Sea-surface observations of the magnetic signals of ocean swells   总被引：2，自引：0，他引：2  

F. E. M. Lilley  A. P. Hitchman  P. R. Milligan  T. Pedersen 《Geophysical Journal International》2004,159(2):565-572

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Electrodialytic remediation of CCA-treated waste wood in pilot scale     

Anne J. Pedersen  Iben V. Kristensen  Lisbeth M. Ottosen  Alexandra B. Ribeiro  Arne Villumsen 《Engineering Geology》2005,77(3-4):331-338

When chromated copper arsenate (CCA)-treated wood is removed from service and turns into waste, the contents of Cu, Cr and As remain high due to the strong fixation of CCA in the wood. This high content of toxic compounds presents a disposal challenge. Incineration of CCA-treated waste wood is not allowed in Denmark; instead, the wood is to be land-filled until new methods for handling the wood are available. Since the amounts of CCA-treated wood being removed from service is expected to increase in the years to come, the need for finding alternative handling methods is very relevant. In this study, the usefulness of Electrodialytic Remediation was demonstrated for handling of CCA-treated waste wood in pilot scale. The electrodialytic remediation method, which uses a low-level direct current (DC) as the cleaning agent, combines electrokinetic movement of ions in the wood matrix with the principles of electrodialysis. It has previously been shown that it is possible to remove Cu, Cr and As from CCA-treated wood using electrodialytic remediation in laboratory scale, but until now, the method had not been studied in large scale. The pilot-scale plant used in this study was designed to contain up to 2 m³ wood chips. Six remediation experiments were carried out. In these experiments, the process was up-scaled stepwise by increasing the distance between the electrodes from initially 60 cm to finally 150 cm. The remediation time was varied between 11 and 21 days, and phosphoric acid and/or oxalic acid was used to facilitate the desorption of CCA from the wood. In the most successful of the experiments carried out, the concentration of CCA in the wood was reduced by up to 82% for Cr, 88% for Cu and at least 96% for As.  相似文献   

Case study on the strategy and application of enhancement solutions to improve remediation of soils contaminated with Cu, Pb and Zn by means of electrodialysis   总被引：8，自引：0，他引：8  

Lisbeth M. Ottosen  Anne J. Pedersen  Alexandra B. Ribeiro  Henrik K. Hansen 《Engineering Geology》2005,77(3-4):317-329

Numerous studies have been conducted with electrochemical removal of heavy metals from spiked kaolinite. Meanwhile, when moving from kaolinite to real soils, new factors must be taken into account—factors influencing, e.g., the buffering capacity of the soil against acidification and the adsorption/desorption processes of the heavy metals. The present study gives some examples where it is necessary to use an enhancement solution to aid desorption of Cu, Zn and Pb during electrodialytic treatment. Dependent on the composition of the pollution, different choices can be made. In the case of a Cu-polluted calcareous soil, ammonia may be used as enhancement solution, due to the formation of charged complexes between ammonia and Cu. Thus, Cu is mobile at high pH when ammonia is added and Cu can be removed without dissolving the calcareous parts. Zn is also mobilized by ammonia, but to a lesser extent than Cu. In the case of Cu, Zn and Pb at the same time, alkaline ammonium citrate may be a solution. It was shown that this enhancement solution could mobilize these three pollutants, but optimization of concentration and pH of the ammonium citrate is still needed. When choosing a remediation scheme for electrochemical treatment of an actual industrially polluted soil, this scheme must be chosen on basis of characterization of soil and pollution combination.  相似文献   

U/Pb ages of ophiolites and arc-related plutons of the Norwegian Caledonides: implications for the development of Iapetus     

