Ash Layers Research Articles

Dynamic environmental conditions recorded by the trace fossil Teichichnus and event beds during deposition of the basal Vaca Muerta Formation in the central Neuquén Basin (Argentina)

The mud-dominated part of the basal Vaca Muerta Formation in the central Neuquén Basin accumulated mainly under dysoxic conditions as indicated by the absence of both fine lamination and large burrows, typical of anoxic and oxic conditions, respectively. Event beds and large, strata-bound concretions preserving a nearly uncompacted sediment fabric document rather discontinuous deposition, in particular as concretions must reside within the zone of carbonate supersaturation for a prolonged period of time to form. The mudrock hosts numerous ash layers. Among them is a bed up to 40 cm-thick that was deposited by storm-induced currents and later became calcified. It contains abundant, winding Teichichnus up to 220 cm-long. The trace producers partly reworked their own spreite and probably applied a gardening and sequestrichnial nutritional strategy (that is collecting and stowing of nutritional material in the burrow for later utilization). The spreite fill documents depositional processes that delivered argillaceous sediment and provided oxygen. The ash originally constituting the Teichichnus bed originated from the volcanic arc west of the basin. In contrast, the erosive surface limiting the Teichichnus bed is covered by mud, implying sediment delivery from the east or south where rivers entered the basin while the climate was (at least seasonally) humid, whereas aridity increased towards the north. Consequently, an estuarine circulation likely developed and prevailed during the initial transgression of the lower Vaca Muerta Formation while cold Palaeo-Pacific water flowed into the subsiding and expanding basin. Later, during prevailing dry climate, an anti-estuarine circulation was probably established.

Study on the effect of ash layer on flow and heat transfer in diesel particulate filter based on 3-D thermal lattice Boltzmann method

After the Diesel engine works for a long time, dense ash layer will be formed on the diesel particulate filter surface, which will increase the back pressure on the diesel particulate filter surface and seriously affect the normal operation of the diesel particulate filter. The diesel particulate filter micro-structure is generated by 3-D reconstruction technology. Moreover, the particle layer and ash layer are reconstructed by quartet structure generation set. The exhaust gas with a velocity of 0.05-0.25 m/s is introduced into the diesel particulate filter model. Under the condition of 873 K temperature field, the 3-D lattice Boltzmann method is used to explore the influence of the particle layer and ash layer accumulated in its micro-structure on its flow and heat transfer. The results show that with the accumulation of ash, the flow velocity in the diesel particulate filter increases with the decrease of porosity. The existence of ash layer increases the pressure difference between the inlet and outlet of the structure, and the pressure difference between the inlet and outlet of the structure increases with the increase of the air inlet speed. Under the same flow conditions, the heat transfer process of structures containing ash stratification is faster, and the highest temperature point moves forward accordingly. This has certain guiding significance for exploring the thermal load of ash containing diesel particulate filter structure.

A synthesis of Carboniferous stratigraphy in Xinjiang, Northwest China with emphasis on regional and global correlations

The Carboniferous is the most widely distributed system in the pre-Mesozoic strata of Xinjiang, Northwest China, and they are exposed in structurally independent units within various tectonic settings across the southwest Central Asian Orogenic Belt and Tarim Craton in Northwest China. According to the lithofacies associations and biotic assemblages, the Carboniferous successions of Xinjiang can be divided into 18 stratal regions, and each of these stratal regions may be further separated into several subregions in terms of lithology, biota, and geochronologic data. The depositional succession of each region is described on the basis of the key section. The marine fossils such as foraminifers (fusulinids), brachiopods, corals, and conodonts, as well as nonmarine fossils such as plants and pollens are reviewed in this study. Combined with the geochronologic data from the volcanic rocks and ash layers, a refined scheme of the Carboniferous successions in different regions across Xinjiang, Northwest China is obtained. The detailed and newly established stratigraphic framework of the Carboniferous strata could be very helpful for the regional and global stratigraphic correlations. It can also offer a new and reliable chronostratigraphic foundation for the comprehensive understanding of the tectonic evolution and petroleum exploration in Central Asia.

