random forest (RF) and artificial neural networks (ANN) models to predict groundwater quality. Particularly, these two models were integrated into cross-validation (CV) and bootstrapping (B) techniques to build predictive models, including RF-CV, RF-B, ANN-CV, and ANN-B. Entropy groundwater quality index (EWQI) was converted to normalized EWQI which was then classified into five levels from very poor to very good. A total of twelve physicochemical parameters from 180 groundwater wells, including potassium, sodium, calcium, magnesium, chloride, sulfate, bicarbonate, nitrate, pH, electrical conductivity, total dissolved solids, and total hardness, were investigated to decipher groundwater quality in the eastern part of Kanchanaburi Province, Thailand. Our results indicated that groundwater quality in the study area was primarily polluted by calcium, magnesium, and bicarbonate and that the RF-CV model (RMSE = 0.06, R2 = 0.87, MAE = 0.04) outperformed the RF-B (RMSE = 0.07, R2 = 0.80, MAE = 0.04), ANN-CV (RMSE = 0.09, R2 = 0.70, MAE = 0.06), and ANN-B (RMSE = 0.10, R2 = 0.67, MAE = 0.06). Our findings highlight the superiority of the RF models over the ANN models based on the CV and B techniques. In addition, the role of groundwater parameters to the normalized EWQI in various machine learning models was found. The groundwater quality map created by the RF-CV model can be applied to orient groundwater use.

A Decade after the Outbreak of Xylella fastidiosa subsp. pauca in Apulia (Southern Italy): Methodical Literature Analysis of Research Strategies

In 2013, an outbreak of Xylella fastidiosa (Xf) was identified for the first time in Europe, in the extreme south of Italy (Apulia, Salento territory). The locally identified subspecies pauca turned out to be lethal for olive trees, starting an unprecedented phytosanitary emergency for one of the most iconic cultivations of the Mediterranean area. Xf pauca (Xfp) is responsible for a severe disease, the olive quick decline syndrome (OQDS), spreading epidemically and with dramatic impact on the agriculture, the landscape, the tourism and the cultural heritage of this region. The bacterium, transmitted by insects that feed on xylem sap, causes rapid wilting in olive trees due to biofilm formation, which obstructs the plant xylematic vessels. The aim of this review is to perform a thorough analysis that offers a general overview of the published work, from 2013 to December 2023, related to the Xfp outbreak in Apulia. This latter hereto has killed millions of olive trees and left a ghostly landscape with more than 8000 square kilometers of infected territory, that is 40% of the region. The majority of the research efforts made to date to combat Xfp in olive plants are listed in the present review, starting with the early attempts to identify the bacterium, the investigations to pinpoint and possibly control the vector, the assessment of specific diagnostic techniques and the pioneered therapeutic approaches. Interestingly, according to the general set criteria for the preliminary examination of the accessible scientific literature related to the Xfp outbreak on Apulian olive trees, fewer than 300 papers can be found over the last decade. Most of them essentially emphasize the importance of developing diagnostic tools that can identify the disease early, even when infected plants are still asymptomatic, in order to reduce the risk of infection for the surrounding plants. On the other hand, in the published work, the diagnostic focus (57%) overwhelmingly encompasses all other possible investigation goals such as vectors, impacts and possible treatments. Notably, between 2013 and 2023, only 6.3% of the literature reports addressing the topic of Xfp in Apulia were concerned with the application of specific treatments against the bacterium. Among them, those reporting field trials on infected plants, including simple pruning indications, were further limited (6%).

Assessing nitrate groundwater hotspots in Europe reveals an inadequate designation of Nitrate Vulnerable Zones

Monitoring networks show that the European Union Nitrates Directive (ND) has had mixed success in reducing nitrate concentrations in groundwater. By combining machine learning and monitored nitrate concentrations (1992-2019), we estimate the total area of nitrate hotspots in Europe to be 401,000 km2, with 47% occurring outside of Nitrate Vulnerable Zones (NVZs). We also found contrasting increasing or decreasing trends, varying per country and time periods. We estimate that only 5% of the 122,000 km2 of hotspots in 2019 will meet nitrate quality standards by 2040 and that these may be offset by the appearance of new hotspots. Our results reveal that the effectiveness of the ND is limited by both time-lags between the implementation of good practices and pollution reduction and an inadequate designation of NVZs. Substantial improvements in the designation and regulation of NVZs are necessary, as well as in the quality of monitoring stations in terms of spatial density and information available concerning sampling depth, if the objectives of EU legislation to protect groundwater are to be achieved.

Comparative assessment on ammonia nitrogen adsorption onto a saline soil-groundwater environment: distribution, multi-factor interaction, and optimization using response surface methodology and artificial neural network

The adsorption of soil can reduce the leaching of NH₄⁺-N from the external environment into groundwater. The adsorption of NH₄⁺-N is affected by many factors. It is critical to use statistical model to quantitatively describe the effects of interaction between two or more factors on the system response. In this study, HJ-Biplot was used to analyze the correlation characteristics of soil water, salt, and nitrogen, and the response surface methodology and artificial neural network were used to statistically visualize the interaction between factors, including concentration, total dissolved solids (TDS), temperature, and pH. The results showed that the study soil was a typical saline soil, with maximum soil NH₄⁺-N content of 85.45 mg/kg. For the adsorption experiments of NH₄⁺-N on saline soils, the effects of factors on the adsorption capacity were assessed using the RSM model. The RSM model was coupled with an ANN to predict the adsorption of NH₄⁺-N by saline soils. The NH₄⁺-N concentration and water pH were both significant at a linear level (p < 0.0001). The interaction between NH₄⁺-N concentration and pH was also more significant (p < 0.01). Under optimal conditions (concentration: 800 mg/L; temperature: 24 °C; TDS: 637 mg/L; pH: 7.83), the NH₄⁺-N adsorption capacity was 1650.2 ug/g, which was in general agreement with the calculated values from the Box-Behnken and RSM model. In addition, a statistical error criterion for the model showed that the RSM-ANN model had greater predictive ability than RSM model.

Variation and internal-external driving forces of grey water footprint efficiency in China's Yellow River Basin

Grey water footprint (GWF) efficiency is a reflection of both water pollution and the economy. The assessment of GWF and its efficiency is conducive to improving water environment quality and achieving sustainable development. This study introduces a comprehensive approach to assessing and analyzing the GWF efficiency. Based on the measurement of the GWF efficiency, the kernel density estimation and the Dagum Gini coefficient method are introduced to investigate the spatial and temporal variation of the GWF efficiency. The Geodetector method is also innovatively used to investigate the internal and external driving forces of GWF efficiency, not only revealing the effects of individual factors, but also probing the interaction between different drivers. For demonstrating this assessment approach, nine provinces in China's Yellow River Basin from 2005 to 2020 are chosen for the study. The results show that: (1) the GWF efficiency of the basin increases from 23.92 yuan/m3 in 2005 to 164.87 yuan/m3 in 2020, showing a distribution pattern of "low in the western and high in the eastern". Agricultural GWF is the main contributor to the GWF. (2) The temporal variation of the GWF efficiency shows a rising trend, and the kernel density curve has noticeable left trailing and polarization characteristics. The spatial variation of the GWF efficiency fluctuates upwards, accompanied by a rise in the overall Gini coefficient from 0.25 to 0.28. Inter-regional variation of the GWF efficiency is the primary source of spatial variation, with an average contribution of 73.39%. (3) For internal driving forces, economic development is the main driver of the GWF efficiency, and the interaction of any two internal factors enhances the explanatory power. For external driving forces, capital stock reflects the greatest impact. The interaction combinations with the highest q statistics for upstream, midstream and downstream are capital stock and population density, technological innovation and population density, and industrial structure and population density, respectively.

