Cd is one of the most serious and harmful heavy metals in the world. Nanomaterials as a new passivating agent for heavy metals in soil have become a hot issue. But nanometer magnesium hydroxide application to heavy metal pollution in soils has not been reported. The laboratory culture experiments were conducted to study the effect of nanometer magnesium hydroxide and ordinary magnesium hydroxide (100, 200, and 300 mg kg⁻¹) as cadmium passivators on soil cadmium form under different cadmium levels (1, 5, 10, and 15 mg kg⁻¹). The results showed that the soil Cd distribution ratio of exchangeable Cd (EX-Cd FDC) was 66.7% to 81.8% at cadmium levels of 1, 5, 10, and 15 mg kg⁻¹, identifying it as the main form of soil cadmium. Soil EX-Cd FDC reached the lowest level on the 14th day of culture. Addition of both nanometer magnesium hydroxide and ordinary magnesium hydroxide decreased the EX-Cd FDC of the soil at each cadmium level. With increasing amount, the soil EX-Cd FDC followed a decreasing trend. During the 0–28 days of culture, at the levels of 1, 5, 10, and 15 mg kg⁻¹ cadmium, the EX-Cd FDC of soil treated with nanometer magnesium hydroxide and ordinary magnesium hydroxide decreased by 11.4% to 67.7%, 7.8% to 37.2%, 7.7% to 36.4%, and 5.0% to 28.8% (nanometer magnesium hydroxide) and .5% to 49.5%, .6% to 15.0%, 1.0% to 18.1%, and .7% to 14.6% (common magnesium hydroxide), respectively, compared with control. Under the same application amount, nanometer magnesium hydroxide achieved a better effect than ordinary magnesium hydroxide in reducing soil EX-Cd FDC. The antagonism between Cd and Mg competes for exchange sites during soil adsorption or Mg²⁺ forms hydroxy-magnesium through OH⁻ coordination in the soil via hydrolysis equilibrium. This facilitates the formation of precipitates, such as carbonates in Cd²⁺, and reduces active-state cadmium in soil. The effect of nanometer magnesium hydroxide in passivating active cadmium on cadmium-contaminated soil exceeds that of common magnesium hydroxide.

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不同镉水平下纳米氢氧化镁对土壤镉形态的影响

镉是世界上最严重和最有害的重金属之一。纳米材料作为一种新型的土壤重金属钝化剂已成为研究热点。但纳米氢氧化镁在土壤重金属污染中的应用尚未见报道。通过室内培养试验，研究了不同镉水平（1、5、10、15）下作为镉钝化剂的纳米氢氧化镁和普通氢氧化镁（100、200、300 mg kg ^-1）对土壤镉形态的影响。毫克公斤^-1 )。结果表明，在镉含量分别为1、5、10和15 mg kg ^{-1时，交换性Cd（EX-Cd FDC）的土壤Cd分布率为66.7%~81.8%。}，确定其为土壤镉的主要形态。土壤EX-Cd FDC在培养第14天达到最低水平。添加纳米氢氧化镁和普通氢氧化镁均降低了土壤在各镉水平下的EX-Cd FDC。随着用量的增加，土壤EX-Cd FDC呈下降趋势。在培养的 0-28 天期间，在 1、5、10 和 15 mg kg ^{-1的水平下}镉、纳米氢氧化镁和普通氢氧化镁处理土壤的 EX-Cd FDC 分别下降 11.4% 至 67.7%、7.8% 至 37.2%、7.7% 至 36.4%、5.0% 至 28.8%（纳米氢氧化镁）和与对照相比，分别为 0.5% 至 49.5%、0.6% 至 15.0%、1.0% 至 18.1% 和 0.7% 至 14.6%（普通氢氧化镁）。在相同的施用量下，纳米氢氧化镁在降低土壤EX-Cd FDC方面比普通氢氧化镁取得了更好的效果。Cd和Mg之间的拮抗作用在土壤吸附过程中竞争交换位点，或者Mg ²⁺通过水解平衡在土壤中通过OH ^-配位形成羟基镁。这促进了沉淀物的形成，例如 Cd ^{2+中的碳酸盐}，并减少土壤中的活性态镉。纳米氢氧化镁对镉污染土壤的活性镉钝化效果超过普通氢氧化镁。