Volcanic Ash Samples Research Articles

Utilization of volcanic ashes for the production of geopolymers cured at ambient temperature

Two types of volcanic ash were characterized (chemical and mineralogical compositions, amorphous phase composition, particle size distribution and specific surface area) and then used as raw materials for the synthesis of geopolymer cements cured at ambient temperature (24±3°C). The synthesized products were characterized by determination of setting time, 28-day compressive strength, X-ray diffraction and Fourier Transform Infrared Spectroscopy. The mineralogical composition, the amorphous phase composition, the particle size distribution, the specific surface area of the volcanic ashes as well as the molar ratios of Na2O/Al2O3 of the synthesized products and of SiO2/Na2O of the alkaline solutions were the main parameters which influenced the synthesis of geopolymers with attractive characteristics at ambient curing temperature. The volcanic ash sample whose mineralogical composition contained anhydrite, low content of free CaO, low specific surface area (2.3m2/g) and synthesized products with Na2O/Al2O3 molar ratios between 1.23 and 1.44 led to long setting time (test samples could be handled easily only after 14days at ambient atmosphere of the laboratory) and low 28-day compressive strength (9–19MPa) geopolymers. Moreover, its products swelled and presented cracks resulting from the formation of ettringite. The volcanic ash sample with large (Al2O3+SiO2)% wt of amorphous phase, high specific surface area (15.7m2/g) and synthesized products with Na2O/Al2O3 molar ratios between 1.04 and 1.31 led to more effective geopolymers: setting time was between 490 and 180min and 28-day compressive strength between 23 and 50MPa at ambient curing temperature (24±3°C).

Scavenging of sulphur, halogens and trace metals by volcanic ash: The 2010 Eyjafjallajökull eruption

The Eyjafjallajökull volcanic eruption in 2010 released considerable amounts of ash into the high troposphere-low stratosphere, leading to unprecedented disruption of air traffic over Europe. The role of such fine-grained tephra in adsorbing, and therefore rapidly scavenging, volcanogenic volatile elements such as sulphur and halogens, is explored here. We report on results (major to trace element chemistry) of leaching experiments carried out on 20 volcanic ash samples, taken from the deposits of the main phases of the eruption (March–April 2010), or directly while falling (5–9 May 2010). Ash leachate solutions from Eyjafjallajökull are dominated – among cations – by Ca and Na, and display nearly equal S:Cl:F abundances (mean S/Cl and S/F molar ratios of 0.95 and 0.34, respectively). Abundances of major elements on surface minerals from freshly fallen ash are found to increase linearly upon increasing distance from the eruptive vents (a proxy for in-plume residence times). This allows for the formation rates of sulphur- and halogen-bearing surface salts to be quantified (3×10−9 to 2×10−8molm2s−1), and for the averaged rate of in-plume ash-dissolution to be estimated (1.5×10−8molm−2s−1; this sourcing the majority of cation species to soluble surface salts). These fast in-plume heterogeneous reactions are the cause of large volatile depositions: we estimate that 282 tons of elemental S, 605 tons of Cl, and 691 tons of F were daily ground deposited via ash over Iceland in early May 2010. Since fluorine is ∼3 times more rapidly processed in the plume than S and halogens (e.g., F is extremely reactive both in gas and aerosol forms and it is rapidly adsorbed onto ash), ash leachate compositions are in no way representative of S:Cl:F proportions in volcanic gases, and consequently of limited use in eruption monitoring.

