How microplastics crosses the buoyancy barrier

Microplastic particles in the environment are covered by a so-called eco-corona. The eco-corona is made up of natural organic matter (NOM) like biomolecules, humic substances and other natural molecules. NOM substantially changes the surface properties of microplastic particles and therefore the interaction with other surfaces in the aqueous environment influencing their aggregation behaviour. Using Colloidal Probe-AFM we studied the interactions of eco-corona covered microplastic particles on the nanoscale. Measurements were performed in different ionic concentrations to mimic changing environmental conditions. We found that the eco-corona is able to *pull* at the silica colloidal probe by polymer bridging. This mechanism will lead to aggregation and consequently sedimentation in the environment. With simple microplastic-silica sand aggregation experiments and following Raman- and ESEM-Imaging we verified the presence and stability of these aggregates on the microscale. In conclusion, we show that the eco-corona is able to form polymer bridges and *pull* surfaces towards itself to form aggregates on two different length scales. This mechanism may contribute substantially to microplastic particle aggregation in the aqueous environment and explains why microplastics sediment. Also see: https://micro2024.sciencesconf.org/557842/document