Freezing Temperature Research Articles

A novel simultaneous abatement of bromate and diphenyl phosphate using the freezing process

The purification of bromate (BrO3-)-contaminated water has become a challenge because of its persistence and adverse effects. Furthermore, there has been concern over the release of byproducts, such as diphenyl phosphate (DPHP), from flame retardants in wastewater treatment plant (WWTP). In this study, we designed the water treatment system for the oxidation of DPHP accompanied by bromate (BrO3-) reduction via freezing the solution. A sample containing 10 μM DPHP, 100 μM Br-, and 50 μM BrO3-, with a pH of 3 was frozen at -20oC, approximately 25 μM BrO3- was reduced, and DPHP was fully eliminated after a 0.5 h reaction time. Conversely, these reactions did not advance in water at 20oC. This increase in the rate of chemical reaction in ice is the consequence of the freeze concentration effect, which refers to the extraction of dissolved chemical species into the liquid-like regions of the polycrystalline ice micro-structure during the freezing of the solution. The redox reactions among DPHP, Br-, and BrO3- become thermodynamically favorable due to the distinctive environment in the liquid brine in ice. The efficiency of the DPHP oxidation significantly increased with an increase in BrO3- concentration, and vice versa. The Br-/BrO3--induced HOBr production is proposed as a primary oxidant for DPHP degradation. The proton activity (pH) has a significant influence on the reaction efficiency. The low freezing temperature accelerated the reaction kinetics of DPHP degradation and BrO3- reduction. The results of this study indicate the possibility of utilizing ice chemistry for the BrO3- reduction that concomitantly removes DPHP for water treatment. This environmentally friendly water treatment method can be considered to implement in regions with a cold climate.

The sensitivity of sea-ice brine fraction to the freezing temperature and orientation

Abstract The changing conditions in which sea ice forms and exists are likely to affect the properties of sea ice itself, and potential climate feedbacks need to be identified and understood to improve future projections. Here we perform a set of idealised laboratory experiments that model sea-ice growth under a range of freezing conditions. The results confirm existing theories; sea-ice growth rate is largest for cooler freezing temperatures, fresher ambient salinities and cases with bottom cooling. Our primary metric of interest is the brine fraction (the volume ratio of brine inclusions to the total sea ice), which we quantify and determine its sensitivity with respect to the ambient salinity, freezing temperature and, for the first time, the freezing direction. We find that the brine fraction of our model sea ice is most sensitive to freezing temperature, and increases 2.5% per 1 $^\circ$ C increase of freezing temperature.

Enhanced functionalities of isovalently substituted 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) relaxor piezoceramics synthesized via air quenching

The isovalently substituted lead-free binary solid solution, 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) (BF-BT) (x ≤ 0.07), has been synthesized by solid state ceramic method via air quenching sintering. FTIR and XRD along with Rietveld structure refinement confirmed a pure perovskite phase with a pseudocubic structure (space group Pm3‾m) for developed compositions. SEM revealed a dense microstructure with fine grain size (<1.5 μm) and minimal porosity. XPS analysis reveals predominantly Bi+3 and Fe+3 states, along with oxygen vacancies (VO··). Ferroelectric studies demonstrated a maximum remanent polarization (Pr) of 12.3 μC/cm2 and coercive field EC of 30.95 kV/cm for La3+ concentration of x = 0.03. Overall decrement in Pr can be attributed to dipolar defect-induced random fields reducing the activation barrier for domain nucleation. Leakage current measurement reveals improved resistivity (∼108 Ω cm) up to an applied field of 30 kV/cm. Dielectric measurements unveiled two frequency-dependent anomalies in temperature dependence above room temperature, indicative of diffuse phase transitions. The Vogel-Fulcher model depicted an increasing freezing temperature (from 465 K for x = 0.01–551 K for x = 0.07) and decreasing activation energy (from ∼0.61 eV to 0.07 eV) with increasing La3+ concentration. The estimated diffuseness parameter around ∼2 suggested relaxor behavior. Doping with La resulted in increased dielectric permittivity at 10 kHz (from 4100 to 24066), showcasing the efficacy of site engineering in augmenting the functional properties of BF-BT for high-temperature dielectric and transducer applications.

