Search Results (1,798)

This study uses high-frequency monitoring across a river–barrier lake–reservoir continuum in the upper Minjiang River, southwestern China, to quantify the spatiotemporal dynamics and drivers of aquatic CO₂ partial pressure (pCO₂) and to identify the dominant controls under contrasting lotic and lentic conditions. River reaches were CO₂-supersaturated throughout the year, with higher pCO₂ in the wet season (mean 521 ppm) than in the dry season (421 ppm), indicating persistent CO₂ evasion to the atmosphere. In contrast, the downstream canyon-type reservoir showed a pronounced seasonal reversal. During the wet season, surface-water pCO₂ averaged 395 ppm, about 24% lower than that of the river and below atmospheric levels (~419 ppm); more than 55% of observations were undersaturated, with minima as low as 141–185 ppm, indicating temporary CO₂-sink behavior. In the dry season, mean pCO₂ increased to 563 ppm, exceeding both riverine and atmospheric levels and returning the reservoir to a CO₂ source. The reservoir pCO₂ variability was governed by the interaction of hydrology and metabolism: rising water levels and longer residence times likely enhanced CO₂ accumulation from the decomposition of inundated organic matter, while warm temperatures, high light and monsoon-driven nutrient inputs promoted phytoplankton growth that removed dissolved CO₂ and elevated dissolved oxygen, producing temporary sink behavior. In the river, short residence time and strong turbulence limited in-stream biological regulation, and pCO₂ variability was mainly driven by catchment-scale carbon inputs along the elevation gradient. Overall, our results demonstrate that dam construction and impoundment can substantially modify carbon cycling in high-mountain rivers. Under specific conditions (warm water, sufficient nutrients, high algal biomass), lentic environments may strengthen photosynthetic CO₂ uptake and temporarily transform typical riverine CO₂ sources into sinks, with important implications for carbon-budget assessments and reservoir management in mountainous basins. Full article

Combined application of organic (M) and chemical fertilizer (C) is a significant measure to enhance soil fertility and ensure food security. In 2023 and 2024, we established six treatments: T1 (no fertilization), T2 (100% C), T3 (75% C + 25% M), T4 (50% C + 50% M), T5 (25% C +75% M), and T6 (100% M), with three replicates for each treatment. The total amount of nitrogen applied to the soil for T2–T6 was the same, and the organic fertilizer was compost sourced from cow dung. The aims of this study were to explore the effects of organic fertilizer combined with chemical fertilizer on soil fertility, and apparent nutrient balance, to investigate its possible economic benefits. We also analyzed the influence of the combined application of organic and chemical fertilizers on the degree of coupling and coordination (D) between soil fertility and economic benefits. The total phosphorus, total potassium, available phosphorus, available potassium, and organic matter in the soil all showed an increasing trend with an increase in the proportion of organic fertilizer applied. T2 reduced the soil pH by 7.41–8.94% compared with T1, while applying organic fertilizers (T3–T6) increased the soil pH by 0.72–8.62% compared with T2. T4 is conducive to the balance of income and expenditure of nitrogen, phosphorus, and potassium elements. The corn yield, net income, and input–output ratio all showed an initial increase followed by a decrease with an increase in the proportion of organic fertilizer applied, and their values all reached the maximum under T4. Based on the CRITIC-TOPSIS method and the coupling coordination degree model, it was determined that the fertilization strategy with the highest comprehensive score and D under the conditions of this experiment was 50% C +50% M (T4), which not only improved soil fertility but also achieved the highest economic benefit. The research results were of great significance for promoting sustainable agricultural development. Full article

