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71.
According to the present concept for final storage of spent nuclear fuel in Sweden, the spent fuel, encapsulated in copper or copper/steel canisters, will be placed in tunnels in a deep rock formation. The canisters will be surrounded by compacted bentonite clay acting as a buffer material. In connection with a safety analysis of such a storage facility, the total solubility of certain elements (e.g., uranium) as well as the transport properties (e.g., retardation due to sorption on mineral surfaces) of the long-lived radionuclides released from the canister have to be predicted or measured. The chemical conditions, governing the solubility and speciation of trace elements encountered in and around the repository depend on interactions between the ground water and the engineering materials in the repository and a production of oxidants due to radiolysis in the spent fuel. In the present study the speciation and solubility of uranium and neptunium in a bentonite-ground water system and in ground waters with compositions measured at a site at äspö, SE Sweden, have been calculated. The calculations have been carried out using a recent version of the geochemical computer code PHREEQE and the database HATCHES 5.0. Predictions of the uranium and neptunium concentrations in the ground water in the vicinity of a damaged high level waste repository have also been performed. The uranium concentration in the water in the bentonite barrier is predicted to be of the same order of magnitude or lower than that found in some granitic ground waters. For neptunium the calculations are uncertain due to the small amount of experimentally determined thermodynamic data and few verifications under the conditions (pH - Eh - carbonate concentration) considered. The predicted concentrations (ca 10–12 m, corresponds to ca 0.006 Bq/l) may be regarded as high, considering the high toxicity of neptunium and its long half-life. 相似文献
72.
Karin F. Helmens Peter Kuhry Nathaniel W. Rutter Klaas Van Der Borg Arie F. M. De Jong 《Quaternary Research》1996,45(3):289-299
Palynological, paleopedological, and glacial geomorphological evidence from the area of the high plain of Bogotá in the Colombian Eastern Cordillera indicates a significant climatic warming around 18,00014C yr B.P. Comparison of dated vegetation changes, pedogenic episodes, and glacier fluctuations provides the basis for defining the so-called “La Laguna Interstadial” that lasted from 19,500 to 17,000 yr B.P. During this interstadial period, mean annual temperatures in the tropical Andes were up to 4°C higher than during the preceding and following stadial periods, when full-glacial conditions prevailed and temperatures were up to 8°C colder than at present. 相似文献
73.
The tolerance of post yolk-sac American shad Alosa sapidissima larvae to salinities typically seen in estuaries was assessed experimentally. Sixteen-day-old Hudson River (experiment I) and 35-d-old Delaware River (experiment II) larvae were held for 8 d and 9 d respectively in low (0–1‰), medium (9–11‰), and highly (19–20‰) brackish water, and mortality and growth rates were measured. Growth rates did not vary significantly among salinity treatments. Mortality in experiment I did not vary significantly among salinity treatments however, in experiment II, mortality was zero at 10‰ but higher and statistically indistinguishable between 0‰ and 20‰ In experiment II relative condition increased with salinity. These results imply that estuarine salinities neither depress growth rates nor elevate mortality rates of larval American shad when compared with freshwater conditions. We conclude that ecological factors other than the physiological effects of salinity have played more important roles in the evolution of the upriver spawning and nursery preference shown by this species. 相似文献
74.
Peter Haase Susanne Lohse Steffen Pauls Karin Schindehütte Andrea Sundermann Peter Rolauffs Daniel Hering 《Limnologica》2004,34(4):349-365
In the past, no single standardised method for sampling and sorting benthic macroinvertebrates has been implemented in Germany. Therefore, we tested the suitability of two common sorting protocols, RIVPACS and AQEM/STAR, by taking samples with each protocol at 44 sampling sites. Our results reveal that different methods deliver slightly different assessment results. Moreover these two methods differ in costs. Although the AQEM/STAR protocol takes longer than the RIVPACS protocol, we favoured the AQEM/STAR protocol because of its higher level of standardisation. In order to limit costs to an acceptable level, a modification of the AQEM/STAR protocol (MAS method) is developed. This method is highly standardised, gives stable assessment results and is relatively inexpensive (€ 224.00 for processing of an average sample). A detailed protocol of the newly developed method is given. 相似文献
75.
