Low Amounts Of Water Research Articles

Analysis of the composition of Brazilian black soybean seeds and mathematical modelling of intermittent drying and extraction of antioxidant compounds using fractional calculus

AbstractThe present study aims to analyze the composition of black soybean seeds, evaluate the intermittent drying of black soybean seeds by fractional calculus, optimize the extraction conditions of the antioxidant compounds by varying the solvent ratio and the extraction time, fit traditional models of extraction kinetics, and compare with the fractional order model. Regarding the oil content, it is analyzed that black soybeans have a high lipid content (18.86%), an oil source of interest for research and industrial applications. Regarding drying, it was found that the first order model cannot be used to describe the kinetics of intermittent drying for black soybean seeds and the best kinetic fits were obtained with the Page and fractional order models, which can be applied in simulations of drying and dryer designs. Regarding the extraction process, ethanol/water 45/55 (v/v) solvent proportion obtained the highest antioxidant compound content during 1 h of extraction. So and MacDonald's and hyperbolic kinetic models presented the best fitting to experimental data. About the fractional order model, it is found that for extraction conditions with more significant amounts of water in the ethanolic solution, the α value obtained is less than 1, resulting in the phenomenon of subdiffusion. For the extraction condition with a low amount of water in the ethanolic solution, the α value was greater than 1, depicting a superdiffusion process.

Drying and rewetting affect the chemical speciation and bioavailability of soil phosphorus in a hyper-arid desert ecosystem

Climate change is expected to alter the frequency and intensity of drying and rewetting cycles, impacting water availability and consequently soil nutrient availability. However, the effects of these fluctuations on the chemical speciation and bioavailability of phosphorus (P) in soil with or without desert species remain uncertain. We conducted a pot experiment involving bare soil and two desert species (Alhagi sparsifolia and Calligonum mongolicum) to determine the short-term impacts of drought (no water supply), drying-rewetting-1 (D-RW1, high frequency of low water amounts), and drying-rewetting-2 (D-RW2, low frequency of high-water amounts) treatments on soil Hedley-P pools, plant P concentration and biomass accumulation. Results demonstrated that the presence of plants significantly increased soil labile-P and organic P (Po) concentrations by 60–150% and 1–68%, respectively, compared to bare soil. Both D-RW1 and D-RW2 treatments significantly increased soil dissolved organic carbon concentration by 2–35% relative to the drought treatment. Moreover, soil resin-P and NaHCO3-Pi concentrations under Alhagi sparsifolia in D-RW1 treatment significantly increased by 31% and 75%, respectively, when compared to the drought treatment, with NaHCO3-Po and NaOH-Po concentrations under D-RW2 treatment rising by 14% and 32%, respectively. Furthermore, D-RW2 treatment significantly increased leaf P concentration and biomass compared to D-RW1 and drought treatments. Overall, compared to drought treatment, frequent low-intensity drying-rewetting cycles enhanced soil Pi turnover, whereas infrequent high-intensity drying-rewetting cycles increased Po turnover and P bioavailability. These findings will inform better water management strategies for desertification restoration in hyper-arid desert ecosystems.

Monitoring fungi and mycotoxin potential in pistachio nuts of Turkish origin: A snap-shot for climate change scenario

Pistachio (Pistacia vera L.) is an economically important tree nut. Due to its nutritional properties and health benefits, it is considered a healthy food and thus widely consumed worldwide. However, fungal contamination of the commodities has received considerable attention because of possible contamination by toxigenic fungi, important source of mycotoxins, resulting from secondary metabolism and hazards to health consumer. Members of the genus Aspergillus, mainly Aspergillus flavus and Aspergillus niger, are reported as occurring most frequently on pistachio nuts, because able to grow in the presence of low amounts of water and to produce mycotoxins (aflatoxins and ochratoxins), that are well known for their harmful health effects on humans.Monitoring the contaminating fungal species is particularly worthy of note also in climate change scenario, allowing to notice changes in fungal population composition through the time.This study aimed to contribute to collect data about fungal population and mycotoxins occurred in pistachio samples collected in Turkey: prevalence of 2 species, A. flavus and Aspergillus tubingensis, was assessed. The A. flavus strains consisted of a mixed population of aflatoxin producers and non-producing strains in vitro, with evidence of a new genotype in gene cluster within strains of aflatoxin non-producing chemotype.

