Mineral Substrates Research Articles

Enhancing oil recovery using silica nanoparticles: Nanoscale wettability alteration effects and implications for shale oil recovery

Enhanced oil recovery (EOR) techniques have the potential to improve recovery in unconventional shale oil reservoirs which have prolific short-term success but elusive near-to-long term outlook. The use of silicon dioxide nanoparticles for enhancing shale oil recovery has recently gained significant attention in the oil industry. However, the technique remains novel partly due to inadequate fundamental understanding of oil release mechanisms. Herein, the oil recovery potential of untreated and treated silica nanoparticles is investigated using an atomic force microscope (AFM) by studying nanoscale interactions between different crude oil functional species and substrates of pure minerals found in a shale oil reservoir. Quartz and muscovite mica (clay substitute) were employed as substrates as these are the dominant rock minerals identified in the most productive zone of Tuscaloosa Marine Shale (TMS). Thiolates of undecane (CH3) and phenyl (C6H5) compounds were used to simulate alkane and aromatic fractions of TMS crude oil respectively, while undecanoic acid (COOH) thiol was used to represent carboxylic acid found in asphaltene and resin components. Following our in-house experimental protocol for liquid cell force spectroscopy, adhesion forces and surface energies between functionalized AFM probes and mineral substrates were characterized in untreated and amino-treated silica nanoparticle dispersions. Zeta potential of respective nanofluid solutions was measured and AFM adsorption data were supported with scanning electron microscope (SEM) micrographs of TMS rock samples. Results showed that aqueous dispersions of hydrophilic silicon dioxide nanoparticles promote wettability towards a less oil-wet state by significantly lowering the adhesion force and energy barrier to spontaneously detach oil molecules from clay and quartz mineral surfaces in shale reservoirs, shown at the nanoscale with AFM studies. However, the grafting of aminosilanes onto surfaces of silica nanoparticles generally increased adhesion forces and surface energies due to surface charge effect and hydrophobicity. Findings pertinent to nanoparticle silanization were consistent in molecular interactions on mica in nanofluids but not necessarily predictable with quartz surfaces, highlighting mineralogical effects. The irreversible adsorption of silica nanoparticles was also observed. Adhesion force and energy are resolved in various intermolecular forces such as electric double layer repulsion, non-electrostatic interaction and structural forces. The scientific significance and broad engineering implications of results were comprehensively discussed in the context of previously reported core-to-field scale observations of nanofluid EOR. This study pitches new light on the scientific understanding of silica-based nanofluid EOR by probing nanoscale wetting effects of silica nanoparticles with implications for shale oil recovery. The findings herein can help for better understanding of the design of nanofluid EOR reagents and the conditions that favor application of silica nanofluid EOR.

Geometry and mineral heterogeneity controls on precipitation in fractures: An X-ray micro-tomography and reactive transport modeling study

The processes that affect reorganization of flow and transport in fractures during precipitation were investigated experimentally and numerically in order to highlight the interplay between calcite precipitation, flow and growth substrate. Calcite was precipitated from a supersaturated solution at two different flow rates (0.4 or 12 cm3·hr−1) into artificial fractures made in dolomitic limestone. Although the inlet fluid composition and temperature were identical for all the experiments, facture sealing and precipitation patterns were closely linked to the mineral substrate, fracture geometry and flow field reorganization. Calcite precipitation rate is highly variable along and between the flow paths and depends on the local saturation index of the reactive fluid. In addition, calcite precipitates preferentially on calcite comparatively to dolomite substrate. 2D reactive transport modeling accounting for the negative feedback between porosity and permeability decrease succeeded in quantitatively reproducing the experimental observations, such as the evolution of the fracture void obtained from X-ray micro-tomography (XMT), the evolution of the calcium breakthrough concentration and fracture sealing. The corresponding model was then used to evaluate the impacts of fluid flow and reactivity on randomly generated anisotropic fractures geometries. Simulation results reveal that the sealing capacity of fractures and associated reorganization of flow depends on the Damköhler number, i.e., the ratio between characteristic times for advective transport and reaction, although other factors like the fracture geometry and kinetic law play also a role at this stage. More importantly, the existence of a critical saturation index for initiating precipitation onto mineral substrate can substantially impair the prediction of the sealing capacity, and will depend on the spatial heterogeneity and connectivity of the mineral substrate. Most cases result in a strong precipitation gradient along the flow direction that will increase the permeability anisotropy. However, under certain conditions, precipitation allows the fracture to recover more isotropic properties that will lead back to a more uniform flow field and sealing. Negative feedback between precipitation process and transport during fracture closure supports a strong reorganization of flow of supersaturated fluids during geo-engineering operations.

