Comparative Assessment of Microplastics in Surface Waters and Sediments of the Vaal River, South Africa: Abundance, Composition, and Sources

Abstract We extracted microplastics from surface water and sediment samples from the Vaal River in Johannesburg, South Africa. Average abundances of 0.61 ± 0.57 particles/m3and 4.6 × 102 ± 2.8 × 102 particles/kg dry weight were recorded for water and sediment samples, respectively. In both sediment and water samples, more than 80% of microplastics were fragments and fibers of smaller than 2 mm. High-density polyethylene, low-density polyethylene, and polypropylene were the dominant polymers identified in both sample types. In addition, polyethylene co-vinyl acetate, polyester, polyurethane, and polyethylene/hexene-1-copolymer were also detected in sediment samples. Colored microplastics were the most commonly observed in both sample types; pigment yellow 83 was detected in surface water, and carbon black was detected in both sediment and water samples during Raman analysis. Taking into consideration the physical and chemical characteristics of the detected microplastics, their potential sources include inflow from tributaries, surface run-off from urban city centers, recreational activities, and wastewater effluent from industries and households. Environ Toxicol Chem 2022;41:3029–3040. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.