Nanoscale zero-valent iron increases rice grain quality and suppresses polychlorinated biphenyl accumulation

Abstract

Iron-based nanoparticles (FeNPs) have shown significant potential for sustainable agriculture; however, previous evidence primarily focused on iron-mediated soil remediation through rhizosphere interactions, while the influence of FeNPs on the physio-biochemical processes of aboveground crops and their contribution to pollutant control remain unclear. This study compared the beneficial effects of commonly applied iron oxide NPs and nanoscale zero-valent iron (nZVI) on soil and rice under 2,4,4′-trichlorobiphenyl (PCB28) contamination, with an emphasis on the biological responses of aboveground crop parts. The results identified 100 mg kg⁻¹ nZVI with a particle size of approximately 100 nm (nZVI₁₀₀) as the optimal amendment, enhancing PCB28 removal in soil by 16.4% while increasing the grain yield by 52.9%. Histological analysis revealed that 100 mg kg⁻¹ nZVI₁₀₀ treatment increased the lipid layer of rice stems by 58.5%, which promoted the enrichment of PCB28 in the stem and reduced its accumulation in the whole aboveground part, and the stem-to-leaf translocation factor decreased from 2.16 in the control group to 0.57, inhibiting PCB28 upward migration. Additionally, nZVI₁₀₀ improved grain quality by reducing tricarboxylic acid cycle intermediates and increasing proline content, which enhanced storage properties. The change of metabolites including increased grain vitamins and aromatic compounds along with improved softness (as reflected by gel consistency) could enhance the flavor and nutritional value of grains, and was expected to increase the economic value of agricultural products. These findings demonstrate that nZVI effectively mitigates PCB28 accumulation and toxicity, while simultaneously enhancing rice quality, highlighting its potential for advancing high-quality agricultural practices.