The electrical conductivity of albite feldspar: Implications for oceanic lower crustal sequences and subduction zones

Abstract Volatile-sensitive electrical soundings are becoming more widely adopted, with large nationwide arrays currently being acquired globally. This boom in new data is despite several key uncertainties relating to the electrical responses of a wide range of minerals that make up crustal regions. Complications include the influence of mineral chemistry, hydrous or nominally hydrous phases, and oxygen fugacity on charge-carrying ion activity within a mineral substrate. Feldspars are the most abundant mineral group in the Earth’s crust, comprising about 60% of its mineral assemblages and are particularly prevalent within subduction zones and lower crustal sequences. These areas are known locations where ore systems are commonly rooted, making them among the most widely studied regions in the Earth. To date, few studies exist that cover the electrical behavior of the feldspar mineral albite. To help address some of these issues and complications, we have undertaken electrical conductivity investigations on a single crystal of gem-quality albite (Ab49An48Or3) from Nuevo Casas Grande, Chihuahua, Mexico. Electrical conductivity measurements using impedance spectroscopy were performed at a pressure of 1 GPa over a temperature range of 373–1273 K in a multi-anvil high-pressure apparatus. Experiments were carried out using different metal electrodes: molybdenum, nickel, and rhenium to vary the oxygen fugacity during the experiments. FTIR measurements of the starting and final materials confirm that the initial samples are completely dry but absorb an average of 67 ppm H2O by mass during the experiments from the surrounding pressure medium materials. We observe no correlation in the amount of water absorbed in the feldspar to the oxygen fugacity under water-undersaturated conditions. Our investigations show that the activation enthalpy increases from ~0.77 to ~1.0 eV from the nominally hydrous to the completely dry feldspar. The activation enthalpy decreases with increasing oxygen fugacity for comparable water contents. An oxygen fugacity exponent of –0.069 is calculated at the nominal water content measured in the experiments, indicating an electrical conductivity mechanism that also involves the mobility of hydrogen.

Piedra pómez, tezontle y soluciones nutritivas en el cultivo de tomate cherry

El uso de sustratos minerales locales de bajo costo y soluciones nutritivas con la composición química adecuada pueden ser la alternativa para maximizar el potencial de producción de tomate cherry (Solanum lycopersicum L.). El objetivo del presente estudio fue evaluar sustratos de la zona de Nayarit en combinación con soluciones nutritivas, sobre el crecimiento, contenido nutrimental y producción de tomate cherry. La investigación se realizó en Nayarit, México. El diseño experimental fue completamente al azar con arreglo bifactorial, los factores fueron los sustratos piedra pómez y tezontle, y las soluciones nutritivas de Steiner y Castellanos, esto originó cuatro tratamientos con 11 repeticiones, donde una repetición fue una planta a dos tallos. Se determinaron las variables altura de planta, diámetro de tallo, área foliar, biomasa seca de parte aérea, biomasa seca de raíz, producción de fruto por planta, unidades SPAD y contenido nutrimental foliar (N, P y K). Los resultados mostraron que la solución nutritiva de Steiner incrementó la producción de fruto y también el crecimiento evaluado en altura de planta, diámetro de tallo y biomasa seca de raíz. El contenido nutrimental de N, P y K fue superior con la solución de Castellanos. En el sustrato piedra pómez la producción de fruto, crecimiento de planta y contenido nutrimental fueron más altos en relación a las plantas en tezontle. Se concluyó que el sustrato piedra pómez en combinación con la solución nutritiva de Steiner fue la más viable para tomate cherry, ya que favoreció el crecimiento de planta y producción de fruto.

