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Abstract The wind generation of transverse thermocline motions in an infinitely long two‐layer channel is studied theoretically. Winds both along and across the channel are considered. Horizontal momentum transfer is parameterized by a constant coefficient of eddy viscosity. For a channel narrow compared with its internal Rossby radius of deformation, the transverse motions are uni‐modal and generated most efficiently by long‐shore winds. Theoretical results in this narrow channel limit agree well with observations made at Babine Lake, British Columbia. For a channel wide compared with its Rossby radius, the response is multi‐modal, especially for cross‐channel winds. For a model Lake Michigan, computed interfacial displacements due to a steady wind either across or along the channel are small compared with the observed displacements. However, a semi‐diurnal wind (in either direction) is in near resonance with the seventh transverse mode. Thus multi‐modal displacements as large as those observed could possibly be generated by semi‐diurnal winds across or along the channel. 相似文献
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Clinton D Church Richard T Wilkin Charles N Alpers Robert O Rye R Blaine McCleskey 《Geochemical transactions》2007,8(1):10
Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured
for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine
whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings.
Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation
are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation
and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2–3 ‰ heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved
gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron
microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and
denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately
diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine
produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur.
DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures. 相似文献
34.
Clinton R. Edwards 《GeoJournal》1992,26(4):443-452
Long before the European “Age of Discovery” began, mariners were ranging the coasts and nearer reaches of the eastern Atlantic
and the North Sea, and vessels capable of keeping the sea for more than a few days had been developed. This provided an adequate
basis upon which ships for farther voyaging could evolve. The major changes for overseas travel were in size and rig, but
also important was an eventual alteration in design incorporating the carrying capacity of large cargo vessels and the weatherly
qualities (ability to sail to windward) and maneuverability of the smaller caravel. Increase in size was necessary to carry
larger crews and supplies for their sustenance, larger cargoes, and materials for repair and replacement of ship’s gear, sails,
and the like. After much experimentation with various combinations of lateen and square sails, the full-rigged ship with relatively
small square sails on the foremast and mainmast became the standard, although the lateen was retained on the mizzen and any
other masts stepped astern of it. Other changes in design accommodated the need for armament. The result, fully developed
by the end of the sixteenth century, was the full-rigged galleon, and little in the way of substantive changes in design and
rig occurred during the next several centuries. 相似文献
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Asheka Rahman Frank T-C. Tsai Christopher D. White Douglas A. Carlson Clinton S. Willson 《Hydrogeology Journal》2008,16(4):749-764
Data integration is challenging where there are different levels of support between primary and secondary data that need to
be correlated in various ways. A geostatistical method is described, which integrates the hydraulic conductivity (K) measurements and electrical resistivity data to better estimate the K distribution in the Upper Chicot Aquifer of southwestern Louisiana, USA. The K measurements were obtained from pumping tests and represent the primary (hard) data. Borehole electrical resistivity data
from electrical logs were regarded as the secondary (soft) data, and were used to infer K values through Archie’s law and the Kozeny-Carman equation. A pseudo cross-semivariogram was developed to cope with the resistivity
data non-collocation. Uncertainties in the auto-semivariograms and pseudo cross-semivariogram were quantified. The groundwater
flow model responses by the regionalized and coregionalized models of K were compared using analysis of variance (ANOVA). The results indicate that non-collocated secondary data may improve estimates
of K and affect groundwater flow responses of practical interest, including specific capacity and drawdown.
Résumé L’intégration de données entre en jeu lorsque plusieurs niveaux intermédiaires d’assistance sont nécessaires pour corréler données primaires et secondaires de diverses manières. Le présent article décrit une méthode géostatistique qui intègre les mesures de conductivité hydraulique (K) et les données de résistivité électrique, afin d’estimer plus efficacement la distribution de K dans l’Aquifère Supérieur de Chicot, au sud-ouest de la Louisiane (Etats-Unis). Les mesures de K sont issues des pompages d’essai et représentent les données primaires (“dures”). Les données des diagraphies de résistivité électrique ont été considérées comme des données secondaires (“molles”), à partir desquelles les valeurs de K ont été déduites, par la loi d’Archie et l’équation de Kozeny-Carman. Un pseudo semi-variogramme croisé a été développé afin de pallier à l’absence de colocalisation des données de résistivité. Les incertitudes sur les semi-variogrammes automatiques et sur les pseudo semi-variogrammes croisés ont été quantifiées. Les réponses du modèle d’écoulement des eaux souterraines aux modèles régionalisés et co-régionalisés de K ont été comparés, par les analyses de variance (ANOVA). Les résultats montrent que les données secondaires non-colocalisées peuvent améliorer les estimations de K, et affecter efficacement les réponses des écoulements souterrains, y compris les débits spécifiques et les rabattements.
