Occurrence, Distribution, and Characteristics of Microplastics in the Sediment of the Ovia River, Benin City, Nigeria

This study assessed the occurrence, distribution, and characteristics of microplastics in sediment samples from the Ovia River, Southern Nigeria, across six sampling months from December 2024 - May 2024 from four stations to evaluate spatial and seasonal variations in microplastic abundance, polymer types, particle size, and elemental composition in bottom sediments using Fourier Transform Infrared Spectroscopy (FTIR), and elemental composition via Energy Dispersive X-ray (EDX) spectroscopy. The results showed that Station 2 recorded the highest mean microplastic count (8.67 particles/sample), while Station 1 had the lowest (3.67 particles/sample). Polyvinyl Alcohol (PVA), Polybutadiene (PB), and Polyisoprene (PI) were the most prevalent polymers across stations. The downstream locations (stations 3 and 4) exhibited greater polymer diversity, including Polystyrene (PS), Polyurethane (PU), and Polyamide (PA), likely due to urban and industrial inputs. Particle size distribution revealed a decline from upstream to downstream, with the largest particles recorded at station 2 (2.85 µm) and the smallest at station 4 (1.27 µm) in January 2024. There was a decrease in the particle sizes characteristics across all the study stations in May 2024, suggesting seasonal degradation or transport dynamics. Fourier Transform Infrared (FTIR) spectroscopy confirmed dominant polymer types, with functional groups indicating alcohols, alkenes, amines, and alkynes. Energy Dispersive X-ray (EDX) analysis revealed carbon as the predominant element, with minor but uniform traces of nitrogen, phosphorus, chlorine, and silicon across stations. Analysis of variance showed no significant differences in elemental concentrations. The study confirms that sediments from Ovia River act as major sinks for microplastics, with pollution influenced by land-use activities and hydrological patterns. High diversity and accumulation at certain stations reflect localized pollution sources. There is an urgent need for improved waste management, environmental monitoring, and public education on plastic use.