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Post-industrial low-density and linear low-density polyethylene blown films are mechanically recycled for reutilizing in the production of blown films for packaging applications. This process enables the production of films with lower cost and similar properties while preserving the environment and lowering the amount of waste material disposed of. The mechanical recycling process results in the production of recycled pellets. This process includes chopping, washing, drying, and reprocessing. Mixtures of these recycled materials and their virgin form with various concentrations are shaped into blown films with inherent 70 and 30 wt% loadings for low-density polyethylene and linear low-density polyethylene components, respectively. Fourier transform infrared spectroscopy results of the recycled material show no contamination or chemical reaction with other materials. Gel permeation chromatography is carried out on the virgin and recycled low-density polyethylene and linear low-density polyethylene, and the results indicate the occurrence of chain session and crosslinking during the recycling process. The decline in the thermal properties of the samples, seen from the differential scanning calorimetry results, indicates the presence of crosslinks. The effect of structural changes caused by the recycling process on the rheological properties is studied. The miscibility of the blend components is evaluated by Cole-Cole plots and then further proved by Han and Van Gurp-Palman curves. Mechanical properties display an upturn following the presence of the crosslinkes. A decline in the optical properties in the films caused by the refraction of light by the crosslink structure in the film bulk and on the surface is evident. Highlights * LDPE and LLDPE were recycled according to the circular economy approach * Blown films containing virgin and recycled LDPE and LLDPE were produced * Chain scission and crosslinking as a result of recycling were studied * Rheological, thermal, mechanical, and optical properties were studied KEYWORDS circular economy, crosslinking, mechanical properties, polyethylene, recycling, rheological properties, 1 | INTRODUCTION The vast applicability of plastics due to their lightweight and ease of processing, along with other desirable features like high strength and sensible prices, has made them [...]

During the mid-Pliocene warm period (mPWP; 3.264–3.025 Ma), atmospheric CO2 concentrations were approximately 400 ppm, and the Antarctic Ice Sheet was substantially reduced compared to today. Antarctica is surrounded by the Southern Ocean, which plays a crucial role in the global oceanic circulation and climate regulation. Using results from the Pliocene Model Intercomparison Project (PlioMIP2), we investigate Southern Ocean conditions during the mPWP with respect to the pre-industrial period. We find that the mean sea surface temperature (SST) warming in the Southern Ocean is 2.8 °C, while global mean SST warming is 2.4 °C. The enhanced warming is strongly tied to a dramatic decrease in sea ice cover over the mPWP Southern Ocean. We also see a freshening of the ocean (sub)surface, driven by an increase in precipitation over the Southern Ocean and Antarctica. The warmer and fresher surface leads to a highly stratified Southern Ocean that can be related to weakening of the deep abyssal overturning circulation. Sensitivity simulations show that the decrease in sea ice cover and enhanced warming is largely a consequence of the reduction in the Antarctic Ice Sheet. In addition, the mPWP geographic boundary conditions are responsible for approximately half of the increase in mPWP SST warming, sea ice loss, precipitation, and stratification increase over the Southern Ocean. From these results, we conclude that a strongly reduced Antarctic Ice Sheet during the mPWP has a substantial influence on the state of the Southern Ocean and exacerbates the changes that are induced by a higher CO2 concentration alone. This is relevant for the long-term future of the Southern Ocean, as we expect melting of the western Antarctic Ice Sheet in the future, an effect that is not currently taken into account in future projections by Coupled Model Intercomparison Project (CMIP) ensembles.

Paleoclimate reconstructions across Iceland provide a template for past changes in climate across the northern North Atlantic, a crucial region due to its position relative to the global northward heat transport system and its vulnerability to climate change. The roles of orbitally driven summer cooling, volcanism, and human impact as triggers of local environmental changes in the Holocene of Iceland remain debated. While there are indications that human impact may have reduced environmental resilience during late Holocene summer cooling, it is still difficult to resolve to what extent human and natural factors affected Iceland's late Holocene landscape instability. Here, we present a continuous Holocene fire record of northeastern Iceland from proxies archived in Stóra Viðarvatn sediment. We use pyrogenic polycyclic aromatic hydrocarbons (pyroPAHs) to trace shifts in fire regimes, paired with continuous biomarker and bulk geochemical records of soil erosion, lake productivity, and human presence. The molecular composition of pyroPAHs and a wind pattern reconstruction indicate a naturally driven fire signal that is mostly regional. Generally low fire frequency during most of the Holocene significantly increased at 3 ka and again after 1.5 ka BP before known human settlement in Iceland. We propose that shifts in vegetation type caused by cooling summers over the past 3 kyr, in addition to changes in atmospheric circulation, such as shifts in North Atlantic Oscillation (NAO) regime, led to increased aridity and biomass flammability. Our results show no evidence of faecal biomarkers associated with human activity during or after human colonisation in the 9th century CE. Instead, faecal biomarkers follow the pattern described by erosional proxies, pointing toward a negligible human presence and/or a diluted signal in the lake's catchment. However, low post-colonisation levels of pyroPAHs, in contrast to an increasing flux of erosional bulk proxies, suggest that farming and animal husbandry may have suppressed fire frequency by reducing the spread and flammability of fire-prone vegetation (e.g. heathlands). Overall, our results describe a fire frequency heavily influenced by long-term changes in climate through the Holocene. They also suggest that human colonisation had contrasting effects on the local environment by lowering its resilience to soil erosion while increasing its resilience to fire.