Combined neutralization–adsorption system for the disposal of hydrothermally altered excavated rock producing acidic leachate with hazardous elements

Hydrothermally altered rock excavated in a tunnel project produces acidic leachate containing hazardous elements that include arsenic (As), lead (Pb), copper (Cu) and zinc (Zn). To mitigate this problem, this paper evaluated a combined neutralization–adsorption system that used readily available and cheap reagents like calcium carbonate (CaCO3) and partly-weathered volcanic ash. Batch neutralization experiments showed that CaCO3 was effective in raising the pH of the leachate around neutral while the batch adsorption experiments illustrated that the volcanic ash sample collected near the tunnel project area was highly capable of adsorbing arsenate (As[V]), Pb, Cu and Zn. Under column conditions, the amount of hazardous elements released from the rock increased by several folds and their breakthrough curves had flushing-out trends. The mechanisms of As and heavy metals release probably include the dissolution of soluble phases and pyrite oxidation. Addition of CaCO3 in the column experiments based on estimates from the batch results underestimated the amount of neutralizer needed to adjust the effluent pH to around 8, resulting only in slight increase of the pH. Nevertheless, the presence of CaCO3 drastically reduced the amount of hazardous elements released from the altered rock especially during the initial stages of the column experiments. Combining neutralization and adsorption effectively reduced the amount of As and heavy metals in the effluent throughout the duration of the column experiments, which is attributed to the slight neutralizing effect of volcanic ash that raised the pH around circumneutral as well as its rich Al and Fe oxyhydroxide/oxide contents. The combined system immobilized the hazardous elements through a combination of co-precipitation and adsorption reactions and showed potential as an alternative method for the disposal of altered rocks producing acidic leachate.

Atmospheric ice nuclei in the Eyjafjallajökull volcanic ash plume

Abstract. We have sampled atmospheric ice nuclei (IN) and aerosol in Germany and in Israel during spring 2010. IN were analyzed by the static vapor diffusion chamber FRIDGE, as well as by electron microscopy. During the Eyjafjallajökull volcanic eruption of April 2010 we have measured the highest ice nucleus number concentrations (>600 l−1) in our record of 2 yr of daily IN measurements in central Germany. Even in Israel, located about 5000 km away from Iceland, IN were as high as otherwise only during desert dust storms. The fraction of aerosol activated as ice nuclei at −18 °C and 119% rhice and the corresponding area density of ice-active sites per aerosol surface were considerably higher than what we observed during an intense outbreak of Saharan dust over Europe in May 2008. Pure volcanic ash accounts for at least 53–68% of the 239 individual ice nucleating particles that we collected in aerosol samples from the event and analyzed by electron microscopy. Volcanic ash samples that had been collected close to the eruption site were aerosolized in the laboratory and measured by FRIDGE. Our analysis confirms the relatively poor ice nucleating efficiency (at −18 °C and 119% ice-saturation) of such "fresh" volcanic ash, as it had recently been found by other workers. We find that both the fraction of the aerosol that is active as ice nuclei as well as the density of ice-active sites on the aerosol surface are three orders of magnitude larger in the samples collected from ambient air during the volcanic peaks than in the aerosolized samples from the ash collected close to the eruption site. From this we conclude that the ice-nucleating properties of volcanic ash may be altered substantially by aging and processing during long-range transport in the atmosphere, and that global volcanism deserves further attention as a potential source of atmospheric ice nuclei.

Airborne in-situ investigations of the Eyjafjallajökull volcanic ash plume on Iceland and over north-western Germany with light aircrafts and optical particle counters

