The composite agent of ferrous sulfate, fly ash, and calcium lignosulfonate (FFC) can remediate the soil contaminated by As and Sb under cyclic freeze-thaw (F-T) via stabilization/solidification (S/S). However, the impact of high-frequency F-T cycles on the leaching behavior and migration of As and Sb in FFC-treated soils remains unclear. Here the leaching concentrations, heavy metal speciation (Wenzel's method), and Hydrus-1d simulations were investigated. The results showed that FFC effectively maintained the long-term S/S efficiency of arsenic remediation subject to an extended rainfall and freeze-thaw cycles, and stabilized the easily mobile form of As. The short-term S/S effect on Sb in the remediated soils suffering from F-T cycles was demonstrated in the presence of FFC. In a 20-year span, the mobility of Sb was affected by the number of F-T cycles (FT60 > FT20 > FT40 > FT0) in soil with a depth of 100 cm. As leaching progressed, FFC slowed the upward proportion of adsorbed As fractions but converted parts of the residual Sb to the form of crystalline Fe/Al (hydro) oxide. Moreover, the adsorption rate and capacity of As also preceded that of Sb. Long-term curative effects of FFC could be observed for As, but further development of agents capable of remedying Sb under cyclic F-T and long-term rainfall was needed. The predictive results on the migration and leaching behavior of heavy metals in S/S remediated soils may provide new insight into the long-term assessment of S/S under natural conditions.

中文翻译：

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冻融频率和降雨对铁基复合剂固化固化土中As、Sb金属（类）淋失的影响

硫酸亚铁、粉煤灰和木质素磺酸钙（FFC）复合剂可通过稳定/固化（S/S）循环冻融（FT）修复As、Sb污染的土壤。然而，高频 FT 循环对 FFC 处理土壤中 As 和 Sb 的浸出行为和迁移的影响仍不清楚。这里对浸出浓度、重金属形态（Wenzel 方法）和 Hydrus-1d 模拟进行了研究。结果表明，FFC在延长降雨和冻融循环的情况下有效维持了砷修复的长期S/S效率，并稳定了砷的易移动形式。在 FFC 存在的情况下，证明了经 FT 循环修复的土壤中 Sb 的短期 S/S 效应。在20年的时间跨度内，Sb的迁移率受到100 cm深度土壤中FT循环次数（FT60 > FT20 > FT40 > FT0）的影响。随着浸出的进行，FFC 减缓了吸附 As 部分的上升比例，但将部分残留的 Sb 转化为结晶 Fe/Al（氢）氧化物的形式。此外，As的吸附速率和容量也先于Sb。 FFC对砷的长期疗效可以观察到，但需要进一步开发能够在循环FT和长期降雨下修复锑的药剂。 S/S修复土壤中重金属迁移和淋溶行为的预测结果可能为自然条件下S/S的长期评估提供新的见解。