Total N,total P and organic matters content in floodplain soils of Xianghai Nature Reserve     

Deng Wei  Zhai Jin-liang  He Yan 《地理学报(英文版)》2002,12(1):58-64

Soil sediment samples of 10 layers with a spacing of 10 cm each were collected in different floodplain zones adjacent to Huolin River in the Xianghai Nature Reserve, and contents of total N, total P and organic matters were analyzed. The results showed that contents of total N, total P and organic matters were generally decreasing with the increase of distance from sample locations to the river channel, and contents of the three items were generally higher in the upper soil layer than that in the lower soil layer. The content variations displayed how flooding functions influenced nutrient matter content variations in floodplain soils since the flood inundation frequencies of the sample locations varied. The correlation analysis displayed that there were remarkable relativities between total N, total P and organic matters within definite spatial distance from the Huolin River channel.  相似文献   

Sedimentary cycles of trace elements in Salawusu River Valley since 150 ka BP   总被引：6，自引：0，他引：6  

Yao Chun-xial  Li Bao-sheng  Jin He-ling  David Dian Zhang  Yan Man-cun  Zhu Yi-zhi  Li Hou-xin  Zhang Yu-hong  Luo Kai-li 《地理学报(英文版)》2002,12(1):65-71

The paper makes some analyses on 11 trace elements in the Milanggouwan stratigraphical section in the Salawusu River valley, which is regarded as a prototype geology-palaeoclimate record since 150 ka BP. The results show that the content and variation of trace elements has experienced remarkably regular changes in the pace with coarse and fine sedimentary cycles of palaeo-aeolian sands to its overlying fluvio-lacustrine facies or/and palaeosols. The trace elements with chemical properties of relatively active (V, Sr, Cu, Ni, As) and relatively stable (P, Pb, Rb, Mn, Nb, Zr) are a manifestation of the corresponding 27 changeable cycles between peak and valley values, appearing a multi-fiuctuational process line of relative gathering and migration since then. The low numerical value distribution of these two types of trace elements in the aeolian sand facies represents erosion and accumulation under wind force during the cold-dry climate. Whereas their enrichments in both fluvio-lacustrine facies and palaeosols are related to the valley’s special low-lying physiognomic position between the Ordos Plateau and the Loess Plateau under the warm and humid climate conditions. The above relatively migrated and gathered change of the trace elements is the result of 27 climatic cycles of cold-dry and warm-humid, which is probably caused by repeated alternations of winter monsoon and summer monsoon in the Mu Us Sandy Land influenced by the climate vicissitudes in northern hemisphere during glacial and interglacial periods since 150 ka BP.  相似文献   

Statistical characteristics of chlorophyll-a concentration in Hong Kong′s coastal waters     

CHEN Xiaoling  Yok Sheung Li  LI Zhilin 《地理学报(英文版)》2002,12(3)

In this paper seven of the ten Water Control Zones (WCZs) in Hong Kong′s coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal variations of chlorophyll-a and its influencing factors. Cluster analysis was employed to group the monitoring stations based on the structure of the data set. Multiple step regression was employed to determine the significant influencing factors of chlorophyll-a level. The results suggest that all the monitoring stations could be grouped into two clusters. Cluster I with frequent red tide incidents comprises two WCZs which aresemi-enclosed bays. Cluster II with less red tide occurrence comprises the other five WCZs in an estuarine environment in the west. For both clusters, the organic contents indicator, BOD5, was a common significant influencing factor of the chlorophyll-a level. Nitrogen and light penetration condition related to turbidity, total volatile solids and suspended solids had more influence on the cholophyll-a level in Cluster I than in Cluster II, while phosphorus and oceanographic conditions associated with salinity, temperature, dissolved oxygen and pH were more important in Cluster II than in Cluster 1. Generally, there was a higher average chlorophyll-a level in winter and autumn in a year.The chlorophyll-a level was much higher in Cluster I than in Cluster II among all seasons. Although the chlorophyll-a concentration had great variations from place to place in Hong Kong′s coastal waters, it seemed to have a common long term fluctuation period of 8-10 years with a high-low-high variation in the period in the whole region, which might be influenced by other factors of global scale.  相似文献   

A finite‐element algorithm for electromagnetic induction in two‐dimensional anisotropic conductivity structures     

Yuguo Li 《Geophysical Journal International》2002,148(3):389-401

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On the spatial relationship between landslides and causative factors on Lantau Island, Hong Kong   总被引：8，自引：0，他引：8  

C. H. Zhou  C. F. Lee  J. Li  Z. W. Xu 《Geomorphology》2002,43(3-4)

This paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level. The approach is based on digital databases, and incorporates such methods as statistics, spatial pattern analysis, and interactive mapping. Firstly, the authors propose an object-oriented conceptual model for describing a landslide event, and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework. The statistical histogram, spatial overlay, and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors. A case study of an extreme event in 1993 on Lantau Island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on Lantau Island. A regional difference in the relationship between landslides and topography is identified. Most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25–35°, while in the eastern part, the corresponding range is 30–35°. Overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub-covered area, and in the transition zones between different vegetation types. The proposed approach can be used not only to analyze the general characteristics of such a relationship, but also to depict its spatial distribution and variation, thereby providing a sound basis for regional landslide prediction.  相似文献   

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   

Rescaled-range and power spectrum analyses on well-logging data   总被引：6，自引：0，他引：6  

Chun-Feng Li 《Geophysical Journal International》2003,153(1):201-212

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Partial melt or aqueous fluid in the mid-crust of Southern Tibet? Constraints from INDEPTH magnetotelluric data   总被引：13，自引：0，他引：13  

Shenghui Li  Martyn J. Unsworth  John R. Booker  Wenbo Wei  Handong Tan  Alan G. Jones 《Geophysical Journal International》2003,153(2):289-304

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天山1号冰川厚度和冰下地形探测与冰储量分析   总被引：12，自引：0，他引：12       下载免费PDF全文

孙波  何茂兵  张鹏  焦克勤  温家洪  李院生 《极地研究》2003,14(1):35-44

通过对天山乌鲁木齐河源 1号冰川的雷达回波探测 ,清晰地揭示出冰川底部冰 /岩界面的位置及其起伏变化特征 ,显示出雷达波对山地冰川良好的穿透能力和对冰下地形的高分辨能力 ,冰川雷达测厚的误差小于 1 .2 %。研究结果显示 ,1号冰川东支冰川平均厚度为 5 8.77m ,西支冰川平均厚度为 44.84m ,冰体厚度最大值发育于冰川中部趋于主流线位置。冰川冰储量计算表明 ,东支冰储量为 0 .0 5 1 868km3,西支冰储量为 0 .0 2 0 2 1 0km3。表面和底部地形有明显差异 ,主要因冰川动力过程对基岩强烈的地貌作用所致 ,意味着冰床的起伏地形对冰川浅层冰体的运动过程影响不显著。  相似文献   

星载微波散射计技术及其在极地的应用   总被引：1，自引：0，他引：1       下载免费PDF全文

程晓  鄂栋臣  邵芸  李震 《极地研究》2003,15(2):151-159

简要介绍了微波散射计的原理、星载微波散射计的发展状况及用于提高散射计图像空间分辨率的图像滤波重建算法。在此基础上结合几种星载微波散射计数据简要介绍了微波散射计在南北两极的应用情况 (海冰图测绘、海冰运动监测、海冰分类、极地冰盖研究等 )及其未来研究展望。  相似文献