Application of high-resolution site characterisation tools and sampling methods for assessing microplastic migration...

The study addresses a significant environmental issue: the accumulation of microplastics (MPs) in municipal solid waste (MSW) dumpsites and their migration into deeper soil and groundwater (GW). Given the global increase in plastic production and limited waste management, this topic is highly relevant. Furthermore, many studies lack robust methodologies for tracking MP movement through complex soil strata. This study presents an innovative approach, employing advanced site characterisation and sampling techniques, including cone penetration test (CPT), hydraulic profiling tool (HPT), continuous soil sampling, and discrete GW sampling. This integrated method facilitates the identification of high-permeability zones, enabling large-depth sampling while reducing cross-contamination risk. Key findings reveal a substantial MSW layer containing plastics, textiles, and metals in specific zones, while natural soils dominate other areas. Unsaturated zones are mainly sandy, with occasional low-compressibility clay layers. MP concentrations are notably high at the MSW-soil interface 6600-8800 items/kg and decrease significantly with depth to 300-700 items/kg in saturated zones. Smaller MPs (<500 µm), mainly polyethylene, polypropylene, polyamide, and polyester, dominate soil samples. In GW, MP levels range from 26 to 171 items/L, with fibers (<250 µm) comprising about 80 % of MPs, highlighting subsurface soils as partial barriers to MP migration.