The adsorption of plutonium IV and V on goethite   总被引：1，自引：0，他引：1  

Arthur L. Sanchez  James W. Murray 《Geochimica et cosmochimica acta》1985,49(11):2297-2307

The adsorption of Pu(IV) and Pu(V) on goethite (αFeOOH) from NaNO₃ solution shows distinct differences related to the different hydrolytic character of these two oxidation states. Under similar solution conditions, the adsorption edge of the more strongly hydrolyzable Pu(IV) occurs in the pH range 3 to 5 while that for Pu(V) is at pH 5 to 7. The adsorption edge for Pu(V) shifts with time to lower pH values and this appears to be due to the reduction of Pu(V) to Pu(IV) in the presence of the goethite surface. These results suggest that redox transformations may be an important aspect of Pu adsorption chemistry and the resulting scavenging of Pu from natural waters.Increasing ionic strength (from 0.1 M to 3 M NaCl or NaNO₃ and 0.03 M to 0.3 M Na₂SO₄) did not influence Pu(IV) or Pu(V) adsorption. In the presence of dissolved organic carbon (DOC), Pu(V) reduction to Pu(IV) occurred in solution. Pu(IV) adsorption on goethite decreased by 30% in the presence of 240 ppm natural DOC found in Soap Lake, Washington waters. Increasing concentrations of carbonate ligands decreased Pu(IV) and Pu(V) adsorption on goethite, with an alkalinity of 1000 meq/l totally inhibiting adsorption.The Pu-goethite adsorption system provides the data base for developing a thermodynamic model of Pu interaction with an oxide surface and with dissolved ligands, using the MINEQL computer program. From the model calculations we determined equilibrium constants for the adsorption of Pu(IV) hydrolysis species. The model was then applied to Pu adsorption in carbonate media to see how the presence of CO₃^?2 could influence the mobility of Pu. The decrease in adsorption appears to be due to formation of a Pu-CO₃ complex. Model calculations were used to predict what the adsorption curves would look like if Pu-CO₃ complexes formed.  相似文献   

North Sea troughs and plate tectonics     

Arthur Whiteman  David Naylor  Richard Pegrum  Graham Rees 《Tectonophysics》1975,26(1-2)

Interlinked roughly trilete shaped (plan) predominantly sub-Upper Cretaceous trough systems extending north-south for more than 1200 km are described for the North Sea Basin. Palimpsest tectonic controls are rejected as a major explanation of their development and an explanation in terms of lithospheric plate development is offered. The trilete trough patterns are seen as failed arms, superficial manifestations and consequences of plume or hotspot generated crestal uplifts initiated mainly in Late Carboniferous and Early Permian times over an area extending from Hatton and Rockall Banks in the west to the Skagerrak in the east. The Tertiary and Late Cretaceous broad basinal development of the North Sea Basin is seen as an inner continental margin development of the Bott and Watt type related to Cenozoic spreading of the North Atlantic and development of the Cenozoic continental margin. The Mainz trilete system may be part of the overall pattern but data is inconclusive. Close relationships exist between trough and trap formation, geothermal history and the generation, maturation and accumulation of hydrocarbons.  相似文献   

Segmentation-based approach for trend analysis and structural breaks in rainfall time series (1851–2006) over India     

Niraj Priyadarshi  Soumya Bandyopadhyay  V. M. Chowdary  K. Chandrasekar  Jeganathan Chockalingam  Uday Raj 《水文科学杂志》2020,65(9):1583-1595

ABSTRACT

This study analysed long-term rainfall data (1851–2006) over seven climatic zones of India at seasonal and annual scales based on three techniques: (i) linear regression, (ii) multifractal detrended fluctuation analysis (MFDFA) and (iii) Bayesian algorithm. The linear regression technique was used for trend analysis of short-term (30 years) and long-term (156 years) rainfall data. The MFDFA revealed small- and large-scale fluctuations, whereas the Bayesian algorithm helped in quantifying the uncertainty in break-point detection from the rainfall time series. Major break points years identified through Bayesian algorithm were 1888, 1904 and 1976. The MFDFA technique identified that high fluctuation years were between 1871–1890, 1891–1910 and 1951–1970. Linear regression-based analysis revealed 1881–1910 and 1971–2006 as break-point periods in the North Mountainous Indian region. A similar analysis was carried out for India as a whole, as well as its seven climatic zones.  相似文献   

