排序方式: 共有51条查询结果,搜索用时 15 毫秒
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Study of the contaminant transport into granite microfractures using nuclear ion beam techniques 总被引:2,自引:0,他引:2
Hydrated bentonite is a very plastic material and it is expected to enter in the rock microfractures at the granite/bentonite boundary of a deep geological high-level waste repository. This process is enhanced by the high swelling pressure of the clay. Since bentonite has a very good sorption capability for many radionuclides, the displacement of the clay might lead to a "clay-mediated" contaminant transport into the rock. The aim of this work is to study the contaminant transport into granite microfractures using nuclear ion beam techniques, and to determine to what extent the clay can favour it. To do so, bentonite previously doped with uranium, cesium and europium was put in contact with the surface of granite sheets. Granite sheets contacted with non-doped bentonite and with radionuclide solutions were also prepared as references. This allowed analysing the differences in the diffusion behaviour of the three systems: clay, radionuclides and clay plus radionuclides. A combination of Rutherford backscattering spectrometry (RBS) and other nuclear ion-beam techniques such as particle-induced X-ray emission (PIXE) and microPIXE was used to study the depth and lateral distribution of clay and contaminants inside granite. It was also tried to evaluate not only the diffusion depth and diffusion coefficients but also the different areas of the granite where the diffusants have a preferential access. 相似文献
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Tiziana Romagnoli Giorgio Bavestrello Emellina M. Cucchiari Mario De Stefano Cristina G. Di Camillo Chiara Pennesi Stefania Puce Cecilia Totti 《Marine Biology》2007,151(2):537-552
The microalgal community associated with Eudendrium racemosum, a marine hydroid widely distributed in the Mediterranean Sea, was studied during an annual cycle, at monthly frequency,
in a coastal station of the Ligurian Sea. Microalgae were represented mainly by diatoms, which exhibited higher abundance
and biomass values between autumn and spring (max 46,752 cells mm−2 and 1.94 μg C mm−2, respectively), while during summer a significant decrease was observed (min 917 cells mm−2 and 0.013 μg C mm−2). High levels of abundance of filamentous cyanobacteria were observed in summer. Spatial distribution of epibiontic microalgae
showed a markedly increasing gradient from the basal to the apical part of hydroid colonies. Considering the growth forms
of diatom communities, motile diatoms (mainly small naviculoid taxa) were the most abundant in all the periods. Adnate (Amphora and Cocconeis spp.) were distributed mainly in the basal and central part of hydroid colonies and showed two peaks (autumn and summer).
Erect forms (mainly Tabularia tabulata, Licmophora spp., Cyclophora tenuis) were mainly distributed in the apical part of the colonies and showed their maximum densities in spring–summer. Tube-dwelling
(Berkeleya rutilans, Parlibellus sp.) were observed at low densities throughout the study period, without any significant temporal or spatial variability.
Comparing the microalgal communities on marine hydroid to those grown on mimic substrata placed in the sampling station during
summer, significantly higher values of abundance were observed in the hydroid, suggesting that microalgae may benefit from
the polyp catabolites. This fact was particularly evident for the adnate diatoms, whose temporal trend paralleled the cycle
of hydroid host. 相似文献
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This paper explores how earthquake scientists conceptualise earthquake prediction, particularly given the conviction of six earthquake scientists for manslaughter (subsequently overturned) on 22 October 2012 for having given inappropriate advice to the public prior to the L'Aquila earthquake of 6 April 2009. In the first study of its kind, semi‐structured interviews were conducted with 17 earthquake scientists and the transcribed interviews were analysed thematically. The scientists primarily denigrated earthquake prediction, showing strong emotive responses and distancing themselves from earthquake ‘prediction’ in favour of ‘forecasting’. Earthquake prediction was regarded as impossible and harmful. The stigmatisation of the subject is discussed in the light of research on boundary work and stigma in science. The evaluation reveals how mitigation becomes the more favoured endeavour, creating a normative environment that disadvantages those who continue to pursue earthquake prediction research. Recommendations are made for communication with the public on earthquake risk, with a focus on how scientists portray uncertainty. 相似文献
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Pennesi C Totti C Romagnoli T Bianco B De Michelis I Beolchini F 《Water environment research》2012,84(1):9-16
Several species of seagrass and marine macrophytes were investigated for their biosorption performance in the removal of lead from aqueous solution. The effect of pH on the equilibrium of the seagrass Cymodocea nodosa as a biosorbent also was studied. It was found that increasing pH increased lead biosorption, with a maximum uptake of approximately 140 mg/g in the range pH 3.3 to 5. Equilibrium data at different pH levels were successfully fitted to competitive equilibrium models. In addition, the seaweeds belonging to different phyla (i.e., Chlorophyta, Heterokontophyta, and Rhodophyta) were studied for the effect of their structure on equilibrium at a constant pH 5. The brown algae (Heterokontophyta) showed the highest potential for lead sorption, with a maximum uptake of 220 mg/g for C. compressa and 140 mg/g for S. lomentaria. The green algae (Chlorophyta) showed lead uptake in the range 40 to 90 mg/g, and the red algae (Rhodophyta) was least effective, with uptake in the range 10 to 40 mg/g. 相似文献
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Lucile Gentaz Tiziana Lombardo Claudine Loisel Anne Chabas Marta Vallotto 《Environmental science and pollution research international》2011,18(2):291-300