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Microplastic (MP) are emerging contaminants of concern in freshwater reservoirs, yet their atmospheric inputs, hydrological transfer, and size-dependent fate remain poorly constrained, particularly in South Asia. This study integrates atmospheric deposition measurements, field observations, and hydrological modelling to quantify MP transport and retention in Rawal Lake, Pakistan. MPs were consistently detected in atmospheric fallout, surface water, and sediments, demonstrating active exchange across environmental compartments. Surface water concentrations ranged from 7 to 120 MP L⁻¹, while atmospheric deposition averaged ~18 MP m⁻² d⁻¹, indicating continuous external loading. Spatial patterns revealed elevated concentrations at inflow and shoreline sites, while the spillway exhibited lower levels consistent with export-dominated conditions. Size distributions and polymer composition indicated strong hydrodynamic sorting, with fine particles dominating atmospheric inputs and coarser particles preferentially retained in sediments. Model-based estimates further highlighted atmospheric deposition as a significant loading pathway relative to catchment inputs. Overall, Rawal Lake functions as an integrative sink influenced by both external inputs and internal processes, with implications for contaminant accumulation and freshwater management in urbanized catchments.
Mehboob et al. (Mon,) studied this question.