Importance of soil surface characteristics on water erosion in a small grazed Sahelian catchment     

H. Karambiri  O. Ribolzi  J. P. Delhoume  J. Ducloux  A. Coudrain‐Ribstein  A. Casenave 《水文研究》2003,17(8):1495-1507

This study concerns the problem of water erosion in the Sahel. Surface water and sediment yields (suspended matter and bedload) were monitored for 3 years (1998–2000) at the outlet of a small grazed catchment (1·4 ha) in the northern part of Burkina Faso. The catchment consists of about 64% sandy deposits (DRY soil surface type), which support most of the vegetation, and about 34% of crusted bare soils (ERO soil surface type). The annual solid‐matter export is more than 90% suspended sediment, varying between 4·0 and 8·4 t ha^?1. The bedload represents less than 10% of soil losses. In a single flood event (10 year return period), the sediment yield can reach 4·2 t ha^?1. During the period studied, a small proportion (20 to 32%) of the floods was thus responsible for a large proportion (80%) of the solid transport. Seasonal variation of the suspended‐matter content was also observed: high mean values (9 g l^?1) in June, decreasing in July and stabilizing in August (between 2 and 4 g l^?1). This behaviour may be a consequence of a reorganization of the soil surfaces that have been destroyed by trampling animals during the previous long dry season, vegetation growth (increase in the protecting effect of the herbaceous cover) and, to a lesser extent, particle‐supply limitation (exhaustion of dust deposits during July). The particle‐size distribution in the suspended matter collected at the catchment outlet is 60% made up of clay: fraction ≤2 µ m. The contribution of this clay is maximum when the water rises and its kaolinite/quartz ratio is then close to that of the ERO‐type surfaces. This indicates that these surfaces are the main source of clay within the catchment. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

射电天球参考架指向维持方法讨论     

李金岭  金文敬  李金增 《天文研究与技术》1994,(4)

依据河外射电源天球参考架的现状与建立射电天球参考架的最终目的，本文提出了以共同基本源维持参考架指向的观点。对实际资料的归算结果表明，在确保参考架指向长期稳定性方面，共同基本源指向维持模型优于ＩＥＲＳ维持模型。依据验算结果，文中同时讨论了选源标准与参考架指向稳定性的关系，指出基本源一次性变更的比例不能过高。一方面应完善选源标准；另一方面，一旦此标准发生性？上的改变时，应对在旧标准下选出的基本源进行复核，并作相应的指向调整，否则将可能造成参考架指向的跳变。  相似文献   

Hard X-ray spectrum of Mkn 421 during the active phase     

R. K. Manchanda 《Journal of Astrophysics and Astronomy》2001,22(2-3):145-154

Spectral measurement of Mkn 421 were made in the hard X-ray energy band of 20–200 keV using a high sensitivity, large area scintillation counter telescope on November 21, 2000 and these coincided with the onset of an active X-ray phase as seen in the ASM counting rates on board RXTE. The observed spectrum can not be fitted to a single power law similar to the PDS data of BeppoSAX. The data can be fitted both by a two component power-law function or a combination of an exponential function with a power law component at the high energies above 80 keV. We identify these components with those arising from the synchrotron self compton and the high energy power-law tail arising from the upgrading of the thermal photons due to multiple Compton scattering a la Cyg X-1. A comparison with the earlier data clearly suggests a spectral variability in the hard X-ray spectrum of the source. We propose a continuously flaring geometry for the source as the underlying mechanism for energy release.  相似文献   

A study on quality of aquatic environment in Tumen River Area     

Zhu Yanming  Li Jinsong  Lu Xueqiang 《中国地理科学(英文版)》1997,8(2):126-135

After the survey of pollution sources, a study on surface water quality assessment and forecast is given by means of grey system method, fuzzy mathematical method and multiple-index method. Based on it, aquatic environment quality features, treatment measures and environmental strategies of the area are proposed. The quality of aquatic environment of 5 rivers in the Tumen River area is studied. The results show that the pollution of surface water is serious; water quality of most rivers is between grade IV and V except the Hunchun River, being higher than grade IV standard; pollution levels of most rivers have been basically controlled except the of Burhatong River, which is deteriorating gradually. Pollutants of the rivers are comparatively regular, mainly are SS, COD, BOD, AR-OH, NH₃-N. The main pollution trades are chemical fibre industry, pulp and paper making industry and mining industry. If the growth rate of gross industrial product is higher than 25 percent under the encouraging-model of regional exploitation, the pollutants’ load will overtake the bearing capacity of aquatic environment. Thus some protection program against pollution must be worked out in order to achieve the harmonious development of economy society and environment. A project from “Studies on Earlier Stage of Regional Development” of the Chinese Academy of Sciences  相似文献   

