Search Results (329)

Nitrogen-doped graphene-coated Fe nanoparticles (EC@N₆Fe_0.6-700) were synthesized through the pyrolysis of a durian peel-supported urea ferric salt mixture. These materials were subsequently utilized to activate peroxymonosulfate (PMS) for oxidation of terramycin (TEC). The incorporation of an optimal amount of urea and ferric nitrate during the synthesis of materials significantly improves the catalytic activity of the resulting catalysts after pyrolysis. Using EC@N₆Fe_0.6-700 catalyst at a concentration of 0.10 g L⁻¹, 98.55% oxidation of 20 mg L⁻¹ TEC is achieved within 60 min. Additionally, EC@N₆Fe_0.6-700 exhibits exceptionally low metal leaching, with levels remaining below 0.25 mg L⁻¹. The EC@N₆Fe_0.6-700 shows remarkable stability during oxidation and effectively resists interference, reusability, and robust stability throughout the oxidation process. The mechanism of the EC@N₆Fe_0.6-700/PMS/TEC system is determined, and the ¹O₂ is the main reactive oxygen species (ROSs). The XPS analysis confirms that the primary active sites are Fe⁰, as well as nitrogen-doped regions within the carbon matrix. This research demonstrates that by integrating iron and nitrogen with durian peel, it is possible to develop a PMS activator with satisfactory oxidation performance for the degradation of environmental pollutants. Full article

In the context of the disposal of spent radioactive fuel, heat-emitting radionuclides such as Cs and Sr are of utmost concern, as they have a major influence on the distance at which disposal galleries should be spaced apart and, thus, the cost of a disposal facility. Therefore, certain scenarios investigate the partitioning and transmutation of spent fuel to optimize the disposability of both Cs- and Sr-rich waste streams and the remaining fractions. In this study, the Cs- and Sr-rich waste stream, a nitrate-based solution, was immobilized in metakaolin and blast furnace slag-based alkali-activated matrices. These matrices were chosen for immobilization because they are known to offer advantages in terms of durability and/or heat resistance compared with traditional cementitious materials. The goal of this study is to develop an optimal recipe for the retention of Cs and Sr. For this purpose, recipes were developed following a design-of-experiments approach by varying the water-to-binder ratio, precursor, and waste loading while respecting matrix constraints. Leaching tests in deionized water showed that the metakaolin-based matrix was superior for the combined retention of both Cs and Sr. The optimal recipe was further tested under accelerated leaching conditions in an ammonium nitrate solution, which revealed that the leaching of Cs and Sr remained within reasonable limits. These results confirm that alkali-activated materials can be effectively used for the immobilization and long-term retention of heat-emitting radionuclides. Full article

Polymer-coated controlled-release fertilizers’ (CRFs) unique nutrient release mechanism has the potential to mitigate the leaching of mobile soil nutrients, such as nitrate-nitrogen (NO₃-N). The study aimed to evaluate the capacity of a polymer-coated CRFs to maintain maize (Zea mays L.) crop growth/health indicators and production goals, while reducing NO₃-N leaching risks compared to conventional (CONV) fertilizers in North Florida. Four CRF rates (168, 224, 280, 336 kg N ha⁻¹) were assessed against a no nitrogen (N) application and the current University of Florida Institute for Food and Agricultural Sciences (UF/IFAS) recommended CONV (269 kg N ha⁻¹) fertilizer rate. All CRF treatments, even the lowest CRF rate (168 kg N ha⁻¹), produced yields, leaf tissue N concentrations, plant heights, aboveground biomasses (AGB), and leaf area index (LAI) significantly (p < 0.05) greater than or similar to the CONV fertilizer treatment. Additionally, in 2022, the CONV fertilizer treatment resulted in increases in late-season movement of soil NO₃-N into highly leachable areas of the soil profile (60–120 cm), while none of the CRF treatments did. However, back-to-back leaching rainfall (>76.2 mm over three days) events in the 2023 growing season masked any trends as NO₃-N was likely completely flushed from the system. The results of this two-year study suggest that polymer-coated CRFs can achieve desirable crop growth, crop health, and production goals, while also having the potential to reduce the late-season leaching potential of NO₃-N; however, more research is needed to fully capture and quantify the movement of NO₃-N through the soil profile. Correlation and Principal Component Analysis (PCA) revealed that CRF performance was significantly influenced by environmental factors such as rainfall and temperature. In 2022, temperature-driven nitrogen release aligned with crop uptake, supporting higher yields and minimizing NO₃-N movement. In 2023, however, rainfall-driven variability led to an increase in NO₃-N leaching and masked the benefits of CRF treatments. These analyses provided critical insights into the relationships between environmental factors and CRF performance, emphasizing the importance of adaptive fertilizer management under varying climatic conditions. Full article

