Coarse Quartz Research Articles

A Comparative Study of Anionic and Cationic Collector in Microbubble-Assisted Flotation for Coarse Quartz Particle: Performance and Adsorption

Recent studies have suggested that using microbubbles to assist in coarse particle flotation has some advantages. However, how the type of collector affects the recovery of coarse particles under microbubbles still needs to be clarified. This study compared the performance and adsorption characteristics of anionic (sodium oleate - NaOL) and cationic (dodecylamine - DDA) collector environments for microbubble-assisted flotation of coarse quartz particles. A two-factorial level and Box-Behnken techniques were used for statistical design for screening and characterizing the performance. The flotation process utilizing NaOL and DDA was not significantly affected by froth depth. In the presence and absence of microbubbles, the performance of DDA surpassed that of NaOL; therefore, the average recovery of the cationic collector was more than 10% higher than that of the anionic collector. Contact angle analysis revealed that NaOL measured approximately 70° while DDA measured around 90°. DDA was adsorbed more significantly than NaOL at the same collector concentration. Zeta potential was more sensitive to DDA; increasing both collector concentrations also increased the value of zeta potential. FT-IR and EDX analyses showed that DDA and NaOL were chemically adsorbed onto quartz. Overall, this study demonstrates that DDA outperformed NaOL in the presence and absence of microbubbles during the flotation of coarse quartz particles.

Pottery Production Changes During the Transition from Byzantine to Umayyad Rule

Pottery is the most affected tool by the changes in human societies; this is due to its flexibility during forming. In order to estimate the effect of the transition of inhabitants of the urban center of Umm Qais (Gadara), north Jordan, from Byzantine (Christianity) to Umayyad (Islam) rule on pottery production traditions, a total of 29 cooking pots and sherds of pottery jars were selected. The samples were dated according to stratigraphy, archaeological context, and parallel examples to the proposed periods. The samples were investigated following the typological and archaeometric approaches. The raw materials and firing technology of the pottery during the two periods were determined following chemical and mineralogical methods using petrography, XRD, ED-XRF, and EDX-SEM techniques. The results revealed that many styles and forms of pottery continued to be produced and some new styles emerged at the urban center of Gadara. Technically, the potters inherited the knowledge of selecting the available raw materials and firing conditions of pottery during the Byzantine and Umayyad periods. During these periods, Umm Qais potters used the local raw materials—non-calcareous ferruginous illite clays mixed with medium to high amounts of coarse quartz grains and fired at temperatures around 1000° in an oxidizing atmosphere to produce cooking pots. They used the available medium to highcalcareous ferruginous illite clays and fired them at temperatures between 850° and 950° in an oxidizing atmosphere to produce the jars. Importing fine fabric jars and cooking pots during the seventh century from Jarash are indicated too. Thus, the types and forms of everyday use pottery were more affected by the political and religious changes than the technical aspects.

The variation of particle concentration with height of wind-blown coral sand

Wind-blown coral sand movement is common in the marine coral sand island environment but received much less research attention compared to desert and coastal sands. We used the particle image velocimetry technique with wind tunnel experiments to determine the decay trends of the particle number density, nominal particle area density, and actual particle area density with height for wind-blown coral sands from the South China Sea. Then, a new morphology factor FM that consists of volume V, density ρs, drag coefficient CD, and projected area A of coral sands, was defined to evaluate the influences of particle characteristics on wind-blown sand movement and the results were compared with those of quartz sands from an inland desert. We found that the average FM of coral sands is more comparable to that of coarse quartz sands than smaller size groups. Coral sands tend to move nearer the surface during aeolian processes compared to smaller quartz ones due to their larger FM. The decay rate of particle number density of coral sands with height is similar to that of coarse (0.8–1 mm) quartz sands, but significantly larger than that of smaller quartz ones. The decay rate of the actual particle area density of coral sands with height is larger than that of their nominal particle area density, so that significant deviations may exist if a fixed particle size and spherical shape are assumed to study wind-blown particle movement. The present work contributes to understand the effect of particle characteristics on the wind-blown sand movement from a physical mechanism perspective for both desert quartz sands and marine coral sands.

