Gênese, mineralogia, micromorfologia e formas de fósforo em arqueo-antropossolos da várzea do Rio Amazonas

• Autor(a) principal: Souza, Kleberson Worslley de
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1615
• topic: Terra Preta de Índio; Solo antrópico; Solos arqueológicos; Indian Black Earth; Anthropic soil; Archaeological soils; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Throughout the Amazon region is common the occurrence in sites of Indian Black Earth (IBE) often accompany the main rivers. The IBE soils are considered anthropic, because they have human activity as a cause of occurrence, although some scientists point out other hypotheses for the formation of the Amazon IBE, already discredited in the news. In this work, were studied sites of IBE between Careiro da Várzea and Coarí cities. The soils were subjected to chemical and physical analysis routine, sequential fractionation of P forms and determination of total contents elements in the sample digestion with HCl, HF and HN in the microwave. Were developed X-ray diffraction patterns for clay minerals identification in selected samples in natural clay, clay with K saturation at 25, 350 and 550 °C, clay saturated with Mg and Mg more glycerol at room temperature and Clay treated for concentration of oxides. The microchemical and micromorphological study was performed in thin sections prepared from undisturbed samples. According to results, the preterit human actions in studied sites promoted significant changes in many of the physical, morphological, chemical and mineralogical soil characteristics of the floodplain environment, making them very different from adjacent soils. Although the soil of the lowland landscape is naturally more fertile, it is possible to observe that human interference has caused significant changes in soil fertility in this environment. The present results show that the floodplain sites studied IBE have the highest P concentrations ever recorded in the literature. The Lauro Sodré site included in this study, showed 7905 mg dm-3 of P extracted by Mehlich-1. Most of the P in these soils is as its form originally deposited in the soil (P-Ca). Zn, Cu, Sr and Ba were directly correlated with the anthropic horizons. Other changes in the soil which were due to human intervention are a matter of mineralogy, the presence of apatite and vivianite, not found in the adjacent soil. The preservation of biogenic apatite in the form of bone fragments in the anthropogenic horizons of these soils is probably due to the higher pH and the constant contribution of P and Ca geogenic to the soil by continuous deposition of Andean sediments relatively rich in these elements. This is evidenced by microchemical maps that generally show bone fragments without surrounding reactions of dissolution of biogenic apatite. Nevertheless, in the anthropic horizons of these soils was found magnetic attraction material. The XRD detected the presence of magnetite and maghemite in this material. The training most likely magnetic minerals (magnetite / maghemite) horizons anthropogenic of Fluvisols was the frequent occurrence of fire in the area of formation of the IBE, promoting the formation of magnetite from the substrate with sufficient supply of Fe3+, released from ferromagnesian minerals of Andean origin, in a chemically reducing environment and high temperatures, which would then be oxidized to maghemite, according to the dynamics of the environment. This suggests that the use of fire was widespread in the floodplain as in the upland.