Water retention in sandy substrates modified by cross‐linked polymeric microgels and their complexes with a linear cationic polymer

AbstractNew synthetic soil conditioners for anti‐erosion protection of soils in the form of microgel copolymers of N‐isopropylacrylamide and acrylic acid (PAA#) and their interpolyelectrolyte complexes (IPEC#) with different surface charges are tested for optimization of water retention and porous structure in two samples of soil substrates. Water retention curves (WRCs) are used as a fundamental thermodynamic indicator of water holding capacity in soil substrates treated by new polymeric materials. Soil‐hydrological constants, as well as specific surface parameters and pore distribution curves are calculated from the WRCs using the van Genuhten model and the Voronin method in the author's modification. PAA# and anionic IPEC# with high swelling degree at a dose of 1% (by weight) increase field water capacity, available soil water range and specific surface area by 5–6 times for quartz sand, along with reorganizing its structure towards micropore dominance. For loamy sand, the same treatment was less effective with a twofold increase in field moisture capacity, double or triple increase of specific surface area, and an almost constant range of available soil water due to the strong increase of wilting point parameter. Weakly swelling linear polyacrylic acid and cationic IPEC# did not significantly affect properties of both mineral substrates.

The advancing mycelial frontier of ectomycorrhizal fungi.

This article is a Commentary on Hagenbo et al. (2021), 230: 1609–1622.

2D mineral substrate leads to more sensitive flexible magnetosensors

By using a layered mica substrate, magnetosensors can be made extremely flexible without sacrificing sensitivity.

Detection of petroleum hydrocarbons in continental areas using airborne hyperspectral thermal infrared data (SEBASS)

Remote sensing tools have proven to be effective for direct detection of petroleum hydrocarbons (PHC) in continental areas. PHC yield diagnostic absorption features in the near, shortwave, midwave, and thermal infrared (NIR-SWIR-MWIR-TIR) ranges. Thus far, the NIR-SWIR range has been primarily exploited for remote sensing PHC detection, whereas the application of MWIR and TIR data has remained underexplored. In this work, we aim to close this gap by using the Spatially-Enhanced Broadband Array Spectrograph System (SEBASS) (7.6–13.5 μm) to map PHC-impregnated soil substrates. A laboratory experiment was performed to identify the features in pure crude oil samples, in dry/wet mineral substrates, and in their physical mixtures using attenuated total reflectance (ATR) and directional-hemispherical reflectance (DHR) measurements. A similar setting was designed in an open environment and imaged by the SEBASS sensor. Close-range spectroscopy indicated that PHC features between 7 and 15 μm are subtle in comparison to the features of the mineral substrates, thus hindering direct identification of the PHC spectrally. However, the PHC coating of the grains increased the emissivity of the background features - a finding that was supported by SEBASS data processing using a matched filtering technique. The SEBASS data indicated that besides an increase in the emissivity of the underlying substrates, the presence of PHC also induces a change in the temperature of the contaminated targets. The combination of these two factors highlighted the contaminated sites indirectly. Since the mapping of clean, moist and PHC contaminated sites with TIR data depends on variations in the emissivity and temperature of the targets, the application can be extended to orbital sensors with lower spectral resolution (such as ASTER and ECOSTRESS), enabling the monitoring of larger areas.

Supergene gold mineralization from exploited placer deposits at Dziwiszów in the Sudetes (NE Bohemian Massif, SW Poland)

Representative ore samples collected from outcrops in the exploited Dziwiszów placer gold deposit in Lower Silesia offer the opportunity to study supergene transformations which probably occurred over historic periods. The ore samples are alloys of gold and silver, with trace amounts of Hg and Pd. There are three distinct sub-types of detrital gold: (1) flaky, (2) nugget-like; and (3) irregular/craggy grains, respectively. All samples record the features of supergene processes such as dissolution textures, as well as the formation and aggregation of authigenic nano- and microparticles of native gold. Surface authigenic morphotypes include nano-particles of semi-spherical or blebby native gold, as well as overgrowths of crystalline phases of platy gold and micro-aggregates of bacteriomorphic Au, which provide evidence for microbial gold biomineralization. The growth history of individual native gold particles is documented by nano- to micro-textural investigations of sample grains ranging from isolated semi-spherical nanoparticles through agglomerates to irregularly shaped platy micro-nuggets of gold. The presence of nano- to microphase native gold embedded in fine-grained assemblages of clayish masses and the absence of any evidence for abrasion of individual grains suggest the authigenic origin of blebby native gold particles and overgrowths of platy native gold grains. Hence, we propose that these particles were formed in situ. Chemical transfer may be related to both the precipitation of Au from a colloidal solution, as well as to its adsorption by clay minerals and surface precipitation on particles of the mineral substrate.

