Interaction Effects of Lead and Cadmium Concentrations on Heavy Metal Accumulation and Transport in Rice

ABSTRACT The co‐contamination of cadmium (Cd) and lead (Pb) in paddy soil poses a significant threat to rice safety. While interactions between Cd and Pb are well‐documented, no prior study has systematically examined their tissue‐specific accumulation and transport dynamics across rice organs. Through pot experiments with varying Cd (1.14, 1.95, and 3.87 mg kg −1 ) and Pb (55.75, 105.71, and 244.59 mg kg −1 ) treatments, we demonstrate that Pb250 (244.59 mg kg −1 ) substantially enhanced Cd accumulation in all rice tissues. Notably, brown rice Cd reached 0.51 mg kg −1 under Cd2Pb250, exceeding China's safety limit (0.2 mg kg −1 ) by 155%. Root Cd content peaked at 51.02 mg kg −1 under Cd4Pb250, while Pb increased Cd transport in vascular tissues (internodes/nodes) by 54%. In contrast, Pb accumulation was concentrated in the roots (1125 mg kg −1 under Pb250) but remained below 0.15 mg kg −1 in grains. This study represents the first comprehensive quantification of Cd–Pb antagonism and synergism effects across 14 rice tissues, providing critical mechanistic insights into Pb's role in exacerbating Cd grain translocation and informing targeted remediation strategies for co‐contaminated paddies.