During the time period of the eruption of the Icelandic volcano Eyjafjallajökull in April/May 2010 the Duesseldorf University of Applied Sciences has performed 14 research flights in situations with and without the volcanic ash plume over Germany. In parallel to the research flights in Germany three measurement flights have been performed by the University of Iceland in May 2010 over the western part of Iceland. During two of these flights the outskirts of the eruption plume were entered directly, delivering most direct measurements within the eruption plume during this eruptive event. For all the measurement flights reported here, light durable piston-motor driven aircrafts were used, which were equipped with optical particle counters for in-situ measurements. Real-time monitoring of the particle concentrations was possible during the flights. As different types of optical particle counters have been used in Iceland and Germany, the optical particle counters have been re-calibrated after the flights to the same standard using gravimetric reference methods and original Eyjafjallajökull volcanic ash samples. In-situ measurement results with high spatial resolution, directly from the eruption plume in Iceland as well as from the dispersed and several days old plume over Germany, are therefore presented here for the first time. They are normalized to the same ash concentration calibration standard. Moreover, airborne particles could be sampled directly out of the eruption plume in Iceland as well as during the flights over Germany. During the research flights over Iceland from 9 May 2011 to 11 May 2011 the ash emitted from the vent of the volcano turned out to be concentrated in a narrow well-defined plume of about 10 km width at a distance of 45–60 km away from the vent. Outside this plume the airborne ash concentrations could be proved to be below 50 μg m −3 over western Iceland. However, by entering the outskirts of the plume directly the research aircraft could detect ash concentrations of up to 2000 μg m −3 . On the other hand, the ash plume, which was analysed by research flights over Germany several thousand km away from the eruption vent, appeared to be significantly structured in horizontal and vertical directions. Different sub-plumes could be found. Peak concentrations of more than 330 μg m −3 could be detected. The results of the measurements within the ash plume over Germany were compared with the predictions of the London VAAC model. The range of ash concentrations found by the research aircraft in Germany were not in conflict with the calculations of concentration regimes by the London VAAC model. However, the in-situ measurements performed by the research aircraft were able to deliver information about the structure and composition of the ash plume, which could not be covered by the dispersion model. Therefore, light piston-motor driven aircrafts equipped with optical particle counters proved to be a very versatile tool for the real-time in-situ determination of the spatial extension of volcanic ash plumes, the ash particle size distributions and the particle mass concentrations. Moreover, all these parameters could be measured with a high horizontal and vertical spatial resolution. Therefore, these kinds of measurements can deliver immediate data for the validation and verification of dispersion models and can give direct in-situ information additional to LIDAR measurements and satellite observations. As the piston-motor driven aircrafts are able to operate even at elevated volcanic ash concentrations they can provide valuable ash concentration results for air traffic safety. ► Aircraft in-situ measurements of the Eyjafjalla ash plume with optical particle counters. ► Direct measurements up to 2000 μg m −3 in the outskirts of the ashplume on Iceland. ► Ash plume mapping over northern Germany with concentrations up to 330 μg m −3 . ► Comparison with London VAAC model. ► Calibration of the optical Particle counters with original Eyjafjalla ash.

Volcanic ash from the 2010 Eyjafjallajökull eruption

Abstract The April 2010 eruption of Eyjafjallajokull volcano created major disruption to European air traffic. The main uncertainty in predicting the volcanic ash distribution in air space was the nature of the eruption plume including the grain size of the volcanic ash. The volcanic ash samples collected in the vicinity of the volcano on April 15th 2010, the first day of air traffic disruption in Europe, reveal that up to 70% of the mass was less than 60 μm in diameter. This fine grained ash could remain suspended in the atmosphere for days, posing threats to air traffic.

Geochemistry and correlation of volcanic ash beds from the Rootsiküla Stage (Wenlock–Ludlow) in the eastern Baltic

Nine altered volcanic ash samples from the shoal and lagoonal sediments of the Rootsikula Stage (Wenlock-Ludlow boundary interval, Estonia) were analysed, compared and correlated with five samples of deep sea environments from Latvia. Volcanic ash correlations indicate that the Wenlock-Ludlow boundary correlates with the boundary of the Viita and Kuusnomme beds, i.e., it is significantly lower than proposed earlier. The distribution of chitinozoans supports this new correlation. Geochemical data indicate subalkaline source magma of volcanic ashes with potassium dominating over sodium.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Mass-independent isotopic signatures of volcanic sulfate from three supereruption ash deposits in Lake Tecopa, California