A pilot study with 18 dairy farms in recharge areas of five vulnerable drinking water abstractions in the Dutch province of Overijssel aimed to reduce nitrate leaching risks to the upper meter of groundwater through improved farm management. The pilot employed a voluntary, mutual gain approach, promoting measures that enhanced both nutrient efficiency and groundwater quality. Over the research period (2011–2017), nitrogen surpluses on the soil balance declined significantly from 153 to 96 kg N per ha per year, achieving the target of 100 kg N per ha per year. Despite this decline, average nitrate concentrations in the upper meter of groundwater fluctuated annually, showing no significant reduction in grassland but a noticeable decrease in maize. Economic evaluation showed that relative fodder profitability (RFP) increased over time, suggesting positive financial effects of implemented measures, as acknowledged by participating farmers. However, the adoption of measures perceived as complex or less financially rewarding remained limited, highlighting the challenges of relying solely on voluntary implementation. The absence of farm-specific feedback on nitrate leaching emerged as a critical limitation, emphasizing the need for additional monitoring tools, such as residual soil nitrogen assessments, to provide actionable insights at the farm or field level. These findings underscore the potential for further reducing nitrate leaching through enhanced feedback systems, precise execution of measures, and collaborative efforts integrating farmer expertise and scientific knowledge. Full article

Excessive application of nitrogen (N) fertilizers in agriculture poses significant environmental risks, notably nitrate leaching into groundwater. This study evaluates soil water dynamics and the transport of urea, ammonium, and nitrate under variable-saturated conditions in a long-term experimental field in Croatia, Europe. Utilizing HYDRUS-1D and HYDRUS-2D models, we simulated water flow and nitrogen transformation and transport across six lysimeter-monitored locations over four years (2019–2023), incorporating diverse crop rotations and N addition. Key modeled processes included nitrification, urea hydrolysis, and nitrate leaching, integrating field-measured parameters and climatic conditions. The models achieved high reliability, with R² values for water flow ranging from 0.58 to 0.97 and for nitrate transport from 0.13 to 0.97; however, some cases reported lower reliability. Results revealed that nitrate leaching was influenced by precipitation patterns, soil moisture, crop growth stages, and fertilization timing. Peak nitrate losses were observed during early crop growth and post-harvest periods when elevated soil moisture and reduced plant uptake coincided. The findings highlight the importance of optimizing nitrogen application strategies to balance crop productivity and environmental protection. This research demonstrates the effectiveness of numerical modeling as a tool for sustainable nitrogen management and groundwater quality preservation in agricultural systems. It also indicates the need for further development by capturing some of the processes such as identification in the N cycle. Full article

The application of metal–organic frameworks (MOFs) has attracted increasing attention in organic synthesis. The modification of MOFs can efficiently tailor the structure and improve the property for meeting ongoing demand in various applications, such as the alteration of gas adsorption and separation, catalytic activity, stability, and sustainability or reusability. In this study, carboxyethylsilanetriol (CEST) disodium salt was used as a dual-functional ligand for modified Al-MIL-53 to fabricate CEST-functionalized Al-MIL-53 samples through a hydrothermal reaction of aluminum nitrate, terephthalic acid, and CEST disodium salt by varying the molar ratio of CEST to terephthalic acid and keeping a constant molar ratio of Al³⁺/-COOH of 1:1. The structure, composition, morphology, pore feature, and stability were characterized by XRD, different spectroscopies, electron microscopy, N₂ physisorption, and thermogravimetric analysis. With increasing CEST content, CEST-Al-MIL-53 still preserves an Al-MIL-53-like structure, but the microstructure changed compared with pure Al-MIL-53 due to the integration of CEST. Such a CEST-Al-MIL-53 was used as the support to load Pd particles and afford a catalyst Pd/CEST-Al-MIL-53 for Suzuki–Miyaura C-C cross-coupling reaction of aryl halides and phenylboronic acid under basic conditions. The resulting Pd/CEST-Al-MIL-53 showed a high catalytic activity compared with Pd/Al-MIL-53, due to the nanofibrous structure of silicon species-integrated CEST-Al-MIL-53. The nanofiber microstructure undergoes a remarkable transformation into intricate 3D cross-networks during catalytic reaction, which enables the leachable Pd particles to orientally redeposit and inlay into these networks as the monodisperse spheres and thereby effectively preventing Pd particles from aggregation and leaching, therefore demonstrating a high catalytic performance, long-term stability, and enhanced reusability. Obviously, the integration of CEST into MOFs can effectively prevent the leaching of active Pd species and ensure the re-deposition during catalysis. Moreover, catalytic performance strongly depended on catalyst dosage, temperature, time, solvent, and the type of the substituted group on benzene ring. This work further extends the catalytic application of hybrid metal–organic frameworks. Full article

