超滤分级研究腐殖酸的结构组成

利用切面流超滤技术将Pahokee泥炭腐殖酸分为相对分子质量不同的8个级分,并综合应用元素分析和傅立叶变换红外光谱(FT-IR)、固体13C核磁共振(13C NMR)和裂解-气相色谱-质谱(Py-GC-MS)技术详细研究了分级前后腐殖酸分子的结构组成特征.研究表明,随相对分子质量的增加,腐殖酸分子中的元素碳、元素氢含量增加;而元素氧和含氧官能团含量减少;并且低相对分子质量级分中含有相对较多的木本植物来源的芳香结构,而高相对分子质量级分中含相对较多微生物和植物来源的聚脂肪结构.本研究结果不仅说明环境中的腐殖酸分子是由许多相对分子质量不同、结构性质各异的腐殖酸分子组成,而且这些腐殖酸分子可能与腐殖酸形成过程中各种来源的物质在不同阶段的腐殖化产物有关,表明了腐殖酸类地质大分子物质的非均一性和复杂性.

Structural compositions of humic acids fractionated by tangential flow filtration

Humic acid extracted from the Pahokee peat was fractionated into e i ght fractions by tangential flow filtration. The chemical and structural propert ies of the humic acids before and after fractionation were characterized by elem ental analyzer, Fourier transform infrared spectrometry (FT-IR), solid state 1 3C-nuclear magnetic resonance spectrometry (13C-NMR) and pyrolysis-gas chr omatography-mass spectrometry (Py-GC-MS). The results show that the conten ts of C and H, and the H/C molar ratio increase with the increasing relative mol ecular mass, but the content of O and the O/C molar ratio decrease. Moreover, th ere are more wood plants-derived aromatic structural units in the lower relati ve molecular mass fractions, while more plants and microbes-derived aliphatic units exist in the higher relative molecular mass fractions. The results of this work indicate that the humic macromolecule is composed of many humic molecules with different relative molecular mass and chemical compositions. These humic mo lecules are probably the humified products of various compounds in different hum ification processes. This implies the heterogeneous and complex compositions of the humic acid geomacromolecules.