Main Degradation Process Research Articles

Reactions of a Prototypical Phenolic Antioxidant with Radicals in Polyethylene: Insights from Density Functional Theory.

Phenolic antioxidants are widely used to prevent oxidation, which is the main degradation process for many polymers, in particular polyolefins among which polyethylene is the most employed one. Although it is generally understood that one of the main mechanisms by which phenolic antioxidants prevent or slow down oxidation is by deactivating radicals and preventing the formation of alkyl radicals, detailed understanding at the atomic scale of the hierarchy of radical reactions is still lacking. Here, we investigate the interaction of a prototypical phenolic antioxidant, butylated hydroxytoluene (BHT), with radicals in a polyethylene model by means of static and dynamic simulations based on density functional theory. We focus on the H-transfer reactions between BHT and radical species by evaluating the associated energy barriers and analyze the conditions in which these relevant reactions occur by first-principles molecular dynamics simulation. Our polyethylene model includes a realistic surface of a crystalline lamella, thus describing the local atomic environment in which the reactions mainly take place. Our results suggest that the H-transfer reaction of the BHT molecule with an alkoxy radical is spontaneous, and the energy barrier is small (∼0.1 eV) with a peroxy radical. Conversely, direct scavenging of alkyl radicals by BHT seems excluded. Our molecular dynamics simulations highlight the influence of steric hindrance and antioxidant diffusion within amorphous regions on antioxidant efficiency.

Combined kinetic analysis of thermal degradation characteristics and reaction mechanism of thin intumescent fire-retardant coating of steel structure

To determine the thermal kinetic triplets and elucidate the reaction mechanism of thin intumescent fire-retardant coatings (IFR) of steel structures, one efficient combined kinetic approach was implemented in this study. Thermogravimetric experiments were conducted in air atmosphere at four heating rates, and the whole IFR thermal degradation process was divided into two stages. The average activation energy values derived by model-free methods were 78.9 kJ/mol and 175.16 kJ/mol for Stage I (0<α < 0.2) and Stage II (0.2<α < 0.9), respectively. Furthermore, the linear Coats-Redfern (CR) and non-linear Masterplots models were applied to identify the possible reaction mechanism. It was found that the F3/2 mechanistic model was better suited to the main thermal degradation process. Then model reconstruction based on the F3/2 mechanism model was performed. The results showed that the reconstructed model had a strict linear relationship in the independence analysis and KCE analysis, along with a good agreement between the theoretical and experimental results. The current study provided new insights into the systematic thermal degradation mechanism of IFR, and the proposed kinetic model would be helpful for the thermal protection prediction for steel structure during fire.

Effect of different boundary conditions on the combustion properties and fire characteristics of typical woods

To provide guidance on the bioenergy potential of wood and its fire spread numerical simulation, insights into the combustion properties and fire characteristics of one hardwood (sassafras) and two softwoods (pine and fir) were investigated. The effect of different boundary conditions are focused. The condensed phase decomposition in thermogravimetric analysis indicated that the main degradation processes for all wood combustion could be divided into two stages, and the corresponding demarcation point of conversion rate is 0.4 and 0.35 for hardwood and softwood, respectively. Three specific regions could further be established based on the activation energies variations in Stage Ⅰ. The governing reaction mechanism of sassafras wood is determined to be the diffusion model connect with order-based model, while the reaction mechanism of softwoods (pine and fir) can be considered as the reaction order (1st to three-halves) type followed by diffusion model. The gas phase flaming in FPA combustion experiments suggest that fir and pine wood have a faster charring rate and produce less CO and CO2 during pyrolysis and combustion. Sassafras requires more time to be ignited owing to its high density, which causes higher thermal inertia therefore decelerating the temperature increase on the sample surface. In addition, the dense structure of sassafras leads to an early appearance of the second HRR and MLR peaks. As hardwood has a higher density than softwood, the thermal insulation in hardwood delays char cracking on sassafras wood surface and enhances the duration between ignition and flameout. Such findings should provide guidance for wood combustion modeling and flame spread simulation in future works.

