Environmental Earth Sciences最新文献

Construction of dams causes changes in the natural flow and sediment patterns of rivers, disrupting their ecosystems. This study aims to evaluate how two dams in Ardabil province affect river flow and sediment load indicators. Several indices, including mean annual flow/sediment load (A), flow/sediment load duration curve difference (M), flow/sediment load duration variability (Dv), and seasonal period (SP), were employed to evaluate the impact of regulatory dams on the monthly flow/sediment regime of the river. Results indicate similar monthly flow and sediment load values at the upstream and downstream stations of Yamchi dam, with a slight increase at the downstream station of Sabalan dam. Yamchi dam had a more substantial impact than Sabalan dam on flow and sediment load indices. Both dams exhibited high seasonal amplitude (SA), signifying significant flow and sediment load variability. The Yamchi dam had more effect on flow index changes, with a flow duration curve difference (M = 0.77). Additionally, the changes in sediment-related indices were greater at Polealmas compared to Doost Bigloo (0.98 vs. 0.8), indicating a reduced sediment-related impact during the study period. The monthly changes in flow and sediment load at the upstream and downstream stations of both dams followed the same pattern. The study emphasizes the different impacts of dams on the flow/sediment load regime of the river, implying varying ecological implications on the river ecosystem and riparian zones. The findings emphasize the importance of considering multiple indicators to comprehensively evaluate dam impacts on river dynamics and underscore the impacts on flow regime and river ecosystem.

This study presents a comparative analysis of horizontal and pipe drains in earth dams, focusing on optimizing seepage control and stability. Using the Kreireche dam in Algeria as a case study, we employed GeoSlope software (SEEP/W and SLOPE/W) to conduct numerical simulations across 20 different scenarios, varying drain configurations and hydraulic conditions. Results indicate that pipe drains significantly outperform horizontal drains in managing seepage and enhancing dam stability. Pipe drains with larger diameters (2 m) reduced pore pressure by 15–20% compared to horizontal drains, demonstrating superior seepage control. Optimal drain placement within the range of X/B = 0.2 to 0.4 led to maximum safety factors, highlighting the importance of drain positioning. Statistical analysis using RMS, MAE, and MSE metrics showed that pipe drains consistently provided more reliable seepage and exit gradient control compared to horizontal drains. Increasing pipe drain diameter from 1 m to 2 m improved discharge seepage prediction consistency, reducing normalized RMS and MAE by 18.5% and 17.3%, respectively. Pipe drains exhibited 64.2% lower normalized RMS values for exit gradient predictions compared to horizontal drains, indicating more effective erosion risk mitigation. This study provides important insights for enhancing drainage system design in earth dams, resulting in increased stability and long-term performance of these crucial water management structures.

Sands from the dune, berm, and shore environments at Playa las Golondrinas (18° 30′ 51″ N, 67° 3′ 26″) were investigated to explore how beach sands could be applied as a potential environmental (geogenic) background for the local region. Grain size is dominantly unimodal classifying as fine to medium sand. Hydraulic conductivity values range from 1.07 cm/s (berm) to 1.49 cm/s (shoreface). Sample mineralogy as constrained by X-ray diffraction (XRD) reveals a dominance of quartz and feldspar with minor Mg-calcite, pyroxene, and olivine. Light microscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM–EDS) support XRD data and indicate the presence of oxide-bearing lithic fragments in addition to biologic materials (e.g., corals. forams). Reflective spectra are consistent with XRD and microscopy. Bulk element concentrations determined using inductively coupled plasma—mass spectrometry (ICP-MS) are consistent with derivation from the arc-related rocks of Puerto Rico’s interior exhibiting LILE enrichment, Pb-enrichment, and associated Nb–Ta depletion. The majority of the bulk elemental concentrations are below those of average upper continental crust (UCC) values and element co-variation trends (e.g., wt. % Fe₂O₃ vs. As) are interpreted as geogenic in origin. Berm sands are enriched in Fe, Mn, Ni, Cr, V, and As compared to dune and shore samples and this signature is interpreted as being from a wind-driven winnowing effect. The exact form of As (As³⁺ or As⁵⁺) remains unconstrained and thus it is unknown if As is mobile in this environment. Reflective spectra, supported by grain size, mineralogy, and bulk chemistry, enables future remote sensing investigations by providing detailed constraints on sand in environmentally sensitive areas. This study therefore provides local context for metal pollution studies across the region.

