Exogenous Mineral Research Articles

Physico-chemical aspects of uranium extraction for investigation of underground well leaching control systems

This article gives the physical and chemical aspects of uranium extraction from the zones of reservoir oxidation using ultrasonic technology and the theoretical justification for the technology of in-situ borehole leaching (ISL) of uranium deposits in Kazakhstan. Kazakhstan has significant reserves, well-explored uranium deposits, developed uranium mining and processing capacities, as well as the current state of the world uranium market, which determine the prospects for the development of the uranium mining industry in Kazakhstan. Ore deposits of uranium deposits localized at the fronts of seam oxidation zones are largely similar in terms of the chemical composition of host rocks. Fe, Al, Mg, Ca, K, and Na are among the most widespread petrogenic elements of rock-forming minerals. Uranium is observed in association with iron, vanadium, selenium, molybdenum, rhenium, and other elements. Uranium mineralization is represented by exogenous (secondary) minerals – pitchblende and coffinite. In the general balance of uranium minerals, pitchblende is about 30%, and coffinite is about 70%. Nasturan (хUO2×yUO3×z) is represented by an association of tetravalent uranium dioxide and hexavalent uranium trioxide with a variable composition (UO2+UO3) - 65-85%, coffinite - tetravalent uranium silicate USiO4.

Soft-Tissue, Rare Earth Element, and Molecular Analyses of Dreadnoughtus schrani, an Exceptionally Complete Titanosaur from Argentina.

Simple SummaryAlthough many analytical techniques have shown that organic material can be preserved in fossils for millions of years, the geochemical factors that allow this preservation are not well understood. This is partly because paleomolecular studies often do not include geochemical analyses of the fossil or burial environment from which it came. We conducted in-depth geological, geochemical, and molecular analyses of a specimen of Dreadnoughtus schrani, an immense dinosaur from Argentina. We reviewed physical aspects of the sediments in which Dreadnoughtus was deposited, then characterize the following features: the structural integrity of the bone microstructure; the amount and type of external mineral that infiltrated the bone; the concentration of elements that are rare in the Earth’s crust (REEs) throughout the bone; the preservation of soft-tissue structures (e.g., bone cells and blood vessels); the preservation of bone protein using antibodies that specifically recognize collagen I. Our data show that original bone microstructures and protein are preserved in Dreadnoughtus, and that after burial, the specimen was exposed to weakly-oxidizing conditions and groundwaters rich in “light” REEs but experienced little further chemical alteration after this early stage of fossilization. Our findings support the idea that fossils showing lower concentrations of REEs are well suited for molecular analyses.Evidence that organic material preserves in deep time (>1 Ma) has been reported using a wide variety of analytical techniques. However, the comprehensive geochemical data that could aid in building robust hypotheses for how soft-tissues persist over millions of years are lacking from most paleomolecular reports. Here, we analyze the molecular preservation and taphonomic history of the Dreadnougtus schrani holotype (MPM-PV 1156) at both macroscopic and microscopic levels. We review the stratigraphy, depositional setting, and physical taphonomy of the D. schrani skeletal assemblage, and extensively characterize the preservation and taphonomic history of the humerus at a micro-scale via: (1) histological analysis (structural integrity) and X-ray diffraction (exogenous mineral content); (2) laser ablation-inductively coupled plasma mass spectrometry (analyses of rare earth element content throughout cortex); (3) demineralization and optical microscopy (soft-tissue microstructures); (4) in situ and in-solution immunological assays (presence of endogenous protein). Our data show the D. schrani holotype preserves soft-tissue microstructures and remnants of endogenous bone protein. Further, it was exposed to LREE-enriched groundwaters and weakly-oxidizing conditions after burial, but experienced negligible further chemical alteration after early-diagenetic fossilization. These findings support previous hypotheses that fossils that display low trace element uptake are favorable targets for paleomolecular analyses.

