Plastic pollution in marine environments is a severe problem in the world due to misuse and mismanagement of the materials. Microplastics are a specific form of pollutants in this context and its handling is very difficult due to its very small size of particulates. Currently, the impacts of marine plastic debris are not considered. However, this type of particulates can be assessed like other emissions with the systematic and quantifiable approach in life cycle assessment (LCA). It was our goal to find and test first methodological approaches for including impacts of marine litter of microplastics to LCA. The Medellin Declaration on Marine Litter in Life Cycle Assessment and Management raised this issue in 2017 and called for LCA to address the challenges of marine litter. The present research paper focuses on how to integrate plastic debris impacts with focus on microplastics into LCA and gives a suggestion for an assessment approach. Based on a literature review, we considered various impacts to the marine environment of microplastics linked with their kinetics of the fragmentation and degradation. Subsequently, we developed a characterization LCA model for microplastics in the marine environment. We addressed therein the fate of microplastics and their specific eco-toxic effects to different organisms. We compared the impacts of different types of polymers as well and showed how these can be integrated in an assessment using the new characterization model. The assessment of marine litter impacts in LCA was strongly dependent on the number of microplastic particles produced from the original litter over time. These impacts were derived from measurements of the number of microparticles, their densities in the marine environment and their impacts to different organisms. The new characterization model includes the relationship between fragmentation and degradation and can be used for impact assessments within LCA. The question where we did not find a finally satisfying solution is the issue of the length of the time horizon of the assessment or the discounting. Those are regarded as subjective and are encountered with sensitivity or scenario analysis. Results from different time horizons can be aggregated to one figure or can be compared separately. Further investigations should be taken for a better understanding of this issue and for concrete solutions because their influence on the results of life cycle assessments is often fundamental.

中文翻译：

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微塑料作为海洋塑料垃圾的一个组成部分的生命周期影响评估

由于材料的滥用和管理不善，海洋环境中的塑料污染是世界上的一个严重问题。在这种情况下，微塑料是一种特殊形式的污染物，由于其颗粒尺寸非常小，因此处理起来非常困难。目前，没有考虑海洋塑料垃圾的影响。然而，这种类型的颗粒物可以像其他排放物一样通过生命周期评估 (LCA) 中的系统和可量化方法进行评估。我们的目标是找到并测试第一个方法论方法，以将微塑料的海洋垃圾对 LCA 的影响包括在内。生命周期评估和管理中的海洋垃圾麦德林宣言在 2017 年提出了这个问题，并呼吁 LCA 应对海洋垃圾的挑战。本研究论文侧重于如何将塑料碎片影响与微塑料结合到 LCA 中，并为评估方法提出建议。根据文献综述，我们考虑了微塑料对海洋环境的各种影响，与它们的破碎和降解动力学有关。随后，我们开发了海洋环境中微塑料的表征 LCA 模型。我们在其中讨论了微塑料的命运及其对不同生物的特定生态毒性影响。我们还比较了不同类型聚合物的影响，并展示了如何使用新的表征模型将这些影响整合到评估中。LCA 中海洋垃圾影响的评估在很大程度上取决于原始垃圾随时间产生的微塑料颗粒的数量。这些影响源自对微粒数量、它们在海洋环境中的密度及其对不同生物的影响的测量结果。新的表征模型包括破碎和退化之间的关系，可用于 LCA 内的影响评估。我们没有找到最终令人满意的解决方案的问题是评估或贴现的时间范围的长度问题。这些被认为是主观的，会遇到敏感性或情景分析。来自不同时间范围的结果可以汇总为一个数字，也可以分别进行比较。应该进行进一步调查以更好地理解这个问题并找到具体的解决方案，因为它们对生命周期评估结果的影响通常是根本性的。