Comment     

Leo A. Aroian 《Mathematical Geology》1980,12(5):441-438

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Source identification of polycyclic aromatic hydrocarbons in sediments of a creek around a flow station     

A. K. Inengite  N. C. Oforka  C. Osuji Leo 《International Journal of Environmental Science and Technology》2013,10(3):519-532

Sources of the sixteen polycyclic aromatic hydrocarbons (PAHs) in the United States Environmental Protection Agency priority pollutants list were determined in sediments of Kolo Creek using diagnostic ratios of parent PAHs[phenanthrene/phenanthrene + anthracene; fluoranthene/fluoranthene + pyrene; benz(a) anthracene/benz(a) anthracene + chrysene and indeno(1,2,3-d)pyrene/indeno(1,2,3-cd)pyrene + benzo(ghi)pyrelene]. The study was conducted over four seasons (dry, late dry, rainy and late rainy seasons). Applying cross plots of the diagnostic ratios revealed that PAHs in Kolo Creek sediment have pyrogenic origins except in the rainy season that had petrogenic origins. Comparison of diagnostic ratio values obtained from this study with literature values enabled the further classification into types of pyrogenic and/or petrogenic sources. While the pyrogenic sources of PAHs were mainly as a result of Grass/Wood combustion, the petrogenic PAHs were as result of drained diesel and lubricating oil. The predicted sources corresponded with the prevailing human activities in the vicinity, especially samples collected near a petrol station and an abattoir. This study further affirms the simplicity and accuracy of the use of diagnostic ratios for PAHs source prediction.  相似文献   

Analyses of primary remanence vector data from a large collection of lava flows: towards improved methodology in paleo-geomagnetism     

Leo Kristjansson 《Studia Geophysica et Geodaetica》2013,57(4):543-564

Research into the properties of past geomagnetic fields (paleo-geomagnetism) has been carried out worldwide for over half a century. This research utilizes rocks which are to a varying degree inadequate for that purpose, and evaluation of the results is therefore not always on firm ground. One resource which can be utilized to constrain several aspects of the interpretation of other paleo-geomagnetic data, consists of stable primary remanence vectors in large homogeneous collections of dated fresh lava flows. We outline how the available remanence data from several thousand lavas in Iceland may be analysed in a semi-quantitative way to test some of current results, methodology and concepts of paleo-geomagnetism. Among topics where such analysis provides new insights, are the geomagnetic polarity time scale, the frequency distribution of virtual geomagnetic poles in latitude and longitude, and the relative intensity of the magnetic field as a function of virtual pole latitude. Comparison of the scatter in remanence intensities and in absolute paleointensity determinations on Icelandic lavas indicates, along with other evidence, that quality criteria for the latter are in need of revising. It is also confirmed here that long-term changes have occurred in the amplitude of the geomagnetic secular variation; they should be taken into account in studies on other properties of the paleo-geomagnetic field.  相似文献   

Development without Intervention: A Successful Self‐Reliance Initiative of Rural Development and Urban Growth in The Sudan     

Mohamed Babiker Ibrahim  Leo Charles Zulu 《Geographical review》2014,104(4):481-505

We investigate the complex relationship between small‐scale farming, urban‐rural remittances and rural development. We highlight a successful, innovative self‐reliance approach in which traditional farmers changed their mode of production, improved their income, and enhanced rural development, including urbanization, in Shubbola village of western Sudan. The major initial driver was investment from remittances by family members who had migrated to urban centers, thus overcoming the problem of access to credit/capital. Consequently, the increased use of tractor technology helped farmers overcome agricultural labor shortages, and increase their farm size and productivity. Increased income from remittances and farming broadened economic and social improvements, including lifestyle and the built environment. In the process, Shubbola has grown into a viable and vibrant town, providing its residents with diverse socioeconomic services and modern infrastructure. This case illustrates the potential of development from within with minimal direct input from the government, nongovernmental organizations, and international donors.  相似文献   

Contaminant leakage from deeply buried cylindrical repositories     

J. R. Booker  C. J. Leo 《国际地质力学数值与分析法杂志》1994,18(8):565-580

The presence of any leak in a waste repository is going to cause some concern since it may lead to the contamination of the surrounding soil and groundwater. This is an important problem which occurs and recurs, sometimes despite the precautions taken to minimize the possibility of development of any leak. The effects of contaminant leakage in general are not well understood. Thus it is the aim in this paper to develop some semi-analytical solutions of leakage problems occurring in deeply buried cylindrical repositories. In the solution approach, a series of integral transforms is used to simplify the governing equations and solutions are found in the transform space before numerical inversions are applied to obtain the contaminant concentrations in real space and time. To illustrate the application of the technique, results of some leakage cases are presented.  相似文献   

Electromagnetic fields in a halfspace scattered by a buried sphere by the method of transformation of local elements     

Yong-Chia Thio  Leo John Gleeson 《Geophysical Journal International》1979,57(3):671-681

Summary. A problem in modelling electromagnetic fields used in exploration geophysics is treated mathematically. Analytical expressions are obtained for the electric field due to a harmonic current in a horizontal loop on or above a conducting ground in which is buried a conductive and permeable sphere (ore body). The loop is coaxial with the sphere. For a general time-varying current in the loop, the analysis is carried to the stage where a Fourier inversion can be used to obtain readily the electric field in the time-domain. A new relationship between spherical and cylindrical wave functions is obtained as a transformation of local elements.
Solution of this problem has not been presented before in this form. Lee's solution of 1975 which uses an integral-equation formulation treats a similar problem without taking account of differences in magnetic permeability. The effects of magnetic permeability may have important and useful implications for geophysical explorations.  相似文献   