Laboratory Evaluation of Tundish Covering Powders and Rice Hull Ash on Cleanliness for a SAE 1055 Modified Steel

The continuous casting tundish is the last metallurgical reactor where molten metal flows before solidifying in the continuous casting mold. A tundish covering powder can be used for improving steel cleanliness; in this case it is named ‘active tundish slag’. The objective of this work is to evaluate, in laboratory, the effect of three kinds of tundish covering powders on cleanliness for a SAE 1055 modified steel - a Ca-aluminate, a Ca-Mg-aluminate, and an Al-silicate powder, analysing their interaction with rice hull ash. The forementioned materials were molten on liquid steel, representing different kinds of tundish covering powders which are used in the steel industry: a Ca-Mg-aluminate, an Al-silicate, and a Ca-aluminate. Experiments were performed with and without a top layer of rice hull ash, simulating industrial conditions. Distribution, density, and mean diameter of inclusions were measured through automated inclusion analyses. Through computational thermodynamics it was possible to evaluate deviation from saturation (considering Al2O3 and MgO from refractory) and slag viscosity. It can be stated that the Ca-aluminate tundish covering powder gives better results regarding cleanliness for the SAE 1055 modified steel under laboratory conditions.

정선 매둔동굴 출토 청동기시대 사람뼈 연구

At Jeongseon Maedun Cave Site, the Bronze Age human skeletons are almost completely restored and preserved in good condition. It is of great importance, as the Site shows the burial cave customs of a type of tomb that is little investigated in Korean peninsula.
 The burial cave comes under a mass tomb in which several individuals are buried, including at least three persons, adults and children. It may be a joint tomb (family tomb) judging from the aspect of excavation and the sex and age of the buried. In particular, human bones in Tomb No. 1 with the most remaining area were buried by burying aside above an ash layer that was intentionally built. The stone chamber is assumed to be a stone coffin, and burial goods include arrowhead and red burnished pottery.
 Based on the result of an analysis of sex and age, No. 1 is of a woman in her mid-30s to 50s; No. 2, of a late-middle-aged to elderly man; and No. 3, of a young child aged 3-6. Measurement of bones in No. 1 reveals that the height is about 151-156㎝ and the cranium type is classified to be high and long. High cranium type is unique characteristic of the inhabitants of the Korean peninsula like other ancient human skeletons; However, the narrow and long cranium type(hyperdolichocrany, the cranial index 66.9) can be differentiated from that. This morphometric characteristic is considered as an unique and inherent feature that the residents around Maedun Cave shared. It has high correlation in the cranium type and archaeological aspects with the Bronze Age human skeletons excavated in Hwangseok-ri, Jecheon. As for pathological features, porotic hyperostosis and cribra orbitalia were found in the cranium; oral cavity and periodontal diseases, in the upper jaw and teeth; and osteoarthritis in the spine and ribs. Lifestyles including diseases, health, and nutritional status could be inferred from such features. Furthermore, the stable isotope analysis, which is of a chemical analytic method of diet, reveals that the proportion of total animal protein consumed in the diet was low, whereas the intake of farm crops(C4 plant), such as millet, foxtail millet and broomcorn was high. This dietary characteristic corresponds with the results of Hwangseok-ri, Jecheon and Joongdo, Chuncheon, enabling the restoration of dietary life of central region residents of the Korean peninsula in the Bronze Age.

Palynological Characteristics and Volcanic Ash from Sediments of Chistoye Lake, Northern Priokhotye

