Occurrence and distribution of microplastics in surface sediments of a typical river with a highly eroded catchment, a case of the Yan River, a tributary of the Yellow River

Xiaoli Zhao; Zihan Liu; Lu Cai; Jianqiao Han

doi:10.1016/j.scitotenv.2022.160932

Occurrence and distribution of microplastics in surface sediments of a typical river with a highly eroded catchment, a case of the Yan River, a tributary of the Yellow River

Sci Total Environ. 2023 Mar 10:863:160932. doi: 10.1016/j.scitotenv.2022.160932. Epub 2022 Dec 14.

Authors

Xiaoli Zhao¹, Zihan Liu¹, Lu Cai¹, Jianqiao Han²

Affiliations

¹ Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi, China.
² Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi, China; Institute of Soil and Water Conservation, Chinese Academy of Science and Ministry of Water Resources, Yangling, Shaanxi, China. Electronic address: hjq13@163.com.

PMID: 36526203
DOI: 10.1016/j.scitotenv.2022.160932

Abstract

Investigation of microplastic contamination in riverbed sediments can help clarify long-term microplastic pollution and establish prevention measures in watersheds. However, little research has been conducted on riverbed sediment pollution on the Loess Plateau, a highly eroded area in Northwest China. This research investigates the Yan River as a case study. The occurrence and distribution of microplastics were surveyed and analyzed to explore the microplastic pollution in the riverbed of the Loess Plateau. Microplastics were found in all sediment samples, with an abundance of 208.89-686.67 items kg^-1. Polypropylene and polyethylene were the main microplastic components identified using Fourier transform infrared spectrometry and imaging systems. Particles 0.5-1.0 mm in size accounted for 38.5 % of the total microplastics in this region. The main microplastic colors were black, white, and transparent, which accounted for 40.75 %, 20.75 %, and 20.38 % of the total microplastics, respectively. There was an increasing trend in the microplastic abundance in sediments in the downstream direction that accompanied the increase in population density from 55.31 persons km^-2 upstream to 230.05 persons km^-2 downstream. Microplastic pollution was related to the complex geographical, semiarid monsoon climate, elevation, grassland, per capita GDP, and anthropogenic factors in the Yan River basin. The erodible loess and high-intensity rainstorm promoted severe soil erosion, which caused microplastics absorbed in the soil to migrate to the river. Poorly managed solid wastes, such as agricultural mulch, plastic bottles, and other plastic products are also sources of microplastics in the riverbed. This study further clarifies microplastic pollution in typical rivers of highly erosive areas and provides useful information for basin management.

Keywords: Loess Plateau; Microplastic; Sediment; Yan River.