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981.
The aim of this study is to determine the total metal (aluminum, copper, manganese, nickel, lead, zinc, cadmium, iron, mercury) contents of dominant shrimp species and sediments present at 1–50 m depths of the Northern Inner Shelf of the Sea of Marmara. Shrimp and sediment samples were collected from four regions (Büyükçekmece, Silivri, Tekirda?, ?arköy) and from different depths (1, 5, 10, 20, 30, 50 m) at each region in September and November of 2003. Three shrimp species [Palaemon adspersus (Rathke, 1937), Palaemon serratus (Pennant, 1777), Parapenaeus longirostris (H. Lucas, 1846)] were identified to be dominant as a result of the examination on the obtained samples. Heavy metal contents of these three species were determined and the results were compared with the acceptable treshold values of the Seafood Standards and also with available literatures. The Cu contents were found to be higher than the treshold limits in all samples except P. longirostris from Silivri, also the Cd contents in all samples except P. adspersus from Büyükçekmece, the Zn contents only in P. adspersus and P. longirostris from Tekirda?, and the Pb contents in all species from all regions. These high values are the indicator of industrial pollution. There is not any data in the Seafood Standards about Mn, Ni, Fe and Al contents in shrimp species. The values of these metal contents were given in the present study. The examination of total metal distributions in bottom surface sediment samples in the Northern Inner Shelf of the Sea of Marmara showed that the determined values were higher than the shale average at some depths of examined stations.  相似文献   
982.
Storm surges: perspectives and options   总被引:4,自引:1,他引:3  
This review paper attempts to summarize the scattered and fragmented knowledge about past and possible future changing storm-surge statistics using the particularly well-studied case of the North Sea as an example. For this region, a complete and robust analysis methodology has been developed in recent years. This methodology is based on dynamical and statistical models. Using the concept of dynamical downscaling, development during recent decades, when sufficiently good and homogeneous weather data exist, has been “reconstructed,” and scenarios of possible future change are described. “Localization” allows estimation of changes at specific sites, e.g., harbors. As local water-level statistics depend not only on climate variations but also on local modifications of the local bathymetry, new options for adaptation emerge. For the case of Hamburg, an option for such future adaptations is discussed.  相似文献   
983.
There is little information regarding pollutant levels in farmed fish, and the risks associated to consumption. This study was designed to assess levels of exposure to metals, organochlorinated compounds, polycyclic aromatic hydrocarbons (PAHs) and alkylphenols (APEs) in farmed sea bass Dicentrarchus labrax from five aquacultures located in Southern Europe. Additionally, several biochemical responses (metallothionein, 7-ethoxyresorufin O-deethylase, vitellogenin) were determined as complementary tools. The obtained data indicate that pollutants exposure in farmed fish is similar to the levels reported in wild specimens from the area. Nonetheless, some biochemical responses were observed in the studied organisms, viz. metallothionein induction in Cu exposed organisms, and 7-ethoxyresorufin O-deethylase (EROD) and vitellogenin induction in PAHs and APEs exposed ones. The study further supports the usefulness of the biomarker approach as a first screening method to discriminate between basal and high levels of exposure in cultured fish.  相似文献   
984.
以历史上黄河下游的决溢频率为泥沙灾害的代用指标;研究了黄河下游历史泥沙灾害的宏观特征.研 究表明,气候因素对黄河下游决溢频率有深远的影响.隋唐以前,天然植被尚未遭到显著破坏,当湿润指标 增大时,有利于植被的生长,故黄河下游决溢频率减小.10世纪以后,二者的关系与此相反,当湿润指标增 大时,决溢频率也增大,反之亦然.每世纪大旱年颁次与每世纪决溢频次之间呈明显正相关,说明目前受到 各方面广泛关注的黄河下游“小水大灾”现象,在历史上已经存在.干旱时期中,河槽萎缩,一旦大水来 临,很容易发生决溢.以华山松树木年轮指数为气温的代用指标,研究了气温变化与决溢频率变化的关系, 结果表明,在50a的尺度上,当气温降低时,决溢频率增大,反之亦然.人类活动是影响黄河下游泥沙灾害 的重要因素.  相似文献   
985.
