泥炭土连续碱抽提腐殖酸的分子结构特征

从Pahokee泥炭土中连续碱抽提分离出8个不同的腐殖酸级分，并对每一级分进行了元素分析、傅里叶变换红外光谱（FTIR）、固态^13C核磁共振（^13CNMR)、高效排阻色谱（HPSEC）等一系列定性、定量研究。结果表明：所分离出的8个腐殖酸级分存在明显的结构性质差异，随提取和蔼的增加，O／C原子比由0．52减少到0．36，H／C原子比由1．05增加到1．52，相应于结构中含氧基团的减少和脂族基的增加，表观分子量也由7．7K增加到22．1K。同时，^13C NMR显示长链脂肪碳结构由无定型向晶型转变。此工作表明在所研究的腐殖酸中可能存在分别具有芳香或脂肪特性的两类腐殖酸结构，每种类型都有不同的分子量分布、元素组成、基团结构和母质来源。在特定的环境因素下，不同类型的腐殖酸会共存于同一体系中，增加了腐殖物质的非均匀性和复杂性。

Molecular Structure Characterization of Humic Acids Progressively Extracted from a Peat Soil

Eight humic acid fractions were progressively extracted from a Pahokee peat soil and were characterized by terms of qualitative and quantitative techniques including elemental analysis fourier transform infrared spectrometry (TFIR), soild state 13C nuclear magnetic resonance ( 13C NMR), high performance size exclusion chromatography (HPSEC). This study demonstrated distinct compositional and structural differences existed in the eight humic acid fractions. The O/C atomic ratio decreased from 0.52 to 0.36 whereas the H/C atomic ratio increased from 1.05 to 1.52 as a function of extraction. This trend corresponded to the decreasing contents of oxygen-containing groups and the increasing contents of aliphatic groups. The apparent molecular weight increased from 7.7 K to 22.1 K. Moreover, the structure of the aliphatic chain varied from amorphism to regularity indicated by 13C NMR. The study suggested that there might be two types of humic acid structure associated in the peat, exhibition, element composition, group structure and source material. Under special environments, humic acids with different types can coexist in a system, which increases the heterogeneity of humic substances.