Temperature Reduction Research Articles

Dewatering Spent Ion-Exchange Resins with Supercritical CO2

ABSTRACT A process for dewatering spent ion exchange resins (gel and porous) used in nuclear power plants by supercritical CO2 (sCO2) is described. The amount of water removed by sCO2 is much higher than that expected from solubility considerations alone. Water from gel-type resins is both dissolved by and emulsified in sCO2. Emulsification also occurs in the absence of solids when water alone is contacted by sCO2. It is not a factor for microporous resins where an additional mechanism, viscous fingering, is involved. It appears that bulk water is emulsifiable but not if it is held in pores. Dewatering via viscous fingering has been previously invoked for matrices such as wood and sludge. The resins can be dewatered and dried with sequential batches of sCO2 at sub-boiling temperatures. The CO2 can then be potentially reused after expansion and separation from the entrained water. Partial decompression of the water-laden sCO2 would lead to cooling, which would drop the water solubility substantially. A reduction of temperature from 90 oC to 65oC reduces the solubility of water in sCO2 by a factor of five. The condensed water could then be separated with a hydrocyclone. The footprint of sCO2 is much smaller than the conventional drying process. The energy costs are also much lower because evaporation of water is avoided.

Contrast between Brazil and other countries in nutraceutical components of Camelina sativa grains

Camelina sativa, also known as false flax, is a species can be cultivated in a variety of climates, seasons and soil types, due to its short development cycle and tolerance to drought and low temperatures. In the composition of its grains, it presents a high amount of oil and rich in unsaturated fatty acids. In view of this, the objective of this work was to compare the composition of the nutraceutical components of Camelina sativa L. grains cultivated in Brazil and countries in Europe, Asia and North America. About 20 kg of grains were collected and then a homogeneous sample of 1kg of grains was cleaned to perform the centesimal composition of the grains. Afterwards, a search for information was carried out on the cultivation of Camelina sativa L. in other countries and the collection of information on the centesimal composition of the grains of this oleaginous plant. The collection of information was based on obtaining published scientific articles on the nutraceutical composition of Camelina sativa in regions of Europe, Asia and North America. Brazil presents a promising environment for the cultivation of Camelina sativa, with superior performance for the content of stearic acid, linoleic acid, linolenic acid and palmitic acid. The fatty acids profile decreased with the reduction of the minimum air temperature. The mineral material, palmitic acid and linolenic acid are positively correlated.

Multi-Strategical Thermal Management Approach for Lithium-Ion Batteries: Combining Forced Convection, Mist Cooling, Air Flow Improvisers and Additives

Maintaining the peak temperature of a battery within limits is a mandate for the safer operation of electric vehicles. In two-wheeler electric vehicles, the options available for the battery thermal management system are minuscule due to the restrictions imposed by factors like weight, cost, availability, performance, and load. In this study, a multi-strategical cooling approach of forced convection and mist cooling over a single-cell 21,700 lithium-ion battery working under the condition of 4C is proposed. The chosen levels for air velocities (10, 15, 20 and 25 m/s) imitate real-world riding conditions, and for mist cooling implementation, injection pressure with three levels (3, 7 and 14 bar) is considered. The ANSYS fluent simulation is carried out using the volume of fluid in the discrete phase modelling transition using water mist as a working fluid. Initial breakup is considered for more accurate calculations. The battery’s state of health (SOH) is determined using PYTHON by adopting the Newton–Raphson estimation. The maximum temperature reduction potential by employing an airflow improviser (AFI) and additives (Tween 80, 1-heptanol, APG0810, Tween 20 and FS3100) is also explored. The simulation results revealed that an additional reduction of about 11% was possible by incorporating additives and AFI in the multi-strategical approach. The corresponding SOH improvement was about 2%. When the electric two-wheeler operated under 4C, the optimal condition (Max. SOH and Min. peak cell temp.) was achieved at an air velocity of 25 m/s, injection pressure of 7 bar with AFI and 3% (by wt.) Tween 80 and a 0.1% deformer.

