摘要 :
During the processing and during their lifetime, polymers are subjected to several environmental stresses—thermomechanical, photo-oxidative, etc.—that can strongly modify their chemical and molecular structure and, consequently,...
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During the processing and during their lifetime, polymers are subjected to several environmental stresses—thermomechanical, photo-oxidative, etc.—that can strongly modify their chemical and molecular structure and, consequently, their morphology. Reduction of the molecular weight and formation of double bonds and oxygenated groups are the main changes observed as a consequence of the degradation. As a result of these changes, the macroscopic properties are dramatically modified. These changes can have a relevant effect if the post-consumer plastic manufacts are recycled. In this work, a sample of polypropylene subjected to two different degradation histories—photo-oxidation in air and in marine water—is reprocessed two times in a mini twin-screw extruder in the same processing conditions. The effect of the thermomechanical degradation during the reprocessing is different. Indeed, the less severe degraded sample shows a higher degradation level during reprocessing because the shear stress is larger. This means that the thermomechanical degradation kinetics is larger in the less degraded samples. Nevertheless, the final properties of the recycled polymers are different because the properties of the photo-oxidized samples before reprocessing were very different.
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The usage of sails is increasing parallel to the sustainability initiatives in marine transportation not only for recreational craft but also for large vessels carrying commercial goods and passengers. In this study, the marine en...
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The usage of sails is increasing parallel to the sustainability initiatives in marine transportation not only for recreational craft but also for large vessels carrying commercial goods and passengers. In this study, the marine environmental degradation of the sailcloth which significantly shortens the lifetime of these materials was investigated experimentally. Dacrons, which are relatively cheap, easy to form, and resistant to breakdown, but problematic to keeping their original shape while subjected to wind loads, were selected as the sailcloth. The combined effect of seawater exposure, temperature, UV, wet-dry cycle, water repellent treatment on the Dacron's mechanical performance was measured by tensile tests performed for the Dacron specimens with nine different areal weights and in two different fibre directions (warp and weft) and by dynamical mechanical analysis for a representative Dacron sailcloth. The comparative results show that the marine environment has significant degradation effects on the mechanical performance of sailcloths.
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Abstract Aegagropiles are conglomerations of fibre debris from Posidonia oceanica meadows that are frequently found along Mediterranean beaches, but the plant organ from which these fibres arise remains unknown. In this study, a h...
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Abstract Aegagropiles are conglomerations of fibre debris from Posidonia oceanica meadows that are frequently found along Mediterranean beaches, but the plant organ from which these fibres arise remains unknown. In this study, a histological comparison of P. oceanica organs from 3 shoots with the structure of aegagropile fibres showed that most of them arise from leaf sheaths and rhizomes, suggesting that they are degradation products from the “matte” rather than from the leaf litter, which is mainly composed of detached leaf blades. Moreover, fungal hyphae, micro-sclerotia and typical degradation traces were found in the peripheral tissues of living P. oceanica organs, as well as in degrading aegagropiles. We assume, by comparing Vohník’s observations and the observations made in this study, that these endophytic fungi and degradation traces might be attributed to a dark septate endophyte (DSE) in the Aigialaceae (Pleosporales), Posidoniomyces atricolor, which was recently described as an endosymbiont in P. oceanica roots. It constitutes one of the most important microorganisms by abundance that degrade P. oceanica tissues within the matte and give rise to the different fibre types in aegagropiles. This study shows that the proliferation of fungi causes organ degradation in Posidonia, starting early in living P. oceanica plants, continuing in the matte and, probably, in the leaf litter. The DSE plays a much more important role than that of a simple plant endosymbiont; its omnipresence within P. oceanica (and the degradation of the middle lamella and cell death during proliferation) causing the degradation of various Posidonia organs also contributes to the enrichment of the ‘matte’ compartment of this ecosystem, notably favouring nitrogen retention in its chitinous walls.
