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A mobile downhole fluorometer was used to detect zones of preferential groundwater tracer transport into an observation well. Identification of such zones is not possible if individual samples are collected over the well's entire screened interval. Laboratory-based tests using the fluorometer, and a purpose-built apparatus demonstrated that the fluorometer could be used with tracers to characterise well water flow regimes. During field investigations in a porous aquifer, the fluorometer monitored tracer concentrations in an observation well with a 12-m-long screen, 10 m down the hydraulic gradient from a fully penetrating injection well. Test results showed that the tracer occurred in the observation well over a discrete 2.5-m-thick interval. Single-well dilution test and vertical-flow data indicated that water entered the well at additional depths, but no tracer was detected at these levels. A numerical model reproducing dilution test concentration profiles indicated that water entered the well in many of these horizons at comparable velocities to those in the tracer-bearing zone. These data suggest that groundwater flow direction varied with depth in the aquifer under investigation. Moreover, simulations of tracer arrival indicated that the tracer distribution observed in the observation well was derived from a horizon that may be no thicker than 0.5 m.RØsumØ Un fluorim tre a ØtØ utilisØ pour dØtecter les zones d'Øcoulement prØfØrentiel d'un traceur dans un puits d'observation. Les identifications de telles zones n'est pas possible si les Øchantillons individuels sont collectØs sur toute les longueurs des parties crØpinØes du puits. Les tests de laboratoire utilisant un fluorim tre et un dispositif adØquat ont montrØ que les fluorim tres pouvaient servir à dØfinir les rØgimes d'Øcoulement de l'eau dans les puits. Durant les investigations de terrain dans un aquif re poreux, le fluorim tre a enregistrØ les concentrations du traceur dans un puits d'observation avec une crØpine de 12 m. de long, 10 m sous le gradient hydraulique dans un puits à pØnØtration totale. Les rØsultats des tests ont montrØ que le traceur apparaissait dans un interval discret de 2.5 m de long. Un test de dilution en puits unique et des donnØes d'Øcoulement vertical ont indiquØ que l'eau rentrait dans le puits à d'autres profondeurs, mais le traceur n'a pas ØtØ dØtectØ à ces niveaux. Un mod le numØrique reproduisant le test de dilution et le profil de concentration a indiquØ que l'eau entrait dans le puits à ces niveaux à des vitesses comparables de celle du traceur. Ces donnØes sugg rent que l'Øcoulement des eaux souterraines varie avec la profondeur dans l'aquif re sous la zone d'investigation. D'ailleurs, les simulations de l'arrivØe du traceur ont montrØ que la distribution des concentrations du traceur dans le puits ne pouvaient pas Þtre dues à une couche plus fine que 0.5 m.Resumen Se utilizó un fluorómetro móvil descendente para detectar zonas de transporte preferencial de trazadores de agua subterrµnea en un pozo de observ...

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In the Southern Espinhaço Mountain Chain and in the Upper JequitinhonhaValley, magnetic soils, in different pedogenetic stages, are found to be forming over intrusions of basic lithology. The essential chemical and mineralogical properties of samples from magnetic soil profiles from those two physiographic environments in the state of Minas Gerais, Brazil, are reported. Three of the pedons (Rhodic Kandiustox -RKox, Rhodic Haplustox -RHox, and Typic Argiustoll -TAoll) were identified as being indeed developed over basic rocks; the fourth pedon (Typic Haplustox -THox) is currently forming on an acidic rock. Particle size and routine chemical analyses were performed on samples from all horizons of the four selected soil profiles. For a deeper insight into the dominant mineralogy of each diagnostic soil horizon, the elemental contents, expressed in terms of the corresponding metal cation oxides, namely Fe 2 O 3 , Al 2 O 3 , and MnO 2 , were obtained from digesting the whole soil samples with sulfuric acid. A similar chemical analytical procedure was performed for the residual solid extracts obtained from attacking the whole soil materials with mixtures of (i) dithionite -citrate -bicarbonate and (ii) oxalate -oxalic acid. The soil samples were also analyzed by Mössbauer spectroscopy at room temperature (~298 °K) in an attempt to better identify the main magnetic iron oxides. Maghemite (δFe 2 O 3 ) was found in all samples and magnetite (Fe 3 O 4 ) was identified only for the sample from the Typic Argiustoll. The pedogenetic loss of silica and consequent accumulation of iron and aluminum oxides along the profile are found to be somehow correlated to the weathering sequence in the soils forming on basic rocks: TAoll < RKox < RHox.

the local and regional structural pattern of volcanic edifices strongly controls the space distribution of electrical resistivity. Here we report on the structural context of the western part of the Las cañadas caldera of tenerife (Lcc) thought to have initiated the formation of the caldera. Using a new dataset of 11 audiomagnetotelluric tensors we emphasize the resistivity distribution of Ucanca caldera and propose a major revision of its extension. We find that Ucanca caldera has a limited westwards extent and that El cedro sector is a depression margin of the caldera. According to the extent of hydrothermalized rocks at the base of the Lcc wall and the distribution of Pico teide -Pico Viejo vents, we constrain the location and size of Ucanca caldera. the interpretation of these results also constrains the extension of the Icod Valley and proposes a headwall located below the Pico teide -Pico Viejo complex.