Effect of divalent cations on the kinetics of Fe(III) complexation by organic ligands in natural waters     

Manabu Fujii  Andrew L. Rose  Tatsuo Omura 《Geochimica et cosmochimica acta》2008,72(5):1335-1349

We have investigated the kinetics of Fe(III) complexation by several organic ligands including fulvic acid, citrate and ethylenediaminetetraacetic acid (EDTA). Particular attention was given to examination of the effect of competitive divalent cations (Me: Ca²⁺ and Mg²⁺) at concentrations typical of seawater on the complexation rate. All experiments were conducted in 0.5 M NaCl solution buffered with 2 mM bicarbonate at pH 8.0 in the absence and presence of Me (25 μM-250 mM). The rate constants of complex formation determined by using the competitive ligand (5-sulfosalicylic acid) method combined with visible spectrophotometry ranged from 3.3 × 10⁴ to 3.2 × 10⁶ M⁻¹ s⁻¹. The mechanism of complexation was then examined based on a kinetic model. When EDTA was used as a ligand, Me at concentrations comparable to the ligand markedly retarded the rate of iron complex formation due to the predominance of an adjunctive pathway (where iron-ligand complex is formed via direct association of iron to Me-ligand complex). In contrast, the competing effect of Me on iron complexation by citrate and fulvic acid was observed only when the Me concentration was in excess of the ligand by more than a factor of 10-1000. The kinetic model suggests that iron complexation by fulvic acid occurs predominantly via a disjunctive pathway (where iron complexation by ligand occurs after dissociation of Me from Me-ligand complex) at concentrations of divalent cations and natural organic matter typical of natural waters including seawater and freshwater.  相似文献   

Subglacial comminution in the deforming bed: Inferences from SEM analysis     

Kathryn C. Rose  Jane K. Hart 《Sedimentary Geology》2008,203(1-2):87-97

This study investigates the variations in erosional processes beneath Briksdalsbreen; a Norwegian valley glacier, with a thin coarse grained deforming bed. The subglacial zone was investigated in situ, close to the central glacial flow line (Site A) and close to the valley wall (Site B), via boreholes. The till was collected using two different sediment samplers and the bed was examined using a borehole video camera. In order to evaluate how representative borehole sampling was of the subglacial environment, the results from in situ subglacial samples were compared with random samples taken from an exposed subglacial surface in the glacier foreland, as well as a sample taken from the site after glacier retreat. The results indicated that the texture of the exposed subglacial surface was similar to in situ samples from subglacial Site B (close to the valley wall), and that the samples collected with the ‘small’ sediment sampler had the closest fit. SEM analysis revealed eroded quartz grains at both sites as a result of rotation (abrasion) and fracture. The samples from close to the valley wall were very poorly sorted, with evidence for rounding and preservation of pre-weathered surfaces, which suggest that a relatively simple pattern of erosion from crushing to rotation dominated. However, the till from the centre of the glacier was better sorted, more angular, and with few pre-weathered surfaces. We suggest that this results from a more complex glacial erosional history associated with greater strain and longer residence time within the deforming layer. When compared with other deformation tills, it was confirmed that there is a relationship between grain size and erosional style. Clay-rich tills show little comminution, fine sand-rich tills generate a significant silt component, whilst the coarse sand-rich tills at Briksdalsbreen showed complex deformational styles but no significant silt component.  相似文献   

Analysis of an estuarine striped bass population: Effects of environmental conditions during early life     

William J. Kimmerer  James H. Cowan  Lee W. Miller  Kenneth A. Rose 《Estuaries and Coasts》2001,24(4):557-575

Estuarine fish populations are exposed to a variety of environmental conditions that cause both short-term variability and long-term trends in abundance. We analyzed an extensive data set for striped bass (Morone saxatilis) in the San Francisco Estuary to refine our understanding of how environmental variability influences recruitment. We examined the effects of environmental variability during early life stages on subsequent recruitment (age 3 yr), and the degree to which conditions in early life may have contributed to a long-term decline in abundance of adult striped bass in the San Francisco Estuary. Survival from egg to young-of-the-year varied strongly with freshwater flow; this effect apparently occurred within the first week or two of life, a time period that encompasses transport of eggs and larvae from the rivers to rearing areas and the onset of feeding. The rate of freshwater flow to pumping facilities that export freshwater from the system had small or sporadic effects on survival during the first month or two of life. Although many young striped bass between ages 2 and 8 mo were entrained in export pumping facilities, the resulting high mortality was unrelated to total mortality rates determined from field data on young striped bass. This lack of effect was apparently due to strong density-dependent mortality occurring between ages 1 mo and 3 yr (Kimmerer et al. 2000). The available data do not support previously suggested relationships between recruitment and freshwater flow during early life, or between gross estimates of pesticide input and survival of early life stages. We used a simple life-cycle model to show that various combined factors could have led to a decline in adult abundance, particularly a large and increasing adult mortality, but that events early in life probably did not contribute substantially to the decline. These results demonstrate that several decades of monitoring data from numerous life stages are needed to distinguish among alternative hypotheses about environmental influences on populations of estuarine fish.  相似文献   

Analytical Procedures for the Measurement of Boron Isotope Compositions by Ion Microprobe in Meteorites and Mantle Rocks   总被引：3，自引：1，他引：3  

Marc Chaussidon  François Robert  Denis Mangin  Pascal Hanon  Estelle F. Rose 《Geostandards and Geoanalytical Research》1997,21(1):7-17

