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991.
渤海大型底栖动物丰度和生物量的研究   总被引:4,自引:2,他引:4  
于 1997年 6月、1998年 9月和 1999年 4月 3个航次对渤海的大型底栖动物进行了定量研究。在研究海区共采到大型底栖动物 30 6种 ,其中甲壳动物 97种 ,环节动物 95种 ,软体动物 88种 ,棘皮动物 11种 ,其它动物共 15种。其总平均丰度和生物量分别为 2 5 76 ind./m2和4 4 .4 7g/m2。渤海大部海区的总平均生物量在过去十年中可能未发生大的变化。渤海含砂量相对高的生境有较高的动物丰度 ,而在水位较深的水域 ,由于有较高的初级生产量到达底部 ,从而支持着较高的大型底栖动物的生物量。渤海海峡口可能是渤海大型底栖动物生物量的高值区  相似文献   
992.
There are more than 600 Cenozoic volcanic cones and craters with abeut 50 000 km2of lava flows in northeast China, which formed many volcanic clusters and shown the features of the continental rift - type volcanoes. Most volcanic activities in this area, especially in the east part of Songliao graben, were usually controlled by rifts and faults with the main direction of NE / NNE in parallel and become younger from the central graben towards its both sides, especially to the east continental margin. It is revealed that the volcanism occurred in northeast China was as strong as that occurred in Japan during the Miocene and the Quaternary. The Quaternary basalt that is usually distributed along river valley is called "valley basalt"while Neogene basalt usually distributed in the top of mounts is called "high position basalt". These volcanoes and volcanic rocks are usually composed of alkaline basalts with ultramafic inclusions, except Changbaishan volcano that is built by trachyte and pantellerite.  相似文献   
993.
综合运用岩心、钻井、测井及地震资料,对潍北凹陷古近系孔一段的地层特征及沉积演化进行研究。结果表明:潍北凹陷孔店组一段可以划分为3个亚段、11个砂层组。在西部鄌郚—葛沟断裂和东部昌邑—大店断裂控制下,地层东西向发育稳定,仅在北部洼陷带地层显著加厚;在北部古城—潍河口断层控制下,地层向南部超覆,地层由北向南变薄。潍北凹陷孔店组一段主要发育扇三角洲相和湖泊相,南部斜坡带发育小范围三角洲相。孔一下亚段,物源供给充足,北部洼陷带、瓦城断阶带和灶户断鼻带发育大规模的扇三角洲相;孔一中亚段,湖盆水体变浅,物源供给减少,北部洼陷带、瓦城断阶带和灶户断鼻带继承性发育扇三角洲相,但分布范围变小;孔一上亚段,湖盆水体最浅,物源供给少,全区发育滨浅湖亚相,仅在央斜4井区和昌11井区发育小范围的扇三角洲相沉积。  相似文献   
994.
时空特征分析对全面掌握水质变异规律具有重要意义,但现有的水质时空特征分析方法仍存在水质变异次序不分、水质变幅极值不清、水质评价特征值不明等不足。为更加清晰地探析水质时空特征信息,以秦淮河为研究对象,参考工程水文学经验频率法,建立“水文频率-水质”拟合曲线用于探索流域内高/低活动区不同时间段和丰/枯水期不同河段水质变异特征,并与传统的箱线图法进行对比。结果表明:与箱线图相比,“水文频率-水质”拟合曲线可量化关键水质评判点与特征值信息,使水质时空变异过程更为清晰。在时间上“水文频率-水质”拟合曲线的最佳形式为线性曲线,水质浓度一般不会发生突变;在空间上“水文频率-水质”拟合曲线的最佳形式为指数曲线,水质浓度有较大可能发生突增。各时间段高活动区氮磷浓度大于低活动区,各水体断面丰水期氮磷浓度低于枯水期。该方法分析过程简单方便,结果直观有序,能将水质信息以统计规律自动反映出来,在水质采样点、采样时间和采样频率典型时可作为优选方法用于河流水质时空特征研究。  相似文献   
995.
架状硅酸盐矿物晶体结构为氧离子作开层堆积,阳离子充填空隙而形成.矿物晶胞参数与硅氧四面体的排列方式有关,和硅氧四面体的棱长l、对棱间距T_(?)、四面体的高T_h等几何要素有确定的函数关系.  相似文献   
996.
SWAN2.0系统的设计与实现   总被引:2,自引:0,他引:2       下载免费PDF全文
强对流天气短时临近预报系统(Severe Weather Automatic Nowcasting,SWAN)是面向短时临近监测、分析、预报、预警制作等功能为一体的业务平台。SWAN2.0基于MICAPS4(Meteorological Information Comprehensive Analysis and Processing System Version 4.0,人机交互气象信息处理和天气预报制作系统)二次开发框架,采用C/S架构,服务器部署在省级,负责收集数据,运算SWAN产品;客户端部署在气象台站,实现具体的预报业务,并形成算法二次开发接口。SWAN2.0新增了三维变分风场反演、基于分雨团技术的雷达降水估测、冰雹识别等方法,实现了算法管理、产品生成、分析处理、资料检索显示、实时监控报警、预警产品制作等功能。SWAN2.0业务系统已在全国试用,在强对流天气监测、分析和短时临近预报预警中发挥了重要作用。  相似文献   
997.