Chistoye Lake (59° 32' N, 151° 48' E) is located 10 km from the northern coast of Taui Bay (Okhotsk Sea) in the central part of a tectonic depression that has been infilled with Paleogene and Neogene deposits. The lake originated as the result of glacial activity during the latest Pleistocene (MIS2). A 550-cm-long lacustrine sediment core was raised from Chistoye Lake using a piston sampler. The core is dominated by silt with layers of peat and sand at its base. The silt includes two tephra layers at 360-364 cm and 77-80 cm. The tephra layers have different geochemical, magnetic, and mineralogical properties. Volcanic ash like the lower tephra in the Chistoye core has been found in other lacustrine sites from the Upper Kolyma, Upper Indigirka, and Northern Priokhotye regions. Radiocarbon dating of organic remains that bracket this second tephra, corresponding to the lower tephra in Chistoye Lake, indicates an age of 7 650 ± 50 years ago, which is comparable with the age of the Kurile Lake - Iliyinskaya caldera forming eruption in Kamchatka. The younger tephra also has been noted in cores from other lakes in Northern Priokhotye and dated to 2 745 ± 10 years ago. A distinctive feature of this Late Holocene tephra is its high magnetic susceptibility. Extrapolation of a sedimentation rate based on the tephra ages suggests that the Chistoye record is approximately 11 700 years old. Palynological analysis of the Chistoye Lake material showed that all samples contain pollen redeposited from Neogene sediments (Picea sect. Eupicea, Tsuga, Tilia, Corylus, Juglans, Ulmus). These taxa can be easily discounted as contaminant, but other pollen types (e. g., Pinus subgen. Haploxylon, Betula, Alnus, Cyperaceae, Poaceae) are more problematic for interpreting the paleovegetation, because they represent plants that were present during the Holocene and/or the Late Pleistocene and during the Neogene. Nonetheless, the changes in the percentages of Sphagnum spores suggest a gradual increase in effective moisture during the Younger Dryas and Holocene. A multiproxy study of the sediments from Chistoye Lake, in conjunction with their palynological characteristics, shows the importance of analyzing magnetic properties to help determine the presence of tephra in the sediments. Volcanic ash layers in the lake sediments from northeastern Siberia are reliable chronostratigraphic markers that can supplement radiocarbon dates and improve the regional understanding of climate and vegetation changes during the Holocene.

Late Quaternary sediments from Barakar-Damodar Basin, Eastern India include the 74 ka Toba ash and a 17 ka microlith toolkit

The Youngest Toba Tuff (YTT, 74 ka ago) is considered as the product of one of the largest super-volcanic events in the Quaternary period, which possibly caused a disastrous effect on the climate and hominid habitation. Here, we report a rare occurrence of an ∼ 2 cm YTT ash bed in the Barakar-Damodar Late Quaternary sediments, Eastern India, and the Microlith toolkits that were found in the sedimentary deposits above the ash layer. The high silica content of the glass shards with bubble walls, blocky, rod-shaped structures, and pumice morphology, are similar to other YTT ash deposits. The sedimentary facies associated with the ash layer show a transition from lacustrine to fluvial depositional environments. Sedimentological, petrographical, mineralogical, geochemical, and magnetic properties suggest the ash was deposited in a lacustrine environment. Moreover, the discovery of the ash bed, the occurrence of in-situ Bovid species, and microlith assemblages in the Barakar-Damodar Valley add to our understanding of late Pleistocene depositional environments, hominin occupations, and possible local migration across eastern India during the Last Glacial Maximum (LGM) period.

MEASUREMENT OF THERMAL RADIATION OF MOXA PHYSIOTHERAPEUTIC REGIME

Thermal radiation from various sources is widely used in medical therapy procedures. Sources of artificial and natural origin are used to create thermal radiation. The latter are of the greatest interest, as they form a wide spectrum of radiation, most comparable to a person's own radiation. The use of wormwood cigars (mox) became widespread. With their help, sessions of one of the most popular methods of Chinese folk medicine, moxatherapy (burning, thermopuncture, "jiu" therapy) are conducted. The authors conducted studies of the thermal radiation of a wormwood cigar in the wavelength range of 800…1000 nm. "Qiaitiao" No. 6 cigars from the standard treatment set were used for experimental research.
 The purpose of the conducted research is to determine the power of thermal radiation of moxa and evaluate the dynamics of its changes during the course of a treatment session. A high-precision OM3-65 absorbing power wattmeter with an optoelectronic converter was used for measurements. Studies have shown that the maximum power of thermal radiation is formed immediately after the wormwood cigar begins to smolder. Its value is within (1.5...2.0) 10-4 W. When a cigar burns for 2.5 minutes, the intensity of heat radiation decreases by more than an order of magnitude. This is due to the fact that in the process of smoldering moxa, a layer of ash is formed between the burning and irradiation zones, which partially absorbs the flow of thermal radiation. In addition, during decay of fixed moxa, the irradiation zone gradually moves away from the irradiated surface.
 Removing the ash layer and placing the moxa at the previous distance leads to the restoration of the initial power level. Approximate expressions were obtained, which, based on experimental data, describe the change in the heat radiation power of a wormwood cigar.
 The features revealed during the study of the thermal radiation of the wormwood cigar will be useful for specialists engaged in practical thermotherapy and will contribute to increasing its effectiveness.