The Great Plains of North America host a stark climatic gradient, separating the humid and well-watered eastern US from the semi-arid and arid western US, and this gradient shapes the region's water availability, its ecosystems, and its economies. This climatic boundary is largely set by the influence of two competing atmospheric circulation systems that meet over the Great Plains – the wintertime westerlies bring dominantly dry air that gives way to moist, southerly air transported by the Great Plains low-level jet in the warmer months. Climate model simulations suggest that, as CO2 rises, this low-level jet will strengthen, leading to greater precipitation in the spring but less in the summer and, thus, no change in mean annual precipitation. Combined with rising temperatures that will increase potential evapotranspiration, semi-arid conditions will shift eastward, with potentially large consequences for the ecosystems and inhabitants of the Great Plains. We examine how hydroclimate in the Great Plains varied in the past in response to warmer global climate by studying the paleoclimate record within the Ogallala Formation, which underlies nearly the entire Great Plains and provides a spatially resolved record of hydroclimate during the globally warmer late Miocene. We use the stable isotopes of oxygen (δ18O) as preserved in authigenic carbonates hosted within the abundant paleosol and fluvial successions that comprise the Ogallala Formation as a record of past hydroclimate. Today, and coincident with the modern aridity gradient, there is a sharp meteoric water δ18O gradient with high (−6 ‰ to 0 ‰) δ18O in the southern Great Plains and low (−12 ‰ to −18 ‰) δ18O in the northern plains. We find that the spatial pattern of reconstructed late Miocene precipitation δ18O is indistinguishable from the spatial pattern of modern meteoric water δ18O. We use a recently developed vapor transport model to demonstrate that this δ18O spatial pattern requires air mass mixing over the Great Plains between dry westerly and moist southerly air masses in the late Miocene – consistent with today. Our results suggest that the spatial extents of these two atmospheric circulation systems have been largely unchanged since the late Miocene and any strengthening of the Great Plains low-level jet in response to warming has been isotopically masked by proportional increases in westerly moisture delivery. Our results hold implications for the sensitivity of Great Plains climate to changes in global temperature and CO2 and also for our understanding of the processes that drove Ogallala Formation deposition in the late Miocene.

Grain prices in early modern Europe reflected the effects of weather and climate on crop yields and a complex array of societal and socio-economic factors. This study presents a newly developed series of grain prices for Sušice (southwestern Bohemia, Czech Republic) for the period 1725–1824 CE, based on various archival sources. It aims to analyse their relationships with weather and climate, represented by temperature, precipitation, and drought (self-calibrated Palmer Drought Severity Index, scPDSI) reconstructions, as well as particular weather extremes and anomalies reported in documentary evidence. Wheat, rye, barley, and oats series in Sušice showed high mutual correlations. The mean highest prices during the year typically occurred from May to July before the harvest, while prices usually declined afterwards. Wheat, rye, and barley prices were significantly negatively correlated with spring temperatures and positively correlated with scPDSI from winter to summer. This indicates that wetter winters, cooler and wetter springs, and wetter summers contributed to higher prices. The extremely high grain prices in the years 1746, 1771–1772, 1802–1806, and 1816–1817 were separately analysed with respect to weather and climate patterns and other socio-economic and political factors. The results obtained were discussed in relation to data uncertainty, factors influencing grain prices, and the broader European context.

Laboratory experiments showed that the isotopic fractionation of δ13C and of δ18O during calcite formation of planktic foraminifera are species-specific functions of ambient CO32- concentration. This effect became known as the carbonate ion effect (CIE), whose role for the interpretation of marine sediment data will be investigated here in an in-depth analysis of the 13C cycle. For this investigation, we constructed new 160 kyr long mono-specific stacks of changes in both δ13C and δ18O from either the planktic foraminifera Globigerinoides ruber (rub) or Trilobatus sacculifer (sac) from 112 and 40 marine records, respectively, from the wider tropics (latitudes below 38°). Both mono-specific time series Δ(δ13Crub) and Δ(δ13Csac) are very similar to each other, and a linear regression through a scatter plot of both data sets has a slope of ∼ 0.99 – although the laboratory-based CIE for both species differs by a factor of nearly 2, implying that they should record distinctly different changes in δ13C, if we accept that the carbonate ion concentration changes on glacial–interglacial timescales. For a deeper understanding of the 13C cycle, we use the Solid Earth version of the Box model of the Isotopic Carbon cYCLE (BICYLE-SE) to calculate how surface-ocean CO32- should have varied over time in order to be able to calculate the potential offsets which would by caused by the CIE quantified in culture experiments. Our simulations are forced with atmospheric reconstructions of CO2 and δ13CO2 derived from ice cores to obtain a carbon cycle which should at least at the surface ocean be as close as possible to expected conditions and which in the deep ocean largely agrees with the carbon isotope ratio of dissolved inorganic carbon (DIC), δ13CDIC, as reconstructed from benthic foraminifera. We find that both Δ(δ13Crub) and Δ(δ13Csac) agree better with changes in simulated δ13CDIC when ignoring the CIE than those time series which were corrected for the CIE. The combination of data- and model-based evidence for the lack of a role for the CIE in Δ(δ13Crub) and Δ(δ13Csac) suggests that the CIE as measured in laboratory experiments is not directly transferable to the interpretation of marine sediment records. The much smaller CIE-to-glacial–interglacial-signal ratio in foraminifera δ18O, when compared to δ13C, prevents us from drawing robust conclusions on the role of the CIE in δ18O as recorded in the hard shells of both species. However, theories propose that the CIE in both δ13C and δ18O depends on the pH in the surrounding water, suggesting that the CIE should be detectable in neither or both of the isotopes. Whether this lack of role of the CIE in the interpretation of planktic paleo-data is a general feature or is restricted to the two species investigated here needs to be checked with further data from other planktic foraminiferal species.

