Search Results (1,981)

With accelerating urbanization, rivers have been severely polluted, resulting in widespread black and odorous waterways. The coagulation–sedimentation and contact oxidation bypass treatment process is characterized by low operational cost and simple operation and management. In this study, a coagulation–sedimentation–contact oxidation biofilter process was developed to treat heavily polluted malodorous blackwater. Among the tested biofilm carriers, rigid aramid fiber exhibited the fastest biofilm formation and the best pollutant removal performance. Based on a comprehensive evaluation of effluent quality and treatment capacity, the optimal operating conditions of the proposed process were identified as a PAC dosage of 50 mg/L, an air-to-water ratio of 7:1, and a hydraulic retention time (HRT) of 2 h. Under these conditions, the effluent concentrations of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), and suspended solids (SSs) were consistently maintained below 30, 5, and 5 mg/L, respectively. Moreover, the optimized system demonstrated strong resistance to shock loading, maintaining stable operation at influent COD and SS concentrations of approximately 150 mg/L and 40 mg/L, respectively, while complying with the Class A Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants. This study provides an efficient treatment strategy for malodorous blackwater remediation. Full article

Root anatomy serves as a critical indicator for understanding wetland plant adaptation strategies to environmental changes. Since water depth determines root oxygen demand while nitrogen addition regulates nutrient acquisition, the two factors exert significant and interactive effects on root anatomical structure. In this study, we established a controlled experiment employing three water depth treatments (W1: −10 cm; W2: 10 cm; W3: 30 cm), two nitrogen (N) forms (ammonium-N, nitrate-N), and four N addition levels (N0: 0 mg/L; N1: 40 mg/L; N2: 80 mg/L; N3: 160 mg/L). This design enabled us to analyze the effects of water–nitrogen interactions on the anatomical structure of reed roots to reveal wetland plants’ adaptive strategies to water-nitrogen fluctuations. The results indicate that (1) under nitrogen-free treatment, compared to the control group, the W1 treatment reduced the root aerenchyma proportion and the stele-to-root diameter ratio by 15.8% and 37.0%, respectively. In contrast, exodermis thickness increased by 32.4%, while epidermis thickness decreased by 33.7%. Under the W3 treatment, the aerenchyma proportion increased by 21.0%, the stele-to-root diameter ratio decreased by 22.2%, and exodermis thickness increased by 35.3%. (2) Compared to the nitrogen-free treatment, nitrate addition increased the root aerenchyma proportion under W1, W2, and W3 by 18.8%, 6.9%, and 18.3%. The stele-to-root diameter ratio increased by 27.9% and 12.7% under W1 and W2, but decreased by 10.8% under W3. Exodermis thickness increased by 26.3% under W2, whereas it decreased by 10.8% under W3. Epidermis thickness increased by 36.1% and 22.2% under W1 and W3, while a decrease of 12.7% occurred under W2. (3) Compared to the nitrogen-free treatment, ammonium addition increased the root aerenchyma proportion under W1, W2, and W3 by 13.6%, 13.2%, and 10.0%. The stele-to-root diameter ratio increased by 28.1% under W1 but decreased by 10.4% under W3. Conversely, exodermis thickness decreased by 20.2% under W1 while increasing by 12.6% under W3. Epidermis thickness increased by 26.3% and 20.8% under the W1 and W3 treatments. In summary, the root anatomical structure of P. australis adaptively responds to variations in water depth, nitrogen forms, and nitrogen concentrations by modulating aerenchyma proportion, the stele-to-root diameter ratio, exodermis thickness, and epidermis thickness. Future research should strengthen the study of the relationship between root anatomical traits and plant functions, to more comprehensively explore the adaptation mechanisms of wetland plants to global environmental change. Full article

