Construction of model structure of humic substances toward the elucidation of their stability in the environment

为了在建立腐植酸平均化学结构模型的基础上阐明腐植酸在环境中的固定机理，研究了腐植酸（HAs）的结构单元，特别是缩合芳香组分和官能团的组成与腐植酸的腐殖化程度的关系，然后研究了^<14>C年龄。x射线衍射（XRD）谱图的11波段分析成功地找到了0.24 ~ 1.68 nm的c层平面，对应于4 ~ 3环缩合芳族结构。它们的平均大小和含量随着腐殖质化程度的增加和HA分子中芳香C的相对丰度的增加而增加。傅里叶变换离子回旋质谱（FT-ICR/MS）检测了一系列线性融合和网状凝聚芳香酸的11-69个化合物，其中最多有24个双酚类化合物。腐殖质化程度越高，这些成分的数量和峰强度也越大。根据与^<14>C年龄的关系，得出：≥5环的凝聚芳香结构的相对富集有助于土壤中HAs的抗性增强。引入了相位调整自旋边带技术，改进了固态C <13>核磁共振光谱定量C官能团的方法。

Toward an elucidation of immobilization mechanism of humic substances in th environment based on the establishment of their average chemical structure model, structural units especially condensed aromatic components and composition of functional groups in humic acids (HAs) were investigated with regard to the degree of humification and then ^<14>C age. The 11 band analysis of X-ray diffraction (XRD) profile succed in finding 0.24-1.68 nm C-layer planes corresponding to 4- to 3-ring condensed aromatic structure. Their mean size and contents increased with increasing degree of humification and relative abundance of aromatic C in HA molecules. Fourie transform-ion cyclotron mass spectrometry (FT-ICR/MS) detected 11-69 compounds of a series of linearly fused and net-like condensed aromatic acids with max 24 biphelyl-type compounds. The number and peak intensity of those components were also larger in the HAs with a greater degree of humification. Based on the relation to ^<14>C age, it was concluded that the relative enrichement of condensed aromatic structures with ≧5 rings contributes to the enhancement of recalcitrance of HAs in soil. Quantification of C functional groups using solide-state ^<13>C NMR spectroscopy was improved by introducing phase-adjusted spinning-sideband technique.