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41.
42.
The strata of the Ireviken Event can be correlated between Gotland, Sweden and the Viki core on Saaremaa, Estonia, with a high degree of precision. Most of the ten datum planes are found with a precision of better than 0.1 m in the Lower and upper Visby Beds on Gotland and high in the Mustjala Member of the Jaani Formation on Saaremaa. Five of the latest Llandovery–early Wenlock units defined by these datum planes are between c. 0.12 and 1.77 m thick on Gotland and 0.12 and 0.67 m in Estonia. The duration of each was between a few thousand and c. 31 000 years. The stratigraphic resolution achieved in the interval of the Ireviken Event is 10,000 years. Ultimate range ends are lacking within a preceding, slightly longer interval, but the pattern of intermittent presence of some taxa agrees well with an unchanged relative rate of sedimentation. Their coeval presence in different places indicates ecological, regional or more widespread changes. 相似文献
43.
Schiedek D Broeg K Barsiene J Lehtonen KK Gercken J Pfeifer S Vuontisjärvi H Vuorinen PJ Dedonyte V Koehler A Balk L Schneider R 《Marine pollution bulletin》2006,53(8-9):387-405
During a field study performed in spring and autumn 2001 and 2002, blue mussels (Mytilus edulis) and female eelpout (Zoarces viviparus) were collected at three locations in the Wismar Bay (Baltic Sea), and several biomarkers of contaminant effects were analysed. Besides seasonal and inter-annual variations, biomarker signals were most pronounced at the location closest to Wismar Harbour (Wendorf) in both species. Lysosomal membrane stability (LMS) was lowest and acetylcholinesterase activity (AChE) was significantly reduced. Frequency of micronuclei (MN) was significantly higher (in blue mussels), indicating mutagenic effects. In eelpout elevated levels of DNA adducts, EROD induction and PAH-metabolites were measured. Metallothionein (MT), biomarker for trace metal exposure, showed a gradient only in spring. Organochlorine contaminant analyses (PCBs, DDTs) corresponded to the observed biomarker levels. The results obtained clearly demonstrate pollution effects in the southwestern Baltic Sea. Moreover, they show that a multibiomarker approach is also applicable in a brackish water environment. 相似文献
44.
Modeling of damage,permeability changes and pressure responses during excavation of the TSX tunnel in granitic rock at URL,Canada 总被引:1,自引:0,他引:1
Jonny Rutqvist Lennart Börgesson Masakazu Chijimatsu Jan Hernelind Lanru Jing Akira Kobayashi Son Nguyen 《Environmental Geology》2009,57(6):1263-1274
This paper presents numerical modeling of excavation-induced damage,
permeability changes, and fluid-pressure responses during excavation of a test tunnel associated with the tunnel
sealing experiment (TSX) at the Underground Research Laboratory (URL) in Canada. Four
different numerical models were applied using a wide range of approaches to model damage
and permeability changes in the excavation disturbed zone (EDZ) around the tunnel.
Using in situ calibration of model parameters, the modeling could reproduce observed
spatial distribution of damage and permeability changes around the tunnel as a
combination of disturbance induced by stress redistribution around the tunnel
and by the drill-and-blast operation. The modeling showed that stress-induced
permeability increase above the tunnel is a result of micro and macrofracturing
under high deviatoric (shear) stress, whereas permeability increase alongside
the tunnel is a result of opening of existing microfractures under decreased mean
stress. The remaining observed fracturing and permeability changes around the periphery
of the tunnel were attributed to damage from the drill-and-blast operation. Moreover,
a reasonably good agreement was achieved between simulated and observed
excavation-induced pressure responses around the TSX tunnel for 1 year following its
excavation. The simulations showed that these pressure responses are caused by
poroelastic effects as a result of increasing or decreasing mean stress, with
corresponding contraction or expansion of the pore volume. The simulation results
for pressure evolution were consistent with previous studies, indicating that the
observed pressure responses could be captured in a Biot model using a relatively
low Biot-Willis’ coefficient, α ≈ 0.2,
a porosity of n ≈ 0.007, and a relatively
low permeability of k ≈ 2 × 10−22 m2,
which is consistent with the very tight, unfractured granite at the site. 相似文献
45.
