Fragmentation and Abrasion of Plastics by Sediments and Chemical Additive Leaching – PLASTICAL

• Applicant: Dr. Florian Pohl
• Subject Area: Geology ; Oceanography ; Physical Geography
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 532753326

Plastic waste is omnipresent in natural ecosystems and carries the potential for long-term ecological impacts. In particular, the increase in micro and nano-plastics through fragmentation and the release of chemical additives from plastics can lead to ecotoxicological effects. Current research shows that plastic waste is now an integral part of many natural sedimentary systems. Here, plastic is transported with sediments, abraded, and fragmented. However, it is not clear how efficient these fragmentation processes are and what sedimentary conditions favor them. Moreover, the size of plastic particles influences their transport and deposition behavior, which is crucial for predicting their accumulation in sedimentary systems. Most plastics are not used in their pure form but are mixed with chemical additives to generate certain material-specific properties (color, elasticity, inflammability). Some of these additives are related to health issues and are not firmly bound in the plastic structure, which is why they can leach out of the plastic particles into the environment over time. The leaching period or leaching rate depends on various environmental conditions but is also determined by the plastic surface available for leaching. As the degree of fragmentation of plastic particles increases, their leaching surface increases, ultimately increasing the leaching rate. Therefore, the fragmentation of plastics in the environment is also important to understand the period over which chemical additives are released by plastic particles. The aim of this project is to understand how different plastics are abraded and fragmented during various transport processes through sediments. In addition, the fragmentation rate is correlated with the leaching rate of chemical additives. This is investigated in laboratory experiments, which include a specially constructed annular flow channel to simulate the fragmentation rate under certain flow processes and compare this with the leaching rate of chemical additives. The results are compared and verified with field studies that investigate the surfaces of microplastic particles from the Rhine and Elbe for characteristic abrasion traces and chemical surface changes due to leaching processes. Transport, distribution, and deposition of microplastics in deep-sea canyon systems are simulated in scaled physical experiments in a test basin (11 x 6m). Finally, deep-sea sediments from three deep-sea canyon systems (Congo, Bengal, Gioia) are investigated on a total of three research cruises with regard to microplastic concentrations and particle size distributions, as well as chemical additives leached from the plastic.

• DFG Programme: Independent Junior Research Groups