Hundreds to thousands of megatons of sulfur dioxide released by supereruptions can change chemical and physical properties of the atmosphere and thus induce climate perturbations. We present oxygen and sulfur isotope analyses of sulfate in 48 volcanic ash samples, and 26 sediment samples from dry lake beds in the Tecopa basin, California, USA. These ash layers represent three supereruptions, including the 0.64 Ma Lava Creek Tuff, 2.04 Ma Huckleberry Ridge Tuff and 0.76 Ma Bishop Tuff. Mass-independent oxygen signatures (Δ 17O up to 2.26‰) that are present in these ash units, and not in associated sediments, indicate oxidation of volcanic SO 2 by mass-independent ozone and its products. In this study, we consider the formation, deposition, preservation and dilution of mass-independent volcanic sulfate (MIVS). Using the isotopic compositions of the sulfates, we construct a mixing model that demonstrates that the main source of sulfate in Lake Tecopa is mass-dependent sediment-derived sulfate (MDSDS, > 77%). However, ash beds still preserve up to 23% of MIVS that initially had undiluted Δ 17O value around 8‰, and Δ 33S as low as − 0.35‰, and Δ 36S up to 1.08‰. Therefore, despite potential dilution by MDSDS, the MIVS signatures can be preserved in the geologic record for few million years, if deposited as gypsum in arid environments, alkaline or saline lake. The oxygen and sulfur mass-independent signatures of the volcanic sulfates indicate that photolysis and oxidation of volcanic SO 2 has been achieved in the upper atmosphere. Since only supervolcanic eruptions were shown to generate massive amount of mass-independent sulfate, it requires that up to 20–60% of the global ozone layer is consumed as a result of supervolcanic SO 2 released. This may occur as a result of a strong physical and chemical degradation of the tropopause; we speculate that the distinction between the high-troposphere and the low-stratosphere, at least locally, could be erased by supereruptions, and recorded by MIVS.

Rapid releases of metal salts and nutrients following the deposition of volcanic ash into aqueous environments

Deposition of volcanic ash into aqueous environments leads to dissolution of adsorbed metal salts and aerosols, increasing the bioavailability of key nutrients. Volcanogenic fertilization events could increase marine primary productivity, leading to a drawdown of atmospheric CO 2. Here we conduct flow-through experiments on unhydrated volcanic ash samples from a variety of locations and sources, measuring the concentrations and fluxes of elements into de-ionized water and two contrasting ocean surface waters. Comparisons of element fluxes show that dissolution of adsorbed surface salts and aerosols dominates over glass dissolution, even in sustained low pH conditions. These surface ash-leachates appear unstable, decaying in situ even if kept unhydrated. Volcanic ash from recent eruptions is shown to have a large fertilization potential in both fresh and saline water. Fluorine concentrations are integral to bulk dissolution rates and samples with high F concentrations display elevated fluxes of some nutrients, particularly Fe, Si, and P. Bio-limiting micronutrients are released in large quantities, suggesting that subsequent biological growth will be limited by macronutrient availability. Importantly, acidification of surface waters and high fluxes of toxic elements highlights the potential of volcanic ash-leachates to poison aqueous environments. In particular, large pH changes can cause undersaturation of CaCO 3 polymorphs, damaging populations of calcifying organisms. Deposition of volcanic ash can both fertilize and/or poison aqueous environments, causing significant changes to surface water chemistry and biogeochemical cycles.

Use of immobile trace elements for the correlation of Telychian bentonites on Saaremaa Island, Estonia, and mapping of volcanic ash clouds

Thirty suspected altered volcanic ash (bentonite) samples from the Nassumaa-825 and Orissaare-859 sections were analysed by the X-ray fluorescence method. Twenty of these samples revealed chemical signs of pure volcanogenic material, one was of mixed terrigenous-volcanogenic origin, and nine were classified as terrigenous claystones. Twenty of the bentonites were correlated, with variable confidence, with bentonites from earlier studied sections; one sample represents a formerly unknown eruption. New and earlier published bentonite correlations were used for tracing the diachronous nature of the Rumba-Velise formations boundary and for composing new isopach schemes of six Telychian bentonites.