Thanh Son Nguyen Lennart Börgesson Masakazu Chijimatsu Jan Hernelind Lanru Jing Akira Kobayashi Jonny Rutqvist 《Environmental Geology》2009,57(6):1239-1254
In order to demonstrate the feasibility of geological disposal of spent CANDU fuel in Canada, a safety assessment was performed
for a hypothetical repository in the Canadian Shield. The assessment shows that the maximum long term radionuclide release
from such repository would meet international criteria for dose rate; however, uncertainties in the assumed evolution of the
repository were identified. Such uncertainties could be resolved by the consideration of coupled Thermal-Hydro-Mechanical-Chemical
(THMC) processes. In Task A of the DECOVALEX-THMC project, THM models were developed within the framework of the theory of
poroelasticity. Such model development was performed in an iterative manner, using experimental data from laboratory and field
tests. The models were used to perform near-field simulations of the evolution of the repository in order to address the above-mentioned
uncertainties. This paper presents the definition and rationale of task A and the results of the simulations. From a repository
safety point of view, the simulations predict that the maximum temperature would be well below the design target of 100°C;
however, the stress on the container can marginally exceed the design value of 15 MPa. However, the most important finding
from the simulations is that a rock damage zone could form around the emplacement borehole. Such damage zone can extend a
few metres from the walls of the emplacement holes, with permeability values that are orders of magnitude higher than the
initial values. The damage zone has the potential to increase the radionuclide transport flux from the geosphere; the effect
of such an increase should be taken into account in the safety assessment and mitigated if necessary by the provision of sealing
systems.
Prepared for publication in Environmental Geology.
DECOVALEX-THMC Special Issue. 相似文献
46.
The local analysis of signals arising on the sphere is a common task in earth sciences. On the real line the analytic signal turned out to be an important representation in local one-dimensional signal processing. Its generalization to two dimensions is the monogenic signal, and the properties of the analytic and the monogenic signal in the Fourier domain are well known. A generalization to the sphere is given by the Hilbert transform on the sphere known from Clifford analysis. To obtain a spectral characterization, the transform has to be decomposed into spherical harmonic functions. In this paper, we derive the spherical harmonic coefficients of the Hilbert transform on the sphere and give a series expansion. This will show that it acts as a differential operator on the spherical harmonic basis functions of the Laplace equation solution, analogously to the Riesz transform in two dimensions. This allows an interpretation of the Hilbert transform suitable for signal processing of signals naturally arising on the two-sphere. We show that the scale space naturally arising is a Poisson scale space in the unit ball. In addition, the obtained interpretation of the Hilbert transform is used for orientation analysis of plane waves. This representation is justified as a novel signal model on the sphere which can be used to construct intensity and rotation-invariant operators for local signal analysis in a scale-space concept. 相似文献
47.
48.
49.
Gunilla Ericson Gun kerman Birgitta Liewenborg Lennart Balk 《Marine environmental research》1996,42(1-4)
DNA adducts in cod embryos and larvae were analysed by 32P-postlabeling to test the hypothesis that anthropogenic substances, which could form reactive intermediates, are involved in the reproductive failure of cod (Gadus morhua) from the Baltic Sea. A comparison with cod from the Barents Sea was performed. The mean value of DNA adducts in cod embryos/larvae from the Baltic Sea was 2.3 nmol of adducts/mol nucleotides, compared to 0.12 nmol of adducts/mol nucleotides in the embryos/larvae from the Barents Sea. 相似文献
50.
The chlorophyll-a concentration is generally overestimated for the southern China coastalwaters if the default algorithm of the SeaDAS is employed. An algorithm is developed for retrieval of chlorophyll-a concentration in the Zhujiang Estuary, Guangdong Province, China, by using simulated reflectance data. The simulated reflectance is calculated corresponding to the SeaWiFS wavelength bands, via a general model by inputting measured water components, i.e. , the suspended sediment, chlorophyll-a, and yellow substance (DOC) concentration data of 130 samples. Empirical relationships of the chlorophyll-a concentration to 240 different band combinations are investigated based on the simulated reflectance data, and the band combination, R_5R_6/R_3R_4, is found to be the optimum one for the development of an algorithm valid for the Zhujiang Estuary. This algorithm is then employed to determine the chlorophyll-a concentration from SeaWiFS data. The estimated concentrations have a better accuracy than those obtai 相似文献