Climate reconstructions of the last millennium rely on networks of high-resolution and well-dated proxy records. This study presents age-at-depth data and preliminary results from the new Mount Brown South (MBS) ice cores, collected at an elevation of 2084 m on the boundary of Princess Elizabeth Land and Kaiser Wilhelm II Land in East Antarctica. We show an initial analysis of the site meteorology, mean annual chemical species concentrations and seasonal cycles, including the identification of a seasonal cycle in fluoride concentrations. The annually resolved chronologies were developed from the chemistry data using a site-specific layer-counting methodology that employed seasonally varying trace chemical species and stable water isotopic ratios, combined with alignment to known volcanic horizons. The uncertainty in the determination of annual horizons via layer counting was also quantified. The chronologies developed include the “Main” 295 m record spanning 1137 years (873–2009 CE) and three surface cores spanning the most recent 39–52 years up to the surface age at the time of drilling (austral summer 2017/2018). Mean annual trace chemical concentrations are compared to the Law Dome ice core (located 1130 km east of the Mount Brown South site) and discussed in terms of atmospheric transport. The MBS chronologies presented here – named MBS2023 – will underpin the development of new palaeoclimate records spanning the past millennium from this under-represented region of East Antarctica.

Abstract Volcano-hazard maps are broadly recognized as important tools for forecasting and managing volcanic crises and for disseminating spatial information to authorities and people at risk. As scientists, we might presume that hazards maps can be developed at the time and with the methods of our discretion, yet the co-production of maps with stakeholder groups, who have programmatic needs of their own, can sway the timing, usability, and acceptance of map products. We examine two volcano hazard map-making efforts by staff at the U.S. Geological Survey. During the 1990s and early 2000s scientists developed a series of hazard assessments and maps with detailed zonations for volcanoes in Washington and Oregon. In 2009, the National Park Service expressed the need for simplified versions of the existing hazard maps for a high-profile visitor center exhibit. This request created an opportunity for scientists to rethink the objectives, scope, content, and map representations of hazards. The primary focus of this article is a discussion of processes used by scientists to distill the most critical information within the official parent maps into a series of simplified maps using criteria specified. We contextualize this project with information about development of the parent maps, public response to the simplified hazard maps, the value of user engagement in mapmaking, and with reference to the abundance of guidance available to the next generation of hazard-mapmakers. We argue that simplified versions of maps should be developed in tandem with any hazard maps that contain technical complexities, not as a replacement, but as a mechanism to broaden awareness of hazards. We found that when scientists endeavor to design vivid and easy-to-understand maps, people in many professions find uses for them within their organization’s information products, resulting in extensive distribution.

The Mt Samalas eruption, thought to have occurred in summer 1257, ranks as one of the most explosive sulfur-rich eruptions of the Common Era. Despite recent convergence, several dates have been proposed for the eruption ranging between 1256–1258, with, as of yet, no single combination of evidence that has been able to robustly distinguish between and exclude the other dates proposed for the Mt Samalas eruption. Widespread surface cooling and hydroclimate perturbations following the eruption have been invoked as contributing to a host of 13th century social and economic crises, although regional-scale variability in the post-eruption climate response remains uncertain. In this study we run ensemble simulations using the UK Earth System Model (UKESM1) with a range of eruption scenarios and initial conditions in order to compare our simulations with the most complete globally resolved multi-proxy database for the Mt Samalas eruption to date, incorporating tree rings, ice cores, and historical records. This allows more precise constraints to be placed on the year and season of the Mt Samalas eruption, as well as an investigation into the regionally heterogeneous post-eruption climate response. Using a multi-proxy to model comparison, we are able to robustly distinguish between July 1257 and January 1258 eruption scenarios, where the July 1257 ensemble simulation achieves considerably better agreement with spatially averaged and regionally resolved proxy surface temperature reconstructions. These reconstructions suggest the onset of significant cooling across Asia and Europe in 1258 and thus support the plausibility of previously inferred historical connections. Model-simulated temperature anomalies also point to severe surface cooling across the Southern Hemisphere with as of yet unexplored historical implications for impacted civilisations. Model simulations of polar sulfate deposition also reveal distinct differences in the timing of ice sheet deposition between the two simulated eruption dates, although comparison of the magnitude or asymmetric deposition of sulfate aerosol remains limited by large inter-model differences and complex intra-model dependencies. Overall, the multi-proxy to model comparison employed in this study has strong potential in constraining similar uncertainties in eruption source parameters for other historical eruptions for which sufficient coincident proxy records are available, although care is needed to avoid the pitfalls of model–multi-proxy comparison.

The Middle Eocene Climatic Optimum (MECO) is a global warming event mainly recognized in the marine domain and described less in the terrestrial environment. Here we present a comprehensive geochemical record of the MECO from the Escanilla Formation, a fluvial sedimentary succession in the southern Pyrenees, Spain, based on a suite of sampled paleosols, fluvial stromatolites, and pedogenic nodules. Our multiproxy approach involves using carbon and oxygen stable isotope compositions to identify the regional preservation of the MECO, calculate chemical weathering intensity and mean annual precipitation, perform clumped isotopes on carbonates, and identify clay mineralogy assemblages of paleosols. Results indicate that the Middle Eocene interval in the southern Pyrenees was characterized by low weathering rates under warm and arid climatic conditions. This is further supported by the presence of smectite, palygorskite, illite, and chlorite, which suggest seasonal rainfall but under generally dry conditions resulting in weak chemical weathering. Importantly, a negative organic carbon isotopic excursion indicates the regional, terrestrial impact of the MECO, highlighting that fluvial sedimentary successions even in active foreland basins can represent particularly interesting terrestrial archives of past changes in global climate.