Effect of the combined addition of mineral nitrogen and crop residue on soil respiration, organic carbon sequestration, and exogenous nitrogen in stable organic matter

Nitrogen fertilization can change soil respiration via microbial biomass, which affects the decomposition of soil organic matter (SOM) and plant residues. The quantitative influence and underlying mechanisms of mineral N and the combination of straw and N on stable organic N (humus) are still unclear. To explore the mechanisms of the conversion of mineral N to stable organic N (humus N), we performed incubation experiments using 13C natural abundance and 15N isotope labeling techniques with four treatments: control, added straw (St), added N (N), and added straw and N (St + N). The effect of N addition on the CO2 emission rate and cumulative CO2 emissions showed a prominent two-phase characteristic: both the CO2 emission rate and cumulative production were stimulated by exogenous mineral N during the initial stage, while the CO2 emission rate gradually decreased during the middle and later stages; however, residual C may remain in the soil for a longer time, leading to great differences in soil C/N ratios at different stages. This indicates that added N was rapidly utilized by microorganisms. At the end of the incubation period, the proportion of 15N derived from labeled N to total N in humus was 0.063% (N) and 0.085% (St + N), while the proportion of 15N in humus to total mineral N added was 0.41% and 0.64%, respectively. This indicated that even if only mineral N was added, the stable organic N in humus was converted by microbes. Compared with the addition of only mineral N, the combination of N and straw promoted the conversion of mineral N to stable organic N. The results of this study clarify the effect of mineral N on stable organic N and associated SOC mineralization, and can thus be used to develop strategies to improve soil fertility or mitigate climate change by increasing the SOC.

Potential of pineapple peel in the alternative composition of culture media for biosurfactant production.

The large pineapple's consumption and processing have generated a massive amount of waste yearly, which requires adequate treatment measures to avoid damages to the environment. Pineapple peel is one of the main residues obtained from this fruit and a promising strategy to take advantage of its potential is using it for biosurfactant production due to the peel's rich composition in fermentable sugars and nutrients, such as potassium and magnesium that favor the Bacillus subtilis growth and biosurfactant excretion as well. The current research performed a central composite design (CCD) with four independent variables (glucose, pineapple peel, potassium, and magnesium), evaluating substrates' influence on the surface tension reduction rate (STRR) and the emulsification index (EI24). The results indicated that pineapple peel has the necessary potential to act as a partial substitute for glucose and salt nutrients, minimizing the costs of supplementing with exogenous minerals. The highest surface tension reduction rate (57.744%) was obtained at 2.18% glucose (w/v); 14.67% pineapple peel (v/v); 2.38 g/L KH2PO4; and 0.15 g/L MgSO4.7H2O; whereas to obtain the maximum predicted value for EI24 (61.92%) the medium was composed by 2.24% glucose (w/v); 12.63% pineapple peel (v/v); 2.53 g/L KH2PO4; and 0.29 g/L MgSO4.7H2O.

Assessment of pesticide residues, exogenous heavy metals and essential minerals in spinach after cleaning with traditional methodologies

ABSTRACT Green leafy vegetables are a rich source of micronutrients but can usually contain contaminants such as pesticides and toxic heavy metals. In this work, we have evaluated the effectiveness of washing with tap water, vinegar-acidified water and basified water with sodium bicarbonate in eliminating three pesticides (methomyl, deltamethrin and lambda-cyhalothrin) and some exogenous heavy metals. The HPLC-UV method was validated for pesticides analysis in vegetable matrices using the QuEChERS method extraction. The results showed that a ca. of 57 to 71% and 73 to 97% of the 3 pesticides are removed after washing with acidified and basified water, respectively. On the other hand, the ICP-MS method was used for analysing heavy metals and essentials elements in spinach. Washing with both acidic and alkaline water removed a part of toxic heavy metals. The decrease in metals concentrations indicated that, probably, the metals contamination of vegetables was mainly through the foliar deposition. Acidified and basified water solubilise small particles containing these exogenous metals In conclusion, the performance of washing with the basic medium was better to remove pesticides and some of exogenous toxic heavy metals from the surfaces of spinach leaves and to preserve the essential elements of the plant.

