Clement Alibert, Mathilde Duval, Stephanie Slowinski, Fereidoun Rezanezhad, Philippe Van Cappellen (2022). Standardized experiments for microplastics migration in soils. Proceedings of the GWF Annual Open Science Meeting, May 16-18, 2022.

Microplastics (MPs) are now recognized as a major and significant environmental contaminant. The continued production of plastics coupled to their degradation and the transport of macro- and micro-plastics has resulted in widespread contamination of many environmental systems, including most remote ones. Although lentic aquatic systems are usually considered to be the final receivers of MPs, soils are also an important receiver of microplastic contamination, even if they are a temporary reservoir that the microplastics eventually lost from via runoff to surface water or percolation to groundwater. MPs in soil may also enhance or slow down the migration of other contaminants already present in soils via chemical or physical associations with these other contaminants. However, the mechanisms controlling MP migration through a soil profile and the relative potential for MP loss from soil via runoff or percolation are not yet well understood. Some reasons for this knowledge gap include the lack of systematic and comprehensive analysis techniques for MPs in soils, and a lack of field and experimental data. As a result, there is a deficit in the ability to model microplastics transport in soils, which will be necessary for modelling their watershed-scale fate and transport. In this research, we review the existing literature that exists about microplastic transport experiments in soils and highlight key knowledge gaps that should be addressed. The transport and mobility of MPs in soils are mainly controlled by their size, shape, and surface properties, which collectively control the physical and chemical interactions of MPs with their surrounding environment. There is a lack of experiments of microplastic migration in soils under controlled conditions testing the effect of size, shapes, density, material type, surface properties, extent of MP degradation, and soil composition. We also noticed that experimental setups and conditions are quite variable from one laboratory to another. The main goal of this study is to standardize a method under controlled conditions to fill the main gaps regarding the transport of microplastics in soil systems by considering the main key parameters such as: downward vertical migration, microplastic types/sizes/shapes/aged and soil types. Results obtained by testing and monitoring the effect of all those parameters under controlled conditions will help for the development microplastics transport modeling in soil systems.

AOSM2022 UWaterloo core team First Author: Clement Alibert, Water Institute and Department of Earth and Environmental Sciences, University of Waterloo Additional Authors: Mathilde Duval (Water Institute and Department of Earth and Environmental Sciences, University of Waterloo), Stephanie Slowinski (Water Institute and Department of Earth and Environmental Sciences, University of Waterloo), Fereidoun Rezanezhad (Water Institute and Department of Earth and Environmental Sciences, University of Waterloo), Philippe Van Cappellen(Water Institute and Department of Earth and Environmental Sciences, University of Waterloo)