Search Results (8,408)

Acetaminophen, more commonly known as paracetamol (APAP), is one of the most widely used analgesics and antipyretic drugs worldwide. Its presence in the environment poses a risk to the organisms it comes into contact with, which is why it has been classified as an emerging contaminant. Given its adverse effects and continuous discharge into water bodies, it is necessary to study efficient, environmentally sustainable processes for its complete removal. Denitrification is a biological process that has been studied for the biodegradation of recalcitrant compounds and certain pharmaceuticals such as 17β-estradiol and ampicillin, transforming them into harmless products such as N₂ and HCO₃⁻. In the present study, the biodegradation of 6 mg L⁻¹ of APAP-C was evaluated through a denitrifying process. Batch experiments were conducted, achieving acetaminophen (APAP) removal efficiencies (E_APAP-C) of 83.3 ± 0.86% and nitrate removal efficiencies (E_N-NO3⁻) of 100%. The substrates were predominantly converted into HCO₃⁻ and N₂, with yields greater than 0.9, while intermediates such as NO₂⁻ were observed only transiently during the reaction. At the end of the experimental period, no secondary metabolites were detected, indicating that intermediates did not accumulate to quantifiable levels. Full article

Herein we reported on a one-pot nitro reduction/nucleophilic aromatic substitution on 1-(2-fluoro-5-nitrophenyl)ethan-1-one using a mixture of acetic acid and iron powder in ethanol. The resultant target compound, a nitrated N bis-acetophenone, has many reactive handles; as such, it is a novel intermediate that can be deployed for the syntheses of a vast array of compounds not reported before. This compound is fully characterized using ¹H and ¹³C NMR spectroscopy, and HRMS. Full article

Degraded groundwater quality, characterized by elevated salinity and nitrate concentrations, poses significant public health concerns, particularly for vulnerable populations such as children. High content of nitrate in drinking water may lead to non-carcinogenic health risks, highlighting the urgent need for sustainable groundwater management strategies to protect both human health and environmental integrity. This study assesses the suitability of groundwater resources in the Regueb Basin for irrigation and drinking purposes, with particular attention paid to nitrate contamination. The Irrigation Water Quality Index (IWQI) indicates considerable spatial variability in groundwater quality, with values varying between 15.86 and 89.55 and a median of 41.69, reflecting differing levels of suitability for irrigation across the basin. Similarly, the Drinking Water Quality Index (DWQI) ranges from 149.16 to 982.42, with a median value of 445.71, suggesting significant concerns regarding groundwater suitability for drinking purposes. The health risk assessment (HHRA) based on the Nitrate Pollution Index (NPI) and the nitrate hazard quotient (HQ__nitrate) reveal substantial risks to human health. NPI values vary between 0.45 and 5.5, with a median of 1.65 indicating varying levels of nitrate pollution. The HQ__nitrate results show that all groundwater samples (100%) pose health risks for children (HQ > 1). For women, 75.61% of HQ values exceed the safe threshold, affecting approximately 80% of the study area, whereas for men, 48.48% of HQ values exceed 1, impacting about 36.67% of the area. Overall, these findings highlight the urgent need for effective groundwater management strategies to mitigate nitrate contamination and ensure the safe and sustainable use of the groundwater resources in the Regueb Basin. Full article

This research explored how dietary supplementation of calcium nitrate influences methane emissions, nitrogen excretion, ruminal fermentation parameters, and microbiota in Liuyang black goats. A total of twelve male goats from this breed were divided into two groups: one serving as a control group (CON), while the other received a treatment of 3% calcium nitrate (CAL). The research was conducted over a period of 40 days and comprised two separate trial phases. A 10-day adaptation period and a 5-day sampling period (days 11–15) for each stage. Results showed that incorporating calcium nitrate significantly reduced the emissions of methane (CH₄) (p < 0.05) and carbon dioxide (CO₂) (p < 0.05). Moreover, the use of calcium nitrate modified the trends in ruminal fermentation, resulting in an increase in pH (p < 0.05). Moreover, the ratio of acetate to propionate (A:P) was notably reduced in the CAL group (p < 0.05), indicating a shift toward enhanced production of propionate. At the microbial level, an increased presence of Bacteroidota and Prevotella was observed in the CAL group (p < 0.05). In contrast, the CON group exhibited elevated levels of Firmicutes and Methanobrevibacter (p < 0.05). This finding suggests that calcium nitrate plays a significant role in reducing methane emissions and also affects the fermentation processes in the rumen along with the microbiota of Liuyang black goats. Further research is needed to examine the long-term implications of calcium nitrate supplementation on the health and productivity of these goats. Full article

