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Microplastic contamination in biomined recovered soils: Estimation, characterization, chemical ageing verification, and ecological risk implication for agricultural use
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Soil recovered from processing old landfill waste (often reused as farm fertilizer) contains thousands of tiny plastic particles per kilogram, with the smallest fragments being especially abundant. Since this soil is being spread on agricultural land, these microplastics could work their way into crops, water, and eventually our food supply, yet there are currently no safety standards checking for this contamination before it's used. The findings suggest we need better testing and regulations before this "recycled" soil gets approved for farming.
Plastic waste constitutes a substantial portion of municipal solid waste (MSW). Improper disposal and inadequate management of MSW have resulted in the accumulation of legacy waste, generating toxic leachate and landfill gases. To mitigate these challenges, biomining emerged as an effective approach. Biomining involves the stabilization/excavation and segregation of legacy waste into reusable byproducts, including recovered soil. This recovered soil is often used as an agricultural amendment; however, it may contain microplastics (MPs) from the degradation of plastic waste. Consequently, its use could facilitate the spread of microplastics. Given the limited understanding of this pathway, this study investigates MPs in Biomined recovered soil, evaluates their ageing, and the associated ecological risks of applying such soil as an amendment. The Biomined recovered soil samples were collected from the Gandhinagar dumpsite, homogenized, and Fenton-digested. MPs were separated by saturated NaCl solution, visualization using a stereomicroscope and identification by Fourier-transform infrared spectroscopy. Results show that Biomined recovered soil contained 7,633 ± 208 small (<1 mm) and 1,100 ± 150 large (1–5 mm) MPs/kg, with <0.2 mm particles dominating the small MPs fraction and 1–2 mm particles dominating the large MPs fraction. Fragments predominated among both small (39%) and large (38%) MPs. A total of nine polymer types were identified, with polyethylene terephthalate and polypropylene being the most prevalent. Chemical ageing analysis indicated significant degradation in polyurethane. Abundant small MPs posed a significant ecological threat, highlighting the need for MPs monitoring and regulatory standards before using biomined recovered soil as agriculture amendment.
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Researchers measured microplastic contamination in topsoil at a former waste dump site in India after biomining remediation and found an average of approximately 114,000 microplastics per kilogram of soil. Fragment-shaped particles dominated the samples, composed mainly of polyethylene and polypropylene, and the common plasticizer di-n-butyl phthalate was also detected, raising concerns about the environmental safety of land recovered through biomining.
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