Chemical immobilization is a practical approach to remediate heavy metal contamination in agricultural soils. However, the potential remobilization risks of immobilized metals are a major environmental concern, especially in acid rain zones. In the present study, changes in the immobilization efficiency of several amendments as affected by simulated soil acidification were investigated to evaluate the immobilization remediation stability of several amendments on two cadmium (Cd) contaminated soils. Amendments (hydrated lime, hydroxyapatite and biochar) effectively immobilized Cd, except for organic fertilizer, and their immobilizations were strongly decreased by the simulated soil acidification. The ratio of changes in CaCl₂-extractable Cd: pH (△CaCl₂-Cd/△pH) can represent the Cd remobilization risk of different amended soils. Hydroxyapatite and biochar had a stronger durable immobilizing effect than did hydrated lime, particularly in soil with a lower pH buffering capacity, which was further confirmed by the Cd concentration and accumulation in lettuce. These results can be attributed to that hydroxyapatite and biochar transformed greater proportions of exchangeable Cd to other more stable fractions than lime. After 48 weeks of incubation, in soil with a lower pH buffering capacity, the immobilization efficiencies of lime, hydroxyapatite, biochar and organic fertilizer in the deionized water group (pH 6.5) were 71.7%, 52.7%, 38.6% and 23.9%, respectively, and changed to 19.1%, 33.6%, 26.5% and 5.0%, respectively, in the simulated acid rain group (pH 2.5). The present study provides a simple method to preliminarily estimate the immobilization efficiency of amendments and predict their stability in acid rain regions before large-scale field application. In addition, hydrated lime is recommended to be combined with other acid-stable amendments (such as hydroxyapatite or biochar) to remediate heavy metal-contaminated agricultural soils in acid precipitation zones.

化学固定化是补救农业土壤中重金属污染的实用方法。但是，固定化金属的潜在迁移风险是一个主要的环境问题，尤其是在酸雨地区。在本研究中，研究了几种改良剂的固定化效率受模拟土壤酸化影响的变化，以评估几种改良剂在两种受镉（Cd）污染的土壤上固定化修复的稳定性。修正剂（熟石灰，羟基磷灰石和生物炭）有效地固定了Cd（有机肥除外），并且通过模拟土壤酸化作用，其固定率大大降低。CaCl ₂萃取性Cd：pH的变化率（△CaCl _2）-Cd /△pH）可以代表不同改良土壤中Cd迁移的风险。羟基磷灰石和生物炭具有比熟石灰更强的持久固定作用，尤其是在pH缓冲能力较低的土壤中，这可以通过生菜中Cd的浓度和积累得到进一步证实。这些结果可以归因于羟基磷灰石和生物炭将更大比例的可交换镉转化为比石灰更稳定的馏分。孵育48周后，在pH缓冲能力较低的土壤中，去离子水组（pH 6.5）中石灰，羟基磷灰石，生物炭和有机肥料的固定效率分别为71.7％，52.7％，38.6％和23.9％。 ，并且在模拟酸雨组（pH 2.5）中分别更改为19.1％，33.6％，26.5％和5.0％。本研究提供了一种简单的方法，可以在大规模现场应用之前，初步估算修饰剂的固定化效率并预测其在酸雨地区的稳定性。此外，建议将熟石灰与其他酸稳定的改良剂（例如羟磷灰石或生物炭）结合使用，以修复酸沉淀区中重金属污染的农业土壤。