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41.
A New Reference Material for Tritium Organic Molecules in Sediment: Results of an International Intercomparison Exercise 下载免费PDF全文
Phillip E. Warwick Ian W. Croudace Richard M. Marsh Nicolas Baglan Sang Bog Kim 《Geostandards and Geoanalytical Research》2018,42(2):253-262
Solid matrix 3H reference materials are challenging to prepare given the volatile nature of 3H and are often unrepresentative of the range of 3H forms that may be encountered during routine analysis. As a result, few 3H reference materials are currently available, undermining verification of analytical techniques for environmental 3H measurement. To address this, an International Working Group on Organically‐Bound Tritium Analysis determined to produce a tritium natural matrix reference material (NMRM). The reference material comprises marine sediment blended with sewage sludge contaminated with 3H‐organic species arising from authorised discharges from a radiopharmaceutical manufacturing site. Previous studies have demonstrated that the 3H species have persisted in the environment over three decades providing valuable supporting data to underpin the characterisation of the NMRM. The preparation and characterisation of the NMRM are described along with the subsequent application of the reference material in an international intercomparison exercise involving nineteen laboratories from nine countries. A reference value of 168 ± 22 Bq kg?1 was derived from the data arising from the proficiency test. 相似文献
42.
Zexuan Xu Nicolas Massei Ingrid Padilla Andrew Hartmann Bill Hu 《Environmental Earth Sciences》2018,77(12):476
This introductory editorial paper provides a review and prospective outlook of the achievements and challenges in karst research under a changing environment. A brief discussion of the past and future karst research has been focused on: (1) data and new technologies; (2) modeling of karst flow and reactive transport; (3) responses of karst hydrosystems to climate variability and changes across scales. 相似文献
43.
Sumanta Dandapath Bishwajit Chakraborty Nicolas Maslov Siddaiah M. Karisiddaiah Dhrupad Ghosh William Fernandes Andrew Menezes 《Marine and Petroleum Geology》2012,29(1):115-128
Here we apply quantitative technique to describe the seafloor seepages based on the multi-beam backscatter and bathymetric investigations to characterize the pockmark morphology. The variable seafloor backscatter strength for coarser seafloor sediments are related to the diagenesis derived from biodegraded seepages. In this regard, box counting method is used to estimate ‘fractal dimension’ for backscatter imagery data of 398 blocks. These blocks are further sub-grouped into six classes depending on the spread of pockmark related seepages. The study area lies 102 km west off Marmagao along the central west coast of India which contains pre-dominantly (70%) gas-charged sediments. Comparison between the estimated self-similar fractals reveals that there is approximately 97% correlation between the box (Dbox) and information (Dinfo) dimensions. Box dimension–derived fractal dimension values, suggest that the seepages are more along the fault trace in deeper waters, in comparison to sparsely distributed shallow water seepages. Besides, this poor seepage is confined within the smooth to moderately rough seafloor. It is established that the high backscatter strength along the upper slope of the pockmark region having higher fractal dimensions reflects multifractal behavior of seepage distribution. Entire area indicates patchy seepage patterns as supported by estimated fractal values showing intermittent fluctuations, which emphasizes non-linear behavior. Estimated self organizing criticality (SOC) parameters for six representative blocks reveal that the nature of pockmark, fault trace, sediment nature coupled with slumping of pockmark’s wall, sediment movement due to bottom currents are controlling the dynamic balance in the area seepage system. Further, our study emphasizing the multifractal behavior of seepage blocks, clearly depicts the drift in the seepage pattern. 相似文献
44.
Kenneth Neil Mertens Manuel Bringué Nicolas Van Nieuwenhove Yoshihito Takano Vera Pospelova Andre Rochon Anne De Vernal Taoufik Radi Barrie Dale R. Timothy Patterson Kaarina Weckström Elinor Andrén Stephen Louwye Kazumi Matsuoka 《第四纪科学杂志》2012,27(7):734-744
Process length variation of cysts of the dinoflagellate Protoceratium reticulatum (Claparède et Lachmann) Bütschli in surface sediments from the North Pacific was investigated. The average process length showed a significant inverse relation to annual seawater density: σt annual = ?0.8674 × average process length + 1029.3 (R2 = 0.84), with a standard error of 0.78 kg m?3. A sediment trap study from Effingham Inlet in British Columbia revealed the same relationship between average process length and local seawater density variations. In the Baltic–Skagerrak region, the average process length variation was related significantly to annual seawater density: σt annual = 3.5457 × average process length ? 993.28 (R2 = 0.86), with a standard error of 3.09 kg m?3. These calibrations cannot be reconciled, which accentuates the regional character of the calibrations. This can be related to variations in molecular data (small subunit, long subunit and internal transcribed spacer sequences), which show the presence of several genotypes and the occurrence of pseudo‐cryptic speciation within this species. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
45.
Julien Berger Olivier Féménias Nicolas Coussaert Jean-Claude C. Mercier Daniel Demaiffe 《Contributions to Mineralogy and Petrology》2007,153(5):557-575
Ultramafic and mafic xenoliths of magmatic origin, sampled in the Beaunit vent (northern French Massif Central), derive from
the Permian (257 Ma) Beaunit layered complex (BLC) that was emplaced at the crust-mantle transition zone (∼1 GPa). These plutonic
xenoliths are linked to a single fractional crystallisation process in four steps: peridotitic cumulates; websteritic cumulates;
Al-rich mafic cumulates (plagioclase, pyroxenes, garnet, amphibole and spinel) and finally low-Al mafic cumulates. This sequence
of cumulates can be related to the compositional evolution of hydrous Mg basaltic magma that evolved to high-Al basalt and
finally to andesitic basalt. Sr and Nd isotopic compositions confirm the co-genetic character of the various magmatic xenoliths
and argue for an enriched upper mantle source comparable to present mantle wedges above subduction zones. LILE, LREE and Pb
enrichment are a common feature of all xenoliths and argue for an enriched sub-alkaline transitional parental magma. The existence
of a Permian magma chamber at 30 km depth suggests that the low-velocity zone observed locally beneath the Moho probably does
not represent an anomalous mantle but rather a sequence of mafic/ultramafic cumulates with densities close to those of mantle
rocks. 相似文献
46.