Sandstone-hosted uranium deposits represent one of the most critical global uranium resources suitable for in situ recovery, with their formation closely associated with organic matter (OM). We conducted a systematic literature review to synthesize over 100 published studies sourced from authoritative databases (Elsevier, Google Scholar, Web of Science, Scopus, CNKI, etc.). This study systematically summarizes the types and geological characteristics of OM in sandstone reservoirs and thoroughly analyzes the geochemical mechanisms by which OM regulates the transport and precipitation of aqueous uranium. By integrating case studies of representative sandstone uranium deposits globally, three major OM-related metallogenic models are proposed with distinct core characteristics: the humic-dominated model is driven by the complexation and direct reduction of uranium by humic substances/coal-derived OM; the roll-front model relies on reactions between oxidized uranium-bearing fluids and scattered OM, as well as microbially generated sulfides at the migration front; and the seepage-related model is fueled by upward-migrating deep hydrocarbon fluids (petroleum, methane) that act as both uranium carriers and reductants. Furthermore, this review explores the spatial coupling relationships between OM distribution and uranium mineralization in typical geological settings, evaluates the guiding significance of OM for uranium exploration, and outlines key unresolved scientific issues. The findings refine the genetic theoretical framework of sandstone-hosted uranium deposits and provide important technical support and theoretical guidance for future uranium exploration deployment and resource potential evaluation. Full article

Metallic implants used in orthopedics, such as titanium alloys, possess excellent mechanical strength but suffer from corrosion and poor bio-integration, often necessitating revision surgeries. Bioactive coatings, particularly hydroxyapatite, can enhance implant osteoconductivity, but high-purity synthetic hydroxyapatite is costly. This study investigates the development and characterization of a low-cost, biocompatible coating using hydroxyapatite derived from an unconventional natural source dromedary bone applied onto a titanium substrate via plasma spraying. Hydroxyapatite powder was synthesized from dromedary femurs through a thermal treatment process at 1000 °C. The resulting powder was then deposited onto a sandblasted titanium dioxide substrate using an atmospheric plasma spray technique. The physicochemical, structural, and morphological properties of both the source powder and the final coating were comprehensively analyzed using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray Diffraction, and Fourier-Transform Infrared Spectroscopy. Characterization of the powder confirmed the successful synthesis of pure, crystalline hydroxyapatite, with Fourier-Transform Infrared Spectroscopy analysis verifying the complete removal of organic matter. The plasma-sprayed coating exhibited good adhesion and a homogenous, lamellar microstructure typical of thermal spray processes, with an average thickness of approximately 95 μm. X-ray Diffraction analysis of the coating revealed that while hydroxyapatite remained the primary phase, partial decomposition occurred during spraying, leading to the formation of secondary phases, including tricalcium phosphate and calcium oxide. Scanning Electron Microscopy imaging showed a porous surface composed of fully and partially melted particles, a feature potentially beneficial for bone integration. The findings demonstrate that dromedary bone is a viable and low-cost precursor for producing bioactive hydroxyapatite coatings for orthopedic implants. The plasma spray method successfully creates a well-adhered, porous coating, though process-induced phase changes must be considered for biomedical applications. Full article

Mangrove sediments in the South China Sea, particularly in the Hainan Island region, play a crucial role in regulating heavy metal migration and sequestration. However, the impact of converting mangrove areas to fish and shrimp culture ponds on heavy metal pollution in the Bamen Bay Mangrove Reserve is unclear. This study evaluates the pollution levels and ecological risks of Cr, Zn, Pb, Cu, and As in sediments from three land-use types using pollution indices (CF, PLI, RI) and the geo-accumulation index (I_geo). Multivariate analysis explores the relationships between metals and their potential sources. The results show significant differences in pollution levels (p < 0.05), with culture ponds having the highest pollution and ecological risk (RI = 73). As is the primary ecological risk factor (Er = 129). Zn and Cr are positively correlated with organic matter, while As and Pb show negative correlations with pH and salinity. Culture ponds increase heavy metal load and ecological risk, adversely impacting the mangrove ecosystem. These findings provide scientific support for land-use management and pollution control in mangrove wetlands. Full article

