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Effect of microplastics on swelling behaviour of geosynthetic clay liners (GCLs)
Summary
Laboratory tests exposing geosynthetic clay liner (GCL) bentonite to 1 µm polystyrene microplastics found no measurable effect on swelling behavior or hydraulic properties in this preliminary study. While reassuring for landfill containment integrity, results are limited to one MP type and size, leaving open questions about whether more varied or abundant microplastics—common in actual landfill leachate—could degrade these barriers over time.
Microplastics (MPs) are emerging persistent pollutants and landfills have been evidenced as one of the main sinks of MPs. Landfill-based lining systems are employed to prevent contaminated leachate from migrating to underlying aquifers. Geosynthetic clay liners (GCLs) composed of bentonite clay are widely used in lining systems due to their high swelling capacity and low hydraulic conductivity. However, bentonite clay is chemically reactive, and its engineering properties are significantly affected when exposed to ion-concentrated solutions. No studies have investigated the impacts of MPs on the engineering properties of GCLs despite the well documented presence of MPs in landfill leachate. In this paper, results of an experiment during which a GCL was exposed to spherical 1 μm polystyrene MPs in the laboratory are reported. The effects of the exposure on the swelling potential of the GCL and the interaction between MP and bentonite, using scanning electron microscopy (SEM), are discussed. Swelling index (SI) and oedometer swelling strain tests were conducted to characterize swelling behaviour. While the preliminary results reported here are limited to a single type, size and shape of MP, no evidence of an effect of polystyrene MPs on swelling of GCL’s bentonite has been found.