Effect of hydraulic retention time on the electro-bioremediation of nitrate in saline groundwater

Bioelectrochemical systems (BES) have proven their capability to treat nitrate-contaminated saline groundwater and simultaneously recover value-added chemicals (such as disinfection products) within a circular economy-based approach. In this study, the effect of the hydraulic retention time (HRT) on nitrate and salinity removal, as well as on free chlorine production, was investigated in a 3-compartment BES working in galvanostatic mode with the perspective of process intensification and future scale-up. Reducing the HRT from 30.1 ± 2.3 to 2.4 ± 0.2 h led to a corresponding increase in nitrate removal rates (from 17 ± 1 up to 131 ± 1 mgNO₃^--N L^-1d^-1), although a progressive decrease in desalination efficiency (from 77 ± 13 to 12 ± 2 %) was observed. Nitrate concentration and salinity close to threshold limits indicated by the World Health Organization for drinking water, as well as significant chlorine production were achieved with an HRT of 4.9 ± 0.4 h. At such HRT, specific energy consumption was low (6.8·10^-2 ± 0.3·10^-2 kWh g^-1NO₃^--N_removed), considering that the supplied energy supports three processes simultaneously. A logarithmic equation correlated well with nitrate removal rates at the applied HRTs and may be used to predict BES behaviour with different HRTs. The bacterial community of the bio-cathode under galvanostatic mode was dominated by a few populations, including the genera Rhizobium, Bosea, Fontibacter and Gordonia. The results provide useful information for the scale-up of BES treating multi-contaminated groundwater.

Nitrate removal by combining chemical and biostimulation approaches using micro-zero valent iron and lactic acid

The occurrence of nitrate is the most significant type of pollution affecting groundwater globally, being a major contributor to the poor condition of water bodies. This pollution is related to livestock-agricultural and urban activities, and the nitrate presence in drinking water has a clear impact on human health. For example, it causes the blue child syndrome. Moreover, the high nitrate content in aquifers and surface waters significantly affects aquatic ecosystems since it is responsible for the eutrophication of surface water bodies. A treatability test was performed in the laboratory to study the decrease of nitrate in the capture zone of water supply wells. For this purpose, two boreholes were drilled from which groundwater and sediments were collected to conduct the test. The goal was to demonstrate that nitrate in groundwater can be decreased much more efficiently using combined abiotic and biotic methods with micro-zero valent iron and biostimulation with lactic acid, respectively, than when both strategies are used separately. The broader implications of this goal derive from the fact that the separate use of these reagents decreases the efficiency of nitrate removal. Thus, while nitrate is removed using micro-valent iron, high concentrations of harmful ammonium are also generated. Furthermore, biostimulation alone leads to overgrowth of other microorganisms that do not result in denitrification, therefore complete denitrification requires more time to occur. In contrast, the combined strategy couples abiotic denitrification of nitrate with biostimulation of microorganisms capable of biotically transforming the abiotically generated harmful ammonium. The treatability test shows that the remediation strategy combining in situ chemical reduction using micro-zero valent iron and biostimulation with lactic acid could be a viable strategy for the creation of a reactive zone around supply wells located in regions where groundwater and porewater in low permeability layers are affected by diffuse nitrate contamination.

Valuation of ecosystem damage induced by soil-groundwater pollution in an arid climate area: Framework, method and case study

Groundwater is an important source of water, even the only source in some arid areas. However, climate changing and ecosystem damage induced by pollution aggravate water resource crisis. The "polluter pays" principle is deeply rooted in efforts to manage the polluted sites, particularly in the soil-groundwater environment. Unfortunately, there is no ecosystem damage compensation mechanism generally accepted by all stakeholders. In this study, we establish an assessment framework and valuation methods for ecosystem damage induced by soil-groundwater pollution in an arid climate area based on a "pollution source → target (soil-groundwater) → receptor (humans, animals, and plants) → damages → stakeholders (human society and ecosystem)" model that is usually applied in groundwater risk assessment research. Five economic loss are included in the valuation methods: (1) human health loss, (2) emergency disposal cost, (3) direct economic loss, (4) ecological restoration cost, and (5) ecosystem services loss. We apply the framework to a case study in an arid climate area, northwest China and calculate the total economic loss from ecosystem damage in the case study at 12.6 million yuan. The largest proportion of the total loss was the ecological restoration cost (85.6%), followed by the emergency disposal cost (11.2%), and finally ecosystem services loss (3.2%). Valuation of ecosystem damage from environmental pollution is essentially a socioeconomic issue. This study supplies a new framework and methods for valuing ecosystem damage induced by pollution, and offers suggestions for environmental management to reduce the damage caused by soil-groundwater pollution to health and ecosystems.

Judging the sources of inferior groundwater quality and health risk problems through intake of groundwater nitrate and fluoride from a rural part of Telangana, India

Evaluation of groundwater quality and related health hazards is a prerequisite for taking preventive measures. The rural region of Telangana, India, has been selected for the present study to assess the sources and origins of inferior groundwater quality and to understand the human health risk zones for adults and children due to the consumption of nitrate ([Formula: see text])- and fluoride (F^-)-contaminated groundwater for drinking purposes. Groundwater samples collected from the study region were determined for various chemical parameters. Groundwater quality was dominated by Na⁺ and [Formula: see text] ions. Piper's diagram and bivariate plots indicated the carbonate water type and silicate weathering as a main factor and man-made contamination as a secondary factor controlling groundwater chemistry; hence, the groundwater quality in the study region is low. According to the Groundwater Quality Index (GQI) classification, 48.3% and 51.7% of the total study region are excellent (GQI: < 50) and good (GQI: 50 to 100) water quality types, respectively, for drinking purposes. However, [Formula: see text] ranged from 0.04 to 585 mg/L, exceeding the drinking water quality limit of 45 mg/L in 34% of the groundwater samples due to the effects of nitrogen fertilizers. This was supported by the relationship of [Formula: see text] with TDS, Na⁺, and Cl^-. The F^- content was from 0.22 to 5.41 mg/L, which exceeds the standard drinking water quality limit of 1.5 mg/L in 25% of the groundwater samples. The relationship of F^- with pH, Ca²⁺, Na⁺, and [Formula: see text] supports the weathering and dissolution of fluoride-rich minerals for high F^- content in groundwater. They were further supported by a principal component analysis. The Health Risk Index (HRI) values ranged from 0.20 to 20.10 and 0.36 to 30.90 with a mean of 2.82 and 4.34 for adults and children, respectively. The mean intensity of HRI (> 1.0) was 1.37 times higher in children (5.70) than in adults (4.16) due to the differences in weight size and exposure time. With an acceptable limit of more than 1.0, the study divided the region into Northern Safe Health Zone (33.3% for adults and 28.1% for children) and Southern Unsafe Health Zone (66.7% for adults and 71.9% for children) based on the intensity of agricultural activity. Therefore, effective strategic measures such as safe drinking water, denitrification, defluoridation, rainwater harvesting techniques, sanitary facilities, and chemical fertilizer restrictions are recommended to improve human health and protect groundwater resources.

Groundwater Quality Affected by the Pyrite Ash Waste and Fertilizers in Valea Calugareasca, Romania

The aim of the study was to assess the groundwater quality in a rural area affected by the abandoned pyrite ash waste dumps. The abundance of major ions in groundwater depends largely on the nature of the rocks, climatic conditions, and mobility. To evaluate geochemical processes, 30 groundwater samples collected from Valea Calugareasca, Prahova County, Romania, were analyzed for the major anions (NO3−, SO42−, Cl−, HCO3−, and F−) and cations (Ca2+, Mg2+, Na+, and K+), which are naturally highly variable due to climatic and geographical location conditions. Ca2+, Na+, Mg2+, and K+ varied between 118 and 275 mg/L, 32 and 160 mg/L, 12.2 and 78.4 mg/L, and 0.21 and 4.48 mg/L, respectively. NO3− levels exceeding the World Health Organization (WHO) limit of 50 mg/L were identified in 17% of the groundwater samples, mainly as result of fertilizers applied to agricultural activities. The hydrogeochemical study identified dolomite dissolution and halite precipitation as natural sources of ions as well as the presence of pyrite as a source of SO42− ions in 60% of the samples. The sulfate content varied between 125 and 262 mg/L. Bicarbonate and chloride concentrations varied between 202 and 530 mg/L and 21 and 212 mg/L. The saturation index indicates the contribution of Ca2+ ions in the groundwater samples came from some processes of dissolving rocks such as aragonites (values between 1.27 and 2.69) and calcites (values between 1.43 and 2.82). Negative halite values indicated that salt accumulation results from precipitation processes. Only 10% of the analyzed groundwater samples were suitable for human consumption, the samples being situated on the hill, far away from the pyrite ash waste dumps and agricultural land.

