南极菲尔德斯半岛古海蚀龛沉积的古环境记录   总被引：3，自引：2，他引：3       下载免费PDF全文

孙立广  刘晓东  谢周清  赵俊琳 《极地研究》2002,14(3):163-173

在西南极菲尔德斯半岛长城站地区发现有大量古海蚀龛 ,龛内保存有完整沉积剖面 ,通过对其中一个沉积剖面的粒度特征及元素组成的分析 ,确认该剖面是后期的湖相沉积 ,并据此恢复了距今 460 0年以来该地区古环境演化历史。结果表明 ,距今 40 0 0— 30 0 0年长城站区地表岩石化学风化作用较强烈 ,处于一个相对温暖的时期 ,这与湖泊沉积物、海洋沉积物等古环境记录载体的研究结果是一致的 ,证明古海蚀龛沉积可以作为研究南极无冰区和冰缘地区古环境演化历史的一种新的地质载体。  相似文献   

格罗夫山:我国新发现的一个陨石富集区   总被引：6，自引：3，他引：6       下载免费PDF全文

刘小汉  琚宜太 《极地研究》2002,14(4):243-247

中国南极考察队在1998—2000年两次对南极洲格罗夫山地区进来了考察,共回收32块陨石,根据陨石的分布位置和岩石化学类型的差异性,初步确定格罗夫山是我国新发现的一个陨石富集区,但是该区的陨石富集模式还有待于进一步研究。  相似文献   

Groundwater regime and calculation of yield response in North China Plain: a case study of Luancheng County in Hebei Province     

Jia Jin-sheng  Yu Jing-jie  Liu Chang-ming 《地理学报(英文版)》2002,12(2):217-225

The groundwater table has been declining at a rate of 0.65 m/yr in Luancheng County since large scale groundwater extraction carried out in the 1960s. The drop of precipitation, substantial increase in agricultural output, variations of crop planting structure and construction of water conservancy projects in the headwater area all tie up with the decline of the groundwater table. On the basis of analyzing the hydrogeological conditions and the water resources utilization of Luancheng County, a three-dimensional groundwater flow model was developed to simulate the county’s groundwater flow through finite-difference method using Visual Modflow software. We divide the research field into four parts after analyzing the hydrogeological condition. Based on parameter calibration and adjustment using measured data, the hydraulic conductivity and specific yield were simulated. Using the calibrated model, we analyze the agricultural water saving potentiality and its influence on the groundwater. The results are as follows: (1) if we decrease the amount of water extracted by 0.14xl0⁸ m³, the average groundwater table of the five observation wells in December will rise by 0.33 m; (2) if we decrease the water by 0.29x 10⁸m³, the average groundwater table of the five observation wells in December will rise by 0.64 m; and (3) if we increase the water by 0.29 x 10⁸m³, the average groundwater table of the five observation wells in December will decline by 0.45 m. So we can draw a conclusion that controlling the agricultural water use is an important way to prevent the decline of groundwater table.  相似文献   

Research progress of socio-economic water cycle in China   总被引：3，自引：0，他引：3  

Jia Shao-feng  Wang Guo  Zhang Shi-feng  Yu Gui-rui  Wang Jin-xia  Xia Jun 《地理学报(英文版)》2002,12(1):114-120

China has made great progress in the study of socio-economic water cycle. She has completed national water resources appraisement and medium to long-term water supply planning. She has been engaging in study on water-deficient regions in North China and Northwest China for about half a century. For solving water shortage problem in northern China, she has put forward the famous South-to-North Water Transferring Projects, which has been set as one of the four biggest national projects in the Tenth Five-Year-Plan period although there are still debates. For promoting water use efficiency, China has been reforming her water management system, including water right system and water price system. There has already been a case of water right purchase. China has also done a lot of research on the interaction between human activity, water and ecosystem. For meeting the need of sustainability and coordinating water resources development and environmental protection, the study of ecological water requirement became very hot in recent years. There are three focuses of socio-economic water cycle study now in China: water transfer projects from the south to the north, water resources management and ecological water requirement.  相似文献   