Over two years, a randomized complete block field trial tested deficit irrigation [I: 70% ETc; NI] and ammonium nitrate [N₀, N₆₀, N₁₂₀; 0, 60, 120 kg N ha⁻¹] application in two northern Greece winegrape vineyards of cv. ‘Xinomavro’ (XM) and cv. ‘Cabernet Sauvignon’ (CS). Leaf-blade δ¹⁵N was measured at berry set, bunch closure, veraison, and technological maturity; berry-juice (must) δ¹⁵N at technological maturity and dormant cane δ¹⁵N in winter were also determined. In the first year, δ¹⁵N was additionally measured in petioles, unripe berries, trunks, and roots, along with arbuscular mycorrhizal fungal (AMF) colonization of fine roots. Fertilization increased δ¹⁵N in leaf blades and canes, whereas berry-juice δ¹⁵N responded weakly and inconsistently. Irrigation marginally lowered cane δ¹⁵N; cane δ¹⁵N varied between years, and berry-juice δ¹⁵N showed the highest variability across treatments. At berry set, intravine discrimination was evident: young berries and leaf blades were enriched, while fine roots and woody tissues were depleted. Root δ¹⁵N responses differed between cultivars and depended on AMF colonization in XM. Leaf and cane δ¹⁵N were positively related to vine N status, yield, and pruning weight but negatively to agronomic N-use efficiency indices. These findings indicate that δ¹⁵N serves as an integrative proxy of N cycling processes and fertilizer-use efficiency in vineyards, with potential implications for the assessment and optimization of sustainable vineyard management practices in the context of climate change. Full article

The high-temperature corrosion behavior of A1, T22, and T91 steels was investigated in molten nitrate salts at 400, 500, and 600 °C during 100 h of exposure. The combined influence of temperature and chromium content on corrosion kinetics and oxide-scale stability was evaluated using open-circuit potential (OCP), linear polarization resistance (Rp), electrochemical impedance spectroscopy (EIS), scanning electron microscopy, X-ray diffraction, and cross-sectional elemental mapping. OCP measurements showed a progressive shift toward more negative potential with increasing temperature, indicating enhanced oxidation tendency. Electrochemical measurements revealed a systematic decrease in Rp and impedance magnitude as temperature increased, confirming accelerated corrosion kinetics and reduced interfacial resistance. EIS spectra exhibited two characteristic time constants associated with the outer corrosion products and the inner metal/oxide interface. Significant differences in scale growth were observed depending on alloy composition. At 600 °C, oxide thickness reached approximately 700–800 μm for A1, ~100 μm for T22, and ~10 μm for T91. Chromium-containing steels promoted the formation of a compact Cr-rich inner oxide layer that improved scale adhesion and suppressed the exfoliation phenomena observed in A1 steel. Overall, temperature controls corrosion kinetics, whereas chromium content governs oxide-scale compactness and long-term stability in molten nitrate environments. Full article

Characterizing surface runoff and the transport process of non-point source pollutants (NSPs) carried by this runoff is crucial for identifying key source areas, estimating pollution loads entering water bodies, and implementing pollution control, which is particularly important in regions dominated by smallholder farming in China. Currently, most of the commonly used NSP models originated from international countries and have shortcomings such as high data requirements, high generalization degrees, and requiring the calibration of numerous parameters in the application process. Therefore, a distributed non-point source pollution model based on the time-varying gain and stormwater runoff response was constructed, designed for application at the watershed scale. This study describes the construction of the model, introducing its principles and structure through three key modules: a rainfall–runoff module, a soil erosion module, and a pollutant migration and transformation module. The proposed model was used to simulate the rainfall–runoff, soil erosion, and nutrient migration and transformation processes at different spatiotemporal scales. Although it achieved the best performance at the monthly and annual scales, its simulation results at the daily and hourly scales still met the relevant requirements, with relative errors within 20% and Nash–Sutcliffe Efficiency (NSE) coefficients of approximately 0.7. The annual sediment delivery ratios for the Yangliu Small Watershed and the basin above the Ankang section in 2022 were determined to be 0.445 and 0.36, respectively. The pollutant processes corresponding to different runoff events in the Yangliu Small Watershed were simulated, and the average NSE for total nitrogen (TN), ammonia nitrogen (NH₃-N), nitrate nitrogen (NO₃-N), total phosphorus (TP), and soluble reactive phosphorus (SRP) were determined to be 0.69, 0.74, 0.79, 0.71, and 0.71, respectively. For the basin above the Ankang section, the NSE coefficients for the simulation of NH₃-N and TP pollutant processes were 0.78 and 0.83, respectively. The model demonstrated robust applicability across various spatial (ranging from small to large watersheds) and temporal (hourly−daily−monthly−annual) scales, and exhibited stability across different basins in a semi-humid region of China. The model is characterized by a parsimonious parameter set, ease of calibration, and strong spatiotemporal versatility, thus providing an efficient and reliable tool for non-point source pollution simulation. Full article

