Mineral Substrates Research Articles

Could landscape ecology principles apply at the microscale? A metabarcoding approach on Trichoptera larvae-associated microbial diversity

Landscape heterogeneity is known as a major factor of community structure and composition. Whether this effect of the landscape extends at different scales and particularly at the relevant scale for microorganisms remained to be determined. We used the cases produced by aquatic larvae of Trichoptera, which assemble organic or mineral particles, as naturally replicated experimental systems representing structured substrates to determine the effect of landscape structuration on microbial communities. A metabarcoding approach was used to characterise fungal, bacterial and diatom communities on cases produced by six Trichoptera species and related unstructured organic and mineral substrates. The structuration of the particles constituting the cases was also determined as a measure of microscale landscape. Structured substrates harboured communities of diatoms, fungi and bacteria that differed from those found on unstructured substrates. Microbial communities also differed between organic and mineral substrates. We found a higher microbial diversity on structured substrates than on unstructured substrates. The heterogeneity of the microscale landscape also affected bacterial and fungal communities within cases. These results highlight the importance of microscale landscape structuration for microbial diversity and demonstrate that approaches of landscape ecology could be downscaled to the microscale.

EXPERIENCE IN THE APPLICATION OF METHODS OF RESTORATION OF DAMAGED REINFORCED CONCRETE STRUCTURES IN TRANSPORT CONSTRUCTION

Evidence suggests that concrete self-healing can be achieved by introducing bacteria into the concrete matrix. Despite the fact that a number of researchers have conducted experiments with different types of bacteria, the ideal combination of factors such as bacterial species, types of mineral substrate, types of carrier materials and the amount of each of these components has yet to be identified to make a qualitative breakthrough in solving the problem of self-healing concrete and reinforced concrete structures. The paper presents the results of a study on the development of a technology for obtaining materials with bio-additives, the study of the process of crack repair in concrete, and the establishment of physical and technical properties of concrete modified with a microbiological additive and restored materials. The article analyses the processes of structure formation, physical and mechanical properties of concrete and other cement composites, ways to improve them, degradation processes, damage and defects that reduce the durability of reinforced concrete structures, as well as methods of their repair and restoration. Based on the analysis of existing approaches to the creation of concrete using biotechnology and self-healing processes of defective reinforced concrete structures, theoretical prerequisites for the development of technology for the creation of concrete modified with microbiological additives and self-healing structures are developed. It is concluded that it is potentially possible to heal cracks in concrete under the control of bacteria as a result of mineral sludge formation. However, some areas of this concept require further development. It is necessary to clarify how effectively the deposition of minerals produced by bacteria seals large cracks, i.e. how much the permeability of cracked concrete is reduced to prevent corrosion of embedded reinforcement and thus increase the service life of the building material. In addition, it is necessary to select bacterial species that remain viable when introduced into the concrete matrix for at least the expected service life of the structure. Despite the fact that no qualitative breakthrough has yet been achieved in the field of concrete self-healing, this is a very promising area of research.

Features of distribution of a number of rare and protected plant species in the territories of oligotrophic and mesotrophic mires within oil fields of Khanty-Mansi Autonomous Area – Yugra

The technogenic transformation of oligotrophic and mesotrophic mires, which occurs during the functioning of the infrastructure of oil fields, leads to the emergence of new habitats with fundamentally different conditions, previously uncharacteristic for these biogeocenoses. Expansion of areas of eutrophicated soils, pollution with oil and chlorides, subsequent reclamation measures, the formation of embankments from mineral soil – all these disturbance types create the preconditions for the disappearance of rare plants, however, in parallel, the introduction of new species that also have a protected status is noted. Transformed areas of mires can become refugia for endangered and protected plants. Three groups of plants can be distinguished, related to the nature of the technogenically transformed substrates on which they settle. The first group includes plants that settle exclusively on peat, the second includes species found on mineral substrates introduced into mires, the third group includes species that can grow both on mineral substrates and technogenically eutrophicated peat soils. The article provides characteristics of a number of transformed habitats that arose in the mire areas of the – Khanty-Mansi Autonomous Area – Yugra, within which rare and protected species were found. Among the plants whose distribution in the mires of the district is largely due to the expansion of human economic activity, mention should be made of Thelypteris palustris, Lycopodiella inundata, Typha angustifolia, liverwort Heterogemma laxa, etc.