Tea plants (Camellia sinensis) uniquely hyperaccumulate fluoride (F) and concurrently exhibit a preference for ammonium nitrogen (NH₄⁺-N) over nitrate nitrogen (NO₃⁻-N). However, the mechanistic basis for co-existence of NH₄⁺-N preference and F hyperaccumulation in C. sinensis remains unexplored. Here, we investigated F accumulation and translocation with varying N supplies (0 mM and 2.854 mM N with NH₄⁺-N:NO₃⁻-N ratios of 3:1, 4:0 and 0:4) and F concentrations (0, 8 and 16 mg·L⁻¹ NaF) to reveal the mechanism driving NH₄⁺-N preference and F hyperaccumulation in C. sinensis. Results show that NH₄⁺-N supply enhanced H⁺ efflux, mobilizing aluminum (Al) to form mobile Al-F complexes for translocation to shoots, thereby alleviating F toxicity in roots. This process was facilitated by transporters including CsCLCd, CsCLCe, CsCLCf2 and CsFEX. In contrast, NO₃⁻-N promoted root sequestration of F as immobile calcium (Ca)-F complexes, exacerbating damage. Under NO₃⁻-N supply, CsCLCb primarily mediated NO₃⁻ transport, while CsCLCc, CsCLCe, CsCLCf1, CsCLCf2 and CsFEX were involved in F transport. In leaves, CsCLCd, CsCLCe, CsCLCf1, CsCLCf2, CsCLCg and CsFEX mediated vacuolar sequestration under both N conditions. These findings elucidate that NH₄⁺-N preference is mechanistically linked to F hyperaccumulation through an Al-assisted translocation pathway, which confers tolerance by exporting F from roots. Full article

Pasture-based ruminant systems link nitrogen (N) nutrition with ecosystem N cycling. Grazing ruminants convert fibrous forages into milk and meat but excrete 65 to 80% of ingested N, creating excreta hotspots that drive ammonia volatilization, nitrate leaching, and nitrous oxide (N₂O) emissions. This review synthesizes ecological and ruminant nutrition evidence on N flows, emphasizing microbial processes, biological N₂ fixation, plant diversity, and urine patch biogeochemistry, and evaluates strategies to improve N use efficiency (NUE). We examine rumen N metabolism in relation to microbial protein synthesis, urea recycling, and dietary factors including crude protein concentration, energy supply, forage composition, and plant secondary compounds that modulate protein degradability and microbial N capture, thereby influencing N partitioning among animal products, urine, and feces, as reflected in milk and blood urea N. We also examine how grazing patterns and excreta distribution, assessed with sensor technologies, modify N flows. Evidence indicates that integrated management combining dietary manipulation, forage diversity, targeted grazing, and decision tools can increase farm-gate NUE from 20–25% to over 30% while sustaining performance. Framing these processes within the global N cycle positions pasture-based ruminant systems as critical leverage points for aligning ruminant production with environmental and climate sustainability goals. Full article

Aiming at the problems of tree vigor decline and unstable fruit quality caused by soil impoverishment and easy nutrient loss in the Ziziphus jujuba Mill. ‘Huizao’ (Huizao) producing areas of southern Xinjiang, the application effect of bag-controlled slow-release fertilizer (BCSRF) in this region remains unclear. In this study, a field experiment was conducted with four fertilization concentration gradients, including CK (0 kg/ha), T1 (22 kg/ha), T2 (44 kg/ha), and T3 (66 kg/ha), to investigate the effects of BCSRF on soil nutrient dynamics and plant growth, as well as the fruit yield and quality of Huizao. The results showed that BCSRF could effectively maintain the supply levels of soil alkali-hydrolysable nitrogen, available phosphorus, and available potassium during key growth periods, among which the T3 treatment exhibited the most significant effect. This treatment not only significantly increased the yield per plant of Huizao by 39.34% compared with the control, but also markedly enhanced the contents of the endogenous substance, including soluble sugar and cyclic adenosine monophosphate. This study confirms that under the condition of sandy loam soil in southern Xinjiang, a single basal application of an appropriate amount of BCSRF can achieve continuous nutrient supply, simultaneously improve soil fertility and fruit quality, providing a theoretical basis and technical guidance for simplified and efficient fertilization in local jujube orchards. Full article