Pedogenic clay formation from allochthonous parent materials in a periglacial alpine critical zone

This project investigated the origin of clay minerals in regolith present above quartzite bedrock in the alpine zone of the Uinta Mountains, Utah, USA. Geochemical and mineralogical analysis indicates that these clays formed through chemical weathering of two allochthonous parent materials. Smectite-rich clays, with Mg abundance distinctly higher than modern dust or local bedrock, formed through weathering of andesitic ash layers that were deposited during the Oligocene from eruptive centers in the Basin and Range. In contrast, various stages of interstratified kaolinite-illite–smectite clays have formed through weathering of mica and feldspar delivered by eolian processes that continue today. Local bedrock appears to have played only a minor role as a parent material for clay neoformation. These results demonstrate that pedogenic clay can be common even in cold climate soils and regolith overlying weathering resistant bedrock. They also emphasize that the clay inventory in soil and regolith can reflect processes that operated before modern climatic conditions were established, and reinforce the key role played by exogenous mineral inputs in the functioning of the alpine critical zone.

A new hypothesis for the origin of Amazonian Dark Earths

Amazonian Dark Earths (ADEs) are unusually fertile soils characterised by elevated concentrations of microscopic charcoal particles, which confer their distinctive colouration. Frequent occurrences of pre-Columbian artefacts at ADE sites led to their ubiquitous classification as Anthrosols (soils of anthropic origin). However, it remains unclear how indigenous peoples created areas of high fertility in one of the most nutrient-impoverished environments on Earth. Here, we report new data from a well-studied ADE site in the Brazilian Amazon, which compel us to reconsider its anthropic origin. The amounts of phosphorus and calcium—two of the least abundant macronutrients in the region—are orders of magnitude higher in ADE profiles than in the surrounding soil. The elevated levels of phosphorus and calcium, which are often interpreted as evidence of human activity at other sites, correlate spatially with trace elements that indicate exogenous mineral sources rather than in situ deposition. Stable isotope ratios of neodymium, strontium, and radiocarbon activity of microcharcoal particles also indicate exogenous inputs from alluvial deposition of carbon and mineral elements to ADE profiles, beginning several thousands of years before the earliest evidence of soil management for plant cultivation in the region. Our data suggest that indigenous peoples harnessed natural processes of landscape formation, which led to the unique properties of ADEs, but were not responsible for their genesis. If corroborated elsewhere, this hypothesis would transform our understanding of human influence in Amazonia, opening new frontiers for the sustainable use of tropical landscapes going forward.

Impacts of exogenous mineral silicon on cadmium migration and transformation in the soil-rice system and on soil health

Exogenous silicon has been shown to enhance plant growth and alleviate heavy metals toxicity, but the regulation mechanism of silicon on cadmium migration and transformation in the soil-rice system is still unclear, which is worth further study. In this study, a pot experiment was carried out to explore the influence of different doses (0, 1 and 5%) of mineral silicon on soil properties, nutrient availability, rice growth, soil enzyme activities, Cd bioavailability, and uptake and accumulation of Cd in high-accumulating (H) and low-accumulating (L) rice cultivars grown in contaminated soils. Results showed that mineral-Si treatment could increase the total biomass and grain yield, with an increased rate of 17.7–27.3% and 14.7–19.1% for H; while 26.2–33.4% and 21.3–30.3% for L. Compared with non-mineral-Si treatment, the soil EX-Cd decreased by 3.9–13.3% (H) and 2.3–10.7% (L). Additionally, the Cd content in rice grain was significantly declined by 29.5–31.3% (H) and 34.9–35.2% (L). Mineral-Si enhanced urease, sucrase, and neutral phosphatase activities in both cultivars, but suppressed catalase activity in H. A selective change in bacterial community structure was observed under mineral-Si treatment, however, the bacterial community remained stable, suggesting that the mineral-Si had no adverse effect on the microbial community. The positive response of soil enzymes activities, rice growth and the overall stabilization of microbial environment for mineral-Si addition to the Cd contaminated soils indicated that mineral-Si could mitigate the risk of Cd and well maintain the soil health, proving it to be eco-friendly and low-cost amendment for soils remediation.

