SEDIMENT MOBILIZATION BY SURFACE EROSION IN MIDDLE MOUNTAIN CATCHMENTS OF NEPAL     

Juerg MERZ Gopal NAKARMI Pradeep M. DANGOL Madhav P. DHAKAL Bhawani S. DONGOL Rolf WEINGARTNER 《国际泥沙研究》2006,21(3):180-199

1 INTRODUCTION Soil erosion in the foothills of the Hindu Kush-Himalayas (HKH) is considered to be a hot topic in land degradation research in the region (Scherr and Yadav, 1996). The land degradation research has mainly addressed the issue of topsoil los…  相似文献   

利用对数正态分布图解析徐州城市土壤中重金属元素来源和确定地球化学背景值   总被引：9，自引：0，他引：9  

王学松  秦勇 《地球化学》2007,36(1):98-102

城市土壤指示了城市环境中重金属污染的状况.为了更好地评价人为因素对城市土壤的影响强度,确定城市土壤重金属元素的地球化学背景值是十分必要的.以徐州城市表层土壤中Pb、Cu、Zn、V、Se和Ti等重金属为例,利用对数正态分布图区分了不同元素的来源,其中Ti和V主要来自土壤母质的分化,而Pb、Cu、Zn和Se等的来源则比较复杂,表现为受人为因素作用强烈.这些结果与利用多元统计方法(如聚类分析和主成分分析)获得的结果一致.利用对数正态分布图获得了Pb、Cu、Zn、V、Se和Ti等元素的地球化学背景值.  相似文献   

Rock-magnetic properties of Neogene sediments, northern flank of Tianshan Mountains     

Li ChuanXin  Guo ZhaoJie  Meng ZiFang  Li HaiYan  Zhang ZhiCheng  Wu ChaoDong 《中国科学D辑(英文版)》2007,50(4):544-554

Analyses of rock-magnetic properties of Neogene sediments of the Taxihe section, northern Tianshan Mountains, show that the section can be classified into three categories including lacustrine facies, fluvial facies and alluvial facies, which correspond to the lower, middle and upper of the Taxihe section respectively. The magnetic minerals of the lacustrine facies may be affected by the process of weath- ering, lithogenesis and biolithogenesis besides the source of the sediments. The natural remanence intensities are between 10-3 A/m and 10-2 A/m. The minerals are dominated by magnetite and the high coercive magnetic mineral may be goethite. The magnetic grains are the mixture of PSD SD or SD SP. The natural remanence intensities of the strata of fluvial facies are between 10-2 A/m and 10-1 A/m, about ten times that of the lacustrine facies. The magnetic minerals are mainly magnetite and hematite, and the magnetic grains are mainly PSD. The characteristic remanence (ChRM) carriers are magnetites. In the alluvial facies, the natural remanence intensities are mostly less than 1×10-2 A/m. The magnetic minerals of the series are dominated by magnetite and hematite, almost the same as the fluvial facies. But the difference is that most of the stepwise demagnetization can reveal two components and the ChRM carriers are hematites. The magnetic grains are PSD in terms of the hysteresis parameters.  相似文献   

Constraining the propagation of bomb-radiocarbon through the dissolved organic carbon (DOC) pool in the northeast Pacific Ocean     

Steven R. Beaupr  Ellen R.M. Druffel 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1717-1726

This study extends the 1991-1995 records of marine dissolved organic carbon (DOC) concentrations and Δ¹⁴C values at hydrographic Station M (34°50′N, 123°00′W) with new measurements from a frozen (-20 °C) archive of samples collected between April 1998 and October 2004. The magnitudes and synchronicity of major Δ¹⁴C anomalies throughout the time-series imply transport of DOC from the surface ocean to depths of at least 450 m on the timescale of months. Keeling plots of all measurements at Station M predict a continuum of possible background DOC compositions containing at least 21 μM of -1000‰ (i.e., ≥57,000 ¹⁴C years) DOC, but are more consistent with mean deep DOC (38 μM, -549‰; i.e., 6,400 ¹⁴C years). These results and coral records of surface dissolved inorganic carbon (DIC) Δ¹⁴C were used to estimate pre-bomb DOC Δ¹⁴C depth profiles. The combined results indicate that bomb-¹⁴C has penetrated the DOC pool to depths of ≥450 m, though the signal at that depth is obscured by short-term variability.  相似文献   