Properties of cement raw meals used as sorbents in a calcium looping process

Calcium looping (CaL) is a promising carbon capture and storage (CCS) technology that has the potential to significantly reduce CO2 emissions in cement production. Integrating CaL with cement production provides a viable solution to the high CO2 emissions generated during the calcination process. This study examines the behavior of two industrial cement raw meals from different sites (A-RM and B-RM) under CaL conditions, focusing on phase composition, particle size distribution, and clinker phase evolution up to 1450 °C. Calcination and CaL experiments were conducted in a CO2-rich atmosphere, with materials characterized using quantitative X-ray diffraction (Q-XRD) and high-temperature X-ray diffraction (HT-XRD). The results showed that both raw meals absorbed similar amounts of CO2 during the cyclic CaL experiments. A-RM formed C2S and other silicates, while B-RM retained more free CaO due to a less effective reaction with coarser quartz (SiO2) particles. HT-XRD revealed delayed clinker-phase evolution in the 1000–1400 °C range in CaL-treated raw meals. However, CaL-treated raw meals achieved low free CaO at 1450 °C, suggesting that optimal kiln conditions can produce the desired phase composition. These findings indicate that integrating CaL-treated raw meals into cement production requires careful optimization of operational parameters to maintain clinker quality and minimize energy consumption. Further research should focus on improving the efficiency and reactivity of CaL-treated raw meals to enhance their suitability for industrial cement production.

Amine-coated nanobubbles-assisted flotation of fine and coarse quartz

This study investigates the role of alkyl ether monoamine-coated nanobubbles (NBs) in assisting the flotation process of quartz across various particle sizes, on a bench scale. Experiments were conducted in a mini lab column utilizing a consortium of bubble sizes: D32 = 1200 μm for macrobubbles and D32 = 180–220 nm for amine-coated NBs. The study revealed that an increase in amine-coated NBs correlates well with a decrease in the air/solution’s interfacial tension caused by the ether amine at less than 68 mN m−1. True flotation recoveries with varying amine/g quartz, where the collector-frother amine may be amine-coated NBs alone or assisted by NBs generated in pure water, were compared with blank tests, in the absence of NBs. The flotation study evaluated size-to-size fractions from fine (−20 µm) to coarse (up to 150 µm) particles and their mixtures. In addition, the work extended to explore the behavior of the “super” coarse quartz from 150 µm up to 1000 µm. The results highlighted a clear dependence on the particle size, with NBs improving recoveries in all fractions, especially the difficult-to-treat ultrafine/fine and coarse quartz. Recovery results exceeded 90 % in all fractions (isolated or in mixtures) at a high rate with the amine-coated NBs. The mechanisms proposed improved flotation performance attributed to the high numerical concentrations of NBs (at least 2–3 × 1010 NBs per gram of quartz) rapidly attaching to quartz surfaces, serving as “seeds” for the adhesion of larger bubbles generated in conventional flotation cells. This interaction facilitates the formation of lightweight, cluster-like aggregates that swiftly rise to the column’s surface. Notably, larger quartz particles (+355 µm) form the bigger hydrophobic and buoyant clusters, leading to their rapid levitation and effective phase separation, with over 95 % separation efficiency. This innovative technique’s significance, outcomes, and potential scalability are thoroughly discussed, highlighting its promising applicability in diverse mineral and ore flotation systems, particularly those containing quartz and silicates.

