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 mu m 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.

Automated summary

There is a pressing need for research on the distribution of microplastics in wetlands, as these ecosystems of special ecological value are under threat from the growing use of plastic. This study examines the occurrence of microplastics in the surface sediment of the Freidounkenar International Wetland in Northern Iran, an important habitat for migratory birds. The researchers found a total of 1368 microplastics per kilogram in the surface sediments, with the highest concentrations near agricultural fields, agroecosystems for birds, fishing areas, and roads. The dominant types of microplastics were fibers, white-transparent, and black-grey particles.