Mineralogical Record for Stepwise Hydroclimatic Changes in Lake Qinghai Sediments Since the Last Glacial Period

Lake Qinghai is sensitive to climatic changes because of its pivotal location between mid-latitude Westerlies and the low-latitude East Asian monsoon. An 18.6 m long drilling core (1Fs) from Lake Qinghai provides new information on the hydroclimatic dynamics since the last glacial period. Here, we present the results of bulk mineral assemblages of this core. X-ray diffraction (XRD) results showed that the bulk minerals of the core sediments consist of major clastic minerals (e.g., quartz, feldspar, muscovite), carbonates (e.g., calcite, aragonite, dolomite), and minor clay minerals (e.g., chlorite). Quartz as an exogenous detrital mineral in lake sediments, its abundance is related to lake level changes resulting from regional climate changes via fluvial/aeolian transportation. Aragonite was precipitated from water solutions or chemical alteration of pre-existing minerals or biogenic mediation, closely related to lake hydroclimate change. Mineral assemblages revealed remarkable stepwise hydroclimatic changes. High quartz content and low calcite without aragonite suggested a cold-wet climate condition under predominant westerlies during the last glacial period from 35 to 25.3 ka. Afterward, quartz decreased and aragonite occasionally appeared, indicating an unstable hydroclimatic condition during the last deglaciation. Since the Early Holocene (11.9–8.2 ka), predominant minerals shifted from terrigenous quartz to authigenic carbonates, suggesting an increasing lake level, possibly due to intensified Asian summer monsoon with increased effective moisture. Aragonite became the primary carbonate mineral, implying a warming and humid hydroclimate environment with a relatively higher lake-level. During the Middle Holocene (8.2–4.2 ka), aragonite showed a decreasing trend indicating a higher lake level with weak evaporation. During the Late Holocene since 4.2 ka, there were lower quartz and aragonite, suggesting a deep lake with a weak summer monsoon. Our quartz and carbonate minerals record provided essential clues to reconstruct hydroclimate change in Lake Qinghai since the last glacial period.

The Mineral Composition and Sources of the Fine-Grained Sediments from the 49.6°E Hydrothermal Field at the SWIR

We used the X-ray diffraction method to determine systematically the mineral phases in bulk sediment samples and acid undissolved residuals of the fine-grained fraction of the surface sediments from the 49.6°E hydrothermal field at the Southwest Indian Ridge (SWIR) and discussed the mineral sources of the surface sediments. The results showed that the surface sediments in this region were composed of calcareous ooze, and calcite was the dominant mineral. The sediments also contained quartz, feldspar, clay minerals, pyroxene, sphalerite, barite, serpentine, and magnetite. The quartz, feldspar, and clay minerals were exogenous minerals that mainly originated from the Namib and Kalahari deserts in southern Africa. The pyroxene, serpentine, magnetite, sphalerite, calcite, and barite were endogenous minerals from weathering of seafloor basement rocks and seafloor hydrothermal activities. The sulfide particles in the sediments were mainly deposited from upwelling plumes.

NEW DATA ON SEASONAL MINERALS OF MUD VOLCANOES IN AZERBAIJAN

The article discusses the morphology and material composition of seasonal minerals of mud volcanoes in Azerbaijan Mud volcanism is a complex and rather unexplored geological phenomenon. Mud volcanoes are known in Turkmenistan, Dagestan, Georgia, Sakhalin, Taman Peninsula, Crimea, Azerbaijan and many regions of the World. In the geological literature, this phenomenon has been widely reflected. The bibliography of scientific works on mud volcanism has hundreds of titles. One of the classic areas of mud volcano development is Azerbaijan. In the process of geological research in recent decades, a huge geological material has been accumulated on the mud volcanism of Azerbaijan. The described types of mud volcanoes eruptions and the material composition of the mound breccia, it was possible to discover new interesting facts of unusual mineralogical finds. Of particular interest are authigenic minerals formed directly from the water phase of mud volcanoes and are seasonal. Their formation indicates that mineral formation processes are active in these natural sites. The occurrence of seasonal minerals is controlled by several factors, including the climatic conditions of the region. Main part of such minerals crystallizes only in dry and warm weather, which makes their systematic research much more difficult. The sodium hydroxide described in the article, which is very unstable under natural conditions, is a confirmation of this. However, even for a short interval of the existence of seasonal minerals, studying the features of their composition, one can obtain important information for genetic constructions. In addition to exogenous minerals of the weathering zone, the article also describes molybdenite associated with hydrothermal processes. The study of the mineral component of both endogenous and exogenous processes makes it possible to assess their evolution, the direction of the geological development of mud volcanoes in the region.