Freezing-Prediction System of Outdoor Horizontal Fire Pipe Using Metal Heater

The method of winding a heating wire and covering it with insulation materials has been widely used to prevent freezing during winter in outdoor firefighting pipes, which have a low amount of water flowing inside. However, several issues must be considered when using a heating wire, such as the hardening of its sheath, the outbreak of fire owing to electric leakage or short-circuiting, and difficulties in maintenance and repair. A freeze-protection system using a metal heater was developed to solve these problems. Thermal flow was analyzed using ANSYS CFX by varying the pipe diameter, insulation thickness, and outdoor temperature. Based on the obtained results, a regression equation was derived to predict the water temperature using the Minitab software. This study defined the recommended installation interval of the metal heater for frost prevention as the point at which the temperature inside the core of the pipe was maintained above 0 °C or higher. Under the same experimental conditions, the recommended installation intervals obtained via thermal fluid and regression analyses were 2.6 and 2.7 m, respectively. These values differed from the recommended installation interval of 2.9 m, derived from the actual experiment, by a maximum of 0.3 m.

Effect of Surface, Subsurface Drip Irrigation and Nanotechnology Perfusion Methods on Irrigation Efficiency and Saved Water Ratio in Plowed and Unplowed Soils

A field experiment was conducted in Al-Habbaniyah district / Al- Khalidiya district / Al-Anbar governorate, western Iraq, in Silty loam soil during the fall season 2020, to study the effect of surface and subsurface drip irrigation and perfusion irrigation with nanotechnology on irrigation efficiency, the amount of added water and the percentage of water saving in plowed and non-plowed soils. Perfusion was done when 50% of the prepared water was depleted. The treatments were distributed according to the Nested-Factorial Experiments Design (NFED) with three replications. The yellow corn, cultivar Euphrates, was planted on 2020/15/7. The American evaporation basin, type A, was used in the timing of irrigation. According to the rate of water consumption in terms of the equivalent depth of the added water, the total yield and the efficiency of water use. The results of the study showed the uniqueness of the drip irrigation system by giving the highest irrigation efficiency of 100% for the two plowing modes, while the surface drip irrigation system gave an irrigation efficiency of 83% in the uncultivated soil, and the lowest amount of water was added during the season, which amounted to 5215 m3. ha-1 in the nano-technology perfusion irrigation method with a savings rate of 29.97 and 13.19% compared with the surface drip irrigation method, while it reached 15.23 and 8% compared with the subsurface drip irrigation method in the plowed and non-plowed soils sequentially, the highest average total production was 11.7 tons of grain per hectare for the tillage and no-till treatment, and it decreased significantly to 7.5 tons ha-1 in the surface drip irrigation method, while the tillage treatments did not record significant differences in the short-term grain yield.

Reduction of Dinitrobenzene Derivatives in Ethaline: Hydrogen‐Bonding Interactions through the Inversion of Potentials in a Deep Eutectic Solvent

AbstractThe reduction of dinitro‐benzene derivatives have been examined in Ethaline containing a low amount of water (less than 0.2 %) chosen as a prototypical example of Type III‐DES. Analyses of the voltammograms reveal a situation of potential inversion (i. e. the second electron transfer is easier and occurs at a least negative potential) for the reductions of 1,2‐ and 1,4‐dinitrobenzene contrarily to the reduction of dinitrobenzene in a classical organic solvent. This is ascribed to H‐Bond interactions in Ethaline that are different for a delocalized radical anion and the dianion in a molecule bearing two conjugated redox groups. Indeed, the inversion of potential is not observed for the 1,3‐dinitrobenzene reduction. Reduction potentials in Ethaline are less negative than those in organic solvent (acetonitrile, DMF), that falls in line with the H‐bonding stabilization of the electrogenerated charged species in Ethaline. The potential inversion is not observed in ethylene glycol (with 0.2 mol L−1 Et4N+ Cl−) that is one of the components of Ethaline suggesting that choline chloride plays a major role in the H‐bonding/ion‐pairing stabilization. Interestingly and despite these stabilizations, the charge transfer kinetics remain comparable with those measured in common organic solvents (ks around 0.13 cm s−1).

