Search Results (14)

During a volcanic eruption, a large volume of pyroclastic material can be deposited on the roads and roofs of the urban areas near volcanoes. The use of volcanic ash as an additive for the manufacture of bricks provides a solution to the disposal of part of this natural residue and reduces the depletion of a non-renewable natural resource, clayey soil, which brings some environmental and economic advantages. The pore system, compactness, uniaxial compression strength, thermal conductivity, color and durability of bricks without and with the addition of volcanic ash were evaluated through hydric tests, mercury intrusion porosimetry, ultrasound, uniaxial compression tests, IR thermography, spectrophotometry and salt crystallization tests. The purpose of this research is to determine the feasibility of adding 10, 20 and 30% by weight of volcanic ash from La Palma (Canary Islands, Spain) in two grain sizes to produce bricks fired at 800, 950 and 1100 °C. The novelty of this study is to use two sizes of volcanic ash and fire the samples at 1100 °C, which is close to the liquidus temperature of basaltic magmas and allows a high degree of interaction between the volcanic ash and the brick matrix. The addition of fine volcanic ash was found to decrease the porosity of the bricks, although the use of high percentages of coarse volcanic ash resulted in bricks with almost the same porosity as the control samples. The volcanic ash acted as a filler, reducing the number of small pores in the bricks. The presence of vesicles in the volcanic ash reduced the compressive strength and the compactness of the bricks with additives. This reduction was more evident in bricks manufactured with 30% of coarse volcanic ash and fired at 800 and 950 °C, although they still reached the minimum resistance required for their use in construction. No significant differences in thermal conductivity were noticed between the bricks with and without volcanic ash additives, which is crucial in terms of energy savings and the construction of sustainable buildings. At 1100 °C the volcanic ash changed in color from black to red. As a result, the additive blended in better with the matrix of bricks fired at 1100 °C than in those fired at 800 and 950 °C. The bricks with and without volcanic ash and fired at 1100 °C remained intact after the salt crystallization tests. Less salt crystallized in the bricks with volcanic ash and fired at 800 and 950 °C than in the samples without additives, although their low compressive strength made them susceptible to decay. Full article

Volcanic ash (VA) is an abundant resource in many world regions that can be used as a supplementary cementitious material (SCM). However, its low reactivity limits its applications as a replacement for Portland cement. In this study, the improvement of its reactivity was evaluated through the calcination of VA (CVA) at 700 °C, alkali activation with Na₂SiO₃, CaCl₂, and Na₂CO₃, as well as its combination with other SCMs (lime, fly ash, and blast-furnace slags). Additionally, the effect of curing was analysed under different regimes: standard moist curing and heat curing. The use of alkaline activators, especially 2% Na₂SiO₃ and 1% CaCl₂, along with thermal curing (70 °C for 3 days) in mortars containing 50% VA, resulted in compressive strengths at 28 days, significantly higher than those obtained for mortars with non-activated VA or those cured under moist conditions. Furthermore, the addition of 10% fly ash (FA) and 5% slag (EC) to the mortars also led to the largest improvements in compressive strength. In addition, mortars cured at 70 °C exhibited lower shrinkage and improved resistance to acid attacks, particularly in those manufactured with CVA and 1% CaCl₂. This study concludes that it is possible to optimise the design of mortars with 50% VA in replacement of ordinary cement based on activation and curing methods. These methods improve early-age strength, reduce shrinkage and water absorption, and enhance acid resistance. Full article