Nucleation of multi-species crystals: methane cleatrate hydrates, a playground for classical force models

Nucleation and growth of methane clathrate hydrates is an exceptional playground to study crystallisation of multi-component, host-guest crystallites when one of the species forming the crystal, the guest, has a higher concentration in the solid than in the liquid phase. This adds problems related to the transport of the low concentration species, here methane. A key aspect in the modelling of clathrates is the water model employed in the simulation. In previous articles, we compared an all-atom force model, TIP4P/Ewald, with a coarse grain one, which is highly appreciated for its computational efficiency. Here, we perform a complementary analysis considering three all-atoms water models: TIP4P/Ewald, TIP4P/ice and TIP5P. A key difference between these models is that the former predicts a much lower freezing temperature. Intuitively, one expects that to lower freezing temperatures of water correspond to lower water/methane–methane gas–clathrate coexistence ones, which determines the degree of supercooling and the degree of supersaturation. Hence, in the simulation conditions, 250 K (500 atm, and fixed methane molar fraction), one expects computational samples made of TIP4P-ice and TIP5P, with a similar freezing temperature ( T f ∼ 273 K), to be more supersaturated with respect to the case of TIP4P-Ew ( T f ∼ 245 K), and crystallisation to be faster. Surprisingly, we find that while the nucleation rate is consistent with this prediction, growth rate with TIP4P-ice and TIP5P is much slower than with TIP4P-Ew. The latter was attributed to the slower reorientation of water molecules in strong supercooled conditions, resulting in a lower growth rate. This suggests that the freezing temperature is not a suitable parameter to evaluate the adequacy of a water model.

On the Effects of Physical Climate Risks on the Chinese Energy Sector

We examine the impact of physical climate risks on energy markets in China, distinguishing between traditional energy and new energy stock markets, and the energy commodity market, utilizing a time-varying parameter vector autoregressive model with stochastic volatility (TVP-SV-VAR). Specifically, we investigate the dynamic effects of five specific subtypes of physical climate risks, namely waterlogging by rain, drought, typhoon, cryogenic freezing, and high temperature, on WTI oil prices and coal prices. The findings reveal that these physical climate risks exhibit time-varying similar effects on the returns of traditional energy and new energy stocks, but heterogeneous effects on the returns of WTI oil prices and coal prices. Finally, we categorize and examine the impact of both acute and chronic physical risks on the energy commodity market.

Knowledge, attitudes, and practices towards poultry handling and Salmonella risk among households in Beirut, Lebanon

Food-Borne Disease (FBD) is defined as an illness resulting from consuming foods contaminated with bacteria, their toxins, viruses, or parasites. Food poisoning due to improper food handling is a major global public health problem. In Lebanon, numerous challenges affect safe food consumption, with poultry being a common vehicle for many pathogens, such as Salmonella spp. This bacterium can cause serious illnesses, including gastroenteritis, characterized by abdominal pain, vomiting, diarrhea, and fever. This study aimed to examine the Knowledge, Attitudes, and Practices (KAPs) towards poultry handling among households in Beirut, Lebanon, and identify factors influencing KAP levels. A cross-sectional study was conducted through face-to-face interviews with 125 households in different areas of Beirut. The interview was divided into four main parts: sociodemographic characteristics, knowledge, attitudes, and practices. The results showed that consumers’ knowledge and practices were inadequate, though their attitude was positive. Participants aged 43-55 had higher odds of having a good knowledge level than those aged 18-29 (OR = 3.889, p = 0.02). Additionally, those with a college education were 7.442 times more likely to have a positive attitude towards food safety compared to those with no formal education (p = 0.005). Most participants (91.2%) do not regularly check their refrigerator and freezer temperatures. Furthermore, significant associations (p < 0.001) existed between the different KAP levels. This study aimed to raise public awareness regarding the handling of chicken to minimize food-borne illnesses by evaluating food handlers’ knowledge and behaviors. Insights from this study can used in campaigns to raise awareness about Salmonella and transmission risks among households. Moreover, findings may guide policymakers to create regulations for safe handling of poultry.

