Geothermal investigations in an area of induced seismic activity, northern São Paulo State, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Pollution by hexachlorobenzene and pentachlorophenol in the coastal plain of São Paulo state, Brazil

Organochlorine compounds were dumped by chemical industries during the 1970s in many areas of the coastal plain of São Paulo state in Brazil. These dumps, located on hillsides and in valleys, in both rural and urban environments, are responsible for soil and water pollution. The objective of this work was to determine how the pollutants have spread in an area occupied by a spodosol-type soil mantle. The study combines soil morphological observations with soil and water analysis of hexachlorobenzene (HCB) and pentachlorophenol (PCP) in soil toposequences. The results indicate that the highest pollutant concentrations are observed near the dump site and that the compounds contamination is increasing. A map integrating topography and chemical concentrations was created to visualize the spatial distribution of HCB levels in the landscape. Physical and chemical analyses were performed to measure HCB and PCP levels in the soil. Soil water appears to act as a vector of HCB, probably through complexation with and dispersal of dissolved organic matter. The persistence of HCB at the studied site is most likely due to the low pH values in combination with a high content of organic matter. HCB was consistently found in higher concentrations than PCP. It is plausible that the cause of this difference is that PCP is degraded more easily under sunlight than HCB and that degradation of PCP under acid conditions leads to the formation of HCB. © 2003 Published by Elsevier B.V.

Investigação de Intrusão de Água Salgada em Aqüífero Superficial a Partir de Medidas de Resistividade Elétrica

A site investigation program was carried out to detect salt-water intrusions in a shallow sedimentary aquifer based on electrical resistivity measurements. The site is located close to Paranaguá harbor, in the Paraná State, Brasil. At this site, high chloride concentration contaminated shallow water wells used to supply water for local industries. The site investigation program included a fieldwork, dipole-dipole electrical profiling, resistivity piezocone tests, physical-chemical analysis of sampled water and interpretation of borehole logs. The resistivity piezocone tests provided two simultaneous information; the soil stratigraphy at a very detailed level and a quasi-continuous resistivity profile. Both information adequately complemented dipole-dipole electrical profiling test data. The integration of all test data allowed identifying the contaminated areas as well as guided the location of new water wells to be installed in this area.

Resistivity (DC) method applied to aouifer protection studies

Resistivity (DC) method using vertical electrical soundings (Schlumberger array) are conducted In the vicinity of Canoas/RS, applied to environmental studies with the objective of Investigating groundwater conditions, The present paper shows a geoelectrlcal Identification of the lithology and an estimate of the relationship between the resistivity and Dar Zarrouk parameters (transverse unit resistance and longitudinal unit conductance) with the properties such as aquifer transmlssivlty and protection of ground water resources, In the saturated sediments, resistivity values defined the following sequence: clay layers (resistivity < 40 ohm-m) and sand layers (resistivity > 40 ohm-m), Two sand layers were identified; one corresponding to the unconfined aquifer and another to the confined aquifer between two clay layers, In the map of the transverse unit resistance of the unconfined aquifer, the tendencies of high values can be associated with the zones of high transmissivity; hence, these zones are suggested for the installation of monitoring wells, The map of longitudinal conductance Illustrates the Impermeability of the confining clay layer, Values of S > 1.0 siemens would indicate zones in which the confined aquifer would be protected; In comparison, values of S < 1.0 siemens would indicate zones of probable risks of contamination. © 2006 Sociedade Brasileira de Geofísica.

Resistivity piezocone for geo-environmental site characterization: Two case histories from Brazil

This paper presents two case histories from Brazil where geophysical and resistivity piezocone tests were carried out to detect contamination. At the first one, the site investigation program was carried out to detect salt-water intrusions in a superficial sedimentary aquifer, at the Paranaguá harbor, in Paraná State. The second case history is a sanitary landfill from Bauru City, São Paulo State. In both sites, superficial geophysical tests were interpreted to detect and delineate the shape of contamination plume, helping to locate the resistivity piezocone tests. It was found that the interpretation of resistivity piezocone tests is straightforward to assess salt-water intrusion in sedimentary sands. For tropical soils, this technique presented some limitations since the groundwater table sometimes is deeper than the layer penetratable to the cone. Moreover, the genesis of those soils affects soil behavior and soil and water sampling is required to support interpretation.

Avaliação do processo de fluoretação nos sistemas de abastecimento de água da região de Araçatuba, São Paulo

This paper focuses on the drinking-water fluoridation process in Araçatuba region water supply systems by means of 5.157 fluoride concentration data from 2001 to 2005. These data were studied based on the water source, the administration and the structure of the water supply system, according to the population of the county and the type of management. Almost half of samples did not comply the fluoridation standard and the higher compliance was verified in the water supply systems operated by Sabesp (69%), followed by the group of Large counties (52%), statistically similar to the Medium ones (51.4%), and better than the Small ones (28%). The systems with surface intakes showed statistically higher performance in the compliance to the standard (60%) compared to the ones that use groundwater (42.9%). In this last group, those that explore the Guarani aquifer were superior (52.3%) than the others (46.6%).

