Search Results (2,897)

This study characterizes the physicochemical properties of coal gangue in Huainan, a typical coal resource-based city in China, and evaluates variations in its chemical composition and associated ecological risks. The results show that the coal gangue in the Huainan mining area is composed mainly of quartz and clay minerals, with SiO₂ and Al₂O₃ together accounting for over 86% of the total composition. Rare earth element concentrations are generally higher than background levels, whereas heavy metal concentrations are generally below the risk screening values for soil contamination of agricultural land. Complex associations are observed among the elements in coal gangue. The correlation coefficients between SiO₂ and the other oxides or heavy metals range from −0.750 to −0.993, indicating significant negative correlations and suggesting that the silicate mineral phase occurs independently of other element-enriched phases. The potential ecological risk index (RI) for heavy metals ranges from 33.75 to 300.71 and is driven primarily by Hg and Cd. The RI for rare earth elements ranges from 98.9 to 220.3, with Lu as the key influencing element. The predicted probability of adverse biological effects is 14–15%. Overall, classified management of coal gangue in the Huainan mining area is recommended, together with strengthened continuous monitoring of Hg and Cd and optimization of ecological disposal strategies by integrating potential ecological risk assessment with analysis of adverse biological effects, thereby further supporting the green transition of resource-depleted cities. Full article

The dynamics of methane (CH₄), nitrous oxide (N₂O) and carbon dioxide (CO₂) in groundwater have rarely been investigated. As dissolved gases they may be transported to distant sites and, hence, to the atmosphere. Crumps Cave (CC) is located on a perched aquifer in south-central Kentucky. Water was sampled at a waterfall within the cave located 15 m below the surface, at two adjacent surface wells 15 m and 50 m deep, providing samples from the epikarst and regional aquifer, respectively. Dissolved gases and geochemistry parameters were analyzed for seasonal changes across three years of weekly monitoring (2015–2017) using Kruskal–Wallis H tests and Bonferroni-corrected pairwise comparisons. Dissolved CO₂ concentrations are mainly controlled by percolation through the epikarst, influenced by soil respiration, and vary with rainfall and seasonal temperature fluctuations. CH₄ showed a site-dependent pattern: concentrations were significantly elevated in warm seasons at the shallow and deep wells, where anaerobic conditions and agriculturally derived organic matter promote methanogenesis; no seasonal variation was detected at the cave site, where oxic conditions limit CH₄ year-round. N₂O was significantly elevated in cold seasons at all three sites, driven by cold-season denitrification of agriculturally derived nitrates. N₂O did not differ between sites, indicating seasonal temperature-driven denitrification as the primary control rather than site hydrology, with cold-season denitrification of agriculturally derived nitrates from fertilizer application. Indirect gas emissions are characteristic of karst systems and may be transported or stored in aquifers through complex interactions of groundwater recharge, microbial activity, and seasonal land-use variability. Full article

Mining of sulfide-rich deposits enhances the oxidation of sulfide minerals, generating acid mine drainage (AMD) characterized by high sulphate and dissolved metal concentrations and the formation of secondary iron minerals (hematite, goethite, and jarosite). As these minerals display diagnostic features in the visible–near-infrared (VNIR) region, multispectral satellite data provide a cost-effective means of monitoring. Here, the performances of Sentinel-2 and the VNIR bands from WorldView-3 are assessed and compared for the mapping and discrimination of secondary iron minerals in Sierra Minera de Cartagena–La Unión (SE Spain). Both datasets were analyzed using a band ratio and a parabola fitting technique focused on reflectance maxima. Band ratio results were interpreted as broad spectral patterns rather than definitive mineral identifications. Mineral maps were validated by applying X-ray diffraction on 74 surface soil samples. Although both sensors were able to reproduce the main spatial patterns of iron mineral distribution, Sentinel-2 data better discriminated hematite, goethite, and jarosite, especially when using the parabola fitting approach, whereas WorldView-3 VNIR data distinguished mainly hematite from the combined goethite–jarosite group. The better performance of Sentinel-2 is attributed to its red-edge and near-infrared band configuration. These findings indicate that freely available Sentinel-2 imagery can support systematic monitoring of oxidation processes in mining environments and contribute to environmental risk assessment in degraded landscapes. Full article