Relationships between morphological facies and the evolutionary processes of petroplinthites in the Southern Espinhaço Range (SE-Brazil)

Morphological facies of petroplinthites describe how soil components such as the soil matrix, nodules, pores, and coatings relate to each other in space. French scientists have extensively used such descriptions to interpret evolutionary processes and stages of petroplinthites (laterites, ferruginous duricrusts, ironstones) in Central and Western Africa. However, there has been little progress using the interpretation of petroplinthite facies in other parts of the world. This study explores the protocol in Brazilian petroplinthites with the aim of defining processes and identifying evolutionary stages based on analysis of the morphological differences in the petroplinthites from a pedogenetic perspective. The studies were concentrated in the Southern Espinhaço Range, southeast Brazil, and covered Petric or Pisoplinthic Plinthosol (Petroferric Oxisols) profiles with a wide morphological variety of petroplinthites. Based on a literature review, the aim was to standardize concepts and define the different morphological facies, before applying them to the petroplinthites of the study area. Geochemical and mineralogical analyses were added to the description of the facies to interpret the main pedogenetic processes and evolutionary sequences among the profiles. As such, macro and micro morphological descriptions were carried out in association with geochemical maps using SEM-EDS, and specific mineralogical characterization was performed using an electronic microprobe to characterize the main morphological facies. XRD, XRF, and magnetic susceptibility analyses were used to interpret the main formation, transformation, and degradation processes of the petroplinthites. The integration of these analyses enabled the association of the morphological facies with the petroplinthite evolutionary processes. Thus, while lamellar facies are shown to be directly associated with saprolitization processes, nodular and massive facies generally represent intense lateritization. Protopisolithic facies are commonly associated with transformation processes, with goethite precipitation and re-cementation of the matrix, while pisolithic facies are formed through degradation processes with intense mineral dissolution. Recovering the protocol for associating macro and micro morphological facies with geochemistry and mineralogy enabled improved interpretation of the genesis of petroplinthites, with clearer and more objective identification of the evolutionary stages, as well as their relationship with the landscape and the hydrological systems and environmental conditions.

Role of Salt Concentration in Stabilizing Charged Ni-Rich Cathode Interfaces in Li-Ion Batteries.

The cathode-electrolyte interphase (CEI) in Li-ion batteries plays a key role in suppressing undesired side reactions while facilitating Li-ion transport. Ni-rich layered cathode materials offer improved energy densities, but their high interfacial reactivities can negatively impact the cycle life and rate performance. Here we investigate the role of electrolyte salt concentration, specifically LiPF6 (0.5-5 m), in altering the interfacial reactivity of charged LiN0.8Mn0.1Co0.1O2 (NMC811) cathodes in standard carbonate-based electrolytes (EC/EMC vol %/vol % 3:7). Extended potential holds of NMC811/Li4Ti5O12 (LTO) cells reveal that the parasitic electrolyte oxidation currents observed are strongly dependent on the electrolyte salt concentration. X-ray photoelectron and absorption spectroscopy (XPS/XAS) reveal that a thicker LixPOyFz-/LiF-rich CEI is formed in the higher concentration electrolytes. This suppresses reactions with solvent molecules resulting in a thinner, or less-dense, reduced surface layer (RSL) with lower charge transfer resistance and lower oxidation currents at high potentials. The thicker CEI also limits access of acidic species to the RSL suppressing transition-metal dissolution into the electrolyte, as confirmed by nuclear magnetic resonance (NMR) spectroscopy and inductively coupled plasma optical emission spectroscopy (ICP-OES). This provides insight into the main degradation processes occurring at Ni-rich cathode interfaces in contact with carbonate-based electrolytes and how electrolyte formulation can help to mitigate these.

Composition dependence of X-ray stability and degradation mechanisms at lead halide perovskite single crystal surfaces.

The multiple applications of lead halide perovskite materials and the extensive use of X-ray based techniques to characterize them highlight a need to understand their stability under X-ray irradiation. Here, we present a study where the X-ray stability of five different lead halide perovskite compositions (MAPbI3, MAPbCl3, MAPbBr3, FAPbBr3, CsPbBr3) was investigated using photoelectron spectroscopy. To exclude effects of thin film formation on the observed degradation behaviors, we studied clean surfaces of single crystals. Different X-ray resistance and degradation mechanisms were observed depending on the crystal composition. Overall, perovskites based on the MA+ cation were found to be less stable than those based on FA+ or Cs+. Metallic lead formed most easily in the chloride perovskite, followed by bromide, and only very little metallic lead formation was observed for MAPbI3. MAPbI3 showed one main degradation process, which was the radiolysis of MAI. Multiple simultaneous degradation processes were identified for the bromide compositions. These processes include ion migration towards the perovskite surface and the formation of volatile and solid products in addition to metallic lead. Lastly, CsBr formed as a solid degradation product on the surface of CsPbBr3.

