The nature of humic substances (HSs) extracted from soil organic matter and their distinction from degrading plant material has recently been called into question. Quantitative solid-state ¹³C nuclear magnetic resonance (NMR) analyses, in good agreement with elemental analysis, show that HSs are distinct from common biopolymers, refuting claims to the contrary made based on ¹H-detected NMR spectra of the same standard peat humic acid as studied here. Aromatic carbons not bonded to hydrogen or oxygen, which are rare (≤10%) in common biomolecules, constitute a large fraction (28%–33%) of prairie soil and peat humic acids. Oxygen-bonded nonprotonated carbons such as aryl ketones, nonprotonated alkyl C–O, and abundant COOH groups are also characteristic of humic and fulvic acids but not observed in plant biopolymers. These distinctive structural differences between HSs and biopolymers challenge the recent proposal that HSs are unremarkable intermediates in a continuum of degrading biomolecules.

中文翻译：

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丰富的非质子化芳族和氧键合碳使腐殖质与生物聚合物截然不同

从土壤有机质中提取的腐殖质（HSs）的性质及其与降解植物材料的区别最近受到质疑。固态¹³ C核磁共振定量分析与元素分析吻合良好，表明HS与普通生物聚合物不同，驳斥了基于¹的相反说法。此处研究的相同标准泥炭腐殖酸的H检测NMR光谱。不与氢或氧键合的芳族碳在普通生物分子中很少见（≤10％），占草原土壤和泥炭腐殖酸的很大一部分（28％–33％）。氧键结合的非质子化碳，例如芳基酮，非质子化的烷基C-O和丰富的COOH基团也是腐殖酸和富里酸的特征，但在植物生物聚合物中没有观察到。HS和生物聚合物之间的这些独特的结构差异挑战了最近的提议，即HS是连续降解生物分子中不起眼的中间体。