Occurrence characteristics of microplastics in Dongting Lake, China

Abstract

Lakes are critical sinks for terrigenous microplastics (MPs), yet understanding their ecological risks remains hindered by data uncertainties and the absence of local background values. In this study, an enhanced pollution load index (PLI) model integrating stochastic mathematical methods and species sensitivity distributions (SSD) was developed. The model was applied to assess and predict the ecological risk posed by MPs in the surface water and sediments of Dongting Lake, the second-largest freshwater lake in China. Results revealed average MP abundances of 4889 (range: 1667–9667) items/m3 in surface water and 7058 (range: 3935–10,736) items/kg in sediments within the Dongting Lake District. Small microplastics accounted for 90% of total MP particles, predominantly as polyethylene fragments. SSD-derived predicted no-effect concentrations values were determined as 8620 items/m³ for water and 7022 items/kg for sediments. While surface water exhibited low MP pollution risk and sediments were classified as unpolluted, both compartments showed signs of potential pollution escalation, suggesting non-negligible ecological risks. Through conditional fragmentation modeling, primary MP sources were identified as Yangtze River upstream inputs, atmospheric deposition, and soil erosion. In conclusion, the enhanced PLI model demonstrates effective ecological risk assessment and forecasting capabilities across environmental media, providing strategic insights for lake MP pollution mitigation.