Search Results (1,277)

Understanding nitrogen (N) retention mechanisms in pristine humid temperate rainforest soils is critical for effective ecosystem management and nutrient conservation. The potential abiotic transformation of nitrite (NO₂⁻) into organic N forms in the absence of microbial activity in these ecosystems remains largely unexplored, despite its role in mitigating N leaching. This study focuses on the abiotic incorporation of nitrite (NO₂⁻) into dissolved organic nitrogen (DON) under anoxic conditions, a mechanistic step not directly evaluated in previous research, which employed ¹⁵N-labelled nitrate (NO₃⁻). To address this gap, we used ¹⁵N-labelled NO₂⁻ at 5 and 15 mg L⁻¹ in a lab incubation study under anoxic conditions to trace the contribution of abiotic nitrite transformation to organic N formation in organic matter-rich soils from temperate rainforests developed on both volcanic and non-volcanic parent materials. The added ¹⁵N declined rapidly after 15 min by 52% and 60% in both soil solutions, while it started to form labelled DON, increasing by 11% and 34%, after five days of incubation, with the highest accumulation at 15 mg L⁻¹ of ¹⁵N-NO₂⁻. These results show that up to 77% of the added ¹⁵N-NO₂⁻ can be abiotically incorporated into the DON of unpolluted old-growth temperate rainforest, whether developed on volcanic or non-volcanic soils. Nitrogen input has a stronger effect than soil parent material from which the soils originate. This reveals the natural resilience of unpolluted temperate rainforests to N loss, with implications for long-term ecosystem stability and nutrient cycling. Full article

The widespread contamination of aquatic environments by tetracycline antibiotics (TCs) poses a substantial threat to public health and ecosystem stability. Although photo-Fenton processes have demonstrated remarkable efficacy in degrading TCs, their practical application is limited by challenges associated with catalyst recyclability. This study reports the development of a novel magnetic recoverable SrFe₁₂O₁₉/g-C₃N₄ heterostructure photocatalyst synthesized via a facile one-step co-calcination method using industrial-grade precursors. Comprehensive characterization revealed that nitrogen defects and the formation of heterojunction structures significantly suppress electron (e⁻)–hole (h⁺) pair recombination, thereby markedly enhancing catalytic activity. The optimized 7-SFO/CN composite removes over 90% of oxytetracycline (OTC) within 60 min, achieving degradation rate constants of 0.0393 min⁻¹, which are 9.1 times higher than those of SrFe₁₂O₁₉ (0.0043 min⁻¹) and 4.2 times higher than those of g-C₃N₄ (0.0094 min⁻¹). The effectively separated e⁻ play three critical roles: (i) directly activating H₂O₂ to generate ·OH radicals, (ii) promoting the redox cycling of Fe²⁺/Fe³⁺ ions, and (iii) reducing dissolved oxygen to form ·O₂⁻ species. Concurrently, h⁺ directly oxidize OTC molecules through surface-mediated reactions. Furthermore, the 7-SFO/CN composite exhibits exceptional operational stability and applicability, offering a transformative approach for scalable photocatalytic water treatment systems. This work provides an effective strategy for designing efficient and recoverable photocatalysts for environmental remediation. Full article

The sustainable restoration of river and lake ecosystems requires advanced wastewater treatment technologies to control nitrogen pollution, a key driver of aquatic degradation. This study explores the physiological responses of anammox granular sludge (AnGS) to varying nitrogen loading rates (NLRs), offering insights into microbial stability under environmental stress. AnGS samples with different particle sizes (<1.0 mm, 1–2 mm, >2 mm) were subjected to NLRs ranging from 0.9 to 3.6 gN/L/d. As the NLR increased, the NO₂⁻-N/NH₄⁺-N consumption ratio rose from 1.0 to 1.2, and the most active particle size shifted to 1–2 mm. Hydroxyapatite (HAP) crystals formed at higher NLRs, enhancing the settling and activity of 1–2 mm AnGS but inhibiting larger granules (>2 mm). Microbial analysis revealed that Candidatus Brocadia dominated at high NLRs (10.5%), outperforming Candidatus Kuenenia (2.47%). The enrichment of these key genera across granules indicates adaptive microbial migration under loading stress. These findings provide critical operational strategies for sustaining AnGS performance through particle size regulation, contributing to nitrogen control solutions vital for river and lake restoration efforts. Full article