Pré-oxidação e adsorção em carvão ativado granular para remoção dos herbicidas Diuron e Hexazinona de água subterrânea

The cultivation of sugarcane demands the use of herbicides such as Diuron and Hexazinone. Some supply wells from Ribeirão Preto, SP, Brazil, built in the Guarani Aquifer are located in recharge points, and the presence of sandy Quartzarenic Neosol in these areas increases the vulnerability of the groundwater to contamination from herbicides This paper reports the water quality monitored in some wells located in the recharge area and the removal of Diuron and Hexazinone by means of adsorption in granular activated carbon (GAC), preceded or not by preoxidation with chlorine and chlorine dioxide in a pilot plant. The results indicated that Diuron was more strongly adsorbed than Hexazinone and that the saturation time of the GAC in the test with preoxidation was shorter than in the test without preoxidation, which may have occurred mainly due to the formation of by-products that competed with the adsorption of the herbicides.

Hidrogeoquímica do aqüífero guarani na área urbana de ribeirão preto (SP)

This work evaluated the hydrogeochemistry of the Guarani Aquifer in the urban area of Ribeirão Preto, São Paulo State. Thirty one sampling points were established and it was carried out field campaigns in 7 and 8 July 2005, analyzing the following parameters: conductivity, temperature, pH, turbidity, color, dry residue, dissolved oxygen, Ca2+, Mg2+, Na+, K+, Fe3+, Al3+, HCO3-, SO42-, PO43-, NO3-, Cl- and F-. The results indicated that the groundwaters in the urban area of Ribeirão Preto pH possess slightly acid, low conductivity, turbidity, color and dissolved oxygen inside the limits established for drinking waters. The ionic composition indicated that the groundwaters have low cations and anions concentration, being they classified as soft water and calcium-bicarbonated. Statistical tests suggested that conductivity and pH are controlled for the calcite dissolution (CaCO3) during the water/rock interaction process. Besides, it is possible to conclude that the high NO3- and PO43- concentrations found in the groundwater in the urban area of Ribeirão Preto are originated due to anthropogenic activities.

Litogeoquímica E aspectos Petrogenéticos dos basaltos da Província Magmática do Paraná na porção centro-norte do Estado de São Paulo

The petrographic and geochemical characterization of flood basalts of Serra Geral Formation are here presented. The investigated areas are situated in four different regions of São Paulo state: Jaú, Ribeirão Preto, Franca and Fernandópolis. They represent almost the total area of outcrops of basalts in the São Paulo State. The petrographical data reveals that these rocks are constituted mainly by plagioclase (30-40%), pyroxenes, augite and pigeonita (20-30%) and magnetite (5-15%), and show a intergranular texture and its varieties intersertal, hialophitic and pilotaxitic. The geochemical data show a basic and tholeiitic affinity of the studied basalts, with high-Ti content (TiO2 > 1.8%), typical of the northern region of Paraná Basin. Three different magma-types were recognized: Paranapanema, Urubici and Pitanga. The first magma-type is concentrated in the Fernandópolis region, the second in the Franca region, and the Pitanga occurs in the Ribeirão Preto and Jaú regions. The distribution patterns of these magma-types and the detailed study of geochemical data showed that they are, probably, generated by a melting of a continental lithospheric mantle.

Influência do arcabouço hidroestratigráfico nas ocorrências de arsênio em águas subterrâneas ao longo do corredor termal do rio Uruguai (Argentina - Brasil - Uruguai)

The Thermal Corridor of Uruguay River is located in the triple border of Argentine, Brazil and Uruguay, and shows an intense economic thermal tourism activity, mainly based on groundwaters from Guarani Aquifer System (GAS). Recent studies have pointed out the occurrence of high concentrations of arsenic (>10 μg/L) in GAS groundwater in this area. The complex geological and hydrogeological framework in the area is associated to the Paraná Basin geological evolution south of the Assuncion-Rio Grande Arch; it encompass paleozoic marine sequences and continental sequences permian/eotriassic to mesozoic in age, which are covered by basaltic lavas of Serra Geral Formation. Iron oxide coatings have been described in sandstones of Buena Vista and Sanga do Cabral formations, which underlie GAS units. Arsenic occurrence is associated to sodium bicarbonate groundwater with pH values over 8.0. Arsenic is released to groundwater by desorption from iron oxides/hydroxides, as result of the higher pH of these waters, indicating that arsenic is released from the units that underlie GAS units. Increase in chromium and uranium concentrations are also related to high pH groundwaters, thus indicating special care on using groundwater from this region.

Groundwater quality on a waste disposal area due to sand mining activities in São Paulo state, Brazil

This investigation reports the results of a study realized in an area related to the development of sand mining activities, which belongs to Sibelco Mineração Ltd. The site is located around Analândia municipality, nearly in the center of São Paulo State, Brazil. Hydrochemical analyses of groundwater were realized under different periods of time, with the aim of evaluating the possibility of release of several constituents to the liquid phase, which may be a source of pollution of the surface hydrological resources and of the deeper Guarani aquifer. This is because the site is located at the recharge area of Guarani aquifer and some tributaries from Corumbataí river may also be suffering contamination, implying on the impoverishment of the water quality that are very important resources in the region, as they are extensively used for drinking purposes, among others.© 2011 WIT Press.