Clay mineralogy mediated by pH and chemical weathering intensity of Permian–Triassic boundary K-bentonites at Dongpan (Guangxi, South China)

Volcanic ash deposits of the Permian-Triassic (P-T) transition in South China, in addition to being associated with the Permian-Triassic boundary mass extinction, are useful marker beds for regional correlation of sedimentary strata. This study investigates the source(s) of P-T volcanic ash layers in South China by studying their clay mineralogy and geochemical characteristics in deep-marine facies at Dongpan. Mineralogically, the Dongpan deposits consist mainly of clay minerals and quartz, with small amounts of anatase and feldspar. C lay minerals in the volcanic ash layer are mainly composed of R1 mixed-layer illite/smectite (I/S) (56.2–74.8%), smectite (14–22.8%), kaolinite (5.4–27.3%) and illite (1.2–5.3%). The relatively high content of kaolinite and weak illitization of smectite at Dongpan differ from the features of clay-mineral assemblages in other contemporaneous deep-water facies. Our results indicate that strong chemical weathering in an acidic and oxidizing environment characterized by low K+/H+ ratios inhibited uptake of K+ in the interlayers of I/S clay minerals and, thus, illitization of smectite. We infer that weathering intensity rather than redox state was the primary influence on the rate of kaolinization of clay minerals in these deep-marine facies. The Dongpan section exhibits a uniform REE pattern, indicating a single and stable source of volcanic ash during the P-T transition. Trace-element and REE distribution patterns and mixed-layer I/S clay-mineral morphologies are consistent with the source of the volcanic ash at Dongpan being a nearby continent-margin volcanism.

Synthetic oxygen carrier C28 compared to natural ores for chemical looping combustion with solid fuels in 80 kWth pilot plant experiments

Chemical Looping Combustion (CLC) is a highly efficient CO2 separation technology with no direct contact between combustion air and fuel. A metal oxide is used as oxygen carrier (OC) in a dual fluidized bed to generate clean CO2. The use of solid fuels, especially biomass, is the focus of current research, because of the possibility of “negative” CO2-emissions. The OC is a key component, because it must meet special requirements for solid fuels, which are different to gaseous fuels. Most frequently naturals ores or synthetic materials are used as OC. Synthetic OC are characterised by higher reactivity at the expense of higher costs. For this reason, so far not so many experiments have been conducted on a larger scale with synthetic OC on solid CLC. This work deals with the synthetic perovskite C28 and investigating the suitability as oxygen carrier in an 80 kWth pilot plant for chemical looping combustion with biogenic fuels. The experiments show a significantly increased combustion efficiency of 99.6 % compared to natural ores and a major influence of the solid circulation rate on general performance, whereby carbon capture rates up to 98.3 % were reached. Furthermore, the role of the fuel reactor's counter-current flow column and its impact on better gas conversion was investigated. C28 suffered no deactivation or degradation over the experimental time, but first traces of ash layer formation, phase shifting and attrition of fines could be detected. The focus of further research should lie on long-term stability and reactivity for their high impact on the economic scale up of C28.

Long-term change of the eruption activities of Sakurajima volcano, Japan, inferred from the fallout tephra deposits