Despite recent improvements in particulate matter (PM) pollution, haze events still frequently occur in many regions of China. Volatile organic compounds (VOCs), as key precursors in atmospheric photochemistry, play a crucial role in haze formation. To elucidate their contributions, high-resolution hourly VOC measurements were conducted in Shaoxing, an industrial city in eastern China, during a winter field campaign from 1 December 2023 to 15 January 2024. The VOC groups were dominated by alkanes (31.5–53.8%), followed by alkenes (7.1–15.1%) and aromatics (6.7–14.1%). Positive Matrix Factorization (PMF) analysis resolved six major VOC sources: vehicle emissions (VE, 33.8%), combustion sources (CS, 20.0%), industrial emissions (IE, 13.4%), gasoline evaporation (GE, 14.6%), solvent usage (SU, 6.9%), and biogenic activities (BA, 12.6%). Based on the PMF results, we further evaluated the source-specific contributions of VOCs to OH radical loss rate (L_OH), ozone formation potential (OFP), and secondary organic aerosol potential (SOAP). During the haze episode, GE was the dominant driver of L_OH (33%), while IE (23%), GE (22%), and VE (20%) were major SOAP contributors. In contrast, during the other periods, CS contributed most to both OFP (24%) and SOAP (28%), followed by VE (22–23%). Overall, our study highlights the critical role of anthropogenic activities in driving secondary pollution and suggests that sector-specific mitigation strategies hold significant potential for local haze abatement. Full article

Edible trees, such as Bordão-de-velho (BVP; Samanea tubulosa), are being studied for their nutritional potential and the presence of bioactive compounds that influence ruminal fermentation. This study aimed to evaluate, using an in vitro assay, the effects of increasing the inclusion of BVP pods in dairy cow diets formulated with different energy levels. The experiment was conducted with eight treatments obtained from a 4 × 2 factorial arrangement, containing four levels of pod inclusion (0, 100, 200, and 300 g/kg dry matter) and two dietary energy levels (high and low). Increasing BVP levels resulted in a linear reduction in gas production from digestible organic matter in low-energy diets, without altering dry matter and organic matter digestibility or methane production. There was an increase in pH and in the acetate/propionate ratio, along with a reduction in the concentrations of short-chain fatty acids and isoacids. In conclusion, Samanea tubulosa pods improve fermentation efficiency and reduce gas production, making them a promising forage source for low-productivity animal diets. Full article

Tight sandstone gas constitutes a strategically significant resource in the exploration of unconventional hydrocarbon systems. Current understanding of the geochemical composition and genesis of tight sandstone gas in the Daning–Jixian Block, southeastern Ordos Basin, is insufficient, which hampers a comprehensive assessment of its resource potential. This study is the first to systematically investigate the geochemical characteristics and genetic origin of high-maturity tight sandstone gas in the southeastern Ordos Basin’s Daning–Jixian Block. Gas specimens were systematically acquired from multiple stratigraphic units within the reservoir interval and subjected to compositional and carbon–hydrogen isotope analysis. Compared with other gas fields in the Ordos Basin, the Daning–Jixian Block has higher average methane concentration, and notably lower ethane and propane concentrations; its average δ¹³C₁ and δ²H-CH₄ is heavier, while δ¹³C₂ and δ¹³C₃ are lighter. Based on the δ¹³C₁-δ²H-CH₄ diagram, all gas samples from the block and other basin gas fields fall into the geothermal, hydrothermal and crystalline gas domain, indicating gas genesis associated with over-mature organic matter interacting with external hydrogen. Milkov genetic diagram analysis reveals that the natural gas consists of primarily early-stage kerogen-cracking gas, with a minor contribution from crude oil-derived gas originating from Carboniferous–Permian source rocks. Notably, samples from Daning–Jixian exhibit a unique δ¹³C₁ > δ¹³C₂ reversal, attributed to mixing effects between gas from highly mature kerogen and gas from secondary cracking of crude oil. Consequently, ethane carbon isotopes alone are insufficient for definitive genetic classification. These findings provide a new geochemical interpretation framework for analogous high-maturity tight gas reservoirs. Full article