Flood events in the lower reaches of the Yellow River: OSL and radiocarbon dating on the Anshang site

The lower reaches of the Yellow River have witnessed numerous episodes of flooding and considerable shifts in its course. Examining flood records within the Yellow River basin offers invaluable insights into ancient human settlements, agricultural practices, trade routes, and technological advancements of ancient Chinese civilizations. However, dating these fluvial sediments poses a considerable challenge due to either the scarcity of organic material for radiocarbon (14C) dating or the potential incomplete bleaching of sediments for optically stimulated luminescence (OSL) techniques. This study focused on the Anshang site located in Henan Province, we obtained OSL ages from distinct grain size fractions of quartz and cross-verified them with independent acceleration mass spectrometry (AMS) 14C ages. The findings revealed that both coarse quartz grains (CG) and medium quartz grains (MG) underwent complete bleaching in silt-dominated flood deposits and shallow lacustrine deposits. Conversely, the OSL ages of CG and MG quartz were notably overestimated by approximately 3–6 ka in silty clay-dominated flood deposits. Upon comparing the OSL ages with AMS 14C ages, it was evident that bulk organic matter AMS 14C ages aligned with CG OSL ages in shallow lacustrine deposits, but they appeared older than CG OSL ages in flood deposits. However, the AMS 14C ages from plant demonstrated good consistency. Consequently, we successfully identified flood-lacustrine sediments dating back to approximately ∼13 ka, ∼8–3 ka, ∼2.6 ka, ∼1 ka, and the last few hundred years, aligning well with historical documentation and earlier research. The regional evidence presented herein enhances our understanding of the applicability of OSL dating and AMS 14C dating in fluvial-lacustrine sediments. Armed with these new ages, we constructed a reference chronology for archaeological localities situated in the fluvial sediments of the lower reaches of the Yellow River.

Archaeometric investigations of the Late Roman Period red slip ware from Caesarea Germanicia (Kahramanmaraş, Southeastern Anatolia)

AbstractIn the present study, red slip wares excavated from the ancient city of Germanicia (modern Kahramanmaraş, Southeastern Anatolia) were subjected to an archaeometric analysis. A multi‐analytical approach was employed, including stereomicroscopy, optical microscopy, XRPD, SEM‐EDS, and XRF to explore the mineralogical and chemical compositions of the samples. Based on both archaeological and archaeometric criteria, the samples were classified into three main categories: African, Phocaean, and Sagalassos red slip wares. The African red slip wares were characterized by an abundance of coarse quartz inclusion, accompanied by lesser quantities of plagioclase and mica. The Phocaean red slip wares primarily consisted of quartz, feldspar, and mica. In contrast, the Sagalassos red slip wares featured a groundmass rich in quartz, mica/biotite, hematite, and opaque minerals. Thermoanalytical data indicated that all samples were fired at temperatures between 800 and 900°C. The results suggest that red slip wares found at Germanicia were not manufactured using local available clay sources but rather originated from different regions. This evidence further provides that Germanicia was actively involved in trade networks and interacted with various ancient urban centers, such as Africa, Phocaean, and Sagalassos, during the Late Roman Period, between the fourth and fifth centuries AD.

Enhancing Soil Resilience: Bacterial Alginate Hydrogel vs. Algal Alginate in Mitigating Agricultural Challenges.

Erosion and tillage changes negatively the soil physical structure, which directly impacts agricultural systems and consequently food security. To mitigate these adverse modifications, different polymeric materials from synthetic and natural sources, have been used as soil conditioners to improve the hydro-mechanical behavior of affected soils. One of the most interesting and used natural polymers is the alginate hydrogel. Although commercially available alginate hydrogels are primarily sourced from algal, they can also be sourced from bacteria. The gelation capacity of these hydrogels is determined by their molecular properties, which, in turn, are influenced by the production conditions. Bacterial alginate hydrogel production offers the advantage of precise control over environmental conditions during cultivation and extraction, thereby maintaining and enhancing their molecular properties. This, in turn, results in higher molecular weight and improved gelation capacity. In this study, we compared the effects of bacterial alginate (BH) and algal alginate (AH) hydrogels over the mechanical, hydraulic, and structural behavior of coarse quartz sand as a model soil. Mechanically, it was observed that the treatment with the lowest concentration of bacteria alginate hydrogel (BH1) reached higher values of yield strength, Young's modulus (E), shear modulus (G) and strain energy (U) than those treatments with algal alginate hydrogel (AH). Furthermore, the increase in the aggregate stability could be associated with the improvement of mechanical parameters. On the other hand, a greater water retention capacity was observed in the BH treatments, as well as a greater decrease in hydraulic conductivity with respect to the AH and control treatments. All these changes could be explained by the formation of bridge-like structures between the sand particles and the hydrogel, and this alteration may result in a shift in the mechanical and wettability characteristics of the treated soils. Finally, our findings emphasize the superior impact of bacterial alginate hydrogel on enhancing the mechanical and hydraulic properties of coarse quartz sand compared to traditional algal alginate. Besides, the use of bacterial alginate hydrogel could be useful to counteract erosion and water scarcity scenarios in agricultural systems.