Investigating the Impact of Various Vegetation Scenarios on Outdoor Thermal Comfort in Low-Density Residential Areas of Hot Arid Regions

In hot, arid regions, outdoor spaces suffer from intense heat. This study explores how vegetation can improve outdoor thermal performance for pedestrians in low-density residential areas. Specifically, it seeks to identify the best combination of grass and trees for optimal comfort. Four scenarios were simulated using ENVI-met software, varying the proportions of grass and three tree types: 50% grass, 50% grass with 25% trees, 50% grass with 50% trees, and 50% grass with 75% trees. A reference scenario with no vegetation was also investigated. The simulated outputs encompassed air temperature (Ta), mean radiant temperature (Tmrt), relative humidity (RH), and physiologically equivalent temperature (PET). The findings show that scenarios with a higher percentage of trees exhibited the best reduction in air temperature, ranging from 0.2 k to 0.92 k. Additionally, the inclusion of trees and grass in the scenarios resulted in a substantial improvement in thermal performance, with an average reduction of 7.5 degrees in PET. Among the evaluated scenarios, the one comprising 75% trees and 50% grass exhibits the most noteworthy enhancement. This study underscores the significance of strategically positioning vegetation to coincide with prevailing wind patterns, thereby enhancing convective cooling mechanisms and improving overall thermal comfort levels. These insights offer valuable implications for urban planning and the development of sustainable design strategies.

Multivariate Bayesian Optimization of CoO Nanoparticles for CO2 Hydrogenation Catalysis.

The hydrogenation of CO2 holds promise for transforming the production of renewable fuels and chemicals. However, the challenge lies in developing robust and selective catalysts for this process. Transition metal oxide catalysts, particularly cobalt oxide, have shown potential for CO2 hydrogenation, with performance heavily reliant on crystal phase and morphology. Achieving precise control over these catalyst attributes through colloidal nanoparticle synthesis could pave the way for catalyst and process advancement. Yet, navigating the complexities of colloidal nanoparticle syntheses, governed by numerous input variables, poses a significant challenge in systematically controlling resultant catalyst features. We present a multivariate Bayesian optimization, coupled with a data-driven classifier, to map the synthetic design space for colloidal CoO nanoparticles and simultaneously optimize them for multiple catalytically relevant features within a target crystalline phase. The optimized experimental conditions yielded small, phase-pure rock salt CoO nanoparticles of uniform size and shape. These optimized nanoparticles were then supported on SiO2 and assessed for thermocatalytic CO2 hydrogenation against larger, polydisperse CoO nanoparticles on SiO2 and a conventionally prepared catalyst. The optimized CoO/SiO2 catalyst consistently exhibited higher activity and CH4 selectivity (ca. 98%) across various pretreatment reduction temperatures as compared to the other catalysts. This remarkable performance was attributed to particle stability and consistent H* surface coverage, even after undergoing the highest temperature reduction, achieving a more stable catalytic species that resists sintering and carbon occlusion.

Enhancement in thermo-hydraulic performance of ceramic-based disk heat sink with fractal micro-channels via double layering, hybrid nanofluids, and cross-sectional convergence

The focus of this paper is to further improve the thermo-hydraulic performance of a disk heat sink with fractal-like microchannels by introducing four distinct modifications: incorporating convergent cross-sections in microchannels, implementing double layering, utilizing a high-conductivity material (AlN ceramic) for the heat sink, and integrating hybrid nanofluids. Hybrid nanofluids, encompassing Aluminum Oxide-Graphene, Aluminum Oxide-Copper, and Copper-Graphene, each with varying volume fractions and an overall volume fraction of 2 % and 4 %, were systematically evaluated. The cumulative impact of these modifications on the four levels fractal-like microchannel heat sink's thermo-hydraulic performance was rigorously assessed through numerical simulations. The flow rate ranges from 300 to 600 ml/min, corresponding to an inlet Reynolds number in the range of 3014 to 6018.The findings reveal that the increase around 10 % in Nusselt number can be achieved through implementing converging cross-sections at levels 3 and 4. Substituting silicon with AlN ceramic leads to a reduction in maximum temperature from 1.85 to 2.58 ℃, depending on the flow rate. Under a heat flux of 40 W/cm2, double layering can reduce thermal resistance by 0.2. Most effective configuration involves a double-layered fractal microchannel with convergent cross-sections at levels 3 and 4, employing AlN ceramic as the material, and utilizing a hybrid water-based nanofluid with a volume fraction of Cu 3 %-Al2O3 1 %. This configuration achieves a notable reduction in maximum temperature by 11.1 °C and 17.97 °C under heat fluxes of 40 and 80 W/cm2, respectively, at a volumetric flow rate of 300 ml/min.