Manfred Baer Nicolas Deichmann Jochen Braunmiller John Clinton Stephan Husen Donat Fäh Domenico Giardini Philipp Kästli Urs Kradolfer Stefan Wiemer 《Swiss Journal of Geoscience》2007,100(3):517-528
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during
2006. During this period, 572 earthquakes and 91 quarry blasts were detected and located in the region under consideration.
Of these earthquakes, two occurred in conjunction with the construction of the new Gotthard railway tunnel and 165 were induced
artificially by the stimulation of a proposed geothermal reservoir beneath the city of Basel. With 20 events with M
L
≥ 2.5, five of which were artificially induced, the seismic activity in the year 2006 was far below the average over the
previous 31 years. Nevertheless, six events were felt by the public, most prominently the strongest of the induced Basel events
(M
L
3.4), which caused some non-structural building damage. Noteworthy are also the two earthquakes near Cortaillod (M
L
3.2), on the shore of Lake Neuchatel, and in Val Mora (M
L
3.5), between the Engadin and Val Müstair, as well as the 42 aftershocks of the M
L
4.9 Vallorcine earthquake, between Martigny and Chamonix, of September 2005.
Editorial handling: Stefan Bucher 相似文献
47.
Transport and deposition of suspended particles in saturated porous media: hydrodynamic effect 总被引:1,自引:1,他引:1
Nasre-Dine Ahfir Hua Qing Wang Ahmed Benamar Adbellah Alem Nicolas Massei Jean-Paul Dupont 《Hydrogeology Journal》2007,15(4):659-668
A laboratory study was undertaken to determine the transport and deposition rate of suspended particles in columns of saturated porous media (gravel and glass beads), where the porous media were subjected to steady-state flow. Silt particles with a mode of 14 μm diameter (used as the suspended particles) and fluorescein (as the conservative tracer) were injected into the columns in short pulses. The breakthrough curves were competently described with the analytical solution of a convection–dispersion equation with a first-order deposition rate. The experiments were performed using different flow rates. The suspended particle size distribution, the porous media, and the flow rates themselves were the main factors retained in this study to investigate the mechanisms governing the transport and deposition kinetics in detail. The results showed the existence of a flow rate, beyond which suspended particles travel faster than the conservative tracer. A decrease of the deposition rate of suspended particles beyond a critical flow velocity was also observed. Such behaviour led to consideration of the couple hydrodynamic-gravity forces at high flow rates. As the hydrodynamic force increases, particle deposition rates are reduced due to the effect of hydrodynamic forces inhibiting the deposition. 相似文献
48.
49.
Jean-Fran?ois?DeconinckEmail author Stephen?P.?Hesselbo Nicolas?Debuisser Olivier?Averbuch Fran?ois?Baudin Julian?Bessa 《International Journal of Earth Sciences》2003,92(2):255-266
We present a dataset including clay mineralogy, gamma-ray spectrometry, organic matter content and magnetic susceptibility of the Hettangian to lowest Sinemurian successions of Dorset and Somerset, southern UK (Blue Lias Formation, Bristol Channel and Wessex basins). In both areas, the clay assemblages comprise predominantly detrital illite, kaolinite and illite/smectite mixed layers. Clays probably originated from the erosion of the Hercynian massifs, the relative proportions of kaolinite and illite being modulated by arid-humid climatic fluctuations. The organic matter (OM) content (types II to IV) ranges up to 12% in both areas. A clear stratigraphical trend in clay mineral assemblages is apparent in Somerset, whereas in Dorset sharp contrasts between adjacent horizons and a greater dilution by carbonate mask the long-term evolution. Correlations between both areas based on similar vertical trends in clay mineral abundance support the suggestion of a hiatus within the angulata Zone of the Dorset succession. As expected, the kaolinite/illite ratio correlates with the Th/K ratio deduced from gamma-ray spectrometry. However, significant departures from the correlation occur in OM-rich intervals, suggesting that Th may be partly adsorbed on to OM particles. Surprisingly, high magnetic susceptibility correlates with abundant kaolinite, not with Fe-rich clays, indicating either that kaolinite is accompanied by a soil-inherited magnetisable phase (possibly iron oxide) or that illite-rich rocks are more strongly diluted by carbonate than are kaolinite-rich strata. 相似文献
50.
Time-relative positioning makes use of observations taken at two different epochs and stations with a single global positioning
system (GPS) receiver to determine the position of the unknown station with respect to the known station. The limitation of
this method is the degradation over time of the positioning accuracy due to the temporal variation of GPS errors (ionospheric
delay, satellite clock corrections, satellite ephemerides, and tropospheric delay). The impact of these errors is significantly
reduced by adding to the one-way move from the known to the unknown station, a back move to the known station. A loop misclosure
is computed from the coordinates obtained at the known station at the beginning and at the end of the loop, and is used to
correct the coordinates of the unknown station. The field tests, presented in this paper, show that using the loop misclosure
corrections, time-relative positioning accuracy can be improved by about 60% when using single frequency data, and by about
40% with dual frequency data. For a 4-min processing interval (an 8-min loop) and a 95% probability level, errors remain under
20 cm for the horizontal components and 36 cm for the vertical component with single frequency data; and under 11 cm for the
horizontal components and 29 cm for the vertical component with dual frequency data. 相似文献