Search Results (24,908)

The salt distribution characteristics in arid areas are directly related to the sustainable development of agriculture. We study the characteristics of spatial changes of soil water and salt in farmland under the full anniversary of different culvert pipe arrangements and optimize the salt drainage parameters of underground drains suitable for the local area so as to promote the management of saline and alkaline land in Xinjiang. A subsurface drainpipe salinity test was conducted in the Yanqi Basin (Bayingoleng Mongolian Autonomous Prefecture, Xinjiang Uygur Autonomous Region, China) to analyze changes in soil water and salt dynamics before and after irrigation-induced salt flushing, assessing the impact of drainpipe deployment parameters. It was found that at a 1.4 m depth of burial, the maximum desalination rates of soil in different soil layers from the subsurface drainpipes in 20, 30, and 40 m spacing plots were 78.28%, 50.91%, and 54.52%, respectively. At a 1.6 m depth of burial, the maximum desalination rates of soil in different soil layers from the subsurface drainpipes in 20, 30, and 40 m spacing plots were 70.94%, 61.27%, and 44.12%. Reasonable deployment of subsurface drainpipes can effectively reduce soil salinity, increase the desalination rate, and improve soil water salinity condition. This study reveals the influence of the laying parameters of subsurface drainpipes on soil water salinity distribution characteristics in arid zones, which provides theoretical support and practical guidance for the management of soil salinization in arid zones. Full article

This study analyzes the mineralogical and geochemical composition of 38 surface sediment samples from the northwest African continental shelf between Cap Boujdour (26.5° N) and Cap Blanc (20.5° N). Using a multiproxy approach, sediment characteristics were assessed through grain size, calcium carbonate (CaCO₃), and organic carbon (Corg) measurements, along with X-ray diffraction (XRD) and X-ray fluorescence (XRF) for geochemical analysis. Bottom water properties, including temperature, salinity, and dissolved oxygen, were measured at various stations using a Conductivity, Temperature, and Depth (CTD) sensor. The results reveal that the inner shelf sediments are primarily mud, with high concentrations of terrigenous elements such as iron (Fe), silicon (Si), rubidium (Rb), and potassium (K), with Fe and Si concentrations ranging from 2.1 to 4.3 wt%. The middle and outer shelf sediments are dominated by biogenic carbonates, with CaCO₃ levels approaching 65%, and elevated calcium (Ca) and strontium (Sr) content. These areas also exhibit the highest bottom water temperatures (up to 16 °C), salinity (36%), and moderate oxygen levels (2–4 mL/L). Slope sediments are enriched with mud and montmorillonite, and aeolian contributions are more pronounced south of Dakhla, as indicated by elevated quartz levels (up to 20%) and the presence of illite, aluminum oxide (Al₂O₃), and iron oxide (Fe₂O₃). This study provides valuable new insights into sedimentary processes on the northwest African shelf, offering implications for regional environmental management and resource exploration. Full article

This study evaluates water body changes in Central Asia (2000–2019) using Landsat 7 data on Google Earth Engine, comparing the Modified Normalized Difference Water Index (MNDWI), OTSU algorithm, and random forest (RF). The random forest algorithm demonstrated the best overall performance in water body extraction and was selected as the analysis tool. The results reveal a significant 11.25% decline in Central Asia’s total water area over two decades, with the Aral Sea shrinking by 72.13% (2000–2019) and southern Kyrgyzstan’s glaciers decreasing by 39.23%. Pearson correlations indicate strong links between water loss and rising temperatures (−0.5583) and declining precipitation (0.6872). Seasonal fluctuations and permanent degradation (e.g., dry riverbeds) highlight climate-driven vulnerabilities, exacerbated by anthropogenic impacts. These trends threaten regional water security and ecological stability, underscoring the urgent need for adaptive resource management. The RF-GEE framework proves effective for large-scale, long-term hydrological monitoring in arid regions, offering critical insights for climate resilience strategies. Full article