To address the ecological risks associated with highly mobile hexavalent chromium [Cr(VI)], woody biochar was functionalized with hydrogen peroxide (H₂O₂) to develop a dual-phase remediation material (H-BC) for aqueous and soil environments. Batch post-contact isotherm fitting yielded a Langmuir-fitted/extrapolated apparent retention capacity q_m of 77.44 mg/g at 328 K. This value reflects enhanced overall Cr(VI)-derived retention within the tested concentration range, rather than increased electrostatic affinity for chromate oxyanions. Empirical kinetic diagnostics and FTIR/XPS results were consistent with adsorption-coupled interfacial reduction, while DFT analysis provided qualitative support for the enhanced electronic responsiveness of H-BC. The OFG-enriched interface may facilitate short-range, non-electrostatic interfacial interactions and stabilize surface-associated Cr(III). Temperature-dependent apparent isotherm fitting suggested that elevated temperature favored the overall Cr(VI)-derived retention process under the tested conditions, and should not be interpreted as rigorous standard-state adsorption thermodynamics. Continuous-flow column leaching and accelerated wet–dry (W–D) aging experiments demonstrated that H-BC substantially suppressed the mobility of operationally filtered Cr(VI), achieving a maximum filtered-Cr(VI)-based retention efficiency of 99.98% under cyclic drying–rewetting conditions. Spatial configuration analysis indicated that homogeneous incorporation of H-BC improved soil–biochar contact and was more effective than stratified placement in limiting vertical filtered-Cr(VI) migration. Overall, oxidatively functionalized H-BC shows promise as a biomass-derived amendment for reducing Cr(VI) mobility in complex environmental matrices, although complete chromium mass redistribution will require future total-Cr and Cr(III)-resolved analyses. Full article

For soil processes that are known to be temporally dynamic, such as soil respiration, methanogenesis, and nitrification–denitrification, it is challenging to capture temporal variations with field-portable greenhouse gas (GHG) analyzers to provide the most accurate estimates of season-long GHG emissions and global warming potentials (GWPs). The objective of this field study was to evaluate the effects of measurement frequency (i.e., weekly, every other week, and every third week), replication (i.e., three, four, or five), and their interaction on the consistency of season-long carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) emissions and GWP estimates across multiple ecosystems. Results are based on direct, in-field measurements with a field-portable gas analyzer. Field research was conducted throughout the 2024 growing season in a minimally grazed pasture, tallgrass prairie, soybean under conventional and conservation management practices, and cotton under conservation management in Arkansas, USA. Season-long CO₂ emissions and GWP from the tallgrass prairie were 1.1 times (12%) greater from the weekly and every-other-week (16.9 and 17.0 Mg ha⁻¹, respectively), which did not differ, than the every-third-week (14.2 and 14.2 Mg ha⁻¹, respectively) measurement frequencies. Season-long CH₄ emissions from the minimally grazed pasture and conservation-tilled soybean system were ≥7.5 times greater with four and five replications, which did not differ, than with three replications. Global warming potential in the conservation-tilled soybean (13.9 Mg ha⁻¹) and conservation-tilled cotton (21.1 Mg ha⁻¹) systems were ≥1.1 times (13%) greater with the every-third-week than with the weekly data set. Though this study was somewhat limited due the data sub-setting approach used, even using current, state-of-the-art, field-portable GHG analyzers, an appropriate in-field measurement frequency and number of spatial replications should be considered to reliably quantify whole-field, season-long GHG emissions and GWP estimates. Full article

