Limitations of Monitoring Wells for the Detection and Quantification of Petroleum Products in Soils and Aquifers

Theoretical analysis and laboratory column experiments were carried out to investigate the conditions required for petroleum products (oil) to flow into a well installed through a sandy porous medium contaminated with the oil. The results indicated that oil would flow into a well only after a layer of "free oil" is formed in the adjacent porous medium. Because significant quantities of oil could be stored in the porous medium under the influence of capillary suction prior to the formation of the zone of free oil, the presence of oil in a well would indicate an advanced stage of oil contamination of the subsurface. While monitoring wells could be used to delineate the extent of the free-oil plume and the plume of dissolved petroleum constituents, they are not useful for delineating the extent of capillary held oil.
The experimental results also indicated that the ratio of the oil-layer thickness in the well to that in the porous medium is not a constant as is sometimes assumed in practice. Further, estimates of the oil thickness in the medium based on the oil thickness in wells and on capillary properties measured in the laboratory were sensitive to the values of the parameters used in these estimates. The measured thickness of the oil layer in a monitoring well alone may not yield reliable estimates of the amount of oil in the subsurface, and assuming that the oil-thickness ratio is a constant can lead to inadequate site assessments and inappropriate remedial plans.     

A statistical approach to evaluate debris avalanche activity in central Virginia

On August 19–20, 1969, the heavy rainfall associated with hurricane Camille triggered numerous debris avalanches in the Blue Ridge Province of central Virginia. Most slope movements occurred in Nelson County in an area that is predominantly underlain by Precambrian granites, gneisses, and schists. This study was undertaken to determine which geotechnical properties of soil and rock were important in promoting debris avalanche activity in central Virginia.

Twenty-one first-order drainage basins in Nelson County were randomly selected and classified as unstable based on their values of horizontal curvature and average gradient as measured on topographic maps. Slope orientation, total soil thickness, and soil horizon thicknesses were measured in the field. Soils from the study basins were tested for geotechnical properties including natural water content, grain-size distribution, Atterberg limits,in situ dry density, and shear strength. These geomorphic and geotechnical properties were subsequently analyzed to ascertain what significant differences existed at the 99% confidence level between three failure classes of unstable basins. Where rock outcrops were present, information regarding discontinuity type, orientation, spacing, continuity, roughness, waviness, aperture, and water quantity was obtained. Values of hand sample hardness were also procured. The role of these bedrock characteristics in determining unstable basin failure class was statistically analyzed at the 95% confidence level.

In general, the results indicate that basins classified as geomorphically unstable are particularly susceptible to debris avalanche activity if they contain coarse-grained soils with low values of plasticity index and moisture content. Geotechnical properties are also found to be significantly different when analyzed with respect to the underlying bedrock unit, which helps explain why basins underlain by certain bedrock units failed more often than basins underlain by other bedrock units. Differences in topography, due to the nature of the underlying bedrock unit, also explain the frequency of debris avalanche occurrences in a given bedrock unit. Characteristics of bedrock discontinuities do not appear to have influenced drainage basin failure.     

Hydrobiology of some solar salt works in India

The hydrobiology of two Indian solar salt works was investigated. A salient feature was variability in physico-chemical and biological characteristics. The filamentous cyanophyceansLyngbya majuscula andOscillatoria salina and the chlorophyceanXenococcus aceervatus were the major primary producers. Significant fauna were protozoans, rotifers and copepods.Artemia was present in only one set of solar salt pans, where it was dominant. The study illustrates the importance ofArtemia in the biological management of solar salt works. This paper is dedicated to Thiru. K. Ayyaru Vandayar, Member, Governing body, A.V.V.M. Sri Pshpam College (Autonomous), Poondi, on his sixtieth birthday     

Microseismicity and tectonics of Sinai

Five microearthquake seismographs were used at 11 sites in northern Sinai in the period February 1987 to February 1988 to study the microseismicity of the area around the Maghara coal mine for mine-development studies. A total of 270 events were recorded on 850 records. The magnitude, epicenter and depth of each event were calculated using suitable software for an Egyptian Geological Survey and Mining Authority's (EGSMA) XT computer. The interpretation of the seismic activity in the area is given in view of plate tectonics, the Sinai subplate boundary follows the Gulf of Aqaba and the Dead Sea. The plate and subplate boundaries are presently active, and there seems to be a diffuse zone of deformation between “NW Africa” and “Nubia” affecting the Cairo-Suez district.     

Generation and migration: Identity crisis and political change among the Moro of the Nuba mountains

During the past half century Moro society has undergone immense economic and social transformations. The Moro adopted rural-urban and rural-rural migration, among other things, to diversify their incomes and augment their sources of livelihood. Politically, the introduction of modern political parties since independence in 1956 and the emergence of regional movements have influenced Moro perception of their reality and relationship with their Hawazma and Jellaba neighbours.I argue in this paper that due to disappointments emanating from harsh living conditions in discordant Northern Sudanese towns, the Moro translate past experiences into a common identity. Migration, in this sense, is seen as a major factor in explaining the Moro crisis of identity and their oscillation between integration and aloofness or modernity and traditionalism.     