Forests are complex systems in which subtle variations in terrain can reveal much about plant community structure and interspecific interactions. Despite a wealth of studies focusing on broad-scale environmental gradients, the role of fine-scale topographic nuances often remains underappreciated, particularly in subtropical settings. In our study, we explore how minute differences in microtopography—encompassing local elevation, slope, aspect, terrain position index (TPI), terrain ruggedness index (TRI), and flow direction—affect neighborhood-scale interactions among plants. We established an 11.56-hectare dynamic plot in a subtropical forest at the northern margin of China’s subtropical zone, where both microtopographic factors and neighborhood indices (density, competition, diversity) were systematically measured using 5 m × 5 m quadrats. Parameter estimation and mixed-effects models were employed to examine how microtopography influences plant spatial patterns, growth, and competitive dynamics across various life stages. Our findings demonstrate that aspect and TPI act as key drivers, redistributing light and moisture to shape conspecific clustering, heterospecific competition, and tree growth. Remarkably, sun-facing slopes promoted sapling aggregation yet intensified competitive interactions, while shaded slopes maintained stable moisture conditions that benefited mature tree survival. Moreover, in contrast to broader-scale observations, fine-scale TRI was associated with reduced species richness, highlighting scale-dependent heterogeneity effects. The intensification of plant responses with life stage indicates shifting resource demands, where light is critical during early growth, and water becomes increasingly important for later survival. This study thus advances our multiscale understanding of forest dynamics and underscores the need to integrate fine-scale abiotic and biotic interactions into conservation strategies under global change conditions. Full article

Inland lakes, contributing substantially to the global storage of sediment organic carbon (SOC), are subject to marked changes in salinity due to climate warming. The imbalance in the supply of resources, such as carbon, nitrogen, and phosphorus, in sediments leads to microbial metabolic limitations (MMLs). This, in turn, triggers the secretion of extracellular enzymes by microorganisms to mine for deficient resources by decomposing complex organic carbon. This process is a rate-limiting step in the degradation of organic carbon and, as a result, has the potential to regulate organic carbon stocks. However, the general understanding of MML patterns and their relationships with SOC content along lake salinity gradients remains elusive. This study examined 25 lakes on the Tibetan Plateau with salinity ranging from 0.13‰ to 31.06‰, analyzing MMLs through enzymatic stoichiometry. The results showed that sediment microbial metabolism was mainly limited by carbon and nitrogen, with stronger limitations at higher salinity. Water salinity and sediment pH were the main factors influencing microbial limitations, either directly or indirectly, through their effects on nutrients and microbial diversity. Additionally, the SOC content was negatively correlated with microbial carbon limitation, a relationship weakened when salinity and pH were controlled. These findings suggest that the decrease in SOC with increased salinity or pH could be driven by stronger microbial carbon limitations, offering insights into the impact of salinity changes on SOC stocks in inland lakes due to climate change. Full article

The increasing quest for greener and more sustainable polymeric materials has gained interest in the past few decades. Non-isocyanate polyurethanes (NIPUs) have attracted attention considering that they are produced through less toxic methods compared to the conventional polyurethanes (PUs) obtained from petroleum resources and toxic isocyanates. In this context, adipic acid, glycerol carbonate, 1,2-ethylenediamine, and 1,6-hexamethylenediamine, were used to synthesize NIPU_ethyl and NIPU_hexa, respectively. The obtained NIPUs were characterized using nuclear magnetic resonance spectroscopy (H-NMR spectra) and Fourier-transform infrared spectroscopy (FTIR) analysis, which verified the structures of the intermediate and final products. Calorimetric and dielectric studies provided direct and indirect support for the facilitated thermal stability of NIPU_ethyl and NIPU_hexa. Compared to the intermediate product, the NIPUs exhibit elevated glass transition temperatures, suggesting the formation of more rigid structures. The NIPUs were also tested in terms of swelling properties, and the results indicated that NIPU_hexa absorbs and withholds increased amounts of water for longer time periods compared to NIPU_ethyl, and their hydrolysis and enzymatic hydrolysis confirmed that NIPU_hexa is more stable in aqueous environments than NIPU_ethyl. Therefore, the successful production of adipic-acid-based NIPUs through a novel perspective of the polyaddition path is reported and complemented by the characterization of the obtained materials with several techniques. Full article