Study of new commercial collectors for the recovery of coarse quartz particles in iron ore flotation

Currently, a small range of commercial collectors is available for the use in reverse iron ore flotation at Vale. This input represents a considerable unit cost, being essential for the concentration of low content itabiritic iron ores. The present work evaluated the reverse cationic flotation of an itabiritic ore with low iron content (39.6 % Fe) from the Iron Quadrangle (BR) in bench scale tests, focusing on the use of new collectors to remove coarse quartz. The sample presents 19% of its particles as oversize in the 0.150 mm sieve. The poor flotation of coarse quartz particles (>0.150 mm) causes significant problems in various iron ore flotation circuits by contaminating the concentrate. The study evaluated the performance of 10 new collectors from the etheramine family with different degrees of neutralization and at different collector dosages. The flotation process variables were set as industrially practiced at the Cauê iron ore plant (BR). In tests varying the specific collector dosage, the non-neutralized etheramines showed improved performance compared to the current 50% neutralized etheramine used in the plant, achieving industrial targets: concentrate SiO2 content rate lower than 4.5% (1.4%), tailings iron content lower than 23% (18.94%), metallurgical recovery greater than 66% (74,8%), and Gaudin Selectivity Index greater than 6.6 (10.5). The 0.150 mm oversize in the concentrate, mostly coarse quartz particles, was reduced from 5.7% down to 1.2%, indicating the potential for the industrial application of non-neutralized etheramines in the recovery of coarse quartz.

Morphogenesis of Balkhania balkhanica Mamontova, 1966 (benthic foraminifera) from Lower Cretaceous successions along the northern Tethyan margin (NE and Central Iran): Time and environmental control

Among large benthic foraminifera, Balkhania genus is one of the most valuable taxon that has been used to better constrain the biostratigraphy of the Lower Cretaceous successions along the Tethyan carbonate platforms. The species Balkhania balkhanica is considered as biostratigraphical index for the Barremian-Aptian interval. This study is focused on the B. balkhanica-bearing intervals of the Tirgan and Taft formations from two sections, deposited on the carbonate platform of the Iranian Tethyan margin (Kopet-Dagh Basin, NE Iran and Yazd Block, Central Iran). The age of the studied sections has already been determined in previous works. In present research, morphology and stratigraphical and ecological distribution of the recorded specimens are interpreted. According to the morphological changes, two morphotypes of B. Balkhanica have been introduced. Small-size morphotype is recorded in the Upper Valanginian to Upper Hauterivian interval of the Tirgan Formation. The Upper Barremian to Lower Aptian successions are mostly associated with larger sized specimens having a coarse quartz agglutinated wall, and named arenaceous morphotype. Their wall is in contrast to the Turkmenistan type specimens having a calcite microgranular-agglutinated wall. Inherent evolutionary factor suggests an evolutionary trend of this species from smaller to larger sized specimens during the Late Valanginian to Early Aptian. A preliminary study of the depositional environment also indicates an environmental control for this type of morphological variation. It suggests that the small-size morphotype mostly occurred in an under-stress shallow-water environment, while the larger size morphotype was associated with deeper and more stable outer-shelf environments.