The Combined Use of Ion Chromatography and Scanning Electron Microscopy to Assess Salt-affected Mineral Materials in Cultural Heritage

ABSTRACT Careful sampling, sample preparation, and subsequent measurements are key steps in handling complex, salt-affected mineral materials. Chemical analyses of ionic components in aqueous solutions (ion chromatography – IC) are nearly always affected by the presence of components originating mostly from the substrate; this causes discrepancies when calculating the equivalent concentrations. This study uses IC and scanning electron microscopy (SEM-EDS) results from the investigation of two historical, salt-laden buildings from Austria to determine the influence of different mineral substrates on the inorganic ionic compositions. Results show that besides carbonate substrates, also seemingly pure salt crusts may include impurities distorting the results and thus the interpretation of data by using the ECOS Runsalt model. The combined use of IC and SEM-EDS provided a reliable solution to assess complex salt-affected building materials.

Colonization and bioweathering of monazite by Aspergillus niger: solubilization and precipitation of rare earth elements.

Geoactive fungi play a significant role in bioweathering of rock and mineral substrates. Monazite is a phosphate mineral containing the rare earth elements (REE) cerium, lanthanum and neodymium. Little is known about geomicrobial transformations of REE-bearing minerals which are also relevant to REE biorecovery from terrestrial and extra-terrestrial reserves. The geoactive soil fungus Aspergillus niger colonized monazite in solid and liquid growth media without any apparent growth inhibition. In a glucose-minerals salts medium, monazite enhanced growth and mycelium extensively covered rock particle surfaces, probably due to the provision of phosphate and essential trace metals. Teeth-like and pagoda-like etching patterns indicated monazite dissolution, with extensive precipitation of secondary oxalate minerals. Biomechanical forces ensued causing aggressive bioweathering effects by tunnelling, penetration and splitting of the ore particles. High amounts of oxalic acid (~46 mM) and moderate amounts of citric acid (~5 mM) were produced in liquid media containing 2% (wt./vol.) monazite, and REE and phosphate were released. Correlation analysis suggested that citric acid was more effective than oxalic acid in REE mobilization, although the higher concentration of oxalic acid also implied complexant activity, as well as the prime role in REE-oxalate precipitation.

Study of the Adhesion of Silicate-Based Coating Formulations on a Wood Substrate

Silicate coatings are environmentally friendly inorganic-based products that have long been used for mineral substrates and protection of steel against corrosion. The development and acceptance of these coatings in the wood sector require some adjustments in formulations or special preparation of the surface to be coated to obtain durable finishes. In this work, the adhesion of various silicate-based formulations to a beech wood substrate (Fagus sylvatica L.), was assessed with the main objective to study relevant parameters and potential improvements. Adhesion strength was determined by pull-off and cross-cut tests. Other coating properties such as scratch, impact, and water resistance were also determined. Surface roughness and interface were analyzed using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM), and coating curing was studied by attenuated total reflection-infrared spectroscopy (ATR FTIR). The results showed that adhesion was highly dependent on formulation, penetration of the coatings into wood, and mechanical anchoring. Increasing the content of solid particles in the coating formulations or adding a polyol (glycerol, xylose), which probably acted as a coalescent, considerably decreased the adhesion strength, probably by blocking penetration into the wood by forming aggregates. Adhesion was improved by pre-mineralization of the surface, and substitution of a part of the potassium silicate binder with potassium methyl siliconate reduced the formation of cracks caused by dimensional instability of the wood.

Managed pathways for CO2 mineralisation: analogy with nature and potential contribution to CCUS-led reduction targets.

The managed mineralisation of CO2 on mineral substrates has significant potential to mitigate CO2 emissions to atmosphere, using processes that are analogous to the formation of limestone in nature. High-temperatures and pressures or ambient conditions can be applied in processes that compare with the natural chemical, hydrothermal or biological formation of limestone. In the UK, recent policy developments recognise the potential of carbon utilisation and a reduction target of 40 Mt by 2030 has been set. In the present work, the analogies between natural and managed carbonate-production are briefly reviewed and the potential gains for mineralisation technology employing flue-gas as a direct source of CO2 are presented. With reference to selected UK solid waste arisings, our high-level analysis indicates mineralisation is capable of permanently sequestrating 1.2 Mt per year of CO2 in carbonated construction products. At a European level, nearly 7.8 Mt of CO2 can be managed in the same way. If indicative indirect CO2 savings are also considered, maximum total CO2 reductions of up to 3 and 30 Mt per year are possible in the UK and Europe, respectively. In respect of the UK's CCUS-led CO2 reductions for the 8 years to 2030, our high-level assessment suggests that up to 24 Mt, representing 60% of the 'target', may be met by the mineralisation of selected industrial process residues.

