矿物基蚯蚓粪表面特征及其对土壤Cd钝化能力的研究

针对农田土壤镉（Cd）活性高的问题，以寻求具有良好重金属钝化特性的原位修复材料为目标，该研究以铁粉、磷矿粉和牛粪混合蚯蚓堆肥所制备的矿物基蚯蚓粪为研究对象，利用系列结构表征手段对其进行基本性质表征，并进一步分析矿物基蚯蚓粪施加下土壤对Cd吸附、有效性和赋存形态的影响，最终筛选出具有良好Cd钝化效果的矿物基蚯蚓粪。结果表明，铁粉及磷矿粉的添加使矿物基蚯蚓粪中的pH值、C/N、有机质含量有所降低，但总养分含量显著增加（P＜0.05）。全自动比表面积及孔隙度、扫描电镜分析和X射线能谱分析结果表明，矿物质的添加增大了蚯蚓粪比表面积和孔容，改变了蚯蚓粪中矿物元素的占比。傅立叶变换红外光谱分析表明，矿物基蚯蚓粪中醇或羧酸类、芳香类以及多糖类物质增多，脂类和碳水化合物减少。X射线衍射分析表明，添加铁粉及磷矿粉制备出来的矿物基蚯蚓粪增加了磷酸盐、纳米零价铁等矿物组分。土壤培养和吸附解吸试验表明，施加矿物基蚯蚓粪显著提升了土壤对Cd的吸附强度，降低了对Cd的解吸率，其中以牛粪+20%铁粉+20%磷矿粉（VCFe+P）进行蚯蚓堆肥所获得的矿物基蚯蚓粪处理的土壤对Cd的吸附效果最佳，较施加纯蚯蚓粪的土壤吸附容量提升137.66%，解吸率降低7.34%～12.76%；该处理的土壤Cd钝化率高达50.02%，Tessier 形态分析结果表明，VCFe+P矿物基蚯蚓粪使交换态Cd向铁锰氧化态Cd和残渣态转化。综上，20%铁粉+20%磷矿粉+牛粪混合蚯蚓堆肥所制备的矿物基蚯蚓粪具有良好的Cd吸附表面特征和高效的Cd钝化能力，在土壤Cd污染修复方面具有较大的应用前景。

Surface characteristics of vermicompost produced with different mineral addition and its effect on Cd immobilization in soil

This study aims to seek in situ remediation materials with a high immobilization efficiency for heavy metals. The mineral-based vermicompost was prepared using cow dung mixed with iron powder and phosphate rock powder minerals. A vermicomposting experiment was also carried out. The mineral-based vermicompost was then examined using a series of structural characterization tools. The remediation effectiveness was assessed to screen the suitable amendments for soil. The adsorption-desorption characteristics were analyzed for the available properties and chemical forms of cadmium (Cd) in soil. The results demonstrated that the addition of iron powder and phosphate rock powder reduced the pH, C/N, and organic matter content in the mineral-based vermicompost, while significantly increasing the total nutrient content. Brunauer-Emmett-Teller (BET) specific surface area measurement, Scanning electron microscopy (SEM) and X-ray energy dispersive analysis (EDS) showed that the mineral-based vermicompost increased the specific surface area and pore volume, whereas, there was a decrease in the pore diameter, compared with the vermicompost (VC). The mineral addition also changed the percentage of mineral elements in the vermicompost. Fourier transform infrared spectroscopy (FTIR) showed that the mineral-based vermicompost had more alcohol or carboxylic acid aromatic compounds and polysaccharides, but fewer carbohydrates and lipids, compared with the vermicompost. X-ray diffraction (XRD) showed that more mineral fractions were found in the mineral-based vermicompost, compared with the untreated. Most mineral components were found in the VCFe+P treatment, such as phosphate and nano-zero-valent iron. Soil culture and adsorption/desorption experiments showed that the application of mineral-based vermicompost enhanced the adsorption efficiency of Cd in the soil, where there was a decrease in the desorption rate of Cd. The best Cd adsorption was achieved in the soil of mineral-based vermicompost with cow manure, 20% iron powder and 20% phosphate rock powder (VCFe+P). The adsorption capacity increased by 137.66%, and the desorption rate decreased by 7.34%-12.76%, compared with the VC application. The VCFe+P treatment was reduced by 50.02% of the available Cd contaminants. Furthermore, The VCFe+P also promoted the transformation of Cd from exchangeable frictions to Fe/Mn oxide fractions and the residual fractions. In summary, the mineral-based vermicompost was produced from a mixture of cow dung. The better adsorption surface and immobilization on soil Cd were achieved in the 20% iron powder and 20% phosphonate powder. There was a great application prospect in the soil remediation of Cd pollution.