The unreasonable application of nitrogen (N) fertilizer leads to high nutrient losses and severe potential of agricultural non-point source contamination, which threatens water quality in the upper Yellow River Basin. Therefore, the aim of this study is to explore the effects of N application rates and various control measures on rice yield and N leaching in paddy fields in the Yellow River irrigation area. Four treatments were employed in this study, CK (no N fertilizer application, 0 kg N∙ha⁻¹), CRU (controlled-release urea application, 180 kg N∙ha⁻¹), OPT (optimal N fertilizer application, 210 kg N∙ha⁻¹), and FP (N fertilizer application based on farmer experience, 240 kg N∙ha⁻¹), to examine paddy yield, N use efficiency (NUE), N concentrations in leaching water at various soil depths, and N contents along the 0–100 cm depth of the soil profile. The results indicated that the amount of TN leached was 25.14–48.04 kg∙ha⁻¹ after different N applications, and the TN leaching coefficients of FP, OPT, and CRU were 10.88%, 11.27%, and 7.07%. Compared to FP and OPT, the CRU significantly reduced the concentrations of TN, ammonium N (NH₄⁺-N), and nitrate N (NO₃⁻-N) in the surface and soil water, with average TN leaching decreasing by 31.55% and 27.35% in the years 2022 and 2023, respectively. NO₃⁻-N was identified as the primary form of N leached from the paddy fields. Compared to FP and OPT treatments, the CRU treatment increased the average paddy yield by 19.99–20.66% and improved the average NUE by 19.04–16.38%. This study revealed that the application of high amounts of N positively affected soil N leaching, and controlled-release urea demonstrates superior efficacy compared to conventional fertilization. The application of controlled-release urea at a rate of 180 kg N∙ha⁻¹ not only ensures a good paddy yield but also reduce N losses, which should be recommended to local farmers. Full article

Soil fertilization with fertilizers derived from renewable sources is a topic of great interest in terms of the sustainable management of organic waste. To optimize the management of nitrogen supplied to the soil with digestates, it is necessary to deepen knowledge on the process of mineralization of organic nitrogen over time. In this research, a laboratory incubation system was utilized to study the impact of various digestate sources on nitrogen mineralization processes in soils and nitrogen mineralization kinetics. Six types of digestates of different origins and composition were administered to soil and the soil samples were placed under controlled conditions. The release of N was determined by measuring ammonium-N and nitrate-N concentrations in leachates during a 12-week period of incubation. The nonlinear regression technique was used to fit the cumulative leaching of total N to the Stanford and Smith first-order kinetic model during the incubation period. The results showed that the differences between digestates, nitrogen and organic carbon concentration, and C/N ratio influenced both ammonification and nitrification processes in the soil and the nitrogen mineralization kinetics. The processing of the statistical data highlighted that the potentially mineralizable nitrogen (MPN) followed first-order kinetics. Full article