Maintaining water quality and fish well-being in newly established, small, unfiltered betta (Betta splendens) aquaria is a significant challenge. To improve betta fish breeding and welfare, this study set up four groups: the Sagittaria subulata (S.su) group, the Alternanthera reineckii (A.re) group, the Wolffia globosa (W.gl) group, and the plant-free (CG) group. We evaluated the effects of aquatic plants on water quality, fish behavior, and microbial community in newly established tanks over 25 days. The results demonstrated that both the dissolved oxygen (DO) and potential of hydrogen (pH) decreased with the experimental duration, while ammonia nitrogen (NH₃-N) increased over time in all groups. Compared to the CG group, all aquatic plants significantly reduced the NH₃-N accumulation. The S.su group exhibited the lowest mean NH₃-N concentration of only 0.14 mg·L⁻¹, which was considerably lower than that of the other groups (p < 0.05). The behavioral analysis revealed that, during the 25-day randomized monitoring period, bettas in the S.su group exhibited the lowest surface breathing, with an average of only 0.36 events per 5 min, which was significantly lower than that of the CG group (p < 0.05). Additionally, the S.su and W.gl groups demonstrated longer average swimming durations than the other groups, suggesting a potential trend toward improved welfare in betta fish. Aquatic plants shaped the microbial diversity and composition within the experimental aquatic system. The W.gl group had the highest microbial diversity, and the A.re and S.su groups enriched Verrucomicrobiota. These results demonstrate the preferential shaping of microbial communities by aquatic plants, suggesting a potential pathway for enhancing water quality. In conclusion, S. subulata demonstrates the greatest benefits under the experimental conditions, making it a more suitable choice for this experiment. Full article

This paper presents a numerical study on the deployment of Overfire Air (OFA) technology in coal-fired thermal power plants in Kazakhstan to reduce harmful emissions. The simulation utilized a digital model of the combustion chamber of the BKZ-75 boiler at Shakhtinsk thermal power plant, which utilizes high-ash Karaganda coal containing 35.10% ash. During the development of two-stage combustion technology, different methods of supplying extra air via OFA injectors were examined. Various positions within the combustion chamber were evaluated for their placement: at heights of h = 0.165 m; 0.75 m; 1.375 m; 2.25 m; 2.5 m; 8 m; 9.4 m; 10 m; 11 m; and 12 m. The baseline combustion mode (OFA = 0%) and several additional air injector settings were analyzed, including OFA levels of 5%, 10%, 15%, 18%, 20%, 25%, and 30% of the total air volume. Numerical simulations generated temperature distributions along with carbon monoxide (CO) and nitrogen (NO) concentration fields, both inside and outside the combustion chamber outlet. Research indicates that the most effective reduction in pollutant emissions happens when OFA injectors are positioned at 9.4 m and supply supplementary air at an OFA rate of 18%. Under these settings, the carbon monoxide concentration at the combustion chamber outlet decreases by approximately 36%, while nitrogen oxide levels drop by 25%, compared to the baseline condition (OFA = 0%). These insights can be utilized to upgrade boiler units, promoting cleaner fuel combustion in coal-fired thermal power plants. Full article