Environmental factors shaping assemblages of ostracods (Crustacea: Ostracoda) in springs situated in the River Krąpiel valley (NW Poland)

We investigated the ostracod assemblage structure in springs of a small lowland River Krąpiel valley. Environmental factors and the potential of ostracods as indicators of spring type were analysed. The analysis involved the type of spring, substrate, physicochemical parameters, and the river valley's hydrological status as environmental factors. A total of thirty ostracod species were recorded. The average count of ostracod individuals in a sample amounted to 100. The assemblages were dominated by juvenile Candona sp., juvenile Psychrodromus sp., Cypria ophtalmica, and Cypridopsis vidua. The spring species accounted for less than 1% of the individual counts, except for juvenile Psychrodromus sp. with 21% and Eucypris pigra with 4%. The average number of taxa per spring was 5. The ostracod assemblages were significantly influenced by limnocrene springs, spring flooding by the river overflow, the presence of coarse leaf litter, the presence of fine organic matter, a high content of NH4 as well as by BOD5, conductivity, pH, Fe, the river habitat modification index (RHM), the habitat modification score (HMS), and the river habitat quality (RHQ). The habitat conditions for the spring species appeared to be enhanced by the domination of mineral substrate over fine particulate organic matter, an elevated pH, the presence of leaf-derived organic matter, and the absence of flooding by the river. The spring species showed no association with the Krąpiel valley hydrological factors.

ДРУГИЙ СТАНДАРТ УКРАЇНИ НА БІТУМИ НАФТОВІ ДОРОЖНІ В’ЯЗКІ: ЗМІСТ ТА ПЕРСПЕКТИВИ

The first Ukrainian standard ДСТУ 4044 “Viscous petroleum road bitumens. Technical conditions” was implemented in 2002. According to its content and list of indicators, it met the level of the oil refining industry of Ukraine and the state of the road industry. In addition to conventional indicators, it included additional indicators of adhesion and mass content of paraffins. The indicator for paraffin remained unregulated, because there was neither acceptable method nor necessary equipment, and in generally an intention of manufacturers and users to apply it. The standard referred to in the article differs from the previous one by the principle of assigning indicators and their list. This is largely due to Ukraine’s accession to the European Free Trade Association and the deepening of scientific knowledge on predicting the behavior of bitumen under different conditions and their impact on the properties of asphalt concrete. Accordingly, the limits of normalization of bitumen grades on the depth of needle penetration were changed, which led to an increase in amount of grades from 4 to 5. Using the dependence of the penetration index on the softening point temperature, its new normative values are ordered. The Fraas breaking temperature provided by the standard is slightly lower than that normalized EN 12591 which is due the climatic conditions of Ukraine. The rate of adhesion of bitumen to the surface is normalized, which quantitatively characterizes the adhesion of bitumen to the mineral substrate, the least favorable for interaction. It is proposed to determine the indicators of technological aging by the RTFOT method. The standard contains additional indicators to be determined according to the harmonized European standards ДСТУ EN 12607-1 and ДСТУ EN 13302 (methods for determining the dynamic viscosity). Additional standards include equal viscous heating temperatures of bitumen in the production of asphalt mixtures and their compaction. The first is the temperature, which corresponds to a bitumen viscosity of 0.5 Pas, the second is 10 Pas. Elongation at a temperature of 0 ºC is included in the standard as a certain analogue of the breaking temperature. Based on the fact that at this time the next European standard is in the final stage before approval, the values of additional indicators can be included into this standard after adjusting their values with European ones based on the characteristics of bitumen used in Ukraine. Keywords: bitumen, depth of needle penetration, softening point temperature, adhesion, ductility, cohesion, heating.

