Humic substances (HSs), as electron shuttles, are associated with iron oxide transformation, yet the manner by which HSs affect Cd/As availabilities during this process under anaerobic conditions remains unclear. Two HSs (humic sodium, HA-Na, and biochemical fulvic acid, BFA) were applied at 0, 1, 2, and 4 g C kg⁻¹ in a submerged incubation experiment. The dissolved, extractable and fractions of Cd/As and different iron oxides in soils were monitored. The addition of both HA-Na and BFA decreased the CaCl₂-extractable Cd by 12.66–93.13%, and increased the KH₂PO₄-extractable As by 18.81–71.38% on the 60th day of incubation. The soil Eh and crystalline iron oxides (Fed) decreased, while amorphous iron oxides (Feo) and dissolved As increased after addition of both HSs. However, the two HSs had opposite effects on soil pH and dissolved Cd at the end of the incubation. HA-Na immobilized 19.47–85.99% more available Cd than did BFA over the incubation, although the extent of immobilization was similar with the maximum application rate on the 60th day. BFA mobilized 5.22–26.12% more available As than did HA-Na. XPS data showed that FeOOH decreased while the FeO component increased over the incubation. Correlation analysis and SEM showed that the reduction in the soil Eh and Fed and relative increase in Feo increased the available Cd, while decreased the available As. Consequently, the addition of HA-Na and BFA, particularly combined with flooding irrigation management, could effectively reduce the available Cd in Cd-contaminated soil. However, this method should be used with caution in As-contaminated soil.

腐殖质 (HS) 作为电子穿梭机，与氧化铁转化有关，但在厌氧条件下，HS 在此过程中影响 Cd/As 可用性的方式仍不清楚。在浸没孵育实验中，以 0、1、2 和 4 g  C  kg ^-1施用两种 HS（腐殖酸钠、HA-Na 和生化富里酸，BFA）。监测土壤中 Cd/As 和不同氧化铁的溶解、可提取和分数。HA-Na 和 BFA 的添加使 CaCl _{2 可}萃取的 Cd降低了12.66–93.13%，并增加了 KH ₂ PO ₄- 在孵化第 60 天可提取 18.81–71.38% 的砷。添加两种HS后，土壤Eh和结晶氧化铁（Fed）减少，而无定形氧化铁（Feo）和溶解As增加。然而，两种 HS 对培养结束时土壤 pH 值和溶解的 Cd 有相反的影响。在孵育过程中，HA-Na 比 BFA 固定了 19.47–85.99% 的可用 Cd，尽管固定程度与第 60 天的最大施用率相似。BFA 比 HA-Na 动员了 5.22–26.12% 的可用 As。XPS 数据显示 FeOOH 减少，而 FeO 组分在孵育过程中增加。相关性分析和扫描电镜表明，土壤 Eh 和 Fed 的减少和 Feo 的相对增加增加了有效 Cd，同时减少了有效 As。因此，添加 HA-Na 和 BFA，特别是结合漫灌管理，可以有效降低镉污染土壤中的有效镉。然而，这种方法在被砷污染的土壤中应谨慎使用。