超顺磁性纳米材料对镉污染稻田土壤微生物和酶的影响

以磁性纳米Fe₃O₄和羟基磷灰石等为原料，制备出超顺磁性纳米Fe₃O₄-磷酸盐功能化材料（MFH），通过在镉污染稻田土壤中投加MFH，对土壤进行磁选修复.选择对Cd具有高、低富集两种水稻，在修复后土壤中进行盆栽试验，研究MFH磁选修复对土壤微生物和酶的影响，探究该材料应用于农田镉污染修复的可能性.结果表明，施用MFH修复镉污染土壤，对Cd污染土壤有较好的修复效果，土壤中总Cd和有效态Cd浓度有了明显降低，总镉去除率为38.9%，有效镉下降率为27.3%，并且两种水稻籽粒中Cd含量均显著降低.采用MFH磁选修复土壤镉后，在两种水稻拔节期、抽穗期和成熟期土壤微生物群落多样性、群落丰富度均有所降低；栽培Cd高富集的玉针香水稻品种的处理在拔节期和抽穗期稻田土壤优势细菌Firmicutes丰度显著增加.采用MFH磁选修复土壤镉后，在两种水稻拔节期、抽穗期和成熟期土壤脲酶活性、过氧化氢酶活性以及土壤过氧化物酶活性均得到了提高；栽种Cd高富集品种玉针香的土壤POD酶活性比栽种低富集品种湘晚籼13号的土壤POD酶活性要略高，而脲酶活性则相反.

Effects of Superparamagnetic Nanomaterials on Soil Microorganisms and Enzymes in Cadmium-Contaminated Paddy Fields

Using Fe₃O₄ and hydroxyapatite as raw materials, superparamagnetic nanometer-sized Fe₃O₄-phosphate functionalized materials (MFH) were prepared. Soil was subsequently magnetically repaired by adding MFH to cadmium-contaminated paddy field soil. Two kinds of rice with high (Yuzhenxiang) and low (Xiangwanxian-13) cadmium enrichment were selected for conduct pot experiments to study the effect of MFH magnetic separation on soil microorganisms and enzymes, and explore the possibility of application in the remediation of cadmium-polluted farmland. The results showed that MFH application improved the soil remediation effect, with significantly reduced total Cd (38.9%) and available Cd (27.3%) contents. In addition, the Cd content of the two kinds of rice grain was significantly reduced. After MFH magnetic separation, soil microbial community diversity and richness were decreased during the jointing, heading, and maturing stages of the two rice varieties. Treatment of cultivated Yuzhenxiang rice with high concentrations of Cd significantly increased the abundance of dominant Firmicute bacteria in the rice field during the jointing and heading stages. With the use of MFH in the magnetic separation, urease, catalase, and soil peroxidase activity were improved during the jointing, heading, and maturing stages of the two rice soils. The POD enzyme activity in the soil planted with Yuzhenxiang was slightly higher than that planted with Xiangwanxian-13, while urease activity showed the opposite trend.