Hydrogeochemical and health risk assessment in and around a Ramsar-designated wetland, the Ganges River Basin, India: Implications for natural and human interactions

Wetlands are the most productive and dynamic ecosystems, which have continuously been influenced by social and economic development. As a result, the pollution of wetland surface water and groundwater in adjacent regions has become an emerging global issue that requires constant monitoring and assessment. The current study investigates the natural and anthropogenic processes that influence surface and groundwater chemistry in and around Saman wetland (a Ramsar site) in the Ganges River Basin, India. Various physicochemical parameters are analyzed, and different hydrochemical indices are utilized to evaluate surface and groundwater quality for domestic and irrigation purposes. It is observed that the waters are alkaline in nature and dominated by moderately hard to hard types. An increase in the concentration of nitrate (NO₃^-) in Saman wetland water is noted, which is possibly due to the leaching of nitrogen ions primarily from fertilizers, pesticides, animal and human waste, and wastewater drained from brick and other factories. The elevated fluoride (F^-) content in studied groundwater samples is mainly governed by geogenic processes. Furthermore, surface and groundwater chemistry are mainly controlled by weathering reaction (rock-water interaction), excluding a few wetland surface water samples that are placed outside the boomerang-shaped boundaries of Gibb's diagram, which suggests evaporated dominance. Water Quality Index (WQI) estimation suggests that around 57% of groundwater samples have poor groundwater quality for drinking purposes. Estimation of irrigation water quality indices suggests that surface water of Saman wetland is permissible for irrigation purposes; however, none of the samples have excellent and good class as per sodium (alkali) hazard. Furthermore, health risk assessment showed that NO₃^- and F^- levels in the groundwater pose noncarcinogenic health effects, preferably to children, and thus is unfit for drinking purposes. For long-term water resource management and conservation of the Saman wetland, this study suggests proper awareness, appropriate remedial measures, and regular monitoring of the surface as well as groundwater quality monitoring in the study region.

Electrocatalytic Reduction of Nitrate via Co3O4/Ti Cathode Prepared by Electrodeposition Paired With IrO2-RuO2 Anode

Nitrate pollution is already a global problem, and the electrocatalytic reduction of nitrate is a promising technology for the remediation of wastewater and polluted water bodies. In this work, Co₃O₄/Ti electrodes were prepared by electrodeposition for the electrocatalytic reduction of nitrate. The morphology, chemical, and crystal structures of Co₃O₄/Ti and its catalytic activity were investigated. Then, the electrocatalytic nitrate reduction performance of Co₃O₄/Ti as the cathode was evaluated by monitoring the removal efficiencies of nitrate (NO₃⁻-N) and total nitrogen (TN), generation of reduction products, current efficiency (CE), and energy consumption (EC) at different operating conditions. Under the catalysis of Co₃O₄/Ti, NO₃⁻ was reduced to N₂ and NH₄⁺, while no NO₂⁻ was produced. After the introduction of chloride ions and IrO₂-RuO₂/Ti as the anode, NH₄⁺ was selectively oxidized to N₂. The removal efficiencies of NO₃⁻-N (at 100 mg/L) and TN after 2 h were 91.12% and 60.25%, respectively (pH 7.0; Cl⁻ concentration, 2000 mg/L; current density, 15 mA/cm²). After 4 h of operation, NO₃⁻-N and TN were completely removed. However, considering the EC and CE, a 2-h reaction was the most appropriate. The EC and CE were 0.10 kWh/g NO₃⁻N and 40.3%, respectively, and electrocatalytic performance was maintained after 10 consecutive reduction cycles (2 h each). The cathode Co₃O₄/Ti, which is prepared by electrodeposition, can effectively remove NO₃⁻-N, with low EC and high CE.

Machine Learning Algorithms for Modeling and Mapping of Groundwater Pollution Risk: A Study to Reach Water Security and Sustainable Development (Sdg) Goals in a Mediterranean Aquifer System

Groundwater pollution poses a severe threat and issue to the environment and humanity overall. That is why mitigative strategies are urgently needed. Today, studies mapping groundwater risk pollution assessment are being developed. In this study, five new hybrid/ensemble machine learning (ML) models are developed, named DRASTIC-Random Forest (RF), DRASTIC-Support Vector Machine (SVM), DRASTIC-Multilayer Perceptron (MLP), DRASTIC-RF-SVM, and DRASTIC-RF-MLP, for groundwater pollution assessment in the Saiss basin, in Morocco. The performances of these models are evaluated using the Receiver Operating Characteristic curve (ROC curve), precision, and accuracy. Based on the results of the ROC curve method, it is indicated that the use of hybrid/ensemble machine learning (ML) models improves the performance of the individual machine learning (ML) algorithms. In effect, the AUC value of the original DRASTIC is 0.51. Furthermore, both hybrid/ensemble models, DRASTIC-RF-MLP (AUC = 0.953) and DRASTIC-RF-SVM, (AUC = 0.901) achieve the best accuracy among the other models, followed by DRASTIC-RF (AUC = 0.852), DRASTIC-SVM (AUC = 0.802), and DRASTIC-MLP (AUC = 0.763). The results delineate areas vulnerable to pollution, which require urgent actions and strategies to improve the environmental and social qualities for the local population.

Consumption of water contaminated by nitrate and its deleterious effects on the human thyroid gland: a review and update

Nowadays, the nitrates have been established as carcinogenic components due to the endogenous formation of N-nitroso compounds, however, the consumption of water contaminated with nitrates has only been strongly related to the presence of methemoglobinemia in infants, as an acute effect, leaving out other side effects that demand attention. The thyroid gland takes relevance because it can be altered by many pollutants known as endocrine disruptors, which are agents capable of interfering with the synthesis of hormones, thus far, it is known that nitrates may disrupt the amount of iodine uptake causing most of the time hypothyroidism and affecting the metabolic functions of the organism in all development stages, resulting in an important health burden for the exposed population. Here, this review and update highlighted the impact of consumption of water contaminated with nitrates and effects on the thyroid gland in humans, concluding that nitrates could act as true endocrine disruptor.

Water Footprint of the Water Cycle of Gran Canaria and Tenerife (Canary Islands, Spain)

When it comes to exploiting natural resources, islands have limitations due to the quantity of these resources and the potential for harm to the ecosystem if exploitation is not done in a sustainable manner. This article presents a study of the water footprint of the different drinking water collection facilities and wastewater treatment facilities in the Canary Islands, in order to determine the blue, green, and grey water footprints in each case. The results show high percentages of drinking water losses, which raises the blue water footprint of the Canary Islands archipelago. The grey water footprint was studied in terms of Biochemical Oxygen Demand (BOD5). The green water footprint was not considered because it is a dimension of the water footprint mainly calculated for agricultural crops. Of the facilities studied, the wells for extraction of drinking water from the aquifer and the distribution network have the largest blue water footprint for the years under study (2019 and 2020). Only the wastewater treatment plants have a gray water footprint in this study, with values between 79,000 and 108,000 m3 per year. As a general conclusion, the most important factor in reducing the water footprint of the water cycle in the Canary Islands is optimization of the water resource, improving existing infrastructures to minimize losses, and implementing a greater circular economy that reuses water on a regular basis.