White-nose syndrome (WNS), caused by the psychrophilic fungus Pseudogymnoascus destructans, poses a severe threat to wild bat populations. Caves serve as unique microecosystems. Exploring antagonistic microorganisms and their volatile antifungal compounds within these native environments has emerged as a promising ecological control strategy. In this study, we isolated four antagonistic bacterial strains from bat cave soil that completely inhibit P. destructans. Additionally, we identified benzaldehyde (BzH) and 2,5-dimethylpyrazine (2,5-DMP) as their primary antifungal volatile organic compounds (VOCs). Combined physiological, biochemical, and multi-omics analyses revealed that these two VOCs disrupt the structural integrity of the fungal cell wall and membrane. This disruption triggers abnormal energy metabolism and compensatory ATP accumulation, leading to a significant intracellular burst of reactive oxygen species and the impairment of primary antioxidant defenses. This sustained oxidative stress causes irreversible DNA damage, endoplasmic reticulum stress, and basal metabolic dysfunction. Consequently, this cascade induces apoptosis and significantly downregulates the expression of essential virulence genes. In conclusion, this study systematically elucidates the molecular network through which VOCs released by cave soil microorganisms antagonize P. destructans. These findings provide a theoretical foundation and candidate intervention molecules for the contactless biocontrol of WNS. Full article

Magnesium (Mg) deficiency is common in acidic orchard soils and can limit fruit crop growth and quality. This study evaluated whether foliar-applied magnesium oxide nanoparticles (MgO NPs) could improve Mg nutrition and fruit quality in ‘Ninghaibai’ loquat grown under Mg-deficient acidic soil conditions. Pot and field experiments were conducted using water as the control and MgSO₄-50eq as an equimolar Mg comparator. MgO NPs showed a concentration-dependent effect, and 200 mg/L produced the best overall performance among the tested concentrations. At this concentration, total biomass increased by 47.27%, compared with CK, accompanied by enhanced chlorophyll accumulation, antioxidant enzyme activities, and Mg uptake. In fruit, 200 mg/L MgO NPs increased soluble solids content by 45.67% and reduced titratable acidity by 53.26%, while also improving fruit size and sugar–acid balance. Leaf transcriptome analysis suggested that MgO NPs altered the expression of genes involved in metabolism, stress response, and secondary metabolite biosynthesis. At the 50 mg/L level, MgO NPs produced stronger responses than the equimolar MgSO₄ treatment in Mg uptake, nutrient acquisition, and several fruit-quality traits. However, excessive application at 500 mg/L weakened growth and quality improvement. Overall, foliar application of 200 mg/L MgO NPs may represent a promising strategy for improving loquat growth and fruit quality under the tested Mg-deficient conditions. Full article

Understory mosses modify near-surface soil conditions, but how elevation regulates their influence on active and mineral-associated soil organic carbon (SOC) remains unclear. We compared independently selected moss-covered and non-moss-covered soils across a 3200–3500 m elevational gradient and integrated soil physicochemical measurements, microbial biomass (MB), dissolved organic matter (DOM), microbial necromass carbon (MNC), particulate organic carbon (POC), mineral-associated organic carbon (MAOC), metagenomic profiling, and piecewise structural equation modeling. Moss-covered soils consistently contained higher SOC and MAOC, but lower DOM, MB, and generally lower POC, than non-moss-covered soils. MNC showed an elevation-dependent reversal, with higher values under moss cover at 3200 m but lower values under moss cover at 3300–3500 m. Elevation was not a significant uniform driver of MB, DOM, MNC, POC, or MAOC; instead, its influence was mainly reflected in interactions with surface cover and in elevation-related changes in moss-layer structure, diversity, and hydrothermal conditions. Core carbon-fixation and degradation functions remained broadly stable, whereas specific functional modules shifted within moss-covered soils: acetate and acetyl-CoA metabolism genes (ackA and abfD) were relatively abundant at 3300–3400 m, while the polysaccharide-reprocessing gene SGA1 and oxidative-transformation gene katG increased toward higher elevations, and pmoC/amoC rebounded at 3500 m. Structural equation models linked the microbial functional gene system more strongly to POC, whereas MNC was positively associated with MAOC, and the direct POC-to-MAOC pathway was not significant. These findings indicate that moss cover is associated with contrasting SOC allocation patterns and stronger microbial necromass–MAOC coupling, while elevation modulates these relationships indirectly through changes in moss communities, soil microenvironment, and microbial functional potential. Full article