Ion migration at the ice–water interface during the freezing process of salt solution – Experimental investigation

Within the scope of this work, systematic investigations of the ion migration process at the ice–water interface during the freezing of salt solutions are performed via experimental investigations (part I) and numerical investigations (part II). In this study, the ion migration trend under different freezing temperatures was revealed, and the formation process of the brine pockets during phase transition and the mechanism of ion release in ice were explored. The results show that the migration capabilities of Na+ and K+ are greater than those of Ca2+ and Mg2+, whereas the migration capability of Cl− is greater than those of HCO3− and SO42−. At −2 °C, the ion concentration in the surface ice decreased by 47.64 %, indicating the occurrence of ion release within the ice. When the moving speed of the phase transition interface is greater than the ion diffusion ability, the brine pockets form in the ice. Under a temperature gradient, the brine pockets in ice become thermodynamically unstable, resulting in the inevitable ion release toward the high-temperature side. The ion release depends on the temperature gradient and the brine pocket concentration. Furthermore, the unsynchronous migration of ions is related to the freezing temperature, diffusion coefficient, hydration radius, and hydration free energy.

Effect of different freezing temperatures on the physical, technological, and organoleptic properties of aged semimembranosus muscles from farmed fallow deer (Dama dama)

Although venison could play an important role in human nutrition, this meat remains undervalued and still contributes very little to the formal meat industry. Moreover, information on processing methods of fallow deer meat and overall quality is still very limited. The objective of this study was to determine how physical, technological, and organoleptic properties differ between 14-day-aged vacuum-packaged fallow deer meat stored either chilled or frozen at different temperatures (-10°C, -18°C, -40°C and -80°C) for six months. Physical, technological, and organoleptic analyses were conducted on semimembranosus muscles (SM) obtained from farmed fallow deer bucks (n = 10). Freezing significantly increased meat redness, yellowness, chroma values, cooking loss and tenderness compared to fresh meat but did not affect pH values, lightness, thawing, or grilling loss. Mean pH readings were 5.5–5.6, being highest in the samples measured one day after slaughter. Freezing at -80°C had the most pronounced effect on some sensory attributes, namely, the highest game meat aroma intensity, sour odour, sour flavour and the lowest chewiness. The findings indicate that a freezing temperature of -18°C and subsequent slow thawing might be preferential in terms of maintaining fallow deer meat quality.

Thermoluminescence and Apollo 17 ANGSA Lunar Samples: NASA's Fifty‐Year Experiment and Prospecting for Cold Traps

AbstractBy placing Apollo 17 regolith samples in a freezer, and storing an equivalent set at room temperature, NASA effectively performed a 50‐year experiment in the kinetics of natural thermoluminescence (TL) of the lunar regolith. We have performed a detailed analysis of the TL characteristics of four regolith samples: a sunlit sample near the landing site (70180), a sample 3 m deep near the landing site (70001), a sample partially shaded by a boulder (72320), and a sample completely shaded by a boulder (76240). We find evidence for a total of eight discrete TL peaks, five apparent in curves for samples in the natural state and seven in samples irradiated in the laboratory at room temperature. For each peak, we suggest values for peak temperatures and the kinetic parameters E (activation energy, i.e. “trap depth,” eV) and s (Arrhenius factor, s−1). The lowest natural TL peak in the continuously shaded sample 76240 dropped in intensity by 60 ± 10% (1976 vs. present room temperature samples) and 43 ± 8% (freezer vs. room temperature samples) over the 50‐year storage period, while sunlit and partially shaded samples (70001, 70180, 72321, 72320) showed no change. These results are consistent with the E and s parameters we determined. The large number of peaks, and the appearance of additional peaks after irradiation at room temperature, and literature data, suggest that glow curve peaks are present in lunar regolith at ∼100 K and their intensity can be used to determine temperature and storage time. Thus, a TL instrument on the Moon could be used to prospect for micro‐cold traps capable of the storage of water and other volatiles.

