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Sediment samples from the continental shelf and slope off Nova Scotia were fractionated with a combination of elutriation and sieving to investigate the most easily resuspended sediment fraction and thus processes of organic deposition. Bulk sediments on the slope were enriched in carbon and nitrogen compared to those on the shelf. Fractionation indicated that<40% of bulk particulate organic carbon (POC) and particulate organic nitrogen (PON) on the shelf (from a sandy bank and a muddy-sand basin) were readily resuspendable, reflecting the large proportion of sand at these stations. On the slope however, about 85% of the bulk POC and PON was resuspendable, due to the high silt-clay content. Resuspendable fractions at all stations did not differ significantly in organic content (i.e. richness). The similarity of these fine fractions, especially at basin and slope stations suggested a related origin (surface production) for these particles. The less resuspendable coarse fraction on the shelf was an organic-poor sand; on the slope the coarse fraction consisted of benthic fecal pellets, similar in richness to the fine fractions. Comparison of predicted and measured sedimentation rates suggested that enrichment of slope sediments could only be explained by horizontal transport of shelf production. This provides further support for the hypothesis that the continental slope is a sink in the global carbon budget.  相似文献   

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《Astronomy& Geophysics》2008,49(4):4.06-4.06
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地震灾害是人类自然灾害中最为严重的一种灾害。一次破坏性地震会给人类造成巨大的生命和财产的损失,叙述了地震灾害损失的特点及开展地震保险、设立地震灾害基金业务的必要性和发展前景,提出了开展地震保险、地震灾害基金业务的一些构想。  相似文献   

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简要分析了地震行业科研专项项目档案的特点,并提出从强化档案管理意识、建立相应的规章制度、档案工作与项目建设同步、加强档案业务指导、重视档案业务技能培训和做好档案验收工作6个方面,做好专项档案工作。  相似文献   

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钱洪伟  刘舒颖 《中国地震》2021,37(3):633-640
社会救援力量业务的经费保障对社会救援队伍的建设至关重要。基于社会救援力量业务的经费保障现状,研究了为什么要进行社会救援力量业务经费保障,剖析了社会救援力量经费保障的不同阶段(经费筹措管理、经费日常管理、经费支出管理及经费监督管理)遇到的风险问题,并有针对性地提出了社会救援力量业务的经费保障风险防控优化对策。研究表明,开展此项研究有助于进一步丰富社会救援力量业务的经费保障理论体系,也有助于社会救援力量的持续健康发展。  相似文献   

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Two species of microcracks   总被引:2,自引:0,他引:2  
We identify two interrelated but independent species of microcracks with differentorigins and different distributions. One species is the classic high-stress microcracksidentified in laboratory stress-cells associated with acoustic emissions as microcracks openwith increasing stress. The other species is the low-stress distributions of closely-spacedstress-aligned fluid-saturated microcracks that observations of shear-wave splitting (SWS)demonstrate pervade almost all in situ rocks in the upper crust, the lower crust, and theuppermost 400 km of the mantle. On some occasions these two sets of microcracks may beinterrelated and similar (hence 'species') but they typically have fundamentally-differentproperties, different distributions, and different implications. The importance for hydrocarbonexploration and recovery is that SWS in hydrocarbon reservoirs monitors crack alignmentsand preferred directions of fluid-flow. The importance for earthquake seismology is that SWSabove small earthquakes monitors the effects of increasing stress on the pervasive low-stressmicrocrack distributions so that stress-accumulation before, possibly distant, earthquakes canbe recognised and impendin~ earthquakes stress-forecast.  相似文献   

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Introduction of species evolutionary sequence into the quantitative biostratigraphy is a significant work, either for studying biologic evolution or for making stratigraphic correlation and reconstructing geologic history. The quantitative biostratigraphy is to determine biostratigraphic event sequences by using probabilistic analysis. The evolutionary sequence systematics can efficiently ascertain species evolutionary sequences. Two methods have been proposed to determine the sequence of species-disappearance events: (1) species extinction events can be closed by last occurrence events using quantitative biostratigraphic analysis; (2) the duration of a species may be approximately replaced by the duration of its parent species. To combine these two methods for determining the sequence of species disappearance is the best way up to now. A consulting standard sequence that consists of the speciation sequence of Permian waagenophylloid corals and the biostratigraphic event sequence of other important fossils in Permian is used as an example. The group spearman rank-correlation test is used to test the consulting standard sequence by comparing four types of calculations and two kinds of sequences and to find abnormal events. Based on the found abnormal events in the test, the consulting standard sequence is revised to deal with different conditions. Sequences of speciation and species-disappearance, and species duration are determined. Application of species evolutionary sequence to quantitative biostratigraphy can largely improve the quality of biostratigraphic event sequence. In stratigraphic correlation, furthermore, event sequences have higher precision than range biozones.  相似文献   

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Tunicates may serve as marine pollution indicators for monitoring the release of industrial and/or radioactive wastes into the marine environment. Their ability to accumulate certain trace elements from the seawater can be employed in order to define a suitable organism as indicator for some specific pollutants. In this work the concentration of the elements cobalt, zinc, chromium, caesium, silver, iron, rubidium, selenium, scandium and antimony has been determined by instrumental neutron activation analysis and γ-ray spectroscopy, in two tunicates, Microcosmus sulcatus (Pyuridae) and Ciona intestinalis (Cionidae).According to the concentration factors found for these species Ciona intestinalis can be used as indicator for iron, while Microcosmus sulcatus as indicator for the elements selenium, chromium, zinc and cobalt.  相似文献   

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Non-indigenous species (NIS) are a growing problem globally and, in the sea, aquaculture activities are critical vectors for their introduction. Aquaculture introduces NIS, intentionally or unintentionally, and can provide substratum for the establishment of other NIS. Little is known about the co-occurrence of NIS over long periods and we document the coexistence over decades of a farmed NIS (a mussel) with an accidently introduced species (an ascidian). Both are widespread and cause serious fouling problems worldwide. We found partial habitat segregation across depth and the position of rafts within the studied farm, which suggests competitive exclusion of the mussel in dark, sheltered areas and physiological exclusion of the ascidian elsewhere. Both species exhibit massive self-recruitment, with negative effects on the industry, but critically the introduction of NIS through aquaculture facilities also has strong detrimental effects on the natural environment.  相似文献   

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Knowledge of the distribution of species life stages at multiple spatial scales is fundamental to both a proper assessment of species management and conservation programmes and the ability to predict the consequences of human disturbances for river systems. The habitat requirements of three native cyprinid species—the Iberian barbel Barbus bocagei Steindachner, the Iberian straight-mouth nase Pseudochondrostoma polylepis (Steindachner), and the Northern straight-mouth nase Pseudochondrostoma duriense (Coelho)—were examined at 174 undisturbed or minimally disturbed sites in 8 river catchments across western Iberia, by modelling occurrence and counts of species life stages at two spatial scales—large (regional) and instream (local)—using hurdle models. All the life stages of the barbel showed a negative association with upstream high-gradient river reaches, whereas juvenile P. duriense favoured such areas. Stream width and openness were negatively related with the occurrence of juvenile and small adult barbel, but not with large adults. Juvenile nase, on the other hand, were found to be mainly confined to fast-flowing habitats with high instream cover and coarser substrata. Advanced life stages of the barbel were mainly associated with the “pure” regional and shared components, whereas the purely local attributes accounted for much of the model variation among nases, in particular juveniles, and juvenile barbel. The results of this study are useful for setting or refining management goals, and highlight the need to separately consider life stages when performing conservation-related studies of species distribution.  相似文献   

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