Parameters of Drainage Waters Collected during Soilless Tomato Cultivation in Mineral and Organic Substrates

The aim was to determine the suitability of various substrates for application in a closed system of soilless tomato cultivation, based on the potential fitness of drainage waters from these substrates for recirculation. Four substrates were used: rockwool, coir substrate, lignite substrate (Carbomat) and biodegradable organic substrate (Biopot). Tomato plants grown in these substrates were fertilized with the same amount of nutrient solution, containing the same concentration of nutrients. The characteristics of drainage water from these substrates were analyzed during cultivation. The highest amount of drainage water was collected from the lignite substrate Carbomat. However, these leachates showed good properties for further recirculation: low electro conductivity and turbidity, high nutrient content, moderate microbial load with high population of Trichoderma fungi, and being beneficial for plant growth. Moreover, Carbomat produced the highest tomato yield compared to other substrates. This indicates that this organic substrate is an efficient alternative to rockwool and its drainage water may be reused in a recirculation system. On the contrary, the drainage water from the Biopot substrate showed the worst qualities: high pH and low EC, low concentration of nitrate nitrogen and phosphorus, very high turbidity and a high number of microorganisms. These parameters do not qualify Biopot drainage waters for reuse.

Rock glaciers and paraglacial features influence stream invertebrates in a deglaciating Alpine area

Abstract Climate change and progressive glacier loss are leading to rapid ecological shifts in alpine aquatic systems. Rock glaciers and paraglacial features such as proglacial lakes, moraines, and taluses can alter the gradients of glacial influence along alpine river networks, but the ecological responses are still understudied. We investigated benthic invertebrate communities of different stream types (upper kryal, lower kryal, glacio‐rhithral, krenal, and rock glacial) within a deglaciating area of the Italian Alps (Solda and Zay sub‐catchments). Alpha‐ (Shannon index and taxa richness) and β‐diversity (i.e. nestedness and turnover), production (abundance, biomass), average body mass of invertebrate taxa, and functional feeding groups were used to analyse the influence of habitat conditions on invertebrate communities in different microhabitats (mineral substrates, bryophytes, Hydrurus foetidus). We defined an index of habitat mildness based on water temperature, channel stability, turbidity, and organic detritus, to measure the difference in community metrics over a gradient of habitat amelioration, driven by the mixing of distinct stream types and their interactions with paraglacial features. While diversity proxies showed an asymptotic behaviour along the gradient, the quantitative metrics peaked at intermediate mildness. Peaks of invertebrate biomass/abundance were recorded at the glacio‐rhithral station below the talus. Highest average body mass occurred at Zay, specifically at the rock glacial stream, and at the lower kryal stations influenced by the lake/moraine and the rock glacier. The moraine outflow showed unexpected high biomass/abundance values of shredders and grazers, that were supported by a high epilithic production. Bryophytes acted as local scale multipliers of mildness as they stored more detritus, and hosted higher biomass/abundance of invertebrates and, in particular, of gatherer–collectors. Beta‐diversity, driven by the turnover component, was positively related to different habitat mildness of the sampling stations. Although influenced by distinct lentic/lotic conditions, rock glacial streams hosted several taxa typical of glacio‐rhithral and krenal stations, alongside large numbers of Diamesa (Chironomidae), a genus typical of kryal habitats. Under progressive deglaciation, rock glaciers and paraglacial features influence the invertebrate communities of alpine river networks. As they host a high number of taxa dwelling in non‐glacial locations, rock glacial streams may act as stepping stones facilitating invertebrate colonisation following glacier retreat. After glacier loss, rock glacial streams may represent climate refugia for cold adapted taxa and/or kryal specialists, because the slow thawing of their ice might sustain cold water conditions for a longer period of time.

Hydraulic niche utilization by larvae of the three Drusinae clades (Insecta: Trichoptera)