Long-lived superhydrophobic micro/nano-locked fiber membranes for long-lasting oil-water separation effectiveness

Superhydrophobic/superoleophilic oil-water separation membranes have great potential for treating industrial, domestic, and marine oily wastewater. However, the robustness of these membranes remains a challenge that restricts their ability to maintain long-lasting oil-water separation effectiveness. Inspired by the adhesion mechanisms of snail and tree frog, exploiting the synergistic effects of interfacial hydrogen bonding and mechanical interlocking, we herein achieved strong adhesion between hydrophobicized in-situ nanoparticles and textile fibers to fabricate a long-lived superhydrophobic micro/nano-locked fiber membrane (LSMFM). LSMFM maintains excellent superhydrophobicity even when exposed to mechanical and chemical damage, such as continuous sandpaper abrasion, tape-peeling, weight impact, water jet, and acid/alkali/salt erosion. Additionally, LSMFM efficiently separates various light/heavy oil-water mixtures, achieving a remarkable separation flux of >10,000 L·m−2·h−1 and an efficiency >98 %, even after 200 cycles with n-hexane. Importantly, such membranes still maintain a high separation flux >19,000 L·m−2·h−1 and efficiency >97 % after sequentially being subjected to acids, alkalis, freezing, and high temperatures, and even the adsorption bag formed by wrapping LSMFM with superhydrophilic wood pulp cotton can adsorb oil at fixed-point and continuously recover pure oil from oily wastewater. This study paves a new way for the sustainable purification of oily wastewater in extreme environments.

Assessment of lyophilized microencapsulated multi strain probiotic for improved shelf life and stability

A Multi species Probiotics (MSP) of calf gut origin was encapsulated either with chitosan (ECMSP) or without chitosan (EMSP). Further, the probiotic was encapsulated and lyophilized (ELMSP) using three types of cryoprotectant solutions sucrose (ELMSP(S)), skim milk (ELMSP(SM)) and sucrose + skim milk combination (ELMSP (SSM)). The encapsulation yield was good and ranged from 75 % to 80 % for MSP products. These MSP products were stored at refrigeration temperature (4 °C), deep freeze and room temperature for 12 weeks. The shelf life (mean CFU) of encapsulated microcapsules was significantly better (P < 0.001) at the refrigeration temperature (9.44 Log10 CFU/g) than deep freeze (7.42 Log10 CFU/g) and room temperature (6.67 Log10 CFU/g). At the end of the 12 weeks storage period, EMSP maintained 25.1 %, 49.6 % and 32.6 % viable counts at room temperature, refrigeration and deep freeze condition respectively. For the lyophilized-encapsulated MSP, the mean probiotic counts of ELMSP(S) and ELMSP (SSM) were significantly (P < 0.001) higher (9.62 Log10 CFU/g) than those of ELMSP(SM) ((9.36 Log10 CFU/g) at room temperature. At refrigeration temperature, the mean probiotic counts for ELMSP (SSM. (10.1 Log10 CFU/g)) were significantly higher (P < 0.001) than ELMSP(S, (9.97 Log10 CFU/g) and ELMSP(SM, (9.86 Log10 CFU/g). Further, a 12 weeks storage study for ELMSP (SSM) showed that the microcapsules stored at refrigeration temperature (4°C) showed only 6.4 % drop in viability which was significantly lower (P < 0.001) than that of room temperature showing 15.3 % drop and deep freeze storage with 17.1 % drop in viability. It was appreciable that even at room temperature; there was only one log drop in the viability of MSP showing that it can be comfortably stored at room temperature for longer periods at field level.

Investigation of cold-resistance mechanisms in cryophylactic yeast Metschnikowia pulcherrima based on comparative transcriptome analysis.

Low temperature inhibits the growth of most microorganisms. However, some microbes can grow well in a low temperature, even a freezing temperature. In this study, the mechanisms conferring cold resistance in the cryophylactic yeast Metschnikowia (M.) pulcherrima MS612, an isolate of the epidermis of ice grapes, were investigated based on comparative transcriptome analysis. A total of 6018 genes and 374 differentially expressed genes (> 2-fold, p < 0.05) were identified using RNA-Seq. The differentially expressed genes were mainly involved in carbohydrate and energy metabolism, transport mechanisms, antifreeze protection, lipid synthesis, and signal transduction. M. pulcherrima MS612 maintained normal growth at low temperature (5°C) by enhancing energy metabolism, sterol synthesis, metal ion homeostasis, amino acid and MDR transport, while increased synthesis of glycerol and proline transport to improve its resistance to the freezing temperature (-5°C). Furthermore, cAMP-PKA and ERAD signaling pathways contribute to resist the low temperature and the freezing temperature, respectively. This study provides new insights into cold resistance in cryophylactic microorganisms for maneuvering various metabolism to resist different cold environment.

