Sedimentary microplastic accumulation in choghakhor international wetland: a modeling approach to local-scale determinants

Background: Microplastic (MP) pollution significantly threatens aquatic ecosystems in Iran because of increasing human activities affecting inland surface freshwater resources. Methods: Our study focused on the Choghakhor International Wetland, quantifying the presence of MPs on the wetland surface sediment, revealing an average of 87.5±11.5 pieces per kilogram of sediment throughout the wetland. We employed the Generalized Additive Model to identify local factors influencing the accumulation of MPs, considering various uncorrelated variables, including electrical conductivity (EC; average=570.0±14.0 dS/m), pH (average=6.98±0.07), organic matter (OM; average=3.51±0.32 %), the Soil Texture Index (STI), Landsat-derived water depth (DEP; R2=0.659), and substrate slope (SLO). Results: The results of the GAM model (R2=0.750; Deviance explained=79.1%) revealed that sediments with finer particles enriched with elevated OC and EC content on flat substrates within the wetland are more susceptible to the accumulation of MPs. Conclusion: These findings underscore the substantial role of sediment attributes, and to a lesser extent, substrate physical characteristics in shaping the dynamics of MP pollution in the Choghakor Wetland.