土壤胡敏酸的^13C核磁共振研究

胡敏酸(HA)是土壤有机质的重要组分,其结构性质与土壤形成和肥力特性有密切关系,长期以来一直是土壤化学研究的难点和重点之一。NMR是研究HA结构的有效手段。自Bar-ton和Schnitzer(1963)首次用~1H NMR研究土壤有机质以来,国外已先后应用~1H、~(13)C NMR和CP-MAS-~(13)C NMR等对土壤及其它来源的HA进行了许多研究,并取得引人注目的进展。但在国内,这方面研究还刚刚开始。本文应用~(13)C NMR方法对东北几种主要耕作土壤以及泥炭和猪粪的HA进行了结构表征,为土壤腐殖酸化学的基础研究提供了资料。

~(13)C NMR Studies of Humic Acids from Soils

The 13C NMR spectra were measured for humic acids from several cultivated soil (black, brown forest, meadow and paddy soil) in the Northeast of China. A comparison between humic acids from peat and those from pig manure was also made. The results show that humic acids of soils mainly consist of four types of carbon: corbonyl, aromatical, alkoxy and polymethylene. Their aromaticity is less than 40%. There are some differences among various humic acids from different soils. Humic acids from peat and pig manure are characterized by lower molecular weight and lower degree of oxidation compared with soil humic acids. The aromaticity of the humic acid from peat is much higher than that from pig manure. The results also show that the 13C NMR spectrometry can be considered as one. of the most effective methods for investigating the structural characterization of humic substances.