Vertical microplastic distribution in sediments of Fuhe River estuary to Baiyangdian Wetland in Northern China

Microplastics exist widely in water environment. The microplastic distribution in sediments can better reflect the long-term microplastic pollution, especially the vertical distribution. However, the vertical microplastic distribution in sediments is diverse and unclear. This paper is the first study on vertical microplastic distribution in estuary sediment of Fuhe River, the main upstream river flowing to Baiyangdian Wetland in the northern China. The typical feature of Fuhe River is that the effluent of municipal wastewater treatment plants is its main water source. Microplastics in 15 sampling sites and different depths (0-50 cm) were examined. Results showed that the microplastic content decreased with the increase of sediment depth, and the highest content was 1049 +/- 462 items/kg in the topmost sediment layer (0-5 cm). The particle size of microplastics was smaller in deeper sediment layers. The proportion of colored microplastics in deeper sediment layers was larger than that in shallower layers. Polyethylene (PE) and polypropylene (PP) were the main plastic polymer types in all sediment samples. The spatial distribution characteristics of microplastics in sediments were closely related to human activities, and the microplastic content was higher in the areas with more intense human activities. This study is helpful to understand the detailed distribution characteristics of microplastics in typical rivers in the northern China, and can provide guidance for reducing microplastic pollution.

Automated summary

The study on the vertical microplastic distribution in estuary sediment of Fuhe River in northern China revealed that microplastic content decreased with depth, with the highest content in the topmost sediment layer. The smaller particle size and higher proportion of colored microplastics were found in deeper sediment layers. The spatial distribution of microplastics in sediments was closely related to human activities, with higher content in areas with more intense human activities.