G. R. Dunning  R. B. Pedersen 《Contributions to Mineralogy and Petrology》1988,98(1):13-23

U/Pb zircon ages are reported for four ophiolites and three crosscutting arc-related plutons from the Norwegian Caledonides. Plagiogranite differentiated from gabbro of the Karmøy ophiolite is dated at 493+7/-4 Ma whereas arc-related trondhjemite cutting this ophiolite crystallized at 485+/–2 Ma. A crosscutting clinopyroxene-phyric gabbro intrusion is dated at 470+9/–5 Ma by near concordant magmatic titanite (sphene) and discordant U-rich (2903–6677 ppm) zircon. Lower intercepts of 247+/–68 and 191+/–70 Ma defined by the plagiogranite and clinopyroxene-phyric gabbro best-fit lines may reflect a real low-T alteration/rift-related event.A plagiogranite differentiate of the Gullfjellet ophiolite complex is dated at 489+/–3 Ma and a crosscutting arc-related tonalite is 482+6/–4 Ma. Both of these ages overlap with those of the correlative rocks at Karmøy suggesting that they are parts of one ophiolitic terrane with a common history.Trondhjemite associated with the Leka ophiolite is dated at 497+/–2 Ma, indicating that supra-subduction zone magmatism there may be coeval with spreading which formed the Karmøy axis sequence.The U/Pb zircon ages of Norwegian ophiolites reported here, combined with ages of other Appalachian-Caledonian ophiolite complexes in Britain and Canada, indicate a narrow age range for the generation of at least two marginal basins in the Tremadoc-Arenig. Two spreading episodes documented at Karmøy are separated in time by intrusion of arc-related trondhjemite magmas at 485+/–2 Ma and may correlate with two separate spreading events documented in other ophiolites.The Solund/Stavfjorden ophiolite, at 443+/–3 Ma, is the only late Ordovician ophiolite yet documented in the entire Appalachian-Caledonian Orogen and it probably represents a small, short-lived marginal basin late in the history of the Iapetus Ocean. It is correlative with Caradocian ensialic marginal basin magmatism in Wales and the Trondheim region, and with tholeiitic gabbro-diorite plutons that intruded Newfoundland ophiolites in a tensional regime after emplacement of the ophiolites over the continental margin.  相似文献   

Comment on ‘Three-dimensional interpretation of multiple-source bipole-dipole resistivity data using the apparent resistivity tensor’ by H.M. Bibby and G.W. Hohmann1     

Xiaobo Li  Laust B. Pedersen 《Geophysical Prospecting》1994,42(5):525-526

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Geology, magmatic affinity and geotectonic environment of some Caledonian ophiolites in Norway     

R.B. Pedersen  H. Furnes 《Journal of Geodynamics》1991,13(2-4)

Ophiolites within the Norwegian Caledonides were generated during at least two distinct periods, i.e. Tremadocian-Arenigian and Ashgillian. The older generation show a long-lived magmatic development (ca 500-470 Ma) with rocks that range from MORB, IAT, boninites, calc-alkaline to alkaline basalt in geochemical affinity. This development is compatible with generation in a subduction-influenced environment, and a plausible modern equivalent may be the ensimatic arc-basin evolution in the western Pacific.The metabasalts of the younger (Ashgill, 443±3 Ma) ophiolite occurrence are characterized by a dominance of N- to E-MORB compositions with subduction zone influence. The volvanics of the complex are intercalated with, and overlain by, continentally-derived sediments. Calc-alkaline as well as alkaline lavas and volcanic-lastics apparantly define late magmatic products. Associated with the youngest ophiolite is a sedimentary melange with olistoliths of mature island arc-derived volcanics, as well as clasts with MORB-IAT affinity, chert and sandstone, the latter probably derived from an accretionary prism. An Andaman Sea model appears most applicable to the youngest ophiolite/associated sediments assemblage.Contemporaneously with the renewed, Ashgillian spreading episode, widespread deposition of clastic sequences of Ashgillian age took place unconformably on the Lower Ordovician ophiolite complexes in fault controlled basins.  相似文献   

A comparison of cytochrome P4501A (CYP1A) mRNA inducibility in four species of Atlantic coast anadromous fishes     

Isaac Wirgin  Blake Konkle  Mark Pedersen  Cheryl Grunwald  Jim Williams  Simon C. Courtenay 《Estuaries and Coasts》1996,19(4):913-922

