Search Results (225)

The use of aeolian sand as a fine aggregate in concrete production provides a sustainable pathway to valorize abundant aeolian resources while alleviating the global shortage of natural construction aggregates. However, the high ultrafine particle content of aeolian sand results in the formation of highly porous interfacial transition zones (ITZ) between sand particles and cement paste, which is the primary cause of the inherent brittleness and inferior mechanical performance of aeolian sand concrete. To overcome this critical limitation, an alkali-activated surface layer (ASL) was constructed on aeolian sand via 4 mol/L KOH activation. This process induced the surface micro-dissolution of minerals to create high-density active ion sites (specifically Ca²⁺, K⁺, Na⁺, and Fe³⁺). These sites facilitated the precise anchoring of carbon nanotubes (CNTs) through the chemical coordination of single-stranded deoxyribonucleic acid (ssDNA). The influence of the ASL and the ssDNA/CNTs nanocomposite on the ITZ was elucidated through macro-mechanical testing and multi-scale microstructural characterization. Experimental results demonstrated that compressive strength, flexural strength, and compressive energy dissipation increased by 48%, 67%, and 42%, respectively. Microstructurally, the modification promoted a pore refinement mechanism, reducing the proportion of harmful (pores > 0.1 μm) from 51% to 20% and narrowing the ITZ width from 20–40 μm to 10–15 μm (a 67% reduction). The observed performance enhancement is attributed to the synergistic effect of the ASL and ssDNA/CNTs, which transforms the inherently weak ITZ into a chemically reinforced interfacial phase via molecular-scale coordination bonding and optimized stacking of cement hydration products. Full article

The 1964 M7.5 Niigata earthquake remains one of the most significant natural laboratories for understanding seismic–induced soil liquefaction and its dependence on geological setting. Among global field case histories, Niigata stands out for the exceptional documentation of liquefaction triggering, lateral spread displacements, and soil–structure interaction. This paper reexamines the event from an engineering–geologic perspective, emphasizing how Holocene coastal and fluvial depositional processes beneath the Echigo Plain controlled the spatial and stratigraphic distribution of liquefaction during the 1964 earthquake. The most severe ground deformations occurred in fluvially reworked sands derived from three major Holocene dune and barrier island systems (CSD1,2,3) formed along the paleo–shoreline of the Sea of Japan. The largest of these, a mid–Holocene transgressive barrier complex deposited to a thickness of 50–60 m of beach and aeolian sand between 8 and 5 ka B.P., now lies buried 5–8 km inland beneath fine–grained alluvial deposits. Tectonic downwarping and deltaic progradation by the Shinano and Agano rivers redistributed these sands into loose, saturated fluvial facies beneath modern Niigata city. Quantitative geotechnical analyses demonstrate that liquefaction occurs within these reworked Holocene units rather than anthropogenic fills. Full article

As the new energy strategy progresses, desert, Gobi, and wasteland areas have become key areas for photovoltaic (PV) development, inevitably bringing new environmental challenges. Although PV power stations act as obstacles with some wind and sand control effects, aeolian erosion remains a problem, especially in localized areas where erosion intensifies. To address this issue, this study uses the PV power station layout in the semi-arid wind and sand region of Yudaokou, Hebei, as a case study. Using computational fluid dynamics (CFD) numerical simulations, a combined layout of PV panels and sand barriers is proposed. It is first assumed that this combined layout improves wind protection compared to photovoltaic arrays. The impact of different sand barrier configurations on the airflow field is analyzed to explore their role in controlling aeolian erosion. By analyzing the airflow field, areas of intensified and potentially intensified aeolian erosion are identified. Based on this, sand barriers are strategically placed in key protective zones on the windward side of the PV array, and the combined layout of PV panels and sand barriers is optimized to improve aeolian erosion control effectiveness and promote the sustainable development of PV power stations. The results indicate that PV panels significantly reduce wind speed by altering local airflow and flow patterns, with the impact primarily concentrated in the first 3 to 4 rows on the windward side of the PV array. By establishing sand barriers beneath the PV panels on the windward side, aeolian erosion can be effectively reduced, with the effect on the airflow field primarily occurring within the 0–0.3 m height above the ground. Continuously establishing sand barriers up to the third row of PV panels effectively reduces wind speed, with further extension not significantly improving wind protection, indicating that the third row of PV panels serves as the critical point for sand barrier establishment. This configuration provides the ideal layout for achieving effective protection and offers theoretical and practical guidance for improving the layout of combined PV power stations. Comprehensive analysis suggests that the optimized configuration of PV arrays and sand barrier layout effectively controls aeolian erosion, with the Model 3, which places sand barriers up to the third row of PV panels, ensuring efficient resource utilization. This study offers a practical approach to reducing damage from wind and sand by optimizing the layout of sand barriers and PV panels, thereby providing important guidance for the sustainable development of PV power stations in arid areas. Full article