Geomorphology and sedimentary/biosedimentary structures of the intertidal environment along the coast of Kuwait,north-western Arabian Gulf

The coast of Kuwait can be divided into nine intertidal geomorphological subunits, of which four are found along the northern muddy shoreline and five along the southern sandy shoreline. In the north the coast is characterized by wide intertidal mudflats, bounded landward by an extensive coastal sabkha which is partly covered by sand drifts. The upper part of the intertidal environment is covered with a mixture of aeolian sands and muddy sediments of marine origin. A number of shallow tidal channels dissect the intertidal flats and small sand bars occur near the low water line. In contrast, the southern shore is characterized by relatively steep sandy beaches fronted by narrow to moderately wide rocky intertidal platforms which are partly covered by sand, bioherms, skeletal debris and algal mats. In some areas the rocky surface is dissected by numerous small gulleys and shallow channels. Multiple sand bars lying either parallel or diagonal to the shoreline are developed near the low water line. This southern intertidal environment is bounded landward by a sandy berm and a wave-cut cliff.Ripple marks are developed almost parallel to the shoreline, showing different flow directions. Energy levels are moderate to high along the southern shore, but low along the northern shore. In the south, waves induced by winds blowing mostly from the north-east and south-east form the dominant energy source, whereas tidal and wind-driven currents are the only tangible process acting along the northern shore.     

Korrelation der Sporenzonen der Oberen Trias und des Jura im Mittleren Orient und in Süddeutschland

Zusammenfassung Bei der sporenstratigraphischen Gliederung des mittleren Mesozoikums im Mittleren Orient konnten vom Nor bis zur Unteren Kreide 6 Sporenzonen unterschieden werden: Unterkreide:Ischyosporites variegatus — Rouseisporites laciniatus — Cicatricosisporites-Zone Malm:Ischyosporites variegatus — Rouseisporites laciniatus-Zone Dogger:Ischyosporites variegatus — Duplexisporites problematicus-Zone Lias:Concavisporites — Duplexisporites problematicus-Zone Rät:Concavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Ricciisporites tuberculatus-Zone Nor:Concavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Cyclotriletes oligogranifer-ZoneVergleichende Untersuchungen ergaben, daß diese Sporenzonen auch auf Süddeutschland übertragbar sind und den faunistischen Grenzen entsprechen. Nur die sporenstratigraphische Festlegung der Nor/Rätsowie der Dogger/Malm- und der Malm/Unterkreide-Grenze bedürfen noch der Verifizierung.

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In the middle Mesozoic of the Middle East 6 spore-assoziations could be distinguished from the Norian to the Lower Cretaceous: Lower Cretaceous:Ischyosporites variegatus — Rouseisporites laciniatus — Cicatricosisporites zone Upper Jurassic:Ischyosporites variegatus — Rouseisporites laciniatus zone Middle Jurassic:Ischyosporites variegatus — Duplexisporites problematicus zone Lower Jurassic:Concavisporites — Duplexisporites problematicus zone Rhaetian:Concavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Ricciisporites tuberculatus zone Norian:Concavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Cyclotriletes oligogranifer zone.The interregional validity and the correspondance of these spore zones with the faunistic boundaries could be substantiated in equivalent sequences in Southern Germany. However, the palynological definition of the Norian/Rhaetian, Middle/Upper Jurassic and Jurassic/Cretaceous boundaries have still to be confirmed in other regions since suitable sections have not been available in Southern Germany.

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Résumé Dans le Mésozoïque moyen du Moyen Orient, six zones de spores peuvent être distinguées du Norien au Crétacé inférieur: Crétacé inférieur: Zone àIschyosporites variegatus — Rouseisporites laciniatus — Cicatricosisporites Jurassique supérieur: Zone àIschyosporites variegatus — Rouseisporites laciniatus Jurassique moyen: Zone àIschyosporites variegatus — Duplexisporites problematicus Jurassique inférieur: Zone àConcavisporites — Duplexisporites problematicus Réthien: Zone àConcavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Ricciisporites tuberculatus Norien: Zone àConcavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Cyclotriletes oligogranifer Une étude comparative montre que les mêmes zones de spores existent en Allemagne du sud et qu'elles correspondent aux limites faunistiques. Toutefois, les limites Norien/ Rhétien, Dogger/Malm et Malm/Crétacé inférieur demandent à être vérifiées.

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- : : Ischyosporites variegatus —Rouseisporites laciniatus — Cicatricosisporites : Ischyosporites variegatus — Rouseisporites laciniatus : Ischyosporites variegatus — Duplexisporites problematicus : Concavisporites — Duplexisporites problematicus : Concavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Ricciisporites tuberculatus : Concavisporites — Duplexisporites problematicus — Lophotriletes sangburensis — Cyclotriletes oligogranifer. , , . , /, / / .

     

Kriging of water levels in the Souss aquifer,Morocco

Universal kriging is applied to water table data from the Souss aquifer in central Morocco. The procedure accounts for the spatial variability of the phenomenon to be mapped. With the use of measured elevations of the water table, an experimental variogram is constructed that characterizes the spatial variability of the measured water levels. Spherical and Gaussian variogram models are alternatively used to fit the experimental variogram. The models are used to develop contour maps of water table elevations and corresponding estimation variances. The estimation variances express the reliability of the kriged water table elevation maps. Universal kriging also provides a contour map of the expected elevation of the water table (drift). The differences between the expected and measured water table elevations are called residuals from the drift. Residuals from the drift are compared with residuals obtained by more traditional least-squares analysis.