Search Results (171)

This study aims to analyze the bending behavior of polylactic acid (PLA) structures made by fusion deposition modeling (FDM) technology. The investigation analyzed chiral structures such as lozenge and clepsydra, as well as geometries with wavy patterns such as roller and Es, in addition to a honeycomb structure. All geometries have a relative density of 50%. After being subjected to three-point bending tests, the capacity to spring back with respect to the bending angle and the shape recovery of the structures were measured. The roller and lozenge structures demonstrated the best performance, with shape recovery assessed through three consecutive hot water immersion cycles. The lozenge structure exhibits 25% higher energy absorption than the roller, but the latter ensures better replicability and shape stability. Additionally, the roller absorbs 15% less energy than the lozenge, which experiences a 27% decrease in absorption between the first and second cycle. This work provides new insights into the bending-based energy absorption and recovery behavior of PLA metamaterials, relevant for applications in adaptive and energy-dissipating systems. Full article

In wet subtropical environments, perennial groundcovers are common in horticultural plantations to protect the soil from erosion. However, there has been little investigation into whether seeding annual cover crops into the perennial groundcovers provides additional soil services including carbon and nutrient cycling in these systems. To investigate this, farmer participatory field trials were conducted in commercial avocado, macadamia, and coffee plantations in the wet Australian subtropics. Cover crops were direct-seeded into existing inter-row groundcovers in winter (cool season cover crops), and into the same plots the following summer (warm season cover crops). Inter-row biomass was quantified at the end of winter and summer in the control (no cover crop) and cover crops treatments. Soil carbon and nutrient cycling parameters including hot water extractable carbon, water soluble carbon, autoclavable citrate-extractable protein and soil enzyme activities were quantified every two months from early spring (September) 2021 to late autumn (May) 2022. Seeded cover crops produced 500 to 800 kg ha⁻¹ more total inter-row biomass over winter at the avocado coffee sites, and 3000 kg ha⁻¹ biomass in summer at the coffee site. However, they had no effect on biomass production in either season at the macadamia site. Soil functional parameters changed with season (i.e., time of sampling), with few significant effects of cover crop treatments on soil function parameters across the three sits. Growing a highly productive annual summer cover crop at the coffee site led to suppression and death of perennial groundcovers, exposing bare soil in the inter-row by 3 weeks after termination of the summer cover crop. Annual cover crops seeded into existing perennial groundcovers in tree crop systems had few significant impacts on soil biological function over the 12-month period, and their integration needs careful management to avoid investment losses and exacerbating the risk of soil erosion on sloping lands in the wet subtropics. Full article

A clear understanding of drought perceptions and adaptation behaviors adopted by farmers is an important way to cope with climate change and achieve sustainable agricultural development. Karst is a type of landscape where the dissolving of the bedrock has created sinkholes, sinking streams, caves, springs, and other characteristic features. The study took the Huajiang karst dry-hot river valley area located in the southwestern part of Guizhou as the study area and used questionnaire survey method, the index of perception and the diversity index of adaptation strategy to explore the risk perception, adaptation perception and adaptation behavior of farmers to non-climatic droughts in the subtropical karst dry-hot valleys. A total of 530 questionnaires were distributed and 520 were returned. The results show that (1) the farmers’ risk perception of drought is stronger than adaptation perception, which shows that although farmers are well aware of the possible risks posed by drought, their subjective initiative and motivation to adapt to drought are weaker; (2) in the face of drought, farmers prioritize selected non-farm measures for adaptation, followed by crop management and finally water resource management; and (3) compared to farmers in arid and semi-arid regions, those in karst hot-dry river valleys exhibit distinct adaptive behaviors in response to drought, particularly in water resource management. Full article