Le pétrole communément appelé " or noir " est une source d’énergie qui a façonné le destin économique de plusieurs pays. La commercialisation des produits dérivés du pétrole permet à un pays de se développer et apporter un bien-être à la population. Cependant, ces produits sont très dangereux à la manipulation. La Côte d’Ivoire est un pays qui effectue chaque année d’énormes échanges de ces types de produits. La quasi-totalité de ses produits transitent par le Port Autonome d’Abidjan à travers de nombreuses installations pétrolifères. Pour la plupart, elles y sont installées et fonctionnent depuis les années de l’indépendance. Ces installations présentent un état de vieillissement qui pourrait entrainer d’énormes risques de déversement, de toxicité, d’explosion et d’incendie dans la ville d’Abidjan. La présente étude vise à connaitre les risques liés au vieillissement des installations pétrolières portuaires d’Abidjan. Pour atteindre notre objectif, la méthode de travail utilisée a été une enquête basée sur deux étapes afin d’obtenir des informations précises. Ces étapes sont la recherche documentaire, les enquêtes de terrain (semi-structurées et par questionnaire). Ainsi nous sommes-nous servis d’appareil photo pour des prises de vue, d’un magnétophone pour l’enregistrement des interviews et d’un GPS. Il résulte de ces enquêtes que le Port Autonome d’Abidjan regorge de 75% des installations et équipements pétrolifères en Côte d’Ivoire. Cependant, l’installation de ces infrastructures date pour la plupart d’avant les indépendances. Ces infrastructures peu entretenues présentent des signes de vétusté qui pourraient mettre en danger les opérations de transfert, de chargement et de déchargement d’hydrocarbures pour l’alimentation des différents terminaux pétroliers portuaires.

Depuis quelques années, l’accès des populations aux services publics se pose comme un défi épineux pour les Etats africains. Les technologies de communication et d’information sont devenues les outils incontournables pour répondre aux défis d’accessibilité des services publics par les populations. Le numérique offre assez de possibilités pour assurer et réduire la fracture qui règne dans l’octroi des prestations publiques au profit des populations. Conscient de ces avantages, le Togo s’est doté de politiques adéquates à travers son Ministère de l’Économie Numérique afin de dématérialiser et de faciliter l’accès aux services publics. La matérialisation de cette volonté politique s’explique par la mise en place des plateformes numériques notamment celle du site service-public pour la demande des pièces d’identité, la demande du casier judiciaire, la demande d’un duplicata, d’un certificat de nationalité, le suivi de la demande initiale de nationalité et la demande de passeport dans le Grand Lomé. L’objectif de cette recherche est d’analyser la contribution du site service-public dans l’accès aux prestations des services publics. Cet article a mobilisé des données d’un sondage effectué en ligne auprès des populations du Grand-Lomé. Les résultats montrent que les populations sont informées de l’existence du site service-public et l’utilisent pour la demande du casier judiciaire, dans la majeure partie des cas, à cause du délai de traitement court. Le niveau faible de connexion ainsi que la limitation des options de paiement rendent difficile l’usage de la plateforme. Toutefois, le site service-public apporte une proximité numérique, qui vient effacer dans le Grand Lomé la distance géographique entre les lieux d’habitations des populations et les services publics.

Les villes vertes, villes durables ou écologiques, sont des villes imaginées pour minimiser leur impact sur l'environnement et promouvoir une qualité de vie élevée pour leurs habitants. En Afrique Subsaharienne, nonobstant la forte urbanisation incontrôlée dans des cas, des initiatives/innovations jugées écologiques par leurs acteurs sont en train d’être mises en œuvre un peu partout. Cette étude analyse les défis auxquels certaines de ces actions se heurtent au Sénégal dans le secteur de l’éco-construction. La méthodologie est basée sur des recherches documentaires et des enquêtes de terrain. La Voûte Nubienne (VN) dans les villes du nord Sénégal (Podor, Matam et Kanel) et le Bloc de Terre Compressé (BTC) à Dakar ont été pris comme échantillons d’analyse de par les présentations théoriques, techniques, les acteurs, la méthode de diffusion et l’état d’adoption. Les résultats ont montré que les défis d’application de ces actions en ville peuvent être liés, d’une part, aux problèmes de vulgarisation et, d’autre part, aux problèmes de contenu (techniques, financiers, socio-culturels) par rapport aux réalités des espaces d’accueil. La prise en compte de ces défis peut ouvrir plusieurs perspectives d’adaptation.

Considérée comme la plus grande ville du nord ivoirien, Korhogo a connu un dynamisme démographique et spatial important. Pour une surface urbanisée qui s’est accrue de 164% entre 1985 et 2016, la population a, quant à elle, atteint, selon l’INS (2021), un effectif de 440926. Fort de cette situation, les besoins des populations se sont accrus notamment dans l’approvisionnement divers (alimentations, eau, électricité, services sociaux). Pour se loger, les ménages ont investi les interstices et les extensions périphériques de la ville, créant ainsi de nouveaux fronts urbains. Dans le contexte mondial de la promotion des villes durables, nous avons été amenés à jeter un regard sur les pratiques immobilières des populations. Pendant que la technique de l’observation nous a permis d’apprécier les modes de construction des logements, les entretiens réalisés et le questionnaire administré aux 900 chefs de ménages ont eu pour objet la connaissance des caractéristiques écolo-technologiques des habitations. Il ressort de cette étude que l’architecture immobilière horizontale, facteur d’étalement urbain, est dominante dans la ville. Par ailleurs, loin d’utiliser des matériaux de construction écologique, le béton demeure le matériau favori. Les pratiques locales constituent en toute évidence des facteurs limitants pour la promotion de la durabilité urbaine. Il paraît donc pertinent d’associer politiques du logement et politiques urbaines, pour un développement de la cité qui tient compte de la qualité du cadre de vie et de la préservation des ressources naturelles.

La prolifération des lieux de culte, l’installation des bars et boites voire de lieux de tolérances et garages représentent des sources de nuisances qui causent des troubles au voisinage. L’on trouve des règles de droit qui protège le voisinage contre le bruit. Il en existe deux catégories. La première constituée de règles générales applicables en vue de la résolution de la question du bruit dans le voisinage et des règles spécialement établies en vue de la protection du voisinage contre le bruit. Pourtant, les nuisances résultant des activités évoquées persistent et troublent la tranquillité et la santé ; diminuant ainsi la qualité de vie des personnes. Dès lors, la protection offerte par la législation en vigueur est-elle efficace ? En réalité, l’on doit comprendre que la protection du voisinage par l’application des règles générales s’est révélée limitée. En conséquence, le législateur a créé des règles spéciales en vue de ladite protection. Mais, ces règles laissent subsister des incertitudes. C’est pourquoi l’étude de la protection du voisinage porte, d’une part, sur la protection du voisinage contre le bruit par l’application de règles générales contrariée et d’autre part, sur la protection discutable du voisinage contre le bruit par des règles spéciales.

