Proton and Cd adsorption onto natural bacterial consortia: Testing universal adsorption behavior     

David Borrok  Jeremy B Fein 《Geochimica et cosmochimica acta》2004,68(15):3231-3238

Bacterial surface adsorption can control metal distributions in some natural systems, yet it is unclear whether natural bacterial consortia differ in their adsorption behaviors. In this study, we conduct potentiometric titration and metal adsorption experiments to measure proton and Cd adsorption onto a range of bacterial consortia. We model the experimental data using a surface complexation approach to determine thermodynamic stability constants. Our results indicate that these consortia adsorb similar extents of protons and Cd and that the adsorption onto all of the consortia can be modeled using a single set of stability constants. Consortia of bacteria cultured from natural environments also adsorb metals to lesser extents than individual strains of laboratory-cultivated species. This study suggests that a wide range of bacterial species exhibit similar adsorption behaviors, potentially simplifying the task of modeling the distribution and speciation of metals in bacteria-bearing natural systems. Current models for bacteria-metal adsorption that rely on pure strains of laboratory-cultivated species likely overpredict the amount of bacteria-metal adsorption in natural systems.  相似文献   

Azimuthal flows in the Earth's core and changes in length of day at millennial timescales     

Mathieu Dumberry  Jeremy Bloxham 《Geophysical Journal International》2006,165(1):32-46

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Ground Water Replenishment with Reclaimed Water in the City of Los Angeles     

Ali A. Karimi  Jeremy A. Redman  Roberto F. Ruiz 《Ground Water Monitoring & Remediation》1998,18(2):150-158

A two-year pilot study involving the recharge of a ground water basin with reclaimed water was completed in the city of Los Angeles. The city's Department of Water and Power is planning to initiate several ground water recharge projects using reclaimed water in the near future. One such project is the Headworks Recharge Project, the focus of this paper, Approximately 1 cfs of the Los Angeles (LA) River water comprised of 70% tertiary treated reclaimed water was recharged on a two-day wet and five-day dry cycle. The recharge water was then extracted from the basin approximately 1000 feet downgradient. Results showed greater than 4-log removal of coliform bacteria, up to 87% reduction in TOC, and compliance of the product water with federal and state drinking water standards. Model simulation showed after 15 years of recharging 3000 acre-feet per year of the LA River water and extracting about 10,000 acre-feet from the basin, the product water would contain from 5% to 15% reclaimed water. This is well below the maximum allowable limit of 20% stipulated by the California regulation.  相似文献   

Bordering on Bosnia     

Jeremy Crampton 《GeoJournal》1996,39(4):353-361

This paper begins by first giving a critique of the conflict in Bosnia from a geographical and cartographic perspective; and in particular how plans to address and solve the crisis have revolved around the cartographic delineation of territory. This is in effect a process of ‘bordering’ on Bosnia. What are the consequences of using maps to partition multi-ethnic states by constructing regions of ethnic dominance? What alternative territorial divisions might be available which are more sensitive to local use of resources? Second, the paper examines the details of the Dayton plan and argues that it is just the latest of a series of plans for Bosnia which defeat the ideal of pluralism. When the ideal of pluralism is dead, then the necessity of living together dies also. What results is not a desired Bosnia, but a divided Bosnia; one only ‘bordering’ on Bosnia in a kind of quasi- or unreal state. Throughout the paper the focus is on the role that maps have played in the conflict, how they have been contested and how they have been used to support the various interests of the parties involved.  相似文献   

Restoration of the elemental and stable-isotopic compositions of diffusionally altered minerals in slowly cooled rocks     

Robert R. Loucks 《Contributions to Mineralogy and Petrology》1996,124(3-4):346-358