How to measure the ESR intensity of the Al centre in optically bleached coarse quartz grains for dating purpose?

The ESR intensity of the Al signal has been traditionally extracted from the measurement of the amplitude between the top of the first peak and the bottom of the last peak from g = 2.0185 to g = 1.9928. However, a recent study by Kabacińska and Timar-Gabor (2022) showed the limitations of this method. As a follow-up, we investigated and compared various Al signal intensity extraction methods to evaluate their impact on the De estimation of several coarse-grained quartz samples (100–200 μm) from Early Pleistocene to modern-age deposits.In particular, we tested the potential of using the area of the Al signal near g = 2.0603, as it is theoretically free of any major interfering signals. However, our results show that the extraction methods related to this area do not offer any substantial advantages over the traditional method in the case of coarse-grained samples. Instead, measurement of the ESR intensity is more time consuming, and resulting dose response curves are more scattered. Actually, most Al intensity extraction methods tested in this study return equivalent dose (De) estimates (as well as bleaching coefficient values) within error, suggesting that the interfering signals do not seem to strongly bias the ESR dose evaluation in those coarse-grained quartz samples. This outcome provides additional support in favor of the use of the traditional method. However, the significant inter-sample variability observed in our study nevertheless shows the necessity to extend this investigation to a larger number of samples of various grain sizes, origins and chronologies in order to identify more meaningful patterns on a larger scale.

Investigation of the provenance of Okinose sand using ESR signals of quartz in granite and granodiorite around Osaka Bay.

A submarine dune on the seabed in the Okinose area of Osaka Bay, Japan, was found to be composed mainly of coarse quartz sand. To investigate the provenance of this sand, quartz extracted from granite and granodiorite sources near Osaka Bay was measured by electron spin resonance; E1', Ti-Li and Al centres were detected in all samples. Although the heat-treated E1' centre was found not to be useful for the present provenance study, the ratio of the signal intensities of the Ti-Li centre to the Al centre classified the potential sources into two groups, based on their likelihood. The results indicated that granite and granodiorite from Awaji Island as well as Rokko granite could be the source of the Okinose sand.

The effect of microbubbles on coarse particle anionic flotation: analysis and optimization

Since the grinding and chemical reagents required for flotation are expensive, coarse particle flotation reduces grinding costs and makes the subsequent process more accessible and cheaper. Recent studies suggest that the flotation of coarse particles using microbubbles has some advantages. However, a thorough analysis of the effectiveness of various flotation parameters and the impact of their interactions on the recovery of coarse particles in the presence and absence of microbubbles has yet to be fully understood. In the current study, the two-level factorial and Box-Behnken experimental designs were performed to characterize, assess, and optimize the implications of seven numerical (sodium oleate, collector; calcium oxide, activator; MIBC, frother; impeller speed; froth depth; pulp concentration; fine particles) and one categorical (microbubbles) independent parameters on the coarse quartz particles. Characterization revealed that froth depth did not significantly affect the flotation recovery of coarse particles in the mechanical laboratory cell. The effects of the variables in the presence of microbubbles revealed that sodium oleate and impeller speed significantly impacted recovery, followed by calcium oxide and fine particles, both of which had a medium influence, and MIBC and pulp concentration, which had a minimal impact. The recovery of coarse particles increased by 92.714% when microbubbles were used, compared to the estimated maximum recovery under ideal conditions of 62.258% without them. From this, it can be concluded that a high coarse particle flotation recovery is possible by optimizing the hydrodynamic conditions and the chemical environment using microbubbles.