In facility tomato production, the excessive application ratio of ammonium nitrogen (NH₄⁺-N) often leads to root acidification and calcium-magnesium antagonism. Although amide nitrogen (urea-N) has better buffering properties, it needs to be hydrolyzed before utilization, resulting in a lag effect. Previous studies have mostly focused on a single nitrogen source or a fixed proportion, and there is still a lack of systematic evidence on the nitrogen supply effects of different nitrogen application combinations at different growth stages of tomatoes. Therefore, in this experiment, tomato cultivar ‘Jingfan 502’ was used. All treatments received the same total nitrogen concentration (15 mM), but the nitrogen was supplied as different combinations of ammonium nitrogen (AN) and amide nitrogen (UN). Six AN–UN ratio treatments were designed: CK (0% AN, 0% UN), T1 (100% AN, 0% UN), T2 (0% AN, 100% UN), T3 (25% AN, 75% UN), T4 (50% AN, 50% UN), and T5 (75% AN, 25% UN). T3 (25% NH₄⁺ + 75% urea) increased single-plant yield by 64.04% and 5.10%, and total N, P, K, and Mg accumulation by 29.0% and 20.7%, relative to T1 and T2. In addition, compared to T1 and T2, the nitrogen fertilizer uptake rate of the T3 treatment increased by 17.00% and 24.90%, respectively, and the electrical conductivity (EC) increased by 27.04% and 44.84%, respectively. Redundancy Analysis (RDA) showed that enzyme activities, total N and electrical conductivity were positively linked to microbial communities in T3 and T4, whereas communities in CK, T1, T2 and T5 correlated with nutrients and pH. Under controlled pot conditions, T3 optimizes the rhizosphere micro-environment, enhances microbial abundance and nutrient uptake, and provides a theoretical basis for precise N management in tomato. Full article

Functional properties of coastal halophytes are important for development of salt-tolerant cash crop cultures. The study of salt tolerance in coastal dune-building grass Leymus arenarius holds significant importance for its application in land reclamation, soil stabilization, and enhancing crop resilience to salinity stress. We used two accessions (LA1 and LA2) of L. arenarius to compare effects of salinity caused by NaCl and NaNO₃ on growth, ion accumulation and mineral nutrition in controlled conditions. L. arenarius plants exhibited high tolerance to sodium salts, with distinct effects on growth and development observed between chloride and nitrate treatments. While both salts negatively impacted root biomass, nitrate treatment (50–100 mmol L⁻¹) increased leaf number and biomass in LA2 plants, whereas chloride treatment decreased tiller and leaf sheath biomass. Despite individual variations, salinity treatments showed comparable effects on traits like tiller and leaf count, as well as leaf blade and sheath biomass. Salinity increased water content in leaf blades, sheaths, and roots, with LA2 plants showing the most pronounced effects. Chlorophyll a fluorescence measurements indicated a positive impact of NaNO₃ treatment on photosynthesis at intermediate salt concentrations, but a decrease at high salinity, particularly in LA2 plants. The accumulation capacity for Na⁺ in nitrate-treated plants reached 30 and 20 g kg⁻¹ in leaves and roots, respectively. In contrast, the accumulation capacity in chloride-treated plants was significantly lower, approximately 10 g kg⁻¹, in both leaves and roots. Both treatments increased nitrogen, phosphorus, and manganese concentrations in leaves and roots, with varying effects on calcium, magnesium, iron, zinc, and copper concentrations depending on the type of salt and tissue. These findings highlight the potential of L. arenarius for restoring saline and nitrogen-contaminated environments and position it as a valuable model for advancing research on salt tolerance mechanisms to improve cereal crop resilience. Full article

Improving nutrient use efficiency and minimizing environmental pollution from excessive fertilization require appropriate nutrient management supported by continuous monitoring of soil nutrient levels during crop growth. As only a few real-time sensors for the measurement of soil nutrients are available, this study evaluated the potential of electrical conductivity (EC) sensors, which reflect the ionic concentrations of the soil solution, for real-time estimation of plant-available nutrient levels. Nitrogen and potassium were sequentially supplied to achieve cumulative application rates of 25–300% of the nutrient uptake-based fertilization rate. The relationship between cumulative fertilization rate and accumulated sensor-based EC increase was described using linear, polynomial, and nonlinear saturation models. Sensor EC increased linearly from 25 to 125% of the nutrient uptake-based fertilization rate, while higher application rates were better explained by the nonlinear saturation equation. Sensor-based EC showed strong correlation with soil ammonium nitrogen (NH₄⁺-N), indicating that the sensor effectively reflected nutrient dynamics. In open-field pepper soil, fertigation-induced increases in sensor EC followed the patterns predicted by both the linear and nonlinear saturation models established in the laboratory. These results demonstrate that EC sensors can be used for real-time monitoring of soil nutrient levels and may contribute to efficient nutrient management in open-field cultivation. Full article

