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Polymer-specific impacts of microplastics on mineral retention and soil stability
Summary
A laboratory study tested six common plastic polymers in soil and found polymer-specific effects on mineral retention and soil aggregate stability, with some MPs reducing soil structure while others had minimal impact, depending on polymer chemistry and surface interactions with soil particles.
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 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.
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