Genesis of Amazonian Spodosols : a study on the structure and mobility of organic matter ; Genèse des Spodosols Amazoniens : une étude sur la structure et la mobilité de la matière organique ; Gêneses de espodossolos amazônico : um estudo sobre a estrutura e a mobilidade da matéria orgânica

Soils play an important role in the most of the activities that occur on the planet. It participation in the main biogeochemical cyles can be highlighted. Soil organic matter (SOM) plays a key role in environmental sustainability, since it is related tocabon and nutrient cycling, being essential for studies related to global climate change and agronomy. One of the major SOM fluorophore is the humic substances (HS), which is fractionated according to their solubility in humic acids (HA), fulvic acids (FA) and humin (HU). The study of the optical properties of the organic matter is an important tool for structural and molecular understanding of humic fractions. Based on that, this work aimed the study of the Amazonian Spodosols genesis through the evaluation of organic matter structural characteristics and its properties of metal complexation using different spoectroscopic techniques. The main results of this research showed large carbon accumulations in depth. Futhermore, is was possible to infer how the Amazonian Spodosols organic matter is divided : - more recalcitrant, humified and old ; -labile and young ; -recalcitrant, little humified and old ; -humified and young. The study demonstrated clearly tha the humification process has no direct relationship with the organic material dating, and that factors such as texture, presence of water and micro-organisms have influenced the formation and humification of that organic material. The FA fraction of the soil has a contribution from groundwater and its chemical structure varies little in depth. Additionaly, FA showed selective interaction with soil metals. However, the HA fraction has been shown less selective, associate with various meta types , such as K, Fe, Mg, Zn and Al. Moreover, its chemical structure varies greatly in the soil depth. Due to the diversity of metals that the HA has affinity, it should be the main responsible of the soil fertility. After all, the results showed that all the three humic fractions are involved in the process of soil ...