Feeding time is a critical but understudied factor influencing nutrient dynamics and overall productivity in aquaponic systems. This study examined the effects of two feeding schedules on growth performance of common carp (Cyprinus carpio L.), hydrochemical parameters, and the growth of lettuce (Lactuca sativa) cultivated in an integrated aquaponic system. Two 60-day trials were conducted over consecutive years under identical greenhouse conditions. Carp were fed either in the morning and early afternoon (T1: 08:00, 11:00, 14:00) or later in the day (T2: 11:00, 14:00, 17:00). Hydrochemical indicators, including dissolved oxygen, turbidity, ammonium ions (NH₄⁺), and nitrates (NO₃⁻), were continuously monitored through online measurement. Carp reared under T2 displayed significantly higher specific growth rate, final body mass, and improved feed conversion ratio (p < 0.05). The T2 variant also showed higher dissolved oxygen levels and lower turbidity compared to T1, indicating enhanced system stability. Although NH₄⁺ concentrations were higher and NO₃⁻ levels lower in T2, these differences did not compromise water quality due to efficient plant nutrient uptake. Lettuce grown under T2 exhibited greater stem and root development and higher biomass accumulation, suggesting improved nitrogen utilization linked to the NH₄⁺/NO₃⁻ ratio and enhanced root oxygenation. Overall, aligning feeding time with fish circadian rhythms improved fish performance, plant growth, and nutrient cycling efficiency. These findings demonstrate that feeding schedule is a key management factor capable of enhancing sustainability and productivity in aquaponic systems. Full article

Sustainable fertilization strategies are increasingly required to enhance crop performance while reducing dependence on synthetic inaputs. In this study, the effectiveness of sea-derived organic amendments, Posidonia oceanica compost and mussel shell powder, was evaluated in Salvia officinalis (sage) cultivation. A pot experiment was conducted in Istron Kalou Xoriou (Crete), using three nitrogen rates (0, 40 and 80 kg ha⁻¹) in combination with four rates of mussel shell powder (0, 50, 100 and 200 g/pot). A total of 9 treatments were set up, each replicated 3 times, resulting in 27 pots. Growth parameters (plant height, total and leaf fresh-dry weight), nitrogen content in plant tissues, nitrogen uptake, and nitrogen use efficiency (NUE) were assessed across three harvest periods. The results indicated that both P. oceanica compost and mussel shell amendments significantly improved soil properties and plant performance. The treatment receiving 200 g/pot of mussel shell powder combined with 80 kg ha⁻¹ fertilization (PH200) consistently produced the highest values for biomass (223.99–383.58 g/plant), nitrogen plant concentration (1.967–2.117%), and nitrogen uptake (1.762–3.248 g/plant). The application of mussel shells effectively increased soil pH, thereby enhancing nutrient availability and promoting nitrogen assimilation. Furthermore, NUE values showed a progressive increase with rising amendments rates. Overall, sea-derived organic amendments demonstrated strong potential as sustainable fertilization materials, contributing to sage productivity improvement while supporting circular management of coastal waste resources. Full article

