Abundance of microplastics in sediments from the urban river in Mongolia

Microplastics (MPs) are ubiquitous pollutants of the aquatic environment; however, the behavior of these materials in freshwater environments is largely unknown. The present study aimed to identify types of MPs and quantify their concentration in the river bottom sediment in the Tuul River, northern central part of Mongolia. The goal was also to analyze and evaluate the behavior of MPs. Six sampling plots were chosen as the research objectives, which were close to the junctions between tributaries and the main river of Tuul in the capital of Mongolia,Ulaanbaatar. All sediment samples contained MPs with an average concentration of 603±251 items kg−1. The major morphotype was synthetic fibers, which originated from polyester and polyamide polymers. While the size of MPs ranged between 28.4 µm and 3409.1 µm, most of these materials varied between 100 and 200 µm. Furthermore, the finer the particle sizes of sediments, the higher the number of detected MPs. Distribution of the MPs in the study area indicates that the point-source of MPs such as wastewater treatment plant strongly affects their concentration. However, domestic wastes (i.e., plastic litter) impact the distribution of MPs as non-point sources.