Assessing the impact of heat mitigation measures on thermal performance and energy demand at the community level: A pathway toward designing net-zero energy communities

AbstractIn the context of escalating global energy demands, urban areas, specifically the building sector, contribute to the largest energy consumption, with urban overheating exacerbating this issue. Utilizing urban modelling for heat-mitigation and reduction of energy demand is crucial steps towards a sustainable built-environment, complementing onsite energy generation in the design and development of Net-zero Energy (NZE) Settlement, especially in the context of Australian weather conditions. Addressing a significant gap in existing literature, this study offers empirical analysis on the climate and energy efficacy of integrated heat mitigation strategies applied in 14 neighbourhood typologies located in Sydney, Australia. Examining the application of cool materials on roads, pavements, and rooftops, alongside urban vegetation enhancement, the analysis demonstrates scenario effectiveness on heat mitigation that leads to reduce ambient temperature and energy demands along with CO2 emissions within the neighbourhoods. Considering building arrangement, built-area ratio, building height, and locations, ENVI-met and CitySim are utilized to assess the heat-mitigation and the energy demand of neighbourhoods, respectively. Results indicate that mitigation measures can lead up to a 2.71 °C reduction in ambient temperature and over 25% reduction in Cooling Degree Hours, with a 34.34% reduction in cooling energy demand and overall energy savings of up to 12.49%. In addition, the annual energy-saving yields a CO2 reduction of approximately 141.12 tonnes, where additional vegetation further amplifies these reductions by enhancing CO2 absorption. This study showcases the pathway towards achieving NZE goals in climates similar to that of Australia, highlighting significant benefits in heat-mitigation, environmental impact, and energy-savings.

Molecular‐Engineered Wool for Sustainable All‐Weather Radiative Cooling Textiles

AbstractPersonal thermal regulation through passive radiative cooling is an effective strategy to achieve sustainable development. Although recent advances have introduced various cooling textile designs, the extensive use of materials unsuitable for common textiles, alongside coating or compositing technologies, not only compromises the wearability and safety of these textiles but also impacts green sustainability. Herein, it is shown that wool is a promising natural material for transferring mid‐infrared human body radiation, but the high absorption in the solar spectrum prohibits wool from achieving satisfactory daytime radiative cooling. Thus the natural wool impregnates zinc ions into the protein chains to form a zinc‐ion woolen (wool‐Zn) fabric. The wool‐Zn fabric can provide humans with a cooling sensation both indoors and daytime outdoors, showing a temperature reduction of 2 °C on human skin indoors and a reduction of 7 °C on artificial skin under direct sunlight, respectively, when covered by wool‐Zn fabrics compared to when covered with cotton. Moreover, the wool‐Zn fabric shows desirable antibacterial properties and durability against washing and abrasion, while maintaining desirable wearability. As a result, the wool‐Zn fabric shows great potential for commercial application in personal thermoregulation and provides an effective avenue toward sustainable energy and environment.

Optimizing control for strike point sweeping using lower divertor coil in EAST

In 2021, EAST was equipped with a full-ring divertor coil to facilitate research on the fish tail divertor concept. Initially, it was observed that the coil current had a negligible ability to sweep the strike point. Conversely, when the amplitude and frequency of the alternating current were marginally increased, there was a significant interruption to plasma control. This perturbation was attributed to the poloidal control field’s limited response rate to the coil’s fluctuations. To address this issue, novel control methodologies were devised to ensure stable and effective sweeping of the strike point using the divertor coil. The devised methods are twofold: For high-frequency strike point control, a low-pass filter decoupling technique based on ISOFLUX control strategy enabled achieving a sweeping frequency of 100 Hz. This strategy allowed for consistent plasma management without compromising average stored energy or density regulation. Resulting from this proficient manipulation of the strike point, a reduction in the peak temperature of the divertor plate was observed. For low-frequency sweeping, a static multi-input multi-output decoupling approach was developed, facilitating concurrent sweeping of both the outer and inner strike points.