Regeneration Strategies for Ruthenium-Poisoned ORR Catalysts in Reformate PEM Fuel Cells

Reformate polymer electrolyte membrane (PEM) fuel cells have great potential to transform the global maritime transportation in a more environmentally friendly and CO2-neutral manner. Platinum (Pt)-ruthenium (Ru) alloy nanoparticles (NPs) supported on carbon (PtRu/C) are the most commonly used electrocatalyst material to accelerate the hydrogen oxidation reaction (HOR) of the reformate gas (H2/CO2/CO) at the anode [1]. The high CO tolerance of PtRu/C catalysts is based on the ensemble effect [2]. However, these materials suffer extremely from the Ru dissolution and Ruz+ crossover to the cathode, which are the main degradation processes in reformate PEM fuel cells. At the cathode, the Ruz+ species immediately redeposit on the Pt/C catalyst, resulting in a drastic decay of the entire performance of the reformate PEM fuel cell. Even if the Ru coverage on the Pt/C catalyst is less than 20 at. %, there is an 8-fold decrease in kinetics of the oxygen reduction reaction (ORR) [3]. Therefore, it is necessary to develop a regeneration protocols to mitigate the Ru poisoning at the cathode.In this study, we developed and tested different regeneration protocols to recover the Ru-poisoned ORR catalysts using a rotating disc electrode (RDE) set-up. To simulate the worst situation for poisoned ORR catalysts, commercially available Pt-Ru alloy NPs supported on carbon were used and characterized by TEM, XRD, XAS, and XPS. In general, our regeneration protocols can be classified into dynamic and steady-state conditions. All protocols included a pre-activation step by holding the potential at 1.4 VRHE for 5 minutes in 0.1 M HClO4. During the dynamic regeneration process, the potential was switched between 1.4 VRHE and 1.6 VRHE with a duration time of 10 s by 10 times using a pulse voltammetry technique. In contrast, the steady-state regeneration protocol consisted of only one pulse at 1.6 VRHE for 100 s. For the recovery procedure of the poisoned ORR catalysts, the experimental parameters were correlated with the changes in ORR performance and electrochemically active surface area (ECSA) via CO stripping as well as the loss of Ru content and particle structure established from μ-XRF, ICP-OES, and TEM.After the dynamic regeneration process, the ORR mass activity (MA) and specific activity (SA) of PtRu2/Vulcan increase initially from 0.07 ± 0.01 to 0.21 ± 0.02 A mgPt+Ru -1 and 62 ± 9 to 190 ± 16 μA cmPt+Ru -2 at 0.85 VRHE, iR-free, respectively. Hence, the dynamic regeneration protocol leads to an improvement of the MA by a factor of 2 and of the SA by 2.1 for PtRu2/Vulcan. In comparison, the steady-state regeneration experiment shows an enhancement by 2.2 (0.26 ± 0.03 A mgPt+Ru -1) for MA and by 3.5 (276 ± 16 μA cmPt+Ru -2) for SA, respectively. Therefore, the steady-state regeneration process is more effective compared to the dynamic regeneration protocol. Based on the µ-XRF data, we observed that the Ru content of the PtRu2/Vulcan decreases from 62 ± 2 at. % to either 5 ± 1 at. % or 8 ± 1 at. % after the steady-state or dynamic regeneration process. The loss of Ru from the particle surface can also be monitored by CO stripping, where the CO oxidation peak is shifted positively from 0.58 VRHE to 0.67 VRHE and 0.63 VRHE after steady-state and dynamic regeneration protocol, respectively. As the particle size of the PtRu2 NPs is around ~ 5.3 ± 1.2 nm, the ECSA is mainly unchanged after both regeneration protocols.Based on our results, the steady-state regeneration process with 1.6 VRHE for 100 s is more effective than the dynamic one with pulses from 1.4 to 1.6 VRHE each with 10 s by 10 times to recover the ORR activity of the PtRu2 alloy NPs. The proposed regeneration protocols can improve the performance and life-time of the reformate PEM fuel cell.