Nitrate runoff loss and source apportionment in a typical subtropical agricultural watershed

Nitrate (NO3-) loss and enrichment in water bodies caused by fertilization are a major environmental problem in agricultural areas. However, the quantitative contribution of different NO3- sources, especially chemical fertilizers (CF) and soil organic nitrogen (SON), to NO3- runoff loss remains unclear. In this study, a systematic investigation of NO3- runoff and its sources was conducted in a subtropical agricultural watershed located in Yujiang County, Jiangxi Province, China. A semi-monthly sampling was performed at the inlet and outlet from March 2018 to February 2019. Hydrochemical and dual NO3- isotope (15 N and 18O) approaches were combined to estimate the NO3- runoff loss and quantify the contribution of different sources with a Bayesian isotope mixing model. Source apportionment by Stable Isotope Analysis in R (SIAR) suggested that NO3- in runoff was mainly derived from nitrification of ammonium (NH4+) mineralized from SON (37-52%) and manure/sewage (M&S) (25-47%), while the contribution of CF was relatively small (14-25%). The contribution of various sources showed seasonal variations, with a greater contribution of CF in the wet growing season (March to August). Compared with the inlet which contributed 37-40% to runoff NO3-, SON contributed more at the outlet (49-52%). Denitrification in the runoff was small and appeared to be confined to the dry season (September to February), with an estimated NO3- loss of 2.73 kg N ha-1. The net NO3- runoff loss of the watershed was 34.5 kg N ha-1 yr-1, accounting for 15% of the annual fertilization rate (229 kg N ha-1 yr-1). Besides M&S (22%), fertilization and remineralization of SON (CF + SON) were the main sources for the NO3- runoff loss (78%), suggesting accelerated nitrification of NH4+ from CF (24%) and SON mineralization (54%). Our study indicates that NO3- runoff loss in subtropical agricultural watersheds is dominated by nonpoint source pollution from fertilization. SON played a more important role than CF. Besides, the contribution of sewage should not be neglected. Our data suggest that a combination of more rational fertilizer N application (CF), better management of SON, and better treatment of domestic sewage could alleviate NO3- pollution in subtropical China.

Nitrate in Groundwater Resources of Hormozgan Province, Southern Iran: Concentration Estimation, Distribution and Probabilistic Health Risk Assessment Using Monte Carlo Simulation

High nitrate concentration in drinking water has the potential to cause a series of harmful effects on human health. This study aims to evaluate the health risk of nitrate in groundwater resources of Hormozgan province in four age groups, including infants, children, teenagers, and adults, based on the US EPA methodology and Monte Carlo technique to assess uncertainty and sensitivity analysis. A Geographic Information System (GIS) was used to investigate the spatial distribution of nitrate levels in the study area. The nitrate concentration ranged from 0.3 to 30 mg/L, with an average of 7.37 ± 5.61 mg/L. There was no significant difference between the average concentration of nitrate in all study areas (p > 0.05). The hazard quotient (HQ) was less than 1 for all age groups and counties, indicating a low-risk level. The HQ95 for infants and children in the Monte Carlo simulation was 1.34 and 1.22, respectively. The sensitivity analysis findings showed that the parameter with the most significant influence on the risk of toxicity in all age groups was the nitrate content. Therefore, implementing a water resources management program in the study area can reduce nitrate concentration and enhance water quality.

Subclinical Hypothyroidism in Families Due to Chronic Consumption of Nitrate-Contaminated Water in Rural Areas with Intensive Livestock and Agricultural Practices in Durango, Mexico

Nitrate is a widely disseminated water pollutant and has been linked to health disorders, including hypothyroidism. Here, we evaluated the relationship between thyroid function and chronic exposure to nitrates in rural zone families, in addition to the genetic and autoimmune factors. Exposure and effect biomarkers, thyroid hormones, and autoantibodies of tiroperoxidase were measured, as well the presence of two FOXE1 polymorphisms (rs965513, rs1867277). Pearson’s correlation, principal component analysis, Kruskal–Wallis, and chi-squared tests were used for statistical analysis. A total of 102 individuals were analyzed; 45% presented subclinical hypothyroidism, a negative correlation was observed between methemoglobin and the total T3 (r = −0.43, p = 0.001) and free T3 levels (r = −0.34, p = 0.001), as well as between TSH and the free T4 (r = −0.41, p = 0.0001) and total T4 (r = −0.36, p = 0.0001). A total of 15.7% had positive antithyroid ab-TPO, while the polymorphic genotype (AA) represented only 3% (rs965513) and 4% (rs1867277) among subjects with subclinical hypothyroidism. The high frequency of subclinical hypothyroidism in the population under study could be related, mainly, to chronic exposure through the consumption of nitrate-contaminated water.

Water environmental pressure assessment in agricultural systems in Central Asia based on an Integrated Excess Nitrogen Load Model

Agricultural runoff is the main source of water pollution in Central Asia. Excessive nitrogen (N) inputs from overuse of chemical fertilizers are threatening regional water resources. However, the scarcity of quantitative data and simplified empirical models limit the reliability of grey water footprint (GWF), particularly in undeveloped regions. In this study, we developed an Integrated Excess Nitrogen Load Model (IENLM) to calculate excess N load and evaluate its potential water environmental pressure in Central Asia. The model optimized the biological N fixation and atmospheric N deposition modules by involving more environmental variables and human activities. Results showed that N fertilizer application contributed over 60% to total N input and was mainly responsible for 42.9% increase of total GWF from 101.5 to 145.0 billion m³ during 1992 - 2018. Water pollution level (WPL) increased from 0.55 in 1992 to 2.41 in 2018 and the pollution assimilation capacity of water systems has been fully consumed just by N load from agriculture since 2005. GWF intensity and grey water pollution - efficiency types in all Central Asian countries have improved in recent years except for Turkmenistan. N fertilizer application and agricultural economy development were the main driving factors induced N pollution. Results were validated by riverine nitrate concentrations and the estimates from prior studies. In future, combining the N fertilizer reduction with other farm management practices were projected to effectively improve the WPL. The modeling framework is favorable for N pollution research in data-scarce regions and provides a scientific basis for decision-making for agriculture and water resource managements.

Nitrates in the environment: A critical review of their distribution, sensing techniques, ecological effects and remediation

Nitrate pollution is eminent in almost all the developing nations as a result of increased natural activities apart from anthropogenic pollution. The release of nitrates in more than critical quantities into the water bodies causes accretion impacts on living creatures, environmental receptors, and human vigour by accumulation through the food chain. Nitrates have recently acquired researchers' huge attention and extend their roots in environmental contamination of surface and groundwater systems. The presence of nitrate in high concentrations in surface and groundwater triggers several health problems, for instance, methemoglobinemia, diabetes, eruption of infectious disorders, harmfully influence aquatic organisms. Sensing nitrate is an alternate option for monitoring the distribution of nitrate in different water bodies. Here we review electrochemical, spectroscopic, and electrical modes of nitrate sensing. It is concluded that, among the various sensors discussed in this review, FET sensors are the most desirable choice. Their sensitivity, ease of use and scope for miniaturisation are exceptional. Advanced functional materials need to be designed to satiate the growing need for environmental monitoring. Different sources of nitrate contamination in ground and surface water can be estimated using different techniques such as nitrate isotopic composition, co contaminants, water tracers, and other specialized techniques. This review intends to explore the research work on remediation of nitrate from wastewater and soil using different processes such as reverse osmosis, chemical denitrification, biological denitrification, ion exchange, electrodialysis, and adsorption. Denitrification proves as a promising alternative over previously reported techniques in terms of their nitrate removal because of its high cost-effectiveness.

Measurement and driving factors of grey water footprint efficiency in Yangtze River Basin

Water shortages and poor water quality have become an urgent problem that is constraining the sustainable development of China. Grey water has been found to bring greater stress on the water supply than freshwater consumption, and the grey water footprint (GWF) has received significant attention as a comprehensive indicator to assess wastewater pollution. In this study, we analysed the grey water footprint in the Yangtze River Basin from 2003 to 2017 and established a Logarithmic mean divisia index (LMDI) model to decompose the grey water footprint efficiency into six key factors. Our findings are as follows: (1) The average grey water footprint (AGWF) in the central regions was 40% higher than eastern region and 172% higher than western region; (2) Economic effects and capital deepening effects are the main factors affecting positive changes in grey water footprint efficiency; (3) Based on an analysis of the driving factors of greywater footprint efficiency in each province, we conducted a territorial classification according to the primary driving factors in each province. Our results reflect the spatial distribution characteristics of the influencing factors on the grey water footprint effect in the Yangtze River Basin and will enable the government to formulate relevant policies for each subregion.

