Biochar Reduces Nanoplastics Uptake by Lettuce and Alleviates Its Toxicity to the Plant

The accumulation of micro- and nanoplastics (MPs/NPs) in croplands threatens food quality and human health. This study investigates the effectiveness of pristine biochar (BC) and iron-doped biochar (Fe-BC), produced from pine sawdust via one-step pyrolysis, in reducing NPs uptake by lettuce (Lactuca sativa L. var. adela). Fe-BC exhibited greater porosity, higher surface area, and a slightly positive surface charge compared to BC. Using Pd-doped NPs, we confirmed that NPs can penetrate roots and translocate to leaves, accumulating more in older tissues. Soil application of 3 wt % BC or Fe-BC significantly lowered leaf NPs concentrations, with Fe-BC showing a greater reduction, by approximately 60% (from 0.90 to 0.36 mg/kg). While both BC and Fe-BC demonstrated a capacity for alleviating NPs-induced metabolic disturbances and partially restoring soil enzyme activities, Fe-BC presents a more promising amendment for mitigating NPs contamination and protecting crop quality.