Nutrient removal efficacy and microbial dynamics in constructed wetlands using Fe(III)-mineral substrates for low carbon-nitrogen ratio sewage treatment.

This study evaluated the roles of two common sources of Fe(III)-minerals-volcanic rock (VR) and synthetic banded iron formations from waste iron tailings (BIF-W)-in vertical flow-constructed wetlands (VFCWs). The evaluation was conducted in the absence of critical environmental factors, including Fe(II), Fe(III), and soil organic matter (SOM), using metagenomic analysis and integrated correlation networks to predict nitrogen removal pathways. Our findings revealed that Fe(III)-minerals enhanced metabolic activities and cellular processes related to carbohydrate decomposition, thereby increasing the average COD removal rates by 10.7% for VR and 5.90% for BIF-W. Notably, VR improved nitrogen removal by 1.70% and 5.40% compared to BIF-W and the control, respectively. Fe(III)-mineral amendment in bioreactors also improved the retention of denitrification and nitrification bacteria (phylum Proteobacteria) and anammox bacteria (phylum Planctomycetes), with increases of 3.60% and 3.20% using VR compared to BIF-W. Metagenomic functional predictionindicated that the nitrogen removal mechanisms in VFCWs with low C/N ratios involve simultaneous partial nitrification, ANAMMOX, and denitrification (SNAD). Network-based analyses and correlation pathways further suggest that the advantages of Fe(III)-minerals are manifested in the enhancement of denitrification microorganisms. Microbial communities may be activated by the functional dissolution of Fe(III)-minerals, which improves the stability of SOM or the conversion of Fe(III)/Fe(II). This study provides new insights into the functional roles of Fe(III)-minerals in VFCWs at the microbial community level, and provides a foundation for developing Fe-based SNAD enhancement technologies.

Microbial colonization of gypsum: from the fossil record to the present day.

Microorganisms inhabiting gypsum have been observed in environments that differ greatly in water availability. Gypsum colonized by microorganisms, including cyanobacteria, eukaryotic algae, and diverse heterotrophic communities, occurs in hot, arid or even hyperarid environments, in cold environments of the Antarctic and Arctic zones, and in saline and hypersaline lakes and ponds where gypsum precipitates. Fossilized microbial remnants preserved in gypsum were also reported. Gypsum protects the endolithic microbial communities against excessive insolation and ultraviolet radiation, while allowing photosynthetically active radiation to penetrate through the mineral substrate. We here review the worldwide occurrences of microbially colonized gypsum and the specific properties of gypsum related to its function as a substrate and habitat for microbial life on Earth and possibly beyond. Methods for detecting and characterizing endolithic communities and their biomarkers in gypsum are discussed, including microscopic, spectroscopic, chemical, and molecular biological techniques. The modes of adaptation of different microorganisms to life within gypsum crystals under different environmental conditions are described. Finally, we discuss gypsum deposits as possible targets for the search for microbial life or its remnants beyond Earth, especially on Mars, where sulfate-rich deposits occur, and propose strategies to detect them during space exploration missions.

PENGUJIAN TIGA METODE PENGUKURAN BOBOT ISI PADA TANAH GAMBUT

This research aims to compare the methods of bulk density measurements in peat soils. The methods are ring sample, peat auger, and syringe. The research was conducted in peat soils in Pontianak City. The research was carried out from June to December 2023. Peat samples were the surface peat (0-10 cm). The samples were collected from five plots, and five replications. On average, the value of bulk density measured by the ring sample was 0.27 g cm-3, which is significantly different from bulk density values measured by the peat auger and syringe: 0.11 g cm-3 and 0.09 g cm-3, respectively. Bulk densities of peat auger and syringe are statistically indifferent. Soil compaction during sampling causes the ring sample's high bulk density value. Accordingly, carbon stock calculation based on ring sample bulk density is significantly higher than carbon stocks calculated by bulk densities of auger and syringe. The bulk density measurement with a peat auger took longer because a water displacement approach must measure the sample volume. Collecting bulk-density samples with a syringe is the easiest and fastest. The volume of the syringe sample is only 10 cm3, and the sample can be taken until the mineral substratum. The number of sample collected by syringe can be significantly increased at 5 cm sampling interval, or equals to 10 sub-samples per 50 cm peat core. Pearson linear correlations of these three methods are sufficiently strong.

