Distribution of Microplastics in the Sediment Profiles of River Benue, North Central Nigeria

Microplastics (MPs) are increasingly recognized as ubiquitous contaminants, with freshwater systems acting both as sinks and conduits for their transport to marine environments. Yet, data on their occurrence in African freshwater systems—particularly in Nigeria—remain limited. This study assessed their presence in sediments from the River Benue. Samples were collected in December 2023 and processed using NaCl/NaI density separation and H₂O₂ oxidation, while suspected MPs were characterized using FTIR and SEM–EDS. A total of 70 suspected MPs ranging between 0.5–5 mm were recovered, with the southern bank exhibiting higher abundance (43 items kg⁻1) than the northern bank (27 items kg⁻1). Fragments and films were the dominant morphotypes. Surface sediments from the southern bank recorded mean particle and mass concentrations of 2.8 ± 1.9 items kg⁻1 and 20.3 ± 10.8 mg kg⁻1 d.w, decreasing to 0.8 ± 1.0 items kg⁻1 and 3.0 ± 4.3 mg kg⁻1 d.w in deeper layers. On the northern bank, surface layers contained 1.9 ± 2.6 items kg⁻1 and 17.1 ± 20.7 mg kg⁻1 d.w, dropping to 0.3 ± 0.58 items kg⁻1 and 4.2 ± 9.9 mg kg⁻1 d.w at depth. Tentatively identified polymers included polystyrene, polyethylene terephthalate, and polyamide. Preliminary risk assessment revealed contamination factor values of 1–19 and pollution load index values of 1–4.36, with a PLIzone of 2.28, indicating polluted conditions. The findings highlight anthropogenic influence on MP contamination and provide critical data on Nigeria’s freshwater systems, underscoring the need for expanded monitoring and implementation of abatement strategies.