Soil Erosion and Landslide Susceptibility Mapping in Western Attica, Greece: A Rock Engineering System Approach

Two of the eight main soil degradation processes with which soils worldwide are confronted are soil erosion and landslides. Specifically, landslides are a major threat in particular areas across Europe, often leading to serious impacts on population, property, and infrastructure. Regarding the abovementioned processes, the case study of the fatal Mandra flash flood (November 2017) in the Attica Region (Greece), which caused 24 deaths, and much infrastructure and building damage, is presented with the intention of assessing the relationship between soil erosion and landslide incidents. Investigations were executed from 2018 to 2022, and their outcomes were taken into consideration by the Technical Authority of the Attica Region. Soil erosion lines were delineated in a GIS and were validated using a previously generated regional Web-GIS landslide susceptibility map. The study presents soil erosion types from the Mandra fatal flash flood event and correlates them with already existing landslide susceptibility analyses for the Attica Region. The produced susceptibility map is a cartographic product on a regional scale (1:100,000) generated via a semiquantitative heuristic methodology named the Rock Engineering System (RES). The way in which both soil erodibility and landslide susceptibility maps were generated and validated could be the basis for proposing modeling approaches that can respond to new developments in European landslide policies.

Non-Linear Evaluation of Coatings Performance: Evaluation of Polyester/Melamine Coil Coating Hydrolysis in NSS Test

Coating is one of the most common and effective ways to protect metallic elements from corrosion. The evaluation of a coating’s performance is related to its quality and durability. Neutral salt spray (NSS) is a common accelerated test used for coatings. Commercial polyester/melamine coil coatings applied on aluminum specimens were exposed to NSS and recorded at 0, 200,400, 600 and 1000 h of exposure. Coating performance changed with time of exposure. The main degradation process is due to the hydrolysis of the coating. A decrease in corrosion rate was observed due to the sealing of the coating, probably due to the deposition of corrosion products, salts, or a mixture of both. EN (electrochemical noise) was a more sensitive technique comapred to EIS (electrochemical impedance spectroscopy). The first changes in the coating were detected after 400 h of exposure by EIS and after 200 h by EN. EIS and EN showed equivalent results in studying the corrosion evolution of coated aluminum. Non-linear analysis using recursive plots (RP) showed the chaotic dynamics occurring with time and the interaction of micro electrochemical cells that formed on the metallic surface; it offered information similar tothe traditional EIS technique and adds complementary data to understand the corrosion phenomenon.

Applying RUSLE for soil erosion estimation in Romania under current and future climate scenarios

Soil erosion is one of the main land degradation processes, often enhanced by unsuitable human activities. In the context of global climate change, soil erosion also exhibits quantitative and qualitative changes induced by the temporally dynamic erosion factors, namely rainfall erosivity and land use. Our study attempts to forecast the evolution of soil erosion rates under climate change scenarios over the Romanian territory. Firstly, we apply the Revised Universal Soil Loss Equation (RUSLE) methodology to achieve a spatial model of soil erosion for the current climate conditions. Secondly, we use projections of rainfall erosivity to derive soil erosion models for two future climate change scenarios (Representative Concentration Pathway - RCP 4.5 and 8.5) and two periods of time (2041–2060, 2061–2080). Thirdly, we compute the differences between future projected and current erosion rates to identify spatial patterns of soil erosion evolution. The results show that, under the influence of rainfall erosivity dynamics, soil erosion tends to increase during the next decades. Overall, an enhancement of soil erosion rates on 84–90% of the country is expected to take place. Most of the erosion rates will increase slightly, with <1 t ha−1 yr−1, from an overall average of 2.94 t ha−1 yr−1, at present, to 3.67 (2061–2080, RCP 8.5) – 3.74 (2041–2060, RCP 8.5) t ha−1 yr−1 at country level. Locally, the erosion rates may increase with >5–10 t ha−1 yr−1 on areas estimated to cumulate >8000 km2. The most affected areas will be the soils situated in hilly and plateau regions, leading to an enhancement of their fertility degradation.