In recent years, biopolymers have been widely used in soil, but few concentration on the application of biopolymers in the organic soil. In this work, the potential using locust bean gum for improving the physical characteristics of the organic soil has been fully evaluated, while the Atterberg limit test, unconfined compressive strength test, and unconsolidated undrained shear test were conducted. In addition, the mineral composition and micro-mechanisms have been analyzed by X-ray diffraction tests, Fourier transform infrared spectra tests, and scanning electron microscopy tests. And we found that locust bean gum could increase the liquid limit and plastic limit of the organic soil, and enchance the compressive strength and shear strength. The increase in soil cohesion with locust bean gum content was more pronounced than the increase in internal friction angle. And as the curing time progresses, locust bean gum gradually transformed from a hydrogel state to a high tensile strength biofilm or flocculent gel matrix, which enhanced the bonding force between soil particles, thus increasing the strength of the specimens, which can be validated by the scanning electron microscopy observations, in which the porosity of soil was significantly reduced. We believed that this work could provide an ecological, economical and practical insight dealing with the engineering project constructions in the organic soil area.

Landslide Susceptibility Zonation is an efficient technique decision-makers use for disaster mitigation in landslide-prone regions. This study proposes an alternate approach for LSZ mapping, aiming to mitigate the limitations of the subjective expert opinion-based methods presently employed by disaster management authorities in India. Consequently, a GIS-based ensemble of Frequency Ratio and Analytical Hierarchy Process is employed, which offers a more robust and objective evaluation of Landslide Susceptibility. A landslide inventory of 592 incidents is processed using the database maintained by the Geological Survey of India, the national nodal agency for landslide studies. Then, LSZ mapping is conducted for a selected region in the Indian Himalayas using the processed inventory and nine causative factors (Elevation, Slope, Aspect, Curvature, Terrain Ruggedness Index (TRI), Distance to drainage, Land Use/Land Cover (LULC), Geology, and Lithology) as input. The generated LSZ map is evaluated using separate subsets of the inventory, yielding accuracies of 74.13% and 75.08%, respectively, during the training and testing stages. The study's findings hold potential implications for more effective disaster mitigation strategies and early warning systems in landslide-prone regions.

Rivers play a crucial role in landscape evolution and human development, especially in arid zones, where hydrological resources are scarce and in high demand. The Atacama Desert is one of the world’s oldest and driest non-polar deserts, and aquatic systems therein have been historically subjected to anthropogenic pressure mainly associated with natural resource exploitation, such as water consumption for industrial mining activities. The mining industry has experienced a systematic development since the early 20th century, making Chile one of the main worldwide copper producers. This study analyzed sediments from two Atacama Desert rivers, the Loa and Salado Rivers (Antofagasta Region, Northern Chile). Sedimentary short-cores were obtained from sampled locations at varying distances from the confluence of the rivers. The characterization of chemical components, grain size, mineralogy, and magnetic properties of the rivers’ sediments was assessed in surface and subsurface samples to determine their respective signatures in the Inka-Coya Lake near the rivers’ confluence. The magnetic mineralogy present in the sediments of both rivers is composed of detrital magnetite and maghemite interspersed with those of authigenic origin. However, the downstream Loa River concentrated more authigenic minerals than the Salado and increased the abundance of silt-sized particles. The grain size of the Loa’s channel bed suggests low stream competency and high formation of depositional habitats. The magnetic signal and mineralogical composition of sediments from the lake are dominated by detrital pyrite, magnetite, and authigenic greigite. In contrast, the river’s sediments were dominated by magnetite and maghemite of detrital origin intercalated with those of authigenic origin. The granulometry, mineralogy, and rock magnetic properties of Inka-Coya Lake sediments indicate recent detrital input alternating with authigenic mineral-rich layers, mainly reflecting shifts in hydrological regimes. The highest concentrations of copper were observed in the upper, more recent sediment layers. Future scenarios of risky climatic conditions associated with increasing global metal demands could modify the availability of potentially toxic elements and transport capability in fluvial sediments, increasing the threats to water resource conservation in the world’s most arid desert.