To address ammonium nitrogen (NH₄⁺-N) and nitrite accumulation in intensive marine shrimp aquaculture, a marine recirculating aquaculture system (RAS) for Penaeus vannamei centered on a moving bed biofilm reactor (MBBR) was constructed to investigate the microbial basis of nitrogen removal. The results showed that the MBBR contributed most to NH₄⁺-N removal, demonstrating favorable nitrification potential under marine conditions (0.513 mg·L⁻¹·h⁻¹). The biofilm carrier formed a complete attached layer and developed a mature biofilm structure. Microbial community analysis revealed clear differentiation between the biofilm and sediment. The biofilm community was dominated by norank_f__Caldilineaceae (9.89%). Linear discriminant analysis effect size identified the nitrifying genus Nitrospira to be significantly enriched on the biofilm side (α = 0.05, linear discriminant analysis > 2.0). In addition, PICRUSt2-based functional prediction suggested a higher potential in biofilm than in sediment for ammonia oxidation and downstream nitrogen transformation, involving ammonia monooxygenase (EC:1.14.99.39), hydroxylamine dehydrogenase (EC:1.7.2.6), nitrate reductase (EC:1.7.99.4), and nitrite reductase (EC:1.7.2.1). Thus, this study provides a microbial basis and process strategy for P. vannamei RAS. Full article

The transition from High-Pressure Sodium (HPS) to energy-efficient Light-Emitting Diode (LED) supplemental lighting alters the plant thermal environment in controlled environment agriculture (CEA). This study evaluated how three practical supplemental lighting regimes, HPS, LED, and LED supplemented with infrared radiation (LED + IR), influence the physiology, growth, and phytochemical profile of Swiss chard (Beta vulgaris L.). We assessed biomass production, photosynthetic performance, oxidative stress markers (TBARS), and the concentration of primary and secondary metabolites. The LED treatment was superior for biomass production, yielding significant fresh mass while maintaining the lowest leaf nitrate content. Conversely, the addition of IR significantly increased leaf temperature, which suppressed growth but acted as a potent “bio-stress” agent, significantly increasing the total phenolic index. This biofortification, however, significantly decreased photosynthetic pigments (chlorophylls and carotenoids), increased lipid peroxidation (TBARS), and led to the highest accumulation of undesirable nitrates. Our findings reveal a clear growth-defense trade-off, demonstrating that while LED lighting is optimal for maximizing yield and food safety, the targeted application of IR radiation is an effective strategy for enhancing the nutraceutical value of leafy greens, requiring careful management to mitigate negative impacts on growth and quality. Full article