L’espace marin et côtier du Togo joue un rôle essentiel dans l’économie du pays, en contribuant à la création d’emplois directs et indirects, à la sécurité alimentaire, à la résilience économique et sociale, à la régulation du climat et à la fourniture d’habitats à des milliers d’espèces. Toutefois, les activités tendent à se développer sur cet espace ; ce qui accroît l’exposition aux risques de conflits d’usage. C’est pour anticiper ces risques que les autorités togolaises ont adopté la planification spatiale marine (PSM) en 2020. Ce travail a pour objectif de montrer l’apport de la démarche sociologique dans la mise en œuvre de la PSM au Togo. À partir de l’exploitation de diverses sources documentaires et des résultats d’entretiens, la recherche tente de démontrer que la mise en œuvre de la PSM a mobilisé des concepts sociologiques (acteur, conflit, participation, intégration, citoyenneté). Il en résulte que la PSM au Togo repose sur la prise en compte des besoins des différentes parties prenantes, notamment les pouvoirs publics, le secteur privé maritime, les écologistes, les pêcheurs et tous les détenteurs de droits.

Les villes d’Afrique Subsaharienne, pour la plupart, connaissent des problèmes liés à la gestion de l’espace urbain. Même au niveau des collectivités locales de taille moyenne, le déphasage entre la dynamique urbaine et les capacités économiques de celles-ci est à l’origine de la dégradation du cadre de vie et de travail de la population. Ce constat est valable pour la commune de Bouaflé. En effet, en dépit des efforts réalisés depuis 2013, qui ont permis aux autorités compétentes de recevoir le prix de la commune la plus propre de Côte d’Ivoire en 2017, la difficile gestion de l’espace urbain se pose avec acuité. Cette étude s’appuie sur une analyse de la littérature, des enquêtes de terrain et des entretiens avec des responsables en charge de la gestion urbaine. Les résultats issus de cette étude montrent que la nécessité du passage d’une gestion non participative à une gouvernance urbaine s’impose à Bouaflé. C’est par ailleurs à ce prix que la ville pourra amorcer le processus d’un développement urbain durable.

De nombreuses études de caractérisation des déchets plastiques dans les villes de la Côte d’Ivoire montrent qu’une part de plus en plus importante de ces déchets est par nature potentiellement recyclable. Les filières de recyclage de déchets sont des vecteurs de création d’emplois, nécessitant souvent peu de qualification, pouvant contribuer à la lutte contre la pauvreté dans les classes sociales les plus démunies. Elles contribuent aussi à l’émergence d’une « économie circulaire », où les déchets plastiques peuvent redevenir des ressources possibles pour d’autres acteurs et utilisateurs. Enfin, elles ont également un impact positif sur la gestion des déchets, sur l’environnement urbain et les risques sanitaires induits par leur mauvaise gestion. L’objectif visé par ce présent travail est de montrer comment les déchets plastiques contribuent à la dégradation de l’environnement dans la ville de Boundiali. La recherche documentaire et l’enquête de terrain sont les méthodes retenues pour la collecte de données. Les résultats attendus seront : identifier les types de déchets plastiques et leurs sources de provenance dans la ville de Boundiali ; analyser le mode de gestion de ces déchets plastiques et évaluer les problèmes environnementaux qui découlent de leur mauvaise gestion.

Les villes de Bouaké et de Korhogo sont confrontées à une grave crise de logement décent qui se traduit par un accès difficile à un logement décent. En conséquence, il s’en suit une situation de mal-logement des ménages. Ainsi, cet article analyse les impacts socio-économiques et environnementaux du difficile accès aux logements décents et les stratégies résidentielles des ménages. À travers une méthodologie axée sur la recherche documentaire et l’enquête de terrain (l’observation directe, les entretiens et l’enquête par questionnaire), les résultats montrent, d’abord, que les ménages vivent dans des logements à faible niveau de commodité et surpeuplés (2,27 à Korhogo contre 2,16 à Bouaké). Ensuite, ils révèlent que 33,2% des ménages locataires vivent dans un logement surpeuplé. Enfin, les locataires déploient trois principales stratégies pour la satisfaction d’un droit fondamental. Ce sont les stratégies par connaissance, par substitution et via les agences immobilières.

La commune de Yamoussoukro dispose de plus de 250 ha de forêts, de sous-bois urbains et d’espaces agraires urbains et péri-urbains, parfaitement intégrés à la trame urbaine. La ville dispose également de dix lacs aménagés qui couvrent environ 150 ha. La présence des caïmans introduits dans ces étangs lacustres constitue une attractivité touristique pour les visiteurs. Au nombre des curiosités touristiques de la ville, l’aménagement ou le ré-aménagement touristique du jardin urbain du Guiglo d’une superficie de 105 ha en un seul tenant en plein centre urbain, pourrait être une réelle opportunité pour promouvoir également l’approche écotouristique qui, subsidiairement, contribuera à la satisfaction des Objectifs de Développement Durable (ODD), et offrir un meilleur cadre de vie et un bien-être social à toute la communauté, face aux défis des changements climatiques. La consultation documentaire, couplée à des entretiens directs et semi-directifs avec les personnes ressources sur le terrain ont permis de recueillir des données qui ont fait l’objet d’analyse et de traitement pour appréhender la politique et projet d’aménagement du jardin du Guiglo, les objectifs stratégiques du projet qui reposent sur l’intérêt communautaire et environnemental des espaces verts urbains. Cette approche a permis de saisir la nature des pollutions ainsi que la caractérisation du milieu et des ouvrages qui constituent un préalable à la proposition de solution durable pour la réhabilitation, l’aménagement et la préservation de tout ce patrimoine.

