Microplastic pollutants in sediments from a water supply reservoir: Spatial heterogeneity in abundance, characteristics and pollution evaluation

When assessing microplastics (MPs) in freshwater ecosystems, previous studies have primarily focused on natural rivers and lakes, with limited attention to urban water source areas. Sediments, recording the steady process of MPs accumulation during a long period of time, can act as an important sink for MPs. In this study, we investigated the distribution, characteristics and pollution evaluation of MP contaminants in sediments of a water supply reservoir of Hefei City (the Dafangying Reservoir). Meanwhile, the differences of MP concentrations in sediments in rural and urban areas were also compared. Our results detected five shapes, seven colors and six polymer types of MPs in sediments of the Dafangying Reservoir. Polystyrene, polyethylene and polypropylene were the most abundance types of MPs identified. The average MPs abundance of sediments in rural areas was 83.20 ± 32.99 n/100 g dry weight (d.w.), and 182.67 ± 72.21 n/100 g (d.w.) in urban areas. The total MP concentrations were significantly higher in sediments of urban sites than that in rural sites, which can be ascribed to more complex and diverse MP sources triggered by intensive anthropogenic activity in cities. Specifically, we also demonstrated significantly higher microbead abundance in urban sites, which may result from the widespread use of microbead in personal care products. Given the complexity and diversity of MPs in urban areas, we exhibited a relatively higher abundance of MPs in the Dafangying Reservoir than that in other rural larger reservoirs. According to the index of geoaccumulation, the sedimentary MPs were assessed as moderately polluted. Our study enriches valuable data on the distribution of MPs contaminants in water supply reservoir, and provides theoretical references for MPs control and management in reservoir ecosystems.