Quantification of levels of cytochrome P4501A (CYP1A) gene expression in sentinel species of fishes has been proposed as a management tool to evaluate contamination of aquatic systems. Based on preliminary studies, we hypothesized that differences in CYP1A mRNA inducibility among individuals, populations, or species might lead to spurious conclusions when using this approach in environmental monitoring programs. To address this possibility, we quantitated and compared CYP1A mRNA induction levels in four species of common Atlantic Coast estuarine fish: smooth flounder, hogchoker, striped bass, and Atlantic tomcod, which were treated with model chemicals (beta naphthoflavone (β-NF), or benzo[a]pyrene at 10 ppm) known to induce CYP1A mRNA, or were exposed to contaminated environments. Species-specific CYP1A DNA probes were generated from PCR (polymerase chain reaction) amplification of genomic DNA using conserved oligonucleotide primers, and, along with cloned rainbow trout and Atlantic tomcod CYP1A cDNA probes were used to quantify CYP1A mRNA levels in northern blot analyses. Successful PCR amplification of CYP1A hybridizable DNA fragments was observed for all four species. Results from northern blot analyses showed large differences in CYP1A mRNA induction among species; only Atlantic tomcod exhibited significant induction of CYP1A mRNA for both chemically treated (97-fold) and environmentally exposed fish (34-fold). Significant, although lower, levels of induction were observed in β-NF treated (14-fold) smooth flounder, but not in environmentally exposed smooth flounder. Only low levels (not significant) of CYP1A gene induction were detected in hogchokers and striped bass. We conclude that CYP1A mRNA inducibility differed significantly among fish taxa perhaps due to differences in regulation of gene expression, suggesting that careful selection of sentinel species should be exercised prior to the use of CYP1A mRNA induction in environmental monitoring programs. However, the significance of differences in CYP1A mRNA inducibility in relation to higher level biological endpoints has yet to be determined.  相似文献   

Controlled-source tensor magnetotelluric responses of a layered earth with azimuthal anisotropy   总被引：2，自引：0，他引：2  

Xiaobo Li  Laust B. Pedersen 《Geophysical Journal International》1992,111(1):91-103

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Simulation of the Ku-band Radar altimeter sea ice effective scattering surface     

Tonboe  R. Andersen  S. Pedersen  L.T. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(2):237-240

A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model is initialized with in situ data collected during the May 2004 GreenIce ice camp in the Lincoln Sea (73/spl deg/W; 85/spl deg/N). Our results show that the snow cover is important for the effective scattering surface depth in sea ice and thus for the range measurement, ice freeboard, and ice thickness estimation.  相似文献   

Armalcolite-bearing Fe-Ti oxide assemblages in graphite-equilibrated salic volcanic rocks with native iron from Disko,central West Greenland     

A. K. Pedersen 《Contributions to Mineralogy and Petrology》1981,77(4):307-324

Native iron-bearing strongly sediment-contaminated andesitic to dacitic lavas from the Maligât Formation on Disko contain an early phenocryst assemblage of plagioclase, low-Ca pyroxene(s) and ilmenite. The phenocrystic ilmenite has reacted to form complex Fe-Ti oxide-metal-sulphide aggregates, which contain one or more of the oxides ilmenite, armalcolite and rutile. The armalcolite is very similar to the lunar type 1 armalcolite of Haggerty (1973) and approximate compositionally the ternary system FeTi₂O₅-MgTi₂O₅-Ti₃O₅ (92 to 97 mol.%). When evidence from several salic rocks is combined the Fe-Ti oxide-metal-sulphide aggregates display reactions which may represent one isobaric invariant assemblage (ilmenite-armalcolite-rutile-iron) and the 3 boundary univariant reactions in the system Fe-Ti-O. The compositional and textural features of ferro-magnesian silicates, oxides and metals show that most rocks were affected by a rapidly declining f _{O 2} during magma ascent and cooling, as displayed in the Fe-Ti oxide-metal-sulphide aggregates by the cross-cutting of one or several T—f _{O 2} buffer curves in the system Fe-Ti-O. Prominent sulphidation reactions are observed in the oxide aggregates and are always of the type where FeO in oxide is replaced by FeS while the liberated oxygen is consumed in a reduction process. Carbon, bound as graphite or cohenite, occurs throughout the rocks and is mostly enclosed in phenocrysts and xenocrysts. When the salic magmas ascended from pre-eruption reservoirs at 1 to 1.5 kb the reduction was largely controlled by strongly pressure-dependent carbon-oxygen equilibria resulting in rapidly declining T—f _{O 2} paths recorded by the oxide assemblages. In the simplified C-O gas system carbon-barometry (Sato 1979) applied to the selected rocks would indicate final equilibrium pressures of between 10 and 100 bars. The scarcity of preserved graphite in the lavas would suggest that the carbon-controlled reductions were terminated when available carbon was exhausted during the magma ascent and solidification.  相似文献