Effect of the arrangement of the injectors on the flow quantities in water injection into the hot supersonic crossflow inside the cylinder

In this study, the effect of different arrangements of injectors on the injection of liquid water into the hot supersonic crossflow of cylindrical geometry on the performance and the rate of evaporation has been studied using a numerical method. The crossflow has a Mach of about 2 and a total temperature of 800[Formula: see text]K. At first, the penetration height and droplets produced by atomization in the supersonic flow are validated using the Lagrangian technique, and the results have been compared with the experiments. The usage of heat transfer equations and the evaporation model for the spray evaporation of droplets in the hot flow is also performed in the validation process, and the results are compared with the experimental results. Then, the injection into the examined geometry with four, six and eight injectors in three different arrangements was evaluated. The results indicate that employing an arrangement of eight injectors leads to the most significant reduction in total temperature, with average total temperatures decreasing to below 550[Formula: see text]K. The results demonstrate a 40% decrease in total pressure, with a decrease in Mach number to about 1 at the end of the cylinder. Additionally, the evaporation rate shows higher evaporation of water in the eight-injector arrangement compared to other arrangements.

Heat Dissipation Capability of Stagger-Stacked Double Data Rate Module

Heat Dissipation Capability of Stagger-Stacked Double Data Rate Module

Investigation of performance and emission characteristics using ethanol-blended gasoline fuel as a flex-fuel in two-wheeler vehicle mounted on a chassis dynamometer

Abstract This study investigated the performance and emissions of flex fuels in a 110-cc BS6-compliant fuel-injected two-wheeler without ethanol adaptation adjustments. The tests were carried out under controlled conditions on a chassis dynamometer at 1000, 2000 and 3000 r.p.m. using ethanol blends from 10% ethanol (E10) to 85% ethanol (E85). Parameters examined included brake power (BP) output, brake-specific fuel consumption (BSFC), peak in-cylinder pressure and exhaust temperature. Emissions, including carbon monoxide (CO), hydrocarbons (HC), nitrogen oxide (NOx) and unregulated emissions, were also assessed. As the percentages of the ethanol blend increased from E10 to E85, there was a noticeable improvement in power output. At 1000 r.p.m., the BP ranged from 2.4 to 4.6 kW for different blends. The BSFC and the peak in-cylinder pressure followed a similar pattern, indicating enhanced performance and fuel efficiency with higher ethanol concentrations. Interestingly, using E85 at 1000 r.p.m. resulted in a significant 41.08% reduction in exhaust temperature compared with E10, although this difference decreased with higher blend percentages. Furthermore, replacing E10 with E85 at 1000 r.p.m. reduced CO and HC emissions by 9.17% and 38.34%, respectively. In contrast, NOx emissions increased at all r.p.m. levels with higher-ethanol blends, peaking at a 415 parts per million increase at 3000 r.p.m. However, unregulated emissions decreased significantly with increased r.p.m. and ethanol content. In summary, the use of flex-fuel blends in a two-wheeler resulted in a modest increase in BP output, improved fuel efficiency and lower CO and HC emissions. These findings are vital for optimizing ethanol blend utilization in two-wheeler engines under low-load conditions, considering both performance and environmental aspects.

Investigating of epoxy nanocomposites structure and properties that contain both pristine and aminosilane-treated silicon carbide (SiC) particles

This article presents a methodology for functionalization of silicon carbide (SiC) through chemical modification using γ-aminopropyltriethoxysilane (APTES) and its subsequent dispersion in an epoxy composition. The research revealed that functionalizing SiC particles with γ-aminopropyltriethoxysilane (SiC(APTES)) enhanced their chemical compatibility with the epoxy composition, facilitating the dispersion of SiC particles. Furthermore, it was observed that the functionalization of the filler had a profound impact on the structure, curing kinetics, and physical and mechanical properties of epoxy nanocomposites. The addition of SiC(APTES) into the epoxy composition resulted in a significant reinforcement of the material. Specifically, the flexural stress and flexural modulus of elasticity increased by 179% and 74%, respectively, while the impact strength experienced a remarkable improvement of 462%. Additionally, the tensile strength and tensile modulus of elasticity increased by 83% and 70%, respectively, compared to the epoxy composite without SiC. The application of SiC(APTES) also played a crucial role in initiating the polymerization process through the involvement of reactive amino groups, leading to a reduction in the initial curing temperature and an amplification of the thermal effects of the polymerization reaction. Moreover, the presence of functionalized SiC significantly influenced the structure of the epoxy composite, thereby contributing to its enhanced strength. In summary, the inclusion of SiC in the epoxy composition not only bolstered the material but also improved its thermal stability.

