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941.
与这两种成分有关的矿床岩性变化很大.在确定溶液源成分时,含矿母岩和与其有关的地层性质是十分重要的,这是提供一个确切的成因模式的基础.同上述两组矿床有关的一些不同的岩性特点如下: 1.火山岩和沉积岩的相对含量Cu-Zn矿床组大多数赋存在以火山岩为主的地层或火山岩派生的沉积岩不发育的地层中.如北美大多数前寒武纪矿床赋存在绿岩带以火山岩为主的岩石中.相反,芬诺斯堪的纳地盾许多前寒武纪矿床则经常分布在含有少量长英质火山岩成分的沉积岩层中.而显生 相似文献
942.
Carrasco M López-Ramírez JA Benavente J López-Aguayo F Sales D 《Marine pollution bulletin》2003,46(3):335-345
Measuring the amount of pollution is of particular importance in assessing the quality and general condition of an ecosystem. In this paper, some of the results obtained as a consequence of the specific agreement between the Environmental Agency (Consejería de Medio Ambiente, Junta de Andalucía) and the University of Cadiz to assess the environmental condition of the marine bottom and waters are showed. Physical and chemical analyses in water and sediments were undertaken at various sampling sites close to urban and industrial locations. Later on, these results were studied under statistical analysis to reveal any possible relationships between the parameters employed, and to identify any analogous behaviour between the sampling sites. Physical-chemical data revealed that sediments and waters analysed were moderately contaminated and, in addition, no great differences were found between in rising and ebbing tide conditions. Finally, considering only the pollution level, from the cluster analysis of sediments two major groups appear, one of which corresponded to those sites located in the outer bay, and the other to those situated in the inner bay. However, number 6 and 14 sampling sites cannot be associated to those groups due to be related to points with important local discharges. 相似文献
943.
Evidence of a high percentage of intersex in the Mediterranean swordfish (Xiphias gladius L.) 总被引:1,自引:0,他引:1
De Metrio G Corriero A Desantis S Zubani D Cirillo F Deflorio M Bridges CR Eicker J de la Serna JM Megalofonou P Kime DE 《Marine pollution bulletin》2003,46(3):358-361
The first evidence of the presence of intersexuality in a wild population of Mediterranean swordfish (Xiphias gladius L.) is reported. Forty of 162 specimens (25%) macroscopically classified as males, showed the presence of female germ cells within the testes. In two specimens grouped previtellogenic oocytes were present; all the other specimens possessed single scattered previtellogenic oocytes. The presence of vitellogenin was demonstrated immunohistochemically in the liver of both intersex and normal males. These findings could be due to the exposure to oestrogen-mimicking substances. 相似文献
944.
945.
Can plankton communities be considered as bio-indicators of water quality in the Lagoon of Venice? 总被引:4,自引:0,他引:4
Bianchi F Acri F Aubry FB Berton A Boldrin A Camatti E Cassin D Comaschi A 《Marine pollution bulletin》2003,46(8):964-971
This study examines whether plankton of the Lagoon of Venice could be considered as a bio-indicator of areas subjected to various anthropogenic influences. This study was a two year hydrochemical and biological survey in five areas of the Lagoon of Venice, each with different environmental conditions due to pollution from urban, industrial, thermal and agricultural wastes. Phytoplankton associations did not show any promising species. In the different lagoonal areas, this community was differentiated into its major groups. In contrast, the copepod Acartia tonsa Dana could be considered as a target species in highly eutrophic areas. 相似文献
946.
Chase ME Jones SH Hennigar P Sowles J Harding GC Freeman K Wells PG Krahforst C Coombs K Crawford R Pederson J Taylor D 《Marine pollution bulletin》2001,42(6):491-505
Gulfwatch, established in 1991, is an international contaminant monitoring program in which the blue mussel, Mytilus edulis, is used as an indicator of the level and extent of contamination in the Gulf of Maine. Since 1991, trace metals, PAHs, PCBs, and OC pesticides have been measured in mussel tissues at 56 sites. The distribution of most metals was relatively uniform throughout the Gulf with the exception of Ag, Pb and Cr. However, the concentration of organic contaminants increased in a north-to-south direction. High concentrations of contaminants were correlated with large human population density and proximity to large rivers. Temporal analysis of five sites revealed that the majority of contaminant concentrations were either unchanged or decreasing. The concentrations of most contaminants were lower than the median of the National Status and Trends (NS & T) Mussel Watch with the exceptions of Cr, Hg, Pb and sigma PCB24. Hg concentrations at > 80% of the Gulfwatch sites exceeded the NS & T median +1 SD. Gulfwatch continues as a primary contaminant monitoring program in the Gulf of Maine. 相似文献
947.
948.
本文叙述了真实时间解释的优点及有关技术,所讨论的相关技术领域是:.并行解释。.信息交换技术。.三维可视化。.综合体系。.未来的解释系统。 相似文献
949.
青藏高原东北部30ka以来的古植被与古气候演变序列 总被引:20,自引:1,他引:20
利用孢粉分析并结合沉积学及~(14)C测年等资料,阐明青藏高原东北部若尔盖高原30ka来的古植被与古气候演变序列以及主要的气候事件。古植被经历了高寒荒漠-草原和亚高山草甸-高寒荒漠-草原、沼泽和亚高山草甸-岛状森林、沼泽和草甸-云杉、冷杉林及沼泽-岛状暗针叶林、沼泽和亚高山草甸7个阶段。气候与植被相应发生了多次变化,冰后期和全新世期间的气候事件在这里均有明显表现。 相似文献
950.
为估计二维横向不均匀,非弹性介质的地面运动,将振型叠加法和有限差分方法相结合,发展一种复合技术,无论震源距大小,都可以计算地震形成的局部波场,它可考虑震源、路径和局部场地土的影响。 相似文献