Impact of coconut-fiber biochar on lead translocation, accumulation, and detoxification mechanisms in a soil–rice system under elevated lead stress

Biochar, an environmentally friendly material, was found to passivate lead (Pb) in contaminated soil effectively. This study utilized spectroscopic investigations and partial least squares path modeling (PLS-PM) analysis to examine the impact of coconut-fiber biochar (CFB) on the translocation, accumulation, and detoxification mechanisms of Pb in soil-rice systems. The results demonstrated a significant decrease (p<0.05) in bioavailable Pb concentration in paddy soils with CFB amendment, as well as reduced Pb concentrations in rice roots, shoots, and brown rice. Synchrotron-based micro X-ray fluorescence analyses revealed that CFB application inhibited the migration of Pb to the rhizospheric soil region, leading to reduced Pb uptake by rice roots. Additionally, the CFB treatment decreased Pb concentrations in the cellular protoplasm of both roots and shoots, and enhanced the activity of antioxidant enzymes in rice plants, improving their Pb stress tolerance. PLS-PM analyses quantified the effects of CFB on the accumulation and detoxification pathways of Pb in the soil–rice system. Understanding how biochar influences the immobilization and detoxification of Pb in soil–rice systems could provide valuable insights for strategically using biochar to address hazardous elements in complex agricultural settings. Lead (Pb) exposure poses a serious risk to public health. Little information is available to integrally delineate the biochar effect on Pb translocation, accumulation, and detoxification mechanisms in a soil–rice system exposed to elevated Pb stress. Synchrotron-based micro X-ray fluorescence spectroscopy and partial least squares path modeling analysis were conducted to investigate the mechanisms underlying Pb immobilization and detoxification in paddy soil amended with coconut-fiber biochar. The results advanced our understanding that biochar application effectively passivated Pb in soil inhibiting its migration to the rhizospheric soil region, diminishing Pb uptake, thus limiting Pb accumulation in cellular protoplasm.