Mild-Temperature Supercritical Water Confined in Hydrophobic Metal-Organic Frameworks.

Fluids under extreme confinement show characteristics significantly different from those of their bulk counterpart. This work focuses on water confined within the complex cavities of highly hydrophobic metal-organic frameworks (MOFs) at high pressures. A combination of high-pressure intrusion-extrusion experiments with molecular dynamic simulations and synchrotron data reveals that supercritical transition for MOF-confined water takes place at a much lower temperature than in bulk water, ∼250 K below the reference values. This large shifting of the critical temperature (Tc) is attributed to the very large density of confined water vapor in the peculiar geometry and chemistry of the cavities of Cu2tebpz (tebpz = 3,3',5,5'-tetraethyl-4,4'-bipyrazolate) hydrophobic MOF. This is the first time the shift of Tc is investigated for water confined within highly hydrophobic nanoporous materials, which explains why such a large reduction of the critical temperature was never reported before, neither experimentally nor computationally.

The influence of using MWCNT/ZnO-Water hybrid nanofluid on the thermal and electrical performance of a Photovoltaic/Thermal system

Rising photovoltaic panel temperatures significantly compromise their performance and lifespan, leading to lower power output and conversion efficiency. Consequently, research on PV panel cooling strategies has gained momentum to address these challenges. This study presents an experimental investigation of a photovoltaic/thermal system's performance using a cooling fluid – a multi-walled carbon nanotube/zinc oxide nanofluid. A comparative analysis is conducted on three PV panels: uncooled, water-cooled, and nanofluid-cooled. Notably, our experiment employed a low mass flow rate (0.156 kg/min), significantly lower than typical values reported in prior literature, and a 0.1 wt% nanofluid concentration. Our primary objective was to evaluate the efficacy of MWCNT/ZnO nanofluid in enhancing the thermal management and overall efficiency of a PVT system. This study focused on the impact of nanofluid on electrical efficiency, thermal efficiency, and exergy performance of the system. The results demonstrate significant improvements. The key findings of this investigation reveal that MWCNT/ZnO nanofluid effectively improves the base fluid's thermal properties, leading to substantial enhancements in both electrical and thermal efficiencies of the PVT system. Compared to the uncooled panel, the nanofluid achieved a maximum temperature reduction of 14.9 °C on the panel surface, a 16.8 % increase in average electrical efficiency, and a maximum thermal efficiency of 51.3 % compared to 45.5 % for water cooling. Moreover, the average overall efficiency of the system with nanofluid cooling reached 58.7 %. Furthermore, the implementation of MWCNT/ZnO nanofluid cooling resulted in a significant boost in maximum overall exergy efficiency, surpassing water cooling and conventional systems by 7 % and 27 %, respectively. Additionally, a 3.5 % reduction in entropy generation and exergy destruction was observed compared to the conventional system.

Effect of Ti content on abnormal grain growth of Fe-Mn-Al-Ni-Ti shape memory alloy

Abstract In this paper, the effects of Ti content on the solvus temperature of γ-phase and abnormal grain growth (AGG) in Fe43.5-xMn34Al15Ni7.5Tix (x = 0, 0.5, 1 and 1.5) shape memory alloys (SMAs) were investigated. It is found that, the increase of Ti content leads to a significant reduction of the solvus temperature of γ-phase, a significant refinement of γ-phase, and a decrease of subgrain size. After 3 times cyclic heat treatments (CHTs), the average grain size of Fe42Mn34Al15Ni7.5Ti1.5 SMA reaches about 9.0 mm, which is about twice of that for Fe42.5Mn34Al15Ni7.5Ti1 SMA. This is attributed to the small subgrains can provide a higher subgrain boundary energy (ΔGs) and grain boundary (GB) migration rate. The subgrain size of Fe42Mn34Al15Ni7.5Ti1.5 SMA (9.7 μm) is significantly smaller than that of Fe42.5Mn34Al15Ni7.5Ti1 SMA (21.3 μm). Thereby, the ΔGs (15.3×10-2 J mol-1) and GB migration rate (11.3×10-6 m s-1) of Fe42Mn34Al15Ni7.5Ti1.5 SMA are significantly higher than those of Fe42.5Mn34Al15Ni7.5Ti1 SMA (7.1×10-2 J mol-1, 6.3×10-6 m s-1). In addition, the maximum superelastic strains of Fe42Mn34Al15Ni7.5Ti1.5 and Fe42.5Mn34Al15Ni7.5Ti1 were 5.3% and 5.1%, respectively. In summary, the addition of 1.5 at.% Ti in Fe-Mn-Al-Ni-Ti SMA can promote the AGG without sacrificing the superelasticity.