Water-Catalyzed Formation of Reactive Oxygen Species from NO2 on a Weakly Hydrated Calcite Surface.

The interfaces of weakly hydrated mineral substrates have been shown to serve as catalytic sites for chemical reactions that may not be accessible in the gas phase or under bulk conditions. Currently known mechanisms for the formation of reactive oxygen species (ROS) from nitrogen dioxide (NO2) involve NO2 dimerization. Here, we report the formation of the ROS HONO via a mechanism involving simple adsorption of a single NO2 molecule on a weakly hydrated calcite substrate. First-principles molecular dynamics simulations coupled with enhanced sampling techniques show how an adsorbed water sublayer can enhance NO2 adsorption on calcite compared to adsorption on a bare dry substrate. On the weakly hydrated calcite surface, an interfacial electric field facilitates proton extraction from water, thus allowing HONO formation from a single adsorbed NO2, i.e., without the need for the formation of a NO2 dimer precomplex. HONO formation on calcite is kinetically more favorable than that in the gas phase, with a reaction barrier of 14 kcal/mol on the weakly hydrated calcite surface compared to 27 kcal/mol in the gas phase. Further photocatalysed HONO production by visible light and HONO dissociation are hampered on calcite, unlike the process on silica. NO2 is a significant anthropogenic pollutant, and understanding its chemistry is crucial for explaining the high ROS levels and haze formation in polluted areas or prebiotic ROS generation. These findings emphasize how mineral substrates under water-restricted hydration conditions can trigger chemical pathways that are unexpected in the gas phase or under bulk conditions.

Unified approach for describing rheological behavior of soil and mineral substrates modified with polymers

Studies in the rheology of natural aqueous dispersions (soils and their mineral substrates) as well as the approaches to control rheological parameters of these systems are of the prime importance to progress in the modern agricultural technologies, geoengineering, construction, etc. To advance in these fundamental and applied directions both original processing of the experimental results and search for the promising modifying agents are required. In this paper, rheological behavior of a representative range of virgin and modified aqueous soils, quartz sand and clays was studied. Modification of the above aqueous dispersed systems with polyelectrolytes and their complexes provided variation of the basic viscoelastic parameters corresponding to the linear viscoelastic region (initial storage modulus G0′, initial loss modulus G0", and strain γ0) and to the transition to steady-state flow (storage modulus Gin′ and strain γin) within 1 – 2 orders of magnitude. For samples studied, correlations for these mechanical characteristics were found – with the growth in the values of G0′ and G0′′, the increase in the values of Gin′ and decrease in the values of γ0 and γin were observed. Based on these correlations the master curves for the strain dependences of storage and loss modulus as well as for loss tangent were constructed. The appearance of the master curves reflected the unified regularities of the rheological response of dispersed systems which were attributed to the general features of structural evolution caused by the mechanical loading. Procedure for prediction of the rheological behavior of aqueous soil samples based on the experimental measurement of only two experimental characteristics (initial values of storage and loss modulus G0′ and G0′′ respectively) was proposed. The validity of this approach was tested using independent experimental data. The original approach obtained can be used for express analysis of the rheology of natural aqueous dispersed materials.

Biogeochemical traces and microbe-mineral interactions in the hyperarid core of the Atacama Desert

