Search Results (1,598)

This study presents the development of eco-friendly cementitious materials for soil stabilization, based on alkaline multi-industrial waste (AMIW), using steel slag (SS), blast furnace slag (BFS), carbide slag (CS), fly ash (FA) and flue gas desulfurization gypsum (FGDG) as the raw materials. The optimal AMIW-based cementitious material composition determined through orthogonal experiments was SS:CS:FGDG:BFS:FA = 15:10:15:44:16. Central composite design (CCD) in response surface methodology (RSM) was employed to optimize the curing process parameters. The maximum 7-day unconfined compressive strength (7d UCS) was achieved under the optimal conditions of 18.51% moisture content, 11.46% curing agent content and 26.48 min of mix-grinding time. The 7d UCS of the AMIW-stabilized soil showed a 24% improvement over ordinary Portland cement (OPC)-stabilized soil. Rietveld refinement results demonstrated that the main hydration products of the stabilized soil were C-S-H and ettringite. After curing for 7 days to 28 days, the C-S-H content increased from 3.31% to 5.76%, while the ettringite content increased from 1.41% to 3.54%. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) analysis revealed that with the extension of curing time, the pores of the stabilized soil become smaller and the structure becomes denser, resulting in an improvement in compressive strength. Full article

The high-temperature and high-humidity conditions arising from the biochemical degradation of landfill waste result in significant temperature gradients within the landfill cover. The effects of waste temperature on landfill gas transport and microbial aerobic methane oxidation are not fully understood. In this study, a fully coupled theoretical model was developed to simulate the interactions of moisture, heat, and gas transport within a capillary barrier cover. A series of parametric studies were carried out to investigate the influence of the combined effects of temperature gradient, initial soil moisture content, and landfill gas generation rate on methane transport, oxidation, and emissions. The simulated results indicated that increasing waste temperature intensified the temperature gradient, leading to higher surface evaporation rates and variations in methane oxidation efficiencies. Additionally, variations in initial soil moisture content and landfill gas generation rates were found to significantly impact gas migration and methane oxidation in the cover. This study demonstrates the critical role of waste temperature in landfill gas migration within landfill cover systems, providing technical methodologies for the optimized design of soil cover systems. Full article

Long-term and extensive mineral mining in the Kuermutu mine section of the Two Rivers Nature Reserve in the Altai region has disrupted the ecological balance between soil and vegetation. To assess the effectiveness of various restoration measures in this abandoned mine area, we compared two restoration approaches—natural turf transplantation (NTT) and replanted economic crop grassland (ARGC)—against an unaltered control (original grassland). We employed 11 evaluation indices to conduct soil and vegetation surveys. We developed a comprehensive evaluation model using the Analytic Hierarchy Process (AHP) to assess restoration outcomes for each grassland type. Our findings indicate that both NTT and ARGC significantly improved ecological conditions, such as reducing soil fine particulate matter loss and restoring vegetation cover. This brought these areas closer to their original grassland state. The species composition and community structure of the NTT and ARGC vegetation communities improved relative to the original grassland. This was due to a noticeable increase in dominant species’ importance value. Vegetation cover averaged higher scores in NTT, while the average height was greater in ARGC. The soil water content and soil organic carbon (SOC) varied significantly with depth (p < 0.05), following a general ‘V’ pattern. NTT positively impacted soil moisture content (SMC) at the surface, whereas ARGC influenced SMC in deeper layers, with the 40–50 cm soil layer achieving 48.13% of the original grassland’s SMC. SOC levels were highest in the control (original grassland), followed by ARGC and NTT, with ARGC showing the greatest organic carbon content at 20–30 cm depths. A comprehensive AHP ecological-economic evaluation revealed that restoration effectiveness scores were 0.594 for NTT and 0.669 for ARGC, translating to 59.4% and 66.9%, respectively. ARGC restoration was found to be more effective than NTT. These results provide valuable insights into ecological restoration practices for abandoned mines in Xinjiang and can guide future effectiveness evaluations. Full article

