Luis de Almeida Prado Bacellar

Influence of the natural oxidation of the leachate organic fraction from a landfill on groundwater quality, Belo Horizonte: Minas Gerais, south-eastern Brazil

The objective of this work was to evaluate the influence of the natural degradation of the leachate organic fraction from the Belo Horizonte landfill on groundwater chemical evolution. The work focused on the modifications introduced by redox reactions in the presence of terminal electron acceptors. Twenty-one sampling points distributed along 13 monitoring wells were selected for the analysis of the chemical indicators of interest (TDS, SO4−2, Fe+2, Ba, pH and Eh). The behaviour of the variables involved in the alteration of the water quality was assessed by the spatial distribution of target parameters, elaboration of redox diagrams and chemical modelling that focused on the determination of mineral saturation indexes. The study showed a trend toward pyrite precipitation, which leads to the removal of chemical species such as divalent iron and sulphur as sulphide from the system. This removal disturbs the chemical equilibrium, typically by moving the reactions to replenish the sulphate concentration present in the groundwater. This process occurs primarily through the dissolution of compounds that have sulphate in their chemical composition, such as barite, suggesting that part of the barium concentration in the subsurface can be of geogenic origin. This study demonstrated the importance of knowing the nature of the geochemical processes in groundwater contaminated by urban solid waste.

Influência geológica em assinaturas químicas das águas e solos do Parque Estadual do Itacolomi, Minas Gerais

This paper presents an analysis of the geochemistry of superficial waters in the Itacolomi State Park and their relationship to the geological scenario and soil geochemistry. Thirty six soil samples were collected at points located in representative areas from the different lithologies. In each region, the soil samples were collected at diverse depths. In addition, eighteen water sampling points were also selected in areas with different drainage patterns. In the ground and water samples, the concentrations of major and trace elements were determined by ICP-OES. Also, physical-chemical parameters were determined for the water samples. The results reveal that geology plays an essential role in the chemical signature of the soils and superficial waters. Comparison with standard values defined by the rules CETESB 195/05 and CONAMA 357/05 proved the influence of pedological and geological characteristics on the water quality. Anomalous concentrations of several elements were found in the water and ground samples. In addition, it was also possible to observe that the regulations for water quality of this area are inadequate since they do not take the geological factors into consideration.

Study of flow in vadose zone from electrical resistivity surveys

Among the indirect methods applied to environmental monitoring, electrical resistivity has played an important role in accessing water flow in the non-saturated zone of the soil and, consequently, aquifer recharge. This work evaluates the influence of some pedo-geomorphologic properties in the infiltration and percolation of water through the superficial soil horizons by means of multitemporal electrical resistivity sections. The experiments were carried out in two areas of distinct pedo-geomorphological characteristics developed on the crystalline basement of southeastern Brazil. The first is situated in a hollow -shaped slope where lixisols predominate; the second, in a nose -shaped slope where well-developed soils (ferralsols ) predominate. The results proved the efficiency of the electrical resistivity method to delimit percolation of tropical soils, even when subtle differences are found in the hydraulic properties of the soil. It was also possible to establish that in the nose slope percolation is faster than in the hollow.

Estimativa de parâmetros de aquíferos através do coeficiente de recessão em áreas de embasamento cristalino de Minas Gerais

O coeficiente de recessao (α) indica a taxa de producao do fluxo de base, que representa a porcao da vazao de um rio mantida pela restituicao de aguas subterrâneas. Ele pode ser obtido atraves da analise de hidrogramas. Esse coeficiente possibilita o calculo de parâmetros importantes, como a transmissividade de aquiferos, as reservas renovaveis de agua subterrânea e as vazoes minimas em canais de drenagem, que, usualmente, sao obtidas atraves de outros indices hidrologicos, como o Q7,10, muito empregado na gestao de recursos hidricos superficiais. As bacias estudadas estao localizadas na porcao centro-sul de Minas Gerais, em regioes de rochas granito-gnassicas, sob vegetacao, clima e uso e ocupacao semelhantes. Os resultados obtidos, no estudo, foram satisfatorios, indicando os metodos de determinacao de coeficiente de recessao como promissores para se caracterizar a producao de agua subterrânea em bacias hidrograficas do embasamento cristalino. A restituicao de aguas subterrâneas para os sistemas de drenagem e maior nas areas de relevo mais suave, indicando que estas constituem as melhores areas de recarga.

Vertedores portáteis em microbacias de drenagem

The increasing need for the characterization of hydrological conditions of catchments demands better and more practical research techniques. The streamflow characterization is fundamental for hydrological/ hydrogeological studies and it can be determined by several methods. This paper intends to analyze the portable weir technique, an alternative methodology for low flow determination, still relatively unknown in Brazil. Two to three streamflow measurements a day were manually taken in ten catchments of the Maracuja basin, a tributary of the Alto Rio das Velhas river in the State of Minas Gerais. Three kinds of weir were used: triangular, rectangular and trapezoidal Cipoletti, all of them constructed with 4-6 mm thick galvanized iron plate. The results showed that this is a practical, reliable and economic technique of measuring low flows. Even though the peak flows were occasionally not recorded, either because of the weir overflow or because of the long recording period. The recession period was always well recorded, allowing the determination of the baseflow, the recession coefficient and other hydrological indices, which are useful in the indirect method of hydrogeological characterization.

