Summary
This laboratory study examined how Lumbricus terrestris earthworms influence the vertical transport of low-density polyethylene microplastics in sandy soil columns. Earthworms were shown to ingest microplastics from the soil surface and transport them to deeper layers, with a preferential accumulation of smaller particles (<250 µm) at greater depths. Microplastics were only detected in leachate from treatments containing earthworms, suggesting that earthworm burrow networks facilitate preferential flow pathways that enhance microplastic mobilisation toward groundwater.
UK applicability
The findings have direct relevance to UK soil and groundwater contamination risks, particularly in regions with shallow water tables and high earthworm populations. UK agricultural and environmental regulators should consider these pathways when assessing microplastic fate in soils and potential entry routes into drinking water systems.
Key measures
Microplastic particle size distribution (1 mm–250 µm, 250 µm–150 µm, <150 µm), microplastic concentration in soil layers by depth, saturated hydraulic conductivity (Ksat), microplastic detection in leachate samples
Outcomes reported
The study measured microplastic (LDPE) distribution and concentration across soil layers in laboratory columns under different conditions, and determined whether microplastics could be mobilised and transported via water leaching in the presence of earthworm activity.
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