Life found various ways to thrive in hostile desert environments. Common adaptation mechanisms are protection against desiccation and UV radiation in biofilms and biocrusts as well as the hypolithic and endolithic colonization of rocks. One of those hostile regions is the Atacama Desert in Northern Chile with its hyperarid core, counted among the most arid places on Earth. Besides the aridity, life faces severe restrictions in these surroundings, e.g. extremely high UV radiation, scarce nutrient supply, and immense salt concentrations. Still, microbial communities and soil organic matter are crucial for the stability of soils and surface sediments in arid ecosystems. Combining molecular mass spectrometry for lipid biomarkers, scanning electron microscopy, and nuclear magnetic resonance spectroscopy, we individually investigated two factors that are of particular importance for the stability of dryland landscapes now and in the future: 1) We studied biogeochemical traces (organic remnants) in surface sediments along an aridity gradient with regard to possible decomposition and/or sequestration of organic compounds. 2) We investigated the interaction of lithobiontic and endolithic microbial communities with the mineral surface with special regard to the stability of soil and surface sediment structures in different areas of the Atacama Desert: in the region of the Salar Grande, Pisagua, and the Quebrada da Aroma. We analyzed halite- and calcium sulfate-dominated evaporitic crusts with and without visible microbial colonization. Organic traces were present in all investigated samples. Following an aridity gradient along the Quebrada de Aroma from an annual precipitation of about 20 mm to the hyperarid core with approx. 2 mm, we found a decrease in functionalized molecular compounds and plant-derived biomarkers (long-chain fatty acids, sterols) as well as an increase in aromatic hydrocarbons, indicating strongly decomposed remnants of plants and microorganisms. The investigation of halite- and calcium sulfate-dominated evaporitic crusts from the Salar Grande, Pisagua, and Aroma region revealed tight interactions of microorganisms with the mineral substrate. Indications of recent bacterial activity were ubiquitous (e.g. short-chain membrane fatty acids, carbohydrates of extracellular polymeric substances (EPS)). Scanning electron microscopy revealed that especially the microbial EPS within evaporites seems to biochemically stabilize mineral aggregates by agglutination. Moreover, fungal biomarkers showed that fungi and fungal parts of lichen were not only present at the surface of physical soil crusts but form widespread networks in the crusts and thereby contribute significantly to the physical stabilization of soils and surface sediments and erosion protection.

The Influence of Minimal Cultivation Techniques on Growth Rate of Robinia pseudacacia L. Seedlings

The seed provenance, the type of substrate and its properties, as well as the watering regime in the first years after sowing are among the most important characteristics affecting the production of containerized seedlings. The objective of this study was to analyse the growth of black locust (Robinia pseudacacia L.) seedlings on different types of substrate (six mineral and two organic) with different textures and pHs under three different regimes of available water content (no-limiting, medium drought, severe drought) over a period of five months (May–October 2023), using seeds from three sources located in the southeast, south, and west of Romania. The highest seedling emergence rate (73.7%) was obtained for the medium seeds with 18.492 g weight (1000 seed weighs) (Bucharest provenance). Direct sowing in the field and containerized seedlings both showed a trend of growing in height during unlimited water and of growing in diameter during low watering. The lowest survival rate of seedlings (86.7%) occurred in the mineral substrate in the case of rendzina with additional sand (pH 8.70), and for the organic substrate, the lowest survival rate (87.0%) occurred for the peat MKS 3 substrate (pH 4.54).

Mathematical Model of Closed Microecosystem “Algae – Heterotrophic Bacteria”

Model of closed microecosystem “algae - heterotrophic bacteria” is proposed in this paper. Mathematical model is the Cauchy problem for system of nonlinear ordinary differential equations. To develop the model the Liebig’s law of the minimum is consistently used for both specific rate of biomass growth and specific death rate of algae and bacteria cells. To describe the specific rate of substrate utilization by algae and bacteria the Andrew’s model (substrate inhibition) is used. It is assumed that specific death rate of algae and bacteria cells increases with decreasing substrate concentration. It is also assumed that carbon and nitrogen are main biogenic elements, and in the system they are in the form of mineral substrate (CO2, NO2, NO3, NH4) and biological substrate (proteins, lipids and carbohydrates). Mathematical model describing time variations in concentration of elements of microecosystem is formulated under the following assumptions: 1) stoichiometric coefficients of algae and bacteria cells are constant in the development of microecosystem; 2) utilization of carbon and nitrogen by algae and bacteria occurs independently; 3) oxygen produced by algae cells during photosynthesis completely covers the demand for oxygen for algae and bacteria cells. To verify the proposed model experimental data for microecosystems «Clorella vulgaris – Pseudomonas sp.» и «Scenedesmus obliquus – Pseudomonas sp.» are used. These systems were studied in laboratory conditions, and concentrations of elements of microecosystems in stationary state were obtained. Parameters of functions describing specific rate of utilization of biogenic elements were derived from experimental data for growth kinetics of algae and bacteria. Concentration of the biomass in stationary state obtained with the use of the proposed model is in reasonable agreement with experimental data.

