土壤胡敏酸和富里酸的性质表征

Characterization of Humic Acid and Fulvic Acid in Soil

为揭示土壤腐殖质组成和结构特征,以碱溶酸析法从土壤中提取胡敏酸和富里酸,并通过元素分析、分子排阻色谱、红外光谱和^(1)H核磁共振波谱等多种手段分析其元素组成和分子结构信息.元素分析结果表明胡敏酸的w(C)=54.17%,w(O)=39.46%,富里酸的w(C)=33.72%,w(O)=61.37%,两者间有较大差异.胡敏酸的H/C摩尔比高于富里酸,而(N+O)/C摩尔比和O/C摩尔比则低于富里酸,说明胡敏酸的缩合度更低,疏水性更强,氧化程度更低.分子排阻色谱揭示胡敏酸相对富里酸含有更多的大分子组分,平均分子量胡敏酸高于富里酸.红外光谱显示胡敏酸和富里酸含有醇、羧酸、长碳链、芳香烃、酯、醚、酚类等官能团和组分,其中胡敏酸更强的长碳链结构吸收峰信号同样预示其可能含有更多大分子组分,而富里酸的氧可能更多地存在于酚羟基和醇羟基官能团中.^(1)H核磁共振波谱揭示胡敏酸和富里酸含有脂肪烃、芳香烃、酚和烯烃等组分.由此可见,胡敏酸和富里酸在元素组成、分子结构等方面存在明显差异,多手段综合表征对揭示其差异性很有必要.

In order to reveal the composition and structural characteristics of soil humus,humic acid and ful⁃vic acid were extracted from soil by the alkali dissolution and acid extraction method,and their elemental composition and molecular structure information were analyzed by elemental analysis,size exclusion chroma⁃tography,infrared spectrum and ^(1)H nuclear magnetic resonance(^(1)H NMR)spectroscopy.The results of ele⁃mental analysis showed that the mass contents of C and O in humic acid were 54.17%and 39.46%respec⁃tively,and the mass contents of C and O in fulvic acid were 33.72%and 61.37%respectively.There was a great difference between the C and O mass contents of humic acid and fulvic acid.The H/C molar ratio of hu⁃mic acid was higher than that of fulvic acid,while the(N+O)/C molar ratio and O/C molar ratio of humic ac⁃id were lower than those of fulvic acid,indicating that humic acid had lower condensation degree,stronger hy⁃drophobicity and lower oxidation degree.Size exclusion chromatography revealed that humic acid contained more macromolecular components than fulvic acid,and the average molecular weight of humic acid was high⁃er than that of fulvic acid.Infrared spectrum showed that humic acid and fulvic acid contain alcohol,carboxyl⁃ic acid,long carbon chain,aromatic hydrocarbon,ester,ether,phenol and other functional groups and compo⁃nents.The stronger absorption peak signal of long carbon chain structure of humic acid indicated that it might contain more macromolecular components.The O of fulvic acid might be more present in the phenolic and al⁃coholic hydroxyl functional groups.^(1)H NMR spectroscopy revealed that humic acid and fulvic acid contained aliphatic hydrocarbons,aromatic hydrocarbons,phenols,olefins and other components.It can be concluded that there are obvious differences between humic acid and fulvic acid in element composition and molecular structure,and comprehensive characterization by multiple means is necessary to reveal their differences.