Prevalence and physicochemical characteristics of microplastics in the sediment and water of Hashilan Wetland, a national heritage in NW Iran

Abstract

The freshwater Hashilan Wetland is an Iranian national heritage in Kermanshah Province which is planned to be registered as a World Heritage site because of its uniqueness in Iran and the neighboring countries. However, no comprehensive investigation on microplastics pollution in the sediment and water is available in the literature to help to preserve the aquatic environment. Thus, sediment and water samples were collected at 16 stations of the wetland and the extracted microplastics were characterized using visual identification, fluorescence and polarized lights, SEM-EDX, and μ-Raman methods. The results indicated presence of microplastic particles in Hashilan Wetland samples. A total of 71 microplastic particles were found in the sediments. The highest number of microplastics were observed close to roads, agricultural fields and tourist centers; however, no particle was observed in the control stations far from the aforementioned places. Cluster analysis showed a significant correlation between microplastic concentration and the clay fraction. Regarding the microplastic shape, Fibrous microplastics were the most frequent (>90%) in water and sediment samples. About 38.03% and 33.33% of the found microplastic particles are smaller than 100μm in the sediment and water, respectively. Classifying the microplastics according to their color result in the decreasing order of black/gray (47.88%) > blue/green (33.8%) > red/pink (18.31%) in the sediments and blue/green (66.67%) > red/pink (33.33%) in the waters. The detected microplastics in Hashilan water and sediment were polyethylene (PE), polypropylene (PP), polystyrene (PS) polymer. Positive matrix factorization (PMF) based on IMPROVE program was run and the results demonstrated relatively similar behaviors of microplastic particles and some potentially toxic elements including Pb, Zn, Cu, and Fe together with the percentage of organic matter and clay fraction in the sediments.