A comparative study on the chemical composition of humic acids from forest soil, agricultural soil and lignite deposit - Bound lipid, carbohydrate and amino acid distributions
A comparative study on the chemical composition of humic acids from forest soil, agricultural soil and lignite deposit - Bound lipid, carbohydrate and amino acid distributions
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DOI：
10.1016/j.geoderma.2005.01.010
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发表时间：
2006-01-01
期刊：
影响因子：
6.1
通讯作者：
Allard, B
中科院分区：
文献类型：
--
作者：
Allard, B
对从森林土壤、农业土壤和褐煤矿床中分离的腐植酸的碱解和酸解组分进行了分析，并对不同腐植酸的碱解脂(结合脂)、碳水化合物和铝氨基酸特征进行了比较。两种土壤腐植酸的组成相当相似，鉴定出三种主要的脂类：(I)脂肪族组分，(Ii)芳香族组分，(Iii)甾醇和三萜醇。脂肪减法是最丰富的，主要由角质和松脂衍生的部分组成，其中一些可以明显地与植被有关。短链α-羟基烷酸和β-羟基烷酸的存在表明有少量细菌输入。芳香族亚组分在碱解产物中所占比例较低，主要由木质素衍生的甲氧基酚组成。在微量的存在下，甾醇和三萜醇主要来自较高的植物来源。褐煤腐植酸的碱解产物有明显不同。褐煤HA释放的结合脂几乎全部由脂肪族组分组成，主要以长链烷酸为主。木质素来源的部分很难检测到，仅由香草酸和4-羟基苯甲酸组成，表明褐煤腐植酸中木质素的变化程度要高得多。不含甾醇和三萜醇。尽管酸水解释放的单糖的组成相当一致，但其分布随腐殖化程度的不同而不同。从土壤到褐煤腐植酸，(半乳糖+甘露糖)/(木糖+阿拉伯糖)比值逐渐增大。这些比值的高值表明碳水化合物主要来自微生物，其中腐殖酸、中性和酸性蛋白质氨基酸占主导地位。非蛋白质氨基酸仅为次要成分，主要由羟基脯氨酸和鸟氨酸组成。两种土壤的氨基酸分布基本一致。褐煤腐植酸的氨基酸分布与土壤相似，不同之处在于：(1)腐殖化程度越高，微生物对氨基酸的贡献越大；(2)腐殖化程度越高，微生物对氨基酸的贡献越大，可能是通过氢键与腐植酸表面相互作用，有利于氨基酸的保存。(C)2005 Elsevier B.V.保留所有权利。
Base- and acid-hydrolysable fractions of humic acids (HAs) isolated from a forest soil, an agricultural soil and a lignite deposit were analysed, and comparisons were made between the base hydrolysable lipid (bound lipid), carbohydrate and Al amino acid signatures of the different humic acids.Bound lipids differ depending on the humic acid origin. Their composition were rather similar for the two soil humic acids, with three main lipid classes identified: (i) aliphatic components, (ii) aromatic components and (iii) sterols and triterpenols. The aliphatic subtraction was the most abundant and consisted predominantly of cutin- and suberin-derived moieties some of which could be clearly related to the vegetation. A minor bacterial input was indicated by the presence of short chain alpha- and beta-hydroxyalkanoic acids. Aromatic subfraction contributed to a low amount to the total base hydrolysates and consisted mainly of lignin-derived methoxyphenols. Present in trace amounts, sterols and triterpenols are mainly of higher plant origin. The base hydrolysate from lignite humic acid markedly differs. Bound lipids released from lignite HA comprised almost exclusively aliphatic components, largely dominated by long chain alkanoic acids. Lignin-derived moieties, hardly detected, consisted solely of vanillic and 4-hydroxybenzoic acids indicating a much higher degree of lignin alteration in lignite humic acid. Sterols and triterpenols were absent.Although the composition of monosaccharides released upon acid hydrolysis was rather uniform irrespective of the humic acid origin, the distribution changed with the degree of humification of the HAs. Ratios of (Galactose+Mannose) to (Xylose+Arabinose) increased from soil to lignite humic acids. The high values of the ratios indicate that carbohydrates are primarily of microbial origin.In all humic acids neutral and acidic protein amino acids dominated. Non protein amino acids were only minor components consisting mainly of hydroxy proline and ornithine. The amino acid distributions of both soil HAs were similar. The amino acid distribution of lignite HA resembled that of soil HAs except for the following differences: (1) the absence of hydroxy proline and the greater abundance of ornithine suggesting a higher microbial contribution to the amino acids as the degree of humification increases, (2) the higher contribution of polar amino acids suggesting a preferential preservation of these amino acids possibly by interaction with the humic acid surface through hydrogen bonds. (c) 2005 Elsevier B.V. All rights reserved.