In this paper, we investigated fractal cluster structures of colloidal particles in tin dioxide films obtained from lyophilic film-forming systems SnCl₄/EtOH/NH₄OH with different pH levels. It was revealed that at the ratio Sn > Cl₂ > O₂, N₂ = 0, and pH = 1.42, the growth of cross-shaped and flower-shaped structures of various sizes from several μm to tens of μm is observed. At the ratio Cl₂ > Sn > O₂ > N₂ and pH = 1.44, triangular and hexagonal structures are observed, the sizes of which are on the order of several tens of micrometers. The growth of hexagonal structures is probably affected by the presence of nitrogen in the film, according to the elemental analysis data. At the ratio Sn > Cl₂ > O₂ > N₂ and solution pH of 1.49, the growth of hexagonal and cross-shaped structures is observed, whereas flower-shaped structures are not observed. Hierarchical flower-like and cross-shaped structures are fractal. The shape of microstructures is directly related to the shape of the elementary cells of SnO₂ and NH₄Cl. A direct dependence of the formation of hierarchical structures on the volume of ammonium hydroxide additive was found. This allows for controlling the shape and size of the synthesized structures when changing the ratio of the initial precursors and influencing the final physicochemical characteristics of the obtained samples. Full article

This study uses a new type of nitrogen-containing nickel-based flux-cored welding wire to study the microstructure and tensile properties of the deposited metal at 600 –700 °C. The results indicate that the precipitation phases of deposited metal mainly include the M (C, N) phase, Laves phase, and γ′ phase. After solution and aging treatment, the Laves phase remelts into the substrate. Nano-sized M (C, N) phase particles precipitate inside the grains, while the M₂₃C₆ phase forms at the grain boundaries. When stretched at 600 °C, the main deformation mechanism of the as-welded specimen is the cutting of precipitated phases by a/2<110> unit dislocations. The ultimate tensile strength of the heat-treated sample is much higher than that of the as-welded sample, but the ductility is reduced. The deformation mechanism involves not only the a/2<110>matrix dislocation cutting precipitation phase, but also two a/6<121>incomplete dislocation cutting precipitation phases together to form stacked dislocations. When stretched at 700 °C, dislocation loops appeared in the SA sample, indicating that the dislocation bypass mechanism had been activated. The tensile deformation mechanism of the deposited metal achieved a transition from dislocation cutting precipitated phases to dislocation bypassing precipitated phases. Full article

The densities of carbon, nitrogen, and phosphorus (C-N-P) reflect the adaptation and response of desert plants to hyper-arid environments. However, the allocation strategies for biomass and C-N-P densities among various plant life forms remain poorly understood. This study involved the collection of samples representing both aboveground and belowground biomass (to depths of 200 cm) from three desert plant species—both herbaceous and shrubby—and evaluating their C-N-P densities. The investigation focused on the distribution strategies and drivers influencing total C-N-P densities within the plant–soil system. The results indicated that the biomass of the shrub Tamarix ramosissima (8.88 ± 1.22 kg m⁻²) was significantly greater than that of the herbaceous plants Alhagi sparsifolia (0.96 ± 0.15 kg m⁻²) and Karelinia caspia (0.72 ± 0.09 kg m⁻²). The total C density among the three species was observed as follows: T. ramosissima (9.26 ± 0.99 kg m⁻²) > A. sparsifolia (6.21 ± 0.85 kg m⁻²) > K. caspia (6.18 ± 1.12 kg m⁻²). Notably, no significant differences were detected in the total N and P densities across the species. Additionally, for A. sparsifolia and K. caspia, the roots exhibited greater biomass and C-N-P densities. Further analysis revealed that soil pools accounted for 56.34–95.10% of total C density, 90.39–98.63% of total N density, and 99.86–99.97% of total P density in the plant–soil system. The order of total C-N-P densities was established as C > P > N, decoupling total P density from other environmental factors. Total C and N densities in the three plant species were predominantly influenced by soil physicochemical properties, with biotic factors and microbial biomass playing secondary roles. This study improves the understanding of C-N-P densities strategies of dominant vegetation for restoration and sustainable management in hyper-arid deserts. Full article