A COMPLEX APPROACH IN ASSESSING RELIABILITY INDICATORS OF ELEMENTS OF TECHNICAL SYSTEMS WHEN DEGRADATION FAILURES OCCUR

The construction and practical use of complexes of mechanical reliability models creates real prerequisites for the transition to resource design of assembly units and aggregates of mobile machines. Therefore, the article solves the tasks of building complexes of inverted stochastic models, which provide the possibility of joint statistical analysis of heterogeneous information about reliability in cases of types of destruction typical for machine elements: during wear and fatigue. A fairly complete and convenient method for solving many problems of mechanical reliability is given for describing a non-stationary monotonic degradation process, which consists in the task of the type of its function or the density of distribution in time segments with parameters that are deterministic monotonic functions of time or working time in load cycles. Such functions should be perceived as parametric. Schemes of models of two main types of degradation processes in machine elements are also given: monotonically increasing, associated with wear and monotonically decreasing, due to fatigue failure. At the same time, the process corresponding to wear is formed by random realizations of a change in the failure parameter over time, and the process characterizing fatigue failure is formed by a set of random individual fatigue curves that depend on cyclic durability. The considered theoretical analysis of the main degradation processes that determine the mechanical reliability of machine elements made it possible to develop a universal approach to building complexes of stochastic reliability models, which provides the possibility of joint statistical evaluation of model parameters for processes caused by wear and tear and fatigue destruction. The practical use of the proposed complexes of mechanical reliability models is expedient both for accelerated assessment and for predicting reliability at the stage of resource design of elements of mobile machines.

Carbon steel corrosion in a bentonite buffer: A comparison between in situ exposure and lab based experiments

AbstractIn this paper, carbon steel corrosion rates from experiments performed in situ (performed in an underground rock laboratory) and ex situ (performed in a conventional laboratory) test methods in anaerobic saturated bentonite are compared. The results indicate that the long‐term corrosion rate follows a power law decay curve, with a higher initial rate and greater rate of decay at higher temperature. In compacted bentonite blocks, varying the density has no significant effect on the corrosion rate measured during in situ testing, whereas granular bentonite of an equal dry density leads to a higher corrosion rate. Precorrosion of test specimens in an aerated solution at room temperature has a negligible effect on the subsequent anaerobic corrosion rate when tested ex situ for durations up to 11.8 years. The main difference between in situ and ex situ tests is the formation of silicon‐rich corrosion products in the ex situ tests but not in the in situ tests. Despite these differences, the corrosion rates in both tests exhibit the same general temporal evolution and similar magnitudes, suggesting that the main steel degradation processes are maintained in both configurations.

КОРРЕКТИРОВАНИЕ ПЕРИОДИЧНОСТИ ОПЕРАЦИЙ ТЕХНИЧЕСКОГО СЕРВИСА МОБИЛЬНЫХ МАШИН С УЧЕТОМ ЖЕСТКОСТИ КЛИМАТА

Based on the analysis of the main operational factors, among which, for specific areas of equipment supply, one of the main ones is the climatic factor, as well as the main damaging degradation processes during the operation of machines, an effective mechanism for planning the frequency of maintenance operations is proposed, which helps to ensure a high level of technical readiness of machines. The operability potential was analyzed, its active, reserve and passive parts were considered, which made it possible to present a model for changing and restoring the operability potential of a mobile machine. Mathematical dependences are given for certain models of machines of the same functional purpose, as well as characterizing processes of reducing the potential of their performance in a certain external environment, their transformation is noted when changing natural and climatic operating conditions. The construction of a priori diagram of the ranks of climatic factors made it possible to note that the most significant adverse effect is exerted by temperature, humidity and solar radiation in the operating area. Taking into account the distribution of zones of technical rigidity of the climate, its score and the coefficient of continentality, a method is proposed for correcting the frequency of operations of technical service of transport-technological machines for the zone of their actual operation.

Degradation kinetics and transformation pathway of methyl parathion by δ-MnO2/oxalic acid reaction system

Methyl parathion (MP) is a typical organophosphorus pesticide that is widely used worldwide, and hydrolysis, oxidation and reduction are the main abiotic degradation processes. Manganese dioxide (MnO2) and organic acid can participate in various geochemical processes of pollutants, a reaction system was constructed to degrade MP using δ-MnO2 and oxalic acid. The δ-MnO2/oxalic acid reaction system could efficiently degrade MP, and the removal rate of MP (20 μM) reached 67.83% within 30 h under the optimized conditions (pH 5, [δ-MnO2] = 2 mM, [oxalic acid] = 100 mM). MP was hydrolyzed by substitution reactions of SN@P and SN@C, and reduced by conversion of the nitro groups (-NO2) in MP and its hydrolysates to amino groups (-NH2). The primary active substance produced in the reaction system was the complexes dominated by Mn(III)-oxalic acid. This study provides a scientific basis for the degradation of organophosphorus pesticides using MnO2 and an organic acid. The results have important theoretical significance and application value for pollution control and remediation of organophosphorus pesticides.

