Microplastic concentrations in the Zandvlei catchment area and Estuary, Cape Town

Abstract

On a global scale, there is an increasing concern about the extent of plastic pollution in coastal areas. Global demand for plastic is increasing annually. South Africa has an extensive plastics manufacturing industry, but recycling is restricted and inadequate, with a large fraction of plastic waste entering the environment, which eventually degrades in smaller plastic particles, referred to as microplastic when smaller than 5 mm. Knowledge about the abundances and characteristics of microplastics is becoming ever increasingly important to assess the potential effects microplastics have on organisms and ecologically sensitive ecosystems. The aim of this study is to determine the abundance and polymer characteristics microplastics in the Zandvlei catchment and vlei area in Cape Town, South Africa from 2018 to 2021. Seasonal sampling was conducted to determine the characteristics (type, colour and size) of microplastics in the surface water and sediment. Microplastic polymer type was verified with a Fourier-transform infrared spectroscopy (FTIR). Microplastics were mainly transparent fibres smaller than 1000 μm size class. Concentrations were higher in sediment across the study 293 (± 37.1 SEM) with 18157 particles recorded across the whole study. This study provides baseline and quantitative information on microplastics in the catchment and Zandvlei Estuary. It will assess bioavailability of microplastics within the area and contribute to long term monitoring of the estuary and the surrounding areas. A risk assessment (Pollution Load Index, Polymer Risk Index and Pollution Risk Index) of microplastics sampled indicated that microplastics in the catchment compared to the vlei pose a greater threat to the environment. The results indicate that there is a need to monitor microplastics in riverine and estuarine ecosystems in South Africa.