Search Results (2,689)

Hopeite (Zn₃(PO₄)₂·4H₂O) coatings, fabricated via zinc phosphate chemical conversion (ZPCC), have attracted considerable interest in biomedical applications owing to their excellent corrosion resistance and biocompatibility. However, the influence of calcium nitrate (CN) on coating properties remains poorly understood. This study systematically investigates the effect of CN concentration on the microstructure and corrosion behavior of ZPCC coatings deposited on stainless steel (SS). The phase composition, surface morphology, and elemental distribution were characterized using X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Electrochemical corrosion performance was assessed via potentiodynamic polarization in a 0.9 wt.% NaCl solution. The results indicate that CN concentration critically influences coating morphology, with higher concentrations leading to reduced crystal size and increased coating mass. Notably, the coating prepared with 6 g/L CN exhibited a dense, uniform, and fine-grained microstructure, resulting in superior corrosion resistance. Additionally, the optimized coating demonstrated strong interfacial adhesion, with a shear strength of 10.05 ± 1.2 MPa. Full article

In this study, the combined effects of influent carbon-to-nitrogen ratio (C/N = 0.8, 1.5, 2.5, 3.5, 4.5) and nitrate (NO₃⁻-N) concentration (40 and 80 mg/L, labeled as R₄₀ and R₈₀) on the partial denitrification (PD) performance were investigated using an intermittent sequencing batch reactor (SBR) process. With sodium acetate as an additional carbon source, the substrate variation, microbial diversity, and functional bacteria evolution were also explored to reveal the nitrite (NO₂⁻-N) accumulation mechanism at low temperatures (3–12 °C). The results showed that the 3.5-R₄₀ and 2.5-R₈₀ systems both presented the optimal NO₂⁻-N accumulation at a temperature of 10 °C, with the NO₂⁻-N transformation rate (NTR) of 66.89% and 76.79%, respectively. In addition, as the temperature reduced from 10 °C to 5 °C, the NO₂⁻-N accumulation performance was significantly suppressed, where the average effluent NO₂⁻-N of 3.5-R₄₀ (20.00 → 11.00 mg/L) and 2.5-R₈₀ (43.00 → 18.90 mg/L) systems reduced by nearly half. It is worth noting that there was almost no NO₂⁻-N accumulation at a C/N ratio of 0.8, although higher NO₃⁻-N concentration promoted NTR under the same C/N ratio. The high-throughput sequencing showed that the minimum Shannon value of 3.81 and the maximum Simpson value of 0.095 both occurred at a C/N ratio of 2.5, suggesting the downshifted microbial richness. Proteobacteria and Bacteroides increased significantly from 35.31% and 18.34% to 51.69–60.35% and 18.08–35.21%, as compared with the seeding sludge. Thauera and Flavobacterium as the main contributors to NO₂⁻-N accumulation accounted for 31.83% and 20.30% at the C/N ratio of 2.5 under a low temperature of 5 °C. The above discussion suggested that higher temperature (10 °C), lower C/N ratio (2.5–3.5), and higher NO₃⁻-N concentration (80 mg/L) were more favorable for the stable PD formation. Full article