Petrographical and geochemical characterization of the inertinite-rich coal from the Ningdong Coalfield, Northwest Ordos Basin, China

This study deals with the coal petrographical and geochemical characteristics of the #2 and #6 coal seams in the Ningdong Coalfield, Northwest Ordos Basin. Proximate analysis, sulfur forms, ash composition, trace element contents along with macral analysis, and X-ray diffraction were performed on the coal samples. The Ningdong coal was deposited in a large continental (freshwater) basin, which resulted in very low ash yield and total sulfur contents (7.63 and 0.35% on average, respectively), with organic sulfur being the dominant sulfur form. The average random vitrinite reflectance of #2 and #6 seams are 0.49 and 0.60%, respectively, indicating a low metamorphic grade. Inertinite is the most abundant group in the Ningdong coal (50.1% on average), whereas, the vitrinite and liptinite contents are 44.2 and 2.4%, on average, respectively. SiO2 is the major coal ash component (35.57%), whereas, the Al2O3, CaO, and Fe2O3 contents also exceed 10% of the crystalline phases. Trace element contents are low in general; a lot of them are less than the respective World hard coal values. At the same time, the contents of Sc, Cr, Mn, Cu, Y, La, Tl, Pb, Th, U, Cs, Yb, and Hf are close to the average values of the World hard coal, with Mn and Sr even slightly enriched in the #6 and #2 seam, respectively. Analysis shows that Si, Al, K, Ti, Li, Cr, Nb, Pb, Th, Cd, In, Hf, and Ta are mainly hosted in the exogenous minerals and Ca, Mg, and Na mainly come from the endogenous minerals. The flat and wide basin structure along with the paleomire supply with fresh water are the major reasons of the special petrographical and geochemical feature of the Ningdong coal.

Effects of magnesium impregnation on stability and sorption performance of biochar derived from sawdust and corn husks

Biochar was derived from MgCl2 and MgO pretreated sawdust and corn husks at 300 °C and 600 °C, respectively, to investigate the effects of exogenous minerals on the stability and sorption performance of the resulting biochar. Impregnation with Mg decreased carbon concentration, increased yield and ash concentration, and increased the pH values at the point of zero charge (pHPZC) of the resulting biochar. The chemical stability of biochar oxidized by K2CrO7 was enhanced with increasing pyrolysis temperature and decreased with the pretreatment of MgCl2 and MgO. Mg-impregnation enhanced carbon loss of the resulting biochar and increased the sorption capacity of biochar for CR significantly, which is potentially caused by electrostatic interaction and surface complexation. This study indicates that magnesium-impregnation significantly enhances the sorption performance of anionic contaminants and the pyrolysis temperature has a greater effect on the stability of the resulting biochar than the magnesium-impregnation.

Exogenous mineralization of hard tissues using photo-absorptive minerals and femto-second lasers; the case of dental enamel

A radical new methodology for the exogenous mineralization of hard tissues is demonstrated in the context of laser-biomaterials interaction. The proposed approach is based on the use of femtosecond pulsed lasers (fs) and Fe3+-doped calcium phosphate minerals (specifically in this work fluorapatite powder containing Fe2O3 nanoparticles (NP)). A layer of the synthetic powder is applied to the surface of eroded bovine enamel and is irradiated with a fs laser (1040 nm wavelength, 1 GHz repetition rate, 150 fs pulse duration and 0.4 W average power). The Fe2O3 NPs absorb the light and may act as thermal antennae, dissipating energy to the vicinal mineral phase. Such a photothermal process triggers the sintering and densification of the surrounding calcium phosphate crystals thereby forming a new, dense layer of typically ∼20 μm in thickness, which is bonded to the underlying surface of the natural enamel. The dispersed iron oxide NPs, ensure the localization of temperature excursion, minimizing collateral thermal damage to the surrounding natural tissue during laser irradiation. Simulated brushing trials (pH cycle and mechanical force) on the synthetic layer show that the sintered material is more acid resistant than the natural mineral of enamel. Furthermore, nano-indentation confirms that the hardness and Young’s modulus of the new layers are significantly more closely matched to enamel than current restorative materials used in clinical dentistry. Although the results presented herein are exemplified in the context of bovine enamel restoration, the methodology may be more widely applicable to human enamel and other hard-tissue regenerative engineering. Statement of significanceIn this work we provide a new methodology for the mineralisation of dental hard tissues using femtosecond lasers and iron doped biomaterials. In particular, we demonstrate selective laser sintering of an iron doped fluorapatite on the surface of eroded enamel under low average power and mid-IR wavelength and the formation of a new layer to substitute the removed material. The new layer is evaluated through simulated brushing trials and nano-indentation. From the results we can conclude that is more acid resistant than natural enamel while, its mechanical properties are superior to that of current restorative materials. To the best of our knowledge this is the first time that someone demonstrated, laser sintering and bonding of calcium phosphate biomaterials on hard tissues. Although we here we discuss the case of dental enamel, similar approach can be adopted for other hard tissues, leading to new strategies for the fixation of bone/tooth defects.

