Sediments microplastics along three Ethiopian Rift Valley lakes demonstrated variation in polymer composition and...

Microplastic contamination in freshwater ecosystems poses an escalating threat to ecological and human health, yet data from African lacustrine environments remain scarce. This study offers a comprehensive assessment of microplastic pollution in sediments from Lakes Ziway, Hawassa, and Koka in the Ethiopian Rift valley. This work aimed to investigate the spatial and temporal distribution of microplastics as a function of surrounding land use and seasonal changes. Samples collected during wet and dry seasons contained 20 to 740 particles kg^-1, with Lake Koka exhibiting the highest mean concentration (454.17 ± 123.92 particles kg^-1), followed by Hawassa (350.42 ± 149.95 particles kg^-1) and Ziway (282.78 ± 151.10 particles kg^-1). Wet-season levels significantly exceeded dry-season concentrations (χ² = 1482.0, p < 0.001), reflecting the role of surface runoff in pollutant transport. Secondary microplastics predominated, mainly as fibers (63.8 %) and fragments (32.5 %), with polyamides (41.9 %), polyethylene (30.4 %), and polypropylene (21.7 %) as the dominant polymers. The study revealed widespread contamination with marked spatial, seasonal, and compositional variability. Pollution Load Index values confirmed severe contamination (PLI >1), with Lake Koka (4.76) reflecting diffuse pollution, compared to more localized inputs at Ziway (3.46) and Hawassa (4.10). These findings underscore the influence of anthropogenic activities and hydrological processes, highlighting the urgent need for targeted waste management and further research into source identification, polymer degradation, ecological and public health risks.