Porous materials are used in many important applications, such as separation technologies, catalysis, and chromatography. They may be obtained from various monomers via diverse polymerization techniques and a wide range of synthesis parameters. The study is devoted to the synthesis and characterization of crosslinked porous polymeric spheres containing pyrrolidone subunits. To achieve this goal, two methods were applied: direct synthesis from N-vinyl-2-pyrrolidone (NVP) with ethylene glycol dimethacrylate (EGDMA) and via a modification reaction of porous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) with pyrrolidone (P). The polymerization was carried out with the use of different molar ratios of the monomers. In order to obtain highly porous materials, pore-forming diluents (toluene, dodecane, and dodecan-1-ol) were used. The synthesized copolymers were characterized using size distribution analysis, ATR-FTIR spectroscopy, scanning electron microscopy, thermogravimetry, and inverse gas chromatography. Determined by the nitrogen adsorption/desorption method, the specific surface area was in the range of 55–468 m²/g. The good thermal properties of the poly(VP-co-EGDMA) copolymers allowed them to be applied as the stationary phase in gas chromatography. Full article

This study investigated the influence of CO₂ levels (20–40%: M20, M30, and M40) in high-oxygen modified atmosphere packaging (Hi-O₂ MAP) on microbial communities and quality attributes of chilled goat meat stored at 4 °C for 12 days. Alpha diversity indices (Chao1, ACE, Simpson, and Shannon) revealed a significant decline in microbial diversity over time, with storage duration exerting a greater impact than packaging conditions. Nonetheless, MAP played a crucial role in shaping microbial profiles, with air packaging (AP) showing the most distinct community, while M40 differed notably from M20 and M30, particularly by day 12, as shown by beta diversity analysis using principal coordinates analysis (PCoA). Proteobacteria and Firmicutes dominated microbial composition, with Pseudomonas and Brochothrix linked to spoilage in AP, while MAP, especially M40, favored the growth of Lactococcus, Acinetobacter, and Vagococcus, enhancing microbial stability. Despite pathogen levels remaining within safe limits, AP exceeded the spoilage threshold (TVC > 7.00 log colony-forming unit (CFU)/g), whereas all MAPs extended shelf life, with M40 most effectively suppressing microbial growth (p < 0.05). Interestingly, metagenomic functional profiling revealed that elevated CO₂ levels (>30%) altered metabolic pathways, shifting spoilage mechanisms from protein degradation in AP to carbohydrate metabolism in MAP, potentially influencing odor and texture attributes. MAP, particularly M40, also reduced protein and lipid degradation and oxidation, as indicated by lower total volatile base nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARSs), and shear force, suggesting better prevention of increased meat hardness and the development of undesirable odors and flavors, although high CO₂ negatively affected redness. Overall, M40 provided the greatest microbial stability and shelf life extension, highlighting the potential of optimized CO₂ levels in Hi-O₂ MAP to preserve goat meat quality and regulate spoilage dynamics. Full article

In this study, nitrogen-doped TiO₂ heterojunction materials were successfully synthesized via a facile one-step solvothermal approach. A range of advanced characterization techniques were employed to thoroughly analyze the structural and compositional properties of the synthesized photocatalysts, and their application potential for tetracycline (TC) degradation under visible light was studied. The results indicated that N-doped TiO₂ exhibited a well-defined hierarchical micro/nanostructure and formed an efficient anatase/rutile homogeneous heterojunction. The photocatalytic performance of N-TiO₂ for TC degradation under visible light was significantly enhanced, achieving a degradation efficiency of up to 87% after 60 min of irradiation. This improvement could be attributed to the synergistic effects of optimal nitrogen doping, heterojunction formation, and the hierarchical micro/nanostructure, which collectively reduced the bandgap energy and suppressed the recombination rate of photogenerated carriers. Furthermore, density functional theory (DFT) calculations were conducted to systematically explore the impacts of substitutional and interstitial nitrogen doping on the energy band structure of TiO₂. Full article

Understanding plant nitrogen (N) uptake strategies during vegetation recovery is essential for restoring and rehabilitating degraded ecosystems. However, there are few studies on plant N uptake strategies in karst regions. In this study, space-for-time substitution was used to investigate the dynamic changes in plant N uptake strategies during vegetation restoration. Grassland, shrub–grassland, shrubland, and woodland naturally recovering in karst ecosystems were chosen as the research objects. The dominant species at each stage were investigated. Dominant plant N uptake rates were measured using the ¹⁵N labeling technique, and plant root functional traits and available soil N were determined. Our results showed that soil inorganic N content and composition varied significantly with vegetation recovery. In early vegetation recovery stages, the soil inorganic N content was low and dominated by ammonium (NH₄⁺), while in the late stages, soil inorganic N content increased, and nitrate (NO₃⁻) became the dominant form. In early vegetation recovery stages, dominant plants preferentially absorbed NH₄⁺, contributing to 90.3%–98.5% of the total N uptake. With vegetation recovery, plants increased the NO₃⁻ uptake ratio from 1.48%–9.42% to 30.1%–42.6%. Additionally, the root functional traits of dominant plants changed significantly during vegetation recovery. With vegetation recovery, specific root lengths and specific root areas decreased, while root N content and plant N uptake rates increased. In summary, plants developed N uptake strategies coordinated with soil N supply by modifying root functional traits following vegetation recovery in karst regions. Full article