Hydrogeochemical characteristics and temperature variations in fault-controlled, deep-circulation thermal springs elucidate water–rock interaction dynamics and hydrothermal circulation depths, providing critical insights into fault permeability and stress accumulation. To investigate the coexistence of high-temperature and medium-low-temperature thermal springs on small-scale faults and their distinct circulation mechanisms, hydrochemical and isotopic analyses were conducted on 13 water samples (9 proximal on the Xiangbaihe Fault) in western Yunnan. The hot springs along the Xiangbaihe Fault are predominantly classified as the Na-HCO₃ type, derived from carbonate and aluminosilicate hydrolysis. δ²H and δ¹⁸O confirmed a meteoric origin, with recharge elevations spanning 2465–3286 m (Gaoligong Mountain). Inverse hydrochemical modeling demonstrated progressive mineral transfer and water–rock interactions along the fault’s east–west axis. Conservative elements (Cl, Li) suggested a shared geothermal fluid source or reservoir affiliation. BLZ reservoir temperatures (194–221 °C) were classified as a high-temperature system, whereas others (58–150 °C) represented medium-low-temperature systems. Although each thermal spring represents a distinct geothermal system, reservoir interconnectivity is inferred. Notably, despite uniform lithology, variations in spring temperature and elemental composition are attributed to a subsurface magma chamber beneath BLZ, heterogeneous fault geometries, differential reservoir temperatures, and variable cold-water mixing ratios. This study establishes a framework for understanding groundwater circulation in small-scale fault-associated geothermal systems, with implications for tectonic activity monitoring and geothermal resource assessment. Full article

Compound dry–hot events refer to climate phenomena where drought and high temperatures occur simultaneously. Compared to single extreme events, compound dry–hot events may have greater adverse impacts. This study uses high-spatial-resolution observational data (i.e., temperature, precipitation, and climate water balance) to cluster and identify spring compound dry–hot events in the Pearl River Basin over the past nearly 50 years. It further investigates the associated large-scale atmospheric circulation conditions during compound dry–hot events. Using three clustering methods and twenty-six evaluation criteria, six events are identified. These events primarily exhibit negative anomalies in precipitation and climate water balance and positive anomalies in temperature. The spatial distribution results show that moisture deficits during compound events are mainly concentrated in the eastern Pearl River Basin, especially in the Pearl River Delta region. An atmospheric circulation analysis indicates that spring compound dry–hot events in the Pearl River Basin are commonly accompanied by persistent abnormal high-pressure systems, relatively weak westerly transport from subtropical regions such as the Indian Ocean and the Bay of Bengal (20–25 °N), and limited moisture input from the western Pacific region. The results of this study can help to better understand and analyze the risk changes of extreme events in the context of global warming. Full article

On 23 January 2024, a M_S7.1 earthquake struck Wushi County, Xinjiang Uygur Autonomous Region, marking the largest seismic event in the Southern Tianshan (STS) region in the past century. This study investigates the relationship between hydrothermal fluid circulation and seismic activity by analyzing the chemical composition and origin of fluids in natural hot springs along the Maidan Fracture (MDF). Results reveal two distinct hydrochemical water types (Ca-HCO₃ and Ca-Mg-Cl). The δD and δ¹⁸O values indicating spring water are influenced by atmospheric precipitation input and altitude. Circulation depths (621–3492 m) and thermal reservoir temperatures (18–90 °C) were estimated. Notably, the high ³He/⁴He ratios (3.71 Ra) and mantle-derived ³He content reached 46.48%, confirming that complex gas–water–rock interactions occur at fracture intersections. Continuous monitoring at site S13 (144 km from the epicenter of the Wushi M_S7.1 earthquake) captured pre-and post-seismic hydrogeochemical fingerprints linked to the Wushi MS7.1 earthquake. Stress accumulation along the MDF induced permeability changes, perturbing hydrogeochemical equilibrium. At 42 days pre-Wushi M_S7.1 earthquake, δ¹³C DIC exceeded +2σ thresholds (−2.12‰), signaling deep fracture expansion and CO₂ release. By 38 days pre-Wushi M_S7.1 earthquake, Na⁺, SO₄²⁻, and δ¹⁸O surpassed 2σ levels, reflecting hydraulic connection between deep-seated and shallow fracture networks. Ion concentrations and isotope values showed dynamic shifts during the earthquake, which revealed episodic stress transfer along fault asperities. Post-Wushi M_S7.1 earthquake, fracture closure reduced deep fluid input, causing δ¹³C DIC to drop to −4.89‰, with ion concentrations returning to baseline within 34 days. Trace elements such as Be and Sr exhibited anomalies 12 days before the Wushi M_S7.1 earthquake, while elements like Li, B, and Rb showed anomalies 24 days after the Wushi M_S7.1 earthquake. Hydrochemical monitoring of hot springs captures such critical stress-induced signals, offering vital insights for earthquake forecasting in tectonically active regions. Full article