Comparative health risk assessment of nitrate in drinking groundwater resources of urban and rural regions (Isfahan, Iran), using GIS

Infantile methemoglobinemia, thyroid disorders, and probably some carcinogenic effects are health concerns associated with dietary nitrate. Isfahan province has a dry and semi-arid desert climate such that the main source of various applications in this province is groundwater resources. This study evaluated spatial analysis of the groundwater NO₃^- concentrations and its possible health risk to residents. Method 8171 Hach was used for nitrate measurement of 1319 groundwater samples from March 2018 to February 2019. Non-carcinogenic risk due to NO₃^- exposure through consumption of drinking water was assessed, and the associated zoning maps were presented using geographic information system (GIS). Nitrate concentrations in the rural and urban areas were within 0.4-137 mg/L NO₃^- and 2.9-209 mg/L NO₃^-, respectively. Also, 226 (25%) and 104 (24%) of samples in the rural and urban areas, respectively, were detected above the Iran and WHO guideline NO₃^- values of 50 mg/L. The highest levels of NO₃^-, which were found in the western and central groundwater resources, occurred in the agricultural and residential areas. The NO₃^- concentrations were higher in urban than rural areas in the many studied counties. Also, nitrate was higher in wet seasons than in dry ones. Infants' non-carcinogenic risks were higher than the other groups. Infants (HQ > 1) were the most vulnerable group compared with the other groups in some counties. Thus, there are potential risks of methemoglobinemia, especially for infants. It is critical to adopt specific strategies to reduce the nitrate concentration in the studied groundwater.

Hydro-Stratigraphic Conditions and Human Activity Leading to Development of a Sinkhole Cluster in a Mediterranean Water Ecosystem

Salento Peninsula (Apulia, southern Italy) is characterised by many active sinkholes, which represent the main geological hazard. The stretch of coastline between the village of Casalabate and Le Cesine wildlife reserve is highly affected, with a system of dunes separating the low beach from extensive wetlands, which were subject to uncontrolled urban development after reclamation. The overall morphology is characterized by flat topography, whilst from a hydrogeological standpoint, the mixing of inland freshwater with advancing brackish water favours the higher aggressivity with respect to soluble rocks, and the development of enhanced dissolution (hyperkarst). The relict landscapes within the protected areas still allow for the recognition of actively occurring sinkholes, which cause damage to houses, the road network and infrastructures. In this article the case of Aquatina di Frigole is described, where in the last 15 years numerous sinkholes have formed, with the processes still in rapid evolution. Detailed surveys allow for to identification of the mechanisms of sinkhole formation (suffusion sinkholes), the deriving cluster, and the main hydrogeological links among the different water bodies in the area. Acquatina di Frigole provides an excellent natural laboratory to observe development and evolution of sinkholes, and their relationships with the stratigraphic and hydrogeological elements.

Physico-Chemical Parameters and Health Risk Analysis of Groundwater Quality

Groundwater pollution is a very common problem worldwide, as it poses a serious threat to both the environment and the economic and social development and consequently generates several types of costs. The analysis of pollution control involves a permanent comparison between pollution costs and the costs associated with various methods of pollution reduction. An environmental policy based on economic instruments is more effective than an environmental policy focused on command and control tools. In this respect, the present paper provides a case study showing how anthropogenic factors such as wastewater, industrial, agricultural, and natural factors are able to change the physical and chemical parameters of groundwater in the study area, thus endangering their quality. In order to monitor the groundwater quality in the region of Dobrudja, an analysis of physico-chemical parameters was performed. The content of heavy metals was analyzed and the health risk index was taken into account and analyzed, in order to set a better correctness of the metal content from the underground waters. Studies on groundwater quality control have shown that, in many parts of the world, water has different degrees of quality depending on the natural and anthropogenic factors acting on the pertaining environment. This is why more attention should be paid to the prevention of groundwater pollution and the immediate remediation of accidents.

The Water Safety Plan Approach: Application to Small Drinking-Water Systems-Case Studies in Salento (South Italy)

BACKGROUND

The quality of water for human consumption is an objective of fundamental importance for the defense of public health. Since the management of networks involves many problems of control and efficiency of distribution, the Water Safety Plan (WSP) was introduced to address these growing problems.

METHODS

WSP was applied to three companies in which the water resource assumes central importance: five water kiosks, a third-range vegetable processing company, and a residence and care institution. In drafting the plan, the terms and procedures designed and tested for the management of urban distribution systems were applied to safeguard the resource over time.

RESULTS

The case studies demonstrated the reliability of the application of the model even to small drinking-water systems, even though it involved a greater effort in analyzing the incoming water, the local intended use, and the possibilities for managing the containment of the dangers to which it is exposed. This approach demonstrates concrete effectiveness in identifying and mitigating the dangers of altering the quality of water.

CONCLUSIONS

Thanks to the WSP applied to small drinking-water systems, we can move from management that is focused mainly on verifying the conformity of the finished product to the creation of a global risk assessment and management system that covers the entire water supply chain.

Identifying the sources of nitrate contamination using a combined dual isotope, chemical and Bayesian model approach in a tropical agricultural river: Case study in the Mun River, Thailand

Environmental issues triggered by increasing nitrate in agricultural river has become global concern. Identifying nitrate sources and transformation are crucial for water sources protection and eliminating nitrate contamination in an agricultural watershed. In this study, chemical and dual isotopic compositions of nitrate were employed to trace the nitrate sources and transformation processes, and proportional contribution of NO₃^- source were estimated by SIAR based on Bayesian model. NH₄⁺ concentrations in middle Mun and lower Mun in wet season were significantly higher than NO₃^-, suggesting enhanced runoff processes by flood promote agricultural fertilized NH₄⁺ leaching into the river. Higher Cl^- concentration and NO₃^-/Cl^- indicated that manure and sewage was the dominate nitrate source in the Lam Takhong River and the upper Mun. The overall values of δ¹⁵N-NO₃^- and δ¹⁸O-NO₃^- ranged from -3.9‰ to +16.6‰ and from -5.2‰ to +40.0‰, respectively. The results of nitrate isotopes indicated that NO₃^- mainly originated from soil N nitrogen, chemical fertilizer, and manure and sewage wastes. Spatially, soil N and chemical fertilizer contributed the most nitrate in the mainstream of lower Mun, middle Mun, and the Lam Takhong River; whereas over 60% of nitrate was derived from manure and sewage in the upper Mun. The spatial variation of water discharge and rainfall, together with the nitrate concentration and isotopes inferred that the nitrate sources and transformations in rain-fed river in tropical zone were distinguished from other rivers. High water discharge driven by rainfall events accelerated the nitrate export and the contribution of atmospheric deposition in wet season, and enlarged the contribution of manure and sewage in dry season. This study provided an example for further researches and approaches to assess the effects of tropical climate and agriculture on nitrate accumulation in watershed.

Advances in Circular Bioeconomy Technologies: From Agricultural Wastewater to Value-Added Resources

This review systematically outlines the recent advances in the application of circular bioeconomy technologies for converting agricultural wastewater to value-added resources. The properties and applications of the value-added products from agricultural wastewater are first summarized. Various types of agricultural wastewater, such as piggery wastewater and digestate from anaerobic digestion, are focused on. Next, different types of circular technologies for recovery of humic substances (e.g., humin, humic acids and fulvic acids) and nutrients (e.g., nitrogen and phosphorus) from agricultural wastewater are reviewed and discussed. Advanced technologies, such as chemical precipitation, membrane separation and electrokinetic separation, are evaluated. The environmental benefits of the circular technologies compared to conventional wastewater treatment processes are also addressed. Lastly, the perspectives and prospects of the circular technologies for agricultural wastewater are provided.

Formation mechanism and step effect analysis of the crop gray water footprint in rice production

Gray water footprint (GWF) is a simple and efficient indicator to quantify water pollution that has received extensive attention. Previously, an agricultural GWF was estimated by assuming the nitrogen loss rate throughout the crop cycle, while the field chemicals accompanying water movement during crop growth were not considered. In this study, using field observations of water and nitrogen transport in Nanjing, China, the GWF was calculated at the time steps of a day (GWF_d), sub-growth period (GWF_s), and whole crop season (GWF_w), and its formation mechanism and step effect in rice production were explored. Field drainage and leakage caused nitrogen loss and generated a GWF, with the latter occurring intermittently. The values of GWF_d, GWF_s, and GWF_w from 2015 to 2018 were 0.42, 0.38, and 0.31 m³/kg, respectively, and the step effect exists temporally for the rice GWF. The GWF of paddy rice growth decreased as the measurement period increased and the time step was calculated using GWF_d as a reference. Herein, it was determined that the GWF_w used in previous studies may have greatly underestimated the adverse impact of the GWF on water quality, particularly in humid regions or years. Therefore, it is essential to identify the formation mechanism and appropriately select the time steps for GWF evaluation during rice production. This research provides methodological references for GWF assessment and reduction in crop production systems.