The coupled processes of ecosystem carbon and water cycles are usually evaluated using the water use efficiency (WUE), and improving WUE is crucial for maintaining the sustainability of ecosystems. However, it remains unclear whether the WUE in different ecosystem responds synchronously to the synergistic effect of the same climate factors at daily and monthly scales. Therefore, we employed a machine learning-driven factor analysis method and a geographic detector model, and we quantitatively evaluated the individual effects and the synergistic effect of climate factors on the daily mean water use efficiency (WUE_D) and monthly mean water use efficiency (WUE_M) in different ecosystems in China. Our results showed that (1) among the 10 carbon flux monitoring sites in China, WUE_D and WUE_M exhibited the highest positive correlations with the near-surface air humidity and the highest negative correlation with solar radiation. The correlation between WUE_M and climate factors was generally greater than that between WUE_D and climate factors. (2) There were significant differences in the order of importance and degree of impact of the same climate factors on WUE_D and WUE_M in the different ecosystems. Among the 10 carbon flux monitoring sites in China, the near-surface air humidity imposed the greatest influence on the WUE_D and WUE_M changes, followed by the near-surface water vapor pressure. (3) There were significant differences in the synergistic effects of the same climate factors on WUE_D and WUE_M in the different ecosystems. Among the 10 carbon flux monitoring sites in China, the WUE_D variability was most sensitive to the synergistic effect of solar radiation and photosynthetically active radiation, while the WUE_M variability was most sensitive to the synergistic effect of the near-surface air humidity and soil moisture. The research results indicated that synchronous responses of the WUE in very few ecosystems to the same climate factors and their synergistic effect occurred at daily and monthly scales. This finding enhances the understanding of sustainable water resource use and the impact of climate change on water use efficiency, providing crucial insights for improving climate-adaptive ecosystem management and sustainable water resource utilization across different ecosystems. Full article

Considerable amounts of irrigation water of vegetable crops grown in homogenous sandy soil profiles could be subjected to deep percolation water losses due to inappropriately designed surface or subsurface drip irrigation methods. This study aimed to investigate the combined influence of implementing clay soil layer in homogenous sandy soil profile of low-tech greenhouse ridges and using modified surface drip irrigation (M-DI) on soil moisture distribution and water productivity of tomatoes. In the greenhouse, a 7.5 cm thick clay soil layer was implemented 15 cm from the soil surface of each ridge as a hydraulic barrier. Three irrigation regimes (100%, 70% and 50% of ETo) were imposed with the M-DI on tomato plants and 100%ETo with surface drip irrigation (DI) as control. Regarding economic valuation, viability was preserved for the M-DI and DI methods. The outcome indicated that soil moisture spreads more horizontally than vertically on the sandy soil above the clay soil layer. The combined effect of the homogenous sandy soil profile amendment and full irrigation (100%ETo) with the M-DI irrigation method increased the tomato fruit yield by 64.5%. Furthermore, the combined influence enhanced water productivity by the M-DI to 54.7 kg/m³ compared to 32 kg/m³ by the DI. However, M-DI demonstrated dominance over DI regarding returns, yield, and profit. Economic-wise, the M-DI requires 50% less of the lateral pipelines needed by the DI in low-tech greenhouses. Adopting the M-DI with a hydraulic barrier can improve soil moisture, water productivity, yield, and returns for tomato crops in low-tech greenhouses under sandy soil conditions. Also, the M-DI with the hydraulic clay barriers was an economically viable investment compared to the DI without clay barriers for growing tomatoes in low-tech greenhouses. Full article