Climate change poses significant threats to rural communities in Kyrgyzstan, particularly for agriculture, which relies heavily on natural resources. In Naryn Province, rising temperatures and increasing natural hazards amplify vulnerabilities, especially in high mountain areas. Addressing these challenges requires understanding both environmental factors and the perceptions of affected communities, as these shape adaptive responses. This study enhances understanding of climate change impacts on communities in Naryn Province by combining environmental and social assessments through a gendered lens, with a particular focus on women. Environmental data, including air temperature, precipitation, river discharge, and satellite-derived vegetation indices, were analyzed to evaluate changes in vegetation and water resources. Social data were collected through interviews with 298 respondents (148 women and 150 men) across villages along the Naryn River, with chi-square analysis used to examine gender-specific perceptions and impacts on livelihoods. The results indicated a noticeable rise in temperatures and a slight decline in precipitation over recent decades, affecting vegetation and grazing areas near settlements. While respondents of both genders reported similar observations, differences emerged in how changes affect their roles and activities, with localized variations linked to household and agricultural responsibilities. The findings highlight the need for inclusive adaptation strategies that address diverse experiences and priorities, providing a foundation for equitable and effective climate resilience measures. Full article

The experiment of loess crack development under dry–wet cycle conditions is of great significance for the study of groundwater preferential flow channels and the prevention and control of infrastructure engineering disasters in loess areas. The loess samples in Chencang District of Baoji City, Shaanxi Province, were taken as the samples in the test. The multiple humidification and dehumidification tests were used to simulate multiple rainfall evaporation, and the moisture content changes in the loess samples during the dry–wet cycle were calculated. With the help of digital image technology, the fracture parameters of the loess samples were extracted, and the variation law of crack parameters was analyzed by combining fractal dimension, Bayesian factor, and Pearson correlation coefficient. The findings indicate that variations in soil moisture content and the number of dry and wet cycles contribute to fluctuations in soil evaporation rates, resulting in varying degrees of soil cracking development. The increase in the number of dry and wet cycles leads to evident soil shrinkage, an accelerated water evaporation process, pronounced surface deterioration, and a higher degree of crack development. The rate of crack propagation varies at different locations, with a higher rate observed in the horizontal plane compared to the vertical plane. The influence of temperature and humidity varies due to the different dimensions of cracks (horizontal and vertical). Horizontal crack development is primarily influenced by temperature, while vertical crack development is primarily influenced by humidity. Temperature and humidity inhibit each other. When one factor is dominant, the other indirectly affects crack development by influencing the dominant factor. The research findings can serve as a valuable reference for effectively mitigating and minimizing the impact of crack development-induced disasters. Full article

This research paper examines how to assess potential locations for wind turbines and photovoltaic modules by combining Geographic Information Systems (GIS) with multi-criteria decision-making (MCDM). These potential locations depend on the current legislation, where many areas are buffer zones due to limitations. The study area is Karpathos, which faces energy and water scarcity. The need to increase the penetration rate of renewable energy sources (RES) by 2030 can help this island to fulfill both its energy and water needs through RES. To apply the weighted linear combination technique, this approach considers all eligibility criteria according to the legislation. After classifying them into four zones, the MCDM results in a suitability map that displays the spatial distribution of the final score, ranging from sites that are not appropriate to areas that are highly suitable. In the photovoltaic module scenario, the buffer zone corresponds to 61% of the island, while in the wind turbine scenario, this number increases to 85%, highlighting the difficulty of finding suitable sites. A sensitivity analysis is performed to determine the impact of the criteria on the suitability of a site for both scenarios. Full article

Alpine wetland ecosystems, as important carbon sinks and water conservation areas, possess unique ecological functions. Driven by climate change and human activities, the spatial distribution changes in alpine wetlands directly affect the ecosystems and water resource management within a basin. To further refine the evolution processes of different types of alpine wetlands in different zones of a basin, this study combined multiple field surveys, unmanned aerial vehicle (UAV) flights, and high-resolution images. Based on the Google Earth Engine (GEE) cloud platform, we constructed a Random Forest model to identify and extract alpine wetlands in the Shule River Basin over a long-term period from 1987 to 2021. The results indicated that the accuracy of the extraction based on this method exceeded 90%; the main wetland types are marsh, swamp meadow, and river and lake water bodies; and the spatial–temporal distribution of each wetland type has obvious heterogeneity. In total, 90% of the swamp meadows areas were mainly scattered throughout the study area’s section 3700 to 4300 m above sea level (a.s.l.), and 80% of the marshes areas were concentrated in the Dang River source 3200 m above sea level. From 1987 to 2021, the alpine wetland in the study area showed an overall expansion trend. The total area of the wetland increased by 51,451.8 ha and the area increased by 53.5%. However, this expansion mainly occurred in the elevation zone below 4000 m after 2004, and low-altitude marsh wetland primarily dominated the expansion. The analysis of the spatial–temporal heterogeneity of alpine wetlands can provide a scientific basis for the attribution analysis of the change in alpine wetlands in inland water conservation areas, as well as for protection and rational development and utilization, and promote the healthy development of ecological environments in nature reserves. Full article

