Plastic bags are currently a major component of marine litter, causing aesthetical nuisance, and undesirable effects on marine fauna that ingest them or are entangled. Plastic litter also rises concern on the ecotoxicological effects due to the potential toxicity of the chemical additives leached in aquatic environments. Conventional plastic bags are made of polyethylene, either from first use or recycled, but regulations restricting single-use plastics and limiting lightweight carrier bags (<50 μm thickness) have fostered the replacement of thin PE bags by compostable materials advertised as safer for the environment. In this study, we assess the degradation of commercially available plastic bags in marine conditions at two scales: aquariums (60 days) and outdoors flow-through mesocosm (120 days). Strength at break point and other tensile strength parameters were used as ecologically relevant endpoints to track mechanical degradation. Ecotoxicity has been assessed along the incubation period using the sensitive embryo test. Whereas PE bags did not substantially lose their mechanical properties within the 60 d aquarium exposures, compostable bags showed remarkable weight loss and tensile strength decay, some of them fragmenting in the aquarium after 3–4 weeks. Sediment pore water inoculum promoted a more rapid degradation of compostable bags, while nutrient addition pattern did not affect the degradation rate. Longer-term mesocosms exposures supported these findings, as well as pointed out the influence of the microbial processes on the degradation efficiency of compostable/bioplastic bags. Compostable materials, in contrast toPE, showed moderate toxicity on sea-urchin larvae, partially associated to degradation of these materials, but the environmental implications of these findings remain to be assessed. These methods proved to be useful to classify plastic materials, according to their degradability in marine conditions, in a remarkably shorter time than current standard tests and promote new materials safer for the marine fauna.

中文翻译：

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传统塑料袋、回收塑料袋和可堆肥塑料袋的海洋降解和生态毒性


塑料袋目前是海洋垃圾的主要组成部分，会造成美观问题，并对摄入或缠绕塑料袋的海洋动物产生不良影响。由于水生环境中浸出的化学添加剂具有潜在毒性，塑料垃圾的生态毒理学效应也引起了人们的关注。传统的塑料袋由聚乙烯制成，无论是首次使用的还是回收的，但限制一次性塑料和限制轻型手提袋（厚度<50微米）的法规促进了可堆肥材料取代薄聚乙烯袋，宣传为对环境更安全。在这项研究中，我们在两个尺度的海洋条件下评估了市售塑料袋的降解情况：水族馆（60 天）和户外流水环境（120 天）。断裂点强度和其他拉伸强度参数被用作生态相关终点来跟踪机械降解。使用敏感胚胎测试评估了整个潜伏期的生态毒性。 PE 袋在水族箱中暴露 60 天后，其机械性能并未大幅丧失，而可堆肥袋则表现出显着的重量损失和拉伸强度衰减，其中一些袋在水族箱中放置 3-4 周后就会碎裂。沉积物孔隙水接种促进了可堆肥袋更快的降解，而养分添加模式并不影响降解速率。长期的中生态环境暴露支持了这些发现，并指出了微生物过程对可堆肥/生物塑料袋降解效率的影响。 与PE相反，可堆肥材料对海胆幼虫表现出中等毒性，部分与这些材料的降解有关，但这些发现的环境影响仍有待评估。事实证明，这些方法可根据塑料材料在海洋条件下的降解性对塑料材料进行分类，其时间明显短于当前标准测试的时间，并促进新材料对海洋动物更安全。