Abstract Assessing volcanic hazards in locations exposed to multiple central volcanoes requires to consider multiple potential eruption sources and their respective characteristics. While this is common practice in ashfall hazard assessment, this is generally not considered for topography-controlled volcanic flow processes. Yet, in volcanic areas with closely spaced volcanic systems, eruptions fed from several contrasted volcanic systems might threaten one given area. Considering the case of the Nyiragongo and Nyamulagira volcanoes in the Virunga Volcanic Province (D.R.Congo), we present a method to produce a combined lava flow inundation susceptibility map that integrates both volcanoes. The spatial distribution of the probability of vent opening for the next eruption is separately constrained for both volcanoes based on the mapping of historical and pre-historical eruptive vents and fissures. The Q-LavHa lava flow probability model is then calibrated separately for each volcano, considering several historical lava flows of Nyamulagira (2004, 2006, 2010) and Nyiragongo (2002). The maps for the two volcanoes are thereafter integrated based on a weighted sum of both individual lava flow inundation probability maps, assuming historically-based relative eruption frequency of the two volcanoes. The accuracy of this probabilistic susceptibility map for the most active volcanic region in Africa was unfortunately validated by the May 2021 lava flow produced by Nyiragongo. This map was discussed and validated in 2019 with local scientists, as well as representatives of disaster management and urban planning institutions, but was not included in the regional contingency plan ahead of the 2021 eruption crisis. Updating the volcanic crisis and evacuation management plans with this lava flow probability map could contribute to reinforce risk awareness among the population and inform the future development of the city of Goma.

Northern latitudes have been significantly impacted by recent climate warming, which has increased the probability of experiencing extreme weather events. To comprehensively understand hydroclimate change and reconstruct hydroclimatic anomalies such as drought periods, appropriate proxy records reaching further back in time beyond meteorological measurements are needed. Here we present a 220-year (2015–1790 CE), continuous, stable oxygen isotope record of diatoms (δ18Odiatom) from Lake Khamra (59.99° N, 112.98° E) in eastern Siberia, an area highly sensitive to climate change and for which there is a demand for palaeohydrological data. This high-resolution proxy record was obtained from a 210Pb–137Cs-dated sediment short core and analysed to reconstruct hydroclimate variability at a sub-decadal scale. The interpretation of the δ18Odiatom record is supported by meteorological data, modern isotope hydrology and geochemical analyses of the same sediment, which is indicative of the conditions in the lake and catchment. A comparison with meteorological data going back to 1930 CE revealed that the δ18Odiatom record of Lake Khamra is primarily influenced by regional precipitation changes rather than the air temperature. We identified winter precipitation, which enters the lake as isotopically depleted snowmelt water, as the key process impacting the diatom isotope variability. We related the overall depletion of δ18Odiatom in recent decades to an observed increase in winter precipitation in the area, likely associated with the global air temperature rise, Arctic sea ice retreat and increased moisture transport inland. Available palaeoclimate proxy records, including a fire reconstruction for the same lake, support the idea that the new record is a valuable hydroclimate proxy that is indicative of precipitation deficits and excludes solar insolation and air temperature as primary driving forces, even before the first meteorological recordings. We propose two possible hydroclimatic anomalies that were detected in the Lake Khamra δ18Odiatom record: one at the beginning of the 19th century and a second prominent event in the 1950s. Both are interpreted as prolonged dry periods associated with enriched δ18Odiatom values likely caused by reduced winter precipitation, which coincide with phases of reconstructed severe wildfires in the region. Despite the apparent pristine lake area, we observed a three- to fourfold increase in mercury concentrations and accumulation rates within the sediment record since the early 20th century, which is partly attributed to human air pollution.

Holocene environmental changes in Patagonia were mostly shaped by fluctuating ice cover recession. Consequently, environmental reconstructions are largely based on discontinuous moraine chronologies from valley deposits. Here, we present a 3 m long continuous sediment record recovered from Laguna Meseta (LME), a lake located on Meseta Chile Chico. Its altitude and location relative to the North Patagonian Icefield provide a unique opportunity to reconstruct the glacial history and related environmental dynamics. Our radiocarbon chronology constrains sedimentation to the last ∼10 000 years and provides a minimum age for postglacial ice-free lacustrine conditions, due to a westward retreat of the ice cap. Lacustrine productivity reached its maximum at the start of the lake phase and decreased afterwards. Between 5500 and 4600 cal yr BP, a major shift towards allochthonous sediment accumulation occurred, caused by an abrupt increase in clastic deposition from basaltic lithologies of the Meseta Chile Chico. This episode correlates with the precipitation-driven Mid-Holocene glacier advance of Patagonian glaciers and suggests that conditions were colder and/or wetter on Meseta Chile Chico at that time. After 4600 cal yr BP, these conditions continued to supply LME with clastic sediments until a stepped decrease around 900 cal yr BP. Thereupon, lacustrine productivity distinctly increased and stabilized around 300 cal yr BP. Our findings indicate that changes in sedimentation on Meseta Chile Chico were mainly controlled by regional variability in the precipitation. Furthermore, strong correlation between our records and available proxies for oscillations of the Southern Hemisphere Westerly Winds suggest a pronounced climatic control by this prominent wind system for central west Patagonia during the last 10 000 years.

