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Rapid extraction of high- and low-density microplastics from soil using high-gradient magnetic separation.

Ramage, Stuart J.F.F.; Pagaling, Eulyn; Haghi, Reza K.; Dawson, Lorna A.; Yates, Kyari; Prabhu, Radhakrishna; Hillier, Stephen; Devalla, Sandhya

Authors

Eulyn Pagaling

Reza K. Haghi

Lorna A. Dawson

Stephen Hillier

Sandhya Devalla



Abstract

Microplastics (MPs) are present in all environments, and concerns over their possible detrimental effects on flora and fauna have arisen. Density separation (DS) is commonly used to separate MPs from soils to allow MP quantification; however, it frequently fails to extract high-density MPs sufficiently, resulting in under-estimation of MP abundances. In this proof-of-concept study, a novel three-stage extraction method was developed, involving high-gradient magnetic separation and removal of magnetic soil (Stage 1), magnetic tagging of MPs using surface modified iron nanoparticles (Stage 2), and high-gradient magnetic recovery of surface-modified MPs (Stage 3). The method was optimised for four different soil types (loam, high‑carbon loamy sand, sandy loam and high-clay sandy loam) spiked with different MP types (polyethylene, polyethylene terephthalate, and polytetrafluoroethylene) of different particle sizes (63μm to 2mm) as well as polyethylene fibres (2–4mm). The optimised method achieved average recoveries of 96% for fibres and 92% for particles in loam, 91% for fibres and 87% for particles in high‑carbon loamy sand, 96% for fibres and 89% for particles in sandy loam, and 97% for fibres and 94% for particles in high-clay sandy loam. These were significantly higher than recoveries achieved by DS, particularly for fibres and high-density MPs (p<0.05). To demonstrate the practical application of the HGMS method, it was applied to a farm soil sample, and high-density MP particles were only recovered by HGMS. Furthermore, this study showed that HGMS can recover fibre-aggregate complexes. This improved extraction method will provide better estimates of MP quantities in future studies focused on monitoring the prevalence of MPs in soils.

Citation

RAMAGE, S.J.F.F., PAGALING, E., HAGHI, R.K., DAWSON, L.A., YATES, K., PRABHU, R., HILLIER, S. and DEVALLA, S. 2022. Rapid extraction of high- and low-density microplastics from soil using high-gradient magnetic separation. Science of the total environment, [online], 831, article 154912. Available from: https://doi.org/10.1016/j.scitotenv.2022.154912

Journal Article Type Article
Acceptance Date Mar 25, 2022
Online Publication Date Mar 29, 2022
Publication Date Jul 20, 2022
Deposit Date Apr 4, 2022
Publicly Available Date Mar 30, 2023
Journal Science of The Total Environment
Print ISSN 0048-9697
Electronic ISSN 1879-1026
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 831
Article Number 154912
DOI https://doi.org/10.1016/j.scitotenv.2022.154912
Keywords Microplastics; Fibres; Soil; HGMS; Rapid extraction; Electomagnetic
Public URL https://rgu-repository.worktribe.com/output/1632160
Additional Information This accompanying file contains supplementary materials at the end of the main text.