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Transport of polystyrene microplastics in bare and iron oxide-coated quartz sand: Effects of ionic strength, humic acid, and co-existing graphene oxide
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Researchers investigated how graphene oxide nanoparticles and humic acid influence the transport of polystyrene microplastics through sand columns, comparing bare quartz sand with iron oxide-coated sand. They found that iron oxide-coated sand strongly retained microplastics regardless of other factors, while graphene oxide significantly promoted microplastic transport by increasing surface charge and creating steric barriers. The study suggests that the co-presence of nanomaterials and organic matter in the environment can significantly alter how microplastics move through soil and groundwater systems.
This research explored the effects of widely utilized nanomaterial graphene oxide (GO) and organic matter humic acid (HA) on the transport of microplastics under different ionic solution strengths in bare sand and iron oxide-coated sand. The results found transport of polystyrene microplastics (PS) did not respond to the presence of HA in sand that contains large amounts of iron oxide. Compared to bare quartz sand, ionic strength had little effect: <20 % of PS passed through Fe sand columns. There was a significant promotion of PS transport in the presence of GO, however, which can be attributed to the increased surface electronegativity of PS and steric hindrance. Moreover, GO combined with HA significantly promoted the transport of PS in the Fe sand, and transport further increased when the concentration of HA increased from 5 to 10 mg/L. Interestingly, the degree of this increase exactly corresponded to the change in the surface charge of the microplastics, demonstrating that electrostatic interaction dominated the PS transport. Further results indicated that co-existing pollutants had significant impacts on the transport of microplastics under various conditions by altering the surface characteristics of the plastic particles and the spatial steric hindrance within porous media. This research will offer insights into predicting the transport and fate of microplastics in complex environments.
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Researchers investigated how ferrihydrite-humic acid coprecipitates in soil affect nanoplastic transport through sand columns, finding that the mineral-organic coating weakens iron oxide retention of polystyrene nanoplastics via steric hindrance and added negative charge, and that UV aging further enhances nanoplastic mobility by increasing surface hydrophilicity and electrostatic repulsion.
Impact of particle size and oxide phase on microplastic transport through iron oxide-coated sand
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Researchers studied how different types of iron oxide coatings on sand affect the movement of polystyrene microplastics through soil. They found that magnetite-coated sand retained the most microplastics, while goethite-coated sand retained the least, with results matching theoretical predictions. The findings suggest that naturally iron-rich soils could serve as effective barriers to prevent microplastic transport through groundwater systems.
Effects of solution chemistry and humic acid on the transport of polystyrene microplastics in manganese oxides coated sand
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Column experiments showed that polystyrene microplastics had significantly lower mobility through manganese oxide-coated sand than bare sand due to electrostatic attraction and surface roughness, with humic acid increasing transport and co-transport with cadmium reducing it.
Co-transport of negatively charged nanoparticles in saturated porous media: Impacts of hydrophobicity and surface O-functional groups
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Researchers studied how graphene oxide (GO) and polystyrene nanoplastics co-transport through saturated soil, finding that in sodium-rich conditions GO can carry nanoplastics through the medium, while calcium ions suppress movement of both by bridging particles to sand grains — with more abundant surface oxygen groups on GO amplifying this effect.
Interplay of compound pollutants with microplastics transported in saturated porous media: Effect of co-existing graphene oxide and tetracycline
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