Environmental Earth Sciences最新文献

The safe geological disposal of high-level radioactive waste requires consideration of the inflow of groundwater from faults or fractures encountered during excavation of deep underground tunnels, as this inflow may adversely affect the installation and performance of bentonite buffers. The water pressure diffusion equation, assuming uniform hydraulic conductivity and specific storage, predicts that the inflow rate from faults or fractures naturally decays at a rate depending on the flow dimension when the cross-sectional area of the flow areas in the fault or fracture system is proportional to the power of the distance from the inflow point. Although this prediction has been verified for decay ratios measured a few weeks after tunnel excavation, its applicability to long-term predictions several years after excavation has not yet been assessed. We investigated the natural inflow decay ratios (i.e., the inverse of the current inflow rate normalized to the initial inflow rate at excavation) at fault-related inflow points in a tunnel at 350 m depth in the Horonobe Underground Research Laboratory, Japan, 10 years after tunnel excavation, and compared them with those modelled using the diffusion equation and flow dimension. The natural inflow decay ratio measured at each inflow point was equal to or higher than the modelled ratio. Although in some cases the measured ratios may be up to four times as high as the maximum modelled ratio, this difference can be explained by the effect of hydraulic interference between adjacent inflow points. The diffusion equation and flow dimension can be used to predict the minimum long-term (several years or longer) natural decay ratio, providing useful insight to implications for repository design timelines or regulatory decisions (e.g., determining when and where to install waste and bentonite buffers in a repository).

To clarify the spatial distribution of heavy metals and assess their potential health risks under the influence of seawater intrusion, 48 groundwater samples were collected from three confined aquifers in the coastal zone of Weifang, China. The concentrations of 13 heavy metals were analyzed. Spatial distribution patterns and inter-element correlations were assessed, and Cl^- was used as a proxy to explore the impact of seawater intrusion on heavy metal enrichment. Additionally, a quantitative health risk assessment was performed following USEPA guidelines. The results show that Fe and Mn concentrations exceed the standards. The distribution of heavy metals exhibits obvious stratigraphic and regional differences, with high spatial heterogeneity. The shallow aquifer is significantly influenced by anthropogenic pollution and seawater intrusion along paleochannel. The middle aquifer is the primary layer for heavy metal accumulation. The deep aquifer is more controlled by geological background conditions. Production activities have not caused large-scale vertical water quality exchange. Strong correlations were found between Cl^- and certain heavy metals (Cd, Mn, Co, V), suggesting that seawater intrusion may enhance the mobilization of specific contaminants. Health risk assessment indicates that ingestion is the primary exposure pathway, with adults facing higher health risks than children. The non-carcinogenic risk is mainly attributed to Mn, with Aquifer II showing higher risk, primarily in coastal region. The carcinogenic risk is mainly attributed to Cd and As, with Aquifer I showing higher risk. These findings provide a scientific basis for groundwater quality protection and pollution control in coastal aquifer systems.

The Bartın Kirazlı Bridge Dam construction has started on Gökırmak stream, western Black Sea Region, for the purposes of irrigation and power generation, and is continuing at present. By the end of construction, it is anticipated that the existing Bartın-Safranbolu Highway will be submerged underwater due to the increase in the Gökırmak stream level. With the start of construction of the new highway alignment for the relocation of the submerged road named as the “Bartın Kirazlı Bridge Dam Diversion”, the paleo-landslide regions alongside the new alignment have been triggered and led to mass movement along a segment of the new highway. This study aims to define the characteristics of this landslide, determine the sliding surface geometry and location, reveal the mobilized mass amount, and specify the appropriate remediation measures for long-term stability. For this purpose, geotechnical investigations and laboratory tests were conducted. With the data obtained from the engineering geological and geotechnical investigations, the landslide geometry and the shear strength parameters of the landslide mass were determined by back analysis. In addition, slope stability analysis was performed by limit equilibrium analyses for both static and dynamic conditions. As a result of these studies, groundwater level reduction by pumping in short-term, rock buttress application after temporary toe excavation and de-watering of the area by surface and subsurface drainage remediation phases were determined to be suitable for the long-term stability of the landslide.

To investigate the evolution pattern of the regional groundwater cycle in an energy base in arid and semiarid areas of northern China under the influences of complex tectonics and coal mining, water samples from different aquifers in typical areas were collected, and the water levels of the major aquifers were observed. Hydrogeological analysis, hydrochemical tests (pH, total dissolved solids (TDS), anions and cations), hydrogen and oxygen isotopes (δD, δ¹⁸O) and an end-member mixed model were used to quantitatively identify the hydraulic connection characteristics of the aquifers under mining disturbance. The results showed that the independence of hydrogeological units in the study area is controlled by large deep faults;δD, δ¹⁸O revealed that the groundwater originates from atmospheric precipitation; the deuterium-excess (d-excess) of the Ordovician limestone aquifer (8.8‰) is greater than that of the sandstone aquifer, and the isotope values of the mine drainage water are in between, confirming the mixing of sources. An end-member model showed that the contribution of Ordovician limestone water to the mine drainage water is 15.59%, and that of the No. 8 and 16 coal roof sandstone water is 84.41%, confirming that the Ordovician limestone aquifer recharges the coal-measure sandstone aquifer via hydraulic faults, and the water is drained by mining. This study elucidates the hydraulic connection evolution mechanism of "precipitation recharge–water conducted by tectonics–drainage due to mining" of karst groundwater in the study area and provides a quantitative basis for groundwater protection and mine drainage water disaster prevention and control in energy bases in arid areas.

