| In order to reveal the effects of aging of immobilization materials on the stability of soil cadmium (Cd) immobilization, three types of acidic paddy soils of Hechi, Xiangtan and Shaoguan were selected, and a 308 days soil cultivation experiment was carried out in the greenhouse. Each experiment site was set up with a control treatment and two treatments with sepiolite and biochar, respectively. The experiment was performed to study the changes of soil Cd fractions in the paddy soils of Hechi, Xiangtan and Shaoguan, and pearson correlation between the forms of soil Cd, iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn). The results showed that after application of sepiolite, the content of acid-extractable Cd in the soil of Hechi, Xiangtan, and Shaoguan showed a downward trend in the early stage of soil cultivation and an upward trend in the later stage of soil cultivation Specifically, the ratio of acid-extracted Cd to total Cd in Hechi soil decreased by 9.0 % from 0 to 28 days, and increased by 13.8% from 28 to 308 days. Similarly, the percentage of acid-extracted Cd in Xiangtan and Shaoguan soil decreased by 3.2% and 4.4% from 0~7 days, respectively, and increased by 2.1% and 3.5% from 7~308 days, respectively. The content of acid-extracted Cd in the soil of Hechi, Xiangtan, and Shaoguan also showed a trend of decreasing first and then increasing with regard to soil applied by biochar. In 0~7 days, the ratio of soil acid-extracted Cd to total Cd in the three test sites decreased by 5.6~8.1 %, and increased by 3.4~6.6 % in 7~308 days. In addition, compared with the application of sepiolite, the application of biochar had a strong correlation between the changes of Cd, Fe, Mn morphology in the soil During the 308 days soil cultivation process, pearson correlation analysis showed that after applying sepiolite or biochar, the same morphological changes of Cd, Zn, and Cu in the soils of Hechi, Xiangtan, and Shaoguan were significantly positively correlated (P<0.05), and extremely significantly positively correlated (P<0.01) or no significant correlation. The conclusions were as following: After the application of sepiolite or biochar, Cd in the paddy soils of Hechi, Xiangtan and Shaoguan was reactivated and re-released as time went on, and the aging of sepiolite and biochar significantly affected the morphological changes of Cd in the paddy soil of Hechi, Xiangtan and Shaoguan. Besides, there was no significant negative correlation between the same form of Cd and Zn and Cu in paddy soil. |