This study investigated the formation mechanism of the Kahui Geothermal Field in Western Sichuan, China, using geophysical and geochemical approaches to elucidate its geological structure and geothermal origins. This study employed a combination of 2D and 3D inversion techniques involved in natural electromagnetic methods (magnetotelluric, MT, and audio magnetotelluric, AMT) along with the analysis of hydrogeochemical samples to achieve a comprehensive understanding of the geothermal system. Geophysical inversion revealed a three-layer resistivity structure within the upper 2.5 km of the study area. A geological interpretation was conducted on the resistivity structure model, identifying two faults, the Litang Fault and the Kahui Fault. The analysis suggested that the shallow part of the Kahui Geothermal Field is controlled by the Kahui Fault. Hydrochemical analysis showed that the water chemistry of the Kahui Geothermal Field is of the HCO₃−Na type, primarily sourced from atmospheric precipitation. The deep heat source of the Kahui Geothermal Field was attributed to the partial melting of the middle crust, driven by the upwelling of mantle fluids. This process provides the necessary thermal energy for the geothermal system. Atmospheric precipitation infiltrates through tectonic fractures, undergoes deep circulation and heating, and interacts with the host rocks. The heated fluids then rise along faults and mix with shallow cold water, ultimately emerging as hot springs. Full article

Type IV pili (T4P) machinery is critical for bacterial surface motility, protein secretion, and DNA uptake. This review highlights the ecological significance of T4P-dependent motility in Thermus thermophilus, a thermophilic bacterium isolated from hot springs. Unlike swimming motility, the T4P machinery enables bacteria to move over two-dimensional surfaces through repeated cycles of extension and retraction of pilus filaments. Notably, T. thermophilus exhibits upstream-directed migration under shear stress, known as rheotaxis, which appears to represent an adaptive strategy unique to thermophilic bacteria thriving in rapid water flows. Furthermore, T4P contributes to the capture of DNA and phages, indicating their multifunctionality in natural environments. Understanding the T4P dynamics provides insights into bacterial survival and evolution in extreme habitats. Full article

In this study, survey methods including seismic techniques and controlled-source audio-frequency magnetotelluric, drilling, and pumping tests were employed to investigate the geothermal systems and their formation mechanisms in northern Shanxi Province, China. The following characteristics were observed: (1) Geothermal resources in northern Shanxi Province are primarily located in Archean metamorphic rocks and fracture zone aquifer groups. The direct heat source is likely uncooled magma chambers in the middle-upper crust, whereas the overlying layers consist of Quaternary, Neogene, and Paleogene deposits. (2) The high-temperature geothermal system is of the convective-conductive type: atmospheric precipitation and surface water infiltrate pore spaces and fault fractures to reach thermal storage, where they are heated. Hot water then rises along the fracture channels and emerges as shallow hot springs, and ongoing extensional tectonic activity has caused asthenospheric upwelling. The partial melting of the upper mantle forms basic basaltic magma, which ascends to the middle-upper crust and forms multiple magma chambers. Their heat is transferred to the shallow subsurface, causing geothermal anomalies. (3) Borehole YG-1 findings revealed that these geothermal resources are primarily static reserves. Our findings provide a foundation for further geothermal development in the region, including the strategic deployment of wells to improve geothermal energy extraction. Full article

This study investigates the hydrological processes and water body transformation mechanisms in the Yuanmou dry–hot valley, focusing on precipitation, well water, spring water, river water, and reservoir water, during both wet and dry seasons. The spatiotemporal characteristics and significance of the hydrogen and oxygen stable isotopes across these water bodies were analyzed. Key findings included the following: (i) Seasonal variations in precipitation, river water, and shallow groundwater were minimal, and were primarily driven by differences in water vapor sources and transport distances during wet and dry seasons. The seasonal effects of mid-deep groundwater and reservoir water were influenced by leakage recharge from deep aquifers and temperature variations, respectively. (ii) The groundwater line-conditioned excess (lc-excess) deviated significantly from the Local Meteoric Water Line, indicating that precipitation recharge occurred primarily through slow infiltration piston flow with significant isotopic fractionation. (iii) River water was recharged by precipitation, deep groundwater, and spring water; well water by precipitation and lateral groundwater inflow; spring water by deep groundwater; and reservoir water by precipitation, groundwater, and water transfer, with strong evaporation effects. (iv) Using a binary isotope mass balance model, the recharge ratios of precipitation and groundwater to surface water were calculated to be 40% and 60%, respectively. Additionally, during the wet season, the proportion of groundwater recharge to river water increased. This study provides valuable insights into hydrological cycle processes in dry–hot valleys and offers a scientific basis for the sustainable development and management of water resources in arid regions. Full article