Dry topsoil restricts root growth and nutrient uptake in arid regions, thereby significantly reducing crop yield. Hydraulic lift occurs due to the dry topsoil and wet deep soil. This study investigates the effects of topsoil drought intensity (three field capacities in topsoil: 60–70% (W1), 50–60% (W2), and 40–50% (W3)) and nitrogen application rate (N1: 120, N2: 240, and N3: 360 kg ha⁻¹) on cotton quality and the distribution of nitrogen in soil and plant under hydraulic lift using a root-splitting device. The upper pot of the root-splitting device was 22 cm high, with a 26 cm top diameter and a 23 cm bottom diameter; the lower pot of the root-splitting device was 45 cm high, with a 48 cm top diameter and a 36 cm bottom diameter. Topsoil moisture was maintained at W1 without nitrogen application under the control treatment (CK). The W2 and W3 treatments (representing different topsoil drought intensities) were designed to compare the interactive effects of water and nitrogen fertiliser on nitrogen distribution and cotton quality with the CK treatment. Results indicate that the concentrations of nitrate nitrogen (NO₃⁻-N) in the 10–20 cm soil were generally higher than those in the 0–10 cm soil. The topsoil drought intensity and nitrogen application rate had significant impacts on nitrogen concentrations in cotton organs. The W2 treatment produced the maximum nitrogen concentration, except for the root nitrogen concentration in 2021. The nitrogen concentration in the roots and stems peaked at 240 kg ha⁻¹ of nitrogen application rate. The topsoil drought intensity and nitrogen application rate had considerable influences on the cotton dry matter. The nitrogen application rate had a significant impact on the following indexes: internal nitrogen-fertiliser use efficiency (INUE), physiological nitrogen-fertiliser use efficiency (PNUE), and nitrogen-fertiliser recovery efficiency (NRE), except for PNUE in 2020. The INUE of other treatments decreased by 13.82–43.44% compared with CK treatment. In 2021, fibre length and elongation were significantly impacted by the topsoil drought intensity, nitrogen application rates, and their interactions. The nitrogen application rate’s effects on the uniformity index were significant in 2020 and 2021. The hydraulic lift magnitude, NRE, and NO₃⁻-N in the 0–10 cm soil were significantly correlated with each other. There were correlations among cotton quality indexes: fibre length and strength, uniformity index and micronaire, and micronaire and elongation. These findings provide a reference for future research on the mechanism by which hydraulic lift participates in nitrogen distribution in soil and crops and also offer a new direction to utilize deep water to improve the utilization rate of water resources. Full article

The present study aimed to evaluate crop characteristics, including morpho-anatomical features and nutritional and health-promoting composition, of head lettuce cultivated in greenhouses covered with transparent glass (control) and glass containing a red luminophore (red). The plant material comprised two lettuce types: butterhead and iceberg. Alterations were observed in head dimensions, morphology, and leaf mesophyll structure of plants from the red greenhouse. Butterhead lettuce plants exhibited unaltered head area under tested conditions but displayed a reduction in accumulated sugars and amino acids, resulting in a decline in dry matter content. Conversely, an increase in soluble and insoluble sugars and amino acid content, along with no change in nitrate content, was observed in iceberg lettuce. However, the growth intensity of iceberg lettuce decreased, while its dry matter content increased. Moreover, phenols and vitamin C concentration were lower in iceberg lettuce than in the butterhead one. In the red greenhouse, the phenolic content declined in both lettuce types, but vitamin C levels were reduced in butterhead lettuce and remained unchanged in iceberg lettuce. The data clearly demonstrate that the extent of variation in crop characteristics observed in lettuce cultivated in the red greenhouse depended on the tested lettuce type, with notable alterations occurring in iceberg lettuce. Full article

The research investigates nitrate and nitrite concentrations in vegetables sold at agri-food markets in Craiova, Dolj County. Vegetable samples were purchased from markets and sourced from the primary agricultural regions of Dolj County, ensuring a representative selection. A total of 300 samples were collected, with 20 samples taken from each of 15 vegetable species at commercial maturity. This research also aimed to estimate the contribution of each type of vegetable to the intake of nitrates/nitrites ingested through consumption, as well as to carry out an assessment of the risk to human health associated with the consumption of these vegetables. Our analysis showed that only three vegetables (tomatoes, eggplants, and bell peppers) exceeded the maximum permissible nitrate levels (MPL). The MPL for nitrite content was exceeded in several vegetables, including eggplant, green bean, lettuce, cabbage, dill, spinach, and lovage. For nitrates, the Hazard Risk Index (HRI) was consistently below 1 across all samples, with the sole exception of children’s consumption scenario. The HRI for nitrite was also below 1 for all samples, suggesting an absence of exposure risk. The findings from this study suggest that the consumption of vegetable products poses an insignificant risk in terms of nitrate and nitrite intake. Full article