Comparing Small Water Bodies’ Impact on Subtropical Campus Outdoor Temperature: Measured vs. Simulated Data

This study investigates the impact of small water bodies on outdoor temperatures in their vicinity, using a campus located in the subtropical region of Taichung City, Taiwan, as the research subject. By employing on-site measurements and Computational Fluid Dynamics (CFD) simulations, we examined their temporal and spatial influence, as well as comparisons between actual measurements and software predictions. Key findings include the following: (1) Small water bodies exhibit discernible temperature-regulating effects on their surrounding areas. While the influence diminishes with distance, this attenuation is not stark, and is potentially constrained by the water body’s patch size. (2) Regulatory effects vary between day and night. In summer, temperature reductions of up to 3.5 °C (simulated) and 3.2 °C (measured) were observed. Conversely, in winter, daytime temperatures around water bodies may rise by up to 3.9 °C. (3) Discrepancies between CFD simulations and actual measurements, influenced by fluctuations in Global Horizontal Irradiation (GHI), range from +2.5 °C to −1.8 °C. During high GHI periods, measured values surpass simulations, whereas during low or zero GHI conditions, simulations exceed measurements. Moreover, high regression analysis R2 values validate the feasibility of CFD simulations for predicting water body-induced temperature changes. Insights from this study offer valuable guidance for urban planners and policymakers seeking sustainable urban climate management strategies.

Effect of cobalt on CeO2 nanorod supported Pt catalyst: Structure, performance, kinetics and reaction mechanism in CO oxidation

Catalytic oxidation represents a highly efficient and extensively employed approach for the elimination of CO in exhaust gas. Rationally designing and preparing catalysts with exceptional activity and stability in the presence of H2O and SO2 at low temperatures represent crucial avenues for future advancements. In this work, a series of Pt catalysts supported on CeO2 nanorods incorporated with varying amounts of Cobalt (Co/CeO2 ratio ranging from 0 to10) were prepared and evaluated for their catalytic activity in CO oxidation under both dry and wet conditions. The ultrahigh dispersion of Pt, outstanding redox properties, and abundant oxygen vacancies on the surface of Co-doped CeO2 nanorod supported Pt catalysts were revealed by XRD, HAADF-STEM, Raman spectroscopy and H2-TPR techniques. The catalytic activity for CO oxidation strongly depends on the Co content and reaction conditions. Among them, Pt/Co-CeO2-5 % exhibits the highest CO oxidation performance with a T90 (the temperature to achieve 90 % conversion of CO) of 170 °C under dry conditions, which is significantly lower by 140 °C compared to T90 of Pt/CeO2. Pt/Co-CeO2-1 % demonstrates superior CO oxidation performance with a T90 of 195 °C under wet conditions, exhibiting a reduction in temperature by 65 °C compared to the T90 of Pt/CeO2. Moreover, Pt/Co-CeO2 exhibits excellent resistance to SO2 compared to Pt/CeO2. Kinetic studies, in situ DRIFT analysis and isotopic experiments demonstrated direct participation of H2O in the reaction. On the catalysts with a low Co/Ce ratio (Co/Ce < 0.03), CO readily reacts with hydroxyl groups dissociated from H2O to form carboxyl intermediates, which subsequently undergo rapid decomposition into CO2, resulting in an enhanced reaction rate of CO oxidation at low temperature.

