A Global Basin-Delineated Model of Macroplastic Distribution from Land to Aquatic Environments

Plastic pollution is a global challenge, yet life cycle impact assessment (LCIA) methods lack spatially explicit transfer coefficients to quantify macroplastics distribution between terrestrial and aquatic environments. Current LCIA models focus on marine impacts, leaving terrestrial and inland aquatic pathways poorly characterized and limiting the integration of land-based plastic emissions into environmental assessment frameworks. Here, we present the Global Plastic Distribution Model (GPDM), the first global, basin-delineated model generating LCIA-compatible macroplastic transfer coefficients across terrestrial and freshwater compartments. GPDM simulates macroplastic mobilization driven by wind and surface runoff on 0.01° × 0.01° grids across 285 hydrological basins over 10 years. Results reveal that, on average, 73 ± 1% of terrestrial plastic emissions remain on land (dominated by grass/shrubland: 24 ± 3% and forests: 21 ± 2%), while 20 ± 5% reach rivers and 0.19 ± 18% accumulate in lakes. Coupling GPDM coefficients with a global mismanaged plastic waste inventory reveals geographic hotspots and priority regions for future regionalized characterization factors. While South and Southeast Asian countries contribute disproportionately to riverine plastic distribution, rankings vary substantially across environments. A two km coastal buffer further identified shoreline-adjacent accumulation hotspots. The spatially explicit transfer coefficients enable basin-resolved fate factors in LCIA, advancing macroplastic impact quantification beyond marine-focused models. Comparison with previous assessments indicates broadly consistent freshwater estimates but greater terrestrial and coastal retention, reinforcing land as a major, often overlooked, plastic sink. GPDM provides a foundation for regionalized fate and characterization factors across interconnected terrestrial and freshwater systems.