Wheat is a crucial crop for human nutrition, and the demand for high-quality indicators within the “from farm to fork” concept is increasing. Based on this premise, this study examined how, at the farm level, the fertilization system can influence key quality indicators relevant to wheat production and final products. This research was conducted under specific conditions of the Western Plain of Romania at the Agricultural Research and Development Station (ARDS), Lovrin, during 2015–2017. Fertilization involved the autumn application of phosphorus (concentrated superphosphate; 0, 40, 80, 120, 160 kg ha⁻¹ active substance, a.s.) and potassium (potassium chloride; 0, 40, 80, 120 kg ha⁻¹ a.s.). Nitrogen (ammonium nitrate; 0, 30, 60, 90, 120 kg ha⁻¹ active substance) was applied in spring in two stages. The combination of these three fertilizers resulted in 18 fertilized variants (T2 to T19), tested alongside an unfertilized control (T1). The experimental variants were arranged in four randomized replications. Grain quality was assessed based on protein content (PRO, %), gluten (GLT, g 100 g⁻¹), gliadins (Gliad, %), glutenins (Glut, g 100 g⁻¹), high-molecular-weight glutenins (HMW, g 100 g⁻¹), low-molecular-weight glutenins (LMW, g 100 g⁻¹), and the gliadin/glutenin ratio (Gliad/Glut). Compared to the average values for each indicator across the experiment, certain variants produced values above the mean, with statistical significance. Variant T16 stood out by producing values above the mean for all indicators, with statistical confidence. Multivariate analysis showed that five indicators with very strong (PRO, GLT) and strong (HMW, Glut, LMW) influence grouped in PC1, while two indicators (Gliad, Gliad/Glut) with very strong and strong influence grouped in PC2. The analysis revealed varying levels of correlation between the applied fertilizers, with nitrogen (N) showing very strong and strong correlations with most indicators, while phosphorus and potassium showed moderate-to-weak correlations. Regression analysis generated mathematical models that statistically described how each indicator varied in relation to the fertilizers applied. Full article

This paper aims to assess the water quality of the Ismailia Canal, Egypt, in accordance with Article 49 of Law 92/2013. QUAL2K and Convolutional Neural Networks and Long Short-Term Memory (CNN-LSTM) are utilized to simulate the water quality parameters of dissolved oxygen (DO), pH, biological oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (TP), nitrate nitrogen (NO₃-N), and ammonium (NH₃-N) in winter and summer 2023. The parameters of the QUAL2K and CNN-LSTM models were calibrated and validated in both winter and summer through trial and error, until the simulated results agreed well with the observed data. Additionally, the model’s performance was measured using different statistical criteria such as mean absolute error (MAE), root mean square (RMS), and relative error (RE). The results showed that the simulated values were in good agreement with the observed values. The results show that all parameter concentrations follow and did not exceed the limit of Article 49 of Law 92/2013 in winter and summer, except for dissolved oxygen concentration (8.73–4.53 mg/L) in winter and summer, respectively, which exceeds the limit of 6 mg/L, and in June, biological oxygen demand exceeds the limit of 6 mg/L due to increased organic matter. It is imperative to compare QUAL2K and CNN-LSTM models because QUAL2K provides a physics-based simulation of water quality processes, whereas CNN-LSTM employs deep learning in modeling complex temporal patterns. The two models enhance prediction accuracy and credibility towards enabling enhanced decision-making for Ismailia Canal water management. This research can be part of a decision support system regarding maximizing the benefits of the Ismailia Canal. Full article