Effects of copyrolysis of sludge with calcium carbonate and calcium hydrogen phosphate on chemical stability of carbon and release of toxic elements in the resultant biochars

The potential release of toxic elements and the stability of carbon in sludge-based biochars are important on their application in soil remediation and wastewater treatment. In this study, municipal sludge was co-pyrolyzed with calcium carbonate (CaCO3) and calcium dihydrogen phosphate [Ca(H2PO4)2] under 300 and 600 °C, respectively. The basic physicochemical properties of the resultant biochars were characterized and laboratory chemical oxidation and leaching experiments of toxic elements were conducted to evaluate the chemical stability of carbon in biochars and the potential release of toxic elements from biochars. Results show that the exogenous minerals changed the physico-chemical properties of the resultant biochars greatly. Biochars with exogenous minerals, especially Ca(H2PO4)2, decreased the release of Zn, Cr, Ni, Cu, Pb, and As and the release ratios were less than 1%. Tessier's sequential extraction analysis revealed that labile toxic elements were transferred to residual fraction in the biochars with high pyrolysis temperature (600 °C) and exogenous minerals. Low risks for biochar-bound Pb, Zn, Cd, As, Cr, and Cu were confirmed according to risk assessment code (RAC) while the potential ecological risk index (PERI) revealed that the exogenous Ca(H2PO4)2 significantly decreased the risks from considerable to moderate level. Moreover, the exogenous minerals significantly increased the chemical stability of carbon in 600 °C-pyrolyzed biochars by 10–20%. These results indicated that the copyrolysis of sludge with phosphate and carbonate, especially phosphate, were effective methods to prepare the sludge-based biochars with immobilized toxic elements and enhanced chemical stability of carbon.

Effects of residue quality and soil mineral N on microbial activities and soil aggregation in a tropical sandy soil in Senegal

The role played by organic residues and exogenous mineral N in the formation of stable soil aggregates in nutrient-poor, tropical sandy soils of Senegal is relatively unclear. This study assessed the effect of two representative low and high quality residues (Zea mays and Crotalaria retusa respectively) on the formation and stability of soil aggregates. The formation and stability of aggregates, soil biomass, root biomass, fungal hyphae length, C mineralization and chitinase activity, as a specific biomarker of the activity of fungal populations, were measured under controlled conditions over 120 days. In both the control and amended soils, there were more macroaggregates (>2000 μm) and mesoaggregates (250–2000 μm) than microaggregates (50–250 μm and <50 μm). The formation of macroaggregates and stability (MWD) were not significantly affected by the quality of residues. Amendment with organic residues shifted the distribution of the aggregate fractions. The macroaggregates increased by 26% with crotalaria and by 35% with maize residues while mesoaggregates decreased by 18% with crotalaria and by 26% with maize residues and microaggregates decreased by 8% with crotalaria and by 9% with maize residues. This study also confirmed that macroaggregates are formed from micro- and mesoaggregates. The total microbial biomass was significantly higher in soil amended with maize residues compared to soil with crotalaria residues and the control soil although the fungal hyphae length decreased when the soil was amended with either crop residue. Chitinase activity is the most pertinent indicator associated with macroaggregation stability. Adding mineral N (equivalent to 120 kg N ha−1 as urea) to the residue increased microbial biomass and reduced fungal hyphae length but had no effect on macroaggregate formation and fungal activity. These observations suggested that, for short term incubation of soil amended with residues, fungal activity plays a greater role in aggregation in sandy soils than the fungal population density.

