腐殖酸凝聚影响干旱区盐土复合体形成与稳定的机制

Bad soil structure and low nutrient of solonchak is the main reason for restricting agricultural production. Organo-mineral complexes, which have important effects on soil structure formation and fertility change, are the core of the soil, and humic acid plays an important role in its formation. So far, the effect of humic acid agglomerates on the formation and stability of Organo-mineral complexes is unclear. Different types of solonchak in southern Xinjiang were selected for this project. Taking the difference of typical solonchak environmental factors and salt ion composition as the clue, the humic acid structure change was taken as the core, Based on the theory of flocculation dynamics (Smoluchow ski equation), colloidal stability theory (DLVO) and fractal geometry (Fractal Geometry) in soil research, the dynamic process and its structural characteristics of humic acid agglomeration were studied by dynamic light scattering, static light scattering, high performance liquid chromatography (HPLC) -TOC combined and high resolution transmission electron microscopy (HRTEM). The effects of humic acid agglomerates structure on the formation of Organo-mineral complexes were studied, and the surface properties, microstructures and microstructures of the surface, charge and functional groups interacting with the clay minerals were elucidated. The research results can enrich the formation mechanism of solonchak structure, and provide the theoretical basis for the improvement of solonchak in arid area, improving soil quality and developing sustainable agriculture.

土壤结构性差、养分低是盐土制约农业生产的主要原因。对土壤结构形成和肥力变化有重要影响的土壤有机无机复合体是土壤的核心，腐殖酸在其形成过程中起主导作用。目前，腐殖酸凝聚体结构变化对土壤复合体形成与稳定的影响尚不清楚。本项目选择新疆南部不同类型盐土为研究对象，以典型盐土环境要素与盐基离子组成差异为线索，以腐殖酸结构变化为核心，以絮凝动力学理论、胶体稳定性理论和分形几何等在土壤研究中的应用为基础，利用动态/静态光散射、高效液相色谱（HPLC）-TOC联用及高分辨透射电镜（HRTEM）等分析技术，研究多盐基离子对腐殖酸凝聚的动力学过程及其结构特征，探讨腐殖酸聚合体结构变化对复合体形成的影响，阐明腐殖酸聚合体与粘土矿物相互作用的比表面、电荷、官能团等表面性质及微观形貌的变化。研究成果可丰富盐土结构体形成机理的研究，为干旱区盐土改良、提高土壤质量，发展可持续农业提供理论依据。

土壤有机无机复合体是形成土壤结构和肥力的物质基础，其类型与成土条件的变化密切相关，可为土壤结构形成和土壤发生学的研究提供理论依据。本项目通过实地调查，选取了草甸盐土、沼泽盐土、洪积盐土、残余盐土、次生盐土、棕漠林盐土6种盐土，在测定分析了不同类型盐土理化性质的基础上，采用X射线衍射（XRD）测定分析了盐土粘土矿物类型，结构表明干旱区盐土成土过程以物理风化为主，盐土成熟度较低。采用干筛法、湿筛法和LB法测定分析了土壤团聚体组成特征和稳定性机制，依据土壤团聚体在组成上具有分形特征，利用分形维数的变化指示成土条件的变化。采用粒度与密度组合分组法（CSDF）将游离的轻组有机物与有机无机复合体和游离的矿物分开，采用SEM对fLF、oLF和hF进行形貌结构表征，可以直观的看到不同类型复合体中有机胶体（有机质）与无机胶体（粘土矿物）的存在形态。通过结合态腐殖质分组法从hF中提取了盐土中不同类型与无机胶体起复合作用的腐殖质，采用傅里叶红外光谱仪（FTIR）对其功能团表征分析复合体中有机胶体官能团特性。胶散分组法（A.Φ.丘林法）结果表明，不同类型盐土均游离态有机无机复合体为主，依次为钙键结合态复合体和铁铝氧化物结合态复合体。通过不同类型复合体元素组成，可以了解不同类型盐土的肥力特征，为更好的改良盐土奠定基础。采用HPLC - TOC联合技术分析了复合体中有机碳含量和腐殖酸凝聚前后相对分子质量分布的变化。综上所述，本项目较系统的研究了盐土复合体组成特征，为研究土壤结构形成机理和盐土发生学奠定了坚实的工作基础，同时也为改良盐土提供理论依据。