Relación entre la permeabilidad teórica y experimental en suelos del entorno de Oviedo (Asturias, NW de España) Relationship between theoretical and experimental permeability in soils around Oviedo (Asturias, NW of Spain)

Resumen: Se ha estudiado la permeabilidad al agua de tres suelos del entorno de Oviedo (N de España) y su relación con algunas de sus propiedades índice. En campo, se realizó una caracterización y clasificación geotécnica, distinguiéndose un aluvión (Nora), coluvión (Ules) y eluvión (Piedramuelle). En laboratorio, se ha medido varias propiedades índice para clasificar los suelos según el Sistema Unificado de Clasificación de Suelos (SUCS). Se han determinado los coeficientes de permeabilidad teóricos y experimental (permeámetro de carga constante), realizándose una comparación entre ellos y su relación con algunas propiedades índice.Palabras clave: Suelos, permeabilidad, SUCS, límites de Atterberg.Abstract: The permeability to water of three soils in the surroundings of Oviedo (N of Spain) and its relationship with some of their index properties has been studied. The characterization and geotechnical classification made in the field allow us to distinguish three soil types: an alluvial soil (Nora), a colluvial soil (Ules) and an eluvial soil (Piedramuelle). The index properties for classifying soils according to the Unified System of Soil Classification (USCS) have been measured in the laboratory. The theoretical and experimental permeability coefficients have been determined, using a steady flow permeameter for the experimental one. The comparison between these coefficients and their relationship with the soil index properties have been studied.Keywords: Soils, permeability, USCS, Atterberg limits.

Petrography and Petrochemical Characteristics of Rare Metal Pegmatites around Oro, Southwestern Nigeria

Petrographic and geochemical evaluation of pegmatite bodies occurring as discontinuous dykes have been studied in Oro area of southwestern Nigeria, with a view to determine the compositional characteristics that may be related to Ta-Nb mineralization potentials. They are found intruding semi discordantly, the older assemblages of quartz mica schist and granite gneiss. A total of twenty-eight samples comprising whole rock pegmatites and eluvial soils were analyzed for major, trace and rare earth elements using (ICP-AES) geochemical method which show the pegmatite samples to be generally highly siliceous with SiO2 values ranging from (71.49-97.77%) with an average of 86.43% in the whole rock samples, and it also ranges from (41.88-57.99%) with an average of 48.43% in the eluvial soil samples, while Al2O3 content is as high as 25.87% in the eluvial soil samples and 6.86% in the whole rock samples depicting the complexity of the pegmatite rock. Variation plots of K/Rb versus Rb, Ta versus Rb, Ta versus Nb, Ta versus K/Cs, Ta versus Cs+Rb and Ta versus Cs discriminant plot indicate the potentials of rare metal mineralization.

A MICROPEDOLOGICAL STUDY OF ELUVIAL SOIL HORIZONS

Three distinctive types of banded fabric related to the degree of eluviation were observed in Ae horizons of Saskatchewan soils. In addition, a type of intertextic fabric and cleavage block fabric were found to be characteristic of the upper and lower portions respectively of Ae horizons. Although essentially similar fabrics can occur within Ae horizons of Chernozemic, Solonetzic, Podzolic, and Gleysolic soils, the occurrence of specific fabric types appears to be related to the degree of eluviation which the horizons have undergone and bears a general relationship to the macrostructure exhibited by the soil.

Notes on the Bionomics of Glossina swynnertoni, Austen

1. G. swynnertoni is a source of danger to man and to cattle. Until reclamation was started it was rapidly advancing in the Shinyanga District and was driving the native population in front of it.2. Round Shinyanga this species occurs in gently undulating country supporting four main types of vegetation, namely:— (a) a Commiphora Fischeri community found on the well-drained rises with a good grass growth ; (b) a Lannea humilis-Commiphora Schimperi community on low-lying hard-pan areas in which the grass is poor and patchy ; (c) communities in which the grass growth is good and the main trees are Acacia spp. ; (d) a plains community, partly treeless, partly covered with shadeless woods of the small gall acacias, which are swampy during the rains and very dry at other periods of the year ; during the dry season the trees are completely leafless, and very dry and severe conditions prevail.3. Game is in moderate numbers throughout the year, so that there is no lack of food in any type of vegetation.4. The majority of flies living in the hard-pan areas obtain and digest their food there. Flies behave similarly in the C. Fischeri association, but some of them whilst searching for food may encounter a hard-pan area, where they will continue their search for food. When they get food they may or may not return to the C. Fischeri association to digest it. If a fly strikes a road or open plain it will patrol this until it finds food, when it will return to more sheltered vegetation to digest it.5. G. swynnertoni is mainly a thicket-breeder, though pupae are also found under decumbent logs, overhanging rocks and in hollows at the bases of trees. Where the C. Fischeri was much broken up by valleys of hard pan, breeding was found to be taking place to the same extent in the thickets of both of these types.6. G. swynnertoni is commonest in hard pan, much less common in C. Fischeri, scarce in the Acacia bush types worked in Shinyanga, and least common in the open plains.7. When flies are numerous, each of the first three types enumerated in (2) is able to support a fly-community. When the flies are scarce, the C. Fischeri and the Acacia communities lose their flies to the hard pan and hence are little infested. The hard pan is to a far greater degree self-contained as regards the requirements of the fly.8. G. swynnertoni is commonest during the first month or two of the dry season. As the dry season progresses it decreases in numbers and reaches its minimum during the short rains. There is a rise in the short dry season following the improvement of conditions brought about by the early rains ; after this numbers remain fairly constant until the end of the long rains. Hunger and female percentage are least in the beginning of the break of the short rains.9. There is no indication that the concentrations of fly in the hard-pan areas disperse at the end of the rains.10. Like Glossina morsitans, G. swynnertoni appears to find food by sight rather than by scent. The part that scent plays in the matter has hardly been finally elucidated.11. G. swynnertoni is capable of crossing an 800 yards clearing without the assistance of game, irrespective of whether the clearing passes over alluvial or eluvial soil. It is the hungry flies mainly that cross. They are presumably searching for food.12. The hungrier a fly is the more persistent it is in following man. Males are more persistent followers than females.13. An experimental attempt was made to exterminate G. swynnertoni by hand-catching off screens in a block of 15 square miles during sixteen months. Reduction in numbers occurred, but flies continued to exist in the block because the isolating clearings were too narrow. Further, female flies do not appear sufficiently readily to catchers, so that breeding is able to continue.14. A very large rise in female percentage occurred. A similar but lower rise marked an experiment in the catching-out of G. palpalis by hand on Mugasiro Island, near Musoma, by Robert Koch in 1913. In this the catching was off man only.