Aeolian sand hazards severely constrain highway safety and operation in arid regions. To support targeted mitigation along Highway S315 in the Gobi Desert of northern China, this study integrates meteorological observations with sand removal records to quantify wind regimes and classify sand hazard intensity. Event thresholds were objectively identified using change points in semi-logarithmic distributions of daily sand removal volumes, and spatial hazard severity was graded based on annual sand removal per unit road length. The results showed that (1) the study area was subject to intense aeolian activity, with a mean annual sand-driving wind frequency of 23.98%, an annual drift potential of 344.91 vector units (VU), and a resultant sand transport direction of 129.88° (east–southeast). (2) Based on inflection point characteristics, sand hazard events were classified into three intensity levels, namely, slight (<800 m³), moderate (800–3000 m³), and severe (>3000 m³), accounting for 13.0%, 76.1%, and 10.9% of all events along Highway S315, respectively. (3) Spatial grading criteria for sand hazard severity were defined as slight (<3 × 10³ m³ km⁻¹ yr⁻¹), moderate (3 × 10³–1.0 × 10⁴ m³ km⁻¹ yr⁻¹), and severe (>1.0 × 10⁴ m³ km⁻¹ yr⁻¹). Application of these criteria to a representative road section (K9+000–K30+600; 21.6 km) indicated that severe, moderate, and slight sand hazard segments extend over 6.0 km, 9.1 km, and 6.5 km, respectively, thereby delineating priority zones for targeted mitigation measures. This study proposes a quantitative framework that couples regional wind-driven sand dynamics with highway hazard severity, enabling targeted mitigation and offering a transferable reference for sand risk management in arid and desert regions. Full article

Aeolian sand is abundant in arid deserts, but its high replacement in cement-stabilized bases can reduce strength and raise cracking risk. Strain localization and crack evolution are also poorly quantified. This study aimed to optimize the early age performance of cement-fly ash stabilized aeolian sand gravel (CFSAG) and clarify its failure mechanism. A Box–Behnken response surface methodology varied the cement content, cement-to-fly ash ratio, coarse aggregate gradation, and aeolian sand content. The 7-d unconfined compressive strength (UCS) and splitting tensile strength (STS) were tested. Digital image correlation (DIC) recorded full-field strains and crack metrics in compression and splitting. SEM–EDS was used to interpret microstructural changes. The aeolian sand content dominated UCS, whereas the cement content and cement-to-fly ash ratio mainly controlled STS. Factor interactions were non-negligible and supported the joint optimization of the two strength indices. DIC identified a crack propagation threshold near 0.9 P_max in splitting. Excess aeolian sand (>50%) caused earlier localization, more cracks, and wider openings. In the appropriate amount of aeolian sand mixtures, hydration products filled voids and improved paste continuity. SEM–EDS indicated that excessive fines increased porosity and weakened the interfacial transition zone. Overall, the combined RSM–DIC–SEM approach links mix design with deformation and microstructure evidence. It provides practical guidance to balance strength and cracking resistance at early ages for cement-stabilized bases in desert highway engineering. Full article

The ancient city of Gela (built in the 7th century BCE) is located in the southern sector of the Sicily Island (Southern Italy) on a Pleistocene marine terrace near the mouth of the Gela River. Gela was one of the most important Greek colonies in the Mediterranean Sea, strategically positioned at the crossroads of the major maritime trade routes and with a rich production of cereals thanks to the fertile Gela River alluvial plain. To reconstruct the coastal and environmental configuration during the Greek period and to improve the understanding of the location of the harbour basin, a multidisciplinary approach was applied to a sector of the Gela River alluvial–coastal plain. This area, located very close to the ancient city, is known as Conca (Italian for “Basin”) and was identified through the analysis of historical and modern maps as well as aerial photographs. The multidisciplinary approach includes geomorphology (derived from maps and aerial photos), stratigraphy (boreholes and archeological trench), paleoecology (ostracoda, foraminifera and fossil contents of selected layers), geochronology (¹⁴C dating of selected organic materials) and archeology (historical sources and maps, pottery fragments extracted from boreholes and trench layers). The main results show that this area was occupied by lower shoreface environments in the time intervals between 4.4 and 2.8 ka, which progressively transitioned to upper shoreface environments until the Greek age. During the Roman period, these environments were significantly reduced due to repeated alluvial sedimentation of the Gela River transforming the area into fluvial–marshy environments. A time interval of aeolian sand deposition was recorded in the upper part of the coastal stratigraphical succession, which can be related to climatic conditions with high aridity. Available data show that marine environments persisted in the Conca sector during the Greek age, allowing hypothesizing the presence of an ancient harbour in this area. The depth of the Greek age marine environments is estimated to be between 4.5 and 7 m below the current ground level. Further investigation, mainly based on geophysical and stratigraphical methods, will be planned aimed at identifying the presence of buried archeological targets. Full article