Millennial-scale climate variations during the last glacial period, such as Dansgaard–Oeschger (DO) cycles and Heinrich events, have been extensively studied using ice core and marine proxy records. However, there is a limited understanding of the magnitude of these temperature fluctuations in continental regions, and questions remain about the seasonal signal of these climate events. This study presents a 60 000-year-long temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) extracted from lake sediments from the Eifel Volcanic Field, Germany. brGDGTs are bacterial membrane-spanning lipids that are known to have a strong relationship with temperature, making them suitable for temperature reconstructions. We test several temperature calibration models on modern samples taken from soils and multiple maar lakes. We find a negative bias in brGDGT-based temperature estimates associated with water depth and anoxic conditions that can be corrected for by accounting for a brGDGT isomer that is only produced in anoxic conditions. The corrected temperature reconstruction correlates with proxy and climate model estimates of temperature spanning the same time period, validating the calibration approach we selected. However, millennial-scale variability is significantly dampened in the brGDGT record, and in contrast to other Northern Hemisphere climate records, during several Heinrich stadials, temperatures actually increase. We demonstrate that these apparent discrepancies can be explained by the unique seasonal response of the brGDGT paleothermometer to temperatures of months above freezing (TMAF). Our data support the view that warm-season temperatures in Europe varied minimally during the last glacial period and that abrupt millennial-scale events were defined by colder, longer winters. Our continuous high-resolution temperature reconstruction provides important information about the magnitude of seasonal climate variability during the last glacial period that can be used to test climate models and inform studies of paleoecological change.

An increasing number of climate model simulations is becoming available for the transition from the Last Glacial Maximum to the Holocene. Assessing the simulations' reliability requires benchmarking against environmental proxy records. To date, no established method exists to compare these two data sources in space and time over a period with changing background conditions. Here, we develop a new algorithm to rank simulations according to their deviation from reconstructed magnitudes and temporal patterns of orbital and millennial-scale temperature variations. The use of proxy forward modeling allows for accounting for non-climatic processes that affect the temperature reconstructions. It further avoids the need to reconstruct gridded fields or regional mean temperature time series from sparse and uncertain proxy data. First, we test the reliability and robustness of our algorithm in idealized experiments with prescribed deglacial temperature histories. We quantify the influence of limited temporal resolution, chronological uncertainties, and non-climatic processes by constructing noisy pseudo-proxies. While model–data comparison results become less reliable with increasing uncertainties, we find that the algorithm discriminates well between simulations under realistic non-climatic noise levels. To obtain reliable and robust rankings, we advise spatial averaging of the results for individual proxy records. Second, we demonstrate our method by quantifying the deviations between an ensemble of transient deglacial simulations and a global compilation of sea surface temperature reconstructions. The ranking of the simulations differs substantially between the considered regions and timescales, which suggests that optimizing for agreement with the temporal patterns of a small set of proxies might be insufficient for capturing the spatial structure of the deglacial temperature variability. We attribute the diversity in the rankings to more regionally confined temperature variations in reconstructions than in simulations, which could be the result of uncertainties in boundary conditions, shortcomings in models, or regionally varying characteristics of reconstructions such as recording seasons and depths. Future work towards disentangling these potential reasons can leverage the flexible design of our algorithm and its demonstrated ability to identify varying levels of model–data agreement. Additionally, the algorithm can be applied to variables like oxygen isotopes and climate transitions such as the penultimate deglaciation and the last glacial inception.

The last deglaciation (∼20–11 ka BP) is a period of a major, long-term climate transition from a glacial to interglacial state that features multiple centennial- to decadal-scale abrupt climate variations whose root cause is still not fully understood. To better understand this time period, the Paleoclimate Modelling Intercomparison Project (PMIP) has provided a framework for an internationally coordinated endeavour in simulating the last deglaciation whilst encompassing a broad range of models. Here, we present a multi-model intercomparison of 17 transient simulations of the early part of the last deglaciation (∼20–15 ka BP) from nine different climate models spanning a range of model complexities and uncertain boundary conditions and forcings. The numerous simulations available provide the opportunity to better understand the chain of events and mechanisms of climate changes between 20 and 15 ka BP and our collective ability to simulate them. We conclude that the amount of freshwater forcing and whether it follows the ice sheet reconstruction or induces an inferred Atlantic meridional overturning circulation (AMOC) history, heavily impacts the deglacial climate evolution for each simulation rather than differences in the model physics. The course of the deglaciation is consistent between simulations except when the freshwater forcing is above 0.1 Sv – at least 70 % of the simulations agree that there is warming by 15 ka BP in most places excluding the location of meltwater input. For simulations with freshwater forcings that exceed 0.1 Sv from 18 ka BP, warming is delayed in the North Atlantic and surface air temperature correlations with AMOC strength are much higher. However, we find that the state of the AMOC coming out of the Last Glacial Maximum (LGM) also plays a key role in the AMOC sensitivity to model forcings. In addition, we show that the response of each model to the chosen meltwater scenario depends largely on the sensitivity of the model to the freshwater forcing and other aspects of the experimental design (e.g. CO2 forcing or ice sheet reconstruction). The results provide insight into the ability of our models to simulate the first part of the deglaciation and how choices between uncertain boundary conditions and forcings, with a focus on freshwater fluxes, can impact model outputs. We can use these findings as helpful insight in the design of future simulations of this time period.

Abstract Learning is to use algorithms to enable machines to learn rules from a large amount of historical data, so as to intelligently identify new samples or predict the future. Deep learning can promote students’ understanding of knowledge, conduct in-depth processing of new knowledge, integrate it with the original knowledge, and apply it to new situations, solve intelligent audio–visual listening from the perspective of deep learning, and focus on cultivating students’ in-depth learning ability and individual differences in innovative thinking. As the main position of ecological education, schools should effectively strengthen the publicity and education of ecological ideas and low-carbon concepts, and integrate them into education and teaching to effectively improve students’ awareness of environmental protection. This study aims to explore the effectiveness of flipped classroom teaching model based on deep learning. Therefore, from the perspective of deep learning, this paper combs the theory of deep learning, constructs a new model of smart classroom, and provides ideas and directions for model reform. In this study, the flipped classroom teaching model based on deep learning was applied to English teaching, and an 8-week teaching experiment was conducted. In addition, this paper believes that it is of great practical significance to carry out environmental protection education with the help of English teaching.