Sources and Consequences of Groundwater Contamination

Groundwater contamination is a global problem that has a significant impact on human health and ecological services. Studies reported in this special issue focus on contaminants in groundwater of geogenic and anthropogenic origin distributed over a wide geographic range, with contributions from researchers studying groundwater contamination in India, China, Pakistan, Turkey, Ethiopia, and Nigeria. Thus, this special issue reports on the latest research conducted in the eastern hemisphere on the sources and scale of groundwater contamination and the consequences for human health and the environment, as well as technologies for removing selected contaminants from groundwater. In this article, the state of the science on groundwater contamination is reviewed, and the papers published in this special issue are summarized in terms of their contributions to the literature. Finally, some key issues for advancing research on groundwater contamination are proposed.

Assessing the land use type and environment factors affecting groundwater nitrogen in an arid oasis in northwestern China

Identifying the magnitude and seasonal variability of groundwater nitrogen (N) under various land use types and quantifying the contribution of their environmental factors are of great importance when attempting to implement prioritizing effective strategies for mitigating groundwater N pollution. In this study, hydrochemical investigation was used to assess the magnitude and temporal variability of groundwater N in arid regions. Spatial distributions of N species (total N (TN), nitrate-N (NO₃^--N), ammonium-N (NH₄⁺-N), and nitrous-N (NO₂^--N)) were mapped using geostatistical techniques. Redundancy analysis (RDA) was conducted to determine environmental factors controlling hydrochemistry. The results showed that residential areas (town and village) and cropland had higher groundwater N concentrations than natural (forest and grassland) and unused land. And the concentrations of N species in rain season (August) were greater than those in the dry season (March) and normal season (November). The N species spatial patterns showed that there is a risk of TN and NO₃^--N pollution in groundwater of town and surrounding developed cropland, and that NH₄⁺-N and NO₂^--N pollution were negligible. Selected environmental factors explained a total of 77.4% of data variance in N concentrations. These factors indicated that water environmental factors (dissolved oxygen (DO), oxidation-reduction potential (ORP), water temperature (WT), and pH) affect groundwater concentrations and forms of N by influencing the process of nitrification and denitrification, which explained about 60% of the variance of the data. Approximately 10.8 and 8.3% of the variability was explained by shallow groundwater depth and soil texture, indicating that N concentrations in groundwater had heterogeneous influence. The high N excessive pollution ratio was observed in towns and cropland indicating that artificial N input is the main reason for groundwater N pollution in the study area. Hence, ameliorating anthropogenic agricultural practices and reducing N input in urban areas are critical to alleviating groundwater N pollution in the research area.

Use of environmental isotopes to assess groundwater pollution caused by agricultural activities

This work applied environmental isotope techniques to validate the results of previous studies on recharge sources in a rural area in central Chile (34.3° S and 71.3° W) and discern the origin of nitrate contamination in wells. Stream water and groundwater samples were taken during three surveys, two during spring snowmelt and one in low-water conditions. Chemical analyses included major cations and anions, isotope analyses included ¹⁸O-H₂O; ²H-H₂0; ³H-H₂0; ¹⁸O-NO₃ ^- and ¹⁵N-NO₃ ^-. The stable isotope data show that surface water and deep groundwater present depleted isotope values associated with recharge from the Andes Mountains and that shallow groundwater has more enriched isotope values that reflect the contribution of local recharge from rainwater infiltration. Depleted isotope values observed in shallow groundwater show the effect of recirculated river water used for irrigation. These results are consistent with the conceptual groundwater model developed in previous studies. Some wells have nitrate concentrations above the allowable limit for drinking water. The stable nitrogen isotopes indicate that nitrate is associated mainly with urea and ammoniacal fertilizers, and nitrate is attenuated by denitrification. The results of this study are relevant to improving management of groundwater resources used for drinking water.

PET-Bottled Water Consumption in View of a Circular Economy: The Case Study of Salento (South Italy)

Polyethylenterephtalate (PET) is the preferred packaging material in the bottled water industry and represents the main cause of waste production. This work investigated the drinking water consumption habits, with particular reference to PET-bottled water, of people living in the province of Lecce (Apulia Region, Southern Italy) by age and geographical groups. Their perception about the quality of tap water was also explored. The survey was performed by the administration of a questionnaire to 4137 citizens. Bottled mineral water was consumed by about the 90.4% of respondents with an average consumption of 387.7 L/year per capita (375.2 L/year in PET-bottles, 12.5 L/year in glass bottles). Public supply system was used by the 61.5% of respondents with an average consumption of 169.4 L/year per capita. The consumption of tap water was negatively related to the perception of its bad quality and the residence in a big city (Lecce); while it was positively associated with the age group ≤16 years old. Effective communications strategies must be developed in order to promote the consumption of tap water and implement good practice of circular economy.

The mixotrophic denitrification characteristics of Zoogloea sp. L2 accelerated by the redox mediator of 2-hydroxy-1,4-naphthoquinone

Denitrification in mixed culture system has been extensively researched to date, but few studies have focused on accelerating the process using redox mediators to promote electron transfer. Strain L2, an iron-reducing bacteria, can remove 75.44% of nitrate under temperature of 30.60 °C, pH of 6.75 and Fe²⁺ concentration of 27.86 mg·L^-1. Additionally, the removal rate of nitrate reached 1.516 mg·L^-1·h^-1 in 8 h with the addition of 0.030 mmol·L^-1 2-hydroxy-1,4-naphthoquinone (HNQ), which increased by 1.38 times than control group. Furthermore, analysis by fluorescence spectroscopy, flow cytometer and gas chromatography demonstrated that HNQ positively stimulated denitrification. This study provides a reference for enhancing denitrification in mixed culture and lays the foundation for the practical application of redox mediators in groundwater treatment.

Measures for reducing nitrate leaching in orchards:A review

Nitrogen (N) is one of the most important nutrients for plant growth. However, improper management of N fertilization in agriculture has led to a large amount of nitrate leaching, which is especially the case in fruit production systems. Studies have shown that high levels of nitrate in drinking water can cause harm to the human body. Excessive nitrate in rivers leads to eutrophication and damage to the ecological environment of the water. This study reviewed the measures and methods for reducing nitrate leaching in orchards. Some approaches for reducing nitrate leaching in orchards were evaluated, such as using grass cover, applying controlled-release N fertilizer, adding nitrification inhibitors, etc. These methods play important roles in reducing nitrate leaching in orchards, but more importantly, integrated measures are required to achieve agricultural sustainability and environmental protection goals.

Exploring environmental efficiency and total factor productivity of cultivated land use in China

During cultivated land use, nonseparable relationships exist between certain inputs and outputs. This study explored the influence of the nonseparable characteristics of input and output variables on both the cultivated land use environmental efficiency (CLUEE) and the cultivated land use environmental total factor productivity (CLUETFP). To evaluate China's CLUEE and CLUETFP from 1997 to 2017, we used the nonseparable hybrid model with undesirable outputs (NSH-U) and the nonseparable hybrid Malmquist (NSH-M) productivity index. The results showed the following: (1) The CLUEE differed significantly among regions, with the CLUEE decreasing from the eastern region to the western, northeastern, and central regions. We observed large differences in the CLUEE among provinces. (2) Nonradial input inefficiency and radial output inefficiency were the primary sources of cultivated land use environmental inefficiency. (3) Technical progress was the primary driving force behind the growth of CLUETFP across the entire country and in the eastern, central, western, and northeastern regions; however, technical efficiency limited the growth of CLUETFP to a certain extent. Finally, we proposed policy implications to improve China's CLUEE and CLUETFP.

