Nanoplastic Transport in Soil via Bioturbation by Lumbricus terrestris
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Date
2021-12-21
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Journal Article
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Abstract
Plastic pollution is increasingly perceived as an emerging threat to terrestrial environments, but the spatial and temporal dimension of plastic exposure in soils is poorly understood. Bioturbation displaces microplastics (>1 μm) in soils and likely also nanoplastics (<1 μm), but empirical evidence is lacking. We used a combination of methods that allowed us to not only quantify but to also understand the mechanisms of biologically driven transport of nanoplastics in microcosms with the deep-burrowing earthworm Lumbricus terrestris. We hypothesized that ingestion and subsurface excretion drives deep vertical transport of nanoplastics that subsequently accumulate in the drilosphere, i.e., burrow walls. Significant vertical transport of palladium-doped polystyrene nanoplastics (diameter 256 nm), traceable using elemental analysis, was observed and increased over 4 weeks. Nanoplastics were detected in depurated earthworms confirming their uptake without any detectable negative impact. Nanoplastics were indeed enriched in the drilosphere where cast material was visibly incorporated, and the reuse of initial burrows could be monitored via X-ray computed tomography. Moreover, the speed of nanoplastics transport to the deeper soil profile could not be explained with a local mixing model. Earthworms thus repeatedly ingested and excreted nanoplastics in the drilosphere calling for a more explicit inclusion of bioturbation in nanoplastic fate modeling under consideration of the dominant mechanism. Further investigation is required to quantify nanoplastic re-entrainment, such as during events of preferential flow in burrows.
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published
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Journal / series
Volume
55 (24)
Pages / Article No.
16423 - 16433
Publisher
American Chemical Society
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Subject
Microplastic; transport; fate; exposure; X-ray computed tomography; earthworms
Organisational unit
09717 - Mitrano, Denise M. (ehemalig) / Mitrano, Denise M. (former)
Notes
Funding
168105 - The path of microplastics to the environment: fate and transport in waste water treatment systems (SNF)
186856 - Synthesis and utility of metal-doped plastic particles and fibers: from analytical standardization to systematic understanding of fate in the environment (SUrPASS) (SNF)
186856 - Synthesis and utility of metal-doped plastic particles and fibers: from analytical standardization to systematic understanding of fate in the environment (SUrPASS) (SNF)