 In polymineralic plutonic igneous and metamorphic rocks, slowly cooled crystals seldom retain their initial chemical compositions. This paper introduces a new, simple and widely applicable material-balance method that recovers the former compositions of minerals – regenerating in many rock types their chemical memory of the environment in which they formed – without a priori knowledge of temperature or pressure or diffusion kinetics. Restored stable-isotopic, trace-element, and/or major-element compositions provide a basis for interpretations of petrogenetic processes and conditions, including recovery of peak temperature and pressure, depth, and average diffusion distance during re-equilibration. Case studies illustrate applications of the mineral-restoration technique to regional crustal dynamics, ore metallogeny, and igneous fluid dynamics and petrogenesis. The first illustrative case addresses the controversial origin of decimetre-thick, modally graded rock layers in the Skaergaard intrusion. Layer-wide mineral-chemistry gradients that previously were ascribed a primary origin are here shown to be due to sub-solidus diffusive re-equilibration amongst minerals that initially were chemically uniform. This finding redefines the constraints to be satisfied by fluid-dynamic models of chemical differentiation processes in the magma chamber, and eliminates the basis of prior interpretations of the modally graded layers as products of in situ crystallization on the magma chamber's floor. In another case, lower crustal olivine-chromite cumulates underwent a long two-stage history of mineral-composition readjustment spanning >500° C. The technique introduced here removes the effects of the second-stage solid-state diffusion, recovering mineral compositions that represent the igneous solidus temperature at the termination of the metasomatic stage. The third example removes effects of retrograde diffusive ion-exchange from garnet, hornblende, and clinopyroxene in order to restore the rock's chemical memory of its pressure and depth of crystallization. The depth corresponds to a measure of extreme Cenozoic uplift and erosion (∼58 km) along the Main Mantle Thrust, which juxtaposes the underthrusting Indian Plate and the over-riding Kohistan island-arc terrain in the Pakistani Himalayas. Received: 28 March 1995 / Accepted: 11 April 1996  相似文献   

Geologic and atmospheric input factors affecting watershed chemistry in upper michigan     

George Rapp Jr.  Barbara W. Liukkonen  James D. Allert  John A. Sorensen  Gary E. Glass  Orie L. Loucks 《Environmental Geology》1987,9(3):155-171

The relationships between watershed variables and lakewater chemistry were examined for 53 lakes in the Upper Peninsula of Michigan to identify factors influencing lake sensitivity to atmospheric inputs. The lakes lie in three distinct geologic/geomorphic regions. Acid neutralization capacity (ANC), sulfate, and color were correlated with parameters related to atmospheric loading, watershed area and relief, hydrology, geology, and land use for the entire 53-lake set and for lower alkalinity subsets. Acid-neutralizing capacity was related to atmospheric acidic inputs and, in the southern portion of the Upper Peninsula, to the presence of mineralized groundwater inputs. In the north, ANC is correlated with hydrologic lake type and surficial deposits. Results show the highest density of acidified lakes in the northern region, which is underlain by noncalcareous sedimentary rocks. Color was related to lake size and the presence of organic soils in the watershed, whereas lake sulfate concentration was mainly influenced by atmospheric or groundwater inputs, surficial deposits, and soil type.  相似文献   

Velocities of compressional and shear waves in limestones   总被引：2，自引：1，他引：2  

Solomon Assefa  Clive McCann  Jeremy Sothcott 《Geophysical Prospecting》2003,51(1):1-13