In May 2008, Chaitén volcano entered an eruptive process, leading to one of the world’s largest eruptions in recent decades. The magnitude of tephra ejected by the eruption left different types of disturbances and caused diverse forms of environmental damage that were heterogeneously distributed across the surrounding area. We went to the field to assess the early vegetation responses a year after the eruption in September 2009. We evaluated the lateral-blast disturbance zone. We distributed a set of plots in three disturbed sites and one in an undisturbed site. In each of these sites, in a rectangular plot of 1000 m², we marked all standing trees, recording whether they were alive, resprouting, or dead. Additionally, in each site of 80 small plots (~4 m²), we tallied the regenerated plants, their coverage, and the log volume. We described whether the plant regeneration was occurring on a mineral or organic substrate (i.e., ash or leaf litter, respectively). In the blast zone, the eruption created a gradient of disturbance. Close to the crater, we found high levels of devastation marked by no surviving species, scarcely standing-dead trees and logs, and no tree regeneration. At the other extreme end of the disturbance zone, the trees with damaged crowns were resprouting, small plants were regrowing, and seedlings were more dispersed. The main form of regeneration was the resprouting of trunks or buried roots; additionally, a few seedlings were observed in the small plots and elsewhere in disturbed areas. The results suggest that the early stages of succession are shaped by life history traits like dispersion syndrome and regeneration strategy (i.e., vegetative), as was found after other volcanic eruptions. Likewise, the distribution of biological legacies, which is related to disturbance intensity, can cause certain species traits to thrive. For instance, in the blow-down zone, surviving species were chiefly those dispersed by the wind, while in the standing-dead zone, survivors were those dispersed by frugivorous birds. Additionally, we suggest that disturbance intensity variations are related to the elevation gradient. The varying intensities of disturbance further contribute to these ecological dynamics. The early succession in the blast zone of Chaitén volcano is influenced by the interaction between species-specific life history, altitudinal gradient, and biological legacies. Further studies are required to observe the current successional patterns that occur directly in the blast zone and compare these results with those obtained following other volcanic disturbances. Full article

This study investigated the potential for efficient and resourceful utilization of phosphogypsum (PG) through the preparation of a High-volume Phosphogypsum Cement Stabilized Road Base (HPG-CSSB). The investigation analyzed the unconfined compressive strength (UCS), water stability, strength formation mechanism, microstructure, and pollutant curing mechanism of HPG-CSSB by laser diffraction methods (LD), X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and inductively coupled plasma-mass spectrometry (ICP-MS). The optimal mix ratio of HPG-CSSB was 4% cement, 1% CA2, 35% PG, and 60% graded crushed stone. The UCS reached 6.6 MPa, 9.3 MPa, and 11.3 MPa at 7, 28, and 60 d, respectively. The alkaline curing agent stimulated cement activity and accelerated the release of Ca²⁺ and SO₄²⁻ from the PG. This formed many C-S-H gels and ettringite (AFt). The curing agent converted Ca²⁺ to C-(A)-S-H gels due to high volcanic ash activity. The diverse hydration products strengthened HPG-CSSB. The HPG-CSSB exhibits favorable water stability, demonstrating a mere 7.6% reduction in strength following 28 d of immersion. The C-S-H gel and AFt generated in the system can carry out ion exchange and adsorption precipitation with F⁻ and PO₄³⁻ in PG, achieving the curing effect of toxic and hazardous substances. HPG-CSSB meets the Class A standard for integrated wastewater discharge. Full article

In an alarming tale of agricultural excess, the relentless overuse of chemical fertilizers in modern farming methods have wreaked havoc on the once-fertile soil, mercilessly depleting its vital nutrients while inflicting irreparable harm on the delicate balance of the surrounding ecosystem. The excessive use of such fertilizers leaves residue on agricultural products, pollutes the environment, upsets agrarian ecosystems, and lowers soil quality. Furthermore, a significant proportion of the nutrient content, including nitrogen, phosphorus, and potassium, is lost from the soil (50–70%) before being utilized. Nanofertilizers, on the other hand, use nanoparticles to control the release of nutrients, making them more efficient and cost-effective than traditional fertilizers. Nanofertilizers comprise one or more plant nutrients within nanoparticles where at least 50% of the particles are smaller than 100 nanometers. Carbon nanotubes, graphene, and quantum dots are some examples of the types of nanomaterials used in the production of nanofertilizers. Nanofertilizers are a new generation of fertilizers that utilize advanced nanotechnology to provide an efficient and sustainable method of fertilizing crops. They are designed to deliver plant nutrients in a controlled manner, ensuring that the nutrients are gradually released over an extended period, thus providing a steady supply of essential elements to the plants. The controlled-release system is more efficient than traditional fertilizers, as it reduces the need for frequent application and the amount of fertilizer. These nanomaterials have a high surface area-to-volume ratio, making them ideal for holding and releasing nutrients. Naturally occurring nanoparticles are found in various sources, including volcanic ash, ocean, and biological matter such as viruses and dust. However, regarding large-scale production, relying solely on naturally occurring nanoparticles may not be sufficient or practical. In agriculture, nanotechnology has been primarily used to increase crop production while minimizing losses and activating plant defense mechanisms against pests, insects, and other environmental challenges. Furthermore, nanofertilizers can reduce runoff and nutrient leaching into the environment, improving environmental sustainability. They can also improve fertilizer use efficiency, leading to higher crop yields and reducing the overall cost of fertilizer application. Nanofertilizers are especially beneficial in areas where traditional fertilizers are inefficient or ineffective. Nanofertilizers can provide a more efficient and cost-effective way to fertilize crops while reducing the environmental impact of fertilizer application. They are the product of promising new technology that can help to meet the increasing demand for food and improve agricultural sustainability. Currently, nanofertilizers face limitations, including higher costs of production and potential environmental and safety concerns due to the use of nanomaterials, while further research is needed to fully understand their long-term effects on soil health, crop growth, and the environment. Full article