Rhenium–osmium ages were determined for two molybdenite samples and a Pb–Pb age was derived from bornite–chalcopyrite–magnetite at the Salobo iron oxide copper–gold deposit to determine the timing of mineralization and its relation to the nearby Old Salobo Granite. Rhenium–osmium dating of molybdenite spatially associated with copper sulfide minerals yields ages with weighted means of 2576±8 and 2562±8 Ma. Removing the error multiplier introduced by the decay constant uncertainty, appropriate for comparing ages from the same isotopic system, these data convincingly argue for two temporally separated pulses of molybdenite deposition at 2576.1±1.4 Ma (n=2) and 2561.7±3.1 Ma (n=3). The 2576±8 Ma age coincides with a previously published U–Pb age of 2573±2 Ma for the Old Salobo Granite, suggesting that main stage ore formation may have been contemporaneous with granite magmatism. The slightly younger 2562 Ma age most likely represents new molybdenite precipitation associated with the development or reactivation of local shear zones. Lead–lead stepwise leaching of copper sulfide minerals yields a less precise isochron age of 2579±71 Ma, and supports an Archean age for the Salobo ores. This is the first documentation of an Archean iron oxide copper–gold deposit, and the Re–Os and Pb–Pb geochronology herein support 2580–2550 Ma estimates for basement reactivation and regional granite magmatism associated with the development of brittle–ductile shear zones. 相似文献
76.
Isa Baud Monika Kuffer Karin Pfeffer Richard Sliuzas Sadasivam Karuppannan 《International Journal of Applied Earth Observation and Geoinformation》2010
Analyzing the heterogeneity in metropolitan areas of India utilizing remote sensing data can help to identify more precise patterns of sub-standard residential areas. Earlier work analyzing inequalities in Indian cities employed a constructed index of multiple deprivations (IMDs) utilizing data from the Census of India 2001 (http://censusindia.gov.in). While that index, described in an earlier paper, provided a first approach to identify heterogeneity at the citywide scale, it neither provided information on spatial variations within the geographical boundaries of the Census database, nor about physical characteristics, such as green spaces and the variation in housing density and quality. In this article, we analyze whether different types of sub-standard residential areas can be identified through remote sensing data, combined, where relevant, with ground-truthing and local knowledge. The specific questions address: (1) the extent to which types of residential sub-standard areas can be drawn from remote sensing data, based on patterns of green space, structure of layout, density of built-up areas, size of buildings and other site characteristics; (2) the spatial diversity of these residential types for selected electoral wards; and (3) the correlation between different types of sub-standard residential areas and the results of the index of multiple deprivations utilized at electoral ward level found previously. 相似文献
77.
Veltman K Huijbregts MA van den Heuvel-Greve MJ Vethaak AD Hendriks AJ 《Marine environmental research》2006,61(5):511-530
The bioaccumulation model OMEGA (optimal modelling for ecotoxicological applications) is used to explore accumulation of organotins in the Western Scheldt food chain, consisting of herbi-detritivores, primary and secondary carnivorous fish and a piscivorous bird. Organotins studied are tributyltin (TBT) and triphenyltin (TPT) and the respective di- and mono-organotin metabolites. Empirical elimination rate constants are compared to model predictions for organic substances and metals. It is found that field bioaccumulation ratios are higher than predicted based on elimination kinetics relevant for organic compounds. The results indicate that uptake of organotins mainly occurs via hydrophobic mechanisms, whereas elimination may occur via metal-like kinetics. This results in very low elimination rates, which are comparable to model predictions for metals. 相似文献
78.
Karin Sesetyan Mine B. Demircioglu Tamer Y. Duman Tolga Çan Senem Tekin Tuba Eroğlu Azak Özge Zülfikar Fercan 《Bulletin of Earthquake Engineering》2018,16(8):3367-3397
The seismic zoning map of Turkey that is used in connection with the national seismic design code (versions issued both in 1997 and 2007) is based on a probabilistic seismic hazard assessment study conducted more than 20 years ago (Gülkan et al. in En son verilere göre haz?rlanan Türkiye deprem bölgeleri haritas?, Report No: METU/EERC 93-1, 1993). In line with the efforts for the update of the seismic design code, the need aroused for an updated seismic hazard map, incorporating recent data and state-of-the-art methodologies and providing ground motion parameters required for the construction of the design spectra stipulated by the new Turkish Earthquake Design Code. Supported by AFAD (Disaster and Emergency Management Authority of Turkey), a project has been conducted for the country scale assessment of the seismic hazard by probabilistic methods. The present paper describes the probabilistic seismic hazard assessment study conducted in connection with this project, incorporating in an area source model, all recently compiled data on seismicity and active faulting, and using a set of recently developed ground motion prediction equations, for both active shallow crustal and subduction regimes, evaluated as adequately representing the ground motion characteristics in the region. The area sources delineated in the model are fully parameterized in terms of maximum magnitude, depth distribution, predominant strike and dip angles and mechanism of possible ruptures. Resulting ground motion distributions are quantified and presented for PGA and 5 % damped spectral accelerations at T = 0.2 and 1.0 s, associated with return periods of 475 and 2475 years. The full set of seismic hazard curves was also made available for the hazard computation sites. The second part of the study, which is based on a fault source and smoothed seismicity model is covered in Demircioglu et al. in Bull Earthq Eng, (2016). 相似文献
79.
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