Polymer-specific impacts of microplastics on mineral retention and soil stability

Microplastics (MPs) contamination threatens soil structure and function. We quantified how six common polymers: polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene-terephthalate (PET), polyurethane (PU) and polyvinyl-chloride (PVC), interact with minerals in four textural (sandy-clay-loam, silty-clay-loam, clay-loam and sandy-loam). Retention, porosity, and aggregate stability were measured with SEM, FTIR, zeta-sizer, and X-ray-diffraction. Low-density polymers (PE and PP) accumulated at 5-10 mg kg^-1 in fine soils and raised stability by 20 %. High-density polymers (PVC and PET) were concentrated in the clay fractions of coarse soils and reduced macroporosity by ≤ 15 %. Allophane and kaolinite adsorbed 19 % and 12 % of low-density MPs, respectively, whereas hematite and hornblende retained ≤7 %. Polymer density and mineral surface area jointly govern MP fate and the resulting shifts in soil physical quality. These polymer-specific mechanisms support the targeted mitigation and refined risk assessment of terrestrial microplastic pollution.