Water scarcity is an increasingly critical global issue, particularly in arid regions like Morocco. Innovative approaches, such as the use of alternative water sources like landfill leachate, offer promising solutions. In this study, phosphate washing sludge was used to treat landfill leachate with the aim of producing irrigation-quality water and recovering nitrogen from the resulting sediment. A total of 40 L of raw leachate was treated with three concentrations of phosphate washing sludge (25%, 37%, and 50%). This volume was processed at the laboratory scale as a proof of concept for potential larger-scale applications. After 24 to 36 h of mixing and agitation, the mixture underwent sedimentation, yielding clear supernatants and nitrogen-rich sludge pellets. These pellets showed a significant increase in organic matter content, from 6.4% to 13.5%, representing an enhancement of 110.9%, thus demonstrating partial leachate depollution and organic matter enrichment. Microbiological analyses revealed a 98.9% reduction in fecal streptococci. The supernatants met irrigation water standards in terms of pH and electrical conductivity, and phytotoxicity tests on maize seeds confirmed their suitability for irrigation. Additionally, the recovered nitrogen-rich sediment presents a valuable input for composting and soil amendment. Full article

Thirty-six Dorper × Katahdin intact male lambs [44.0 ± 0.27 kg initial body weight (BW)] were used in a randomized complete block design to evaluate the effects of supplementing different organic chromium (OrCr) sources on growth performance, dietary energetics, carcass traits, meat quality, and economic return. Treatments (n = 9 lambs/treatment) were (1) Control (no Cr), (2) chromium-enriched yeast (Cr-Yeast), (3) chromium–methionine (Cr-Met), and (4) chromium–propionate (Cr-Pr). All Cr sources were provided at 1.2 mg elemental Cr/lamb/d for 45 d. Lambs received a high-energy finishing diet (78:22 concentrate/forage; steam-rolled corn-based). Dry matter intake was not affected (p = 0.583; 1.27 ± 0.034 kg/d). Compared with Control, Cr-Pr increased final BW (+5%; p = 0.025) and average daily gain (+66%; p = 0.034), and improved feed efficiency (+59%; p = 0.045) and observed-to-expected net energy ratio (+22%; p = 0.042); Cr-Met and Cr-Yeast showed intermediate responses. No differences were observed (p > 0.05) in longissimus lumborum muscle area, cold carcass weight, dressing percentage, cooling loss, or zoometric traits. Rib and rump fat thickness decreased with Cr-Met (−15 and −12%; p = 0.024 and p = 0.048) and with Cr-Pr (−19 and −13%; p = 0.024 and p = 0.048), and all OrCr sources reduced omental (−6 to −25%; p = 0.034), mesenteric (≈−7%; p = 0.042), visceral (−12 to −16%; p = 0.034), and perirenal fat (−25 to −39%; p = 0.028). Empty body weight and hot carcass weight increased with Cr-Pr (p = 0.029 and p = 0.031, respectively). Cr-Yeast and Cr-Pr increased muscle proportion (+5 to +7%; p = 0.003) and reduced carcass fat (−20 to −27%; p = 0.018), improving the muscle/fat ratio (+42 to +50%; p = 0.045). Cr-Pr improved water-holding capacity (+27%; p = 0.014) without affecting pH_24h, purge loss, cooking loss, or Warner–Bratzler shear force (p > 0.05). Cr-Pr reduced cost per kg of gain (−31%; p < 0.001) and increased income (+188% live; +105% carcass; p < 0.001), whereas Cr-Met and Cr-Yeast provided moderate benefits. In conclusion, OrCr supplementation improved dietary energy utilization, growth, carcass traits, and meat quality, enhancing profitability in lambs finished at heavier weights, with Cr-Pr producing the greatest responses. Full article

Nitrogen (N) is the most widely used nutrient in agriculture in the form of urea, yet it is one of the least efficient in terms of application due to losses through volatilization and leaching. The combination of urea with micronutrient sources, especially in the form of nanoparticles, is a promising technology for reducing these losses. Two greenhouse experiments were conducted with the objective of evaluating the influence of coating urea with zinc oxide nanoparticles (NPZnO) and iron oxide nanoparticles (NPFe₂O₃), associated with elemental sulfur (S°), on the leaching of mineral nitrogen and the production of dry mass and accumulation of N in young corn plants. The coating (0.26% w/w) of urea with elemental sulfur (S°) and NPZnO and NPFe₂O₃ reduced N losses through leaching (−21.3%) and delayed the nitrification process of N in the soil (−71.8%). This coating increased the efficiency of nitrogen fertilization in young corn plants, boosting the production of dry mass in leaves (+39.4%), stems (+68.8%), and roots (+61.6%), as well as the absorption of N in the above-ground biomass (+64.1%), compared to conventional urea. The use of urea coated with NPZnO and NPFe₂O₃ associated with S° is an environmentally sound solution for supplying N and micronutrients such as Fe and Zn in a more efficient and sustainable manner, especially in sandy soils with low organic matter content, which are common in the semi-arid region of Brazil. Full article