Soil moisture (SM) is a critical parameter in Earth’s water cycle, significantly impacting hydrological, agricultural, and meteorological research fields. The challenge of estimating surface soil moisture from synthetic aperture radar (SAR) data is compounded by the influence of vegetation coverage. This study focuses on the Weigan River and Kuche River Delta Oasis in Xinjiang, employing high-resolution Sentinel-1 and Sentinel-2 images in conjunction with a modified Water Cloud Model (WCM) and the grayscale co-occurrence matrix (GLCM) for feature parameter extraction. A soil moisture inversion method based on stacked ensemble learning is proposed, which integrates random forest, CatBoost, and LightGBM. The findings underscore the feasibility of using multi-source remote sensing data for oasis moisture inversion in arid regions. However, soil moisture content estimates tend to be overestimated above 10% and underestimated below 5%. The CatBoost model achieved the highest accuracy (R² = 0.827, RMSE = 0.014 g/g) using the top 16 feature parameter groups. Additionally, the R² values for Stacking1 and Stacking2 models saw increases of 0.008 and 0.016, respectively. Thus, integrating multi-source remote sensing data with Stacking models offers valuable support and reference for large-scale estimation of surface soil moisture content in arid oasis areas. Full article

The study of the surface energy balance characteristics of different ecosystems in the Qinghai Plateau is of great significance for a deeper understanding of land surface processes, the water cycle, and global climate change. This study aims to compare the seasonal variations in energy balance and partitioning of four typical ecosystems on the Qinghai Plateau—swamp meadows, subalpine mountain meadows, alpine shrublands, and alpine deserts. Mantel analysis and path analysis were used to explore the regulatory mechanisms of meteorological elements on energy fluxes and the Bowen ratio (β). The results showed the following: (1) Net radiation (R_n), sensible heat flux (H), and latent heat flux (LE) all exhibited a single-peak pattern of change, and the energy partitioning was closely related to the hydrothermal conditions. Swamp meadows and subalpine mountain meadows were dominated by LE throughout the year and the growing season, while H dominated in the non-growing season. Meanwhile, alpine shrublands and alpine deserts were dominated by H throughout the year. (2) β reflected the characteristics of turbulent fluxes variations and the moisture level of the underlying surface. Swamp meadows and subalpine mountain meadows were relatively moist, with the value of β all being less than 1. Alpine shrublands and deserts were comparatively arid, with the values of β all exceeding 1. The energy closure rate ranged from 48% to 90%, with better energy closure conditions observed during the growing season compared to the non-growing season. (3) Meteorological factors collectively regulated the variations in energy fluxes and its partitioning, with H and LE being primarily influenced by R_n, relative humidity (RH), and soil moisture (Ms). β was significantly affected by RH, Ms, and the saturated vapor pressure deficit (VPD). The sensitivity of the ecosystems to changes in fluxes increased with decreasing moisture, especially in alpine deserts, with Ms, VPD and RH being the most affected. Swamp meadows were significantly associated with air temperature (Ta), soil temperature (Ts), and wind speed; subalpine mountain meadows with Ta and Ts; and alpine shrublands with Ta. These results provided a basis for further analyses of the energy balance characteristics and partitioning differences of different ecosystems on the Qinghai Plateau. Full article

Exploring the complex relationship between the freeze–thaw cycle and the surface energy budget (SEB) is crucial for deepening our comprehension of climate change. Drawing upon extensive field monitoring data of the Qinghai-Tibet Plateau, this study examines how surface energy accumulation influences the thawing depth. Combined with Community Land Model 5.0 (CLM5.0), a sensitivity test was designed to explore the interplay between the freeze–thaw cycle and the SEB. It is found that the freeze–thaw cycle process significantly alters the distribution of surface energy fluxes, intensifying energy exchange between the surface and atmosphere during phase transitions. In particular, an increase of 65.6% is observed in the ground heat flux during the freezing phase, which subsequently influences the sensible and latent heat fluxes. However, it should be noted that CLM5.0 has limitations in capturing the minor changes in soil moisture content and thermal conductivity during localized freezing events, resulting in an imprecise representation of the complex freeze–thaw dynamics in cold regions. Nevertheless, these results offer valuable insights and suggestions for improving the parameterization schemes of land surface models, enhancing the accuracy and applicability of remote sensing applications and climate research. Full article

