Microplastic occurrence in sediments of informal settlement in Durban, South Africa: assessing the ocean impact in the aftermath of floods

The environmental impact of microplastics is increasingly being recognized, leading to their inclusion as contaminants of emerging concern. Consequently, it is essential to identify and monitor microplastics and their impact on the ecosystem. In this study, a ball miller was employed to process plastic waste, generating microplastics for the optimisation of separation methods. Microplastics of various sizes and shapes were produced and used to spike the sediments for optimisation of the density separation method. The recovered microplastics ranged from 0.74–5 mm, as confirmed by stereomicroscopy. In addition, the types of polymers present in microplastics were confirmed using Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR). The developed analytical method was employed to study the occurrence of microplastics in river sediments passing through informal settlements after floods. Moreover, the evaluated data confirmed that informal settlements are a major source of microplastics found in the ocean after a flood. Microplastics in river and ocean sediments were predominantly composed of polypropylene, polyethylene, and polystyrene with a size range of 0.90–5 mm. To the best of our knowledge, this study is the first to report the impacts of informal settlements on the ocean during floods in Africa.