The Shahezi Formation is the main source rock formation in the deep part of the Xujiaweizi Fault Depression. In this study, firstly, based on measured pressure data and logging data, analyzed with methods such as fluid inclusion testing and basin numerical simulation, the pressure evolution history of the Shahezi Formation was systematically reconstructed. Secondly, hydrocarbon generation simulation experiments were carried out under pressures of 45, 70, and 100 MPa to reveal the influence of pressure on the hydrocarbon generation and expulsion process of organic matter. The results showed that the evolution of the pore pressure could be divided into four stages. Prior to the end of the early Cretaceous (~104 Ma), the Xujiaweizi Fault Depression was in a normal-pressure state. In the early Late Cretaceous (104–78 Ma), overpressure was generated in the source rocks due to undercompaction and hydrocarbon generation, which was a stage of rapid pressure increase. In the Late Cretaceous (78–65 Ma), a large amount of gas was generated in the source rocks, and the pressure reached the highest value. From the early Paleogene to the present (65–0 Ma), it has been a stage of slow pressure decrease. The strata have experienced slow uplift, and the pressure has gradually decreased. The effect of high pressure can promote the conversion of heavy hydrocarbon gases in the C1–C5 components to methane, but the promoting effect is limited. In contrast, high pressure has a certain effect on the preservation of liquid hydrocarbon components, and this preservation effect may be caused by the conversion of unstable saturated hydrocarbons to aromatic hydrocarbons. Full article

The structure and function of alpine steppes are maintained largely by dominant species, which in turn determine the productivity and stability of plant communities. Nutrient acquisition and stress regulation may, to some extent, be mediated by phyllospheric microbiota at the interface of plants with the atmosphere, and phyllospheric microbes are capable of amplifying and transmitting vegetation responses to degradation. Previous research has mainly addressed climate, soil, vegetation and soil microbiota or has assessed phyllosphere communities as a whole, thereby overlooking the specific responses of phyllospheric bacteria associated with the vegetation-dominant species Stipa purpurea along gradients of vegetation degradation in alpine steppes. In this study, we characterised vegetation degradation at the community level (from non-degraded to severely degraded grasslands) and quantified associated changes in the dominant species Stipa purpurea (cover, height and aboveground biomass) and its phyllospheric bacterial communities, in order to elucidate response patterns within the coupled system of host plants, phyllosphere microbiota, climate (mean annual temperature and precipitation) and soil physicochemical properties. Compared with non-degraded (ND) grasslands, degraded sites had a 22.6% lower mean annual temperature (MAT) and reductions in total nitrogen, nitrate nitrogen, organic matter (OM) and soil quality index (SQI) of 49.4%, 55.6%, 46.8% and 47.6%, respectively. Plant community cover and the aboveground biomass of dominant species declined significantly with increasing degradation. Along the vegetation-degradation gradient from non-degraded to severely degraded alpine steppes, microbial source-tracking analysis of the phyllosphere of the dominant species Stipa purpurea revealed a sharp decline in the contribution of phyllospheric bacterial sources. Estimated contributions from non-degraded sites to lightly, moderately and severely degraded sites were 95.68%, 62.21% and 6.89%, respectively, whereas contributions from lightly to moderately degraded and from moderately to severely degraded sites were 34.89% and 16.47%, respectively. Bacterial richness increased significantly, and β diversity diverged under severe degradation (PERMANOVA, F = 5.48, p < 0.01). From light to moderate degradation, biomass and relative cover of the dominant species decreased significantly, while the phyllosphere bacterial community appeared more strongly influenced by the host than by environmental deterioration; the community microbial turnover index (CMTB) and microbial resistance potential increased slightly but non-significantly (p > 0.05). Under severe degradation, worsening soil conditions and hydrothermal regimes exerted a stronger influence than the host, and CMTB and microbial resistance potential decreased by 6.5% and 34.1%, respectively (p < 0.05). Random-forest analysis indicated that climate, soil, phyllosphere diversity and microbial resistance jointly accounted for 42.1% of the variation in constructive-species biomass (R² = 0.42, p < 0.01), with the remaining variation likely driven by unmeasured biotic and abiotic factors. Soil contributed the most (21.73%), followed by phyllosphere diversity (9.87%) and climate (8.62%), whereas microbial resistance had a minor effect (1.86%). Specifically, soil organic matter (OM) was positively correlated with biomass, whereas richness, beta diversity and MAT were negatively correlated (p < 0.05). Taken together, our results suggest that under ongoing warming on the Qinghai–Tibet Plateau, management of alpine steppes should prioritise grasslands in the early stages of degradation. In these systems, higher soil organic matter is associated with greater phyllospheric microbial resistance potential and increased biomass of Stipa purpurea, which may help stabilise this dominant species and slow further vegetation degradation. Full article