Remote sensing of hazards: The spatio-temporal evolution of land surface temperature over tailings flows and related drivers

Since mining activities began in Brazil some 300 years ago, disasters related to tailings dams have been recorded. In 2019, the B1 dam located at Vale, S.A.'s Córrego do Feijão mine in the municipality of Brumadinho (state of Minas Gerais) collapsed, releasing a vast amount of iron ore tailings into the Ferro-Carvão stream, which spread to the Paraopeba River located 10 km downstream. This tragedy devastated around 294 hectares of the Ribeirão Ferro-Carvão watershed, including mining infrastructure, farmland and housing, and is among the biggest environmental disasters ever recorded in Brazil. The torrent of mud and debris and the substances released by the collapse, namely metals (e.g. iron, manganese), in addition to completely flooding the bed and banks of the Ribeirão Ferro-Carvão and remaining on them for several years as a thick blanket, caused significant changes in land surface temperature (LST). The aim of this study was to spatially analyze the LST in the period before and after the dam burst (2018 - 2021), and to find its relationship with the granulometric and chemical parameters of the deposited materials, as well as with the changes in land use and land cover that occurred with and after the dam burst. Landsat 8 satellite images processed on the Google Earth Engine platform were used to estimate the LST. The results showed a relationship between this parameter and the characteristics of the tailings, with lower temperatures being associated with sectors of the impacted area covered with fine fractions (presumably with greater heat dissipation capacity). A reduction in temperature was also detected over the period analyzed, which was related to the tailings removal and revegetation works in the impacted area. The integrated results indicate that LST is an effective parameter for characterizing disasters involving tailings dams, as well as for monitoring natural recovery or recovery as a result of mitigation measures implemented in the impacted areas. We therefore recommend its use in remote sensing of mining activities in general and tailings dam disasters in particular.

Ore-forming fluid characteristics and ages of the Xinan Cu-Mo deposit at Zijinshan orefield, SE China: New insights for metallogenic mechanism and exploration

The Xinan deposit, a newly discovered porphyry Cu-Mo deposit in the Zijinshan orefield, Fujian Province, exhibits distinct alteration and porphyry mineralization stages, including the potassic, propylitic, and phyllic alteration stages. The phyllic stage is further divided into molybdenite, chalcopyrite, and pyrite sub-stages. Molybdenite Re-Os model age (108.1 ± 1.1 Ma) and concomitant sericite 40Ar/39Ar plateau age (109.0 ± 6.0 Ma) indicate that the Xinan Cu-Mo deposit was formed at 109 ∼ 108 Ma. Four types of fluid inclusions have been identified at the Xinan deposit, including vapor-rich, liquid-rich, and opaque daughter mineral-bearing subtypes with minor transparent daughter mineral-bearing subtypes. Fluid inclusion microthermometry measurements reveal that the potassic alteration stage exhibits homogenization temperatures of 375–475 °C and salinities range of 4–20 wt% NaCl eqv., suggesting minor slight fluid boiling. Chlorite geothermometer suggests temperatures of the propylitic alteration stage range from 261 to 336 °C, averaging at 303 °C. The molybdenite, chalcopyrite, and pyrite sub-stages have homogenization temperatures of 325–400 °C, 325–350 °C, and 300–350 °C, respectively, with corresponding salinities of 2–10 wt% NaCl eqv., 4–8 wt% NaCl eqv., and 2–4 wt% NaCl eqv.. The Laser Raman spectroscopy results show that the fluid inclusions in the Xinan deposit consist of H2O with minor CO2, hematite, chalcopyrite, and halite. The evolution of the ore-forming fluids in the Xinan porphyry Cu-Mo deposit is characterized by a transition from high-temperature, low- to moderate-salinity, oxidized, and CO2-bearing conditions during the potassic alteration stage, to moderate- to high-temperature and low-salinity conditions during the propylitic alteration stage. The subsequent phyllic alteration stage, which overprints on the potassic and partial propylitic alteration stages, is marked by moderate- to high-temperature, low-salinity, and low-oxygen fugacity environments. The primary mechanisms driving mineralization in the Xinan porphyry Cu-Mo deposit are thus identified as the reduction in temperature and oxygen fugacity, coupled with CO2 escape. In contrast to the Luoboling-Jintonghu porphyry Cu-Mo deposit, the ore-forming fluid of the Xinan deposit is characterized by lower temperatures, salinity, and CO2 contents, and reduced fluid boiling. This suggests a relatively subdued porphyry-type mineralization. The lack of a distinct potassic alteration zone in the Xinan Cu-Mo deposit suggests the potential existence of a deeper, higher temperature and salinity porphyry mineralization center beneath this deposit.