Maize double-cropping production systems in Mediterranean areas have a great nitrogen extraction capacity and high nitrogen (N) requirements. This study aims to assess whether in these farming systems, animal manure can be applied, using adequate management practices, at levels exceeding the maximum annual amount of livestock manure established in the European Nitrate Directive for vulnerable zones (170 kg N ha⁻¹) without increasing the risk of water nitrate contamination. We compare the risk of nitrate leaching under two fertilisation strategies, one with synthetic fertilisers and the second with a maximised application of pig slurry, exceeding the limits of the EU Nitrate Directive, in two soil types. Crop yields, N extraction and nitrate concentrations below the crop root zone were not affected by the fertilisation strategies at each site. The results show that pig slurry can be applied above the limit of 170 kg N ha⁻¹ under the conditions of the study, up to 360 kg N ha⁻¹, without increasing the risk for nitrate leaching. Full article

Nitrate leaching from soil presents a significant threat to soil health, as it can result in nutrient loss, soil acidification, and structural damage. It is crucial to quantify the spatial heterogeneity of nitrate leaching and its drivers. A total of 509 observational data points regarding nitrate leaching in northern China were collected, capturing the spatial and temporal variations across crops such as winter wheat, maize, and greenhouse vegetables. A machine learning (ML) model for predicting nitrate leaching was then developed, with the random forest (RF) model outperforming the support vector machine (SVM), extreme gradient boosting (XGBoost), and convolutional neural network (CNN) models, achieving an R² of 0.75. However, the performance improved significantly after integrating the four models with Bayesian optimization (all models had R² > 0.56), which realized quantitative prediction capabilities for nitrate leaching loss concentrations. Moreover, the XGBoost model exhibited the highest fitting accuracy and the smallest error in estimating nitrate leaching losses, with an R² value of 0.79 and an average absolute error (MAE) of 3.87 kg/ha. Analyses of the feature importance and SHAP values in the optimal XGBoost model identified soil organic matter, chemical nitrogen fertilizer input, and water input (including rainfall and irrigation) as the main indicators of nitrate leaching loss. The ML-based modeling method developed overcomes the difficulty of the determination of the functional relationship between nitrate loss intensity and its influencing factors, providing a data-driven solution for estimating nitrate–nitrogen loss in farmlands in North China and strengthening sustainable agricultural practices. Full article

The integration of ecosystem services (ESs) valuation into agricultural policy frameworks is critical for fostering sustainable land management practices. This study leverages the redesigned version of the bio-economic farm model MODAM (Multi-Objective Decision Support Tool for Agro-Ecosystem Management) to estimate the shadow prices of ESs, enabling the derivation of demand and supply curves for nitrate leaching and soil erosion control, respectively. Two hypothetical farms in Brandenburg, Germany—a smaller, arable farm in Märkisch-Oderland and a larger, diversified farm with livestock in Oder-Spree—are analyzed to explore the heterogeneity in shadow prices and corresponding cropping patterns. The results reveal that larger farms exhibit greater elasticity in response to green taxes on nitrate use and lower costs for supplying erosion control compared to smaller farms. This study highlights the utility of shadow prices as proxies for setting green taxes and payments for ecosystem services (PESs), while emphasizing the need for differentiated policy designs to address disparities between farm types. This research underscores the potential of model-based ESs valuation to provide robust economic measures for policy design, fostering sustainable agricultural practices and ecosystem conservation. Full article

Effective nitrogen (N) management practices are essential for achieving efficient and sustainable agricultural production. The purpose of this study was to improve N use efficiency (NUE) and minimize N loss by optimizing the rate and type of N fertilizer application while maintaining a high yield of maize. A two-year field experiment with U (urea), S (slow-release N fertilizer), and SU (blending of S and U) under four N application levels (N1: 90 kg ha⁻¹, N2: 120 kg ha⁻¹, N3: 180 kg ha⁻¹, N4: 240 kg ha⁻¹) was conducted to investigate their effects on ammonia (NH₃) volatilization, residual soil nitrate N (${\mathrm{N}\mathrm{O}}_3^{-}-\mathrm{N}$), yield, NUE, apparent N losses of rainfed maize. NH₃ volatilization in SU and S were 38.46% and 16.57% lower than that in U, respectively. SU and S were found to reduce the apparent N losses by 42.98% and 62.23%. SU decreased ${\mathrm{N}\mathrm{O}}_3^{-}-\mathrm{N}$ leaching in deep soils and increased ${\mathrm{N}\mathrm{O}}_3^{-}-\mathrm{N}$ content in topsoil. Compared with U and S, SU significantly increased yield, plant N accumulation, and NUE. SUN4 achieved the maximum maize yield and plant N accumulation, averaging 7968.36 kg ha⁻¹ and 166.45 kg ha⁻¹. In addition, the high yield and NUE were obtained when the mixing ratio of S and U was 53–58% and the N application rate was 150–220 kg ha⁻¹. The findings highlight that SU effectively reduces N losses while ensuring high yield, which could be used as one of the optimal N fertilization strategies for rainfed maize in Northwest China. Full article