This study addresses groundwater flow processes and hydrochemical evolution in the stratified hard rock terrain of the Seyabo and Feresmay River catchments, in Tigray, North Ethiopia. Geological, hydrogeological, hydrogeochemical, and isotopic methods were employed in this study. Hierarchical Cluster Analysis (HCA) classified the groundwater samples into two major groups and four subgroups based on ten parameters (EC, TDS, pH, Na⁺, Ca²⁺, Mg²⁺, K⁺, Cl⁻, HCO₃⁻, and SO₄²⁻). The two HCA groups contained TDS > 1000 mg/l and TDS < 1000 mg/l, shows different water-rock interactions and depths of circulation. The isotopic composition of the groundwater samples ranged from − 1.7‰ to + 7.2‰ for δ²H, and − 1.55‰ to + 0.18‰ for δ¹⁸O, indicating recharge from evaporated local precipitation. The high pH observed in the Na–Ca–HCO₃ water type with elevated EC reflects deep groundwater circulation within confined aquifers. Recharge from locally evaporated precipitation is progressively modified along the north–south flow path, with salinity increasing from Ca–Mg–HCO₃–SO₄ facies in the recharge zone to Ca–Na–SO₄–HCO₃ midstream and Na–Ca–HCO₃ downstream. This geochemical evolution, confirmed by inverse geochemical modeling, is driven by silicate weathering, cation exchange (Ca²⁺–Na⁺), and CO₂ dissolution–degassing, coupled with evaporation.

Regions with strong earthquakes and heavy rainfall are frequently affected by the coupling of seismic and rainfall effects, leading to frequent and highly destructive landslides that severely threaten regional safety. There is an urgent need for accurate landslide susceptibility assessment methods to support disaster prevention and mitigation efforts. Existing data-driven methods are limited by insufficient understanding of landslide mechanisms and reliance on historical data, while physical analysis methods mostly focus on single triggering conditions, making them unsuitable for complex coupled environments. To address these issues, this study proposes a Rainfall-Earthquake Model (REM), which integrates the seismic permanent displacement model and steady-state hydrological model, and incorporates vegetation's soil-reinforcing effect to enhance accuracy. The model does not require training with historical landslide data and enables rapid Landslide Susceptibility Prediction (LSP) immediately after an earthquake. Additionally, the MATLAB-based REM program supports direct import and efficient processing of TIF-format spatial data, with a single calculation taking only seconds, which is markedly more efficient than traditional methods. Validation using the Luding earthquake case shows that REM improves prediction accuracy by 13.706% compared to conventional methods. It accurately quantifies the synergistic impact of rainfall-earthquake coupling on slope stability and effectively identifies factor sensitivities. This research demonstrates that REM provides an efficient and practical tool for LSP in strong earthquake and heavy rainfall regions, playing a critical role in supporting disaster prevention planning and optimizing emergency decision-making.

The current research on CFG pile composite foundations primarily focuses on rigid foundations. However, there is a significant gap in the analysis of flexible foundations, particularly for specialized foundations such as tailings sand. This study investigates the behavior of CFG pile composite foundations under saturated tailings sand conditions through model testing. The results show that under vertical loading, settlement occurs rapidly, with the maximum settlement ranging between 5.98 mm and 6.12 mm after graded loading. Pore water pressure decreases with depth, with the shallow layer showing a reduction of 19–68% and the deeper layer exhibiting a reduction of 30–85%. The soil pressure is highest at the pile top, with increases ranging from 3.24 to 7.34%. These findings highlight the role of CFG piles in effectively distributing load and controlling settlement under both loading and drainage conditions, providing valuable data for engineering applications in tailings sand foundations.

In Japan, subsurface dams have been constructed to artificially recharge natural aquifers, which primarily comprise the strata of Quaternary Ryukyu limestone. The high porosity of the Ryukyu limestone makes it an excellent reservoir; however, its flow characteristics remain uncertain. In this study, we used X-ray computed tomography (CT) and pore-scale modeling to evaluate the pore and flow characteristics of the Ryukyu limestone samples. The CT results revealed a positive correlation between the porosity and connection probability (i.e., degree of connectivity between pores); the coefficient of variation of the porosity in the vertical direction tended to be smaller when the porosity of the entire region of interest was large. The pore-scale models showed that the flow was concentrated in a few channels (i.e., highly heterogeneous) and that the hydraulic conductivity and its anisotropy were highly dependent on the pore structure in the region of interest. These results enhance our understanding of pore structure and hydraulic behavior in Ryukyu limestone and provide a foundation for future assessments of groundwater flow and contaminant transport in subsurface dam reservoirs.