Stratigraphic analysis of fallout tephra deposits in and around a volcano provides a framework for understanding the long-term temporal change in the volcano’s activities. Here, we reconstruct the evolution of the volcanic activities of Sakurajima volcano based on reconstructed tephra stratigraphy by original field surveys, compilations of geological and archeological data, and new 14C dating. We define three eruption stages of Stage 1 (30–24 ka), Stage 2 (12.8–4.8 ka), and Stage 3 (4.5 ka–present), based on a major hiatus and shifting of the volcanic centers. Stages 2 and 3 are further subdivided according to the predominant mode of volcanic activity. Revised distribution of tephra deposits indicates that a total of 14.5 km3 (5.8 km3 dense rock equivalent) of fallout tephra has erupted from Sakurajima. Among them, Stage 2a (13–8 ka) produced the largest volume of tephra fallout deposits, suggesting that Sakurajima peaked in magma discharge during Stage 2a (2.9 km3/kyr) and then decreased rapidly toward Stage 2b (8–4.8 ka; 0.07 km3/kyr). The eruption of large-volume tephra deposits in Stage 2a, followed by the development of a thick volcanic ash layer in Stage 2b, indicates the eruption style shifted from explosive pumice eruptions in Stage 2a to ash-producing Vulcanian activity in Stage 2b, with decreasing magma discharge rate. Thick volcanic ash deposits covered by several fallout tephra deposits during Stage 3 also reflect a shift in activity from repeated Vulcanian explosions with lava effusions in Stage 3a (4.5–1.6 ka) to predominantly pumice eruptions during the historical period (Stage 3b) with an increasing magma discharge rate. The case study of Sakurajima presented here demonstrates that the combined analysis of the distribution, stratigraphy, and age of pumice fall layers with the lava and pyroclastic cone deposits on the volcanic edifice is a powerful tool for deciphering the growth history of complex stratovolcanoes.

Release characteristics of heavy metals in high-sulfur coal gangue: Influencing factors and kinetic behavior

High-sulfur coal gangue (HS-CG) is extremely unstable in the environment, releasing acid mine drainage with high concentrations of harmful heavy metals (HMs). The effects of HS-CG particle size, leaching solution pH, Fe3+ and acidophilic microorganisms on the release of HMs from the HS-CG and their kinetic behavior were studied using static leaching tests. The results showed that the smaller the particle size of HS-CG and the more acidic the leaching solution, the greater the release of HMs. As the chemical catalyst, the external addition of 300 mg/L Fe3+ can make the leaching amount of Fe, Mn, Cu, Zn, Ni, Cr reached 10,224.93, 93.88, 52.25, 11.56, 7.55, 2.97 mg/kg respectively, and the release of HMs was 1.36–2.60 times of the tests without the addition of iron. However, the concentration of Fe3+ above 800 mg/L promoted the production of jarosite on the surface of HS-CG, which led to decrease in the release of HMs. The HMs forms in HS-CG were different, while the effect of microorganisms on the leaching of Zn (54.99%) and Mn (52.35%) in the higher acid soluble fraction was more obvious, their leaching amount reached 87.21 and 107.58 mg/kg respectively. The kinetic analysis indicated that the rate-controlling step was mainly redox reaction at first, and then gradually controlled by the diffusion of ash layer. So, the kinetic equation controlled jointly by two rate-controlling stages has been proposed to describe the dissolution of HS-CG. This work help develop pertinent strategies for mine area remediation via controlling the HMs generation path.

An exploratory study into ash mobilization using lysimeters

Abstract Wildfires burn vegetation and leave the resultant organic and inorganic ash into the soil surface. Depending on the temperatures and burn durations, the quantity and type of ash can vary widely. Ash mobilization following wildfire is a topic of major concern, since it may result in contamination of surface water bodies within and downstream of the burnt areas. The present study aims to analyse the influence of black and white ash on surface runoff, leachate and total erosion and erosion of organic matter by running a field experiment along 6 weeks, using three replicate lysimeters with control soil, soil with addition of black ash and soil with addition of white ash. There was some suggestion but no statistical evidence that black ash reduced overland flow generation during the initial rainfall events, while black ash was found to increase sediment and organic matter losses by overland flow in a statistically significant manner. This was not during the initial rainfall events and, therefore, not directly related to the presence of a homogenous cover of a well-defined ash layer on the soil surface.

