Microplastic pollution in the Vaal River system

Abstract

This thesis aimed to address the escalating issue of plastic pollution in South Africa's freshwater systems across several key objectives. Findings from the study highlighted the extensive presence of microplastics (MPs) throughout the Vaal River system, particularly in sediment samples, with concentrations in some areas comparable to highly polluted rivers in other regions. Notably, the heavily polluted Klip River exhibited the highest MP concentrations, including an unprecedented high presence of microbeads, indicating the severity of pollution in urbanized and densely populated areas where waste mismanagement is prevalent. Identification of plastic pollution sources revealed a strong correlation between macroplastic presence and MP concentrations in water and sediment, emphasizing local environmental plastic pollution as a significant predictor for riverine MP loads. Urbanized catchments, characterized by dense populations and inadequate waste management, were found to host the highest MP concentrations. Furthermore, the temporal dynamics of MPs in South African freshwater systems demonstrated contrasting trends between heavily polluted and less impacted rivers during the rainy season, emphasizing the influence of runoff on MP concentrations. Insights into the sinks of microplastics underscored sediments as temporary repositories for MPs, particularly during low-flow periods, with rapid settling observed, especially for microbeads. Additionally, wetlands were identified as effective filters, trapping MPs in sediment during low flow periods, raising concerns regarding the accumulating MP concentrations in these sensitive ecosystems. Addressing mitigating actions, recommendations emphasized the urgent need to improve waste management infrastructure, enhance functionality at wastewater treatment plants to minimize MP release into rivers, restrict microbead production, raise public awareness, conduct regular river cleanups, and remove macroplastics from the environment to prevent further generation of MPs. These findings collectively underscore the critical importance of strategic interventions and holistic measures to curtail and remediate plastic pollution in South Africa's freshwater systems.