三种被动式积沙仪积沙效率的野外实验研究   总被引：1，自引：2，他引：1  

俎瑞平  屈建军  高前兆 《干旱区地理》2002,25(3):214-218

积沙仪积沙效率的高低直接影响近地表输沙率的测定，从而影响着风沙地貌的研究和风沙工程设计，对目前三种常用积沙仪在相同条件下（同一下垫面、相同风速）的积沙进行了野外观测。结果表明：（1）相同条件下，楔形积沙仪积沙量远远大于其它两种；（2）近地面积沙量随高度分布上，楔形积沙仪能更好地反映风沙流结构；（3）与其它两种积沙仪相比，楔形积沙仪所采集沙子中的小粒径颗粒含量明显多于其它两种积沙仪结果，而较大粒径颗粒的含量呈相反趋势，造成这些差异的原因在于楔形积沙仪采用的流线型构造和网状结构，从而对风沙流的阻挡程度较小，今后应推广楔形积沙仪的使用。  相似文献   

沙坡头人工植被固沙区天然降水的入渗和分配研究   总被引：5，自引：3，他引：5  

王新平  李新荣  张景光 《中国沙漠》2002,22(6):534-540

土壤、植被冠层与大气界面间(SVAT)物质传输过程日益成为水文学研究最感兴趣的领域,降水量的迁移与转换是非灌溉区SVAT主要的物质传输过程.干旱半干旱区稀疏灌丛蒸散量占降水量的90%以上,因此对降水入渗与水分在土壤内植物根际区再分配的研究显得十分重要.试验于2001年8月17日至9月30日在中国科学院沙坡头试验站进行,主要观测人工植被荒漠灌木柠条(Caragana korshinskii) 灌丛固定沙丘降水入渗与再分配过程.结果表明:在7次不连续降水过程中,土壤入渗深度与降水强度呈简单线性相关关系,土壤入渗速率约为降水强度的10倍.当次降水过程中降水强度小于0.46 mmh-1时,土壤入渗速率约为0 cm*h-1,此时的降水对沙区土壤基本上没有水分补给作用.受荒漠灌木柠条根系吸水作用的影响,其根系密集剖面深度40～140 cm内降水水分入渗积累不明显.降水入渗速率及入渗深度受土壤剖面初始含水率多寡而变化,干燥土壤剖面有助于提高瞬时入渗速率.降水以后随着时间的推移,人工固沙区微环境内空气温度、湿度等气象条件适宜,柠条生长进入相对旺盛阶段,其根系密集层140 cm深度处土壤含水率在总体上下降的过程中,表现出昼消夜长的趋势,试验期间翌日 8:00时土壤含水率值略高于前一日20:00时水分值 0.1%～0.3%.  相似文献   

腾格里沙漠人工固沙植被区生物土壤结皮对降水的拦截作用   总被引：33，自引：16，他引：33  

李守中  肖洪浪  宋耀选  李金贵  刘立超 《中国沙漠》2002,22(6):612-616

在沙坡头人工植被区对人工模拟降水及天然降水后生物土壤结皮层含水率进行了动态定位监测,并分析了生物土壤结皮拦截降水的作用.结果表明:①生物土壤结皮的发育改变了原来沙丘剖面的水分分配格局,10%～40%的年降水量被拦截到结皮层;②随固沙年限的增加,生物土壤结皮的进一步发育和演变,其对降水的拦截能力也进一步提高;③生物土壤结皮对降水的拦截有明显的季节变化,7～10月份平均拦截雨量比4～6月份平均高出12%.  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   

Erosion response to anthropogenic activity and climatic changes during the Holocene: case studies in northwestern China and southern Norway     

HE Xiubin  TANG Keli  John A Matthews  Geraint Owen 《地理学报》2002,12(4):467-471

Soil erosion assessment and prediction play critical roles in addressing problems associated with erosion control or soil conservation. The past dynamics of soil erosion can provide valuable information for us to understand the relations of soil erosion to environmental change and anthropogenic activity. The present paper has compared Holocene climatic changes in northwestern China with those in southern Norway, and investigated the past dynamics of erosion activity during the Holocene. Modern soil erosion on the Loess Plateau is a combination of the intensive natural erosion and human-induced erosion, the latter being four times greater than the former. Because of global warming and increasing human activities, climate on the Loess Plateau is becoming dryer and more unstable, causing an enhanced erosion problem and water scarcity. In the arctic-alpine region of southern Norway, however, the global warming and regional wetting caused expansion of the largest European ice cap. This has accentuated the erosion in that region, with a higher frequency of avalanches and debris flows.  相似文献   