The need for more sustainable agriculture less dependent on mineral fertilizers has intensified the interest in the reuse of agro-industrial by-products as alternative nutrient sources. This study investigates the agronomic potential of citrus sewage sludge (CSS), derived from citrus wastewater treatment, as a nitrogen (N) source for wheat cultivation. An experiment was conducted using two Mediterranean soils with contrasting physicochemical properties, comparing a non-fertilized control (CTR), inorganic N fertilization (NH₄NO₃) (CTR + N), and CSS; fertilizers were applied once at 30 mg of N per plant. Differences in soil organic carbon availability and C/N ratio, together with carbonate-related properties, influenced N dynamics in the soil–plant system. In the soil with higher oxidizable organic C and a more favorable C/N ratio (S1), CSS increased soil ammonium concentrations by about 70% compared with the control and by nearly 50% compared with the soil characterized by lower organic C availability (S2). In S2, the lower concentrations of both NH₄⁺ and NO₃⁻ indicate reduced microbial mineralization and nitrification, consistent with its lower availability of readily degradable organic carbon. Moreover, wheat grown with CSS exhibited a total biomass about 40% higher than that of the CTR. The Mineral Fertilizer Replacement Value (MFRV) reached 73% in S1 and 46% in S2, confirming the potential of CSS as a sustainable N source, particularly in soils where organic C availability supports microbial activity and N transformations. Future strategies should focus on improving CSS use through specific soil management practices. Full article

Invasive insects increasingly threaten ecosystems worldwide, with wetlands especially vulnerable to unpredictable climate. Phragmites australis is a dominant plant species in Louisiana’s Mississippi River Delta and a critically important component of the wetland ecosystem. However, the invasive scale insect, Nipponaclerda biwakoensis, has contributed to large-scale dieback of this foundation species, jeopardizing erosion control, water filtration, and wildlife habitat. Despite rapid regional spread, the fine-scale dispersal of N. biwakoensis within host plants remains poorly understood. We examined whether the crawler-stage of N. biwakoensis scales preferentially settled on the bottom or top sections of P. australis stems, and whether plant nutritional and/or defensive traits shaped this preference. In field surveys, scale densities varied along the length of P. australis stems, with gravid females occurring 3.5× more frequently at the stem base than at the top; parasitism rates were similarly elevated, reaching 12× higher at the base. To evaluate potential drivers of this pattern, we quantified carbon, nitrogen, water, and phenolic content in lower and upper stem tissues and conducted complementary laboratory assays to test crawler settlement preferences. Under controlled conditions, crawlers settled most densely on middle stem sections, with lower densities at the base and the fewest near the top. The basal sections also contained 50% less nitrogen and 47% lower phenolic concentrations compared to the upper stem. The divergence in crawler settlement patterns between field and controlled conditions likely reflects the influence of additional environmental factors present in the field—such as habitat structure, microclimate, and natural enemies—that are absent or minimized in laboratory conditions. By applying a trait-based approach to insect dispersal, we link plant functional traits to N. biwakoensis crawler settlement patterns, strengthening our understanding of of insect distribution and guiding predictions of long-term dispersal in N. biwakoensis. Full article

The effect of nitrogen (N) deposition on soil organic carbon (SOC) and the underlying mechanisms in grassland ecosystems remain a topic of debate. Moreover, previous research has primarily concentrated on interaction between carbon (C) and N cycles in response to N deposition, with less attention paid to how N-induced phosphorus (P) deficits impact SOC sequestration. To further investigate whether soil microbial stoichiometry influences SOC sequestration under N enrichment, we conducted a field experiment involving N and P additions. The soil properties, nutrients within plant leaves and microbial biomass, and the potential activity of eco-enzymes related to microbial nutrient acquisition were measured. Results showed that SOC did not significantly change with N addition, and SOC significantly increased with addition of N and P together, which suggested that the SOC was depleted with N addition. Soil available phosphorus and microbial biomass phosphorus (MBP) did not significantly decrease alongside N addition, which suggested that microbes alleviated P limitation. Microbial metabolic limitation analysis showed microbial P limitation was enhanced by N10 treatment. At the same time, microbial P limitation enhanced microbial C limitation. Consequently, microbes also required more C as an energy resource to invest in enzyme production. Microbial P and C limitations were both significantly negatively correlated with SOC. Results from SEM analysis also showed that the MBC:MBP ratio was significantly negatively correlated with SOC. These results support the idea that consumer-driven nutrient recycling shapes the dynamics of SOC. Therefore, nitrogen deposition-induced MBC:MBP imbalance may regulate SOC in alpine grassland ecosystems. Full article