Nanoconfined humic acid-supported nZVI enhances imidacloprid remediation without compromising soil microbiome or...

Pesticide contamination of agricultural soils poses persistent risks to ecosystem function and agricultural sustainability, yet the application of reactive nanomaterials for remediation remains constrained by physicochemical instability and uncertain ecological consequences. Here, we synthesized a nanoconfined humic acid-supported nZVI composite (HA-nZVI) and evaluated its performance in imidacloprid (IMI)-contaminated soil through kinetic analysis, interfacial characterization, metagenomic sequencing, and dual-framework ARG risk assessment. HA nanoconfinement improved particle dispersion, increased active-site accessibility, and facilitated interfacial electron shuttling. These effects accelerated predominantly abiotic IMI dissipation, raising the degradation rate by 3.8-fold relative to the unamended control and shortening the half-life to 18.56 d. Despite the accelerated removal, dominant phylum-level abundances fluctuated by less than 3%, suppression of plant-beneficial bacteria (PBB) observed with pristine nZVI was alleviated, and no measurable increase in human- or livestock-associated ARG risk was detected among the 525 identified ARG subtypes. Collectively, these findings show that HA nanoconfinement can couple improved pesticide dissipation with phylum-level microbiome compatibility and no detectable increase in resistome-associated health risk, supporting the design of iron-based nanomaterials for sustainable agricultural remediation.