Nitrate pollution in water bodies has become a global environmental problem, and its excessive presence not only leads to eutrophication of water bodies but also threatens human health through the drinking water pathway. Therefore, it is urgent to develop new adsorbents with high adsorption capacity, good selectivity and excellent regeneration performance to solve the problem of nitrate pollution. In this study, reed straw (RS), trimethylamine-modified reed straw (MRS) and triethylamine-modified reed straw (ERS) were prepared by quaternary amination modification for nitrate removal. The adsorption performance, desorption performance, adsorption characteristics under disturbed environment and dynamic adsorption performance were investigated experimentally, and the adsorption mechanism was analyzed by various characterization means. The adsorption performance followed the order ERS (12.25 mg·g⁻¹) > MRS > RS, demonstrating that quaternary amination modification, particularly with triethylamine, significantly enhanced the NO₃⁻-N adsorption capacity. ERS exhibited excellent regeneration stability (over 80% after nine cycles) and high selectivity towards NO₃⁻-N in the presence of competing anions (Cl⁻, SO₄²⁻, humic acid). In the dynamic adsorption experiment, ERS had a breakthrough time of 290 min at a packing height of 3.3 cm, with an adsorption capacity of 10.74 mg·g⁻¹ and good adaptability to flow rate. In the actual wastewater application, the initial NO₃⁻-N removal rate was over 95%, the dynamic desorption rate reached 99.2% and the peak nitrate concentration of the desorbed solution reached 27 times of the initial value, confirming its high efficiency regeneration and enrichment ability. The study shows that the amine-modified reed straw adsorbent has a good potential for application and provides a new way for wastewater treatment plants to solve the problem of nitrate removal 12.25 mg·g⁻¹. Full article

Spinels like Co₃O₄ have acquired relevance because of their photocatalytic, electrocatalytic, optical and magnetic properties. In this context, we investigated the defect structure evolution of compounds synthetized using the nitrate precursor method and after annealing cycles at temperatures ranging from 260 to 650 °C by means of thermogravimetric analysis (TGA), neutron powder diffraction (NPD), X-ray powder diffraction (XRPD) coupled to Pair Distribution Function (PDF) analysis, and Density Functional Theory (DFT) calculations. Deuterated and hydrogenated precursors were adopted to produce the samples for NPD and XRPD experiments, respectively. TGA measurements displayed weight losses, the extent of which increased on lowering the preparation annealing temperature, suggesting that the adopted wet synthesis introduces structural water in the sample. Both XRPD and NPD revealed the presence of vacancies in tetrahedral cobalt sites ($V_{Co1}^{″}$) whose concentration at RT decreases on raising the annealing temperatures, while octahedral cobalt and oxygen sites were fully occupied in all the samples. In addition, the $V_{Co1}^{″}$ presence induces a shrinking of the volume of the CoO₄ tetrahedra. The combination of DFT calculation and diffraction revealed that deuterium/hydrogen ions ($D_i^{•}$/$H_i^{•}$), introduced during the synthesis by the nitrate precursor balanced the $V_{Co1}^{″}$. Finally, DFT calculations revealed that ($D_i^{•}$/$H_i^{•}$) in Co₃O₄ forms hydroxyl groups. Full article

Background: Heart failure with a preserved ejection fraction (HFpEF) accounts for approximately 50% of patients with heart failure. Endothelial dysfunction has been documented in HFpEF, and impaired nitric oxide (NO) production may be a contributing factor in patients decompensating from chronic to acute HFpEF. Plasma nitrite (NO₂⁻), but not plasma nitrate (NO₃⁻), is highly reflective of local nitric oxide production. However, plasma NO₂⁻ levels in relation to chronic and acute HFpEF patients have not been studied. Methods: Plasma NO₂⁻ and NO₃⁻ concentrations were quantified with gas-phase chemiluminescence. Plasma asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO production, and arterial stiffness were also quantified. Samples were collected from 19 participants with chronic HFpEF and 16 participants with acute HFpEF. Results: Plasma NO₂⁻ concentrations were lower in participants with acute HFpEF when compared to the chronic HFpEF group (p = 0.022). NO₃⁻, ADMA and indices of arterial stiffness did not display any significant between-group differences. Conclusions: We present novel NO₂⁻ data, which has not been previously quantified in patients with acute HFpEF. Our results indicate that plasma concentrations of NO₂⁻ may be decreased in patients with acute HFpEF compared to patients with chronic HFpEF, suggesting a dysregulated NO pathway. Further studies are required to confirm these findings in this patient population. Full article

