Deciphering Cd Stabilization Pathways by Organosilicon in Soil-Pakchoi Systems Through Isotope-Tracing

Cadmium (Cd) pollution in farmland soils threatens food safety, making it essential to study soil-crop Cd transport mechanisms and develop remediation strategies. While organosilicon-modified materials demonstrate potential in blocking metal uptake by crops, their underlying mechanisms remain underexplored. This study employed stable isotope 114 Cd tracing to investigate Cd absorption, translocation, allocation in soil-pakchoi system mediated by organosilicon (DMDCS and D6). Results revealed that organosilicon induced Cd redistribution in soils, enhancing its sequestration into non-reactive fractions. Specifically, DTPA-Cd decreased by 13.14-24.19%, while RES-Cd increased by 70.3-106.8%. Organosilicon also inhibited Cd uptake and translocation in pakchoi, reducing root and shoot Cd concentrations by 30.0-33.2% and 54.6-57.1%, respectively, with a 35% decline in translocation factor (TF). This reduction stemmed from diminished Cd accumulation (12.09-17.73% decrease) in soluble subcellular fractions. Among the plant parts, Cd isotopes were markedly fractionated: shoots were isotopically heavier than roots. Silicone application attenuated this fractionation intensity, with Δ 114/110 Cd shoot-root decreased from 0.33 to 0.08. We suggest that organosilicon suppressed the enrichment of exogenous isotopes in plant edible parts due to a 28.1% decrease in Cd isotope exchangeability (E- value) and vacuolar compartmentalization. This study provides new insights into organosilica-mediated Cd dynamics in pakchoi, laying the foundation for future Cd regulation strategies.