| Ms | Ioana | Caprar | Babes-Bolyai University | Romania | Environmental Science | Assessing the Potential Microplastic Sources and Retention Efficiency in Valencia’s Tancat de la Pipa Wetland Abstract Constructed wetlands are promising nature-based solutions for mitigating environmental pollution, able to retain suspended solids as microplastic (MP) particles. This study aims (i) to identify potential sources and transport pathways of MPs in the Tancat de la Pipa constructed wetland (Spain), using a conceptual source-attribution approach based on spatial distribution, particle characteristics, catchment characteristics, hydrological connections, and the available literature and official information, as well as (ii) to evaluate the effectiveness of the wetland in retaining MPs within the investigated size range. Sampling was conducted at six locations representing two inlet canals, two internal sites, and two outlet points of the wetland towards Albufera Lake. Higher MP abundances were recorded at the inlet, while lower concentrations at internal and outlet sites indicated partial retention, with apparent removal efficiencies ranging from 24% to 50%, depending on the sampling campaign. Blue and transparent MPs predominated, while polyethylene (47%) and polyester (18%) were the dominant polymers, followed by polymethyl methacrylate (10%), polystyrene (8%), and polypropylene (7%). The spatial distribution and particle characteristics, together with catchment land use and hydrological connections, indicated potential contributions from mixed sources, including packaging, agricultural activities, wastewater, traffic runoff, fisheries, and industrial activities. These findings provide an initial assessment of potential MP sources and transport pathways in a Mediterranean wetland and indicate partial retention of MPs within the investigated size range, supporting the need for longer-term and source-specific monitoring to improve source attribution and evaluate seasonal variability. Keywords: microplastics; wetland; Albufera; pollution; nature-based solutions | | |