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Extreme heat wave events are now causing ecosystem degradation across marine ecosystems. The consequences of this heat‐induced damage range from the rapid loss of habitat‐forming organisms, through to a
Extreme heat wave events are now causing ecosystem degradation across marine ecosystems. The consequences of this heat‐induced damage range from the rapid loss of habitat‐forming organisms, through to a reduction in the services that ecosystems support, and ultimately to impacts on human health and society. How we tackle the sudden emergence of ecosystem‐wide degradation has not yet been addressed in the context of marine heat waves. An examination of recent marine heat waves from around Australia points to the potential important role that respite or refuge from environmental extremes can play in enabling organismal survival. However, most ecological interventions are being devised with a target of mid to late‐century implementation, at which time many of the ecosystems, that the interventions are targeted towards, will have already undergone repeated and widespread heat wave induced degradation. Here, our assessment of the merits of proposed ecological interventions, across a spectrum of approaches, to counter marine environmental extremes, reveals a lack preparedness to counter the effects of extreme conditions on marine ecosystems. The ecological influence of these extremes are projected to continue to impact marine ecosystems in the coming years, long before these interventions can be developed. Our assessment reveals that approaches which are technologically ready and likely to be socially acceptable are locally deployable only, whereas those which are scalable—for example to features as large as major reef systems—are not close to being testable, and are unlikely to obtain social licence for deployment. Knowledge of the environmental timescales for survival of extremes, via respite or refuge, inferred from field observations will help test such intervention tools. The growing frequency of extreme events such as marine heat waves increases the urgency to consider mitigation and intervention tools that support organismal and ecosystem survival in the immediate future, while global climate mitigation and/or intervention are formulated.
摘要 :
Extreme heat wave events are now causing ecosystem degradation across marine ecosystems. The consequences of this heat-induced damage range from the rapid loss of habitat-forming organisms, through to a reduction in the services t...
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Extreme heat wave events are now causing ecosystem degradation across marine ecosystems. The consequences of this heat-induced damage range from the rapid loss of habitat-forming organisms, through to a reduction in the services that ecosystems support, and ultimately to impacts on human health and society. How we tackle the sudden emergence of ecosystem-wide degradation has not yet been addressed in the context of marine heat waves. An examination of recent marine heat waves from around Australia points to the potential important role that respite or refuge from environmental extremes can play in enabling organismal survival. However, most ecological interventions are being devised with a target of mid to late-century implementation, at which time many of the ecosystems, that the interventions are targeted towards, will have already undergone repeated and widespread heat wave induced degradation. Here, our assessment of the merits of proposed ecological interventions, across a spectrum of approaches, to counter marine environmental extremes, reveals a lack preparedness to counter the effects of extreme conditions on marine ecosystems. The ecological influence of these extremes are projected to continue to impact marine ecosystems in the coming years, long before these interventions can be developed. Our assessment reveals that approaches which are technologically ready and likely to be socially acceptable are locally deployable only, whereas those which are scalable-for example to features as large as major reef systems-are not close to being testable, and are unlikely to obtain social licence for deployment. Knowledge of the environmental timescales for survival of extremes, via respite or refuge, inferred from field observations will help test such intervention tools. The growing frequency of extreme events such as marine heat waves increases the urgency to consider mitigation and intervention tools that support organismal and ecosystem survival in the immediate future, while global climate mitigation and/or intervention are formulated.
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Polypropylene (PP) pellets exposed to solar radiation, ultraviolet B (UVB) radiation and heat in four stimulated treatments: dry-air, seawater-air, seawater-darkness, and dry-darkness for 0.5-1.5 years to investigate morphology an...
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Polypropylene (PP) pellets exposed to solar radiation, ultraviolet B (UVB) radiation and heat in four stimulated treatments: dry-air, seawater-air, seawater-darkness, and dry-darkness for 0.5-1.5 years to investigate morphology and chemical change under various environmental conditions. Scanning electron microscopy and infrared spectroscopy were employed to characterize the virgin and degraded pellets. The degraded PP pellets under solar and UVB irradiation revealed 35% and 12% cracks, respectively. Moreover, carbonyl and hydroxyl groups formed on the surface gradually extended to the interior. However, under photo-irradiation, PP pellets floating in seawater showed less degradation than those in a dry environment. The formation of biofilm may retard the photo-degradation of PP pellets in the seawater when biocides are absent. Results also indicated that the photo oxidation dominated over thermal oxidation during the degradation process in the terrestrial and marine environments.
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Polyvinyl chloride (PVC) is the third one after polyethylene and polypropylene in the production demand. It intends to grow further, causing an increase in the risk of health and ecological problems due to environmental accumulati...