不同石漠化等级的孢粉组合特征及其生态指示意义——以花江实验区为例   总被引：1，自引：1，他引：0  

赵增友  袁道先  罗伦德  石胜强  郝秀东 《中国岩溶》2010,29(2):113-119

以贵州省关岭县南部北盘江试验示范为例,分析了不同等级石漠化土地上的表土孢粉组合特征,揭示了孢粉组合特征与石漠化等级的相互关系。结果显示:石漠化地区的孢粉组合具有鲜明的特征,乔木与灌木合占16.1%,草本与蕨类植物合占58.9%,这反映了石漠化地区以草蕨类植物为主的植被状况;孢粉组合与石漠化等级呈良好的相关性,草蕨类植物随石漠化等级的升高比重由41%增加到77.6%,种类由14种增加到27种,乔木花粉所占比重由6.9%降到2.6%,植物种类不变;孢粉组合反映出三出凤尾蕨等蕨类植物对岩溶石漠化生态环境的适应性和代表性。  相似文献   

应用岩石热解数据S2-TOC相关图进行烃源岩评价   总被引：1，自引：0，他引：1  

曾花森  霍秋立  张晓畅  鄢仁勤  姜淑杰 《地球化学》2010,39(6):574-579

应用岩石热解数据评价烃源岩的传统方法具有一定的局限性。由于矿物基质的吸附或“死碳”的影响,有机质类型的“范氏图解”往往夸大烃源岩有机质类型的非均质性。对松辽盆地上白垩统不同有机质丰度和有机质类型的烃源岩生烃动力学研究表明,它们具有相似的生烃动力学特征,说明尽管有机质丰度存在较强的非均质性,但其有效源岩类型（区别于应用范氏图划分的有机质类型）是一致的。这些烃源岩的岩石裂解烃（S2）与有机质丰度（TOC）的相关系数很高,与生烃动力学的分析结果一致,表明应用S2-TOC相关图划分烃源岩的有机质类型可以更真实地反映烃源岩的有效源岩类型,S2-TOC相关图是评价烃源岩有效源岩类型的有效手段。过去岩石热解数据用于反映烃源岩成熟度的主要指标是tmax,tmax对于偏Ⅱ／Ⅲ型的烃源岩比较适用,而对于Ⅰ型烃源岩,由于生油窗内变化不明显,tmax不能完全反映有机质的成熟过程;而且tmax也受运移油等其他因素影响。不同成熟度的烃源岩的S2-TOC图分析结果显示,随着成熟度的增加,S2-TOC的回归斜率和TOC逐渐减小;利用不同成熟度的烃源岩建立的S2-TOC图可用于评价烃源岩的成熟度。松辽盆地不同沉积相中烃源岩的S2-TOC相关图的特征表明。只要有有利的有机质保存条件,各沉积相下均可发育优质的烃源岩;S2-TOC相关图可以反映烃源岩形成的沉积环境和有机质保存条件。  相似文献   

Assessing the impact of the hydraulic properties of a crusted soil on overland flow modelling at the field scale     

Nane Chahinian  Marc Voltz  Roger Moussa  Gwenn Trotoux 《水文研究》2006,20(8):1701-1722