Late Quaternary geomorphic evolution of the lower Narmada valley, Western India: implications for neotectonic activity along the Narmada–Son Fault     

L. S. Chamyal  D. M. Maurya  S. Bhandari  Rachna Raj 《Geomorphology》2002,46(3-4)

Geomorphic data combined with stratigraphic studies provide significant information to constrain timing and amount of fault movement. The lower Narmada valley lies astride the Narmada–Son Fault (NSF), an important ENE–WSW-trending tectonic element responsible for the current intraplate seismicity being experienced in the central part of the Indian plate. Varying nature and degree of tectonic movements along the NSF during Late Pleistocene and Holocene have produced four geomorphic surfaces in the lower Narmada valley: the alluvial plain (S₁), ravine surface (S₂), a gravelly fan surface (S₃) and the valley fill terrace surface (S₄). Two major phases of tectonic movements in a compressive stress regime are recorded along the NSF: slow synsedimentary subsidence of the basin during Late Pleistocene due to differential movement, followed by inversion of the basin during the Holocene marked by differential uplift along the NSF. The study suggests that the inversion of the basin is in response to the significant increase in the intensity of compressive stresses in the Indian plate mainly during the Early Holocene. The present incisive drainage and recent seismic activity indicate that the compressive stresses continue to accumulate along the NSF due to continued northward movement of the Indian plate.  相似文献   

Occurrence of volcanic ash in the Quaternary alluvial deposits,lower Narmada basin,western India     

Rachna Raj 《Journal of Earth System Science》2008,117(1):41-48

This communication reports the occurrence of an ash layer intercalated within the late Quaternary alluvial succession of the Madhumati River, a tributary of the lower Narmada River. Petrographic, morphological and chemical details of glass shards and pumice fragments have formed the basis of this study. The ash has been correlated with the Youngest Toba Tuff. The finding of ash layer interbedded in Quaternary alluvial sequences of western Indian continental margin is significant, as ash being datable material, a near precise time-controlled stratigraphy can be interpreted for the Quaternary sediments of western India. The distant volcanic source of this ash requires a fresh re-assessment of ash volume and palaeoclimatic interpretations.  相似文献   

Reconceptualizing the role of the user of spatial data infrastructure   总被引：3，自引：0，他引：3  

Nama Raj Budhathoki  Bertram Bruce  Zorica Nedovic-Budic 《GeoJournal》2008,72(3-4):149-160

Spatial data infrastructures, which are Internet-based mechanisms for the coordinated production, discovery, and use of geospatial information in the digital environment, have diffused worldwide in the last two decades. Currently, there are about one hundred spatial data infrastructures at the national level and many other at supra- and sub-national levels. These contemporary spatial data infrastructures operate with two main assumptions: formal organizations are the producers and suppliers of geospatial information; users are the passive recipients of information. The recent phenomenon of volunteered geographic information departs from these assumptions. In this paper, we argue that reconceptualizing the user of a spatial data infrastructure can accommodate this new phenomenon. Such a reconceptualization creates a middle ground between spatial data infrastructure and volunteered geographic information, which has important implications for future research.  相似文献   

Application of water quality control charts to spring monitoring in karst terranes     

Wanfang Zhou  Barry F. Beck  Arthur J. Pettit  Jie Wang 《Environmental Geology》2008,53(6):1311-1321

