Tracing microplastics in deep reservoir using conditional fragmentation model and DOM spectral characteristics

Reservoirs are artificial lakes that act as pivotal sinks for diverse pollutants. However, the environmental behavior and source identification of microplastics (MPs) in deep reservoirs remain poorly understood. In this study, the potential sources of MPs in the Danjiangkou Reservoir were explored using the conditional fragmentation model (CFM), supplemented by dissolved organic matter (DOM) characterization. The average MP abundance in reservoir was 10,476 ± 5594 items/m 3 . An enhanced pollution load index model based on the SSD-derived predicted no-effect concentration suggested an overall “low risk” status. Source apportionment based on CFM indicated that soil erosion was the main source of MPs, followed by atmospheric deposition. Importantly, MP abundance exhibited a strong positive correlation with exogenous terrestrial humic substances, suggesting that MPs are likely co-transported with terrestrial runoff, thereby supporting the soil input pathway. This study provides vital insights into the environmental fate and transportation of MPs in deep reservoirs.