Improving Wheat Yield and Water-Use Efficiency by Optimizing Irrigations in Northern China

Achieving the goal of increasing both crop yield and water-use efficiency with a better irrigation regime is a major challenge in semi-arid areas. In this study, we presented a two-season field experiment (October 2018–June 2019 and October 2019–June 2020) that considered drought stresses, i.e., no irrigation (W0), irrigated in jointing (W1), both in jointing and flowering (W2) after re-greening, and wheat varieties (S086; J22). The results showed that a 45.5% excess of irrigation water input did not promote wheat yield (W1 vs. W2). S086 was beneficial for the usage of soil water consumption under a low amount of irrigation water in both seasons. In addition, irrigation positively affected the activities of superoxide dismutase and catalase in flag leaves (p < 0.05). A decrease in irrigation helped to increase the concentrations of soluble sugar and proline and decrease the amount of malondialdehyde content for S086. For the water- and irrigation-water-use efficiency, W1 was significantly increased by 20.6–21.7% and 38.3–39.3% in 2018–2019 and 23.4–24.4% and 43.8–44.7% in 2019–2020, respectively, as compared to W2. Additionally, a higher yield for S086 than J22 was found under deficit irrigation. Consequently, our study suggested that the S086 variety combined with a total amount of irrigation water of 165 mm might be recommended to meet the win–win goal of high crop yields and water-use efficiency for reducing ground water depletion in the future.

Phase volumes of ultra high performance concrete containing nanoscale pozzolan

Grid nanoindentation and quantitative X-ray diffraction are employed to provide quantitative information on phase constituents of nanoscale pozzolan-containing ultra-high-performance concrete (UHPC). Three UHPC samples containing nanoscale pozzolan and cured with and without microwave energy are investigated. The volume fraction of each phase constituent is independently evaluated using both techniques: nanoindentation (NI) and quantitative X-ray diffraction (QXRD). For the NI, the volumes have been evaluated by taking into account the thresholds characterising the phase constituents. The NI could assess phase mixtures or composites rather than single phases. The microwave-cured samples (CMW and CPMW) contain in total more hydration products that the sample that was not cured with microwave energy (C000). In all three samples, a nanocomposite (C–S–H/CHnm) consisting of high-density (HD) calcium silicate hydrate (C–S–H) and nanoscale portlandite (CH) is included, and its amount is more than double for the pressure-compacted and microwave-cured sample (CPMW). The heat curing by microwave energy together with the very low amount of water and restriction of the available space for hydration products, favour the formation of the nanocomposite (C–S–H/CHnm) in the CPMW sample.

Cellulose Textiles from Hemp Biomass: Opportunities and Challenges

Worldwide demand for man-made cellulosic fibres (MMCF) are increasing as availability of cotton fibre declines due to climate change. Feedstock for MMCF include virgin wood, agricultural residues (e.g., straw), and pre- and post-consumer cellulosic materials high in alpha-cellulose content. Lyocell MMCF (L-MMCF) offer large advantages over other MMCF processes in terms of both environmental and social impacts: the solvent for cellulosic dissolution, n-methyl-morpholine-n-oxide, can be recycled, and the process utilizes non-toxic chemicals and low amounts of water. Hemp can be a preferential cellulosic feedstock for L-MMCF as hemp cultivation results in carbon dioxide sequestration, and it requires less water, fertilizers, pesticides, and herbicides than other L-MMCF feedstock crops. These factors contribute to hemp being an environmentally conscious crop. The increased legalization of industrial hemp cultivation, as well as recent lifts on cannabis restrictions worldwide, allows accessibility to local sources of cellulose for the L-MMCF process. In addition, hemp biomass can offer a much larger feedstock for L-MMCF production per annum than other cellulosic sources, such as eucalyptus trees and bamboo. This paper offers perspectives on the agricultural, manufacturing, and economic opportunities and challenges of utilizing hemp biomass for the manufacturing of L-MMCF.

