This study aimed to determine the leaching mechanism of cadmium (Cd) from contaminated soil by nitrilotriacetic acid (NTA). ¹¹⁴Cd/¹¹⁰Cd isotope technology was adopted as the main characterization method, and experiments were conducted with a typical high-Cd soil to determine the speciation distribution of Cd, isotopic composition, and changes in bonding environment before and after leaching. The speciation distribution of Cd in the soil before leaching in order from most to least was exchangeable Cd, iron‑manganese oxide Cd, residual Cd, carbonate-bound Cd, and organic fraction Cd. The removal efficiency of exchangeable Cd was the highest, followed by iron‑manganese oxide Cd and carbonate-bound Cd. Residual Cd and organic fraction Cd content did not significantly change. Cd(NTA)⁻ and Cd(NTA)₂⁴⁻ were the major species of Cd in the leaching reagent, which was enriched in the heavy isotope ¹¹⁴Cd and had a strong bonding environment. The isotope fractionation coefficient α decreased as the proportion of Cd remaining in the soil decreased. Cd speciation distribution had an important influence on the ¹¹⁴Cd/¹¹⁰Cd fractionation degree in the leaching process. The Cd isotope composition in soil (from −0.12‰ ~ 0.04‰ to −0.35‰ ~ −0.18‰ without buffer and − 0.28‰ ~ −0.09‰ with buffer) can reflect the change of Cd speciation distribution, which determines the characteristics of the bonding environment and, in turn, determines the efficiency of NTA leaching to remove soil Cd. As such, isotope fractionation characteristics can be a significant theoretical support related to NTA leaching Cd contaminated soil.

本研究旨在确定次氮基三乙酸 (NTA) 从污染土壤中浸出镉 (Cd) 的机制。^以114 Cd/ ¹¹⁰ Cd同位素技术为主要表征方法，以典型的高Cd土壤为实验对象，确定浸出前后Cd的形态分布、同位素组成以及结合环境的变化。浸出前土壤中Cd的形态分布从高到低依次为交换性Cd、铁锰氧化物Cd、残留Cd、碳酸盐结合Cd和有机组分Cd。可交换Cd的去除效率最高，其次是铁锰氧化物Cd和碳酸盐结合Cd。残留 Cd 和有机组分 Cd 含量没有显着变化。镉(NTA)^-和Cd(NTA) ₂ ^4-是浸出剂中Cd的主要种类，富含重同位素¹¹⁴ Cd，具有较强的成键环境。同位素分馏系数α随着残留在土壤中的Cd比例的降低而降低。Cd 形态分布对¹¹⁴ Cd/ ¹¹⁰浸出过程中镉的分馏度。土壤中Cd同位素组成（从-0.12‰～0.04‰到-0.35‰～-0.18‰无缓冲和-0.28‰～-0.09‰有缓冲）可以反映Cd形态分布的变化，这决定了土壤的特征粘合环境，进而决定了 NTA 浸出去除土壤 Cd 的效率。因此，同位素分馏特征可以成为与 NTA 浸出 Cd 污染土壤相关的重要理论支持。