One of the latest trends in sustainable agriculture is the use of beneficial microorganisms to stimulate plant growth and biologically control phytopathogens. Bacillus subtilis, a Gram-positive soil bacterium, is recognized for its valuable properties in various biotechnological and agricultural applications. This study presents, for the first time, the successful encapsulation of B. subtilis within electrospun poly(3-hydroxybutyrate) (PHB) fibers, which are dip-coated with cellulose derivatives. In that way, the obtained fibrous biohybrid materials actively ensure the viability of the encapsulated biocontrol agent during storage and promote its normal growth when exposed to moisture. Aqueous solutions of the cellulose derivatives—sodium carboxymethyl cellulose and 2-hydroxyethyl cellulose, were used to dip-coat the electrospun PHB fibers. The study examined the effects of the type and molecular weight of these cellulose derivatives on film formation, mechanical properties, bacterial encapsulation, and growth. Scanning electron microscopy (SEM) was utilized to observe the morphology of the biohybrid materials and the encapsulated B. subtilis. Additionally, ATR-FTIR spectroscopy confirmed the surface chemical composition of the biohybrid materials and verified the successful coating of PHB fibers. Mechanical testing revealed that the coating enhanced the mechanical properties of the fibrous materials and depends on the molecular weight of the used cellulose derivatives. Viability tests demonstrated that the encapsulated B. subtilis exhibited normal growth from the prepared materials. These findings suggest that the developed fibrous biohybrid materials hold significant promise as biocontrol formulations for plant protection and growth promotion in sustainable agriculture. Full article

To mitigate the issues of severe farmland soil salinization, the environmental degradation stemming from the overuse of chemical fertilizers, and suboptimal soil composition, a study was conducted to investigate the influence of different types and ratios of organic fertilizers on the physical and chemical attributes of saline–alkali soil. This study aimed to investigate the relationship between different types and proportions of organic fertilizers, soil moisture, organic fertilizer application rates, organic carbon molecular structure, and the soil environment in saline–alkali soils. Reducing the application of chemical fertilizers and substituting them with organic fertilizers can improve the soil quality of saline–alkali lands. The results indicated that replacing a part of the urea with organic fertilizer in saline–alkali farmland reduced the soil salinity by 11.1 to 22.8% in the 0–60 cm soil layer, decreased the soil pH by 0.11 to 1.52%, and increased the soil redox potential (Eh) values by 2.5 to 4.3% in the 0–20 cm layer of the mild and moderate saline–alkali soils. It also decreased the accumulation of the soil organic matter (OM) during the growing season. Compared to commercial organic fertilizers, natural organic fertilizers increased the accumulation of the soil soluble carbon (DOC) and nitrogen (DON), resulting in less soil salinity accumulation. When commercial organic fertilizer was applied in a 1:1 ratio with inorganic fertilizer, the salt accumulation was minimized. Compared to conventional fertilization, organic fertilizer reduced the accumulation of the NH₄⁺-N (ammonium nitrogen) and NO₃⁻-N (nitrate nitrogen) in the soil by 3.1 to 22.6%. In comparison to conventional chemical fertilizers, the application of organic fertilizer in the mild and moderate saline–alkali soils increased the accumulation of the DOC, DON, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial quotient during the grain-filling stage. Specifically, it increased the DOC, DON, and DOC/DON by 12.7 to 26.7%, 12 to 59.3%, and 15.2 to 35.5%, respectively. The application of commercial organic fertilizer in the mild saline–alkali soils increased the MBC, MBN, MBC/SOC, and MBN/TN by 37.1, 65.6, 36.7, and 4.7%, respectively. Through analyzing the relative proportions of soil surface organic carbon functional groups during the grain filling period, we observed that, after the application of organic fertilizer, the OM in the mildly salinized soils primarily originated from terrestrial plant litter, whereas, in moderately salinized soils, the OM was mainly derived from microbial sources. Full article

