Quantitative and qualitative analysis of microplastic pollution in a large European river

Introduction Microplastic pollution consists of plastic particles smaller than 5 mm, originating from the fragmentation of larger plastic debris due to processes such as ultraviolet radiation, as well as from primary sources including industrial plastic pellets. These particles are widely transported across atmospheric, aquatic, and terrestrial systems and pose significant environmental and health risks to flora, fauna, and humans. Rivers play a critical role in conveying microplastics to aquatic environments. This study investigates microplastic pollution in the Hungarian section (Budapest reach) of the Danube River, Europe's second-largest river and a vital water resource for the region. Methods Water samples were collected across different depths of the water column using a Multilevel Manta net. Laboratory analyses were performed using Fourier-transform infrared (FTIR) spectroscopy and digital microscopy for polymer identification and particle characterization. Concurrent flow measurements were conducted to estimate microplastic mass flux rates. Results The average microplastic concentration was 0.311 mg/m3 (142 particles/m3). The most abundant polymers were polystyrene, polyethylene, and polypropylene. Detected particles occurred in various forms, including fragments, foam, and flakes, and exhibited colors such as yellow, black, gray, and green. These findings indicate substantial microplastic contamination in the studied reach of the Danube River. Discussion The results highlight the Danube River's role as a significant transport pathway for microplastics and underscore the need for targeted monitoring and mitigation strategies. This study contributes to understanding microplastic dynamics in large European rivers and provides valuable insights for developing effective pollution control and management approaches.