晚更新世以来青海北部的人类活动与湖泊演变          下载免费PDF全文

周笃珺  马海州  P.J.Brantingham  谭红兵 《盐湖研究》2003,11(2):8-13

作为高海拔生态环境的青海北部是青藏高原的重要组成部分。晚更新世晚期以来 ,青海北部气候环境一直处于冷暖、干湿波动过程之中 ,湖泊水域也发生了相应的扩张和收缩 ,成为高原人类迁移和发展的自然背景。约 3 0kaB .P .,在晚期智人出现和迁徙的关键时期 ,青海北部开始有了最早的人类活动 ;更新世末—全新世初 ,气候转暖 ,古人类再次来到青海北部 ;进入全新世中期 ,气候暖湿 ,湖水位回升 ,细石器技术变得十分普通 ,青海北部的人类活动渐趋频繁。  相似文献   

Sand harm in Taklimakan Desert highway and sand control     

HAN Zhiwen  WANG Tao  SUN Qingwei  DONG Zhibao  WANG Xunming 《地理学报》2003,13(1):45-53

Reputed as a wonderful achievement of the world's highway construction history, the Taklimakan Desert highway is now facing serious sand drift encroachment problems due to its 447- km-long passage of sand sea consisting of crescent dunes, barchan chains, compound transverse dune ridges and complex megadunes. To solve some technical problems in the protection of the highway from sand drift encroachment, desert experts have been conducting the theoretical and applied studies on sand movement laws; causes, severities and time-space differentiation of sand drift damages; and control ways including mechanical, chemical and biological measures. In this paper the authors give an overall summary on the research contents and recent progress in the control of sand drift damages in China and hold that the theoretical research results and practices in the prevention of sand drift encroachment on the cross-desert highway represent a breakthrough and has an epoch-making significance. Since the construction of protective forest along the cross-desert highway requires large amount of ground water, what will be its environmental consequence and whether it can effectively halt sand drift encroachment on the highway forever are the questions to be studied urgently.  相似文献   

蒙甘新相邻(北山)地区金铜矿床时空分布特征及成矿作用   总被引：14，自引：1，他引：14       下载免费PDF全文

聂凤军  江思宏  白大明  刘妍  张义  赵月明  安存杰  王新亮  苏新旭 《矿床地质》2003,22(3):234-245

文章首次对蒙甘新相邻(北山)地区各类金、铜和铜—镍矿床(点)地质特征、成因类型和空间分布特点进行了系统总结，论证了金、铜和铜—镍成矿作用与古生代岩浆活动的关系，对区域地壳演化过程中金、铜和铜—镍成矿的动力学机制进行了深入讨论。研究结果表明，该区的金矿床(点)大体可划分为变质岩型、火山岩型、斑岩型和深成侵入岩型；铜矿床(点)有斑岩型、夕卡岩型和铜—镍硫化物型。金和铜矿床(点)大都沿古板块汇聚带分布，与海西期火成岩具密切的时空分布关系，它们是古板块对接碰撞期和碰撞期后大规模构造—岩浆活动的产物。  相似文献   

某地平板玻璃原料用石英砂的提纯研究     

彭光菊  黄永平  张石林  莫伟泉  黄松 《矿产与地质》2003,17(1):24-26

某地石英矿砂通过磁选分离法、稀酸浸泡法处理后，矿砂不同程度地降低了铁、铝、钙镁的含量；采用磁选分离 稀酸浸泡法联合处理后，使该地石英砂的化学成分达到了优质的生产平板玻璃用硅质原料的国家标准。  相似文献   

锦江水库坝址③号断裂构造破碎带地质特征及其对堤坝安全性的影响     

黄成炽  黄维旺  李志勤 《四川地质学报》2003,23(2):109-111

通过野外地质调查和地球化学探测成果，结合区域地质发展史，论述锦江水库③号断裂构造破碎带的地质特征及其对建筑物的影响。  相似文献