Microbial eukaryotes have essential roles in aquatic ecosystems, yet their diversity and ecological functions in extreme environments remain understudied compared to prokaryotes. This study aims to thoroughly characterize the composition and diversity of microbial eukaryotic communities in 14 geothermal waters across Croatia. Physicochemical analysis revealed significant variations in temperature (36–55 °C), pH (6.5–8.3), and nutrient concentrations, with all sites displaying anoxic conditions except for one. Sequencing of the V9 18S rRNA gene identified 134 taxa, predominantly from the Alveolata, Stramenopiles, and Opisthokonta supergroups. The highest diversity and richness were observed in aquifer groups with moderate temperatures and nutrient levels, while extreme sites exhibited reduced diversity. Among the key environmental factors shaping these communities, temperature, pH, and nitrate concentrations were most significant. Photoautotrophic and mixotrophic taxa, such as Ochrophyta, Dinoflagellata, and Chlorophyta, were prominent, reflecting their roles in primary production and nutrient cycling. Decomposers, including Basidiomycota and Ascomycota, were linked to organic matter degradation. Microeukaryotes showed adaptations to extreme conditions, such as thermotolerance and evolutionary shifts from phototrophy to heterotrophy, highlighting their ecological versatility. These findings underscore the potential of microbial eukaryotes in biotechnological applications, such as bioremediation and biofuel production. Genera like Tribonema and Navicula demonstrated promising capabilities in nutrient removal and CO₂ fixation. However, further research is necessary to investigate and confirm their suitability for these purposes. To summarize, our research provides new insights into understudied microbial eukaryotes in Croatian hot springs that represent a valuable model for exploring microbial diversity, ecological interactions, and industrial applications in extreme environments. Full article

Cyanobacteria are an ancient group of prokaryotes capable of oxygenic photosynthesis. Recently, thermal crises symptoms in hot springs have been associated with acute cyanopeptides poisoning. The aim of this work is to develop a fast, easy and reliable method to monitor the presence of toxic cyanopeptides in geothermal waters. The analytical method based on capillary zone electrophoresis coupled with tandem mass spectrometry (CZE-MS/MS) was developed for the simultaneous determination of 14 cyanopeptides in less than 7.5 min. A basic 50 mM ammonium acetate buffer at pH 10.2 was selected as the background electrolyte, positive electrospray ionization (ESI+) was employed for all compounds, and a salting-out assisted liquid–liquid extraction (SALLE) protocol with acetonitrile as an extraction solvent and MgSO₄ as an auxiliary salting-out agent was optimized as sample treatment. Six natural hot springs in the province of Granada (Andalucía, Spain) were sampled at the beginning of the summer season (June) and at the end (September). Biomass collected at two sample points (Santa Fe and Zújar) contained cyanobacteria cells from the genera Phormidium, Leptolyngbya, and Spirulina. Nevertheless, cyanotoxins covered by this work were not found in any of the water samples analyzed. The greenness and transferability of the method was evaluated highlighting its sustainability and applicability. Full article