The black olm (Proteus anguinus parkelj Sket & Arntzen) is an endemic species found exclusively in the Dobličica River subterranean water systems of the Dinaric karst in southern Slovenia. These unique habitats are vulnerable to contamination due to rapid water flow, primarily from nitrates from agricultural fertilisers and untreated urban wastewater. The safe limit of nitrate concentration for olms is 9.2 mg NO₃⁻/L, yet measurements in karst springs have shown levels ranging from 3 mg to over 20 mg NO₃⁻/L. The SWAT modelling tool assessed agri-environmental and land use scenarios for their impact on nitrate leaching. Using the model, we identified hotspots with high nitrogen leaching potential that require immediate attention and implementation of better agricultural practices for fertiliser use. For these hotspots, the most effective approach combines scenarios of cover crops (R2), reduced fertilisation (R3), crop rotation (R4), and conversion of cropland to grassland (E2, E4, E5), potentially decreasing nitrate leaching by up to 60%. Implementing the best scenarios is expected to reduce nitrogen levels below the limit value of 9.2 mg NO₃⁻/L, essential for maintaining the black olm habitat. Full article

The demand for intensive agriculture to boost food and crop production has increased. High nitrogen (N) fertilizer use is crucial for increasing agricultural productivity but often leads to significant nitrate losses, posing risks to surface and groundwater quality. This study examines the role of biochar as a soil amendment to enhance nutrient retention and mitigate nitrate leaching. By improving nitrogen efficiency, biochar offers a sustainable strategy to reduce the environmental impacts of intensive agriculture while maintaining soil fertility. An incubation study investigated four biochar feedstocks: spruce bark biochar at 550 °C (SB550), hardwood biochar (75% sugar maple) at 500 °C (HW500), sawdust (fir/spruce) biochar at 427 °C (FS427), and softwood biochar at 500 °C (SW500), to identify the most effective nitrate adsorbent. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) were employed to analyze biochar morphology and surface functional groups. Adsorption isotherms were modeled using the Langmuir and Freundlich equations. The results indicated that surface functional groups, such as aromatic C=C stretching and bending, aromatic C–H bending, and phenolic O–H bending, play crucial roles in enhancing electrostatic attraction and, consequently, the nitrate adsorption capacity of biochar. The equilibrium adsorption data from this study fit well with both the Langmuir and Freundlich isotherm models. Among the four biochar types tested, SB550 exhibited the highest nitrate adsorption capacity, with a maximum of 184 mg/g. The adsorption data showed excellent conformity to the Langmuir and Freundlich models, with correlation coefficients (R²) exceeding 0.987 for all biochar types. These findings highlight the high accuracy of these models in predicting nitrate adsorption capacities. Full article

Winter catch crops are promoted in the European Union under the Common Agricultural Policy to improve soil health and reduce nitrate leaching from agricultural fields. Currently, Member States often monitor farmers’ adoption through on-site inspections for a limited subset of parcels. Because of its potential for region-wide coverage, this study investigates the potential of Sentinel-2 satellite time series to classify catch crops at the field level in Flanders (Belgium). The first objective was to classify catch crops and identify the optimal model and time-series input for this task. The second objective was to apply these findings in a real-world scenario, aiming to provide reliable early-season predictions in a separate target year, testing early-season performance and temporal transferability. The following three models were compared: Random Forest (RF), Time Series Forest (TSF), and a One-Dimensional Convolutional Neural Network (1D-CNN). The results showed that, with a limited field-based training dataset, RF produced the most robust results across different time-series inputs, achieving a median F1-score of >88% on the best dataset. Additionally, the early-season performance of the models was delayed in the target year, reaching the F1-score threshold of 85% at least one month later in the season compared to the training years, with large timing differences between the models. Full article