Achieving sustainable air quality improvements in rapidly industrializing regions requires a clear understanding of the emission sources that drive the formation of PM_2.5 pollution. This study identified the sources of PM_2.5 and its organic carbon (OC) in Zibo, a typical industrial city in Northern China Plain, using the Positive Matrix Factorization (PMF) model during five pollution episodes (P1–P5) from 26 November 2022 to 9 February 2023. A high-temporal-resolution online observation of 61 organic molecular tracers was conducted using an Aerodyne TAG stand-alone system combined with a gas chromatograph–mass spectrometer (TAG-GC/MS) system. The results indicate that during pollution episodes, PM_2.5 was contributed by 32.4% from coal combustion and 27.1% from inorganic secondary sources. Moreover, fireworks contributed 13.1% of PM_2.5, primarily due to the extensive fireworks during the Gregorian and Lunar New Year celebrations. Similarly, coal combustion was the largest contributor to OC, followed by mobile sources and secondary organic aerosol (SOA) sources, accounting for 16.2% and 15.3%, respectively. Although fireworks contributed significantly to PM_2.5 concentrations (31.6% in P4 of 20–24 January 2023), their impact on OC was negligible. Overall, a combination of local and regional industrial combustion emissions, mobile sources, extensive residential heating during cold weather, and unfavorable meteorological conditions led to elevated secondary aerosol concentrations and the occurrence of this haze episode. The high-temporal-resolution measurements obtained using the TAG-GC/MS system, which provided more information on source-indicating organic molecules (tracers), significantly enhanced the source apportionment capability of PM_2.5 and OC. The findings provide science-based evidence for designing more sustainable emission control strategies, highlighting that the coordinated management of coal combustion, mobile emissions, and wintertime heating is essential for long-term air quality and public health benefits. Full article

This study developed a rapid and real-time model for predicting total organic carbon (TOC), which is an alternative to the conventional biochemical oxygen demand (BOD) and chemical oxygen demand (COD) indicators. The influence of input variable selection methods and machine learning hyperparameter tuning on TOC prediction accuracy was compared using ten-year water quality monitoring data. The analysis showed that TOC exhibited strong correlations with COD, T-P, BOD, and ammonia nitrogen (NH₃-N). Principal component analysis confirmed that the primary factors driving TOC variation were associated with organic matter and nutrient pollution. Prediction models were developed using a multilayer perceptron (MLP) and random forest (RF). On average, the MLP model outperformed the RF model by approximately 20%, and COD consistently appeared as a critical predictor in all top-ranked feature sets. Finally, grid search-based hyperparameter tuning of the MLP model with the optimal variable set (DO, COD, T-P, DTP, PO₄-P) increased the coefficient of determination from 0.7496 to 0.7562. The findings demonstrate that precise exploration of variable combinations and stronger model regularization are essential for improving prediction performance in TOC modeling. This study provides a foundation for future development of predictive models that integrate external environmental factors such as nonpoint source pollution. Full article