Modeling dust mineralogical composition: sensitivity to soil mineralogy atlases and their expected climate impacts

Abstract. Soil dust aerosols are a key component of the climate system, as they interact with short- and long-wave radiation, alter cloud formation processes, affect atmospheric chemistry and play a role in biogeochemical cycles by providing nutrient inputs such as iron and phosphorus. The influence of dust on these processes depends on its physicochemical properties, which, far from being homogeneous, are shaped by its regionally varying mineral composition. The relative amount of minerals in dust depends on the source region and shows a large geographical variability. However, many state-of-the-art Earth system models (ESMs), upon which climate analyses and projections rely, still consider dust mineralogy to be invariant. The explicit representation of minerals in ESMs is more hindered by our limited knowledge of the global soil composition along with the resulting size-resolved airborne mineralogy than by computational constraints. In this work we introduce an explicit mineralogy representation within the state-of-the-art Multiscale Online Nonhydrostatic AtmospheRe CHemistry (MONARCH) model. We review and compare two existing soil mineralogy datasets, which remain a source of uncertainty for dust mineralogy modeling and provide an evaluation of multiannual simulations against available mineralogy observations. Soil mineralogy datasets are based on measurements performed after wet sieving, which breaks the aggregates found in the parent soil. Our model predicts the emitted particle size distribution (PSD) in terms of its constituent minerals based on brittle fragmentation theory (BFT), which reconstructs the emitted mineral aggregates destroyed by wet sieving. Our simulations broadly reproduce the most abundant mineral fractions independently of the soil composition data used. Feldspars and calcite are highly sensitive to the soil mineralogy map, mainly due to the different assumptions made in each soil dataset to extrapolate a handful of soil measurements to arid and semi-arid regions worldwide. For the least abundant or more difficult-to-determine minerals, such as iron oxides, uncertainties in soil mineralogy yield differences in annual mean aerosol mass fractions of up to ∼ 100 %. Although BFT restores coarse aggregates including phyllosilicates that usually break during soil analysis, we still identify an overestimation of coarse quartz mass fractions (above 2 µm in diameter). In a dedicated experiment, we estimate the fraction of dust with undetermined composition as given by a soil map, which makes up ∼ 10 % of the emitted dust mass at the global scale and can be regionally larger. Changes in the underlying soil mineralogy impact our estimates of climate-relevant variables, particularly affecting the regional variability of the single-scattering albedo at solar wavelengths or the total iron deposited over oceans. All in all, this assessment represents a baseline for future model experiments including new mineralogical maps constrained by high-quality spaceborne hyperspectral measurements, such as those arising from the NASA Earth Surface Mineral Dust Source Investigation (EMIT) mission.

Hydrothermal synthesis of hydrated layered polysilicate magadiite from coarse quartz glass blocks

Hydrothermal synthesis of hydrated layered polysilicate magadiite from coarse quartz glass blocks

Variation of Flow Hydrodynamic Parameters and Prediction of Particle Separation Indices in the Spiral Concentrator with the Regulation of Pitch-Diameter Ratio

The pitch-diameter ratio is an important design indicator affecting the separation performance of spirals. Based on the numerical simulation method, this paper systematically investigated the variation of flow hydrodynamic parameters in the spiral concentrator with the regulation of the pitch-diameter ratio. The radial distribution and variation trend of hematite and quartz particles with different particle sizes are further analyzed. Additionally, the separation indices of hematite and quartz with different particle size combinations were predicted. The results show that the tangential velocity, maximum radial velocity, velocity shear rate, and Reynolds number of fluid in each region decrease with the increase of the pitch-diameter ratio. The range of laminar flow gradually expands as the pitch-diameter ratio increases. There are significant differences in depth of water, ratio of inward and outward flows, and secondary flow velocity in different regions. Some flow hydrodynamic parameters at the inner trough reach relative equilibrium at a pitch-diameter ratio of 0.675. Hematite and quartz particles form a selective distribution in the trough surface, which comprehensively reflects the density effect, particle size effect, following flow effect of fine particles, and the effect of interstitial trickling of high-density fine particles. Fine hematite and coarse quartz form a large amount of misplaced material, and there is a corresponding mixing area. With the increase in pitch-diameter ratio, coarse and fine hematite particles migrate inward and outward, respectively. With the increase in pitch-diameter ratio, the misplaced amount of quartz on the inner trough decreases, but the outward migration distance of coarse quartz is smaller. Increasing the pitch-diameter ratio is beneficial to the separation of combined feedings of coarse hematite and quartz but unfavorable to that of fine hematite and quartz. The maximum separation efficiency of coarse hematite and fine quartz can reach 85.74%, and the iron grade of the inner product can reach 65.96% when the pitch-diameter ratio is 0.675 and the splitter location is 115 mm. The changing trend of separation indices in this feeding is closely related to the variation of fluid parameters and the change in the radial distribution of single mineral particles. The research results can provide references for the structural design of spirals, the selection of feed particle size, and the adjustment of splitter location.

