Pavement construction relies heavily on natural aggregates and conventional stabilizers such as Portland cement (PC) and lime, contributing to resource depletion, high energy demand, and significant greenhouse gas emissions. Geopolymerization, the alkaline activation of aluminosilicate materials, offers a more sustainable alternative. Mine tailings (MT), abundant mining by-products rich in silica and alumina, are attractive geopolymer precursors, although their reuse is constrained by variable composition and potential toxicity. In mining-intensive countries like South Africa, copper, cassiterite, and gold MT represent promising resources. This review critically synthesizes current knowledge on the physicochemical properties, mechanical performance, and environmental implications of geopolymerized MT in pavement applications. Unlike previous reviews that consider MT or geopolymers in isolation, it establishes a pavement-engineering–driven framework linking MT characteristics, geopolymer chemistry, and pavement performance requirements across laboratory, environmental, and field scales. The reviewed evidence indicates that MT-based geopolymers can achieve higher strength and superior durability than PC or lime-stabilized bases while reducing CO2 emissions by up to 80
TiO2 nanoparticles can exhibit benefits in various areas, including physics, chemistry, biology, the environment, and agriculture, among others, for the advancement of the world. In this research work, TiO2 nanomaterials are fabricated using a green synthesis technique called mechanical attrition and analysis of their properties for CO gas sensors. The structural study confirmed the stable tetragonal crystal structure for TiO2 samples, reducing the crystallinity and forming defects at higher milling times. The morphological analysis showed the transformation of larger grains (more than 1 μm) to nano-sized grains (around 100 nm) after 10 h of the milling process, verifying the formation of nanoparticles. The decrease in oxygen content (at.
Mangroves are vulnerable to rising sea levels and have shown two main mechanisms for adaptation: (1) vertical adjustments related to feedback between plant growth, inundation, and sediment deposition, and (2) horizontal movement to occupy adjacent ecosystems. In this study, the landward migration of mangroves on the Yucatán Peninsula (YP) was characterized for the period 1984–2024. A hybrid classification approach was used to construct coverage maps of mangroves, other vegetation types, and associated land uses. Overlay analysis revealed landward migration in four sub-regions. The total mangrove area identified with landward migration corresponded to 1754.38 ha, distributed in 79 polygons. The average area and distance of landward migration was 22 ha and 178.1 m, respectively. The average landward migration rate observed was 0.5 ha year−1, with an average landward migration speed of 4.47 m year−1. Landward migration occurred in an altitudinal range between − 5.93 and 6.77 m asl, where 50
Tropical cyclones (TCs) pose significant risks due to their associated hazards, including powerful winds, inland and coastal flooding, and wind waves. However, more reliable TC records are required to ensure a robust statistical analysis for risk assessment. To overcome this limitation, researchers have developed methods to generate synthetic tropical cyclones (STCs) that provide a larger sample size of occurrences at specific locations. This study compares STC databases from different sources such as Massachusetts Institute of Technology (MIT), Columbia HAZard model (CHAZ), Synthetic Tropical cyclOne geneRation Model (STORM), and Deltares with historical TCs from the International Best Track Archive for Climate Stewardship (IBTrACS) on a basin-wide scale in the North Atlantic Basin. The aim is to assess the effectiveness of STCs in replicating crucial historical tropical cyclones parameters for risk analysis and to identify potential biases in the STC generation models. The comparison uses a hexagonal mesh to evaluate characteristics such as maximum winds, translation speed, and residence time. The study acknowledges the validation paradox arising from the limited IBTrACS data at specific locations that make it difficult to rigorously validate the accuracy of STCs in those areas and from systematic differences across the STC datasets. Despite the historical TCs database limitation, comparing STC with IBTrACS characteristics remains the only viable method for assessing biases in STC generation models. The evaluated STCs reveal spatial bias patterns, which may indicate deficiencies in the underlying hazard models. Identifying and describing these biases aim to guide the use of these events and highlight key aspects for further development in STC generation methods.
Ephemeral river systems are vital water resources in semi-arid regions, but remain poorly studied regarding recent sedimentation. Their storage function gains importance under more frequent droughts and rapid population growth. This study addresses this gap by examining the Iishana system in northern Namibia and southern Angola, a transboundary network of ephemeral channels and depressions. The aim is to characterize sediment properties and quantify sedimentation rates in channel depressions to assess their influence on water storage capacity. Sediment profiles were physically and geochemically analyzed and dated by using ²¹⁰Pb and ¹³⁷Cs radionuclides, supplemented by radiocarbon analysis. Results show predominantly fine-grained sand and silt with weak pedogenic developments. Age–depth models indicate very low accumulation rates ranging from 0.017 to 0.12 g cm-2 yr-1(Constant Flux: Constant Sedimentation) and 0.05–0.07 g cm−² yr− 1 (Constant Rate of Supply). While ¹³⁷Cs proved unsuitable due to low activity, ²¹⁰Pb provided robust chronologies. Findings indicate that natural sediment infill currently has little effect on the water storage capacity of ephemeral depressions. They highlight both the potential and limitations of radionuclide dating in southern Africa, providing insights into sediment dynamics in semi-arid, low-gradient systems and contributing to a better understanding of these systems and to improved water management strategies.