Provenance changes for mineral matter in the latest Permian coals from western Guizhou, southwestern China, relative to tectonic and volcanic activity in the Emeishan Large Igneous Province and Paleo-Tethys region

Recent studies have found that the provenance for water-transported sediments in some coal seams in the Late Permian and Early Triassic sequences from SW China have changed from mafic rocks of Emeishan Large Igneous Province (ELIP) to intermediate-felsic and alkaline igneous rocks from the ELIP and Paleo-Tethys convergent margins. However, the mechanism of provenance changes for mineral matter in the late Permian coals from SW China remains unclear. This paper uses the detailed mineralogical and geochemical characteristics of the latest Permian coal-bearing strata from the Huopu coal deposit in SW China to identify the potential detrital provenances of mineral matter.The mineralogy of the Huopu coals is dominated by kaolinite, quartz, and calcite. Fracture-filling kaolinite, calcite, quartz, anatase, as well as closely coexisting fracture-filling kaolinite, quartz, and chamosite, were possibly formed by multiple-stage solution injections. The Al2O3/TiO2 values, REY distribution patterns (REY, rare earth elements and Y), as well as Nb/Yb vs. Al2O3/TiO2 and Zr/TiO2 vs. Al2O3/TiO2 diagrams all indicate that the roof and floor sediments of the coal seam were sourced mostly from the ELIP high-Ti basalts. In contrast, the inorganic matter of the coals was derived from the Kangdian tops exposing (1) the Proterozoic meta-granitic complex; (2) the ELIP’s volcanic complex including, in addition to basalts, alkaline and intermediate-felsic lavas and small intrusions; and (3) volcanic ashes from the Paleo-Tethys convergent margins. The latest Permian sedimentation in the Huopu coal deposit is suggested to have been controlled by tectonic activity along the Xiaojiang Fault that separates the inner ELIP from the Western Yangtze Cratonic Basin (WYCB). This activity is characterized by repeated uplifts of the inner ELIP associated with some downward movements in the WYCB and vice versa. The ELIP uplift and WYCB subsidence may have led to intensive erosion of the ELIP basalts and marine transgression producing the clastic sediments, while the ELIP’s downward movement associated with some WYCB uplift may have promoted peat deposition and erosion of the Kangdian tops exposing both the ELIP intermediate-felsic volcanic rocks and the older meta-granitic complexes. Both sedimentation regimes were evidently accompanied by volcanic activity on the Paleo-Tethys convergent margins, but preservation of the volcanic ash layers was possible only during more quiescent peat-accumulation periods. The reduced detrital supply in these periods would result in a higher proportion of the intermediate-felsic pyroclastic debris disseminated in the coals.

Orbital-scale cyclicity and organic matter production in a Permian shallow mixed carbonate-siliciclastic system: Paraná Basin, Brazil

Mixed deposition in shallow seas is highly sensitive to climate variations and sea-level changes, which are the primary controls of high-frequency cycles in the stratigraphic record. The widespread Lower Permian mixed carbonate-siliciclastic succession of the Paraná Basin is composed of rhythmic organic-rich shale interbedded with dolostone. The strata are organized into several orders of magnitude of superimposed asymmetrical and symmetrical facies stacking patterns that developed in a broad epeiric sea, which extended over 106 km2 of Permian Gondwanan land. Detailed sedimentological and stratal stacking analysis allow the hierarchical organization to be identified in large-scale, medium-scale, small-scale, and elementary stacking patterns. The high-frequency depositional cycles compose four 3rd-order sequences. They comprise gray to black shale, marls, and peloidal to micritic dolostone. Due to the shallow water setting, the minimal available accommodation is responsible for the reduced cycle thickness and the overall mixed succession. The rhythmic deposits host highly productive hydrocarbon source rocks. Two widespread, thicker intervals of bituminous shale that develop during 3rd-order sequence transgression events are highly organic-rich oil shale (27 wt%). In addition, thin black shale laminae, which are interbedded with dolostone in high-frequency stacking patterns, are also rich in organic carbon (2–8 wt%). The alternation of high carbonate content and organic matter production was controlled by wet‒dry seasons and was related to total solar radiation maxima and minima. The total solar radiation maxima are translated into elevated carbonate precipitation due to shallower and hypersaline conditions. Total solar radiation minima induce freshwater discharge in shallow and hypersaline environments during wet stages, resulting in water column stratification. The occurrence of kerogen types III and IV, a high gammacerane index, variable Pr/Ph ratios, and C35 homohopane indices indicate this condition. In addition, the input of nutrient-rich terrigenous sediments favor algal blooms, enhancing anoxia in the bottom water, which is responsible for the organic-rich shale facies, as indicated by kerogen types I and II, high hydrogen index values, high C27/C29 sterane ratios, and higher β-carotane values. Based on the hierarchical organization and previous U–Pb SHRIMP zircon ages of volcanic ash layers, it is possible to correlate the observed succession with the global sea-level curve. A time span of 8.0 Ma is assessed for the Irati Sea, with an average of 2.7 Ma for the large-scale cycles. Furthermore, the high-frequency patterns that are compatible with the precession and eccentricity of the short (±100 ka) and major (±400 ka) periodicities of the Earth's orbit are estimated to be 26.6 ka, 135.5 ka, and 400 ka. The high-frequency cycles of organic-rich shales and carbonate that are deposited over thousands of years under long-term sea-level changes and are correlated along the basin suggest climatic control driven by the Earth's orbital perturbation, which is possible in the Milankovitch frequency band.