Water Stress Effects on the Morphological, Physiological Characteristics of Maize (Zea mays L.), and on Environmental Cost

Water stress is one of the most important yield constraints on crop productivity for many crops, and especially for maize, worldwide. In addition, climate change creates new challenges for crop adaptation as water stress appears even in areas where, until recently, there was an adequate water supply. The objective of the present study was to determine the effect of water availability on the morphological and physiological characteristics of maize, and also on the environmental cost under field conditions. The lowest water treatment (ET50) reduced leaf area index, plant height, chlorophyll content, assimilation rate and gas exchange parameters, photosynthetic efficiency, and silage yield. Furthermore, mild water stress (ΕΤ70) affected the characteristics that were studied but maintained a high crop yield. Moreover, the outputs/inputs ratio and energy efficiency showed similar trends, with the highest values under ΕΤ100 treatment and the lowest under ΕΤ50 treatment in two consecutive years. Therefore, the results of this study can be used by farmers in the Mediterranean area, who can maintain or improve their crop yield using a lower amount of water when the water supply is limited, thereby contributing to reducing the impact of global climate change and maintaining crop productivity.

Arbuscular mycorrhizal fungi reduce potassium, cadmium and ammonium losses but increases nitrate loss under high intensity leaching events

BackgroundNutrients and heavy metals can be lost from soils via leaching, and arbuscular mycorrhizal fungi (AMF) can influence these events. Soil column experiments were carried out to examine whether leaching intensity and AMF can alter nutrient and Cd uptake in white clover plants and the extent of their losses through leaching.ResultsThe presence of AMF significantly increased shoot and total biomass, as well as increased N, P, Cu and Zn uptake independent of water amount applied; while root P and Cu uptakes were promoted by AMF at any water amount treatments. Higher water amounts led to reductions in total N, K and Zn uptake for AMF-colonized plants in comparison to moderate water amount treatments. In the absence of AMF, white clover at low water amount treatment exhibited maximal root Cd uptake. At high water amount treatments, the presence of AMF significantly decreased leachate volumes and the amount of leached NH4+, K and Cd while AMF significantly increased the amounts of leached NO3−.ConclusionsOverall we found that AMF-colonized white clover plants reduced NH4+, K and Cd loss from soils but increased the risk of NO3− loss under high intensity leaching conditions.

Molecular Mechanism Underpinning Stable Mechanical Performance and Enhanced Conductivity of Air-Aged Ionic Conductive Elastomers

Ionic conductive elastomers (ICEs), thanks to their liquid-free nature, have emerged as one of the most promising candidates for conductors in soft ionotronics. Notably, most ionotronic devices need to work in ambient environments where the presence of water molecules is ubiquitous. Thus far, the long-term impact of ambient water on the performances of ICEs remains virtually unexplored. Here, we show that air-aged ICEs absorb a very low amount of environmental water (∼0.3–0.6 wt % of the ICEs), which endows ICEs with stable mechanical performance and strongly boosted conductivity. We study the underlying molecular mechanism and clarify that the scission of lithium bonds between lithium ions and elastomer chains provoked by diffusing water molecules accounts for the observed changes in ICE properties. This work provides guidance for the practical mass application of ICE-based soft ionotronics in ambient environments.