Chlorine isotope variations across the Izu-Bonin-Mariana arc

Chlorine isotope ratios were determined for volcanic gas, geothermal well, ash, and lava samples along the Izu-Bonin-Mariana volcanic front, serpentinite clasts and muds from serpentine seamounts (Conical, South Chamorro, Torishima), basalts from the Guguan cross-chain, and sediments from Ocean Drilling Program (ODP) Sites 800, 801, 802, and 1149. There is no systematic variation in δ 37 Cl values along the volcanic front in either gas or ash samples. In contrast, distinct variations occur across the arc, implying variations in the fluid source at different depths within the subduction zone. Serpentinite clasts and serpentine muds from the seamounts tap a source of ~30 km depth and have δ 37 Cl values of structurally bound chloride of +0.4‰ ± 0.4‰ ( n = 24), identical to most seafloor serpentinites, suggesting a serpentinite (chrysotile and/or lizardite to antigorite transition) fluid source. Tapping deeper levels of the subduction zone (~115–130 km depth), volcanic gases and ashes have δ 37 Cl values averaging −1.1‰ ± 1.0‰ ( n = 29), precisely overlapping the range measured in sediments from ODP cores (−1.1‰ ± +0.7‰, n = 11) and limited altered oceanic crust (AOC). Both sediments and AOC are possible Cl sources in the volcanic front. The Guguan cross-chain basalts come from the greatest depths and have an average δ 37 Cl value of +0.2‰ ± 0.2‰ ( n = 3), suggesting a second serpentine-derived source, in this case from antigorite breakdown at ~200 km depth.

Glacial and Postglacial History of the White Cloud Peaks-Boulder Mountains, Idaho, U.S.A.

Glacial and glaciofluvial deposits are mapped and differentiated to develop new local, relative-age (RD) stratigraphies for the North Fork of the Big Lost River, Slate Creek and Pole Creek drainages in the White Cloud Peaks and Boulder Mountains, Idaho. This stratigraphic model expands the areal extent of the "Idaho glacial model". Volcanic ash samples collected from the study area are petrographically characterized and correlated, on the basis of mineralogy and glass geochemistry, to reference samples of identified Cascade Range tephras. Four distinct tephras are recognized including; Mount St. Helens-Set S (13,600-13,300 yr BP), Glacier Peak-Set B (11,250 yr BP), Mount Mazama (6600 yr BP) and Mount St. Helens-Set Ye (4350 yr BP). A core of lake sediments containing two tephra units was obtained from a site called "Pole Creek kettle". Pollen and sediment analyses indicate three intervals of late Pleistocene and Holocene climatic change. Cool and wet climatic conditions prevailed in the region shortly before and immediately following the deposition of the Glacier Peak-Set B ash (11,250 yr BP). Climatic warming occurred from approximately 10,500 to 6600 yr BP after which warm, dry conditions prevailed. Sediment accumulation in the kettle ceased by 4350 yr BP. The presence of Glacier Peak-Set B tephra in the base of the Pole Creek kettle core provides a minimum age of 11,250 yr BP for the retreat of valley glaciers from their Late Wisconsinan maximum position. A radiocarbon date of 8450 + 85 yr BP (SI-5181), and the presence of Mount Mazama ash (6600 yr BP) up-core support the Glacier Peak-Set B identification.

The negative polarization of light scattered from particulate surfaces and of independently scattering particles

Laboratory and computer modeling investigations of the negative polarization of particulate surfaces at small phase angles are important in the development of remote-sensing research of atmosphereless celestial bodies. We present measurements of the phase-angle dependence of the intensity and degree of linear polarization of particles in air and particulate surfaces composed of the particles at illuminating wavelengths 0.63 and 0.44μm. The particulate surface measurements were carried out with the equipment at the Kharkov National University; whereas the scattering measurements of single particles were carried out with the Amsterdam equipment. We study a suite of samples of natural mineral particles (including two volcanic ash samples) that are characterized by a variety of shapes and colors. We find evidence that suggests that in some instances the negative polarization of the surfaces is a remnant of the negative polarization of the single scattering by particles constituting the surfaces. Computer simulations of the light scattering from the particulate surfaces support this conclusion.

