Abstract

The term humic substances (HS) refers to a group of heterogeneous, dark-colored polydisperse substances found in soils, peats, natural waters, and sediments. It is hypothesized that HSs are formed as a result of degradation and transformation of biomolecules of organic residues and free radical condensation reactions (a process called humification). Humic substances are classified as a special category of natural compounds that are dissimilar to the biomolecules of plant and microbial tissues, and are resistant to biodegradation. On the basis of their solubility in alkalis, HSs are divided into humic acids (HAs, soluble, precipitated at pH < 2), fulvic acids (FAs, soluble at all pH values), and humin (insoluble residue). The review provides a critical analysis of the HS terminology and nomenclature, the method of extraction of HS from natural objects, and the hypotheses describing their formation. The ambiguity and duality of the concept of HSs (specific compounds and the sum of operational fractions) are demonstrated, as well as an arbitrary character of the division of organic matter (OM) into the dark-colored compounds of poorly defined structure (HSs) and the substances with a known structure (non-HSs). The interpretation of HSs as mass products of a secondary synthesis requires revision. The possibility of extracellular free radical reactions in soils leaves no doubt; however, a quantitative contribution of the corresponding products to the natural OM has not been established yet. The traditional alkaline extraction should be considered as a method for isolation of hydrophilic polar substances, while the precipitation with acid as their concentration for further analysis. The historical names of humic fractions (HAs, FAs, and humin) should be retained as well-established generic terms and names of the preparations obtained in a certain way without attaching unique features and specificity to all components of these fractions. The C_HA/C_FA (or C_HA/C_org) ratios are simple and convenient indicators of the types of humus reflecting bioclimatic conditions of its formation.

中文翻译：

---

腐殖质：假设与现实（综述）

摘要

术语腐殖质 (HS) 是指在土壤、泥炭、天然水和沉积物中发现的一组异质的、深色的多分散物质。据推测，HSs 是由于有机残留物的生物分子的降解和转化以及自由基缩合反应（称为腐殖化的过程）而形成的。腐殖质是一类特殊的天然化合物，与植物和微生物组织的生物分子不同，具有抗生物降解性。根据它们在碱中的溶解度，HS 分为腐殖酸（HA，可溶，在 pH < 2 时沉淀）、富里酸（FA，在所有 pH 值下均可溶）和腐殖酸（不溶性残留物）。该评论对 HS 术语和命名法进行了批判性分析，从自然物体中提取 H2S 的方法，以及描述其形成的假设。证明了 HS（特定化合物和操作分数的总和）概念的模糊性和二元性，以及将有机物质 (OM) 划分为结构不明的深色化合物 (HS) 的任意特征和已知结构的物质（非 HSs）。将 HS 解释为二次合成的大量产品需要修订。土壤中细胞外自由基反应的可能性是毋庸置疑的；然而，尚未确定相应产品对天然 OM 的定量贡献。传统的碱提法应该考虑作为一种分离亲水性极性物质的方法，而沉淀用酸作为其浓度以供进一步分析。腐殖质组分（HAs、FAs 和腐殖质）的历史名称应保留为公认的通用术语和以某种方式获得的制剂的名称，而不应为这些组分的所有成分附加独特的特征和特异性。C_HA /C _FA（或C _HA /C _org）比率是反映腐殖质形成的生物气候条件的腐殖质类型的简单方便的指标。