Aerial frames and satellite imagery are widely recognized data sources from which to produce maps. For volcanoes, maps enable the quantification of erupted ash and the destruction caused. The last eruptive sequence on Deception Island was endured from 1967 to 1970. Analogue maps were produced via classical photogrammetric methods with a high degree of human intervention mainly to analyse the volcanic-centres areas only. However, historical aerial frames cover the whole of Deception Island. Structure from motion photogrammetry, a near-automated compilation of digital image processing strategies, minimizes the degree of human intervention to produce orthographic mosaics and digital elevation models from digital aerial frames. Orthographic mosaics were produced from historical aerial frames of 1956 and 1968, and a Kompsat-3 image of 2020. Their shared root-mean-square deviation was 1.8 m and 1.7 m in easting and northing, respectively, at ground control points measured with phase-differential global navigation satellite systems. The digital elevation models were processed with a root-mean-square deviation of 2.3 m and 3.6 m from 1956 and 1968 aerial frames, respectively. As the first application, erupted ashfall and the subsequent destruction, mainly at the former Chilean and British bases, were identified, and the volume of erupted ash was assessed to be over 0.16 km³ within the area mapped by these new digital cartographic products. Full article

Lime stabilization is one of the main methods to achieve efficient treatment and resource utilization of waste slurry. This study investigated the compressibility and permeability of lime-stabilized slurry with different granular gradations based on the ultra-low stress consolidation/permeability test and identified the stabilization mechanism of lime-stabilized slurry with high water content by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) tests. The test results indicated that (i) lime-stabilized slurry with high water content showed obvious evidence of remolded yield stress and (ii) the remolded yield stress increased with the increasing lime dosage. Lime was found to induce the flocculation of clay to form aggregates through ion exchange, further stabilizing them through the volcanic ash reaction, thus increasing the remolded yield strength of the stabilized slurry. The remolded yield stress of the Hangzhou stabilized slurry with a 1% lime dosage was shown to increase from 0 kPa to 5.71 kPa, while the compression index C_S1 decreased by 68.8%. In addition, the pore volumes and diameters of the soil increased once the flocculation was completed, leading to increased permeability of the stabilized slurry. It was, however, observed that the stabilized slurry permeability did not increase infinitely with the increasing lime dosage, but on the contrary decreased once the lime dosage exceeded a certain threshold value. The permeability of the Hangzhou stabilized slurry was found to be one order of magnitude higher than that of the remolded slurry at the optimal dosage. Whereas for slurry with high clay content, the recommended lime dosage was established to be 2% to reduce its compressibility or enhance its permeability; for slurry with high silt content, the recommended lime dosage was ascertained to be 3%. Full article

We present a new automatic procedure for updating digital topographic data from multi-source satellite imagery, which consists in the production of Digital Surface Models (DSMs) from high resolution optical satellite images, followed by a context-aware fusion that exploits the complementary characteristics of the multi-source DSMs. The fused DSM minimizes blunders and artifacts due to occlusions (e.g., the presence of clouds, snow or ash plumes) in the source images, resulting in improved accuracy and quality versus those that are not merged. The procedure has been tested to produce the 2021 digital topography of Mt Etna, whose summit area is constantly changing and shows the new peak of 3347 m on the north rim of the South East Crater. We also employ the 2021 DSM to measure the volcanic deposits emplaced in the last five years, finding about 120 million cubic meters, with a yearly average volume of about 24 million cubic meters in agreement with the large eruptive rates registered at Mt Etna since the nineteen seventies. The flexibility and modularity of the presented procedure make it easily exportable to other environmental contexts, allowing for a fast and frequent reconstruction of topographic surfaces even in extreme environments. Full article