The respiratory toxicity of airborne volcanic ash from the Soufrière Hills volcano, Montserrat

AbstractThe Soufrière Hills stratovolcano on the Caribbean island of Montserrat has been erupting since 18th July 1995. An enormous amount of respirable volcanic ash has been suspended into the atmosphere by the eruptions and wind re-suspension of deposited ash. The large amount of fine, airborne particulate matter, in particular the component 10 μm equivalent aerodynamic diameter (PM10), is a cause of medical concern. Airborne levels have frequently exceeded the UK environmental standard for PM10, (50 μg/m3), although it is noted that this standard was primarily set for urban PM10. The crystalline silica in the ash is mostly cristobalite, at reported levels up to 20%. The UK government’s Chief Medical Officer, referring to Montserrat, has suggested that long-term exposure to high levels of volcanic ash could lead to silicosis. These concerns have prompted government-funded investigations into the potential toxicity of well characterized volcanic ash samples from Montserrat. Given the well established toxicity of cristobalite, particular attention was paid to the amount of this mineral in the ash samples. Three ash samples were tested: (1) a vulcanian eruption ash, (2) ash released in a domecollapse pyroclastic flow, and (3) ash from a major vulcanian explosion that was wind-transported to, and deposited on, the neighbouring island of Antigua. Comparative toxicological studies were carried out on respirable preparations of these three samples together with appropriate control mineral dusts that matched the major components of the Montserrat samples: anorthite, labradorite, cristobalite/ obsidian and cristobalite. Alpha quartz (DQ12) was the positive control. All samples, including the controls, were characterized to establish particle-size distributions, particle morphologies, and to confirm the mineralogy. Rats were challenged with 1 mg via intratracheal instillation, and groups sacrificed at three time points (1, 3 and 9 weeks). Health assessment was made by examining endpoints of increasing lung damage such as inflammation, permeability (oedema), changes in epithelium, and increase in the size of broncho-thoracic lymph nodes. The data indicate that Montserrat respirable ash, derived from dome collapse pyroclastic flows or vulcanian explosions, has minimal acute bioreactivity in the lung. The feldspar standards showed low bioreactivity, in stark contrast to the cristobalite standard that showed progressive increases in lung damage. These results suggest that either the mass of cristobalite present in the Montserrat ash was insufficient to cause an effect in the lung, or the cristobalite in the ash was, for some as yet unknown reason, markedly less bioreactive than our pure cristobalite standard.

Geochemical correlation of archaeological sites using tephra from the Minoan eruption

Pumice and volcanic ash samples from different localities in the Middle East region were analysed for major and trace element contents using instrumental neutron activation analysis (INAA). Samples of pumice found in archaeological excavations of Early to Middle Bronze age (≈3500 y. B.P.) from Egypt, Palestine, and Israel could be correlated to the different possible volcanic eruption events in the Aegean Sea. Volcanic ash beds as primary deposits of the Minoan eruption of the Santorini volcano between 1650–1450 B.C. were traced throughout the Aegean islands, in drill cores from the Mediterranean and the Black sea, and in Anatolia. This study lead to a new interpretation of the main distribution of volcanic ash falls from this eruption. Therefore, primary ash beds can be used as direct chronological tracers, whereas pumice found in excavations can only be used for dating by first appearance.

