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

为了阐明环境中腐殖质的固定机理，在建立腐植酸平均化学结构模型的基础上，研究了腐殖酸的结构单元，特别是稠合芳香族组分和官能团的组成与腐殖化度的关系，进而研究了腐植酸的~(14)C年龄。X-射线衍射谱的11个谱带分析成功地找到了0.24-1.68 nm的C层平面，对应于4-3环的稠合芳香族结构。它们的平均尺寸和含量随着腐殖化程度和HA分子中芳香C相对丰度的增加而增加。傅立叶变换离子回旋质谱仪(FT-ICR/MS)检测到11-69种芳香酸中的11-69种化合物，其中最多含有24种联苯型化合物。腐殖化程度较高的HAS中，这些成分的数量和峰值强度也较大。根据与~1t；14&gt；C年龄的关系，得出结论：≧5环相对富含稠合芳香族结构有助于提高土壤中HAS的抵抗能力。通过引入相调整的旋转边带技术，改进了固体核磁共振谱对C官能团的定量研究。

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.