Mismanagement of rural wastewater can lead to environmental contamination with the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Fungi with bioremediating potential constitute a sustainable alternative to decontaminate such wastewater before its reuse. This study evaluated the ability of Aspergillus oryzae pellets to remove 2,4-D from natural and sterile rural wastewater (i.e., with/without native microbiota). The pellets were produced by incubating conidial solutions of A. oryzae strains RCA2, RCA4, RCA5, and RCA10 in synthetic wastewater for 21 days at 25 °C. The wastewater samples were characterized physicochemically and microbiologically upon arrival at the laboratory. Afterwards, they were supplemented with 1, 2.5, or 5 mmol L⁻¹ of 2,4-D and inoculated with the pellets. Physicochemical characterization was repeated throughout the experiment. Herbicide removal and the presence of 2,4-D degradation intermediate, 2,4-dichlorophenol (2,4-DCP), were assessed through high-pressure liquid chromatography with UV/Vis detection (HPLC-UV) and mass spectrometry. At the beginning of the assay, the macro- and micronutrient content in the samples were suitable to sustain fungal growth. By the end, pH had increased and sodium and nitrate levels decreased in comparison with the control. RCA2, RCA4, and RCA10 removed over 80% of 2,4-D after 7 days of incubation, at the three herbicide concentrations tested. Moreover, wet fungal biomass had increased by the end of the assay. These findings demonstrate that RCA2, RCA4, and RCA10 can grow, form pellets, and remove 2,4-D in natural rural wastewater, which makes them potential candidates for bioremediation strategies aimed at improving the quality of water set to be reused. Full article

The evaluation of crop production that influences surface and groundwater quality is of growing importance in the context of agricultural sustainability in Europe. The primary aim of this study was to understand the relationship between gross nitrogen surplus in land and nitrate concentrations in surface and groundwater. The analysis was based on datasets collected from 2010 to 2021. Nitrate levels were categorized into three distinct quality classes based on the percentage of monitoring points, reflecting a spectrum from high quality, defined as nitrate levels below 25 mg/dm³, to poor quality, characterized by levels exceeding 50 mg/dm³. Redundancy analysis indicated that Gross Nitrogen Balance, a fertilizer use predictor, partially influences water quality, potentially due to long-term effects. Model selection for Gross Nitrogen Balance based on the AIC_c information criterion identified catch crops (or green cover), high-intensity agriculture, Natura 2000 sites, nitrogen-fixing plants, organic farming, fast-growing tree plantations, and EU27 states as predictors in the group of supported models. The best-fit model revealed differences between EU27 states for Gross Nitrogen Balance. Catch crops and Natura 2000 sites were also significant predictors, the former associated with a positive and the latter with a negative effect on nitrogen balance. In turn, WEI+ increased with nitrogen balance input but decreased with organic farming, indicating that promoting organic practices could help save water resources. Poland emerged as a country with relatively good water quality compared to several European counterparts, such as Denmark, Belgium, Malta, Czechia, Germany, and Lithuania. The implications of this research extend significantly to evaluation of the effects of the Common Agricultural Policy within the European Union. Full article