The development of sustainable, environmentally friendly alkali-activated binder has emerged as an alternative to ordinary Portland cement. The engineering and durability properties of alkali-activated binder using various precursor combinations have been investigated; however, no study has focused on the impact of high-volume natural pozzolan (NP) on the acid resistance of alkali-activated NP and limestone powder. Therefore, the current study assesses the impact of high-volume natural pozzolan (volcanic ash) on the durability properties of alkali-activated natural pozzolan (NP) and limestone powder (LSP) mortar by immersion in 6% H₂SO₄ for 365 days. The samples were prepared with different binder ratios using alkaline activators (10 M NaOH_(aq) and Na₂SO₄) combined in a 1:1 ratio and cured at 75 °C. NP was combined with the LSP at three different combinations: NP:LSP = 40:60 (AAN₄₀L₆₀), 50:50 (AAN₅₀L₅₀), and 60:40 (AAN₆₀L₄₀), representing low-volume, balanced, and high-volume binder combinations. Water absorption, weight change, and compressive strength were examined. The microstructural changes were also investigated using FTIR, XRD, and SEM/EDS characterization tools. Visual examination showed insignificant deterioration in the sample with excess natural pozzolan (AAN₆₀L₄₀) after 1 year of acid exposure, and the maximum residual strengths were 20.8 MPa and 6.68 MPa in AAN₆₀L₄₀ and AAN₄₀L₆₀ with mass gain (1.37%) and loss (10.64%), respectively. The high sulfuric acid resistance of AAN₆₀L₄₀ mortar was attributed to the high Ca/Si = 10 within the C-A-S-H and N-A-S-H formed. The low residual strength recorded in AAN₄₀L₆₀ was a result of gypsum formation from an acid attack of calcium-dominated limestone powder. The controlling factor for the resistance of the binder to acid corrosion was the NP/LSP ratio, whose factor below 0.6 caused significant debilitating effects. Full article

UAV-based photogrammetry is becoming increasingly popular even in application fields that, until recently, were deemed unsuitable for this technique. Depending on the characteristics of the investigated scenario, the generation of three-dimensional (3D) topographic models may in fact be affected by significant inaccuracies unless site-specific adaptations are implemented into the data collection and processing routines. In this paper, an ad hoc procedure to exploit high-resolution aerial photogrammetry for the multitemporal analysis of the unstable Sciara del Fuoco (SdF) slope at Stromboli Island (Italy) is presented. Use of the technique is inherently problematic because of the homogeneous aspect of the gray ash slope, which prevents a straightforward identification of match points in continuous frames. Moreover, due to site accessibility restrictions enforced by local authorities after the volcanic paroxysm in July 2019, Ground Control Points (GCPs) cannot be positioned to constrain georeferencing. Therefore, all 3D point clouds were georeferenced using GCPs acquired in a 2019 (pre-paroxysm) survey, together with stable Virtual Ground Control Points (VGCPs) belonging to a LiDAR survey carried out in 2012. Alignment refinement was then performed by means of an iterative algorithm based on the closest points. The procedure succeeded in correctly georeferencing six high-resolution point clouds acquired from April 2017 to July 2021, whose time-focused analysis made it possible to track several geomorphological structures associated with the continued volcanic activity. The procedure can be further extended to smaller-scale analyses such as the estimation of locally eroded/accumulated volumes and pave the way for rapid UAV-based georeferenced surveys in emergency conditions at the SdF. Full article

The volcanic eruption of Cumbre Vieja (La Palma Island, Spain), started on 19 September 2021 and was declared terminated on 25 December 2021. A complete set of aerosol measurements were deployed around the volcano within the first month of the eruptive activity. This paper describes the results of the observations made at Tazacorte on the west bank of the island where a polarized micro-pulse lidar was deployed. The analyzed two-and-a-half months (16 October–31 December) reveal that the peak height of the lowermost and strongest volcanic plume did not exceed 3 km (the mean of the hourly values is 1.43 ± 0.45 km over the whole period) and was highly variable. The peak height of the lowermost volcanic plume steadily increased until week 11 after the eruption started (and 3 weeks before its end) and started decreasing afterward. The ash mass concentration was assessed with a method based on the polarization capability of the instrument. Two days with a high ash load were selected: The ash backscatter coefficient, aerosol optical depth, and the volume and particle depolarization ratios were, respectively, 3.6 (2.4) Mm⁻¹sr⁻¹, 0.52 (0.19), 0.13 (0.07) and 0.23 (0.13) on 18 October (15 November). Considering the limitation of current remote sensing techniques to detect large-to-giant particles, the ash mass concentration on the day with the highest ash load (18 October) was estimated to have peaked in the range of 800–3200 μg m⁻³ in the lowermost layer below 2.5 km. Full article

