Is it fate? Quantifying the probabilities of mismanaged macroplastics reaching the ocean within the Life Cycle Assessment framework

Plastic pollution is a major issue in marine ecosystems. Plastic items can easily be mismanaged or littered at the end-of-life, but leakage to the environment happens throughout the life cycle of any product containing plastic. The leaked and littered plastic particles can be of any shape and size, usually distinguished into micro- (smaller than 5 mm) and macroplastics (larger than 5 mm). With the ongoing, and soon to be concluded, plastic treaty, solutions and actions are required to reduce and hopefully stop macroplastics entering aquatics environment. As macroplastics are one of the major sources of microplastics through fragmentation, microplastics would be consequently reduced.To be able to assess the magnitude of impacts from plastic pollution, we need tools that can address multiple impacts across value chains. One such tool used for decision-making is Life Cycle Assessments which can help by evaluating and comparing similar products for informing the best suitable solutions. However, plastic pollution is currently not well covered in the framework. Recently, Life Cycle Impact Assessments (LCIA) models that assess impacts from plastics that are released directly to the ocean have been developed. Although work has been done on certain impact pathways, most notably for microplastics, fate modeling, describing how plastic is transported through the environment, still needs to be improved and expanded to fill the methodological Fate Factors (FF) gaps in LCIA. One particular need is to cover how macroplastic from land-based activities will be mismanaged (MPW), transported to, and affect different marine ecosystems through environmental and hydrological processes.Through existing conceptual and probabilistic observations-based models, our approach consists of quantifying novel FF for LCIA use. The FFs have global coverage while being regionalized per water basin. We quantify the fate of macroplastic items, by including the influence of environmental factors, such as wind, runoff, and land use. These factors affect the mobilization, transport, and accumulation of plastics pollution from land into marine environments. Transport on land is modeled based on the conceptual framework of the Plastic Pathfinder1 using grid cells-based movement with respect to environmental factors and mapping the plastics mobilization and accumulation on the coasts or in in rivers. Once plastics have reached a river, this portion of MPW is then multiplied by the probabilities of a river to release plastics in the ocean based on observations, discharge, and Strahler order from Meijer et al. (2021)2. FFs can be used to update existing LCIA models which will help accounting and assessing the regional and global impacts of plastic pollution from land to sea in marine environments ultimately improving decision making. _____ (1) Mellink, Y.; van Emmerik, T.; Kooi, M.; Laufkötter, C.; Niemann, H. The Plastic Pathfinder: A Macroplastic Transport and Fate Model for Terrestrial Environments. Front. Environ. Sci. 2022, 10. https://doi.org/10.3389/fenvs.2022.979685.(2) Meijer, L. J. J.; Van Emmerik, T.; Van Der Ent, R.; Schmidt, C.; Lebreton, L. More than 1000 Rivers Account for 80% of Global Riverine Plastic Emissions into the Ocean. Sci. Adv. 2021, 7 (18), eaaz5803. https://doi.org/10.1126/sciadv.aaz5803.