Global surface air temperature increased by ca. 0.5 °C from the 1900s to the mid-1940s, also known as Early 20th Century Warming (ETCW). However, the ETCW started from a particularly cold phase, peaking in 1908–1911. The cold phase was global but more pronounced in the Southern Hemisphere than in the Northern Hemisphere and most pronounced in the Southern Ocean, raising the question of whether uncertainties in the data might play a role. Here we analyse this period based on reanalysis data and reconstructions, complemented with newly digitised ship data from 1903–1916, as well as land observations. The cooling is seen consistently in different data sets, though with some differences. Results suggest that the cooling was related to a La-Niña-like pattern in the Pacific, a cold tropical and subtropical South Atlantic, a cold extratropical South Pacific, and cool southern midlatitude land areas. The Southern Annular Mode was positive, with a strengthened Amundsen–Bellingshausen seas low, although the spread of the data products is considerable. All results point to a real climatic phenomenon as the cause of this anomaly and not a data artefact. Atmospheric model simulations are able to reproduce temperature and pressure patterns, consistent with a real and perhaps ocean-forced signal. Together with two volcanic eruptions just before and after the 1908–1911 period, the early 1900s provided a cold start into the ETCW.

Atmospheric carbon dioxide concentration (pCO2) has increased by approximately 80 ppm from the Last Glacial Maximum (LGM) to the early Holocene. The change in this atmospheric greenhouse gas is recognized as a climate system response to gradual change in insolation. Previous modeling studies suggested that the deglacial increase in atmospheric pCO2 is primarily attributed to the release of CO2 from the ocean. Additionally, it has been suggested that abrupt change in the Atlantic meridional overturning circulation (AMOC) and associated interhemispheric climate changes are involved in the release of CO2. However, understanding remains limited regarding oceanic circulation changes and the factors responsible for changes in chemical tracers in the ocean during the last deglaciation and their impact on atmospheric pCO2. In this study, we investigate the evolution of the ocean carbon cycle during the last deglaciation (21 to 11 ka BP) using three-dimensional ocean fields from the transient simulation of the MIROC 4m climate model, which exhibits abrupt AMOC changes similar to those observed in reconstructions. We investigate the reliability of simulated changes in the ocean carbon cycle by comparing the simulated carbon isotope ratios with sediment core data, and we examine potential biases and overlooked or underestimated processes in the model. Qualitatively, the modeled changes in atmospheric pCO2 are consistent with ice core records. For example, during Heinrich Stadial 1 (HS1), atmospheric pCO2 increases by 10.2 ppm, followed by a reduction of 7.0 ppm during the Bølling–Allerød (BA) period and then by an increase of 6.8 ppm during the Younger Dryas (YD) period. However, the model underestimates the changes in atmospheric pCO2 during these events compared to values derived from ice core data. Radiocarbon and stable isotope signatures (Δ14C and δ13C) indicate that the model underestimates both the activated deep-ocean ventilation and reduced efficiency of biological carbon export in the Southern Ocean and the active ventilation in the North Pacific Intermediate Water (NPIW) during HS1. The relatively small changes in simulated atmospheric pCO2 during HS1 might be attributable to these underestimations of ocean circulation variation. The changes in Δ14C associated with strengthening and weakening of the AMOC during the BA and YD periods are generally consistent with values derived from sediment core records. However, although the data indicate continuous increase in δ13C in the deep ocean throughout the YD period, the model shows the opposite trend. It suggests that the model either simulates excessive weakening of the AMOC during the YD period or has limited representation of geochemical processes, including marine ecosystem response and terrestrial carbon storage. Decomposing the factors behind the changes in ocean pCO2 reveals that variations in temperature and alkalinity have the greatest impact on change in atmospheric pCO2. Compensation for the effects of temperature and alkalinity suggests that the AMOC changes and the associated bipolar climate changes contribute to the decrease in atmospheric pCO2 during the BA and the increase in atmospheric pCO2 during the YD period.

The main aim of the study was to assess the feasibility of using biopolymers of different viscosities (high, medium and low viscosity) as immobilization carriers for laccase in synthetic dye removal. The following dye solutions were decolorized: indigo carmine (IC, anionic dye), methylene blue (MB, cationic dye), and their mixture in a molar mass ratio MB/IC=0.69, using biopolymers of different viscosities as laccase immobilization carriers. Toxicity tests were also carried out to assess the toxicity of the post-decolorization samples. Decolorization tests showed that the main decolorization mechanism depends on the dye class. The removal of IC (max. total removal efficiency 72.15%) was mainly by biocatalysis. The mechanism of the MB decolorization process was mainly by sorption on alginate beads, and the efficiency of enzymatic removal was low. However, the highest efficiency of MB decolorization (45.80%) was obtained for beads prepared using the high viscosity alginate when decolorization occurred by both sorption and biocatalysis. The results of mixture decolorization tests differ from the results obtained for single dyes.The results showed differences in the efficiency of the dye sorption process depending on the alginate used for immobilization. Moreover, the varying mechanisms of dye removal from the dye mixture were confirmed by toxicity tests. The occurrence of both biocatalysis and sorption promotes reduced toxicity

There are approximately 15 million users of system heat in Poland, but unfortunately nearly 70% of the fuel used in heat production is fossil fuel. Therefore, the CO2 emission reduction in the heat production industry is becoming one of the key challenges. City Heat Distribution Enterprise Ltd. in Nowy Sącz (Miejskie Przedsiębiorstwo Energetyki Cieplnej sp. z o.o.) has been conducting a self-financed research and development project entitled The use of algae as carbon dioxide absorbers at MPEC Nowy Sącz. The project deals with postcombustion CO2 capture using Chlorella vulgaris algae. As a result of tests conducted in a 1000 l hermetic container under optimal temperature and light conditions, the recovery of biomass can be performed in weekly cycles, yielding approximately 25 kilograms of biomass per year. Assuming that half of the dry mass of the algae is carbon, it can be said that 240 grams of carbon is bound in one cycle, which, converted to CO2, gives 880 grams of this gas. Our results showed that around 45.8 kilograms of CO2 per year was absorbed. Additionally, it is possible to use waste materials and by-products of technological processes as a nutrient medium for algae