Soil pore structure mediates the effects of soil oxygen on the dynamics of greenhouse gases during wetting–drying phases

The timing and magnitude of greenhouse gas (GHG) production depend strongly on soil oxygen (O2) availability, and the soil pore geometry characteristics largely regulate O2 and moisture conditions relating to GHG biochemical processes. However, the interactions between O2 dynamics and the concentration and flux of GHGs during the soil moisture transitions under various soil pore conditions have not yet been clarified. In this study, a soil-column experiment was conducted under wetting–drying phases using three pore-structure treatments, FINE, MEDIUM, and COARSE, with 0 %, 30 %, and 50 % coarse quartz sand applied to soil, respectively. The concentrations of soil gases (O2, nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4)) were monitored at a depth of 15 cm hourly, and their surface fluxes were measured daily. Soil porosity, pore size distribution, and pore connectivity were quantified using X-ray computed microtomography. The soil O2 concentrations were found to decline sharply as soil moisture increased to the water holding capacities of 0.46, 0.41, and 0.32 cm cm−3 in the FINE, MEDIUM, and COARSE, respectively. The dynamic patterns of the O2 concentrations varied across the soil pore structures, decreasing to anaerobic in FINE (<0.01 %) and MEDIUM (0.02 %), and to hypoxic (4.42 %) in COARSE. Correspondingly, the soil N2O concentration was the highest in FINE (101 μL L−1) and the lowest in COARSE (10 μL L−1), whereas the highest surface N2O flux was observed in MEDIUM (131 μg N m−2 h−1). As soil CO2 concentrations declined, CO2 fluxes increased from FINE to MEDIUM to COARSE. Most pores of FINE, MEDIUM, and COARSE were 15–80 μm, 85–100 μm, and 105–125 μm, respectively, in terms of diameter. The X-ray CT visible (>15 μm) porosity in FINE, MEDIUM and COARSE were 0.09, 0.17, and 0.28 mm3 mm−3, respectively. The corresponding Euler-Poincaré numbers were 180,280, 76,705, and −10,604, respectively, indicating higher connectivity in COARSE than in MEDIUM or FINE. In soil dominated by small air-filled porosity which limits gas diffusion and result in low soil O2 concentration, N2O concentration was increased and CO2 flux was inhibited as the moisture content increased. The turning point in the sharp decrease in O2 concentration was found to correspond with a moisture content, and a pore diameter of 95–110 μm was associated with the critical turning point between holding water and O2 depletion in soil. These findings suggest that O2-regulated biochemical processes are key to the production and flux of GHGs, which in turn are dependent on the soil pore structure and a coupling relationship between N2O and CO2. Improved understanding of the intense effect of soil physical properties provided an empirical foundation for the future development of mechanistic prediction models for how pore-space scale processes with high temporal (hourly) resolution up to GHGs fluxes at larger spatial and temporal scales.

