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Retention mechanisms of microplastics in soil environments during saturation-desaturation cycles: Impact of hydrophobicity and pore geometry
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This study used tiny lab models of soil pores to examine how microplastics get trapped in soil depending on their water-repelling properties and the shape of soil passages. More water-repellent microplastics stuck more firmly to surfaces and were retained at higher rates, up to 50% in some conditions. Understanding how microplastics move through soil is important for predicting whether they will reach groundwater or stay trapped near the surface where they can affect crops.
Forming ubiquitous contaminants in sediments, microplastics (MPs) are of growing concern due to their rapid infiltration into the environment and detrimental effects on ecosystems and human health. Understanding MP transport dynamics in pore networks is essential for predicting their mobility in sediments and soils and developing strategies to mitigate their spread. This study examines how pore geometry and MP hydrophobicity affect retention mechanisms within porous media during saturation-desaturation cycles. Microfluidic experiments were conducted using micromodels representing porous media with varied pore characteristics. MPs with hydrophilic, hydrophobic, and mixed hydrophobicity properties were introduced into these micromodels, and high-resolution imaging analyzed their retention patterns. The results reveal distinct retention behaviors based on MP hydrophobicity and pore geometry. Hydrophilic MPs were retained through clustering and sieving within smaller throats, particularly in low-connectivity geometries, with retention reaching 25 %. Hydrophobic MPs attached strongly to the solid-water interface (SWI) during saturation and shifted to the air-water interface (AWI) during desaturation, achieving retention rates up to 40 % in high-connectivity geometries. Mixed MPs exhibited combined behaviors, with early SWI attachment and subsequent clustering and sieving, resulting in retention rates as high as 50 % in geometries with high specific surface areas. These findings highlight the role of pore geometry and MP surface properties in determining retention and mobility. Hydrophilic MPs form contamination hotspots in fine-grained sediments, while hydrophobic MPs are more mobile in high-connectivity environments. Mixed MPs persist due to multiple retention mechanisms, posing challenges for remediation. This study informs strategies to manage MP contamination in subsurface environments.
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Behaviour and transport of microplastics under saturated flow conditions in sediments and soils
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Researchers investigated the behaviour and transport of microplastics under saturated flow conditions in sediments and soils, examining how particle properties influence movement through porous media. The study aimed to improve understanding of subsurface microplastic fate and transport relevant to both soil and groundwater contamination.
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Researchers investigated how microplastic particles in soil affect the soils water repellency and hydraulic properties. They found that microplastics can significantly increase water repellency in soil, which reduces water infiltration and alters moisture dynamics. These changes could have important consequences for crop growth and groundwater recharge in microplastic-contaminated agricultural soils.
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