Facilitating early boreal forest succession on waste rock using Ramial Chipped Wood mulch: A five-year study

After a mine is closed, waste rock storage areas must be revegetated to facilitate the return of ecosystem services and meet legal and social expectations. The restoration of forest ecosystems on waste rock through spontaneous colonization associated with primary succession can take decades and is still poorly studied. Adding a mulch of ramial chipped wood (RCW) could improve the physicochemical properties and microclimate conditions of waste rock, thus facilitating substrate colonization by plants. In 2016, a fully randomized block design was installed on waste rock from a closed gold mine located in the boreal forest in Abitibi-Témiscamingue, Quebec, Canada. The design included four treatments: scarified waste rock as the control (WR), 2 cm of RCW mulch on top of scarified waste rock (RCW/WR), and 10 cm layer of sand on top of scarified waste rock with or without 2 cm of RCW mulch (RCW/S and S, respectively). Over a period of five years, we followed the natural colonization of forest species as well as abiotic (substrate microclimate conditions and physicochemistry) and biotic (herbaceous plant colonization) factors influencing woody plant colonization success. Six boreal woody species spontaneously colonized the area (five individuals per m2, on average, all species combined). Salix sp. and Picea glauca seedlings were more abundant on substrates with RCW mulch (especially sand) than those without mulch, and P. glauca had greater aerial biomasses with RCW mulch. Substrate water content during the growing season and the presence of the weed species Tussilago farfara were determining environmental factors in substrate colonization by Abies balsamea. In the absence of Tussilago farfara, RCW mulch increased A. balsamea colonization. RCW mulch increased the total cover of colonizing herbaceous plants (23.3–58.2%) as compared to mineral substrates alone (4.78–52.3%), which negatively affected the number of A. balsamea individuals. The colonizing herbaceous species were mostly primary succession species, Pilosella caespitosa, Anaphalis margaritacea, and Tussilago farfara being dominant; no exotic species were observed. The results highlight the potential of RCW mulch in promoting forest recolonization on waste rock, including mid-successional species like Picea sp., which could be useful for facilitating ecosystem succession in post-mining landscapes.

The Molecular Profile of Soil Microbial Communities Inhabiting a Cambrian Host Rock.

The process of soil genesis unfolds as pioneering microbial communities colonize mineral substrates, enriching them with biomolecules released from bedrock. The resultant intricate surface units emerge from a complex interplay among microbiota and plant communities. Under these conditions, host rocks undergo initial weathering through microbial activity, rendering them far from pristine and challenging the quest for biomarkers in ancient sedimentary rocks. In addressing this challenge, a comprehensive analysis utilizing Gas Chromatography Mass Spectrometry (GC-MS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was conducted on a 520-Ma-old Cambrian rock. This investigation revealed a diverse molecular assemblage with comprising alkanols, sterols, fatty acids, glycerolipids, wax esters, and nitrogen-bearing compounds. Notably, elevated levels of bacterial C16, C18 and C14 fatty acids, iso and anteiso methyl-branched fatty acids, as well as fungal sterols, long-chained fatty acids, and alcohols, consistently align with a consortium of bacteria and fungi accessing complex organic matter within a soil-type ecosystem. The prominence of bacterial and fungal lipids alongside maturity indicators denotes derivation from heterotrophic activity rather than ancient preservation or marine sources. Moreover, the identification of long-chain (>C22) n-alkanols, even-carbon-numbered long chain (>C20) fatty acids, and campesterol, as well as stigmastanol, provides confirmation of plant residue inputs. Furthermore, findings highlight the ability of contemporary soil microbiota to inhabit rocky substrates actively, requiring strict contamination controls when evaluating ancient molecular biosignatures or extraterrestrial materials collected.

Fluorescence Microscopy with Deep UV, Near UV, and Visible Excitation for In Situ Detection of Microorganisms.