Dual-gas co-production behavior for hydrate-bearing coarse sediment with underlying gas via depressurization under constrained conditions

Hydrate reservoirs with underlying gas show significant potential for commercial exploitation. An experimental apparatus capable of applying confining pressure and axial pressure was built to simulate the accumulation and dissociation of naturally occurring marine hydrate and a novel method for synthesizing hydrate reservoirs with underlying gas was proposed. With the formed methane hydrate-bearing coarse sediment (HBCS) with underlying gas, hydrate dissociation experiments via depressurization under constrained conditions were carried out at different HBCS proportions. The characteristics of heat transfer and dual-gas co-production during the exploitation of hydrate reservoir at various HBCS proportions were presented. Due to the influence of hydrate decomposition, the diverging temperature variations of the underlying layer and upper HBCS layer were observed at HBCS proportions of 0.21, 0.48, and 0.77. The negative effect of the outside pressure on gas production was not observed in our experimental conditions owing to the adopted coarse quartz sand deposits. The final produced gas volume increases with the HBCS proportion increasing. The produced gas percentage is negative or positive related to the HBCS proportions respectively with the extended production time. In addition, the different production behavior of the underlying gas and hydrate decomposed gas may induce the unexpected exploitation accidents such as blowouts resulting from unstable gas production rate. These findings guide the design of exploitation scheme for reservoirs with different HBCS distribution. And an exploitation method by setting the production well in the underlying gas layer/underlying sediment layer with free gas is then proposed, which can inhibit hydrate reformation and ice generation and improve the production well stability during the hydrate exploitation process.

Lithological controls influence river form in contrasting sub‐catchments: The Scamander and Avenue Rivers, Tasmania

AbstractBedrock influence on river channel form is difficult to assess, with many catchments dominated by glacial erosion and with blanketing sediments from both pluvial and fluvial sources. The Scamander catchment in Tasmania lacks glacial history and features two bedrock‐confined sub‐catchments of similar area and maximum flow length, but one dominated by Mathinna Group sedimentary rocks, and the other with large areas in granite lithology. Lithology types, stream network parameters and near stream slope angles were analysed using geographical information systems, and results of stream cross sections, channel form and planforms were compared for each lithology. Results showed that granite features low gradient, shallow streams with channel slope cross sections of &lt;10°. Granite channels are irregular and dominated by large boulders that create channel roughness and resist incision. Weathering products of coarse quartz sand provide anchorages for in‐channel vegetation. By contrast, sedimentary Mathinna Group rocks feature steeply incised trough‐like channels, with near‐channel hillslope gradients mostly between 30° and 50°. Rectangular blocks disintegrate to gravel cobbles on the channel bed, providing poor anchorage for vegetation. Mathinna lithology influences steep, low roughness channels, and stable, incised recurved meanders formed by river interaction with vertical layers of resistant rock. The resistant bedrock lithology is demonstrated in this study to influence varied river planforms, near‐channel slope gradients, channel sediments and cross sections.

Advanced Simulation of Quartz Flotation Using Micro-Nanobubbles by Hybrid Serving of Historical Data (HD) and Deep Learning (DL) Methods

The present study investigates the optimization and advanced simulation of the flotation process of coarse particles (–425 + 106) using micro-nanobubbles (MNBs). For this purpose, flotation experiments in the presence and absence of MNBs were performed on coarse quartz particles, and the results were statistically analyzed. Methyl isobutyl carbinol (MIBC) was employed as a frother for generating MNBs through hydrodynamic cavitation. The significance of the operating variables, including impeller speed, air flow rate, together with the bubble size, and particle size on the flotation recovery was assessed using historical data (HD) design and analysis of variance (ANOVA). The correlation between the flotation parameters and process response in the presence and absence of MNBs was modeled using hybrid convolutional neural networks (CNNs) and recurrent neural networks (RNNs) as the deep learning (DL) frameworks to automatically extract features from input data using a CNN as the base layer. The ANOVA results indicated that all variables affect process responses statistically and meaningfully. Significant interactions were found between air flow rate and particle size as well as impeller speed and MNB size. It was found that a CNN-RNN model could finally be used to model the process based on the intelligent simulation results. Based on Pearson correlation coefficients (PCCs), it was evident that particle size had a strong linear relationship with recovery. However, Shapley additive explanations (SHAP) was considerably more accurate in predicting relationships than Pearson correlations, even though the model outputs agreed well.