Assessment of Microplastic Contamination in Freshwater Fish and Sediments of the River Benue in Kogi and Benue States

Microplastic pollution is an emerging contaminant of freshwater ecosystems globally, yet published data on microplastic occurrence in Nigeria's major inland rivers, including the Benue River, remain scarce. This study assesses microplastic contamination in freshwater fish and surficial sediments from six sampling stations along the Benue River between Lokoja in Kogi State and Makurdi in Benue State. Fish gastrointestinal tracts were extracted and digested with potassium hydroxide, and microplastics were isolated by density separation and filtration. Sediment samples were processed by wet peroxide oxidation. Microplastic particles were identified and quantified by stereomicroscopy and Fourier-transform infrared spectroscopy. Microplastics were detected in 72.4% of fish gastrointestinal tracts sampled, with an average abundance of 3.8 particles per fish. Fibres constituted 64% of microplastic morphotypes in fish, followed by fragments (24%) and films (12%). Dominant polymer types were polyethylene terephthalate, nylon, and polypropylene, consistent with fishing net, textiles, and packaging waste sources in riparian communities. Sediment microplastic concentrations averaged 234 particles per kilogram dry weight, increasing from upstream to downstream stations and correlating with proximity to population centres. The study establishes the first empirical dataset on microplastic contamination in the River Benue and provides a baseline for monitoring the effectiveness of future plastic waste management interventions. Keywords: microplastics, freshwater fish, River Benue, sediment contamination, FTIR