Enhanced removal of tetrabromobisphenol A by Burkholderia cepacian Y17 immobilized on biochar

Biochar-immobilized bacteria have been widely used to remove organic pollutants; however, the enhanced effect of biochar-immobilized bacteria on tetrabromobisphenol A (TBBPA) removal has not been fully investigated and the removal mechanism remains unclear. In this study, a bacterial strain with high TBBPA degradation ability, Burkholderia cepacian Y17, was isolated from an e-waste disassembly area, immobilized with biochar, and used for the removal of TBBPA. Comparisons were performed of the factors affecting the immobilization and TBBPA removal efficiency, including the biochar preparation temperature, immobilization temperature, and pH. The highest 7-day TBBPA removal efficiency by immobilized bacteria was observed with the most suitable biochar preparation temperature (BC500) and an immobilization pH and temperature of 7 and 35 °C, respectively. The TBBPA removal efficiency reached 59.37%, which was increased by 30.23% and 15.88% compared to that of free and inactivated immobilized Y17, respectively. The suitable biochar preparation temperature BC500, immobilization temperature of 35 °C, and neutral pH of 7 increased the bacterial population and extracellular polymer concentration, which facilitated bacterial immobilization on biochar and promoted TBBPA removal. In this case, the high immobilized bacteria concentration (4.62 × 108 cfu∙g−1) and protein and polysaccharide contents (28.43 and 16.16 mg·g−1) contributed to the removal of TBBPA by facilitating TBBPA degradation. The main TBBPA degradation processes by BC500-immobilized Y17 involved debromination, β-scission, demethylation, O-methylation, hydroxylation, and hydroxyl oxidation. This study proposes a method for preparing immobilized bacteria for TBBPA removal and enriches the microbial degradation technology for TBBPA.

Influence of Stabilization Additive on Rheological, Thermal and Mechanical Properties of Recycled Polypropylene.

To decrease the amount of plastic waste, the use of recycling techniques become a necessity. However, numerous recycling cycles result in the mechanical, thermal, and chemical degradation of the polymer, which leads to an inefficient use of recycled polymers for the production of plastic products. In this study, the effects of recycling and the improvement of polymer performance with the incorporation of an additive into recycled polypropylene was studied by spectroscopic, rheological, optical, and mechanical characterization techniques. The results showed that after 20 recycling steps of mechanical processing of polypropylene, the main degradation processes of polypropylene are chain scission of polymer chains and oxidation, which can be improved by the addition of a stabilizing additive. It was shown that a small amount of an additive significantly improves the properties of the recycled polypropylene up to the 20th reprocessing cycle. The use of an additive improves the rheological properties of the recycled melt, surface properties, and time-dependent mechanical properties of solid polypropylene since it was shown that the additive acts as a hardener and additionally crosslinks the recycled polymer chains.

Vanishing evidence? On the longevity of geomorphic GLOF diagnostic features in the Tropical Andes

Trends in occurrence of glacial lake outburst floods (GLOFs) in space and time as well as frequency-magnitude relationships are typically derived from inventories of past GLOFs. Searching for geomorphic evidence (GLOF diagnostic features) in remote sensing images is a commonly used method for building GLOF inventories. In this study, I examine the longevity of geomorphic GLOF diagnostic features and thus the reliability of GLOF inventories that build on them. A set of 160 GLOFs documented from the Tropical Andes of Peru and Bolivia is analyzed, focusing on four GLOF diagnostic features: (i) breached dams; (ii) pre-GLOF water levels; (iii) outwash fans; (iv) impact areas. A total of 359 GLOF diagnostic features are identified and their evolution is analyzed from multi-decade remote sensing images, with special focus on GLOF diagnostic features that vanished in time. Building on these data, the expected longevity of GLOF diagnostic features is outlined, revealing long persistence of breached dams (>102 years), long persistence of pre-GLOF water levels (up to 102 years) and comparably more intense degradation and vanishing of outwash fans and impact areas. The main degradation processes of GLOF diagnostic features are identified, including the succession of vegetation, geomorphic reworking and anthropogenic activities. Further, the implications for building GLOF inventories are discussed, highlighting that vanishing geomorphic evidence of GLOF diagnostic features may lead to: (i) underestimated spatial extent of GLOF impact areas; and (ii) underestimated total numbers of GLOFs in GLOF inventories. Considering the number of major GLOFs as predictors of the number of minor GLOFs, an example of the Tropical Andes shows that the total number of GLOFs in the post-LIA period may be underestimated by up to 40 % (reference period 2011–2020).

