Characterization of Microplastic Pollution of Sediments from Urban Lakes

Abstract

In recent years, microplastics (MPs) in the environment has become a topic of increasing concern. In this study, typical urban lakes, such as Yushan Lake and Nanhu Lake in Maanshan City, were selected to study the physical morphology and spatial distribution characteristics of MPs in sediments in spring and summer and to explore the sources of MPs in the lakes. On average, MPs in sediments occurred with a content of (0.0284±0.0597) g·kg-1 and abundance of (278.9±529.1) n·kg-1 in spring, and (0.0317±0.0778) g·kg-1 and (277.1±395.6) n·kg-1 in summer, respectively. Using a paired sample T-test, it was found that there was no significant correlation difference between the content (N=22, t=-0.269, P=0.791) and the abundance (N=22, t=0.035, P=0.973) of MPs in the spring and summer sediments. Regarding shape, the MPs in the sediments in the study area were divided into three types:fiber, film, and particle, accounting for 52.9%, 28.9%, and 18.2%, respectively. Size-fraction analysis indicated MPs<1 mm made up the majority, accounting for 83.9% of the total number. It was found that the MPs were mainly polyethylene (PE) and polypropylene (PP) polymers with seriously weathered surfaces. The sediments, which were adjacent either to land with a large stream of people and vehicles or to areas with frequent watersports, had notably high abundance of MPs, revealing the close correlation between the spatial distribution of MPs in lake sediments and human activities. It is thought that atmospheric precipitation (fiber), stormwater, washing of clothes (fiber), degradation of large plastics in the lake, and fishing activities (fishing nets, foam) are the main sources of MPs in lake sediments.