Understanding the community assembly mechanisms and stability of artificial sand-fixing forests is critical for the management of desert ecosystems. This study investigated the understory vegetation of four artificial sand-fixing shrub forests in the Mu Us Sandy Land to understand community assembly mechanisms and stability by analyzing niche characteristics, interspecific associations, and community stability. The results showed the following: (1) Lc (Leymus chinensis), Ee (Euphorbia esula), Gd (Grubovia dasyphylla), and Ch (Corispermum hyssopifolium) all have wide ecological niches and high importance values, serving as key species for maintaining community function. (2) The understory herbaceous plant communities of S. psammophila, A. ordosica and C. fruticosum exhibited low niche overlap, and the A. fruticosa understory herbaceous plant community showed high niche overlap. (3) The overall association of the understory herbaceous plant communities of S. psammophila, A. ordosica, and C. fruticosum is positive, while that of the understory herbaceous plant community of A. fruticosa is negative; the interspecific associations are weak, and the species show an independent distribution pattern. (4) Among the four understory herbaceous plant communities, the stability of the S. psammophila understory herbaceous plant community is relatively the highest, followed by A. ordosica and C. fruticosum understory herbaceous plant community, and the stability of A. fruticosa understory herbaceous plant community is the lowest. Furthermore, community stability was positively correlated with the variance ratio (VR) but negatively correlated with mean niche overlap. We recommend prioritizing S. psammophila and C. fruticosum for sand fixation and conserving key herbaceous species to optimize resource use and stabilize interspecific relationships. The novelty of this study lies in its integrated assessment of niche characteristics, interspecific associations, and community stability, and it primarily focused on the role of interspecific relationships. Future research should incorporate environmental drivers and shrub functional traits to disentangle the synergistic effects of biotic and abiotic factors, thereby providing a more robust scientific foundation for vegetation restoration in desert ecosystems. Full article

Aeolian sand in arid mining regions is highly susceptible to wind erosion, posing serious threats to ecological stability and surface engineering safety. To enhance its resistance, this study applied the microbially induced carbonate precipitation (MICP) technique and conducted wind tunnel experiments combined with SEM and XRD analyses to examine the effects of cementing solution type and concentration, bacteria-to-cementation-solution ratio (B/C ratio), and spraying volume on the wind erosion behavior of MICP-treated aeolian sand. Results show that the cementing solution type and concentration jointly control erosion resistance. The MgO-based system exhibited the best performance at a B/C ratio of 1:2, reducing erosion loss by 47.2% compared with the CaCl₂ system, while a 1.0 mol/L concentration further decreased loss by 97.4% relative to 0.5 mol/L. Increasing the spraying volume from 0.6 to 1.2 L/m² reduced erosion loss by 70–99%, and a moderate B/C ratio (1:2) ensured balanced microbial activity and uniform CaCO₃ deposition. Microstructural observations confirmed that MICP strengthened the sand through CaCO₃ crystal attachment, pore filling, and interparticle bridging, forming a dense surface crust with enhanced integrity. From a symmetry perspective, the microbially induced mineralization process promotes a more symmetric and spatially uniform distribution of carbonate precipitates at particle contacts and within pore networks. This symmetry-enhanced microstructural organization plays a key role in improving the macroscopic stability and wind erosion resistance of aeolian sand. Overall, MICP improved wind erosion resistance through a coupled biological induction–chemical precipitation–structural reconstruction mechanism, providing a sustainable approach for eco-friendly sand stabilization and wind erosion control in arid mining regions. Full article