Geophysical analysis of natural caves in iron lithotypes in the region of Mariana, Southeastern Quadrilátero Ferrífero, Brazil

In Brazil, natural caves in iron lithotypes have increasingly been discovered in iron mining areas and its surroundings. Mining companies attempt to study them according to the Federal Decree 6640/2008 and the Normative Instruction 2/2009 of the Ministry of the Environment, which is concerned with the preservation of the Brazilian Speleological Heritage. This research is within one of those studies in which a geophysical campaign methodology is established for an attempted prospection of caves, in an area located on the north flank of Marianas Anticlinal, Quadrilátero Ferrífero. The flank, which is sustained by iron formations from the Itabira Group and covered by the product of alteration and sedimentary redistribution, experienced extensive and compressive tectonics, generating, respectively, the main structuration in the NW-SE direction and schist thrust slices from the Nova Lima Group. Caves are mainly developed in the lithological contacts and in fault zones. In the regional stage, the methodology uses aeromagnetometric (identification of iron lithotypes, structural and statistical analysis of magnetic lineaments) and aeroradiometric (structural-geological mapping and setting of lithological contacts) methods. Results have shown some caves in lateral contact zones between lithologies, and the structural control imposed by a shear zone in the area. At the local stage, the electrical resistivity method EL was used, dipoledipole array, data mathematical inversion, presentation of pseudo-depth sections and tridimensional modeling. The results, in accordance with the topographic data, show the possible limits of the geometric contour and the tendency for cave deepening. However, studies of the moisture, of similar caves with different spacings, and the use of Ground Penetration Radar – GPR are suggested.

Distribution of groundwater hydrochemical parameters in the surrounds of Lagoa da Confusão - TO - Brazil

As aguas subterrâneas tem grande importância para o abastecimento, economia e conservacao ambiental, contudo, fatores naturais e antropicos podem alterar sua disponibilidade e qualidade, tornando-as vulneraveis a contaminacao. Neste sentido, esse trabalhou buscou entender a distribuicao de parâmetros hidroquimicos na regiao da Lagoa da Confusao, no estado do Tocantins, por meio de analises fisico-quimicas de amostras de agua subterrânea. As analises fisico-quimicas das amostras coletadas em pocos mostraram que as aguas da regiao tem sua hidroquimica controlada prioritariamente pelo bicabornato, calcio e magnesio. As amostras apresentaram, em sua maioria, concentracoes em conformidade com o padrao brasileiro de potabilidade (Portaria do Ministerio da Saude no 2.914 de 12 de dezembro de 2011). A distribuicao dos parâmetros demonstra que a hidroquimica na area esta relacionada a geologia da regiao, marcada pela ocorrencia de carste, bem como a dinâmica de fluxo subterrâneo. Abstract Groundwater has great importance for the supply, economy and environmental conservation, however natural and man-made factors can alter their availability and quality, making them vulnerable to contamination. In this sense, this work sought to understand the hydrochemycal parameters distribution in the region of Lagoa da Confusao, in the State of Tocantins through physical and chemical analyzes of groundwater samples. The results obtained from the analysis of these samples demonstrated that the water of the region has its hydrochemical primarily controlled by bicarbonate, calcium and magnesium. Most samples had parameter concentrations in accordance with the Brazilian standard for drinking water (Ordinance of the Ministry of Health Act. 2.914 of December 12, 2011). The distribution of the parameters shows that the hydrochemistry in the area is related to the geology of the region, marked by the occurrence of karst as well as to the subterranean flow dynamics.

Geofísica aplicada ao estudo de fluxos da água no solo

The electrical resistivity is common used in studies that intents to understand as occur the fl ow of water in soil and consequently as occur the groundwater recharge. The main goal of this paper is to evaluate the interference of some physical properties of the ground in the determination of the front of saturation predicted with the use of the electrical resistivity and to compare as if of the a percolating in the vadose zone, observing the variation of gotten profi les of resistivity in an interval of defi nitive time. Experiments were conducted in soils of southeastern complex crystalline rocks of reliance (Bacao complex), within the Quadrilatero Ferrifero, Centro-Southern State of Minas Gerais, Brazil. For this experiment it was chosen two different areas by geomorphologic features. The fi rst one is hollow on the slippery slope, with the predominance of lixisols; the second one is nose on the slippery slope, with well-developed topsoil prevalence (ferralsols). The results showed that the electrical resistivity method proved effi cient

AVALIAÇÃO DA SUSCEPTIBILIDADE DE SOLOS GNAISSICOS À EROSÃO SUBSUPERFICIAL

The basement rock areas of the Maracuja hydrographic basin show great incidence of huge gullies. This work aims to investigate the influence of the underground erosive processes in the evolution of these features and to understand how the mineralogical and textural factors could affect soil erodibility, specially of the saprolites, since the lateric soils of this basin are more resistant to erosion. So, basic characterization and erodibility essays were carried out in representative soil samples. Soil susceptibility to piping and seepage erosion were investigated through current and modified pin-hole-essays. Laboratory physical models were used in order to observe these and other possible underground erosion mechanisms, especially the slides. However, piping erosion only occurs in the unsaturated portion of gully slopes, provoked by the concentration of superficial water, since pipes are not stable under total saturation, when their roofs tend to collapse, because of the low cohesion of these saprolites. In the other hand, slumps are very common in the saturated portion of gullies, affecting saprolites even in small and low declivity slopes.