Towards a Sustainable and Adaptive Groundwater Management: Lessons from the Benalup Aquifer (Southern Spain)

Reversing the chemical and quantitative impacts derived from human activity on aquifers demands a multidisciplinary approach. This requires, firstly, to update the hydrogeological knowledge of the groundwater systems, which is pivotal for the sustainable use of this resource, and secondly, to integrate the social, economic and administrative reality of the region. The present work focuses on the Benalup aquifer, whose exploitation plays a major role in the economy of the area, based mainly on irrigated agriculture. This activity has had negative consequences for the aquifer in quantitative and chemical terms, leading to its declaration as in poor condition. The study presented here shows the results obtained from the application of hydrogeological techniques, remote sensing and citizen participation tools, which have allowed us to deepen and improve the current knowledge of the system’s hydrogeological, geometric, administrative and social aspects. Additionally, the lessons learned from this case study are analyzed. The deficiencies detected are discussed, and alternatives aimed at the sustainable use of groundwater are proposed, such as the possibility of a joint use of surface and groundwater resources, the creation of a Water User Association responsible for the management of groundwater and the need for greater efforts aimed at educating and raising awareness of water conservation among citizens.

Grey water footprint evaluation and driving force analysis of eight economic regions in China

The grey water footprint (GWF) can be used to connect wastewater quality and quantity, making it a powerful tool for policy makers and those responsible for managing wastewater systems. As a supplementary to existing GWF research, this study explores the GWF evolution of eight economic regions in China by taking into consideration the GWF of livestock feeding. In addition, we use the logarithmic mean division index method to study the background driving forces of GWF in primary industry for eight economic regions. Results show that the overall GWF in China fluctuates from 6082 billion m³ to 6238 billion m³ between the years 2003 and 2015. Primary industry contributes most to the GWF because of livestock feeding, particularly for the northwest economic region, accounting for 84.81% in 2015. The southwest economic region has the highest total GWF, and east coast region has the lowest total GWF. An analysis of driving forces shows that economic scale and industrial structure are the driving forces that best explain the GWF for the East coast, middle of Yellow River, Northwest, and Southwest economic regions. The effects of economic scale and pollution producing intensity are driving the GWF in the Northeast Regions. For the North coast and middle Yangtze River Regions, economic scale, industrial structure, and pollution producing intensity are driving forces for GWF. While for the South coast region, population is an important contributor apart from economic scale and industrial structure. Policy implications from perspective of the agriculture GWF and endowment of different regions were finally discussed.

Development of a Universal Water Quality Index (UWQI) for South African River Catchments

The assessment of water quality has turned to be an ultimate goal for most water resource and environmental stakeholders, with ever-increasing global consideration. Against this backdrop, various tools and water quality guidelines have been adopted worldwide to govern water quality deterioration and institute the sustainable use of water resources. Water quality impairment is mainly associated with a sudden increase in population and related proceedings, which include urbanization, industrialization and agricultural production, among others. Such socio-economic activities accelerate water contamination and cause pollution stress to the aquatic environment. Scientifically based water quality index (WQI) models are then essentially important to measure the degree of contamination and advise whether specific water resources require restoration and to what extent. Such comprehensive evaluations reflect the integrated impact of adverse parameter concentrations and assist in the prioritization of remedial actions. WQI is a simple, yet intelligible and systematically structured, indexing scale beneficial for communicating water quality data to non-technical individuals, policymakers and, more importantly, water scientists. The index number is normally presented as a relative scale ranging from zero (worst quality) to one hundred (best quality). WQIs simplify and streamline what would otherwise be impractical assignments, thus justifying the efforts of developing water quality indices (WQIs). Generally, WQIs are not designed for broad applications; they are customarily developed for specific watersheds and/or regions, unless different basins share similar attributes and test a comparable range of water quality parameters. Their design and formation are governed by their intended use together with the degree of accuracy required, and such technicalities ultimately define the application boundaries of WQIs. This is perhaps the most demanding scientific need—that is, to establish a universal water quality index (UWQI) that can function in most, if not all, the catchments in South Africa. In cognizance of such a need, this study attempts to provide an index that is not limited to certain application boundaries, with a contribution that is significant not only to the authors, but also to the nation at large. The proposed WQI is based on the weighted arithmetic sum method, with parameters, weight coefficients and sub-index rating curves established through expert opinion in the form of the participation-based Rand Corporation’s Delphi Technique and extracts from the literature. UWQI functions with thirteen explanatory variables, which are NH3, Ca, Cl, Chl-a, EC, F, CaCO3, Mg, Mn, NO3, pH, SO4 and turbidity (NTU). Based on the model validation analysis, UWQI is considered robust and technically stable, with negligible variation from the ideal values. Moreover, the prediction pattern corresponds to the ideal graph with comparable index scores and identical classification grades, which signifies the readiness of the model to appraise water quality status across South African watersheds. The research article intends to substantiate the methods used and document the results achieved.

Water Quality Assessment: A Quali-Quantitative Method for Evaluation of Environmental Pressures Potentially Impacting on Groundwater, Developed under the M.I.N.O.Re. Project

Background: At global level, the vulnerability of aquifers is deteriorating at an alarming rate due to environmental pollution and intensive human activities. In this context, Local Health Authority ASL Lecce has launched the M.I.N.O.Re. (Not Compulsory Water Monitoring Activities at Regional level) project, in order to assess the vulnerability of the aquifer in Salento area (Puglia Region) by performing several non-compulsory analyses on groundwater samples. This first paper describes the quali-quantitative approach adopted under the M.I.N.O.Re. project for the assessment of environmental pressures suffered by groundwater and determines the number of wells to be monitored in specific sampling areas on the basis of the local potential contamination and vulnerability of the aquifer. Methods: We created a map of the entire Lecce province, interpolating it with a grid that led to the subdivision of the study area in 32 quadrangular blocks measuring 10 km × 10 km. Based on current hydrogeological knowledge and institutional data, we used GIS techniques to represent on these 32 blocks the 12 different layers corresponding to the main anthropic or environmental type of pressures potentially impacting on the aquifer. To each kind of pressure, a score from 0 to 1 was attributed on the basis of the potential impact on groundwater. A total score was assigned to each of the 32 blocks. A higher number of wells was selected to be monitored in those blocks presenting higher risk scores for possible groundwater contamination due to anthropic/environmental pressures. Results: The range of total scores varied from 2.4 to 42.5. On the basis of total scores, the 10 km × 10 km blocks were divided into four classes of environmental pressure (1st class: from 0,1 to 10,00; 2nd class: from 10,01 to 20,00; 3rd class: from 20,1 to 30,00; 4th class: from 30,01 to 42,50). There were 11 areas in the 1st class, 9 areas in the 2nd class, 8 areas in the 3rd class and 4 areas in the 4th class. We assigned 1 monitoring well in 1st class areas, 2 monitoring wells in 2nd class areas, 3 monitoring wells in 3rd class areas and 4 monitoring wells in 4th class areas. Conclusion: The methodology developed under the M.I.N.O.Re. project could represent a useful model to be used in other areas to assess the environmental pressures suffered by aquifers and the quality of the groundwater.

Enhancement of Tomato Plant Growth and Productivity in Organic Farming by Agri-Nanotechnology Using Nanobubble Oxygation

The development of technology to improve the mineralization of organic fertilizer and to enhance crop production is essential to achieve the transition from traditional farming to eco-friendly organic farming. Nanobubble oxygation (NB) was employed for comparison with traditional pump-aerated oxygation (AW) and a control group through both soil incubation and soil column experiments. Plant-available N and P contents in the NB treatment group were higher than those in the AW and control groups. Enzymatic activities including β-1,4-N-acetyl-glucosaminidase, phosphatase, α-1,4-glucosidase, β-1,4-xylosidase, peroxidase, and phenol oxidase were significantly higher in both oxygation groups compared with the control. The soil microbial biomass, activity, and diversity were also significantly improved due to the oxygation treatment. Additionally, the microbial metabolic functions were shifted in both oxygation treatments compared with the control group. The final tomato yield increase from the NB treatment group was 23%, and that from the AW treatment was 17%, compared with the control.

Nonpoint source pollution

A comprehensive review of the research papers published in 2018 focusing on nonpoint source (NPS) pollution is presented in this review article. The identification of pollution from different sources and estimation of NPS pollution using various models are summarized in this review paper. Various innovative techniques are also examined to abate NPS pollution. PRACTITIONER POINTS: The non-point source pollution in 2018 is systematically reviewed and documented. This review evaluates and summarizes the identification, quantification, reduction, and management of NPS pollution. Future perspectives of NPS pollution research are discussed.