The impact of fertilization and irrigation on heavy metal accumulation in saline–alkali soil and its underlying mechanisms are critical issues given the constraints that soil salinization places on agricultural development and crop quality. This study addressed these issues by investigating the effects of adjusting organic fertilizer types, proportions, and irrigation volumes on the physicochemical properties of lightly to moderately saline–alkali soils and analyzing the interaction mechanisms between microorganisms and heavy metals. The results indicate that the rational application of organic fertilizers combined with supplemental irrigation can mitigate soil salinity accumulation and water deficits, and reduce the soil pH, thereby enhancing soil oxidation, promoting nitrogen transformation and increasing nitrate–nitrogen levels. As the proportion of organic fertilizers increased, heavy metal residues, enrichment, and risk indices in the crop grains also increased. Compared to no irrigation, supplemental irrigation of 22 mm during the grain-filling stage increased soil surface Cd content, Zn content, and the potential ecological risk index (HRI) by 10.2%, 3.1%, and 8%, respectively, while simultaneously reducing the heavy metal content in grains by 12–13.5% and decreasing heavy metal enrichment. Principal component analysis revealed the primary factors influencing Cu and Zn residues and Cd accumulation in the crop grains. Soil salinity was significantly negatively correlated with soil pH, organic matter, total nitrogen, and ammonium nitrogen, whereas soil organic matter, total nitrogen, ammonium nitrogen, soil pH, oxidation–reduction potential, soluble nitrogen, and microbial biomass nitrogen were positively correlated. The accumulation and residues of Zn and Cu in the soil were more closely correlated with the soil properties compared to those of Cd. Specifically, Zn accumulation on the soil surface was primarily related to aliphatic organic functional groups, followed by soil salinity. Residual Zn in the crop grains was primarily associated with soil oxidation–reduction properties, followed by soil moisture content. The accumulation of Cu on the soil surface was mainly correlated with the microbial biomass carbon (MBC), whereas the residual Cu in the crop grains was primarily linked to the soil moisture content. These findings provide theoretical insights for improving saline–alkali soils and managing heavy metal contamination, with implications for sustainable agriculture and environmental protection. Full article

Texas cotton production is facing challenges from increased temperatures and extended droughts. We sought to determine whether applying a multi-species grass mulch on the surface of cotton fields in a semiarid region would mitigate some of the negative effects of climate change. We used open-top chambers (OTCs) to mimic climate warming and compared whether the effects of residue addition were similar between dryland and irrigated cotton fields located in the High Plains region of Texas during the summer of 2021. The OTCs raised the average air temperature by 2 °C. Under experimental warming, residue addition increased moisture content in non-irrigated (i.e., dryland) soils (+9.2%) and reduced the daily temperature range (by −1.4 °C) relative to uncovered soils. Furthermore, when pooled across irrigation and warming treatments, the addition of residue increased microbial biomass, soil respiration (+78.2%), and cotton yield (+15.2%) relative to uncovered soils. OTCs further enhanced the residue effects on microbial biomass by 34.9%. We also observed higher soil organic matter, microbial biomass, cotton biomass, and yield in irrigated fields compared to dryland, irrespective of residue addition. Our findings suggest that residue addition in dryland agriculture can mitigate the adverse effects of warming by stabilizing soil microclimates and promoting microbial growth and biomass by providing a more labile source of carbon, which, in turn, could boost the yield of cotton plants. Full article

In this paper, the advantages of the joint use of MHz- and GHz-frequency band impulses when employing contactless ground penetration radar (GPR) for the remote sensing of biomass, the height of the wheat canopy, and underlying soil moisture were experimentally investigated. A MHz-frequency band nanosecond impulse with a duration of 1.2 ns (average frequency of 750 MHz and spectrum bandwidth of 580 MHz, at a level of –6 dB) was emitted and received by a GPR OKO-3 equipped with an AB-900 M3 antenna unit. A GHz-frequency band sub-nanosecond impulse with a duration of 0.5 ns (average frequency of 3.2 GHz and spectral bandwidth of 1.36 GHz, at a level of −6 dB) was generated using a horn antenna and a Keysight FieldFox N9917B 18 GHz vector network analyzer. It has been shown that changes in the relative amplitudes and time delays of nanosecond impulses, reflected from a soil surface covered with wheat at a height from 0 to 87 cm and fresh above-ground biomass (AGB) from 0 to 1.5 kg/m², do not exceed 6% and 0.09 ns, respectively. GPR nanosecond impulses reflected/scattered by the wheat canopy have not been detected. In this research, sub-nanosecond impulses reflected/scattered by the wheat canopy have been confidently identified and make it possible to measure the wheat height (fresh AGB up to 2.3 kg/m² and height up to 104 cm) with a determination coefficient (R²) of ~0.99 and a bias of ~−7 cm, as well as fresh AGB where R² = 0.97, with a bias = −0.09 kg/m², and a root-mean-square error of 0.1 kg/m². The joint use of impulses in two different MHz- and GHz-frequency bands will, in the future, make it possible to create UAV-based reflectometers for simultaneously mapping the soil moisture, height, and biomass of vegetation for precision farming systems. Full article

