Global Patterns and Regional Remote-Sensing Monitoring of Microplastic Pollution in Freshwater-Ocean Systems (2014-2024).

Microplastics are widely detected in rivers, lakes, and oceans, yet global-scale assessments remain constrained by uneven monitoring coverage, inconsistent reporting units, and limited integration of particle attributes with spatial and temporal analyses. Here, we compiled 6464 georeferenced water-sample concentration records from 2014 to 2024 by integrating Web of Science-indexed studies with compatible records from NOAA NCEI and Adventure Scientists; 1469 sampling sites also contained particle-attribute information. We characterized spatial heterogeneity, regional contrasts, particle composition, nonlinear dynamics, and remote-sensing-assisted hotspot mapping. Sampling records clustered in North America, Europe, East Asia, South Asia, and the midlatitude Northern Hemisphere. River records showed the highest central concentrations, followed by lakes, whereas ocean records had lower medians but distinct local hotspots. Fibers dominated river and lake MPs, while marine records contained higher proportions of fragments and particles. Spearman's tests showed no significant monotonic trends in annual median concentrations, but long short-term memory reproduced river and ocean dynamics well (R2 = 0.971 and 0.962) and indicated divergent Sen-slope directions, with rivers decreasing and lakes, oceans, and pooled global records increasing. Remote-sensing-assisted mapping identified nearshore, estuarine, bay, and hydrodynamically confined zones as microplastic accumulation areas. This framework supports monitoring prioritization, targeted sampling, ecological risk assessment, and coordinated freshwater-ocean governance.