Structural and photocatalytic properties of sol–gel-derived TiO2 samples prepared by conventional and hydrothermal methods using a low amount of water

Structural and photocatalytic properties of sol–gel-derived TiO2 samples prepared by conventional and hydrothermal methods using a low amount of water

Towards circular economy in the agrifood sector: Water footprint assessment of food loss in the Italian fruit and vegetable supply chains

In recent years, the agrifood sector has been relevantly impacted by resource shortage, food loss and waste across the whole supply chain. This study assesses, from a life cycle perspective, the water footprint of the fruit and vegetable losses occurring within the Italian agrifood supply chain, analyzing the potential linkages between circular economy policies and water management.The study methodology consists of three consequential steps: the definition of system boundaries, the data collection from databases and reports, and the processing of said data. Based on data availability of food losses, the following food items were chosen for the analysis, representing about 60% of the Italian fruits and vegetables domestic supply: tomatoes and onions for the macro-group of vegetables; orange, lemons, apples and grapes for the macro-group of fruits.Assessing the water footprint for the six categories of products, this study found out that, although less than other products, the amount of grapes lost along the supply chain determines a very high percentage of water loss. The tomato supply chain has proved to be the most sustainable in terms of water loss, due to the low amount of water needed to cultivate tomatoes. The analysis of the Italian trade market of fruits and vegetables has shown that water losses are mainly due to imports from France and Spain, in line with the high trade volumes. Finally, a weakness of the Italian fruit and vegetable supply chain was observed in the transport phase, because in this phase large quantities of food loss are associated with large volumes of water loss.Far from being the only tool to be used in the decision-making processes, the assessment of water loss embodied in the food loss, can be useful for managing the supply chain processes of perishable foods, ensuring process yield improvements, food quality traceability and environmental impact mitigation.

Nitrogen Agronomic Efficiency and Estimated Losses in Potato with Enhanced-Efficiency Fertilizers

ABSTRACT The objectives were to i) assess the effect of enhanced-efficiency nitrogen (N) fertilizers (EENF) [maleic itaconic acid copolymer (NSN) or 3,4-dimethylpyrazole phosphate (DMPP)] and urea on potato (Solanum tuberosum L.) tuber yield, N agronomic efficiency (NAE), N recovery efficiency in tuber (NREtuber) and plant (NREplant), N physiological efficiency, residual inorganic N in soil at harvest (Nresidual) and N losses (Nlosses) and ii) determine the impact of the amount of drainage water on NAE and Nlosses. On-farm experiments were conducted in seven sites with two fertilizers (EENF and urea) and two N rates (0 and 100 kg N ha−1). A N mass balance was used to calculate Nlosses. At two sites (one with NSN and one with DMPP), tuber yield response to N was greater with EENF than urea (avg. 5.0 Mg ha−1). NAE, NREtuber and NREplant were 17%, 31% and 25% higher with EENF than urea, respectively. These efficiencies decreased as drainage water increased. The estimated Nlosses were 12% lower with EENF, being the reduction particularly relevant with increasing drainage water. Therefore, using EENF in combination with irrigation management that ensures low drainage water amounts is essential for maximizing the fertilizer use efficiency and minimizing Nlosses in potato production systems.

Physico-mechanical properties enhancement of pineapple leaf fiber (PALF) reinforced epoxy resin-based composites using guar gum (polysaccharide) filler: effects of gamma radiation

Pineapple leaf fiber (PALF) reinforced epoxy resin-based composites were fabricated by using hand lay-up technique. The fiber content in the composites was taken as 25% (w/w), then it was modified by inserting 5% guar gum (polysaccharide) filler. Results demonstrated a 6% and 9% increase of tensile strength (TS) and tensile modulus (TM), respectively, over that of virgin PALF-epoxy composites. But 7% reduced elongation at break (Eb%) was noticed in this study. Results also revealed a 6% increase of bending properties due to insertion of guar gum filler. The virgin PALF-epoxy composites and along with guar gum filler PALF-epoxy composites were treated by gamma radiation doses varied from 2.5 to 10 kGy. The results revealed improved tensile and bending properties at 5 and 7.5 kGy, respectively. Sheared composite samples were immersed into deionized water and it was observed that both composites with and without filler absorbed a lower amount of water. The fiber-matrix adhesion was obtained by scanning electron microscopy (SEM) on both composites. The functional groups of the composites were also determined by Fourier transform infrared spectroscopy (FT-IR) and evaluated in this study.