Role of surface morphology on bed material activation during indirect gasification of wood

Olivine and alkali-feldspar were utilized in separate campaigns in an indirect dual fluidized bed gasification campaign with woody biomass as fuel. After three days, both bed materials were reported to be active towards tar removal and exhibited oxygen-carrying abilities and had formed an ash layer consisting of an outer ash deposition layer and an inner interaction layer.X-ray microtomography analysis concluded that a preferred deposition of ash happens onto convex regions of the bed particles, which results in an increase in thickness of the ash layer over convex regions. This effect is most pronounced for the outer layer which is a product of ash deposition. The inner layer exhibits a homogeneous thickness and is probably formed by interaction of Ca from the outer layer with the particles. Transmission electron microscopy revealed the presence of Fe and Mn on the surface of the particles in a solid solution with Mg. The oxygen-carrying effect which is found for aged particles is therefore attributed to the presence of Fe and Mn on the surface of aged particles. Alkali were found on the surface of both particles which are likely contributing to the catalytic activity of the material towards tar removal.

Impact of ash layer retention on heat transfer in piles of vegetation and structure firebrands

The study of firebrands has been of great interest due to the growing threat of fires along the wildland-urban interface (WUI). In previous studies, piles of smoldering firebrands from dowels were found to produce higher heat fluxes than those from branches of the same wood species and geometry. In this study, the difference in burning behavior and heat transfer between these two types of smoldering firebrands are explored through experiments and models, using dowels to broadly represent structure fuels and branches for vegetation fuels. A distinct ash layer was observed in the vegetation firebrands that was not present in the structure firebrands. The deposited ash reduces the mass transport of oxygen within the pile which reduces the heat flux to the surface. In piles of ten, structure firebrands produced higher heat fluxes than vegetation firebrands. A 2D RANS model and an analytical burning model were used to demonstrate the impacts of the ash layer on the total burn time, the heat flux, and the surface temperature of a single firebrand by replicating results from the experiments.

Interpreting the mammal deposits of Cloggs Cave (SEAustralia),GunaiKurnaiAboriginal Country, through community‐led partnership research

AbstractPalaeontological animal bone deposits are rarely investigated through research partnerships where the local First Nations communities have a defining hand in both the research questions asked and the research processes. Here we report research undertaken through such a partnership approach at the iconic archaeological site of Cloggs Cave (GunaiKurnai Country, East Gippsland), in the southern foothills of SE Australia's Great Dividing Range.A new excavation was combined with detailed chronometric dating, high‐resolution 3D mapping and geomorphological studies. This allowed interpretation of a sequence of stratigraphic layers spanning from a lowermost excavated mixed layer dated to between 25,640 and 48,470 cal BP, to a dense set of uppermost, ash layers dated to between 1460 and 3360 cal BP. This long and well‐dated chronostratigraphic sequence enabled temporal trends in the abundant small mammal remains to be examined.The fossil assemblage consists of at least 31 taxa of mammals which change in proportions through time. Despite clear evidence that the Old Ancestors repeatedly carried vegetation into the cave to fuel cool fires (no visible vegetation grows in Cloggs Cave), we observed little to no evidence of cooking fires or calcined bone, suggesting that people had little involvement with the accumulation of the faunal remains. Small mammal bones were most likely deposited in the cave by large disc‐faced owls,Tyto novaehollandae(Masked Owl) orTyto tenebricosa(Sooty Owl).Despite being well dated and largely undisturbed, the Cloggs Cave assemblage does not appear to track known Late Quaternary environmental change. Instead, the complex geomorphology of the area fostered a vegetation mosaic that supported mammals with divergent habitat preferences. The faunal deposit suggests a local ancestral landscape characterised by a resilient mosaic of habitats that persisted over thousands of years, signalling that the Old Ancestors burned landscape fires to encourage and manage patches of different vegetation types and ages within and through periods of climate change.Read the freePlain Language Summaryfor this article on the Journal blog.