Root-zone nitrogen fertilization (RZF) can increase crop N uptake and yield, yet the underlying rhizosphere N-cycling functional mechanisms remain insufficiently resolved. In a field experiment with winter oilseed rape (Brassica napus L.), RZF was compared with conventional fertilization (CF) under the same N input rates, alongside a zero-N control (N0). Compared with CF, RZF significantly increased seed yield (by 0.44 t ha⁻¹) and aboveground N uptake (by 20.45 kg ha⁻¹), while simultaneously enriching rhizosphere mineral N pools (NH₄⁺–N and NO₃⁻–N by 54.50% and 56.02%, respectively). Shotgun metagenomics revealed that RZF reprogrammed rhizosphere N-cycling functional potential, characterized by enhanced nitrogen fixation, reduced nitrification and denitrification, and a tendency toward increased assimilatory nitrate reduction. These module-level shifts were supported by concordant changes in key functional genes, indicating greater genetic potential for N retention and assimilation (nifD, glnA, gltB, nasA, napB, nrfA) and reduced potential for nitrification- and denitrification-driven N losses (amoB/C, narI, nirK, norB). Taxonomic composition analysis showed enrichment of Bradyrhizobium and suppression of key nitrifier taxa (Nitrosospira and a Nitrososphaeraceae-affiliated taxon) under RZF. Rhizosphere pH exhibited the strongest Mantel correlation with multiple N-cycling modules, and rhizosphere available N (AN; sum of NH₄⁺–N and NO₃⁻–N) was positively associated with plant N traits and yield. Structural equation modeling supported a pathway in which a functional balance index (retention/assimilation vs. loss/oxidation) increased AN (0.22), and AN strongly promoted yield (0.90). Collectively, these results elucidate a rhizosphere-centered mechanism whereby localized N placement strengthens soil–plant N coupling and enhances crop productivity through reprogramming microbial N-cycling functional potentials, positioning rhizosphere N processes as a key mechanistic bridge for microbiome-informed optimization of root-zone fertilization. Full article

This paper describes the synthesis and characterisation of the calix semitube 5. The calix[4]semitube consists of two calix[4]arenes connected through their lower rim from two phenol groups in distal positions. One calix[4]arene is unsubstituted on its upper rim, while the upper rim of the other calix[4]arene has two nitro groups in the 1,3- position and two tert-butyl groups in the remaining ones. The synthesis procedure yielded an amorphous structure, which did not provide a single crystal. The final compound was comprehensively characterised by infrared spectroscopy, mass spectrometry, and ¹H and ¹³C NMR spectroscopy. The results of the ¹H NMR spectroscopy confirmed that the calix[4]arene units adopted a cone conformation. This was confirmed by COSY and ¹H-¹³C HMBC. The results obtained confirm that the compound was successfully synthesised. The IUPAC name of 5 is 2,34-di-tert-butyl-39,49-dinitro-6,7,8,9,27,28,29,30-octahydro-15H,21H,36H,42H-4,32:11,25-bis(methano [1,3]benzenomethano)-16,20:37,41-di(metheno)tetrabenzo[g,g1,p,x][1,6,18,23] tetraoxacyclotetratriacontine-43,46,54,60-tetraol. Full article

Urban coastal wetlands along the Peruvian Pacific coast are increasingly affected by urban expansion, pollution, and hydrological alterations, compromising their ecological integrity. In this context, the spatiotemporal variation of the aquatic macrophyte community and its relationship with limnological conditions and drivers of change were evaluated in the Santa Rosa wetland (Chancay, Lima). The objective is to evaluate the spatiotemporal variation of the aquatic macrophyte community in the Santa Rosa wetland and analyze its relationship with physicochemical limnological variables and drivers of change. Sampling was conducted during two contrasting hydrological seasons in 2022: T1 (low-water season) and T2 (high-water season), at six sampling points (P1–P6). Physicochemical variables (water depth, temperature, pH, conductivity, total dissolved solids—TDS, total suspended solids—TSS, dissolved oxygen—DO, turbidity, nitrate—NO₃⁻, ammonium—NH₄⁺, phosphate—PO₄³⁻, and dissolved organic matter—DOM) were measured, and the relative abundance of aquatic macrophytes was evaluated. Drivers of change were identified through direct observation and a structured matrix, with phosphate a PCoA performed to summarize spatiotemporal trends. Data were analyzed using Principal Component Analysis (PCA), Co-inertia analysis, and Multi-Response Permutation Procedures (MRPP). Significant spatiotemporal variation was observed in physicochemical parameters (p < 0.05), with moderate covariation between the two matrices (RV = 0.47). A total of ten aquatic macrophyte species were recorded, with higher abundance of Pontederia crassipes and Pistia stratiotes in T1, and Hydrocotyle ranunculoides and Bacopa monnieri in T2. The most relevant drivers of change were solid waste, livestock grazing, organic contamination, and urban expansion. Spatial heterogeneity was observed in the drivers of change affecting the Santa Rosa wetland, forming a mosaic of areas with different impact profiles. Despite multiple anthropogenic pressures, the Santa Rosa wetland maintains a limnological structure and a functionally coupled macrophyte community, suggesting that essential ecological processes are maintained within the temporal scope of this study. The observed covariation between physicochemical conditions and vegetation confirms the persistence of essential ecological processes, even within an altered urban context. This study demonstrates that integrating biotic components, limnological variables, and drivers of change is fundamental to understanding and monitoring the ecological dynamics of urban wetlands along the Peruvian coast. Full article