The paper is devoted to the description of observations over atmospheric and electric effects from volcanic eruptions on Kamchatka peninsula (Russia) and perspectives of their development. To collect information about atmospheric-electric effects accompanying the eruptions of Kamchatka volcanoes, three sensor networks and a VLF radio direction finding station are used. The World Wide Lightning Location Network (WWLLN) provides information on high-current lightning discharges that occur during the development of an eruptive cloud (EC). Variations in the electric field of the atmosphere (AEF $E_z$ ), during the passage of EC, were obtained by a network of electric field mills at the sites for volcanic activity observations. Seismic detector network was used to make precision reference to the eruptions. Based on the data obtained, a description is given of the dynamics of eruptions of the most active volcanoes in Kamchatka and the Northern Kuril Islands (Shiveluch, Bezymianny, Ebeko). The paper presents a simulation of the response of the atmospheric electric field, which showed that the approximation by the field of distributed charges makes it possible to estimate the volume charges of EC. The fact of a multi-stage volcanic thunderstorm is confirmed. The first stage is associated with the formation of an eruptive column, and the second with the emergence, development and transfer of EC. Registration of electrical and electromagnetic processes in eruptive clouds can be one of the components of complex observations of volcanic eruptions in order to assess the ash hazard for air transport. Full article

Production of artificial lightweight aggregate (LWA) from industrial by-products or abundant volcanic mud is a promising solution to prevent damaging the environment due to the mining of natural aggregate. However, improvements are still needed in order to control the high water absorption of LWA and strength reduction in resulting concrete or mortar. Hence in this research, fly ash, municipal solid waste incineration bottom ash (MSWI BA), and Sidoarjo volcanic mud (Lusi) were employed as a precursor and activated using NaOH 6 M and Na₂SiO₃ in producing LWA. The influence of the type of the precursors on the physical properties of resulting LWA was investigated. The effect of replacing natural fine aggregate with the resulting LWA on the compressive strength and volume density of mortar was also determined. Finer particles, a high amount of amorphous phase, and low loss on ignition (LOI) of the raw material improved the properties of resulting LWA. Mortar compressive strength was decreased by 6% when replacing 16% by volume of natural fine aggregate with fly ash based LWA. Compared to the expanded clay LWA, the properties of alternative LWAs in this study were slightly, but not significantly, inferior. Alternative LWA becomes attractive when considering that expanded clay LWA requires more energy during the sintering process. Full article

Andean headwater catchments are key components of the hydrological cycle, given that they capture moisture, store water and release it for Chilean cities, industry, agriculture, and cities in Chile. However, knowledge about within-Andean catchment processes is far from clear. Most soils in the Andes derive from volcanic ash Andosols and Arenosols presenting high organic matter, high-water retention capacity and fine pores; and are very dry during summer. Despite their importance, there is little research on the hillslope hydrology of Andosols. Environmental isotopes such as Deuterium and 18-O are direct tracers for water and useful on analyzing water-soil interactions. This work explores, for the first time, the efficiency of cryogenic vacuum extraction to remove water from two contrasting soil types (Arenosols, Andosols) at five soil water retention energies (from −1500 to −33 kPa). Two experiments were carried out to analyse the impact of extraction time, and initial water content on the amount of extracted water, while a third experiment tested whether the cryogenic vacuum extraction changed the isotopic ratios after extraction. Minimum extraction times to recover over 90% of water initially in the soil samples were 40–50 min and varied with soil texture. Minimum volume for very dry soils were 0.2 mL (loamy sand) and 1 mL (loam). After extraction, the difference between the isotope standard and the isotopic values after extraction was acceptable. Thus, we recommend this procedure for soils derived from volcanic ashes. Full article