This study employs bibliometric analysis and knowledge mapping to examine trends in research on phytoplankton in Chinese reservoirs from 2004 to 2024. Utilizing the Web of Science Core Collection Database, the analysis focuses on studies related to reservoirs, phytoplankton, and cyanophytes in China. Three distinct stages in the evolution of phytoplankton research are identified: initial studies on lakes and eutrophication (2004–2010), a shift towards cyanobacteria blooms and their ecological impacts (2010–2015), and a recent focus on phytoplankton communities, carbon cycles, and nutrient cycles (2015–2024). Key hotspots such as nitrogen stable isotopes, reservoir management, lakes, and cyanobacterial blooms are identified. This study highlights a growing interest in environmental factors influencing ecosystems, biodiversity conservation, and nutrient status assessment. These findings provide a comprehensive understanding of phytoplankton research in Chinese reservoirs, revealing research hotspots, regional differences, and future directions. A collaboration network analysis among institutions and authors underscores significant contributions from the Chinese Academy of Sciences and key researchers. This study provides a foundation for future research, emphasizing the importance of addressing eutrophication, phytoplankton community dynamics, and ecosystem degradation in reservoirs. Full article

The source of sulfate in the groundwater of karst springs in the northern Taihang Mountains remains unclear due to the influence of multiple factors. To investigate this, 33 sampling points were selected in August 2022 across the exposed, covered, and buried areas of the spring basin, and water samples were collected. Hydrochemistry and sulfur–oxygen dual isotope methods were employed to examine the distribution characteristics of sulfate, δ¹⁸O_SO4, and δ³⁴S_SO4. Based on the distinct characteristics of sulfur isotopes from different sources, the sources of sulfate in various environments were qualitatively analyzed. Additionally, the contribution rates of each source were quantitatively determined using a Bayesian stable isotope mixing model. The results showed that the sulfate content in karst groundwater ranged from 16.68 to 156.84 mg/L, with an average of 62.22 mg/L, and indicated an increasing trend from exposed to covered to buried areas. The δ³⁴S_SO4 values in karst groundwater ranged from 3.1‰ to 13.5‰, with an average of 6.49‰, while the δ¹⁸O_SO4 values ranged from 2.9‰ to 10.3‰, with an average of 5.49‰. The δ³⁴S_SO4 values showed a general increasing trend across the exposed, covered, and buried areas, whereas the δ¹⁸O_SO4 values remained relatively stable across these areas. The analysis revealed that the primary sulfate sources in the exposed area were atmospheric precipitation, soil sulfate, chemical fertilizer, and sewage, contributing 19.6%, 63.5%, 9.4%, and 7.5%, respectively. In the covered area, the main sources were atmospheric precipitation, sulfide oxidation, soil sulfate, and gypsum dissolution, with contributions of 16.5%, 58.7%, 15.9%, and 8.9%, respectively. In the buried area, the sulfate primary originated from atmospheric precipitation, sulfide oxidation, and gypsum dissolution, contributing 11.6%, 78.5%, and 9.9%, respectively. This study provides critical insights into the sulfate sources in different environments, enhancing the understanding of groundwater sulfate pollution in the study area. These findings provide a scientific foundation for managing groundwater pollutants and resources in the karst regions of northern China. Full article

