Developing a systematic method for extraction of microplastics in soils

Radford, Freya; Zapata-Restrepo, Lina M.; Horton, Alice A.; Hudson, Malcolm D.; Shaw, Peter J.; Williams, Ian D.

Abstract

Microplastics are an environmental issue of global concern. Although they have been found in a range of environments worldwide, their contamination in the terrestrial environment is poorly understood. The lack of standardised methods for their detection and quantification is a major obstacle for determining the risk they pose to soil environments. Here we present a systematic comparison of microplastic extraction methods from soils, taking into account the characteristics of the soil medium to determine the best methods for quantification. The efficiency of organic matter removal using hydrogen peroxide, potassium hydroxide and Fenton's reagent was measured. Soils with a range of particle size distribution and organic matter content were spiked with a variety of microplastic types. Density separation methods using sodium chloride, zinc chloride and canola oil were tested. Recovery efficiencies were calculated and the impact of the reagents on the microplastics was quantified using Attenuated Total Reflectance (ATR) Fourier Transform-Infrared (FTIR) spectroscopy. The optimal organic removal method was found to be hydrogen peroxide. The recovery efficiency of microplastics was variable across polymer types. Overall, canola oil was shown to be the optimal method for density separation, however, efficiency was dependent on the amount of organic matter in the soil. This outcome highlights the importance of including matrix-specific calibration in future studies considering a wide range of microplastic types, to avoid underestimation of microplastic contamination. We show here that methods for extracting microplastics from soils can be simple, cost-effective and widely applicable, which will enable the advancement of microplastic research in terrestrial environments.

• Journal Article Type: Article
• Acceptance Date: Mar 8, 2021
• Online Publication Date: Mar 21, 2021
• Publication Date: Apr 14, 2021
• Deposit Date: Jan 25, 2023
• Publicly Available Date: Jan 25, 2023
• Journal: Analytical Methods
• Print ISSN: 1759-9660
• Electronic ISSN: 1759-9679
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 13
• Issue: 14
• Pages: 1695-1705
• DOI: https://doi.org/10.1039/d0ay02086a
• Keywords: General Engineering; General Chemical Engineering; Analytical Chemistry
• Public URL: https://uwe-repository.worktribe.com/output/10382211
• Publisher URL: https://pubs.rsc.org/en/content/articlelanding/2021/AY/D0AY02086A
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Freya Radford (ORCID); : Alice A. Horton (ORCID); : Ian D. Williams (ORCID); : Single-blind; : Received 10 November 2020; Accepted 8 March 2021; Advance Article published 22 March 2021; Version of Record published 15 April 2021