Sulfur isotopic fractionation during hydrolysis of carbonyl sulfide

Carbonyl Sulfide (OCS) is the most abundant sulfur-containing gas in the atmosphere, and it is used as a proxy for terrestrial gross primary productivity (GPP). Oceans are the major source of OCS to the atmosphere, produced by photochemical and “dark” reactions. Hydrolysis to H2S and CO2 is the major removal process of OCS from the ocean's surface. Measuring the sulfur isotope values (δ34S) and the isotopic fractionation (ε) associated with these major OCS sources and sinks could decrease the uncertainties in its fluxes. In the current study, we aim to determine the ε during the hydrolysis process of OCS (εh). We used a purge and trap system coupled to a GC/MC-ICPMS to measure δ34S values during hydrolysis under different temperatures (4–40 °C), salinities (0.2–40 g/L), and pH (4–9), representing various natural environmental conditions. In addition, we use the quantum chemical method to calculate the equilibrium εh and compare it to the empirical results. Our results for the low salinity (S =0.2 g/L; pH 8.0) water show a temperature dependency of the εh from −3.9 ‰ ± 0.2 ‰ (4 °C,) to −2.2 ± 0.6 ‰ (40 °C). The higher fractionation at low temperatures has implication for ice-core data interpretation. However, in natural seawater at 4°C and 22 °C (S = 40 g/L, pH 8.2) there was no such temperature dependency and the εh averaged −2.6 ± 0.3 ‰. Thus, it seems that salinity cancels the temperature effect close to the freezing temperature of water. Varying the pH between 4 and 9 (at 22 °C) did not result in any εh trend. Ab-initio calculations suggest that OCS hydrolysis is not controlled by equilibrium. The εh values we report will aid in quantifying the impact of OCS's hydrolysis on the observable sulfur isotopic signature of OCS in oceanic and in freshwater environments. This in turn will facilitate more accurate mass-balance calculations for the OCS budget from the ocean to the atmosphere.

Comparison of pulmonary vein isolation between two commercially available cryoballoon systems

BackgroundPulmonary vein isolation (PVI) using cryoballoon (CB) ablation has comparable efficacy and safety to the gold standard of radiofrequency ablation in the treatment of symptomatic atrial fibrillation (AF). Initial randomized control trials were performed using Arctic Front Advance Pro™ (AFr) (Medtronic, Dublin, Ireland) CB system. Novel CB systems have recently become available, including the POLARx™ (Px) (Boston Scientific, Marlborough, Massachusetts, USA) system. We aimed to compare PVI using the Px and the AFr CB systems in our patient population in terms of efficacy, safety and procedure characteristics in a routine clinical setting.MethodsWe performed a retrospective analysis of our internal AF ablation registry, containing 452 consecutive patients (pts) that underwent first procedure cryo-PVI for symptomatic AF. Primary endpoints were AF recurrence after 3 and 12 months, complication rate, procedure duration, fluoroscopy time and fluoroscopy dose. Secondary endpoints were minimal freeze temperature, time to isolation (TTI) and temperature at TTI for each of the pulmonary veins as well as minimal esophageal temperature during the procedure.ResultsThe primary efficacy endpoints of AF recurrence after 3 and 12 months were similar between the AFr and the Px systems (25.5% vs 21.3%, p = 0.416 and 22.2% vs 20.6%, p = 0.794, respectively). Complication rates were similar (3.9% vs 6.8%, p = 0.18) between groups and consisted mostly of mild vascular complications. The AFr group showed a significantly shorter procedural duration (68 (55–77) vs 73 (60–80) min, p = 0.002), and lower fluoroscopy dose compared to the Px system. Fluoroscopy times remained similar, however. Minimal freeze temperatures and temperatures at time of isolation were significantly lower in the Px group. However, the time to isolation and minimal procedural esophageal temperature were similar in both groups.ConclusionPVI using the AFr and the Px systems showed comparable safety and efficacy. Procedural times were longer for the Px system. The Px system showed lower freeze temperature measurements but seemed to have a comparable biological effect.