乌鲁木齐河流域地下水水质监测网设计   总被引：1，自引：0，他引：1  

朱瑾  霍传英  李和生  弓小平  王俊桃  李文鹏  周仰效 《水文地质工程地质》2008,35(1):12-18

文章运用地下水易污性编图及污染源分布图法进行了乌鲁木齐河流域地下水水质监测网设计。共设计了130监测孔,现有46个监测孔,另需要84个新的监测孔。按监测类型分为面源监测点22个,点源监测点87个,重点水源地与泉水监测点21个。按监测运行分长期监测点55个,流域普查监测点75个。普查监测点监测频率为1次/5年,长期监测点监测频率为1次/年。首期有针对性地在污染严重的柴窝堡新化厂排污区、乌鲁木齐河谷老排污区、米泉污灌区、米泉工业污染区、老龙河污染区取了25个污染水样测试分析,结果显示地下水已经受到严重污染。  相似文献   

近百年来长江口启东嘴潮滩沉积物质来源及定量估算   总被引：2，自引：0，他引：2  

张云峰  张振克  任航  高磊  丁海燕 《地理学报》2018,73(11):2105-2116

河流入海输沙是海岸稳定的重要物质基础。启东嘴潮滩位于长江北支口门,与江苏海岸线交汇,陆海相互作用强烈。利用电感耦合等离子体质谱仪测定了岩芯沉积物QDZ-1的地球化学元素。根据地球化学元素的分布特征和富集系数,分析了物源指示意义,表明启东嘴潮滩沉积物受到长江物质和南黄海物质的共同影响。基于地球化学元素的沉积物端元定量判识方法,对不同物质来源的贡献率进行了定量估算。在1930年前启东嘴潮滩沉积物主要来自长江的入海输沙,贡献率为68.1%,随着长江北支河槽的衰退,贡献率逐渐减少,在1930-1972年间为38.5%,到1972年后减少到17.5%。苏北沿岸流携带向南输运的南黄海物质,贡献率逐渐增加,在1930年前为27.1%,在1930-1972年间为55.6%,到1972年后增加到75.9%,成为启东嘴潮滩主要物质来源。沉积物来源的阶段性变化,在时间上与北支水动力的阶段性变化基本吻合。  相似文献   

区域碳排放转移的演变特征与结构分解及减排对策分析——以河南省为例   总被引：2，自引：1，他引：1  

钟章奇  吴乐英  陈志建  何凌云 《地理科学》2017,37(5):773-782

通过耦合投入产出分析方法和结构分解模型,探讨2002~2010年区域碳排放转移的演变特征、驱动因素及其地理源特征。研究发现：2002~2010年流出和流入河南省的贸易隐含碳排放均处于不断增加的趋势,其中流出贸易隐含碳排放主要是受外部最终需求的影响,且主要集中在中国的中部和东南部地区,而流入贸易隐含碳排放则主要是受本地最终需求和本地最终产品结构的影响最为显著,且主要来源于中国的东部、东北部和中部地区。研究还发现,为减轻贸易对区域碳排放及其减排责任的影响,开展区域合作来共同减排比单个地区独自应对更为有利,但在区域合作中各地区的获益程度可能会有所差别。  相似文献   

造山带异源浆混花岗岩理论与方法研究   总被引：2，自引：0，他引：2  

窦全成  董琳  曹德云  刘永成  任鹏奎 《矿产与地质》2008,22(3):189-195

1：5万花岗岩填图方法在区调工作中推广以来,在造山带花岗岩调查实践中,由于造山作用及过程的复杂性,花岗岩浆的多源及多样性,使同源岩浆演化理论及方法遇到了难题。文章在新一轮1：25万造山带试点图幅,在对同源岩浆演化理论及方法的适用性进行探索的同时,提出了异源浆混理论指导造山带内部浆混花岗岩（H型花岗岩）的填图方法。并就异源浆混花岗岩鉴别标志等作了系统总结,提出了浆混组合、浆混单元、浆混体,填图的理论方法体系;给予了浆混花岗岩明确的定义。  相似文献   

粤东成矿地质背景及银-铜-铅-锌成矿物质来源探讨     

郭锐  曾国光 《矿产与地质》2008,22(3):236-240

通过对粤东地区地层和岩石中成矿元素含量和区域地质背景的分析,认为粤东地区铜铅-锌-银成矿作用与燕山期的构造-岩浆作用关系密切,成矿物质中银-铜-锌以下地壳来源为主,铅则以上地壳及沉积地层来源为主。  相似文献   

日照市海岸带海滩沉积物粒度特征及物源分析          下载免费PDF全文

张昊  郝义  王惠  李忠涵 《山东国土资源》2020,36(3):50-58

根据日照市海岸带2个重点海滩所采集的样品,通过粒度、磁化率、主微量及稀土元素等方面的调查资料,综合分析了研究区沉积物类型、分布特征、搬运路径及物质来源。结果表明,研究区沉积物类型以砂为主,在平行海岸方向上,沉积物粒径自北至南由细变粗。在垂直海岸方向上,从滩肩到滩面再到低潮线处,沉积物粒径逐渐变细。海滨国家森林公园海滩的分选性要好于万平口海水浴场海滩。沉积物受黄海沿岸流影响,多自北向南运移。海滩中浅部物质的来源与陆内一侧基岩中斜长片麻岩和二长花岗岩的关系较为密切,深部物质的来源与靠海一侧基岩中花岗斑岩和花岗闪长岩的关系较为密切。  相似文献