Near-Complete Decomposition of Soil Microplastics over Transient Electrical Heating and Associated Benefits

Abstract Soil serves as a significant sink for microplastics, posing considerable risks to both the ecological and human health. The diverse composition and dynamic transformation of microplastics present major challenges for remediation as conventional strategies often fail to achieve efficient and complete decomposition. In this study, biochar was applied to microplastic-contaminated soil as a conductive material to initiate transient electric heating under a low-power input. This approach facilitated near-complete decomposition of soil microplastics (>95.0%) across the tested soil and microplastic types while preventing soil hardening. Specifically, electric heating enhanced interactions between soil microplastics and the biochar conductor, leading to the formation of highly aromatic carbon (HAC). The resulting HAC not only improved soil microecology but also supported the growth of pak choi (Brassica campestris L. ssp.). The newly formed HAC was found to upregulate the expression of auxin-responsive gene families, including Aux/IAA and GH3, in the roots. HAC enriched tryptamine in the rhizosphere, and tryptamine abundance was positively correlated with the relative abundance of Sphingomonas, a genus with a reported capacity to convert tryptamine-derived intermediates toward indole-3-acetic acid (IAA) biosynthesis. These findings demonstrate that transient electric heating offers a sustainable strategy for decomposing diverse soil microplastics and that the remediated soil remains safe and conducive for agricultural production.