(1) Background: Mineral nutrient deficiencies are a major constraint on grapevine growth and productivity, yet the clear identification of deficiency symptoms and their physiological impacts remains challenging. (2) Methods: In this study, ‘Thompson Seedless’ grapevines were grown hydroponically under the controlled omission of ten essential nutrients (N, P, K, Ca, Mg, Fe, Mn, B, Zn, Cu) to assess their impact on growth, leaf morphology, chlorophyll content, photosynthesis, respiration, and tissue nutrient concentrations. (3) Results: Deficiencies in N, P, K, Mn, and B caused distinct leaf symptoms: nitrogen (N) deficiency led to pale leaves with bluish-green veins, phosphorus (P) deficiency caused yellowing in apical leaves followed by interveinal chlorosis, and potassium (K) deficiency induced pale yellow discoloration, curling, and rotting of the leaves. Manganese (Mn) and boron (B) deficiencies showed symptoms such as irregular leaf shapes and brittle, glossy leaves, respectively. These deficiencies resulted in reduced dry matter accumulation, decreased shoot length, and lower chlorophyll content. In contrast, iron (Fe) and copper (Cu) deficiencies had minimal effects, closely resembling those of the control conditions with only slight growth suppression. Notably, N, B, and Mg deficiencies led to significant reductions in Cu, Mg, B, and N levels, particularly evident through distinct symptoms in newly formed leaves. (4) Conclusions: Deficiencies in N, P, K, Mg, and B significantly affect grapevine growth, physiological processes, and nutritional quality. These findings emphasize the importance of maintaining balanced mineral nutrition for optimal grapevine health and productivity. Full article

Effectively utilizing aquatic plants to absorb nitrogen from water bodies and convert it into organic nitrogen via nitrogen assimilation enzyme activity reduces water nitrogen concentrations. This serves as a critical strategy for mitigating agricultural non-point source pollution in the Yellow River Basin However, emergent plants’ rate and mechanism of uptake of different forms of nitrogen remain unclear. This study determined the nitrogen uptake rates, nitrogen assimilation activities, root properties, and photosynthetic parameters of four emergent plants, Phragmites australis, Typha orientalis, Scirpus validus, and Lythrum salicaria, under five NH₄⁺/NO₃⁻ ratios (9:1, 7:3, 5:5, 3:7, and 1:9) using ¹⁵N hydroponic simulations. The results demonstrated that both the form of nitrogen and the plant species significantly influenced the nitrogen uptake rates of emergent plants. In water bodies with varying NH₄⁺/NO₃⁻ ratios, P. australis and T. orientalis exhibited significantly higher inorganic nitrogen uptake rates than S. validus and L. salicaria, increasing by 11.83–114.69% and 14.07–130.46%, respectively. When the ratio of NH₄⁺/NO₃⁻ in the water body was 9:1, the uptake rate of inorganic nitrogen by P. australis reached its peak, which was 729.20 μg·N·g⁻¹·h⁻¹ DW (Dry Weight). When the ratio of NH₄⁺/NO₃⁻ was 5:5, the uptake rate of T. orientalis was the highest, reaching 763.71 μg·N·g⁻¹·h⁻¹ DW. The plants’ preferences for different forms of nitrogen exhibited significant environmental plasticity. At an NH₄⁺/NO₃⁻ ratio of 5:5, P. australis and T. orientalis preferred NO₃⁻-N, whereas S. validus and L. salicaria favored NH₄⁺-N. The uptake rate of NH₄⁺-N by the four plants was significantly positively correlated with glutamine synthetase and glutamate synthase activities, while the uptake rate of NO₃⁻-N was significantly positively correlated with NR activity. These findings indicate that the nitrogen uptake and assimilation processes of these four plant species involve synergistic mechanisms of environmental adaptation and physiological regulation, enabling more effective utilization of different nitrogen forms in water. Additionally, the uptake rate of NH₄⁺-N by P. australis and T. orientalis was significantly positively correlated with glutamate dehydrogenase (GDH), suggesting that they are better adapted to eutrophication via the GDH pathway. The specific root surface area plays a crucial role in regulating the nitrogen uptake rates of plants. The amount of nitrogen uptake exerted the greatest total impact on the nitrogen uptake rate, followed by root traits and nitrogen assimilation enzymes. Therefore, there were significant interspecific differences in the uptake rates of and physiological response mechanisms of emergent plants to various nitrogen forms. It is recommended to prioritize the use of highly adaptable emergent plants such as P. australis and T. orientalis in the Yellow River irrigation area. Full article

