Characteristics of soil organic matter (SOM) are important, especially in the Amazon region, which represents one of the world's most relevant carbon reservoirs. In this work, the concentrations of carbon and differences in its composition (humification indexes) were evaluated and compared for several horizons (0 to 390 cm) of three typical Amazonian podzol profiles. Fluorescence spectroscopy was used to investigate the humic acid (HA) fractions of SOM isolated from the different samples. Simple and labile carbon structures appeared to be accumulated in surface horizons, while more complex humified compounds were leached and accumulated in intermediate and deeper Bh horizons. The results suggested that the humic acids originated from lignin and its derivatives, and that lignin could accumulate in some Bh horizons. The HA present in deeper Bh horizons appeared to originate from different formation pathways, since these horizons showed different compositions. There were significant compositional changes of HA with depth, with four types of organic matter: recalcitrant, humified, and old dating; labile and young dating; humified and young dating; and little humified and old dating. Therefore, the humification process had no direct relation with the age of the organic matter in the Amazonian podzols.

中文翻译：

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亚马逊地区Podzol视野中的土壤有机质：增湿，顽固和定年

土壤有机质（SOM）的特性非常重要，特别是在代表世界上最重要的碳储库之一的亚马逊地区。在这项工作中，评估了碳的浓度及其组成（增湿指数）的差异，并比较了三种典型的亚马逊豆状剖面的几个水平线（0至390厘米）。荧光光谱法用于研究从不同样品中分离出的SOM的腐殖酸（HA）馏分。简单和不稳定的碳结构似乎在地表层中积累，而更复杂的腐殖化化合物则在中和较深的Bh层中浸出并积累。结果表明，腐殖酸起源于木质素及其衍生物，木质素可在某些Bh层中积累。存在于较深Bh层中的HA似乎起源于不同的形成途径，因为这些层显示出不同的成分。随着深度的增加，HA的成分发生了显着变化，其中有四种类型的有机物：顽固的，腐殖质的和陈年的；有机质的。不稳定而年轻的约会；谦卑而年轻的约会; 和一点谦卑和古老的约会。因此，腐殖化过程与亚马逊河地区动物体内有机物的年龄没有直接关系。