Assessment of microplastic pollution in River Niger sediments bodies in Lokoja, Nigeria

Abstract

Despite increasing concern over microplastic pollution in freshwater ecosystems, limited information exists on the abundance, polymer composition, and seasonal distribution of microplastics in sediments of the River Niger. This study therefore investigated the abundance, characteristics, and polymer composition of microplastics in sediments collected from 10 sampling sites along the river in Lokoja, Nigeria, with the objective of quantifying contamination levels, identifying dominant polymer types, and evaluating seasonal variations between rainy and dry periods. Sediment samples were collected using standardized procedures and processed through density separation, wet peroxide oxidation, stereomicroscopy, and Fourier Transform Infrared Spectroscopy (FTIR) analyses. Five major polymer types were identified: Polyethylene terephthalate (PET), Polyethylene (PE), Polyvinyl chloride (PVC), Polypropylene (PP), and Polystyrene (PS). PET and PE were the dominant polymers across all sites and seasons, jointly accounting for over 55% of the total microplastics detected, reflecting their widespread use in beverage bottles, sachet water packaging, and polyethylene bags. PVC and PP occurred at moderate levels, while PS was the least abundant. Seasonal variation was minimal, indicating continuous pollution inputs from domestic waste disposal, commercial activities, and storm water runoff. Higher contamination levels were recorded at densely populated and industrial-adjacent locations, including Gadumo, Old Market, and Ganaja. Although concentrations were moderate compared with heavily industrialized regions, the persistence and accumulation of these polymers present emerging ecological risks, highlighting the need for improved waste management, continuous monitoring, and strengthened environmental policy interventions.