Nitrogen (N) is crucial for plant growth and stress resistance and is primarily absorbed and transported by nitrate transporters (NRT). Suaeda glauca, known for its strong salt-alkali stress resistance, and SgNRT genes have rarely been reported. This study aims to identify and analyze the SgNRT gene family to understand its composition, evolutionary patterns, and roles in salt stress responses. We identified 212 SgNRTs, which were categorized into three branches, with SgNRT1/SgNPF and SgNRT2 as the major families. Structural analysis, conserved domains, chromosomal localization, and collinearity were also examined. Spatiotemporal expression characteristics of SgNRT genes were analyzed, revealing specific expression across 13 organs or tissues and dynamic responses to salt treatment over 48 h. Notably, SgNRT1.185, SgNRT2.25, and SgNRT2.2 exhibited rapid salt induction in leaves (activated within 0.5 h, peaking at 2 h), with SgNRT1.185 showing relatively high upregulation. SgNRT1.185 and SgNRT2.35 were induced by high salt concentrations (200 mM) in both roots and leaves. SgNRT2.35 exhibited higher basal and stress-induced levels than the other genes. Bioinformatics analysis suggests spatially specific expression of SgNRT genes, potentially involved in nitrogen absorption and transport across various developmental stages and organs/tissues of Suaeda glauca. These findings offer a theoretical basis for understanding the adaptive strategies of Suaeda glauca under saline-alkali stress and provide insights into the functional evolution of plant NRT genes, aiding in the development of stress-resistant crops. Full article

Groundwater is a strategically important source of drinking water supply in the arid and rural regions of Kazakhstan. The objective of this study is to assess the quality of groundwater at 11 water intakes located in the Kordai, Shu, and Merke Districts of the Shu transboundary basin in the Zhambyl Region. A comprehensive assessment of physicochemical parameters was performed, including concentrations of nitrates, sulfates, chlorides, iron, manganese, and other constituents, with subsequent comparison against regulatory limits defined by Order No. 26 of the Ministry of Health of the Republic of Kazakhstan (dated 20 February 2023), GOST standards, and ST RK ISO standards. The findings revealed that a number of water intakes exceeded the maximum allowable concentrations for specific indicators, especially in areas subject to significant anthropogenic pressure. The most vulnerable sources were identified near settlements characterized by intensive agricultural practices and inadequate wastewater treatment systems. Spatial comparison of the results enabled the identification of potentially contaminated areas as well as aquifer zones suitable for drinking water supply. The study emphasizes the importance of regular groundwater monitoring and spatial analysis techniques (GIS) to enhance the reliability and comprehensiveness of water quality assessments. The data obtained in this study can serve as a basis for informed decision-making in the area of water resource protection and contribute to the achievement of United Nations Sustainable Development Goal 6 (SDG 6)—to ensure availability and sustainable management of water and sanitation for all. Full article

Plugs of lignite coal from multiple formations were subjected to a series of tests to determine the amount of rare-earth elements (REEs) to be extracted from coal in an in situ mining operation. These tests were used to determine if extraction of REEs and other critical minerals in an in situ environment would be possible for future attempts as an alternative to extraction mining. The tests involved subjecting whole lignite coal plugs from the Twin Butte coal seams in North Dakota to flow-through tests of water, and concentrations of 1.0 M ammonium nitrate, 1.0 M and 1.5 M sulfuric acid, and 1.0 M and 1.5 M hydrochloric acid (HCl) solvents at different concentrations and combinations. The flow-through testing was conducted by alternating the solvent and water flow-through to simulate an in situ mining scenario. The samples were analyzed for their concentrations of REEs (lanthanum [La], cerium [Ce], praseodymium [Pr], neodymium [Nd], samarium [Sm], europium [Eu], gadolinium [Gd], terbium [Tb], dysprosium [Dy], holmium [Ho], erbium [Er], thulium [Tm], ytterbium [Yb], lutetium [Lu], yttrium [Y], and scandium [Sc], as well as germanium [Ge] and cobalt [Co], manganese [Mn], nickel [Ni], and barium [Ba]). Results from the testing showed that REEs were extracted in concentrations that were on average higher using sulfuric acid (8.9%) than with HCl (5.8%), which had a higher recovery than ammonium nitrate. Tests were performed over a standard time interval for comparison between solvents, while a second set of testing was done to determine recovery rates of REEs and critical minerals under certain static and constant flow-through times to determine extraction in relation to time. Critical minerals had a higher recovery rate than the REEs across all tests, with a slightly higher recovery of light REEs over heavy REEs. Full article