Aplicação da eletrorresistividade na caracterização do meio hidrogeológico na cidade de JI-paraná (RO)

The Ji-Paraná city (RO) it doesn't possess public system of collection and treatment of sewers, being the waters residuárias produced by the local population thrown at sewages. Traditionally, many inhabitants use wells amazon extracted underground water or tubular shallow in the urban zone. The study accomplished in the Nova Brasília neighborhood for Silva (2009) revealed that the local aquifer is strongly contaminated for nitrate, originated of the decomposition of the organic matter deposited at the sewages local maidservants. With the objective of detecting areas with high concentrations originating from organic compositions of septic sewages, geophysical risings were accomplished, later related with analyses physical-chemistries in samples of groundwaters obtained in several wells installed in the Nova Brasília neighborhood, besides of soil samples descriptions in zone not saturated obtained in wells. The results obtained by the geophysical rehearsals they reveal that the polluting feather not migrates through the zone saturated, arriving with relative easiness to the aquifer, reaching in some points, superior depth to 34 m reached by the geoelectrical profiling.

Geotermometria das águas hipertermais do Sistema Aquífero Guarani no estado de São Paulo

Several geothermometers have been employed to determine the expected temperature in the groundwater reservoirs, most part of them based on the chemical equilibrium between thermal groundwaters and minerals which constitute the aquifer framework. Based on this principle, groundwater from Guarani Aquifer System, which presents temperatures upon to 38°C, classified as hyperthermal by the Brazilian Mineral Water Code, had their chemical composition evaluated with the main purpose to determine the expected temperatures in the reservoir based on the application of several geothermometers. These groundwaters can be classified as Na-HCO3 type evolving to Na-HCO3-Cl-SO4 type due the increase in sulphate and chloride concentrations. Measured groundwater temperatures show a good correlation with the depth of the aquifer, indicating an average geothermal gradient of 27.7°C/km. The lowest geothermal gradients, bellow 25°C/km, are observed in the central portion of the study area; meanwhile the highest gradients are observed in NE and W portions of the study area. Quartz equilibrium based geothermometers return temperature over the measured temperatures, meanwhile chalcedony geothermometer returns temperatures near the measured in the wells, except for the wells located in the area which presents the lowest geothermal gradients. The geothermometers based on the equilibrium between Na/K have returned temperatures diverse from the measured at the field, meanwhile the geothermometer based on the equilibrium between Na/K/Ca has presented good match with groundwater which present temperatures under 50°C, due the thermodynamic equilibrium between these waters and feldspars. Geothermometers show evidences about mixtures between groundwaters from GAS and underlying units, especially in wells located in the SW portion of the study area.

Radon emissions related to the granitic Precambrian shield in southern Brazil

The equivalent uranium (eU) activity concentration was analysed in selected granite samples at several sites in Porto Alegre, Southern Brazil, to obtain information on the radon (222Rn) generation by the aquifer rock matrices. Radon analyses of ground water and soil samples were also performed. Several samples exhibited a dissolved 222Rn activity concentration exceeding the World Health Organization maximum limit of 100 Bq l-1. The dissolved radon content in ground waters from the Fractured Precambrian Aquifer System exhibited a direct significant correlation with the eU in the rock matrices, which is a typical result of water-rock interactions. Variation in the soil's porosity was confirmed as an important factor for 222Rn release, as expected, due to its gaseous nature. Thus, although the calcic-alkaline to alkaline Precambrian granitoid rocks of the study area are important reservoirs for underground resources, they can release high amounts of radon gas into the liquid phase. © 2013 Copyright Taylor and Francis Group, LLC.

Caracterização geofísica em aterro de resíduos sólidos para avaliação de condicionantes de instabilidade geotécnica

The disposal of solid waste can create environmental problems, in addition to the potential risk of instability even in planned geotechnical works, such as provisions in stacks or high ends of the landfill, because they represent mere adjustments in civil engineering works. The Leme city, SP, generates about 35 t/day of municipal waste, that are deposited in a landfill located in the Barro Preto neighborhood. This work conducted a geophysical survey, based on geotechnical instability evidence in area, for analysis of the conditioners that cause on the sides leachate resurgence landfill and its relationship to mass movements and ravines installation in cover soil, with consequent waste exposure. The results indicate horizons of low resistivity connected with resurgence points generated by the organic matter decomposition contained in the waste. Such horizons result in leachate concentration in some places, which, in turn, may lead to loss of cohesion of the materials constituting the residues mass. The results are areas with mass flow by rotational movements, which, together with the surface flow of rainwater, evolves into ravines and exposed residues, preferably at the resurgence point. The leachate flow on the surface affects areas beyond the limits at landfill with direct impact on local agriculture and risk to pedestrians using the highway bordered by the landfill beyond the soil and the local aquifer.