Ionic liquids (ILs) are widely used chemical compounds that may pose potential risks to the environment. In the present study, the effects of 1-ethyl-3-methylimidazolium chloride (EMIMCl) on growth, photosynthetic performance, and oxidative stress in maize (Zea mays L.) seedlings were evaluated, and the role of exogenous L-ascorbic acid (AsA) in modulating plant responses to this stress was investigated. Plants were cultivated in soil contaminated with EMIMCl at concentrations ranging from 1 to 1000 mg·kg⁻¹ of soil dry weight (DW) and treated with AsA at concentrations of 0.5–2 mM. EMIMCl significantly inhibited plant growth, reduced photosynthetic pigment content, and impaired chlorophyll fluorescence parameters, accompanied by increased hydrogen peroxide (H₂O₂) and malondialdehyde equivalents (MDA) levels, indicating the induction of oxidative stress. Moderate doses of AsA partially alleviated EMIMCl-induced toxicity, whereas higher AsA concentrations under severe EMIMCl contamination intensified stress symptoms. These findings demonstrate a dose-dependent and biphasic role of AsA in maize responses to EMIMCl-induced stress. Full article

In soils, mercury is found bound to organic matter, clays, and iron/manganese oxides, which are also major constituents of archaeological pottery. Although pottery is the most researched cultural material with archaeometric techniques, its mercury content remains largely unexplored. To address this gap, we studied Late Neolithic Penha-type pottery from NW Spain. The Late Neolithic was a period of widespread exploitation and circulation of mercury-bearing resources. A total of 92 samples from five archaeological sites were analysed to determine their mercury, carbon, sulfur, and iron content, as well as their spectroscopic properties (FTIR-ATR). Mercury was detected in all samples, with concentrations ranging from 6 to 1086 ng g⁻¹. Neither organic matter (C and S) nor iron compounds (Fe) were found to explain Hg concentrations, suggesting that diagenetic mercury incorporation was unlikely. Mercury was found to be related to kaolinite structural transformations, with concentrations decreasing with increasing degree of transformation. Kaolinite transformation depended on firing conditions (temperature and time), pointing to thermal desorption of the mercury present in the clay. The large observed variability most probably resulted from poorly controlled firing conditions. Nevertheless, whether mercury content reflects unintentional incorporation from naturally mercury-rich raw materials or a deliberate selection or addition (e.g., of cinnabar) during pottery manufacture remains to be further explored. Full article

Soil salinization represents one of the most severe abiotic constraints on global forest productivity. Populus, the most widely cultivated fast-growing timber tree and a premier model woody plant, exhibits striking intrageneric variation in salt tolerance—from the extremely halophytic Populus euphratica to highly salt-sensitive cultivated clones. Understanding the molecular basis of this variation has profound implications for saline–alkali land reclamation and salt-tolerant variety breeding. This review systematically synthesizes current knowledge on Populus salt-stress responses, covering three primary injury mechanisms (osmotic stress, ionic toxicity, and oxidative damage) and the corresponding physiological countermeasures. We further survey functional genes across four major categories: ion transporters, osmotic-adjustment enzymes, antioxidant-defense components, and transcription factors. Crucially, we extend beyond the herbaceous-plant paradigm by examining salt-tolerance strategies that are specific to the woody architecture of Populus: long-distance radial and axial Na⁺ transport through tall stems, salt sequestration in senescent bark and wood parenchyma, and deep-root ion exclusion strategies. Comparative insights from other woody genera are incorporated to highlight convergent and divergent mechanisms. On this basis, we propose an integrated multi-level regulatory model in which Na⁺ compartmentalization/efflux serves as the core, ROS homeostasis as the key regulatory axis, and osmotic adjustment as the auxiliary strategy. Outstanding challenges—including unresolved primary salt-signal perception, insufficient pathway integration, and limited in planta gene-function verification—are critically assessed, and future research priorities encompassing multi-omics integration, CRISPR-based gene editing, and natural-population genomics are outlined. Full article