Uncertainty-bounded estimates of ash cloud properties using the ORAC algorithm: application to the 2019 Raikoke eruption

Abstract. Uncertainty-bounded satellite retrievals of volcanic ash cloud properties such as ash cloud-top height, effective radius, optical depth and mass loading are needed for the robust quantitative assessment required to warn aviation of potential hazards. Moreover, there is an imperative to improve quantitative ash cloud estimation due to the planned move towards quantitative ash concentration forecasts by the Volcanic Ash Advisory Centers. Here we apply the Optimal Retrieval of Aerosol and Cloud (ORAC) algorithm to Advanced Himawari Imager (AHI) measurements of the ash clouds produced by the June 2019 Raikoke (Russia) eruption. The ORAC algorithm uses an optimal estimation technique to consolidate a priori information, satellite measurements and associated uncertainties into uncertainty-bounded estimates of the desired state variables. Using ORAC, we demonstrate several improvements in thermal infrared volcanic ash retrievals applied to broadband imagers. These include an improved treatment of measurement noise, accounting for multi-layer cloud scenarios, distinguishing between heights in the troposphere and stratosphere, and the retrieval of a wider range of effective radii sizes than existing techniques by exploiting information from the 10.4 µm channel. Our results indicate that 0.73 ± 0.40 Tg of very fine ash (radius ≤ 15 µm) was injected into the atmosphere during the main eruptive period from 21 June 18:00 UTC to 22 June 10:00 UTC. The total mass of very fine ash decreased from 0.73 to 0.10 Tg over ∼ 48 h, with an e-folding time of 20 h. We estimate a distal fine ash mass fraction of 0.73 % ± 0.62 % based on the total mass of very fine ash retrieved and the ORAC-derived height–time series. Several distinct ash layers were revealed by the ORAC height retrievals. Generally, ash in the troposphere was composed of larger particles than ash present in the stratosphere. We also find that median ash cloud concentrations fall below peak ash concentration safety limits (< 4 mg m−3) 11–16 h after the eruption begins, if typical ash cloud geometric thicknesses are assumed. The ORAC height retrievals for the near-source plume showed good agreement with GOES-17 side-view height data (R=0.84; bias = −0.75 km); however, a larger negative bias was found when comparing ORAC height retrievals for distal ash clouds against Cloud-Aerosol Lidar with Orthogonal Polarisation (CALIOP) measurements (R=0.67; bias = −2.67 km). The dataset generated here provides uncertainties at the pixel level for all retrieved variables and could potentially be used for dispersion model validation or be implemented in data assimilation schemes. Future work should focus on improving ash detection, improving height estimation in the stratosphere and exploring the added benefit of visible channels for retrieving effective radius and optical depth in opaque regions of nascent ash plumes.

A waste heat exchanger fly ash particle deposition model with dynamic mesh and random function method

The fly ash particle deposition in the heat recovery process of the heat exchanger is an urgent issue that must be addressed. In this work, the particle deposition model is improved using the dynamic mesh technology and random function method. We simulated and predicted the fouling morphology and particle size distribution of the fly ash layer using the deposition characteristics of particles of various sizes. The results indicated that when dynamic mesh technology is adopted, the tube wall's boundary will be deformed geometrically with the deposition of particles, allowing the changes in the fouling morphology to be expressed more effectively. Under this study conditions, the particle deposition mass on the windward and leeward sides of the tube increased initially and then decreased with the particle size increased. When particles of different sizes are mixed, the first layer of particles accelerates the deposition of subsequent particles, and the first layer of particles is generally composed of particles of small size.