在分析黄河三角洲生态现状和特点的基础上 ,阐述了黄河三角洲存在的生态问题 ,并提出了生态保护对策  相似文献   
986.
Deep-sea sediments collected in two areas of the Mediterranean Sea having different sedimentological characteristics have been analyzed to determine present concentrations and inventories of 239,240Pu and to study the main mechanisms controlling them. Plutonium distribution in the deepest part of a submarine canyon (Taranto Valley, Ionian Sea) is compared to that obtained in an abyssal plain (north Algerian Plain). in the latter case, sedimentation is mainly due to the sinking of biogenic particles, while in the former lateral transport of terrigenous material along the slope of the canyon can significantly contribute to sediment accumulation on the bottom.

239,240Pu surface concentration in the canyon ranged from 0.2 to 1 Bq kg-1 (dry weight) and this was lower in the abyssal plain. in this area, plutonium was detectable only in the first 4 cm, while in the canyon it was present down to 11-15 cm. 239,240Pu inventories are 3 Bq m-2 in the plain and 45-60 Bq m-2 in the canyon, indicating considerable input of terrigenous material towards the final part of the Taranto Valley.  相似文献   
987.
利用洪水风险图指导洪泛区及城市建设   总被引:6,自引:0,他引:6  
刘树坤  沈振明 《灾害学》1991,6(4):26-31
本文就洪水风险图的概念、编制方法作了探讨,并介绍了黄河北金堤滞洪区等洪水风险图。最后就洪水风险图的应用作了分析。  相似文献   
988.
Studies on the reproductive biology of seabirds on Talan and Umara islands in 1987–1999 showed that the diet of nestlings and reproductive success of the tufted puffin (Lunda cirrhata) and horned puffin (Fratercula corniculata) considerably varied in different colonies. This was determined by differences in the hydrologic characteristics of water areas and the state of food resources in Taui Bay (the northern Sea of Okhotsk). The reproductive success of tufted puffins was higher on Umara Island due to more favorable environmental conditions and relatively stable food resources in Odyan Bay. The parameters of reproductive success and the nestling diet in tufted and horned puffins from Talan Island differed considerably. The survival of nestlings was always higher in horned puffins, which was related to some characteristics of their feeding ecology.  相似文献   
989.
由于兰州段夏季黄河水的浊度较高,直接影响了自来水厂的正常运行,而目前水厂所用工艺无法满足高浊度水的处理要求,因此,采用自主研究开发的具有特殊结构的水旋澄清池对黄河高浊度水进行了强化处理的试验研究.研究结果表明:在多点投药混合方式下,强化水旋澄清池可提高浊度的处理效果;若在投加无机絮凝剂PAC后,再投加有机絮凝剂PAM进行复配作用,不仅可降低无机絮凝剂的用量,节约制水成本,而且提高了自来水厂的出水水质;结果也表明该水旋澄清池技术能够推广应用于黄河高浊度水的强化处理工艺中.  相似文献   
990.
In recent years there has been an increase in the intensity and frequency of environmental monitoring surveys at UK sewage sludge disposal sites. These have been carried out by the regulatory authorities and by the licensees. in order to ensure maximum efficiency, a coordinated and harmonised programme of monitoring has been developed. the programme concentrates on sediment chemical and biological quality but also includes assessments of water and fish quality

In England and Wales the Ministry of Agriculture, Fisheries and Food is the regulatory authority and the Water Authorities are the licensees. the Ministry's first priority is the collection of samples for temporal trend analysis but in addition, infrequent surveys are made to check the status of the disposal site and surrounding areas. in the periods between status surveys, regular spatial surveys designed to define the area of impact are carried out by the Water Authorities.  相似文献   
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