Agricultural karst watersheds are highly vulnerable to nutrient loss because strong surface water–groundwater (SW–GW) connectivity can rapidly transfer nitrogen and sulfur species from soils, agricultural activities, and human settlements into aquatic systems. However, the coupled behavior and contrasting controls of nitrate (NO₃⁻) and sulfate (SO₄²⁻) in such agroecosystems remain insufficiently understood, limiting effective nutrient and groundwater-quality management. In this study, a typical karst agricultural watershed in Southwest China was selected to investigate the sources, transformation processes, and transport pathways of NO₃⁻ and SO₄²⁻ under strong SW–GW interactions. During the rainy season, 44 groundwater and 40 surface water samples were collected for major hydrochemical and nitrate–sulfate stable isotope analyses. An integrated framework combining hydrochemical analysis, self-organizing maps (SOM), positive matrix factorization (PMF), and MixSIAR were used to identify dominant sources, quantify source contributions, and clarify controlling processes. The results showed that groundwater was mainly characterized by carbonate-controlled Ca-HCO₃ facies, whereas surface water exhibited higher mineralization and a shift toward Ca-SO₄ facies, indicating stronger external inputs and rapid hydrological responses. Nitrate was primarily controlled by external nitrogen inputs, with manure and sewage and soil nitrogen contributing 39–62% and 16–33%, respectively. Nitrate was also regulated by nitrification under oxic conditions, while denitrification was negligible. In contrast, sulfate was predominantly governed by geogenic processes, with sulfide oxidation contributing 63–83%, while other sources were minor. These contrasting controls resulted in distinct spatial and process behaviors: nitrate showed source-driven variability associated with agricultural and domestic inputs, whereas sulfate displayed process-driven accumulation mainly controlled by water–rock interactions. Strong SW–GW connectivity enhanced the transfer of anthropogenic nutrient signals, while subsurface mixing and buffering regulated their expression in groundwater and surface water. These findings demonstrate a clear decoupling between nitrate and sulfate controls in agricultural karst systems and provide a scientific basis for nutrient pollution control, groundwater protection, and sustainable agricultural water management in vulnerable karst regions. Full article

Calcium alginate is an anionic polysaccharide that forms an ionically crosslinked hydrogel network with encapsulation properties to nucleic acids and nutrients for the amelioration of osmotic stress, ion toxicity and nutrient imbalance in saline–alkali soils. Traditional soil reclamation methods, including salt leaching, incorporation of organic matter, and gypsum application, are water-intensive under a changing climate, ultimately necessitating transformative bio-based solutions for food security. Calcium alginate-based biohydrogel represents a versatile platform with a tunable macromolecular architecture, ionic crosslinking via an “egg box” mechanism and potentially promising to deliver engineered co-encapsulated nutrients and genetically modified cargoes. The mannuronic (M) and guluronic (G) acid (M/G) ratios govern ion exchange capacity, rheological behavior and release kinetics in saline- and alkali-stressed environments. Recent studies on alginate-based nutrient encapsulation showed reduced oxidative damage and a 15–50% increase in plant-available water. The irrigation intervals extended from 7 to 14 days and yield gains by 24% in wheat, with comparable improvements in maize, tomato, rice and cotton. Calcium alginate hydrogels encapsulated salt tolerance genes (HKT1, SOS1, AVP1) encoding proteins mainly involved in Na⁺ retrieval from xylem, Na⁺ extrusion from root cells and vacuolar Na⁺ sequestration, which have achieved yield gains of 40 to 75% across wheat, rice and maize. Future research should focus on optimizing mechanical strength, crosslinking chemistry and smart bioencapsulation strategies for sustainable development so that crops are capable of withstanding variable climate stresses. Full article