Rainwater and ash leachate analysis as proxies for plume chemistry at Soufrière Hills volcano, Montserrat

Abstract Chloride and sulphate concentrations in rainwater and water-soluble leachates from volcanic ash samples track the compositions of gas emissions at the Soufrière Hills Volcano, Montserrat, from 1996 to 2001. There are both systematic spatial and temporal variations in the chloride/sulphate ratio (expressed as the equivalent HCl/SO 2 mass ratio) in rainwater and ash leachates. Temporal variations reflect changes in eruption rate and eruptive style. Mass ratios of HCl/SO 2 in ash leachates correspond closely with those obtained by open-path Fourier transform infrared (OP-FTIR) spectroscopy, and reflect changes in volatile emissions throughout the eruption. Both leachate and OP-FTIR spectroscopic analyses show mass ratios of HCl/SO 2 > 1 during dome growth, and HCl/SO 2 < 1 during non-eruptive periods. The HCl/SO 2 mass ratios in rainwater samples from 1996 and 1997 show temporal variations that correlate with changes in extrusion rate. The HCl/SO 2 ratios in plume-affected rainwater and ash leachates from June and July 2001 correlate positively with increasing rockfall energy, and with increasing eruption rate prior to a dome collapse event. The HCl/SO 2 mass ratios in water-soluble ash leachates and rainwater samples collected at the same time and from the same sites, are linearly correlated, with rainwater HCl/SO 2 ratios systematically two to three times higher than ash leachate ratios. Spatial patterns of rainwater pH, and HCl/SO 2 in rainwater and ash leachates are principally influenced by the proximity of the sampling sites to the active dome, and to the typical pattern of dispersion of the plume by tropospheric winds. These results demonstrate that rainwater chemistry and ash leachate analysis provides a useful indicator of volcanic activity, and represents a valuable supplement to volcano surveillance efforts.

Several Chemical and Mineralogical Properties of Volcanic Ash Samples Erupted in 2000 from Miyake Island

Several Chemical and Mineralogical Properties of Volcanic Ash Samples Erupted in 2000 from Miyake Island

TEM-EDX study of weathered layers on the surface of volcanic glass, bytownite, and hypersthene in volcanic ash from Sakurajima volcano, Japan

Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis were used to characterize naturally weathered layers on the surface of volcanic glass, bytownite, hypersthene, and secondary precipitates in volcanic ash erupted from the Sakurajima volcano, Japan. TEM analysis of the volcanic ash revealed sharply, bounded, leached layers on the surface of the volcanic glass and bytownite that were thin structureless coatings mostly ≤0.1 μm thick. EDX analysis showed that the leached layer on the volcanic glass surface is preferentially depleted in Si and enriched in Al relative to its parent matrix, whereas the leached layer on the bytownite surface is extremely depleted in Al and enriched in Si relative to the original bytownite matrix. These chemical characteristics of the weathered layers indicate that incipient dissolution of volcanic glass and bytownite proceeded by preferential leaching of Si and Al, respectively. On the surface of hypersthene, a noncrystalline weathered layer generally <0.01 μm in thickness, which has nearly the same composition as that of the parent matrix, was observed. This weathered layer was produced by precipitation of noncrystalline hydrous ferric oxide with partly developed to poorly crystallized Fe-Si-Mg rich phyllosilicate. The volcanic ash sample contains small amounts of noncrystalline secondary precipitates exhibiting three distinct morphologies: (1) aggregates of very fine fibers, (2) aggregates of fine fibers with crinkled fringes, and (3) spherical forms composed of roughly curled fringes. These noncrystalline precipitates are enriched in Al and Si and contain variable amounts of Fe, depending on their morphology. The Fe content of these materials decreases drastically in the sequence morphology 1 → morphology 2 → morphology 3, which is consistent with the transformation from Al-, Si-, and Fe-rich fine fibers to spherical halloysite by elimination of Fe from the fibers. These alterations of the volcanic ash took place in the crater of the Sakurajima volcano by interaction with near-neutral to weakly acidic solutions under relatively low-temperature conditions.

In vitro toxicology of respirable Montserrat volcanic ash

OBJECTIVESIn July 1995 the Soufriere Hills volcano on the island of Montserrat began to erupt. Preliminary reports showed that the ash contained a substantial respirable component and a large percentage...