Presence of springs in karst terranes provides a unique opportunity to study the rather complex, multi-porosity, and multi-permeability system. When springs are used to evaluate the integrity of storage facilities for hazardous materials or waste disposal facilities constructed in karst areas, the spatial heterogeneity of karst aquifers makes intra-spring comparisons preferred statistical tests. One of the commonly used statistical tests is water quality control procedure such as Shewhart-CUSUM control charts. Appropriate application of the water quality control procedure to intra-spring monitoring depends on whether the assumptions can be justified about the aquifer that drains to the spring and the dataset collected at the spring. Violation of the assumptions would render the statistical tests invalid, which may result in a failure of the groundwater monitoring program. In intra-spring monitoring, it is the temporal variations of water quality at a karst spring need to be addressed, whereas the water quality at the spring is closely associated with the characteristics of the aquifer. The example datasets presented in the paper indicate that both false negative and false positive detections can occur if the temporal variation is not well characterized.  相似文献   

2,4,6-Trinitrotoluene in soil and groundwater under a waste lagoon at the former Explosives Factory Maribyrnong (EFM), Victoria, Australia     

Richard Martel  Timothy James Robertson  Minh Quan Doan  Sonia Thiboutot  Guy Ampleman  Arthur Provatas  Thomas Jenkins 《Environmental Geology》2008,53(6):1249-1259

Energetic materials contamination was investigated at the former Explosives Factory Maribyrnong, Victoria, Australia. Spectrophotometric/high performance liquid chromatography (HPLC) analysis was utilised to delineate a 5 tonne crystalline 2,4,6-trinitrotoluene (TNT) source in a former process waste lagoon that was found to be supplying contaminant leachate to the surficial clay aquitard with a maximum-recorded concentration of 7.0 ppm TNT. Groundwater within underlying sand and gravel aquifers was found to be uncontaminated due to upward hydraulic gradients resulting in slow plume development and propagation. Adsorption and microcosm test results from a parallel study were used as input parameters to simulate aqueous TNT transport in the clay aquitard using ATRANS20 software. The simulated TNT plume was localised within a few metres of the source, and at steady state, though leaching rate calculations suggest that without mitigation or other changes to the system, persistence of the source would be approximately 2,000 years. Remediation strategies may involve removal of the near surface source zone and infilling with an impermeable capping to impede leaching while facilitating ongoing natural attenuation by anaerobic degradation.  相似文献   

3-D reconstruction of coastal bathymetry from AIRSAR/POLSAR data   总被引：1，自引：0，他引：1  

Maged MARGHANY  Mazlan HASHIM  Arthur P.CRACKNELL 《中国海洋湖沼学报》2009,27(1):117-123

This paper introduces a new method for reconstructing three-dimensional (3D) coastal bathymetry changes from Airborne AIRSAR/POLSAR synthetic aperture data. The new method is based on integration between fuzzy B-spline and Volterra algorithm. Volterra algorithm is used to simulate the ocean surface current from AIRSAR/POLSAR data. Then, the ocean surface current information used as input for continuity equation to estimate the water depths from AIRSAR/POLSAR data. This study shows that 3D ocean bathymetry can be reconstructed from AIRSAR/POLSAR data with root mean square error of ±0.03 m.  相似文献   

The geochemistry of sediments from the northern Reykjanes Ridge and the Iceland—Faroes Ridge     

Arthur Horowitz 《Marine Geology》1974,17(2):103-122

Samples from the active Reykjanes Ridge and the inactive Iceland—Faroes Ridge have been investigated sedimentologically, mineralogically, and geochemically. The sediments display polymodal grain-size distributions and are poorly sorted, indicating deposition by various mechanisms and contributions from numerous sources. The mineralogy is fairly typical for the region and strongly reflects the large input of volcanic ash and ice-rafted material.Bulk chemical analyses indicate that the Reykjanes Ridge sediments appear to be enriched in Fe, Mn, Cu, Cr, and Zn as has been reported for other active ridges while the inactive Iceland—Faroes Ridge does not display such enrichments. The enriched metals in the ridge sediments do not show a particular affinity for any one size class. Partition studies indicate that the enriched Fe and Mn are held in separate phases while the other metals are present in all phases. Adsorption is not a major concentrating mechanism for the enhanced elements.Li distributions are apparently unaffected by active ridges and Pb seems to be partially concentrated biologically. There are indications that other criteria must be used in conjunction with bulk chemical analyses, in order to establish the presence of active ridge metal contributions.  相似文献