Soil surface crusts are widely reported to favour Hortonian runoff, but are not explicitly represented in most rainfall‐runoff models. The aim of this paper is to assess the impact of soil surface crusts on infiltration and runoff modelling at two spatial scales, i.e. the local scale and the plot scale. At the local scale, two separate single ring infiltration experiments are undertaken. The first is performed on the undisturbed soil, whereas the second is done after removal of the soil surface crust. The HYDRUS 2D two‐dimensional vertical infiltration model is then used in an inverse modelling approach, first to estimate the soil hydraulic properties of the crust and the subsoil, and then the effective hydraulic properties of the soil represented as a single uniform layer. The results show that the crust hydraulic conductivity is 10 times lower than that of the subsoil, thus illustrating the limiting role the crust has on infiltration. Moving up to the plot scale, a rainfall‐runoff model coupling the Richards equation to a transfer function is used to simulate Hortonian overland flow hydrographs. The previously calculated hydraulic properties are used, and a comparison is undertaken between a single‐layer and a double‐layer representation of the crusted soil. The results of the rainfall‐runoff model show that the soil hydraulic properties calculated at the local scale give acceptable results when used to model runoff at the plot scale directly, without any numerical calibration. Also, at the plot scale, no clear improvement of the results can be seen when using a double‐layer representation of the soil in comparison with a single homogeneous layer. This is due to the hydrological characteristics of Hortonian runoff, which is triggered by a rainfall intensity exceeding the saturated hydraulic conductivity of the soil surface. Consequently, the rainfall‐runoff model is more sensitive to rainfall than to the subsoil's hydrodynamic properties. Therefore, the use of a double‐layer soil model to represent runoff on a crusted soil does not seem necessary, as the increase of precision in the soil discretization is not justified by a better performance of the model. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

近40年内蒙古候降水变化趋势   总被引：1，自引：0，他引：1       下载免费PDF全文

裴浩  郝璐  韩经纬 《应用气象学报》2012,23(5):543-550

基于1964—2003年内蒙古44个站日降水量数据,进行了前20年 (1964—1983年)、后20年 (1984—2003年) 候降水变化的聚类分析,得到了最佳聚类数和各聚类的台站组成及其空间分布情况,对前20年和后20年候降水中值的变化情况、候最大降水量出现时间、各聚类的整体特征等进行了分析,并进行了候 (5 d) 和11 d降水中值极图的对比。结果表明:内蒙古不同地区的候降水变化格局存在经向地带性,但站点海拔的差异使这种地带性有所模糊;前、后两个20年候降水的变化格局较为复杂,大多数站点在一些候降水有显著变化,既有降水显著增加的候,也有降水显著减少的候;候最大降水出现的时间和量值有一定变化。  相似文献   

集合预报产品在台风麦莎预报中的应用   总被引：3，自引：1，他引：2  

刘家峻  张立凤  关吉平  李荔珊  费增坪 《气象》2010,36(5):21-31

为了提高集合预报效果,利用T106L19全球谱模式和增长模繁殖法对台风麦莎制作了13个成员的集合预报,并对其结果进行集合预报产品解释应用研究。首先在离散距离分簇法中,引入方差分析的方法确定分簇基础,然后对集合预报的形势场进行了分簇,相对于以往采用96小时样本为分簇基础进行分簇的方法,分簇效果提高明显,分簇结果能给出台风移动的几种可能路径及其概率;其次对要素随时间的演变利用系统聚类法进行了分类,根据分簇平均图可以确定几个可能的台风登陆地点,制作了这些特殊点要素分类烟羽图,通过分析要素随时间的演变特征,提高对台风登陆地点和时间的预报精度;最后制作了盒须图,通过盒须图中数据组主体以外的数据点,确认出值得注意的一些特殊集合成员的预报结果,减少了小概率事件的漏报率。研究结果表明,将方差分析引入离散距离分簇法,要素烟羽聚类法以及盒须图的应用有利于提高和改善集合预报效果,集合预报产品解释应用效果得到改进。  相似文献   

A test method for analyzing the deformation of landslide model     

《地震研究进展（英文）》2021,1(3):100031

In order to study the overall deformation of geotechnical model conveniently, the worksite of landslide bridge foundation reinforced by the front and rear row anti-slide piles in Chenglan railway was taken as an example. On the basis of shaking tabe test of a 1/40 reduced scale model, the landslide deformation caused by vibration waves was monitored through burying self-made phosphor bronze strips in soil. Combined with the horizontal and vertical coordinates of the bending strain points on the phosphor bronze strips, the digital matrix was converted by applying Renka Cline random matrix generation method, and the two-dimensional contour plots were drawn based on it. The results showed that the two-dimensional contour plots reflected the basic law of landslide deformation reasonably, and it revealed the evolution process of landslide deformation and failure. The research conclusions were consistent with the test phenomenon, which met the basic requirements of overall deformation analysis of landslide model. This proposed method can monitor multiple cross sections and was practical for model test.  相似文献