To study the dynamic characteristics, aging factors and its’ influence factors of Cd added to paddy soil, five kinds of paddy soil with various properties were collected, the soils were artificially polluted by cadmium with 6 different addition levels. A pot experiment was performed to investigate the Cd phytotoxicity to the rice growth characterised with different sensitivity to Cd stress in paddy soils, meanwhile, the effect of five ageing times (i.e. 14d, 30d, 60d, 90d and 180d) on the Cd phytotoxicity was investigated using Log-logistic dose-response distribution model. The results showed that the content of the 0.05mol/L EDTA-2Na extracted Cd decreased with the increasing of the aging time in all the soils, the maximum decrement of the 0.05mol/L EDTA-2Na extracted Cd ranged from 21.5% (for the red soil) to 38.0% (for the black soil) respectively, as compared with the treatment of 14d-incubation time. After aging for 90d, the adsorption of Cd in the soil solution reached the slow reaction stage. According to the fitting parameters of the two-order kinetics equation, the aging of Cd in soil was characterized with the extracted Cd content decreased fast in 30d to 60d stage, then the process became slow and reached the balance in the soil solution after 90d incubation. The analysis of the correlation between the kinetic equation parameters (C∞ andK2) and soil properties indicated that, soil pH was the main control factors affecting the fraction of bio-available Cd content in soils, followed by soil CEC and OC content. The 50%inhibiting concentration (EC50) of Cd toxicity to rice growth increased significantly (P<0.05) with the aging time in soils, the EC50 of the treatments with 180d ageing time increased 72.1% to 195.0% as compared with the treatments of 14d aging time. The effects of soil pH on the Cd aging processes decreased gradually, and the influence of CEC increased gradually in the long-term ageing greater than the treatment of 90d, however, the key factor that affecting the Cd ageing process in the soil was still the soil pH, and no effect of the selected rice cultivars on the Cd ageing process was observed in the soils for this study.%选择5种不同性质的水稻土,通过外源添加制备了6个不同浓度梯度的Cd污染土壤,研究了外源Cd在几种水稻土中的老化动力学特征与影响因子；同时利用盆栽实验,结合Log-logistic分布模型,研究了5个不同老化时间(14、30、60、90和180d)与土壤中Cd对二种不同Cd敏感性水稻生长毒性的影响.结果表明,不同浓度外源Cd进入土壤后,0.05mol/L EDTA-2Na浸提的有效态Cd含量随着老化时间的增加而逐渐下降；与14d处理相比,老化30d后土壤中有效态Cd降幅达21.5%(红壤)~38.0%(黑土)；老化90d后,土壤中Cd进入慢反应阶段.基于二级动力学方程的拟合参数显示,土壤中Cd的老化特征表现为有效态Cd含量在30~60d内快速降低,随后变化减缓,经过90d的老化后,土壤中有效态Cd含量逐渐趋于平衡.基于老化动力学方程参数(C∞及K2)与土壤性质间的相关性分析表明,土壤pH值是影响Cd有效态含量变化的主控因子,其次是土壤 CEC 和 OC 含量.在不同性质土壤中,随着老化时间的增加,土壤中外源 Cd 对水稻生长毒性的半抑制浓度(EC50)值显著升高；与14d老化处理相比,经过180d老化后土壤中Cd对水稻生长毒性的EC50增加72.1%~195.0%；在大于90d的长期老化过程中,土壤pH值对Cd老化过程的影响逐渐降低,而CEC的影响逐渐上升,尽管如此,土壤中Cd老化过程的主要影响因子仍然是土壤pH,而与测试的2种水稻品种无关.
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