Carbonate rocks are important hydrocarbon reservoir rocks with complex textures and petrophysical properties (porosity and permeability) mainly resulting from various diagenetic processes (compaction, dissolution, precipitation, cementation, etc.). These complexities make prediction of reservoir characteristics (e.g. porosity and permeability) from their seismic properties very difficult. To explore the relationship between the seismic, petrophysical and geological properties, ultrasonic compressional‐ and shear‐wave velocity measurements were made under a simulated in situ condition of pressure (50 MPa hydrostatic effective pressure) at frequencies of approximately 0.85 MHz and 0.7 MHz, respectively, using a pulse‐echo method. The measurements were made both in vacuum‐dry and fully saturated conditions in oolitic limestones of the Great Oolite Formation of southern England. Some of the rocks were fully saturated with oil. The acoustic measurements were supplemented by porosity and permeability measurements, petrological and pore geometry studies of resin‐impregnated polished thin sections, X‐ray diffraction analyses and scanning electron microscope studies to investigate submicroscopic textures and micropores. It is shown that the compressional‐ and shear‐wave velocities (V_p and V_s, respectively) decrease with increasing porosity and that V_p decreases approximately twice as fast as V_s. The systematic differences in pore structures (e.g. the aspect ratio) of the limestones produce large residuals in the velocity versus porosity relationship. It is demonstrated that the velocity versus porosity relationship can be improved by removing the pore‐structure‐dependent variations from the residuals. The introduction of water into the pore space decreases the shear moduli of the rocks by about 2 GPa, suggesting that there exists a fluid/matrix interaction at grain contacts, which reduces the rigidity. The predicted Biot–Gassmann velocity values are greater than the measured velocity values due to the rock–fluid interaction. This is not accounted for in the Biot–Gassmann velocity models and velocity dispersion due to a local flow mechanism. The velocities predicted by the Raymer and time‐average relationships overestimated the measured velocities even more than the Biot model.  相似文献   

Solid-state astrochemistry in star-forming regions     

Helen Fraser  David Williams  Ian Sims  Anita Richards  Jeremy Yates 《Astronomy& Geophysics》2003,44(4):4.29-4.33

Surface-catalysed chemical reactions, the molecules they form, and the implications for star formation were key themes in an international workshop on "Solid-state chemistry in star-forming regions" at the Lorentz Centre, Leiden University, the Netherlands from 14–17 April 2003. Helen Fraser, David Williams, Ian Sims, Anita Richards and Jeremy Yates report.  相似文献   

The effect of cadmium on fulvic acid adsorption to Bacillus subtilis     

Paul C. Frost  Patricia A. Maurice  Jeremy B. Fein 《Chemical Geology》2003,200(3-4):217-224

The effects of Cd on the adsorption of an aquatic fulvic acid (FA) to the surface of Bacillus subtilis were investigated from pH 2.5 to 7.0, at fixed ionic strength (0.1 M NaClO₄) and at ambient temperature (22 °C). Cd (14 mg/l) had no effect on FA adsorption at pH<5 but increased FA adsorption at pH>6. The effects of Cd (0, 14 mg/l) on FA adsorption to B. subtilis were further examined as a function of initial FA concentration (0–45 mg C/l) at pH 6.5. FA adsorption isotherms also were measured at pH 6.5 as a function of dissolved Cd concentration (0–14 mg/l) at three initial FA concentrations (4, 8, 22 mg C/l). At all FA concentrations studied at pH 6.5, FA adsorption increased with increasing initial total Cd concentration.

Under all studied conditions, preferential adsorption of high- to intermediate-molecular-weight FA components to B. subtilis resulted in a fractionation of the FA pool, with lower-molecular-weight components remaining in solution. At pH>6, Cd further enhanced the adsorption of high- to intermediate-molecular-weight FA components but did not significantly enhance the adsorption of lower-molecular-weight components. Hence, the overall process of adsorptive fractionation was not altered significantly by the presence of Cd.

Overall, the results of this study (1) demonstrate that FA adsorption to bacterial surfaces can be altered by the presence of a metal cation, and (2) provide further evidence that microbe–metal–ligand interactions may significantly affect the mobility and fate of natural organic matter in the subsurface.  相似文献   

Bradford Sturtevant, 1933-2000     

Youxue Zhang  Heidy Mader  Emily Brodsky  Hiroo Kanamori  Sue Kieffer  Jeremy Phillips  Joe Shepherd  Steve Sparks 《Bulletin of Volcanology》2002,63(8):569-571

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