变性土的腐殖质特性与暗色起源探讨

THE CHARACRERISTICS OF SOIL HUMUS AND THE ORIGIN OF DARKNESS OF VERTISOLS

本文研究鲁豫鄂变性土的腐殖质特征以阐明土壤暗色的起源。主要结果是:土壤腐殖质以胡敏酸为主,HA/FA比在1.02～1.47和1.85～2.27间,E_4及E_4/E_6比值高(4.36～4.71),近似或大于东北的黑土。A组胡敏酸占胡敏酸总量的52％以上,B组占30％,C组占5％～13％。残渣分析表明胡敏素约占有机碳的20％。A组胡敏酸的C/H比为2.17～2.38,B组为2.29～2.10,比一般土壤胡敏酸大一倍,近似或大于风化煤胡敏酸,而C/N比特高(19.82～26.34),推断含角式稠环化合物的芳香核网构成的骨架,C组C/H比低(1.09～1.27),C/N比亦低(9.60～9.78),结构较简单。胡敏酸中芳香核、羧基和羟基的吸收峰明显,A及B组含较多的邻位羧基,而C组不多。A组含氮基团的吸收峰强度小,C组多酰胺衍生物和酚羟基。高芳构化胡敏酸提供的大量共轭双键以及与土粒牢固结合的胡敏素是土壤呈暗色的基础,而与蒙脱石等以不同牢度的结合,形成了对细土部分的浸染效果。供试变性土的暗色物质是母质形成时代的产物。由于这些土壤有机-无机物间的牢固结合以及胡敏酸的高C/H和C/N比,使之在变性土成土过程中保存。

Soil samples for this study were collected from Shandong, Henan and Hubei provinces, China. Results showed that soil humic acid was the predominant composition of the Vertisols. The ratios of HA/FA, E_4/E_6, as well as E_4 were as high as those found in Mollisols in NW China. The relative content of A, B and C group of humic acid fraction was 52%, 30% and 5o%～13% of the total humic acid, respectively. Soil humin content was about 20% of the total organic C. C/H ratio for A and B group were between 2.10～2.38 which were as high as those in humie acid extracted from weathered coal. However, the C/H and C/N ratios for C group were much lower. Data on infrared absorption spectrum denoted that the aromatieeore,-COOH, and -OH absorption pecks were all obvious. All these data indicated that the aromaticity of humic acid in Vertisols was very high. The humus-montmorillonite complexes were considered to be the origin of the darkness of the Vertisols. They were paleo-products formed during paludal stages.