Forest Fires, Land Use Changes and Their Impact on Hydrological Balance in Temperate Forests of Central Mexico

Temperate forests play a fundamental role in the provision, regulation, and support of hydrological environmental services, but they are subject to constant changes in land use (clearing, overgrazing, deforestation, and forest fires) that upset the hydrological balance. Through scenarios simulated with the Water Evaluation and Planning (WEAP) hydrological model, the present study analyzes the effects of forest fires and land use changes on the hydrological balance in the microwatersheds of central Mexico. The land use changes that took place between 1995 and 2021 were estimated, and projections based on the current scenario were made. Two trend scenarios were proposed for 2047: one with a positive trend (forest permanence) and the other with a negative trend (loss of cover from forest fires). The results show that with permanence or an increase in forest area, the surface runoff would decrease by 48.2%, increasing the base flow by 37% and the soil moisture by 2.3%. If forest is lost, surface runoff would increase up to 454%, and soil moisture would decrease by 27%. If the current forest decline trends continue, then there will be negative alterations in hydrological processes: a reduction in the interception of precipitation by the canopy and an increase in the velocity and flow of surface runoff, among others. The final result will be a lower amount of water being infiltrated into the soil and stored in the subsoil. The provision of hydrological environmental services depends on the maintenance of forest cover.

Water use efficiency of poplars grown for biomass production in the Midwestern United States

AbstractWater availability and other site conditions influence poplar biomass productivity and affect clonal performance due to genotype × environment interactions. It is important to select genotypes with high water use efficiency (WUE) that maximizes yield with available amounts of water at sites, while avoiding drought stress and growth impacts to the trees. During drought, stomatal closure induces increased accumulation of δ13C carbon isotope in tree tissues, which is strongly correlated with WUE of trees and usually expressed through carbon isotope discrimination (Δ). Our primary objectives were to evaluate differences in WUE among poplar genotypes grown in the Midwestern United States, and to identify genotypes with high WUE for future deployment on water‐limited sites in the region. Sites included 10‐year‐old biomass plantations in Escanaba, Michigan; Waseca, Minnesota; and Ames, Iowa established from 2000 to 2001 with seven poplar genotypes’ three genomic groups. Following harvest, height, diameter, and biomass were determined. Wood samples were collected from individual growth rings to assess annual ring width and WUE through δ13C and Δ. Aboveground dry biomass varied among sites (p = .0007), clones (p < .0001), and their interactions (p = .0134), ranging from 3.1 to 14.0 Mg ha−1 year−1. Δ varied among sites (Δ = 18.9–19.7‰; p < .0001) and clones (Δ = 18.6–19.9‰; p < .0001), indicating effects of site conditions on WUE of tested genotypes. Clones varied in their water‐conserving strategies. Some clones were characterized as water consumers with high growth and high WUE (“C916000”; “C916400”), while other genotypes were water conservers using lower amounts of water with moderate biomass production (“NC13624”; “NC13649”; “NM2” to a certain extent). Although δ13C carbon isotope accumulation correlates with WUE, Δ should only be used for selection when it is integrated with other parameters such as productivity, soils information, and climate data.

The Kultuma Au–Cu–Fe-Skarn Deposit (Eastern Transbaikalia): Magmatism, Zircon Geochemistry, Mineralogy, Age, Formation Conditions and Isotope Geochemical Data