Coastal sand dunes, shaped by aeolian and marine processes, are critical to natural ecosystems and human societies, making their morphological monitoring essential for effective conservation. However, large-scale, high-precision monitoring of topographic change remains a persistent challenge, a challenge that advanced sensing technologies can address. In this study, we propose an integrated, sensor-based approach using a UAV-mounted light detection and ranging (LiDAR) system, combined with a GNSS-RTK positioning unit and a novel ground control point (GCP) design to acquire high-resolution topographic data. Field surveys were conducted at four time points between October 2022 and February 2023 in the Tottori Sand Dunes, Japan. The digital elevation models (DEMs) derived from LiDAR point clouds achieved centimeter-level accuracy, enabling reliable detection of subtle topographic changes. Analysis of DEM differencing revealed that wind-driven sand deposition and erosion resulted in elevation changes of up to 0.4 m. These results validate the efficacy of the UAV-LiDAR sensor system for high-resolution, multitemporal monitoring of coastal sand dunes, highlighting its potential to advance the development of environmental sensing frameworks and support data-driven conservation strategies. Full article

The Metaponto coastal plain (Ionian margin, Southern Italy) records the Late Pleistocene–Holocene evolution of a foredeep coastal system shaped by relative sea-level change, vertical land motion, and compaction. We analyze a 22 m continuous core (Meta 1) using lithofacies logging, grain size statistics and cumulative curves, multivariate analysis of grain size distributions (PCA and k-means clustering), and three AMS 14C ages, and we compare the record with a nearby borehole (MSB) and a global eustatic curve. Four depositional units document a shift from lower-shoreface–offshore deposition to lagoon–barrier/aeolian systems, culminating in late Holocene near-surface progradation. Textural end members (mud-rich offshore/lagoonal, traction-dominated, and sand-rich) are coherent across classical parameters, Visher-type curves, PCA, and k-means clusters. Depth–age comparisons suggest net uplift during the Late Glacial, followed by near-present relative sea level and a Late Holocene onset of modest net subsidence; a compaction contribution is plausible but unquantified. Subsidence/uplift rates therefore remain upper-bound estimates owing to sparse chronological control and the lack of glacio-isostatic and compaction modeling. Together with the MSB emerged-beach tie-point, the record constrains shoreline position and progradation. The inferred Mid- to Late-Holocene stabilization and progradational trends are consistent with other Italian and wider Mediterranean coastal plains. Additional dating and quantitative paleoecological proxies (e.g., foraminifera/ostracods/molluscs) are key to independently constrain salinity and water-depth changes and to refine the partitioning between subsidence and compaction. Full article

The degradation of sandy land in Inner Mongolia presents a substantial threat to regional ecological security and the sustainable development of agriculture and animal husbandry. Planting alfalfa serves as a crucial recovery strategy; however, the inadequate capacity to retain water and nutrients impedes this process. The current reliance on a singular microbial remediation method has demonstrated limited effectiveness in addressing the challenges posed by sandy soil. While traditional sand-fixing agents can improve soil nutrients, they lack biological activity. Furthermore, the synergistic mechanisms between these approaches and their ecological impacts within a single season remain poorly understood. This study involved a pot experiment utilizing wind-sand soil as the substrate to evaluate the soil physicochemical properties, enzyme activities, and microbial community structure associated with the stress resistance of alfalfa. The results indicated that the medium concentration of sand-fixing agent (1:75) exhibited optimal water retention performance, thereby creating a conducive growth microenvironment for Trichoderma longibrachiatum and mitigating fluctuations in surface temperature and humidity. The combined treatment significantly improved the alpha diversity of soil microorganisms, thereby improving the stability and stress resistance of the system. Through the synergistic approach of “sand fixation and water retention–nutrient activation–improved stress resistance”, the microenvironment of sandy land was effectively improved, promoting alfalfa growth. This method offers “environmentally friendly and synergistic” technical support for the efficient cultivation and ecological restoration of alfalfa in sandy regions, while also contributing to the high-quality development of grassland animal husbandry. Full article

Aeolian sand slopes in the Fugu area of Yulin, Shaanxi Province, China, are prone to rainfall-induced erosion because of the loose structure and low water-holding capacity of the sand, which constrains long-term, sustainable ecological restoration. To address this, aeolian sand was amended with xanthan gum (XG) and a superabsorbent polymer (SAP) and combined with a honeycomb confinement system; evaporation, 70 mm·h⁻¹ rainfall–erosion, and direct shear tests were carried out. SAP increased the 24 h water content of untreated sand from 1.8% to about 20–22%, while excessive SAP led to surface cracking. XG strengthened interparticle bonding and reduced 60 min cumulative erosion from about 53 kg to <0.5 kg (reduction > 99%) and improved shear strength. Within the practically recommended range (XG 0.5–1.0%, SAP ≤ 0.25%), XG and SAP showed water-supply-improving and surface-strengthening effects that effectively covered the early-stage vegetation protection gap, i.e., the period before vegetation becomes dense enough to resist raindrop impact and runoff erosion. The results provide laboratory support for sustainable, nature-based stabilization of aeolian sand slopes in semi-arid engineering areas. Full article