In this study, a novel silver(I) complex [Ag(HL¹)₂]NO₃ (AgHL¹) with coumarin derivative (3E)-3-(1-{[(pyridin-2-yl)methyl]amino}ethylidene)-3,4-dihydro-2H-benzopyran-2,4-dione (HL¹) was prepared. The compounds HL¹ and AgHL¹ were characterized by IR and NMR spectroscopy, elemental analysis, and single crystal X-ray structural analysis. Specifically, the single crystal X-ray analysis determined the structures of both compounds HL¹ and AgHL¹ in their solid state, while NMR spectroscopy was used for structural determination in a solution. The HL¹ proved to be a monodentate ligand and is coordinated to the Ag(I) atom through a nitrogen atom from the 2-picolylamine fragment. In the complex AgHL¹, two molecules of neutral HL¹ are coordinated forming a nearly linear N-Ag-N arrangement. An uncoordinated nitrate anion balances the positive charge of the complex cation. NMR spectroscopy also confirmed the stability of AgHL¹ in DMSO-d₆ for 3 days. In vitro cytotoxicity of HL¹ and AgHL¹ was performed over two cancerous cell lines A549 and HT-29 and their selectivity was verified on a healthy CCD-18Co cell line. AgHL¹ exhibited low anticancer nonselective activity while the ligand was inactive. Also, the complex shows better antimicrobial activity than the positive controls on the Pseudomonas aeruginosa standard and clinical strain as well as on the tested molds. Full article

The content of bioavailable forms of phosphorus (P) and potassium (K) in soil is essential for the proper functioning of agroecosystems. This study aimed to determine the effects of pig slurry (PS) and NPK mineral fertilizers on soil phosphorus (P) and potassium (K) fractions, the relationship between these fractions and basic soil agrochemical properties, and crop yield. The research material was collected from a long-term experiment established in 1955 in Prague-Ruzyně, Czechia. The effect of two constant factors was analyzed: manure application (control, PS) and different doses of NPK fertilizers (N₀P₀K₀, N₁P₁K₁, N₃P₂K₂, and N₄P₂K₂). A significant effect of fertilization on basic soil properties was demonstrated, including total soil carbon and nitrogen. PS and NPK fertilization also significantly affected the content of water-soluble and moderate labile fractions of P and K. These fractions were positively correlated with plant-available P and K (Mehlich 3). The best fertilization option, which resulted in the greatest increase in yield, was the use of PS and mineral fertilizers at the N₃P₂K₂ level. Increasing the nitrogen dose to the level of N₄ resulted in a decrease in the content of bioavailable forms of P and K in topsoil despite the application of PS. Full article

This study aimed to better understand the impacts of various nitrogen (N) forms on blueberry growth and development, as well as to increase blueberry (Vaccinium spp.) N utilization efficiency. We selected the blueberry cultivar ‘Anna’ as the experimental material, and four N treatments were applied throughout the key vegetative growth stage: N deficiency (CK), ammonium-N (T1), nitrate-N (T2), and amide-N (T3). The growth parameters, physiology indexes, and ultrastructure changes in blueberry seedlings were explored. At the same time, the Pearson correlation model was used to analyze the correlation among each physiology index. The results showed that blueberry plants grew better under T1 and T3 treatments, with increased biomass, N content, chlorophyll content, and photosynthetic efficiency. Under T1 treatment, the leaves had lower O₂^˙− generation rate and MDA concentration, but higher superoxide dismutase (SOD), glutamate synthetase (GOGAT), and glutamine synthetase (GS) activity. Compared to T1 treatment, T2 treatment dramatically enhanced peroxidase (POD) activity, glucose content, and free amino acid content, particularly Arg content. Furthermore, N deficit treatment inhibited plant growth while increasing free radicals, POD, catalase (CAT), and glutamate dehydrogenase (GDH) activities, as well as the content of antioxidant compounds. Correlation and principal component analysis showed that photosynthetic properties, chlorophyll content, antioxidant system, amino acid levels, and N metabolizing enzyme activity were significantly affected by different N forms. This study can serve as a scientific foundation for optimal N regulation and management in blueberries. Full article