Anthrax, a zoonotic disease affecting both livestock and humans globally, is caused by Bacillus anthracis. The objectives of this study were the following: (1) to identify environmental risk factors for anthrax and use this information to develop an improved predictive risk map, and (2) to estimate spatial variation in basic reproduction number (Ro) and herd immunity threshold at the village level, which can be used to optimize vaccination policies within high-risk regions. Based on the anthrax incidences from 2000–2023 and vaccine administration figures between 2008 and 2022 in Karnataka, this study depicted spatiotemporal pattern analysis to derive a risk map employing machine learning algorithms and estimate Ro and herd immunity threshold for better vaccination coverage. Risk factors considered were key meteorological, remote sensing, soil, and geographical parameters. Spatial autocorrelation and SaTScan analysis revealed the presence of hotspots and clusters predominantly in the southern, central, and uppermost northern districts of Karnataka and temporal cluster distribution between June and September. Factors significantly associated with anthrax were air temperature, surface pressure, land surface temperature (LST), enhanced vegetation index (EVI), potential evapotranspiration (PET), soil temperature, soil moisture, pH, available potassium, sulphur, and boron, elevation, and proximity to waterbodies and waterways. Ensemble technique with random forest and classification tree models were used to improve the prediction accuracy of anthrax. High-risk areas are expected in villages in the southern, central, and extreme northern districts of Karnataka. The estimated Ro revealed 11 high-risk districts with Ro > 1.50 and respective herd immunity thresholds ranging from 11.24% to 55.47%, and the assessment of vaccination coverage at the 70%, 80%, and 90% vaccine efficacy levels, all serving for need-based strategic vaccine allocation. A comparison analysis of vaccinations administered and vaccination coverage estimated in this study is used to illustrate difference in the supply and vaccine force. The findings from the present study may support in planning preventive interventions, resource allocation, especially of vaccines, and other control strategies against anthrax across Karnataka, specifically focusing on predicted high-risk regions. Full article

Countries face challenges of excess, scarcity, pollution, and uneven water distribution. This study highlights the benefits of advances in groundwater engineering that improve the understanding of utilizing local geological characteristics due to their crucial role in resisting drought in southern Lebanon. The type of drought in the region was determined using the Standardized Precipitation Index (SPI), Standardized Vegetation Index (NDVI), Vegetation Condition Index (VCI), and Soil Moisture Anomaly Index (SM). The dry aquifer and its characteristics were analyzed using mathematical equations and established hydrogeological principles, including Darcy’s law. Additionally, a morphometric assessment of the Litani River was performed to evaluate its suitability for artificial recharge, where the optimal placement of the water barrier and recharge tunnels was determined using Spearman’s rank correlation coefficient. This analysis involved excluding certain parameters based on the Shapiro–Wilk test for normality. Accordingly, using the Geographic Information System (GIS), we modeled and simulated the potential water table. The results showed the importance and validity of linking groundwater engineering and morphometric characteristics in combating the drought of groundwater layers. The Eocene layer showed a clearer trend for the possibility of being artificially recharged from the Litani River than any other layer. The results showed that the proposed method can enhance artificial recharge, raise the groundwater level to four levels, and transform it into a large, saturated thickness. On the other hand, it was noted that the groundwater levels near the surface will cover most of the area of the studied region and could potentially store more than one billion cubic meters of water, mitigating the effects of climate change for decades. Full article