An analytical procedure has been developed to measure in situ the ¹¹ B/¹⁰ B ratio in terrestrial basaltic rocks and meteoritic chondrules having B concentration of less than 1 μg g^?1 using a small radius ims3f ion microprobe. The central difficulties for these measurements are (i) the removal of the trace amount of B contamination introduced in the sample during polishing, (ii) the precise calibration of instrumental mass fractionation of B isotopes and (iii) the low count rates of ¹⁰ B and ¹¹ B. Contamination experiments conducted with isotopically labelled B enriched in ¹⁰ B showed that ultrasonic cleaning in bi-distilled water (< 1 ng g^?1 B) and pre-sputtering of the analysed area decrease B contamination to the level of 0.01 μg g^?1. Analyses of isotope standards spanning a range of ¹¹ B/¹⁰ B between 3.93 and 4.20 showed that instrumental mass fractionation was constant within? during one session of analyses. Repeated analyses of a standard glass showed a reproducibility of instrumental mass fractionation between February 1991 and October 1996 of 1.3. Taking into account all sources of error, boron isotope measurements are accurate to within 5 for meteoritic samples having B contents in the range 0.1 to 1 μg g^?1. A slightly better accuracy of 1.5 can be achieved for basaltic glasses which can be sputtered with very intense primary beams.  相似文献   

A comparison of the climatology of a tropospherestratosphere-mesosphere model with observations     

Steven Pawson  Ulrike Langematz  Arnold Meyer  Peter Strauch  Silke Leder  Klaus Rose 《Climate Dynamics》1991,5(3):161-174

Mean fields from a perpetual January simulation of a GCM extending from the surface to 0.01 hPa (near 80 km) are compared to observations. The zonal mean temperature and wind fields correspond quite well with reality; the low stratosphere, especially in the polar night, is too cold, but warmer than in the original version of the model, with an upper boundary at 25 hPa. Mean fields at standard levels show that the major features of the troposphere are represented by the model, but rather over emphasised; the stratospheric winter polar vortex is too strong, too cold, and too barotropic; it resembles an `undisturbed' January rather than the climatology. Differences in the stationary eddy activity between the extended and orginal versions of the model are noted, and used to explain some differences between the two simulations.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute für Meteorology. Guest Editor for these papers is Dr. L. Dümenil  相似文献   

Stratigraphy of the Toba Tuffs and the evolution of the Toba Caldera Complex,Sumatra, Indonesia   总被引：3，自引：0，他引：3  

Craig A Chesner  William I Rose 《Bulletin of Volcanology》1991,53(5):343-356

During the past 1.2 m.y., a magma chamber of batholithic proportions has developed under the 100 by 30 km Toba Caldera Complex. Four separate eruptions have occurred from vents within the present collapse structure, which formed from eruption of the 2800 km³ Youngest Toba Tuff (YTT) at 74 ka. Eruption of the three older Toba Tuffs alternated from calderas situated in northern and southern portions of the present caldera. The northern caldera apparently developed upon a large andesitic stratovolcano. The calderas associated with the three older tuffs are obscured by caldera collapse and resurgence resulting from eruption of the YTT. Samosir Island and the Uluan Block are two sides of a single resurgent dome that has resurged since eruption of the YTT. Samosir Island is composed of thick YTT caldera fill, whereas the Uluan Block consists mainly of the Oldest Toba Tuff (OTT). In the past 74000 years lava domes have been extruded on Samosir Island and along the caldera's western ring fracture. This part of the ring fracture is the site of the only current activity at Toba: updoming and fumarolic activity. The Toba eruptions document the growth of the laterally continuous magma body which eventually erupted the YTT. Repose periods between the four Toba Tuffs range between 0.34 and 0.43 m.y. and give insights into pluton emplacement and magmatic evolution at Toba.  相似文献   

Water resource management in karstic catchments: the case of the Asso Torrent basin (Southern Italy)     

Marco Delle Rose  Corrado Fidelibus 《Environmental Earth Sciences》2016,75(10):892

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Linked to Landscape: Assessing Urbanization in Germany through Landscape and Economic Factors     

Rose Keller  Colin Vance 《The Professional geographer》2017,69(3):424-437

The ongoing encroachment of urban land into natural landscapes has resulted in the degradation of ecosystems throughout Europe. Understanding why the share of urban land has increased is important for managing urban growth and maintaining ecosystem services. We estimate a model of landscape change that integrates geospatial and socioeconomic data in a spatial autoregressive model to explain the variance in urban growth observed in Germany between 2000 and 2006. In doing so, we test several determinants of urbanization identified by theoretical frameworks from landscape ecology and economics, including landscape pattern and transit infrastructure. The results show that despite planning guidelines and policies to promote dense development, urban growth has been extensive. Regions with a high degree of fragmented land and the prevalence of environmental amenities are characterized by particularly strong growth, pointing to challenges in crafting landscape policies that balance economic development with environmental conservation.  相似文献   

On two beds of re-deposited crag shells in the vicinity of Yarmouth,Norfolk     

C.B. Rose 《Proceedings of the Geologists' Association. Geologists' Association》1862,1(8):192-194

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Diel vertical migration and shoaling heterogeneity in Atlantic redfish: effects on acoustic and bottom-trawl surveys     

Gauthier  Stephane; Rose  George A. 《ICES Journal of Marine Science》2005,62(1):75-85

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