Against the backdrop of China’s Western Development Strategy, numerous infrastructure projects are being constructed in desert regions. Utilizing local aeolian sand (AS) as a raw material for concrete production offers significant cost-saving potential but is hindered by challenges such as limited applicability and inadequate mechanical strength of the resulting concrete. To address these limitations, aeolian sand was ground into aeolian sand powder (ASP) and subjected to treatment with single alkali activators (NaOH, Na₂SiO₃) and a composite alkali activator (NaOH + Na₂SiO₃). The treated and untreated ASP was then used to replace 50% of cement by mass for the preparation of aeolian sand powder–aeolian sand concrete (ASPC). Mechanical performance tests and advanced characterization techniques (SEM, TG-DSC, XRD, FTIR, nanoindentation, and NMR) were employed to investigate the effects of different activators on the mechanical properties of ASPC and elucidate the underlying enhancement mechanisms. The results demonstrated that the composite activator outperformed its single-activator counterparts: ASPC-4-6 (incorporating 4% NaOH and 6% Na₂SiO₃) exhibited 16.3–23.1% higher compressive strength and 12.1–17.6% higher splitting tensile strength across all curing ages compared to plain ASPC. Under the influence of OH⁻ from the composite activator, ASP showed more pronounced reductions in potassium feldspar, montmorillonite, and SiO₂ content, accompanied by the formation of C-S-H gel—replacing the amorphous, water-absorbent N-A-S-H generated by single activators. The presence of highly polymerized hydration products and more stable potassium A-type zeolites in ASPC-4-6 led to a reduction in macropore volume, optimization of pore structure, and refinement of the aggregate–mortar inter-facial transition zone. These micro-structural improvements collectively contributed to the significant enhancement of mechanical properties. This study provides novel insights into the large-scale and multi-dimensional utilization of aeolian sand in concrete. Full article

Low-lying coastal plains are increasingly threatened by saltwater intrusion, yet the extent of the phenomenon and the role of coastal dune systems remain unevenly assessed. In the northern Adriatic Sea (NE Italy), salinisation has been documented, but systematic, spatially resolved studies are lacking. This work investigates the Belvedere–San Marco relict dune system to assess its hydrogeological function and vulnerability to seawater intrusion. An integrated methodology combining borehole and core stratigraphy, in situ water electrical conductivity (EC) measurements, and multi-method geophysical surveys (FDEM, ERT, GPR, active seismics) was tested. Results reveal a consistent stratigraphy of permeable aeolian sands overlying clay-rich units, with groundwater EC values in the dune sector always remaining well below thresholds for brackish or saline conditions. Geophysical imaging reveals that the dunes are low-conductive bodies contrasting sharply with the conductive surrounding lowlands, thus indicating the persistence of a freshwater lens sustained by local recharge within the dunes. The Belvedere–San Marco dunes therefore act as both freshwater reservoirs and natural hydraulic barriers, buffering shallow aquifers against salinisation. This study demonstrated the applicability of integrated geophysical methods to extensively investigate shallow phreatic aquifers lying a few metres below the surface, and establishes a baseline for monitoring future changes under rising sea levels, subsidence, and increased groundwater exploitation. Full article

A sedimentary profile consisting of blown sand capped by a sand-loam bedded interval was analysed in the Svätuše sand pit in the East Slovak Lowland. Stratigraphically, blown sands from this lowland have so far only been indirectly classified into the Weichselian glacial, mainly into its middle and upper stages. The age classification presented in this study results from the optically stimulated luminescence dating method. It identifies the blown sand from the Svätuše as originating during the Early Glacial and Early Pleniglacial phases of the Weichselian glacial (MIS 4–5d). At the end of the Early Glacial phase of the Weichselian glacial, palaeoenvironmental conditions changed. The deposition of blown sand became episodic rather than continuous. As a result, the analysed sedimentary record is composed of a sand-loam interbedded interval in the uppermost part. Full article