The dry–wet cycle will cause the deterioration of rock mass and grouting materials in the anchoring system, and then affect their strength and deformation, which has an important impact on the stability and durability of geotechnical engineering. In this paper, the damage and deterioration effects of sandstone-concrete composite samples under dry and wet cycle conditions are studied by using nuclear magnetic resonance technology, and the mechanism of anchoring system under dry and wet cycle conditions is revealed. The experimental results show that rock and concrete are damaged to different degrees under the action of wet and dry circulation. The micropore content of the whole sample increased and the medium and macro pores expand continuously during the dry–wet cycle action. The cracks development with the increase of number of dry–wet cycles intensify the damage of the sandstone-concrete connection surface. It can be observed that the damage of sandstone part is much lower than that of concrete part under the action of dry–wet cycle based on NMR image. The drawing process compresses the pores and enhances the plastic ability of CRC (concrete rock composite) sample, which explains the mechanical law that the drawing force of low-strength concrete increases gradually with the increase of the number of dry–wet cycles due to the increase of the internal pores of the CRC sample.

An environmental flow (e-flow) regime is designed to mitigate the effects of hydrological changes on rivers and to achieve good environmental status of a river as required by the Water Framework Directive (WFD). Once the components of an e-flow regime have been defined, it is important to verify that it meets its objectives, ideally through field sampling. However, field sampling is often avoided due to its high cost and time demands. This paper presents a methodology for validating a proposed river flow regime prior to implementation, allowing its suitability to be assessed without the costs and delays associated with monitoring and ecosystem response studies. The method includes a hydrological process that compares the official flow regime with the natural regime, and a hydraulic simulation process that tests the flow regime in terms of habitability for fauna. The method is tested on four reaches of the Tagus River, which have undergone significant hydrological alterations, using two different environmental flow regime proposals: one official and the other proposed by the authors. The results show a significant reduction in the annual inflows under the official e-flow regime compared to the natural ones (about 25% of the natural total), as well as a simplification of the seasonal flow variation in all river reaches. In addition, the study shows that at the minimum flows proposed in the official regime, three of the stretches would experience conditions that may impede fish migration. This method of inspecting e-flows can be useful for testing mitigation measures for hydrological changes in the very early stages of their application.

Groundwater is vital for meeting water demands in India, especially for agriculture, but faces stress from industrialization, urbanization, and climate change. Sustainable management, including understanding aquifers and recharge zones like palaeochannels, is essential to ensure long-term groundwater availability. The present research explored the applications of surface geophysical Dar-Zarrouk (D–Z) parameters, estimated from Vertical Electrical Sounding (VES) surveys conducted at seventeen locations, to assess hydrogeological conditions and correlate the findings with the identified palaeochannels within the alluvial area of Saraswati Nagar block of district Yamuna Nagar, Haryana, India. Further, as the study area is occupied with fresh groundwater, the estimated D–Z parameters including Transverse Resistance ((T)) and Longitudinal Conductance ((S)) values should be relatively on the higher side in comparison to the saline groundwater-occupied areas. In the study area, (S) values vary between 0.2025 (Sahabpur) and 2.49 (Talakaur) mho with an average value of 0.9364 mho, and (T) values vary between 922.96 (Bhamboli) and 5505 (Kabulpur) Ωm² with an average value of 3000.75 Ωm² respectively. The results of the electrical resistivity survey have been used for estimating the hydraulic conductivity ((K)) and transmissivity ((t)). Hydraulic parameters such as hydraulic conductivity and transmissivity are pivotal in evaluating and controlling groundwater resources. The findings highlight the valuable insights gained for groundwater resource management. This type of study has not been attempted before by any researcher in this regions hence, it will greatly help in understanding the groundwater regime in the area.