Navegando por Autor "Fontes, Mauricio Paulo Ferreira"
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Item Mineralogy, micromorphology, and genesis of soils with varying drainage along a hillslope on granitic rocks of the atlantic forest biome, Brazil(Revista Brasileira de Ciência do Solo, 2018-07-16) Pacheco, Anderson Almeida; Ker, João Carlos; Schaefer, Carlos Ernesto Gonçalves Reynaud; Fontes, Mauricio Paulo Ferreira; Andrade, Felipe Vaz; Martins, Eder de Souza; Oliveira, Fábio Soares deAlthough the physical environment of the Atlantic Forest realm is well known, studies on the soil-landform relationships are fundamental to improve the management of soil resources to facilitate sustainable development. The purpose of this study was to evaluate a representative topossequence on the “Mares de Morros” landscape of deeply weathered regolith on leucocratic granite rocks and demiorange convex slopes. The soils varied along the topossequence according to drainage and were classified as Acrudox, Pseudogleysol, and Epiaquent. The clay fraction was composed by kaolinite, in association with gibbsite, goethite, hematite, and traces of vermiculite and hydroxy Al interlayered vermiculite (HIV). The kaolinite crystallinity index obtained by different methods showed high structural disorder throughout the sequence, indicating that long-term pre-weathering has produced a homogenous regolith with little differences in terms of mineralogy, despite the changes in drainage. On the other hand, micromorphological features showed a complete change from the typical, well-developed microaggregate structure of upland, well-drained soils, to a massive, poorly developed structure downslope, consistent with the morphological description. Changes in microstructure development and micropedological features occurred both vertically and laterally along the topossequence and indicate that mineralogy alone cannot account for the microaggregate structure of kaolinitic Latossolos (Oxisols) well-drained with low Fe contents. Soils from the “Mares de Morros” landscape of the Alegre river basin on leucocratic granitic rocks highlight an inheritance of a deep preweathered regolith, showing subtle chemical and mineralogical changes, but marked morphological and physical differences along the topossequence, basically controlled by soil drainage in the past or present.Item Mobility of heavy metals as related to soil chemical and mineralogical characteristics of Brazilian soils(Environmental Pollution, 2000-10-26) Matos, Antônio T.; Fontes, Mauricio Paulo Ferreira; Costa, Liovando Marciano Da; Martínez, Mauro AparecidoIn order to better understand the relationship between soil characteristics and mobility of some heavy metals, correlation studies were conducted in samples of unlimed and limed A, B and C horizons of three Brazilian soils, representative of the majority of the tropical soils. A number of chemical and mineralogical characteristics of one Oxisol and two Ultisols were related to the retardation factors (Rf) for zinc (Zn), cadmium (Cd), copper (Cu) and lead (Pb). The retardation factors, obtained in leaching column experiments, were used as an estimate of solute movement in the profile. Soil types and soil horizons were found to influence metal retardation factors which, in turn, correlated better with the chemical than the mineralogical soil characteristics. For the unlimed soil samples, the soil characteristics that significantly correlated with Zn-Rf and Cd-Rf were the sum of exchangeable bases (SB), and soil exchangeable (Ca-KCl) and non-exchangeable (Ca-HCl) calcium contents. These results showed the strong influence of the cation exchange phenomenon on the retention and mobility of these two metals. For Cu and Pb, not only SB, cation exchange capacity (CEC) and Ca-KCl and Ca-HCl but also the organic matter correlated well with the Rf, showing that complex or chelate formation may play an important role in the movement of these elements. The important soil chemical characteristics related to the retardation factors in the limed soil samples were SB for Cd, and Ca-HCl for Cu and Pb, suggesting that precipitation may also influence the mobility and retention of the latter two heavy metals in these soil samples. Soil pH influenced the heavy metals adsorption and movement as shown by the significant correlation with the retardation factors when the combined data for the unlimed and limed soil samples was considered.