We report a simple, inexpensive design of a fluorescence microscope with light-emitting diode (LED) excitation for detection of labeled and unlabeled microorganisms in mineral substrates. The use of deep UV (DUV) excitation with visible emission requires no specialized optics or slides and can be implemented easily and inexpensively using an oblique illumination geometry. DUV excitation (<280 nm) is preferable to near UV (365 nm) for avoidance of mineral autofluorescence. When excited with DUV, unpigmented bacteria show two emission peaks: one in the near UV ∼320 nm, corresponding to proteins, and another peak in the blue to green range, corresponding to flavins and/or reduced nicotinamide adenine dinucleotide (NADH). Many commonly used dyes also show secondary excitation peaks in the DUV, with identical emission spectra and quantum yields as their primary peak. However, DUV fails to excite key biosignature molecules, especially chlorophyll in cyanobacteria. Visible excitation (violet to blue) also results in less mineral autofluorescence than near UV, and most autofluorescence in the minerals seen here is green, so that red dyes and red autofluorescence of chlorophyll and porphyrins are readily distinguished. The pairing of DUV and near UV or visible excitation, with emission across the visible, represents the most thorough approach to detection of labeled and unlabeled bacteria in soil and rock.

The most suitable system to grind the whole tooth to use it as graft material

Aim: In regenerative dentistry, the success is influenced by the graft material, which should act as an osteoconductive scaffold. It provides a mineral substrate during resorption and induces the activity of osteoinductive cells capable of producing new bone, platelet growth factors, and cell differentiation factors that guide the differentiation of undifferentiated mesenchymal cells. Given that dentin shares many biochemical characteristics with bone tissue, it has recently attracted considerable interest as a biomaterial for bone repair. The aim of this study is to compare two grinder types to determine the optimal method for producing dentinal particles using a mechanical grinder. Methods: A sample of 40 natural human teeth without restorations, prostheses, or root canal treatments was used and divided into two groups subjected to two different grinder speeds (high-speed and low-speed). Results: The high-speed showed a greater dispersion (53.5% ± 9.89% of the tooth) due to the pulverisation (highly thin granules) of part of the tooth. The low-speed grinder did not pulverize the dentin and the percentage of tooth loss is 9.16% ± 2.34%. Conclusions: The low-speed grinder allows to save a major part of the tooth and has a maximum quantity of graft material but requires more time. Further studies must be promoted to optimise the grinding procedures.

The use of fluorescence lifetime imaging (FLIM) for in situ microbial detection in complex mineral substrates.

The utility of fluorescence lifetime imaging microscopy (FLIM) for identifying bacteria in complex mineral matrices was investigated. Baseline signals from unlabelled Bacillus subtilis and Euglena gracilis, and Bacillus subtilis labelled with SYTO 9 were obtained using two-photon excitation at 730, 750 and 800nm, identifying characteristic lifetimes of photosynthetic pigments, unpigmented cellular autofluorescence, and SYTO 9. Labelled and unlabelled B. subtilis were seeded onto marble and gypsum samples containing endolithic photosynthetic cyanobacteria and the ability to distinguish cells from mineral autofluorescence and nonspecific dye staining was examined in parallel with ordinary multichannel confocal imaging. It was found that FLIM enabled discrimination of SYTO 9 labelled cells from background, but that the lifetime of SYTO 9 was shorter in cells on minerals than in pure culture under our conditions. Photosynthetic microorganisms were easily observed using both FLIM and confocal. Unlabelled, nonpigmented bacteria showed weak signals that were difficult to distinguish from background when minerals were present, though cellular autofluorescence consistent with NAD(P)H could be seen in pure cultures, and phasor analysis permitted detection on rocks. Gypsum and marble samples showed similar autofluorescence profiles, with little autofluorescence in the yellow-to-red range. Lifetime or time-gated imaging may prove a useful tool for environmental microbiology. LAY DESCRIPTION: The standard method of bacterial enumeration is to label the cells with a fluorescent dye and count them under high-power fluorescence microscopy. However, this can be difficult when the cells are embedded in soil and rock due to fluorescence from the surrounding minerals and dye binding to ambiguous features of the substrate. The use of fluorescence lifetime imaging (FLIM) can disambiguate these signals and allow for improved detection of bacteria in environmental samples.