The Kultuma deposit is among the largest and most representative Au–Cu–Fe–skarn deposits situated in Eastern Transbaikalia. However, its genetic classification is still a controversial issue. The deposit is confined to the similarly named massif of the Shakhtama complex, which is composed mainly of quartz monzodiorite-porphyry and second-phase monzodiorite-porphyry. The magmatic rocks are characterized by a low Fe2O3/FeO ratio, low magnetic susceptibility and belong to meta-aluminous, magnesian high-potassic calc-alkalic reduced granitoids of type I. The results of 40Ar-39Ar and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating showed that the formation of magmatic rocks proceeded during the Late Jurassic time: 161.5–156.8 Ma. Relatively low Ce/Ce*, Eu/Eu* and Dy/Yb ratios in the zircons indicate that the studied magmatic rocks were formed under relatively reduced conditions and initially contained a rather low amount of magmatic water. A mineralogical–geochemical investigation allowed us to outline five main stages (prograde skarn, retrograde skarn, potassic alteration, propylitic (hydrosilicate) alteration and late low-temperature alteration) of mineral formation, each of them being characterized by a definite paragenetic mineral association. The major iron, gold and copper ores were formed at the stage of retrograde skarn and potassic alteration, while the formation of polymetallic ores proceeded at the stage of propylitic alteration. The obtained timing of the formation of retrograde skarn (156.3 Ma) and magmatic rocks of the Shakhtama complex, along with the direct geological observations, suggest their spatial–temporal and genetic relationship. The data obtained on the age of magmatic rocks and ore mineralization are interpreted as indicating the formation of the Kultuma deposit that proceeded at the final stages of collision. Results of the investigation of the isotope composition of S in sulfide minerals point to their substantial enrichment with the heavy sulfur isotope (δ34S from 6.6 to 16‰). The only exclusion with anomalous low δ34S values (from 1.4 to 3.7‰) is pyrrhotite from retrograde skarns of the Ochunogda region. These differences are, first of all, due to the composition of the host rocks. Results of the studies of C and O isotope composition allow us to conclude that one of the main sources of carbon was the host rocks of the Bystrinskaya formation, while the changes in the isotope composition of oxygen are mainly connected with decarbonization processes and the interactions of magmatic fluids, host rocks and meteoric waters. The fluids that are responsible for the formation of the mineral associations of retrograde skarns and the zones of potassic alteration at the Kultuma deposit were reduced, moderately hot (~360–440 °C) and high-pressure (estimated pressure is up to 2.4 kbar). The distinguishing features of the fluids in the zones of potassic alteration at the Ochunogda region are a lower concentration and lower estimated pressure values (~1.7 kbar). The propylitic alteration took place with the participation of reduced lower-temperature (~280–320 °C) and lower-pressure (1–1.2 kbar) fluids saturated with carbon dioxide, which were later on diluted with meteoric waters to become more water-rich and low-temperature (~245–260 °C). The studies showed that the main factors that affected the distribution and specificity of mineralization are magmatic, lithological and structural–tectonic ones. Results of the studies allow us to classify the Kultuma deposit as a Au–Cu–Fe–skarn deposit related to reduced intrusion.

Amorphous and crystalline CaCO3 phase transformation at high solid/liquid ratio – Insight to a novel binder system

The transformation reactions in aqueous calcium carbonate systems are relevant for biomineralization processes, functionalised materials design and recently for the potential development of inorganic binders. The so-called ‘calcium carbonate cements’ are obtained by mixing amorphous (ACC) and crystalline CaCO3 (herein the anhydrous minerals calcite, aragonite and vaterite) with low amounts of water. The mechanisms behind the setting and hardening of these binders are still not clear. In the present study, the dissolution and precipitation reactions in low water ACC systems with and without crystalline CaCO3 have been investigated by in-situ techniques, Raman spectroscopy and optical pH measurements, coupled with reaction time resolved mineralogical and chemical analyses of solid and liquid samples. The results clearly indicate the presence of initial crystalline CaCO3 polymorphs to control the reactions kinetics and the resulting individual microstructure. Vaterite, with a considerably higher surface area than calcite and aragonite, produces more bonded and connected material. In the ACC-vaterite system the transformation of vaterite to calcite takes places in two dissolution-precipitation stages, accompanied by typical pH in- and decreases. Time-resolved analyses and hydrochemical modelling clearly reveal the solid transformation behaviour to be governed by the presence/absence of Mg2+ in the solution and the impurities, such as Na+, liberated from the educts to the reactive solution. The control and adjustment of the identified influencing parameters could allow for promising future development of CaCO3-based binders.