Exogenous Mineral Regulation Under Heavy Metal Stress: Advances and Prospects

Heavy metals (HMs) contaminate the soil through various natural and anthropogenic resources and are transported to the plant systems. These heavy metals are translocated within the plant system by the apoplast and symplast through various transporters such as HMAs, ZIP, ABC. HMs disturb plant metabolism, cause oxidative stress and nutrient dearth. Many researchers have applied exogenous minerals to alleviate these negative impacts caused by HMs. Minerals mitigate the HMAs induced negative impacts by the enhancement of biochemical reactions and physiological processes in plants. In the present article the role of exogenous mineral regulation under heavy metal toxicity is being discussed.

Exogenous mineralization of cell-seeded and unseeded collagen–chitosan hydrogels using modified culture medium

Induced biomineralization of materials has been employed as a strategy to increase integration with host tissue, and more recently as a method to control cell function in tissue engineering. However, mineralization is typically performed in the absence of cells, since hypertonic solutions that lack the nutrients and culture components required for the maintenance of cell viability are often used. In the present study, we exposed fibroblast-seeded three-dimensional collagen–chitosan hydrogels to a defined culture medium modified to have specific concentrations of ions involved in biomineralization. The modified medium caused a significant increase in calcium deposition in collagen–chitosan gels, relative to constructs incubated in a standard medium, though serum supplementation attenuated mineral deposition. Collagen–chitosan constructs became opaque over 3days of mineralization in modified Dulbecco’s modified Eagle medium (DMEM), in contrast to translucent control gels incubated in standard DMEM. Histological staining confirmed increased levels of mineral in the treated constructs. Rheological characterization showed that both the storage and loss moduli increased significantly in mineralized materials. Mineralization of fibroblast-seeded constructs resulted in decreased cell viability and proliferation rate over 3days of incubation in modified medium, but the cell population remained over 75% viable and regained its proliferative potential after rescue in standard culture medium. The ability to mineralize protein matrices in the presence of cells could be useful in creating mechanically stable tissue constructs, as well as to study the effects of the tissue microenvironment on cell function.

Exogenic microbial activity in coals

This work presents studies on the exogenic changes during storage of coal samples. These changes are results of oxidizing and reducing processes. The studied coal samples are of different age and rank. The major applied methods are SEM and XRD. Microorganisms were observed among the newly formed mineralization. The neoformed mineral phases are presented by gypsum, K-jarosite, barite, sulphates of Fe, Mg and Na, sulphur, Fe-oxides/hydroxides and framboidal pyrite. Neoformed mineral bacterial colonies were also established, as well as included cell-like bodies in novel mineral matter. It could be supposed that the microorganisms participate in the formation of exogenic mineralization on the mined coals. Observed spontaneous burning of coals appears to be a result of the activity of aerobic microorganisms.

Genetic model of uranium mineralization in the Permo-Triassic sedimentary rocks of the Stara Planina eastern Serbia

One deposit and four occurrences of uranium minerals in the Permo-Triassic sedimentary rocks of the Stara Planina in eastern Serbia were ascertained using data from years of multidisciplinary geological research. The minerals are the fissure-filling type, and were assigned to the exogenic mineralization group, being mostly epigene in nature. Relevant geological information was used to derive a genetic model of uranium mineralization in the Permo-Triassic sedimentary rocks of the Stara Planina. The model explains the formation of Permo-Triassic rocks and three stages of the complex process of U mineralization. The genetic model treats: (1) the primary sources of the uranium; (2) the mobility of uranium; and (3) accessory metals from the parent rocks to their deposition in host rocks and the postmineral change in ore bodies. A geochemical barrier zone was identified in the sedimentary rocks that contained uranium mineral ore. This geochemical barrier area included crescent-shaped, flat-lens, or vein-like ore bodies. The U-containing mineral described is comparable with those from the relatively common fissure-filling uranium minerals found around the world.