Spatio-temporal variations of shallow and deep well groundwater nitrate concentrations along the Indus River floodplain aquifer in Pakistan

Excessive use of nitrogenous fertilizers and their improper management in agriculture causes nitrate contamination of surface and groundwater resources. This study was conducted along the seasonally flooded alluvial agricultural area of Indus River Basin to determine the spatial and temporal dynamics of nitrate concentrations in the groundwater along the river. Total of 112 samples were collected from shallow (30-40 ft) and deep groundwater (120-150 ft) wells at seven sites, 25 km apart from each other and covered an area of 170 km along the river, during four sampling campaigns between October 2016 to May 2017 i.e. in start, mid and end of dry season. The study period covered the whole agricultural cycle including the wet summer season with no agricultural activities under flooding and the sampling sites were always less than 2 km from the river bank. Nitrate concentrations of shallow wells were 15-54 and 20-45 mg L^-1 during the start and middle of dry season, respectively. However, at the end of the dry season, the highest nitrate concentrations of 35-75 mg L^-1 were recorded and 70% of these samples contained nitrate concentrations above the permissible limit 50 mg L^-1. Similar seasonal patterns of nitrate concentrations were observed in deep wells, however, δ¹⁸O data suggested lower recharge in deep well than shallow wells. The results illustrated that high nitrate concentrations in shallow wells were associated with high δ¹⁸O values indicating that the quantity of evaporated water infiltrated from the floodplain, possibly from distribution channels, along with the nitrate polluting shallow wells more than the deep wells. At the end of the dry season, nitrate concentrations exceeded the permissible limits in both shallow and deep wells, which possibly happened due to the horizontal movement of groundwater along with the nitrate mixing during vertical seepage of river water to the aquifers.

Identifying spatial heterogeneity of groundwater and its response to anthropogenic activities

With the rapid development of economy and society, the quality of groundwater is deteriorating under the dual influence of natural factors and anthropogenic factors, and it seriously threatens the safety of human drinking water. Identifying and analyzing the impact of anthropogenic activities is the key to solving this problem. Based on the groundwater problem in Changle County, Shandong Province, P.R. China, 43 groundwater samples were taken and tested. The statistical characteristics of the monitoring data, the groundwater chemical types, spatial distribution of groundwater, and influencing factors were analyzed by using enrichment factor, Mahalanobis distance, grey water footprint, and so on. The analysis results show that the overall water quality of Changle County is poor, and the main over-standard ions are Cl- , SO2- 4, and NO- 3. There is obvious spatial heterogeneity in the groundwater quality. The spatial variation of NO- 3 is affected by structural factors (topography, hydrology, etc.) and random factors (industrial, agricultural, etc.), and the spatial variability of NO- 3 is the most significant. Other water quality indicators are mainly affected by structural factors. The mass concentration of most ions decreases gradually from north to south, and the overall water quality in the southern region is better than that in the northern region. Thus, the supervision of chemical fertilizers and pesticides should be strengthened. The advanced treatment and reuse of wastewater from industrial parks should be promoted to improve the quality of groundwater and ensure the safety of human drinking water.

Residents perceptions of non-dietary pesticide exposure risk. Knowledge gaps and challenges for targeted awareness-raising material in Italy

Currently there are no tools to accurately estimate pesticides exposure risk for residents and bystanders. European Member States have to develop specific measures and communication strategies to prevent and minimize non-occupational pesticides exposure. Moreover, these measures should be compliant with the requirements of the Directive on Sustainable Use of Pesticides. Unfortunately, there is a high degree of uncertainties in the assessment of the non-dietary exposure risk for residents, therefore risk communication passes through a deep understanding of exposure risk perception. The objective of this pilot study is to assess citizens' risk perception of non-dietary exposure to pesticides, and to assist policy-makers and risk communicators in developing targeted awareness-raising materials for residents and bystanders. Through a household survey, conducted in the rural area of the province of Piacenza (IT) we investigated knowledge, health risk perceptions, and information sources related to non-dietary exposure to agricultural pesticides in residents' indoor and outdoor environment. The factors that push individuals to give importance to several possible pollution sources and to mitigation measures or precaution, in order to protect themselves from possible exposure sources, were also investigated. Results show that even if the air quality of the residential area is not judged negatively, pesticides are perceived as air pollutants that could lead to an actual exposure and, are correlated to the health status. The perception of risk, however, does not seem to be dependent only on the distance between homes and fields. The interpretative hypothesis that the perception of the relationship between air quality and health is influenced by the cultural issue and by psycho-sensory factors and not supported by proper information, even if with some differences among age groups, it seems to be confirmed. To better transfer knowledge and communication, the commitment of those who are recognised as "competent" (doctors and researchers) is critical.

Adsorption of nitrate, phosphate, nickel and lead on soils: Risk of groundwater contamination

Agricultural activities pose a significant risk of groundwater pollution. Indeed, fertilizers and treated wastewater used for irrigation are, in part, responsible for the deterioration of groundwater and surface water quality. In some cases, soil may provide a protective barrier against this pollution, but this depends on the nature of the soil and the contaminant. This work presents the effect of the soil clay content on the retention of four different pollutants in order to evaluate the risk they represent for the groundwater. These contaminants are generated by two main agricultural activities: 1/soil fertilization with phosphate and nitrate fertilizers and 2/irrigation with treated wastewater in which heavy metals such as nickel and lead are persistent. Firstly, the characterization of the sand and clay used in this work was performed and showed a cation exchange capacity of 1.24 and 25 meq/100 g, a specific surface area of 0.12 and 67.98 m²/g and a percentage of organic matter of 0.15 and 2% for sand and clay, respectively. The retention isotherms on all pollutants and the Langmuir, Freundlich, Freundlich-Langmuir, Hill and Koble-Corrigan models were applied. All experimental isotherms have been successfully adjusted using the Koble-Corrigan expression. The amounts of nitrates, phosphates, nickel and lead retained by the sandy soil, for an initial pollutant concentration equal to 1 meq/L, were evaluated at 0.29, 3.89, 5.97 and 8.56 μeq/g respectively. In contact with a soil containing 30% clay, the adsorbed amounts were estimated at 3.55, 15.00, 6.97 and 8.79 μeq/g for nitrates, phosphates, nickel and lead, respectively. These results mean that the pollutants that pose the greatest risk of groundwater contamination when carried by water through sandy soil are classified as follows lead < nickel < phosphate < nitrate while for a clayey soil, the classification becomes as follows: phosphates < lead < nickel < nitrate.

Rational trade-offs between yield increase and fertilizer inputs are essential for sustainable intensification: A case study in wheat-maize cropping systems in China

In order to feed a population of nearly 1.4 billion people with limited arable land resources, China's high crop production has been maintained by an intensive cropping system with excessive inputs of chemical fertilizers, resulting in high environmental costs. This study attempted to explore the reasonable balance between yield increase and nitrogen (N) inputs in the intensive wheat-maize cropping system in the North China Plain, which is one of the most important grain production regions in China. Based on yield simulations with the DSSAT-CERES-Wheat and DSSAT-CERES-Maize models and a household survey of 241 farmers' fields, we conducted a coupled analysis of the regional crop yields, N fertilizer inputs, and farmers' technical conversion efficiency with respect to winter wheat and summer maize production in four representative study areas. We also conducted a quantitative analysis of the equilibrium relationship between fertilizer application rates and expected yields, and the optimum N fertilization amounts for wheat and maize were recommended. The results indicated that farmers' average yields had reached almost 80% of the attainable yields, which meant that there was little room for farmers to increase their yields. However, we found that the yield gaps among the different farmers were still large, and most farmers applied excessive amounts of N while obtaining unsatisfactory yields due to poor fertilizer management techniques. Only 15% of winter wheat and 4% of summer maize on farmers' fields had achieved the synergy of high crop yields and efficient fertilization, and farmers' technical conversion efficiency was still relatively low. Therefore, farmers should be guided to appropriately lower their yield expectations and reduce the overuse of N fertilizer. In the future, if farmers receive necessary education and training and adopt advanced fertilizer management techniques, sustainable intensification of agricultural production with lower environmental costs will be feasible in China.