Songjun Han  Fuqiang Tian 《水文研究》2018,32(19):3051-3058
Natural evaporation occurs with water transportation from an unsaturated land surface into an unsaturated atmosphere. The subprocesses at the land surface and in the atmosphere are one‐sidedly emphasized in the Penman approach and the complementary principle, in which the ratio of actual evaporation to the Penman potential evaporation is expressed as a function of the wetness state of the land surface and the atmosphere, respectively. The Penman approach and complementary principle can be integrated for completely conceptualizing the evaporation process, by expressing the evaporation ratio as a function of both the land surface and atmospheric wetness. The integrated approach has the potential to increase the accuracy of evaporation estimation while reducing the burdens of parameterization.  相似文献   
998.
The extent of glacier terminus displacement is instrumental in investigations of natural or artificial geographic changes. Its importance to earth science and engineering is reflected in the considerable efforts that have been devoted to the development of several boundary displacement analysis methods. Among the methods, the buffering-based approach compares favorably with other approaches in objectivity and robustness. However, it does not consider the relative positions of boundaries, because its buffering operation cannot determine features' relative directions. This limitation incurs inaccurate calculation results – underestimation of mean shifts and overestimation of shape variations, especially when the two compared boundaries intersect. Discrete displacement analysis (DDA), an alternative method that considers given geographic objects as a set of a finite number of points, is proposed here. In a series of tests carried out, including Jakobshavn glacier's calving front, DDA was found to correctly calculate mean shift and shape variation even in cases where the conventional buffering-based method failed. Moreover, this approach is independent of the dimension of space in which it is implemented, and thus is expected to be utilized for analysis of 3D geographic object displacement.  相似文献   
999.
On Monday, May 12, 2008, a devastating mega-earthquake of magnitude 8.0 struck the Wenchuan area, northwestern Sichuan Province, China. The focal mechanism of the earthquake was successive massive rock fracturing 15 km in depth at Yingxiu. Seismic analysis confirms that the major shock occurred on the Beichuan–Yingxiu Fault and that aftershocks rapidly extended in a straight northeast–southeast direction along the Longmenshan Fault zone. Fatalities approaching a total of 15,000 occurred, with a significant number resulting from four types of seismically triggered geohazards—rock avalanches and landslides, landslide-dammed lakes (“earthquake lakes”), and debris flows. China Geological Survey has identified 4,970 potentially risky sites, 1,701 landslides, 1,844 rock avalanches, 515 debris flows, and 1,093 unstable slopes. Rock avalanches and landslides caused many fatalities directly and disrupted the transportation system, extensively disrupting rescue efforts and thereby causing additional fatalities. Landslide-dammed lakes not only flooded human habitats in upstream areas but also posed threats to potentially inundated downstream areas with large populations. Debris flows become the most remarkable geohazards featured by increasing number, high frequency, and low triggering rainfall. Earthquake-triggered geohazards sequentially induced and transformed to additional hazards. For example, debris flows occurred on rock avalanches and landslides, followed by landslide-dammed lakes, and then by additional debris flows and breakouts of the landslide-dammed lakes and downstream flooding. Earthquake-induced geohazards occurred mainly along the fault zone and decreased sharply with distance from the fault. It can be anticipated that post-earthquake geohazards, particularly for debris flows, will continue for 5–10 years and even for as long as 20 years. An integrated strategy of continuing emergency response and economic reconstruction is required. The lesson from Wenchuan Earthquake is that the resulted geohazards may appear in large number in active fault regions. A plan for geohazard prevention in the earthquake-active mountainous areas is needed in advance.  相似文献   
1000.
陈文静  蔡奎  栾文楼  闫家栋  薛东青  田浩飞  邹承杰  赵亮  郭涵  宋炜  董鑫 《地质论评》2022,68(5):2022092002-2022092002
土壤是重要的自然资源之一,与人们的生活息息相关。笔者等基于任丘市1∶5万比例尺土地质量地球化学调查成果,依据相关标准和规范,对研究区土壤植物生长必需营养元素、重金属环境质量和土壤健康质量的元素进行了评价,为研究区生态环境保护、土地利用规划、特色农业开发、高标准农田建设等提供了科学依据。评价结果表明:① 土壤养分元素磷、钾、三氧化二铁处于丰富或中等状态,有机质、氮、铜、钼等元素处于较缺乏状态,有效态中有效锰、有效铁较缺乏;土壤总体处于碱性,偏碱性,元素有效态含量与其全量做相关分析得出具有一定的相关性,土壤pH从碱性到强碱性,Cu、Mn、Zn、K元素有效态与其全量的相关性减弱,B、P元素有效态与全量的相关性增强;②重金属元素单因子指数法评价,除一个样品Ni元素和两个样品Zn元素超过农用地土壤筛选值外,Cu、Pb、As、Cd、Cr、Hg元素均符合农用地土壤污染风险管控标准;研究区尼梅罗综合污染指数全部小于0. 7,说明全部达到了一级水平;研究区8种重金属元素全部符合无公害蔬菜产地的环境质量标准;除个别Cd元素和Pb元素样品不达标外,其他元素水平全部符合土壤《绿色食品产地环境质量标准》;③反映土壤健康质量的元素F和Se元素整体处于缺乏—较缺乏状态,I元素整体处于适中状态。  相似文献   
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