Microplastics (MPs) distribution in Surface Sediments of the Freidounkenar Paddy Wetland

There is an urgent need to increase knowledge on the distribution of microplastics (MPs) in wetlands because these are sites of special ecological value and the ever-growing use of plastic can threaten such fragile ecosystems. This research assesses, for the first time, the occurrence of MPs in surface sediment of the Freidounkenar International Wetland (Northern Iran), a valuable habitat for migratory birds. A total of 1368 MP/kg were identified in the surface sediments of the wetland. The distribution of MPs in sediments per area was Ezbaran (36.5%), Western Sorkhrood (32.0%), Freidounkenar (20.1%) and Eastern Sorkhrood Ab-bandans (11.4%). The most contaminated sites were located close to agricultural fields, Damgahs (agroecosystems for birds), fishing areas and roads. Fibers and white-transparent and black-grey MPs constituted the dominant MPs in the surface sediment. The most abundant MPs were < 250 μm and these were made of nylon, polypropylene-low density polyethylene copolymer, polystyrene, low density polyethylene and polypropylene. The identification of MPs was carried out visually and supported with Scanning Electron Microscopy (SEM)-Energy Dispersive X-Ray (EDX) and micro-Raman techniques. There were weathering signs in large proportion of the MPs, according to SEM analysis, which evidences their formation from the degradation of other plastics. This is a comprehensive study on MPs in surface sediment of this sensitive internationally recognized ecosystem with high ecological value.