Quantitative Source Apportionment and Transfer Mechanism of Pb in Different Compartments of Soil-Wheat System: A Fresh Insight from Pb Isotopic Composition, Fractionation and Inverse Distance Weightings.

Abstract

Lead (Pb) pollution has always been a persistent and unresolved environmental issue of great concern. This study innovatively applied Pb isotopic compositions and inverse distance weighting (IDW) to quantitatively identify Pb source contributions in the soil-wheat system in Kaifeng, China. Results showed Pb concentrations followed as soil > root > stem > shell > grain, with 18.2% of grains exceeding the National food safety standard (0.2 mg kg⁻¹). Quantitative source identification displayed atmospheric deposition contributed 66.82%, 66.32% and 63.00% to grains, leaves and shells, respectively, while sewage irrigation accounted for 67.74%, 58.61% and 57.56% in roots, stems and soils. Lighter Pb isotopes from atmospheric deposition were more readily absorbed by leaves and enriched in grains, whereas roots and stems retained heavier isotopes from sewage irrigation, effectively blocking their migration to grains and reducing health risks. This study provides valuable insights into Pb uptake, migration, and mechanisms in the soil-wheat system. It is commended reasonable regulation of rhizosphere soil and atmospheric environment or physiological interference on wheat growth might be an effective way to reduce the risk of Pb enrichment in wheat grains.