Microplastics pollution in urban freshwater sediments: A descriptive assessment of land-use categories

Microplastics (MPs) contamination is a pressing environmental concern due to its widespread presence in aquatic ecosystems and potential adverse effects. Microplastic (MP) abundance is highly variable and may be influenced by urban land-use types. However, studies examining the relationship between land use and source-specific MP distribution in urban freshwater systems, particularly stormwater retention (SWR) ponds, remain limited, representing an important research gap for urban stormwater management and flood control practices. Therefore, this study investigated the distribution of microplastics in pond sediments and assessed how different urban land-use types (residential, educational, and mixed-use areas) contribute to MP pollution in SWR pond sediments. MPs were identified using Nile Red staining and fluorescence microscopy, enabling detection of MPs ranging from 25 to 2000 μm. MPs were detected in all sediment samples, with an average abundance of 521.25 ± 302.46 items/kg dry sediment. Fragments and fibers were the most prevalent MP types, comprising 75 % of total MPs, with a dominant size range of 75-300 μm. Sediments from predominantly educational and residential catchments exhibited higher MP pollution levels than mixed-use areas; however, no statistically significant correlation was observed between land-use type and MP abundance. These findings demonstrate that urban SWR ponds can act as effective sinks for MPs from the urban environment.