BayCEER Workshop 2024

To the Atmosphere and Back: Toward a Deeper Understanding of the Governing Processes to Microplastic Deposition

Microplastics (MPs) are small pieces of synthetic polymers, typically smaller than 5 mm. These can have primary and secondary origin. When airborne, their variability and abundance are governed by various processes on the earth-atmosphere-surface. Despite the significant implications of the atmospheric deposition of MPs for the environment, ecosystems, and human health, our understanding of the atmospheric removal processes and underlying mechanisms remains limited. This is likely related to the fact that so far, no consistent link between the deposition of MPs and meteorological factors could be uncovered. To address these research gaps, we collected monthly atmospheric deposition samples, both wet and total, over one year from March 2022 till February 2023, at Bayreuth Centre of Ecology and Environmental Research, Germany, and analysed them for MPs. Close to this urban site, we monitored meteorological parameters such as temperature, wind direction and velocity, and precipitation. Here we report the abundance of MPs in the atmospheric fallout, their size, shape, and polymer type obtained by analysing our samples using micro-Fourier transform infrared spectroscopy (µ-FTIR). This dataset was used to statistically elucidate the link between possible underlying processes of MP sources, transport, and removal. At our study site, wet deposition accounted for approximately half of the total yearly MPs’ atmospheric deposition. Most MPs in the deposition samples were fragments accounting for 87% of all detected particles. A very highly significant difference in the size of beads between wet and total deposition was calculated, with both fragments and beads being smaller in size in wet deposition. Our findings suggest that smaller MP particles are likely more efficiently removed by wet deposition.

Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – SFB-1357, Project no. 391977956 – European Union’s Horizon 2020 research and innovation programme.