A general model for estimating actual evaporation from non-saturated surfaces     

Qiu Xinfa Ph.D  Zeng Yan  Liu Changming 《地理学报(英文版)》2002,12(4):479-484

Based on energy balance equation and mass transfer equation, a general model to estimate actual evaporation from non-saturated surfaces was derived. Making use of two concepts, “relative evaporation” and “relative drying power”, a relationship was established to account for the departure from saturated conditions. Using this model, the actual evaporation (evapotranspiration) can be calculated without the need of potential evaporation estimation. Furthermore, the model requires only a few meteorological parameters that are readily and routinely obtainable at standard weather stations. Based on nearly 30 years data of 432 meteorological stations and 512 hydrological stations in China, in combined with GIS, nine typical river basins were selected. Using the data of the selected river basins, the model was tested. The results show that the actual evaporation rate can be estimated with an error of less than 10% in most areas of China, except few years in the Yellow River Basin.  相似文献   

Are hydrous phases more compressible? Implications for high-velocity zones in the deep mantle     

Lin-gun Liu 《Geophysical Journal International》2002,149(1):37-43

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Velocity profile of a sand cloud blowing over a gravel surface   总被引：2，自引：0，他引：2  

Zhibao Dong  Hongtao Wang  Xiaoping Liu  Fang Li  Aiguo Zhao 《Geomorphology》2002,45(3-4)

Particle dynamic analyzer (PDA) measurement technology was used to study the turbulent characteristics and the variation with height of the mean horizontal (in the downwind direction) and vertical (in the upward direction) particle velocity of a sand cloud blowing over a gravel surface. The results show that the mean horizontal particle velocity of the cloud increases with height, while the mean vertical velocity decreases with height. The variation of the mean horizontal velocity with height is, to some extent, similar to the wind profile that increases logarithmically with height in the turbulent boundary layer. The variation of the mean vertical velocity with height is much more complex than that of the mean horizontal velocity. The increase of the resultant mean velocity with height can be expressed by a modified power function. Particle turbulence in the downwind direction decreases with height, while that in the vertical direction is complex. For fine sands (0.2–0.3 mm and 0.3–0.4 mm), there is a tendency for the particle turbulence to increase with height. In the very near-surface layer (<4 mm), the movement of blown sand particles is very complex due to the rebound of particles on the bed and the interparticle collisions in the air. Wind starts to accelerate particle movement about 4 mm from the surface. The initial rebound on the bed and the interparticle collisions in the air have a profound effect on particle movement below that height, where particle concentration is very high and wind velocity is very low.  相似文献   

Statistical properties of reflection traveltimes in 3-D randomly inhomogeneous and anisomeric media   总被引：1，自引：0，他引：1  

Yu. A. Kravtsov  T. M. Müller  S. A. Shapiro  S. Buske 《Geophysical Journal International》2003,154(3):841-851

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南极无冰区典型沉积环境石英砂表面结构特征及其在沉积环境识别中的应用   总被引：5，自引：0，他引：5       下载免费PDF全文

尹雪斌  孙立广  刘晓东 《极地研究》2003,14(1):1-11

本文利用电镜扫描方法 (SEM)对比分析了南极乔治王岛无冰区海滩沉积、冰碛物以及阿德雷岛湖泊沉积等典型沉积环境中的石英砂表面结构特征 ,得出了乔治王岛各典型沉积环境中石英砂表面结构特征的颗粒频率曲线。结果表明 :不同沉积环境下的石英砂颗粒表面结构特征具有相似性 ,这主要和南极地区广泛发育的冰川作用有关 ,同时 ,它们也有各自典型的特征组合 ,这些典型特征组合的不同反映了石英砂后期的搬运历史和沉积环境的差异。本文还依据石英砂表面特征的颗粒出现频率 ,利用聚类分析方法对研究区内三级海岸阶地上的沉积物和一个未知成因的样品进行了沉积环境的判别分析 ,结果证明石英砂微形貌特征可以作为南极地区沉积环境识别的有效手段  相似文献   

北极海冰细菌产胞外酶及主要环境因子的初步研究   总被引：1，自引：3，他引：1       下载免费PDF全文

曾胤新  俞勇  涂雪梅  陈波  何剑锋 《极地研究》2003,15(4):303-309

覆盖在北极海洋上的广阔海冰为其内部生存的微生物群落提供了一个独特的生境。研究表明 ,大量海冰细菌能够分泌产生胞外酶 ,其中产蛋白或脂质水解酶细菌的比例远高于产多糖水解酶的细菌。温度、盐度是直接影响海冰细菌生存与活力的 2个主要环境因子。 76%的产酪蛋白酶海冰细菌为低温菌 ,菌株只能在 <35°C条件下生长 ;而 98%的酪蛋白酶最适作用温度≥ 35°C ,其中 62 %的酶最适作用温度≥ 45°C。几乎所有的产酪蛋白酶海冰细菌都耐盐或嗜盐  相似文献