Mapping of the degradation processes at bifunctional O2 gas diffusion electrode for aqueous alkaline metal-air batteries

Rechargeable aqueous alkaline zinc-air batteries present, in principle, auspicious characteristics for the stationary storage of electricity produced by intermittent renewables. Still, a number of issues associated with the durability of the electrocatalytic performances of the air cathode hinder further implementation of this battery technology. A recent article (J. Power Sources 482 (2021) 22,890) details a high-performance gas diffusion electrode (GDE) embedding a bi-functional catalyst for the oxygen evolution and oxygen reduction reactions. Now, aiming at a better understanding of the degradation processes taking place at such electrode, we detail a multi-scale approach based on a combination of results from electrochemical, electron imaging and spectroscopic techniques (EIS, SEM, XPS, operando EXAFS). Insights gained resolve the main degradation processes occurring at different length-scales (Å vs. μm), chemical and structural changes at the electrode components level, as well as of their interrelations. The degradation mapping realized at the gas diffusion electrode level and under current loads relevant for practical application paves the way for further improvements of the electrode architecture. In addition, model quantitative XPS analysis, cell design for operando EXAFS and differential analysis of the EXAFS data introduced herein, are applicable to any type of GDE architecture for electrode durability studies.

Images in transformation: The color and its change in a group of Portuguese paintings from the second half of the 16th century

AbstractFour panel paintings depicting episodes related to the birth of Christ and attributed to the Portuguese mannerist painter Francisco João (doc. 1558–1585) were found to exhibit a muted palette that had no correspondence with the traditionally vivid colors used in the sixteenth century to represent joyful biblical events. Complementing previous research on the disruption and loss of the red glazes in these paintings, the investigation focused on the analysis of materials, painting technique and degradation issues that further affected the original paintings, changing the viewer's perception and understanding of these artworks. The investigation combined the visual examination of the painting surface with microscopic and spectroscopic analysis of the binder and pigments. A conventional palette made of lead white, lead‐tin yellow, ochres, vermilion, verdigris, smalt, azurite, carbon black and a red lake made of brazilwood and cochineal was identified. The pigments were bound in an oil‐based medium. Chemical and physical alterations detected in paints rich in smalt and verdigris were found to be responsible for color changes affecting significant areas of the compositions. The presence of moisture and the reaction between pigment and binder leading, among other products, to soap and oxalate formation, played a central role in the long‐term behavior of the paint film. Understanding the main degradation processes involved and their consequences is crucial when interpreting an artists' color palette and designing the best approach to preserve these paintings.

Isolation and Screening from Soil Biodiversity for Fungi Involved in the Degradation of Recalcitrant Materials.

Environmental pollution is an increasing problem, and identifying fungi involved in the bioremediation process is an essential task. Soil hosts an incredible diversity of microbial life and can be a good source of these bioremediative fungi. This work aims to search for soil fungi with bioremediation potential by using different screening tests. Mineral culture media supplemented with recalcitrant substances as the sole carbon source were used as growth tests. First, soil dilutions were plated on Petri dishes with mineral medium amended with humic acids or lignocellulose. The growing fungal colonies were isolated and tested on different substrates, such as complex mixtures of hydrocarbons (petrolatum and used motor oil) and powders of different plastic polymers (PET, PP, PS, PUR, PVC). Qualitative enzymatic tests were associated with the growth tests to investigate the production of esterases, laccases, peroxidases, and proteases. These enzymes are involved in the main degradation processes of recalcitrant material, and their constitutive secretion by the examined fungal strains could have the potential to be exploited for bioremediation. More than 100 strains were isolated and tested, and several isolates with good bioremediation potential were found. In conclusion, the described screening tests are an easy and low-cost method to identify fungal strains with bioremediation potential from the soil. In addition, it is possible to tailor the screening tests for different pollutants, according to requirements, by adding other recalcitrant substances to minimal culture media.