Thermal maturity of the axial zone of the southern Apennines fold-and-thrust belt (Italy) from multiple organic and inorganic indicators     

S. Corrado  L. Aldega  P. Di Leo  C. Giampaolo  C. Invernizzi  S. Mazzoli  M. Zattin 《地学学报》2005,17(1):56-65

The reconstruction of the thermal history of folded and thrust units is crucial to define the pattern of tectonic loading and the time-space evolution of an orogen where tectonic exhumation processes occurred at shallow crustal levels. In the present study, a well-constrained reconstruction of the thermal maturity in the axial zone of the southern Apennines has been achieved by the combined use of different thermal indicators in diagenesis. The major results are: (i) documentation of a jump in thermal maturity from the Apenninic Platform derived tectonic unit (from immature to early mature stages of hydrocarbon maturation) to the Lagonegro Basin derived tectonic units (late diagenetic zone); (ii) documentation of along-strike slighter variations in the Lagonegro units, concerning thermal maturity (thus maximum burial temperatures). This can be related to changes in amounts of tectonic burial and erosion/exhumation because of the lack of cylindricity of contractional structures; (iii) recognition of an independent thermal evolution of the allochthonous chain compared with the Apulian Platform tectonic unit with Mt Alpi area (in the late mature stage of hydrocarbon generation) interpreted as a sector of localized, intense exhumation within the External Zone of the orogen.  相似文献   

Stratigraphy and paleomagnetism of a 2.9-km composite lava section in Eyjafjördur,Northern Iceland: a reconnaissance study     

Leo?KristjanssonEmail author  Agust?Gudmundsson  Bj?rn?S.?Hardarson 《International Journal of Earth Sciences》2004,93(4):582-595

Eight mountainside profiles in lava flows south of the fjord Eyjafjördur, Northern Iceland, were sampled for paleomagnetic studies. The sampling was concurrent with pilot stratigraphic mapping of the lava sequences in these and several supplementary profiles. The eight profiles are correlated with minor overlaps so that they form a composite section of 2.9 km thickness, estimated to cover the age range between about 9 and 5 million years ago (Hardarson et al. 1999). Paleomagnetic measurements made on 319 lavas generally yield primary remanence directions of high stability and within-unit consistency. Evidence for at least 17 reversals of the geomagnetic field is seen, as well as numerous field excursions. Frequent clustering of directions in successive lavas indicates that the volcanism was episodic.  相似文献   

Changes of erosive rainfall for El Niño and La Niña years in the northern Andean highlands of Peru   总被引：1，自引：0，他引：1  

Consuelo C. Romero  Guillermo A. Baigorria  Leo Stroosnijder 《Climatic change》2007,85(3-4):343-356

Information related to rainfall erosivity in the Andes is scarce. This study was carried out to determine the characteristics of rainfall events at the La Encañada watershed, northern Peru, using daily rainfall data from the 1995 to 2000 period that included all the El Niño and Southern Oscillation (ENSO) phases. Three weather stations were installed within the study area, at the top, middle and bottom of the watershed. We analysed the total amount, duration, intensity, kinetic energy and probability of return of rainfall events. In general, 80% of the rainfall events at watershed level had an average rainfall intensity lower than 2.5 mm h^?1 and only 4% had an average intensity larger than 7.5 mm h^?1. Rainfall erosivity registered at the bottom of the watershed was slightly higher than in the rest of the area. The highest intensities were observed during an El Niño year whereas a La Niña year was characterized by the highest amount of total rainfall compared to the other ENSO phases and by the low intensity rain events. Simulations using the WEPP model estimated higher sediment yield and runoff for the bottom of the watershed during a La Niña year versus El Niño or Neutral years. Even when the analysed rainfall data was too limited to conclude erosion and runoff during any ENSO phase, the simulated results showed us the trend of the behaviour of rainfall erosivity under the ENSO phases at different locations.  相似文献   

Divariant and trivariant reaction line slopes in FMAS and CFMAS: theory and applications   总被引：1，自引：0，他引：1  

Leo M. Kriegsman 《Contributions to Mineralogy and Petrology》1996,126(1-2):38-50

The theory of divariant reactions is investigated in some detail and approaches involving simultaneously operating reactions and X _Mg isopleths are combined. Using the Gibbs' method (Spear et al. 1982), a general equation is derived for X _Mg isopleth slopes in FMAS and CFMAS, which may be applied to any divariant assemblage in these systems. Isopleth slopes are calculated for a number of divariant FMAS and CFMAS reactions inferred to have operated in Sri Lankan granulites, giving more rigorous constraints on the local P-T path. Isopleth slopes are also calculated for the trivariant CFMAS reaction orthopyroxene + plagioclase = garnet + quartz. The resulting dP/dT range from +8 to +18 bar/K. Application to Sri Lankan granulites confirms an earlier hypothesis (Faulhaber and Raith 1991) that a retrograde path with a dP/dT of ～10–15 bar/K may cause garnet growth in charnockites and garnet breakdown in metabasites. It is shown here that dP/dT depends primarily on the Ca contents of garnet and plagioclase. Large variations in isopleth and reaction line slopes are possible, due to the thermodynamic effect of additional components in solid solutions, e.g. albite in plagioclase. This has a good potential for the assessment of the exact form of P-T paths. Equations to calculate isopleth slopes could be included in software packages aimed at defining P-T estimates, enabling geologists to derive realistic P-T paths.  相似文献