The effect of wildfires on the soils of the south taiga and forest‐steppe environments of Central Russia (Histic Spodosols and Eutric Fluvic Arenosols) was investigated in terms of the content and quality of humic acids (HAs) using instrumental spectroscopic methods (solid‐state carbon‐13 nuclear magnetic resonance and electron spin resonance). The bulk elemental composition of HAs was not essentially altered in postfire soils; however, the organic matter of fire‐affected superficial soil layers was characterized by changes in the structural composition and biochemical activity levels. Solid‐state carbon‐13 nuclear magnetic resonance spectroscopy showed that there is an intensive increase in aromatic compounds in HA molecules in soil from both the south taiga and forest‐steppe environments. There is a pronounced and statistically significant decline of aliphatic chain content in response to exposure to fire. The free radicals content and the degree of molecular stabilization assessed with electron spin resonance showed an essential alteration of the HAs, expressed in the increase in the radical's portion, in postfire soils compared with that found in soils not exposed to fire. It was also shown that the accumulation of aromatic compounds indicates only apparent stabilization of HAs due to the loss of periphery alkylic carbon species, which was confirmed by destabilization of the molecules as illustrated by the increase of free radicals.

中文翻译：

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评估火灾后土壤的降解动力学：使用光谱学方法研究腐殖酸的稳定性和分子组成

使用仪器光谱法（固态）研究了野火对俄罗斯中部南部针叶林土壤和俄罗斯中部森林草原环境（Histo Spodosols和Eutric Fluvic Arenosols）的影响。碳13核磁共振和电子自旋共振）。在火灾后的土壤中，HA的主要元素组成基本没有改变；然而，受火影响的浅层土壤有机质的特征是结构组成和生化活性水平的变化。固态碳13核磁共振波谱表明，来自南针叶林和森林草原环境的土壤中HA分子中的芳香族化合物大量增加。暴露于火中，脂族链含量显着且统计学上显着下降。与未暴露于火的土壤相比，在火后土壤中自由基含量和通过电子自旋共振评估的分子稳定程度表明，HAs发生了本质变化，以自由基部分的增加表示。还显示出芳族化合物的积累表明由于外围烷基碳物质的损失，HA仅具有明显的稳定作用，这可以通过自由基的增加使分子失稳来证实。与未暴露于火的土壤相比，在火后土壤中自由基含量和通过电子自旋共振评估的分子稳定程度表明，HAs发生了本质变化，以自由基部分的增加表示。还显示出芳族化合物的积累表明由于外围烷基碳物质的损失，HA仅具有明显的稳定作用，这可以通过自由基的增加使分子失稳来证实。与未暴露于火的土壤相比，在火后土壤中自由基含量和通过电子自旋共振评估的分子稳定程度表明，HAs发生了本质变化，以自由基部分的增加表示。还显示出芳族化合物的积累表明由于外围烷基碳物质的损失，HA仅具有明显的稳定作用，这可以通过自由基的增加使分子失稳来证实。