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农业土壤中的有机质主要来源于植物残体的部分分解、微生物生物量以及腐殖物质。13C核磁共振、羟化四甲铵气相色谱/质谱法和热解气相色谱/质谱法等先进的分析技术被用来研究地中海的深褐色土壤中土壤有机质及相应的腐殖酸的化学结构。羟化四甲铵法对大多数土壤和腐植酸样品的热化学分析的主要产物是木质素提取复合物和非木质素芳香化合物、杂环氮、脂肪酸甲酯和二羧酸二酯。在>250μm的羟化四甲铵色谱分馏所得的木质素提取复合物要明显多于<2μm时的。脂肪酸甲酯和二羧酸二酯团长链峰值的相对强度在团聚体大小上有所降低,但是他们却对土壤有机物质的结构表现出明显的贡献。热解气相色谱/质谱法和羟化四甲铵气相色谱/质谱法数据表明在腐植酸的结构中含有大量的木质素和表皮材料。在氧化过程的最后阶段随着颗粒大小的降低腐植酸样品中含有木质素提取物单元,而来源于微生物的活动多种脂肪酸以及高含量的非木质素芳香结构。我们的数据表明:新鲜的有机物质被分解和腐化成腐植酸时存在一个类似于结构的稳定阶段,但这部分产物进一步分解(主要是通过氧芳香碳取代氧烷基)转化为腐化产物。
Organic matter in agricultural soils mainly comes from partial decomposition of plant residues, microbial biomass and humus. Advanced analytical techniques such as 13C NMR, tetramethyl ammonium hydroxide gas chromatography / mass spectrometry and pyrolysis gas chromatography / mass spectrometry were used to study the chemical structure of soil organic matter and corresponding humic acid in the dark brown soil of the Mediterranean. The major products of the thermochemical analysis of most soil and humic acid samples by the tetramethylammonium methylation method are lignin extraction complexes and non-lignin aromatic compounds, heterocyclic nitrogens, fatty acid methyl esters and dicarboxylic acid diesters. Lignin extraction complexes obtained by fractionation of hydroxymethyl tetramethylammonium> 250 μm were significantly more than <2 μm. The relative intensities of the long chain peaks of fatty acid methyl esters and dicarboxylic acid diesters decrease in the size of the aggregates, but they do contribute significantly to the structure of soil organic matter. Pyrolysis gas chromatography / mass spectrometry and tetramethyl hydroxymethane gas chromatography / mass spectrometry data show that the humic acid structure contains a large number of lignin and epidermal materials. The humic acid sample contains lignin extract units with a variety of fatty acids derived from microorganisms and a high content of non-lignin aromatic structures as the particle size decreases in the final stages of the oxidation process. Our data show that there is a stabilization stage similar to structure when fresh organic matter is decomposed and humified into humic acid, but this part of the product is further decomposed (mainly by the replacement of oxyalkyl groups by oxygen aromatic carbons) into a decomposed product.