A field experiment on macroplastic redistribution and fragmentation by soil tillage

Soil is polluted with plastic waste from macro to submicron level, and research has intensified on the fate and transport of plastic with more focused particulate plastic, including fibers (<5mm). Yet, our understanding of macroplastic (>5mm) occurrence and behavior has remained comparatively elusive, mainly due to a lack of tracing mechanism. This study utilized magnetically tagged soil movement and provided a comparison with a method for tracing macroplastic pieces labeled with a physically adhesive passive radiofrequency identification transponder used as an innovative and efficient approach. A field study following best practice approaches of soil tillage was carried out to determine the displacement of macroplastic during the non-inversion chisel and inversion disk tillage process to understand the fate of macroplastic in arable land. All the experiments were performed at plain topography to eliminate the downslope and drift effect, while tillage depth (0.15 m) and speed (4.5 km h^-1) were kept constant during the tillage process. The results indicate that non-inversion tillage has a significantly more protracted macroplastic transport displacement compared to inversion tillage by a factor of 2.4.  The mean displacement of macroplastic by tillage erosion is 0.36 ± 0.25 m chisel and 0.15 ± 0.13 m disk tillage per pass. However, inversion tillage caused substantially more fragmentation of macroplastic. In general, both tillage implements drove the burial of surface macroplastic into the plow layer.  This highlights that soil can act as a long-term sink for macro and microplastic and would expect less plastic to be transported into the atmosphere and aquatic system from arable land.

 

This project gets financing from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement number 955334.