Effect of lignite substrate compared to mineral wool and supplementary lighting with HPS and LED on growth, plant photosynthetic activity, yield and fruit quality of greenhouse cucumber

The substrate in hydroponic cultivation is one of the basic factors for proper plant growth, and current environmental trends suggest replacing the previously used mineral wool with organic substrates. Light is also essential for proper plant growth, which is why LEDs (Light Emitting Diode) are increasingly used to provide plants with supplementary light, allowing, among other things, to control the spectral composition. The aim of this study was to determine the effect of lignite substrate and LED supplementary lighting on morphological and physiological parameters as well as quality and yield of cucumber (Cucumis sativus L.) in hydroponic cultivation compared to the cultivation in mineral wool substrate. Lignite mats applied in cultivation with LED supplementary lighting had a beneficial effect on cucumber plant growth and development and plant nutrition in Fe, K, P, Ca, Mg and Zn compared to cultivation in mineral substrate and HPS supplementary lighting. The combination of LED lighting and lignite mats also improved the physiological parameters of the cucumber plants, as well as fruit hardness. Fruits harvested from plants grown in lignite substrate and supplemented with LEDs had the lowest nitrate content and increased TSS value, as well as increased fruit firmness.

A solid substrate based on clay minerals for sampling organic liquids in molecular LIBS analysis

A clay mineral substrate based on a mixture of bentonite and sepiolite allows the direct molecular LIBS analysis of flammable liquids, such as toluene, gasoline and diesel.

Uptake and reactivity of NO2 on the hydroxylated silica surface: A source of reactive oxygen species

We report state-of-the-art first-principles molecular dynamics results on the heterogeneous chemical uptake of NO2, a major anthropogenic pollutant, on the dry and wet hydroxylated surface of α-quartz, which is a significant component of silica-based catalysts and atmospheric dust aerosols. Our investigation spotlights an unexpected chemical pathway by which NO2 (i) can be adsorbed as HONO by deprotonation of interfacial silanols (i.e., –Si–OH group) on silica, (ii) can be barrierless converted to nitric acid, and (iii) can finally dissociated to surface bounded NO and hydroxyl gas phase radicals. This chemical pathway does not invoke any previously experimentally postulated NO2 dimerization, dimerization that is less likely to occur at low NO2 concentrations. Moreover, water significantly catalyzes the HONO formation and the dissociation of nitric acid into surface-bounded NO and OH radicals, while visible light adsorption can further promote these chemical transformations. This work highlights how water-restricted solvation regimes on common mineral substrates are likely to be a source of reactive oxygen species, and it offers a theoretical framework for further and desirable experimental efforts, aiming to better constrain trace gases/mineral interactions at different relative humidity conditions.

In Vitro Experimental Observations on Fungal Colonization, Metalophagus Behavior, Tunneling, Bioleaching and Bioweathering of Multiple Mineral Substrates

This study reports on experimental observations during fungi–mineral substrate interactions. Selected mineral substrates of biotite, muscovite, bauxite, chromite, galena, malachite, manganite, and plagioclase were exposed in vitro to free fungal growth under open conditions. The interaction produced strong biochemical and biomechanical alterations to the mineral substrates. Specifically, reported here is a three-dimensional thigmotropic colonization pattern of the mineral surfaces that suggested a possible pattern of fungal metalophagus behavior. Authigenic secondary mineral biomineralization occurred: Ca- and Mg-Oxalates such as weddellite: CaC2O4·2H2O, whewellite: CaC2O4·H2O, and glushinskite: MgC2O4·2H2O; struvite: (NH4) MgPO4·6H2O; gibbsite: Al(OH)3; and gypsum: CaSO4·2H2O. The bioleached elements included Fe, Pb, S, Cu, and Al, which formed single crystals or aggregates, amorphous layers, amorphous aggregates, and linear forms influenced by the fungal filaments. The fungi bioleached Fe and Al from bauxite and Mn from manganite and deposited the metals as separate mineral species. Gypsum was deposited during the interaction with the manganite substrate, indicating a source of Ca and S either within manganite impurities or within the fungal growth environment. Other biochemical and biomechanical features such as tunneling, strong pitting, exfoliation, dissolution, perforations, and fragmentation of the mineral surfaces were also produced. The results of this study, besides emphasizing the role of fungi in bioweathering and mineral alteration, also show that, to produce these alterations, fungi employ a 3D fungal colonization pattern of mineral surfaces guided by thigmotropic and possible metalophagus behavior.