Synthesis and physical properties of Sm2PdGe3 in a context of RE2PdGe3 family

In this study, we present the crystallographic and magnetic characterization of a new intermetallic compound Sm2PdGe3, which was synthetized by a two stage method employing an eutectic alloy. The investigations carried out exhibited, that Sm2PdGe3 crystallize in AlB2-type structure with lattice parameters a = 4.2189(1) Å and c = 4.1031(2) Å. This compound can be classified as a cluster-glass with a spin freezing temperature Tf = 10.5 K. Furthermore, there were carried out the analysis of the role of the rare earth (RE) elements on the structural parameters of RE2PdGe3 and draw a correlation between the RE radius and the unit cell parameters. We show that a deviation from the ideal 1:3 Pd:Ge ratio is necessary to synthesize RE2PdGe3 with smaller RE elements.

Effect of freeze-thaw treatments with different conditions on frost fatigue in three diffuse-porous trees.

In addition to inducing xylem embolism, freeze-thaw events can cause frost fatigue phenomena. Freezing temperature, freezing times, number of freeze-thaw cycles and frost drought can affect the level of freeze-thaw-induced embolism, but it is unknown whether there is an effect on frost fatigue. We assessed whether these frost-related factors changed frost fatigue in the three diffuse-porous species by simulating freeze-thaw treatments under different conditions. We also proposed a new metric, embolism area, in place of embolism resistance, to more accurately quantify the shift of the vulnerability curve after experiencing freeze-thaw-induced embolism and refilling. Frost fatigue caused vulnerability curves of all species to change from S-shaped to double S-shaped or even R-shaped curves. When exposed to a freeze-thaw event, Acer truncatum showed strong resistance to frost fatigue; in contrast, Populus (I-101×84K) and Liriodendron chinense were more vulnerable. Changing freezing temperature and times did not impact the response to frost fatigue in the three species, but a greater number of freeze-thaw cycles and more severe frost drought significantly exacerbated their fatigue degree. Considering that frost fatigue may be a widespread phenomenon among temperate diffuse-porous species, more work is needed in the future to reveal the mechanisms of frost fatigue.

An approach to Molten Salt Reactor operation and control and its application to the ARAMIS actinide burner

Molten salt reactors (MSRs) are Generation IV nuclear reactor concepts gaining significant research interest worldwide. The present work proposes a methodology for the definition and optimization of the MSR operating conditions and control strategy. The proposed methodology employs a novel 0D steady-state model, the multi-physics system-scale MOSAICS (MOlten SAlt Incompressible Calculation System) model and a Global Sensitivity Analysis (GSA) method based on Hilbert-Schmidt Independence Criterion indices. The methodology was then applied to the ARAMIS (Advanced Reactor for Actinides Management in Salt) fast-spectrum chloride-salt burner reactor. Two alternative control strategies are proposed in order to achieve target margins to the salt freezing and structure material limit temperatures during normal operation, plus a 20 % power variation per minute load-following objective. The performance of the control strategies was assessed through comparison with the natural behavior during a load-increasing transient, as well as during Unprotected Transient Over-Power (UTOP) and Station Blackout (SBO) accidents. Controlled load variation transients are observed to reduce overall temperature variation rates throughout the salt circuits, while the inclusion of a variable fuel flow from the reactor commands can further limit these fluctuations. However, the selected operating conditions exhibited insufficient margins to freezing or the materials limit temperature under unprotected accident conditions. GSA enabled the derivation of correlations to characterize the dynamic response of MSRs to the accidents. Based on the observed reactor response to the various transients, potential modifications to the ARAMIS design and control strategies are proposed.

