Modeling Microplastic Emission, Transport, and Spatial Dispersion in the Pearl River Delta Using a Simplified One-Dimensional Framework

Microplastic pollution has become an increasingly critical environmental issue in large river-delta systems, yet quantitative modeling of its regional emission and downstream transport remains limited. This study develops and implements a simplified steady-state model to simulate the emission, transport, and spatial expansion of microplastics in the Pearl River Delta (PRD), China. Through rigorous mathematical modeling and data analysis, the research reveals distinct spatial patterns of microplastic concentration along the PRD transect. The results demonstrate that concentrations increase dramatically in the upstream Guangzhou urban reaches, achieving a maximum concentration of 28,729 items/m3 at Tianhe. These elevated levels persist through the Huangpu and Panyu regions before showing a gradual decline toward the estuarine section. Notably, the model's predicted concentration at Nanshan (9,002 items/m3) closely aligns with previously reported average levels for the Pearl River estuary, validating the model's accuracy in capturing both magnitude and longitudinal trends. Further analysis of the relationship between concentration hotspots and source-emission hotspots reveals that local microplastic distribution is governed by a complex interplay between anthropogenic source strength and riverine transport capacity, rather than being solely determined by emission intensity. This finding provides crucial insights for understanding microplastic pollution dynamics in complex river-delta systems and offers valuable implications for environmental management strategies.