In order to assess the spatial and temporal characteristics of the urban thermal environment in Zhengzhou City to supplement climate adaptation design work, based on the Landsat 8–9 OLI/TIRS C2 L2 data for 12 periods from 2019–2023, combined with the lLocal climate zone (LCZ) classification of the urban subsurface classification, in this study, we used the statistical mono-window (SMW) algorithm to invert the land surface temperature (LST) and to classify the urban heat island (UHI) effect, to analyze the differences in the spatial distribution of thermal environments in urban areas and the aggregation characteristics, and to explore the influence of LCZ landscape distribution pattern on surface temperature. The results show that the proportions of built and natural landscape types in Zhengzhou’s main metropolitan area are 79.23% and 21.77%, respectively. The most common types of landscapes are wide mid-rise (LCZ 5) structures and large-ground-floor (LCZ 8) structures, which make up 21.92% and 20.04% of the study area’s total area, respectively. The main urban area’s heat island varies with the seasons, pooling in the urban area during the summer and peaking in the winter, with strong or extremely strong heat islands centered in the suburbs and a distribution of hot and cold spots aggregated with observable features. As building heights increase, the UHI of common built landscapes (LCZ 1–6) increases and then reduces in spring, summer, and autumn and then decreases in winter as building heights increase. Water bodies (LCZ G) and dense woods (LCZ A) have the lowest UHI effects among natural settings. Building size is no longer the primary element affecting LST as buildings become taller; instead, building connectivity and clustering take center stage. Seasonal variations, variations in LCZ types, and variations in the spatial distribution pattern of LCZ are responsible for the spatial differences in the thermal environment in the study area. In summer, urban areas should see an increase in vegetation cover, and in winter, building gaps must be appropriately increased. Full article

This study investigates water–rock interactions of Taiwan hot springs by analyzing rare earth elements (REEs) concentrations and strontium (Sr) isotopes. REEs were separated from samples using RE resin, and their concentrations were measured by HR-ICPMS. Strontium was isolated using Sr^SPEC resin, and the strontium isotopic ratio was determined by MC-ICPMS. The ΣREE in the hot springs ranges from 3.17 ng/L to 29.7 µg/L, with the highest levels found in the Tatun Volcano Group, followed by springs from sedimentary and metamorphic regions. The primary factors controlling REE compositions are lithology and pH. REE patterns of hot springs can be categorized into five types, indicating that the hot springs were affected by various mechanisms. The most distinct hot spring samples are from Tatun Volcano, Ginshan, and Kuantzuling. The ⁸⁷Sr/⁸⁶Sr ratios range from 0.70468 to 0.71730, with the most radiogenic samples originating from metamorphic regions, reflecting the nature of the parent rock interacting with the hot spring water. Seawater intrusion and preferential weathering of carbonate also have minor effects on Sr isotope composition. The findings indicate that the types of surrounding rocks and the pH values of the hot springs significantly influence REE patterns and Sr isotope compositions in Taiwan’s hot springs. Full article

The dissolution of dolomite can not only provide the chemical components in hot springs but also provide a high-quality reservoir for geothermal resources. However, there is still debate about the main controlling factors and mechanisms of the dissolution process of dolomite. The Shuijing hot springs in Guizhou Province are rich in SO₄²⁻ and the geothermal reservoir is dolomite, which provides an excellent opportunity to understand the role of SO₄²⁻ in the dissolution process of dolomite. In this paper, water–rock interaction experiments were conducted at different temperatures to study the effects of SO₄²⁻, pH, and CO₂ on the dissolution of dolomite from the Shuijing hot springs geothermal reservoir. The results indicate that temperature is a significant factor affecting the chemical composition of hot springs water, with higher temperatures having a more pronounced effect on the dissolution of dolomite. At lower temperatures of 25 °C and 90 °C, the molar ratio of the released Ca²⁺ and Mg²⁺ during the dissolution of dolomite in the initial reaction stage generally approaches the Ca/Mg molar ratio of dolomite, exhibiting congruent dissolution. However, at elevated temperatures of 150 °C, the released Ca/Mg molar ratio surpasses the Ca/Mg molar ratio of dolomite, demonstrating an incongruent dissolution characteristic with Ca²⁺ being preferentially released over Mg²⁺. Additionally, the relative importance of CO₂, SO₄²⁻ and pH on the dissolution degree of dolomite is CO₂ > SO₄²⁻ > pH = 4 > pH = 7 > pH = 10. The promotion effect of SO₄²⁻ on dolomite dissolution indicates that the greater the SO₄²⁻ concentration, the stronger the dissolution of dolomite, and its dissolution ability is enhanced with the increase in temperature. Furthermore, the effect of CO₂ on the dissolution of dolomite is stronger than that of SO₄²⁻, leading to the oscillating fluctuation trend of the released Ca²⁺ and Mg²⁺. Full article