Microplastics occurrence, abundance, and typology across various locations of the Akaki River during the wet season

Graphical abstract showing microplastic pollution assessment of the Akaki River, Ethiopia, during the wet season. The study design shows 30 samples from 10 sites with 100% detection. Abundance ranges from 331 to 1,361 particles per liter. Fibers and transparent particles dominate morphology. Polyethylene 35%, PET 25%, and polypropylene 25% are the main polymers. Ecological risk is classified as high at all sites. Plastic is extensively used in various sectors, and its breakdown to microplastics (MPs) poses significant ecological and health concerns. In Ethiopia, the Akaki River plays a crucial role in socioeconomic use in urban and peri-urban agricultural regions, but it is vulnerable to natural and human-made pollution. This study aims to assess the abundance, morphology, and polymer types of MPs in the Akaki River during the wet season. A laboratory-based cross-sectional study was conducted using a purposive sampling technique, and 30 water samples were collected from 10 sites. The laboratory analysis is performed by sieving, density separation, organic digestion, filtration, and detection of MPs under a stereomicroscope and Fourier-transform infrared spectroscopy. MPs were found in all water samples, ranging from 331 to 1,361 particles/L. The most prevalent MPs were transparent particles, fibers, and polyethylene. Kruskal-Wallis testing found statistically significant differences in the median microplastic abundance of sampling points. The abundance of fibers and transparent particles was found to be strongly correlated. The microplastic concentrations after rescaling are higher than reported for river waters in other areas, highlighting that the river is highly polluted. The study emphasizes the need for improved waste management and stricter regulations on wastewater treatment in Addis Ababa.