Aquaculture wastewater (AWW) contains elevated concentrations of nitrogen, phosphorus, and salts, in addition to many micropollutants that may cause environmental pollution if discharged untreated. This study evaluated the potential of the halophilic microalga Dunaliella salina for simultaneous phycoremediation of AWW and production of biodiesel-oriented biomass. Microalgal growth and biochemical composition were compared between AWW and synthetic f/2 medium under controlled laboratory conditions. Results showed that AWW supported efficient microalgal growth, showing a biomass yield of 1.32 g L⁻¹ with a productivity of 0.09 g L⁻¹ d⁻¹, representing 40.88% and 18.42%, respectively, over that obtained in f/2 medium. Cultivation in wastewater also enhanced the volumetric productivity of lipids, proteins, and carbohydrates by 26.20%, 12.46%, and 26.38%, respectively. Significant nutrient removal from AWW was achieved, with high reduction efficiencies for nitrate, nitrite, ammonium, phosphate, and sulfate within the range 76.80–94.10%, along with a decrease in salinity by 29.70%. The lipid fraction was dominated by fatty acid methyl esters suitable for biodiesel production, representing 94.10% of the total lipids. Biodiesel properties met the international fuel standards and were even improved when the microalga was cultivated in AWW. These findings demonstrate that AWW can serve as an effective culture medium for halophilic microalgae, enabling simultaneous wastewater treatment and sustainable biofuel feedstock production. Full article

This study evaluates the performance of Ni-La₂O₃/Beta catalysts for the dry reforming of methane, focusing on the effects of nickel loading, catalyst pretreatment, reaction temperature, and gas composition and flow rate. Catalysts with nickel contents ranging from 3 to 20 percent by weight were prepared via wet impregnation and characterized by gas adsorption, X-ray diffraction, temperature-programmed reduction with hydrogen, thermogravimetric analysis, and transmission electron microscopy. The results indicate that nickel gradually incorporates into the zeolitic support, preferentially occupying the most stable sites. Direct reduction of the impregnated catalyst precursors—omitting the calcination step—yielded materials with slightly higher methane conversion (ca. 3.5%) and enhanced stability. This improved performance is attributed to the reduction occurring during the thermal decomposition of supported nickel nitrate, which promotes finer nickel dispersion and stronger interaction with the La₂O₃-modified Beta zeolite. Full article

This study presents a comparative evaluation of four drying methods for carrot, red beet, and pumpkin pomace to produce natural functional food ingredients. The work addresses the valorization of 35–45% vegetable processing waste—a rich source of bioactive compounds—aligning with circular bioeconomy principles and Kazakhstan’s goals for deep processing of agricultural raw materials. The compared methods were convective drying (CD), ultrasound pretreatment + convective drying (US + CD), vacuum-microwave drying (VMD), and ultrasound pretreatment + vacuum-microwave drying (US + VMD). Drying kinetics, water activity, physicochemical and functional properties of powders, retention of bioactive compounds, color characteristics, thermal stability, and sensory attributes were assessed. Kinetics were fitted using Midilli et al., Page, and Weibull models. US + VMD provided the highest drying acceleration (6–11 times faster than CD), reaching final moisture of 5.1–5.9%, water activity a_w 0.27–0.31 in 80–170 min, and bioactive compound retention of 90–95% (carotenoids 92–95%, betalains 90–94%). It also delivered superior flowability (Carr’s index 22.5–30.4%), dispersibility (80–88% in 30 s), and thermal stability (75–85% at 200 °C). Acceleration varied by raw material: maximum for beet (up to 11×) due to soluble sugars and nitrates, minimum for pumpkin (5.5–8×) due to dietary fibers and pectins, and intermediate for carrot (6–9×) influenced by carotenoids’ dielectric properties. The results highlight US + VMD’s strong potential for producing functional powders to replace synthetic additives in food systems. Effective method selection and parameter optimization require consideration of raw material type and rheological characteristics. Full article