A novel composite cementitious material was constructed by synergistically utilizing multiple industrial solid wastes, including electrolytic manganese residue (EMR), red mud (RM), and ground granulated blast furnace slag (GGBS), with calcium hydroxide [Ca(OH)₂] as an alkaline activator. In addition, the mechanical properties of the composite cementitious materials were systematically analyzed under different raw material ratios, alkali activator dosages, and water-binder ratios. To further investigate the hydration products and mechanisms of the composite cementitious material, characterization methods, for instance, XRD, FT-IR, SEM-EDS, and TG-DTG, were employed to characterize the materials. To ensure that the composite cementitious material does not cause additional environmental pressure, it was analyzed for toxic leaching. The relevant experimental results indicate that the optimal ratio of the EMR–RM–GGBS–Ca(OH)₂ components of the composite cementitious material is EMR content of 20%, RM content of 15%, GGBS content of 52%, calcium hydroxide as alkali activator content of 13%, and water-binder ratio of 0.5. Under the optimal ratio, the composite cementitious material at 28 days exhibited a compressive strength of 27.9 MPa, as well as a flexural strength of 7.5 MPa. The hydration products in the as-synthesized composite cementitious material system primarily encompassed ettringite (AFt) and hydrated calcium silicate (C-S-H), and their tight bonding in the middle and later curing stages was the main source of engineering mechanical strength. The heavy metal concentrations in the 28-day leaching solution of the EMR–RM–GGBS–Ca(OH)₂ composite cementitious material fall within the limits prescribed by the drinking water hygiene standard (GB5749-2022), indicating that this composite material exhibits satisfactory safety performance. To sum up, it is elucidated that the novel process involved in this research provide useful references for the pollution-free treatment and resource utilization of solid wastes such as red mud and electrolytic manganese residue in the future. Full article

The sustainable utilization of water resources plays a crucial strategic role in regional economic development. The water resources carrying capacity (WRCC) is a multifaceted system influenced by diverse factors, where the interplay among water resources, societal factors, economic conditions, and ecological elements collectively determines the overall WRCC. Combining relevant research results, this paper utilized an improved TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) and GRA (grey relational analysis)-based WRCC evaluation model, introduced the panel vector autoregressive (PVAR) model to analyze the effects of interactions among subsystems, and applied the geographically and temporally weighted regression (GTWR) model for the driving analysis of WRCC. Using Ningxia Hui Autonomous Region as a case study, this paper discusses the internal dynamic relationships and driving mechanisms of the WRCC system. It also provides a new perspective for discussing WRCC in water-scarce areas and provides novel approaches for optimizing water resource management and enhancing ecological protection. The results indicate that the water resources subsystem is central to the WRCC in Ningxia, with significant interconnections among the four subsystems. However, significant spatial and temporal heterogeneity is evident across different regions. The water resources system contributes significantly, with ecological development having a positive impact on water resources. However, social and economic development has a restrictive impact on water resources. Full article

This work involves the development of a hydrodynamic fertilizer injector (HFI), which uses an integrated axial-flow turbine (AFT) and a diaphragm pump to absorb liquid fertilizer. Three structural parameters—the number of impellers (M₁), average number of blades per impeller (M₂), and arrangement pattern (M₃)—are considered, and 12 AFT designs are developed. Using a combination of CFD numerical simulations and hydraulic performance testing, the response of the AFT output power (P), blade negative pressure (NP), and fertilizer injection flow rate (Q_inj) to structural parameters and inlet pressure (H) is investigated. The results show that the normalized root mean square error between the simulated outlet flow rate (Q_s) and the measured flow rate (Q_m) is 5.1%, indicating high accuracy in the grid motion simulation method. P increases first and then decreases with the increase in impeller speed (n). The maximum P (P_max) ranges from 150.1 to 201.4 W. P_max increases with H, decreases with increasing M₁ and M₂, and shows little change with M₃. At H = 0.14 MPa, M₁ and M₂ have a significant influence, and at H ≥ 0.14 MPa, M₁ becomes the most significant factor (p < 0.05). Low-speed flow and negative pressure cavitation zones at the leading edge of the blade suction surface cause flow blockage and affect the lifespan of the AFT. These regions decrease in size as H increases but increase with M₁. The negative pressure (NP) decreases as M₂ increases. When M₁, M₂, and M₃ are 2, 3, and identical (D33), the P_max of the AFT is maximized, increasing by 6.7% to 33.5% compared with those of the other combinations. The Q_inj of D33, D34, D43, and D44 at H = 0.12~0.18 MPa range from 288.6 to 847.3 L/h, which is 38.7% to 461.0% higher than that of domestic and international venturi injectors. When considering cavitation issues and the manufacturing cost of the AFT mold, D44 may be chosen. Although its Q_inj is 7.0% lower than that of D33, NP is reduced by 37.9%. These findings provide a basis for the development of the HFI with AFT as the driving unit. Full article