Cadmium (Cd) contamination in agricultural soils poses a severe threat to food safety and human health through the food chain. This study investigated the efficacy of tobacco straw-derived biochar, applied at varying rates (0%, 1%, 2%, and 5% w/w), in mitigating Cd accumulation and modulating the growth and nutritional quality of two amaranth (Amaranthus tricolor L.) cultivars (red and green) grown in Cd-contaminated soil (initial total Cd of 2.18 mg/kg). The pot experiment revealed that biochar significantly reduced Cd uptake in both cultivars. Mechanistically, biochar elevated soil pH and drove the in-situ transformation of highly bioavailable exchangeable Cd into the more stable Fe-Mn oxide-bound fraction. Consequently, shoot Cd concentrations were notably suppressed, with the red cultivar exhibiting a superior response; the 2% biochar treatment optimally reduced its shoot Cd concentration by 37.6% compared to the control. Crucially, the amendments induced highly cultivar-specific growth responses. While biochar application simultaneously mitigated Cd toxicity and promoted biomass accumulation in red amaranth (yielding a 58.6% increase in shoot dry weight at the 2% rate), it exerted antagonistic, inhibitory effects on the growth of green amaranth. In conclusion, the incorporation of 2% tobacco straw biochar serves as a highly effective, dual-purpose strategy for significantly reduced health risks and enhancing the yield of red amaranth in Cd-contaminated fields. However, in green amaranth, biochar application induced a physiological trade-off, inhibiting growth despite successful Cd reduction. Furthermore, while Cd concentrations were significantly reduced on a dry-weight basis, future evaluations based on fresh-weight regulatory limits are required to fully confirm food safety. Full article

With rapid urbanization, the generation of municipal solid waste is growing, placing ever-increasing pressure on cities to close, remediate and repurpose landfill sites in environmentally sustainable and climate-adaptive ways. Traditional landfill final covers such as compacted clay and geosynthetic systems are intended to limit infiltration; yet their conceptual designs often fail in performance longevity due to effects such as desiccation, settlement, root intrusion, freeze–thaw cycling and extreme rainfall. Phytocapping, or evapotranspiration/store-and-release cover technology is the use of vegetated soil profiles to provide storage for percolating rainfall, return water to the atmosphere through evapotranspiration and support biologically mediated oxidation of methane. Phytocapping is a green-inclusive nature-based climate adaptation strategy for urban landfill closure. This study explores hydrological performance, methane mitigation, ecological co-benefits, economic feasibility, climate sensitivity, monitoring requirements and regulatory barriers linked to phytocapping systems. Field evidence is strongest in Australia and the United States, especially through ACAP- and A-ACAP-style programs, while evidence from humid tropical, monsoon, freeze–thaw and low-resource urban contexts is comparatively lacking. As reported in published studies, well-designed phytocaps can result in reduced percolation compared to traditional clay caps. Reported publications also mention considerable construction-cost savings, depending on site conditions and design assumptions. Methane-related outcomes vary by measurement method and site context, with studies reporting surface flux reductions, methane oxidation and landfill gas attenuation as distinct performance indicators. These advantages are counter-balanced by design uncertainties that vary from site to site, limited long-term monitoring data, climate transferability concerns, and regulatory systems still firmly anchored in prescriptive low-permeability barriers. This review proposes a policy-oriented analytical framework that bridges the gap between technical performance evidence, urban co-benefits, staged monitoring and performance-based landfill closure regulation. As such, phytocapping should be considered not as a general-purpose substitute for engineered covers, but as a climate-responsive nature-based solution that can complement urban waste servicing infrastructure, ecological restoration and adaptive governance of landfills when properly designed, monitored and regulated. Full article