Hydraulic niche descriptors of final instar larvae of nine Drusus species (Trichoptera) were studied in small, spring-fed, first-order headwaters located in the Mühlviertel (Upper Austria), Koralpe (Carinthia, Austria), and in the Austrian and Italian Alps. The species investigated covered all three clades of Drusinae: the shredder clade (Drusus franzi, D. alpinus), the grazer clade (D. biguttatus, D. chauvinianus, D. dudor, D. monticola), and the filtering carnivore clade (D. chrysotus, D. katagelastos, D. muelleri). Flow velocity was measured at front center of 68 larvae, head upstream, on the top of mineral substrate particles at water depths of 10–30 mm, using a tripod-stabilized Micro propeller meter (propeller diameter = 10 mm). Each data series consisted of a sampled measurement lasting 30 s (measuring interval = 1 s). In total, 2040 single velocity measurements were taken. Instantaneous flow velocities and drag at the sites of the 68 larvae varied from 0 to 0.93 m s−1 and 0 to 8346 *10−6 N, respectively. Flow velocities and drag between the three clades were highly significantly different (p < 0.001); mean velocity (+ 95% confidence limits) for the three clades were 0.09 + 0.00 m s−1 for the shredder, 0.25 + 0.00 m s−1 for the grazer, and 0.31 + 0.01 m s−1 for the filtering carnivore clade; the corresponding data for drag were (85 + 18)*10−6 N, (422 + 61)*10−6 N and (1125 + 83)*10−6 N, respectively. Adhesive friction ranged from (41.07 + 53.03)*10−6 N in D. franzi to (255.24 + 216.87)*10−6 N in D. chrysotus. Except in D. franzi and D. dudor adhesive friction was always well below drag force, indicating that submerged weight alone was not sufficient to stabilize the larvae in their hydraulic environment. Reynolds numbers varied between 0 in D. franzi and D. alpinus, and 12,634 in D. katagelastos, with 7% of the total in the laminar (R < 500), 30% in the transitional (R = 500–2000), and 61% in the fully turbulent stage (R > 2000). Froude numbers (Fr) varied from 0 to 2.97. The two Drusus species of the shredder clade and three out of four species of the grazer clade were exposed to subcritical Fr < 1, one species of the grazer clade and two out of three species of the filtering clade to supercritical Froude numbers >1.

The stoichiometric C-Fe ratio regulates glucose mineralization and stabilization via microbial processes

The association of soil organic matter (SOM) with iron (Fe) oxides by adsorption and/or co-precipitation contributes to long term C stabilization in soil. While there is an understanding of the relationship between soil carbon (C) and the biogeochemical cycling of Fe, a lack of information exists on the role of Fe oxides on the accumulation of C in paddy soils. This study aimed to assess the role of Fe (oxyhydr)oxides on mineralization and stabilization processes following amendment of paddy soil with a labile C substrate (99 atom % 13C-glucose). The study utilized 4 paddy soils with a total Fe concentration ranging from 13.7 to 55.8 g kg−1. In soils with 42.7 and 55.8 g kg−1 Fe, the addition of glucose resulted in an Fe bound organic C: Fe molar ratio (C:Fe molar ratio) ≥6, suggesting the formation of Fe-OM complexes mainly via co-precipitation. The highest portion of 13C (13.8%) protected in Fe-OM complexes was found in soil containing 55.8 g kg−1 of Fe. The stabilization of the added labile C substrate was shown, using random forest analysis, to be controlled by the C: Fe molar ratio, while substrate mineralization was regulated by the core genera Sphingomonas and Devosa (r-strategists) (affiliated to Proteobacteria) and C:N ratio. Substrate mineralization was 47% lower in soil containing 55.8 g Fe kg−1 compared to 13.7 g Fe kg−1, with a concomitant reduction in SOM priming of 37%. This reduction in substrate mineralization and the priming effect was likely due to lower C substrate availability via the formation of Fe-OM complexes, thereby protecting the C from mineralization. In conclusion, the Fe concentration in paddy soils plays a central role in the abiotic stabilization of ‘new’ C through the formation of Fe-OM complexes via co-precipitation, thereby limiting the availability of this C substrate for microbial mineralization, and at the same time modulating the microbial community structure.

Sorbents Based on Crown Ethers for Purification of Aqueous Solutions from Metal Ions

The sorption of copper and lead ions by sorbents based on 15-crown-5 and 18-crown-6 esters and their benzosubstituted analogs chemically bonded to porous mineral substrates under the action of gamma radiation is considered. The influence of various parameters on the efficiency of metal sorption from aqueous solutions is studied. The correspondence between the ability of the sorbent to absorb metal ions and the size of the cavity of the crown ether (CE) is shown, which determines the high level of selectivity of such sorbents. Indeed, sorbents based on 18-crown-6 ether have a significantly higher sorption capacity in relation to lead, while 15-crown-5 ether is more effective for the sorption of copper ions. The effect of the radiation dose rate and the time of holding the sorbent in a salt solution on the amount of sorbed metal is studied.