Properties of foam concrete containing phase change material impregnated pumice

Energy consumption rises as a result of numerous electrical devices used to maintain thermal comfort of interior building areas. Using building materials with low thermal conductivity and density as well as an effective thermal energy storage plan can help to mitigate this. In order to enhance thermal performance of building, phase change material (PCM) was incorporated to foam concrete mixture in this study. Capric acid (CA)-palmitic acid (PA) eutectic mixture was prepared and impregnated with pumice (50 % by weight), a light and porous material. DSC results indicated that pumice/CA-PA composite exhibited a melting temperature of 22.84˚C and a freezing temperature of 20.85˚C, with corresponding enthalpy values for melting and freezing determined to be 85.4 J/g and 85.1 J/g, respectively. TGA analyses demonstrated that operational temperature of pumice/CA-PA composite was significantly below its thermal degradation temperature (194˚C). The prepared pumice/CA-PA composites were replaced with silica aggregate at different rates and incorporated in foam concrete mixture. Porosity and water absorption values rose as pumice/PCM content increased, yet there was a 7.2–41.1 % drop in dry unit weight when compared to reference. Compressive strength also showed a linear decrease and the lowest compressive strength value was recorded as 4.71 MPa in the presence of 40 % pumice/PCM. Thermal conductivity dropped from 0.487 W/mK to 0.167 W/mK, suggesting that foam concrete samples that were produced are all suitable as insulation materials. In peak solar radiation hours, PCM-impregnated pumice foam concrete (PFC) provided about 11.8 % and 8.72 % surface and room center temperatures compared to that of the reference in maximum case. PFC with PCM provided 6.54 % warmer surface temperature in cold weather. PFC-PCM can provide a cooler indoor temperature during peak temperature hours. Therefore, it may have a great potential to decrease the cooling load of a building.

Experimental study on freezing temperature and its influencing factors of loess contaminated by heavy metals

This paper attempts to reveal the freezing temperature and its influencing factors of heavy metal-contaminated loess by adopting two cooling methods: fast and slow grading. As a result, Lanzhou loess was used as an experimental material to make polluted soil with varying heavy metal concentrations and initial water content. The pollutant elements included Zn, Ni, Cu, Cr, Cd, and Pb. The findings demonstrate that: 1) The slow cooling rate causes supercooling, jumping, and a progressive decrease in the temperature of the polluted soil. Different cooling methods have no obvious effect on freezing temperature. Furthermore, the freezing temperature of contaminated soil varies depending on its water content. The impact of increasing water content on freezing temperature is not evident; 2) The freezing temperature of loess decreases with the increase of heavy metal ion content. The freezing temperature of loess polluted by Zn, Ni and Cd ions decreased linearly with the increase of ion content. The influence of cations on the freezing temperature of loess is as follows: Zn2+> Ni2+> Cd2+> Cr3+> Pb2+> Cu2+. The influence order of anions is Cl− > SO42−; 3) The freezing temperature of loess containing heavy metal ions is about equal to the freezing temperature of the corresponding heavy metal solution plus the freezing temperature of loess itself. The freezing temperature of heavy metal-polluted loess follows the temperature superposition principle.

Microplastic Particles Contain Ice Nucleation Sites That Can Be Inhibited by Atmospheric Aging.

Recent research has shown that microplastics are widespread in the atmosphere. However, we know little about their ability to nucleate ice and their impact on ice formation in clouds. Ice nucleation by microplastics could also limit their long-range transport and global distribution. The present study explores the heterogeneous ice-nucleating ability of seven microplastic samples in immersion freezing mode. Two polypropylene samples and one polyethylene terephthalate sample froze heterogeneously with median freezing temperatures of -20.9, -23.2, and -21.9 °C, respectively. The number of ice nucleation sites per surface area, ns(T), ranged from 10-1 to 104 cm-2 in a temperature interval of -15 to -25 °C, which is comparable to that of volcanic ash and fungal spores. After exposure to ozone or a combination of UV light and ozone, simulating atmospheric aging, the ice nucleation activity decreased in some cases and remained unchanged in others. Our freezing data suggest that microplastics may promote ice formation in cloud droplets. In addition, based on a comparison of our freezing results and previous simulations using a global transport model, ice nucleation by microplastics will impact their long-range transport to faraway locations and global distribution.