Anaerobic situation induced by long-term flooding of paddy soils makes dissimilatory iron (Fe) reduction and Arsenic (As) reduction in pore water. In our research, different dosage of nitrate (1 and 20 mmol NO₃⁻ kg⁻¹ soil, LN and HN, respectively) were used as amendments for As immobilization. The effect on soil properties such as pH, Eh, sulfate, and nitrate; the effect on As(III) and dissimilatory iron reduction and the effect on microbial community structure were investigated. Our results showed that With the addition of nitrate, the reduction of Eh was accelerated. Especially for HN, the Eh decreased from 139 to 40 mV in 30 days, is higher than Eh in original soil (CK). The dissimilatory iron reduction was significantly depressed by the addition of nitrate, Fe²⁺ in nitrate amendments are much less than control, especially for HN, Fe²⁺ concentration was 62.58% lower than control. While Final As(III) concentrations were 284.67, 223.87, and 190.70mg Kg⁻¹ for CK, LN, and HN treatments, respectively. In both LN and HN, the concentration of NO₃⁻ faded with incubation time, which means that NO₃⁻ could act as an electron acceptor instead of Fe³⁺ and As(V). Moreover, nitrate has selectivity for microbes, while the abundance of Clostridia and Geobacteraceae, which play a major role in the reduction of dissimilatory iron, is strongly inhibited, thereby inhibiting the process of dissimilatory iron reduction. Our results showed that by promotion of decreasing Eh, inhibition dissimilatory iron reduction, and Arsenic speciation transformation, nitrate could act as an effective amendment for As immobilization in paddy soils.

稻田长期淹水引起的厌氧情况使孔隙水中的异化铁（Fe）和砷（As）减少。在我们的研究中，不同剂量的硝酸盐（分别为 1 和 20 mmol NO ₃ ^- kg ^-1土壤、LN 和 HN）被用作 As 固定化的修正。对土壤性质的影响，如 pH、Eh、硫酸盐和硝酸盐；研究了对 As(III) 和异化铁还原的影响以及对微生物群落结构的影响。我们的结果表明，随着硝酸盐的加入，Eh 的还原速度加快。特别是对于 HN，Eh 在 30 天内从 139 mV 下降到 40 mV，高于原始土壤（CK）中的 Eh。硝酸盐、Fe的加入显着抑制了异化铁的还原硝酸盐添加物中的²⁺远低于对照，尤其是 HN，Fe ²⁺浓度比对照低 62.58%。而CK、LN 和 HN 处理的最终 As(III) 浓度分别为 284.67、223.87 和 190.70mg Kg ^-1。在 LN 和 HN 中，NO ₃ ^-的浓度随着培养时间而减弱，这意味着 NO ₃ ^-可以作为电子受体而不是 Fe ³⁺和 As(V)。此外，硝酸盐对微生物具有选择性，而梭菌和地杆菌科的丰度在异化铁的还原中起主要作用的 被强烈抑制，从而抑制了异化铁的还原过程。我们的研究结果表明，硝酸盐通过促进降低 Eh、抑制异化铁还原和砷形态转化，可以作为水稻土壤中砷固定化的有效改良剂。