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Polyvinyl chloride (PVC) is the third one after polyethylene and polypropylene in the production demand. It intends to grow further, causing an increase in the risk of health and ecological problems due to environmental accumulation and incineration. In the present study, we determined the biodegradative abilities of marine bacteria for PVC. Three potential marine bacterial isolates, T-1.3, BP-4.3 and S-237 (Vibrio, Altermonas and Cobetia, respectively) were identified after preliminary screening. They led to active biofilm formation, viability and protein formation on the PVC surface. The highest weight loss (1.76%) of PVC films was exhibited by BP-4.3 isolate after 60 days of incubation. Remineralization of PVC film was confirmed by CO2 assimilation assay. Change in surface topography was confirmed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The functional group peak intensity was decreased for the terminal chlorine group at the region 1000-1300 cm(-1), which indicated the dechlorination. Thermogravimetric, tensile strength and contact angle analysis showed a decline in the mechanical properties and a rise in PVC film's hydrophilic nature after biodegradation. These results demonstrated promising evidence of PVC degradation by marine bacteria.
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Marine plastic pollution is a worldwide challenge making new progress in the field of degradable polymers necessary. However, it is difficult for commercial biodegradable polymers, such as polylactide (PLA), to realize rapid degra...
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Marine plastic pollution is a worldwide challenge making new progress in the field of degradable polymers necessary. However, it is difficult for commercial biodegradable polymers, such as polylactide (PLA), to realize rapid degradation in seawater by simply blending modification. Here, we prepared a novel series of poly(butylene diglycolate/terephthalate) (PBDT) copolymers by introducing diglycolic acid into PBT. The proposed polyesters can serve as an eco-friendly substitute for existing packaging materials. The mechanical property of PBDTs, with high tensile strength (>23.4 MPa) and elastic modulus (95-610 MPa), had advantages compared with commercial degradable polymers. The hydrophilicity is enhanced with ether bonds of butylene diglycolate (BD) segments. And the hydrolysis of copolymers was accelerated in seawater, showing 16% weight loss after 30 days. Moreover, PBDTs with BD segments > 20% performed great degradability in Phosphate Buffered Saline and enzymatic solution. And their degradation mechanism was monitored through various tests such as ~1H NMR, SEM and GPC. With a small number of antibacterial agents, such as 8% mass fraction of chitosan nanoparticles (CHNPs) or 1.0% of Ag@AgCl, PBDT composites could obtain good antibacterial ability for Gram-negative Escherichia coli without sacrificing the thermal, mechanical properties of the parent PBDT50. This work provides insights and direction for the development of seawater degradable polymers and thereby is able to relieve additional marine pollution in the future.
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Economic, social and ecological development are seriously impeded by the deterioration of the environment - which creates detrimental effects on people's livelihoods as well as natural resources management. This study aims to expl...
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Economic, social and ecological development are seriously impeded by the deterioration of the environment - which creates detrimental effects on people's livelihoods as well as natural resources management. This study aims to explore the predominant factors affecting natural resources management within marine protected areas (MPAs) and the impact of said factors. The data was collected using a survey questionnaire through face to face interaction with respondents. The structural equation model (SEM) was employed to analyse the collected data. The study found that economic, social, cultural and ecological development factors have a significant influence on "sustainable use of natural resources". By contrast, political and technological development does not have any significant relationship with sustainable use of natural resources. This might be because MPAs are not politically and technologically developed yet according to community expectations. Therefore, this study will propose some directives for policymakers to accelerate economic, social, cultural and ecological development - as well as to increase sustainability awareness and form favourable environmental attitudes among marine park communities to promote natural resource management.
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Epoxy resin samples were cyclically exposed to ultraviolet A (UVA) and a 5 wt% salt solution in a specially designed marine environment simulation system. Surface analyses indicated that UVA irradiation could accelerate the degrad...
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Epoxy resin samples were cyclically exposed to ultraviolet A (UVA) and a 5 wt% salt solution in a specially designed marine environment simulation system. Surface analyses indicated that UVA irradiation could accelerate the degradation of the epoxy surface and the dissolution of the degraded products, while the salt crystallization in the drying process could further accelerate the chalking and peeling of the degraded products. A possible synergistic effect between the UVA irradiation and salt crystallization was proposed to interpret the degradation, which may provide a new insight into the damage of organic polymer materials in marine environments.
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