Resumen La integración de datos es un gran desafío cuando existen diferentes niveles de apoyo entre datos primarios y secundarios que es necesario correlacionar de varias maneras. Se describe un método geoestadístico el cual integra mediciones de conductividad hidráulica (K) y datos de resistividad eléctrica para tener una mejor estimación de la distribución de K en el Acuífero Chicot Superior del suroeste de Luisiana, Estados Unidos de América. Las mediciones de K se obtuvieron de pruebas de bombeo y representan los datos primarios (duros). Los datos de sondeos de resistividad eléctrica se consideraron como datos secundarios (suaves) y se usaron para inferir valores de K a través de la ley de Archie y la ecuación de Carman-Kozeny. Se desarrolló un pseudo semivariograma cruzado para enfrentar la falta de colocación de datos de resistividad. Se cuantificaron las incertidumbres en los auto-semivariogramas y en los semivariogramas cruzados. Las respuestas del modelo de flujo de agua subterránea por los modelos coregionalizados y regionalizados de K se compararon usando el análisis de varianza (ANOVA). Los resultados indican que los datos secundarios no colocados pueden mejorar los estimados de K y afectar las respuestas de flujo de agua subterránea de interés práctico, incluyendo capacidad específica y descenso.相似文献
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Peter Molnar Gregory A. Houseman & Clinton P. Conrad 《Geophysical Journal International》1998,133(3):568-584
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James E. Landmeyer Francis H. Chapelle Paul M. Bradley James F. Pankow Clinton D. Church Paul G. Tratnyek 《Ground Water Monitoring & Remediation》1998,18(4):93-102
Methyl tert -butyl ether (MTBE) and benzene have been measured since 1993 in a shallow, sandy aquifer contaminated by a mid-1980s release of gasoline containing fuel oxygenates. In wells downgradient of the release area, MTBK was detected before benzene, reflecting a chromatographic-like separation of these compounds in the direction of ground water flow. Higher concentrations of MTBE and benzene were measured in the deeper sampling ports of multilevel sampling wells located near the release area, and also up to 10 feet (3 m) below the water table surface in nested wells located farther from the release area. This distribution of higher concentrations at depth is caused by recharge events that deflect originally horizontal ground water flowlines. In the laboratory, microcosms containing aquifer material incubated with uniformly labeled 14 C-MTBE under aerobic and anaerobic. Fe(III)-reducing conditions indicated a low but measurable biodegradation potential (<3%14 C-MTBW as 14 CO2 ) after a seven-month incubation period, Tert -butyl alcohol (TBA), a proposed microbial-MTBE transformation intermediate, was detected in MTBE-contaminated wells, but TBA was also measured in unsaturated release area sediments. This suggests that TBA may have been present in the original fuel spilled and does not necessarily reflect microbial degradation of MTBE. Combined, these data suggest that milligram per liter to microgram per liter decreases in MTBE concentrations relative to benzene are caused by the natural attenuation processes of dilution and dispersion with less-contaminated ground water in the direction of flow rather than biodegradation at this point source gasoline release site. 相似文献
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Abstract. The benthic flora of the limestone (20%) and sand (80%) substrates typical of intermediate depths on the west coast of Florida was sampled using quadrats over a three year period. Twenty seven taxa of macroscopic algae and one seagrass, Halophila decipiens , were collected. No plants were found during February of two consecutive years. The biomass and available energy ranged from 0 (winter) to 12.4g dry weight and 128 kJ (summer) per 25cm: on the limestone outcroppings and from 0 to 4.4g dry weight and 43 kJ for the sand substrate. The flora was seasonal with no dominant macroscopic algae occurring throughout the year. The flora of the intermediate depths is subjected to abiotic disturbances and is rudcral in nature. Thus, secondary production in the extensive intermediate depths along the west coast of Florida must depend more on the inshore, shallow water seagrass communities for primary production. 相似文献
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Depth Distribution of Thalassia testudinum in two Meadows on the West Coast of Florida; a Difference in Effect of Light Availability 总被引：2，自引：0，他引：2
Abstract. Shoot density was lower, while leaf area index and above- to below-ground biomass ratios were higher for Thalassia testudinum collected from the deep edge when compared to the shallow edge of a meadow off Anclotc Key, Florida. These three characters followed patterns predicted from previous studies. The characters were reversed in order for plants from shallow and deep edges of a meadow off Egmont Key, about 50 km south of Anclote Key. Causes other than light were not evident to explain this reversal in the Egmont Key meadow. This study suggests that although light limitation may be the usual limiting factor for depth distribution in seagrass meadows, other factors cannot be ignored in many meadows along the west coast of Florida. 相似文献