北盘江流域水土流失及石漠化调控   总被引：4，自引：2，他引：2  

秦中  张捷  王腊春 《中国岩溶》2005,24(1):51-55

以1989- 2001年通过盘江桥、高车断面的输沙量资料,分析北盘江流域的水土流失状况。结果表明,喀斯特地区的水土流失特征具有非线性的复杂关系。为了改善北盘江流域的生态环境质量,有必要对石漠化过程和人类活动方式采取适当的调控措施。通过对不同尺度范围可行性的探讨,认为按尺度层次划分的坡地改良方式,可能是北盘江喀斯特地区石漠化治理较为有效的途径。   相似文献   

石油类污染物在包气带土层中的水化学迁移率测定     

李绪谦  商书波  林亚菊  周洪义  侯戈 《吉林大学学报(地球科学版)》2005,35(4):501-504,519

水化学迁移率是反映污染质在水-土孔隙介质中迁移锋面速度的参数,参数值的大小与土壤介质性质、水流状态、污染物质的物理化学性质有关。利用淋滤土柱的动态平衡试验法,模拟自然降雨入渗条件下,石油类污染物在吉林油田区包气带土层中的迁移转化过程。试验结果表明,其水化学迁移过程可分为淋溶阶段、吸附阶段和平衡阶段;微生物分解作用比较弱;不同厚度土层的淋滤液浓度衰减曲线趋势极为相似。考虑室内实验与野外自然环境之间存在的尺度效应,合理确定了阻滞因子、水化学迁移率。  相似文献   

From precipitation to runoff: stable isotopic fractionation effect of glacier melting on a catchment scale          下载免费PDF全文

Shiqiao Zhou  Zheng Wang  Daniel R. Joswiak 《水文研究》2014,28(8):3341-3349

Stable isotope variability and fractionation associated with transformation of precipitation/accumulation to firn to glacial river water is critical in a variety of climatic, hydrological and paleoenvironmental studies. This paper documents the modification of stable isotopes in water from precipitation to glacier runoff in an alpine catchment located in the central Tibetan Plateau. Isotopic changes are observed by sampling firnpack profiles, glacier surface snow/ice, meltwater on the glacier surface and catchment river water at different times during a melt season. Results show the isotopic fractionation effects associated with glacier melt processes. The slope of the δD‐δ¹⁸O regression line and the deuterium excess values decreased from the initial precipitation to the melt‐impacted firnpack (slope from 9.3 to 8.5 and average d‐excess from 13.4‰ to 7.4‰). The slope of the δD‐δ¹⁸O line further decreased to 7.6 for the glacier runoff water. The glacier surface snow/ice from different locations, which produces the main runoff, had the same δD‐δ¹⁸O line slope but lower deuterium excess (by 3.9‰) compared to values observed in the firnpack profile during the melt season. The δD‐δ¹⁸O regression line for the river water exhibited a lower slope compared to the surface snow/ice samples, although they were closely located on the δD‐δ¹⁸O plot. Isotope values for the river and glacier surface meltwater showed little scatter around the δD‐δ¹⁸O regression line, although the samples were from different glaciers and were collected on different days. Results indicate a high consistency of isotopic fractionation in the δD‐δ¹⁸O relationships, as well as a general consistency and temporal covariation of meltwater isotope values at the catchment scale. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Spatial explicit soil moisture analysis: pattern and its stability at small catchment scale in the loess hilly region of China          下载免费PDF全文

Feixiang Sun  Yihe Lü  Bojie Fu  Zhimin Ma  Xueling Yao 《水文研究》2014,28(13):4091-4109

Soil moisture is essential for plant growth and terrestrial ecosystems, especially in arid and semi‐arid regions. This study aims to quantify the variation of soil moisture content and its spatial pattern as well as the influencing factors. The experiment is conducted in a small catchment named Yangjuangou in the loess hilly region of China. Soil moisture to a depth of 1 m has been obtained by in situ sampling at 149 sites with different vegetation types before and after the rainy season. Elevation, slope position, slope aspect, slope gradient and vegetation properties are investigated synchronously. With the rainy season coming, soil moisture content increases and then reaches the highest value after the rainy season. Fluctuation range and standard deviation of soil moisture decrease after a 4‐month rainy season. Standard deviation of soil moisture increases with depth before the rainy season; after the rainy season, it decreases within the 0‐ to 40‐cm soil depth but then increases with depths below 40 cm. The stability of the soil moisture pattern at the small catchment scale increases with depth. The geographical position determines the framework of soil moisture pattern. Soil moisture content with different land‐use types is significantly increased after the rainy season, but the variances of land‐use types are significantly different. Landform and land‐use types can explain most of the soil moisture spatial variations. Soil moisture at all sample sites increases after the rainy season, but the spatial patterns of soil moisture are not significantly changed and display temporal stability despite the influence of the rainy season. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Are spatial patterns of soil moisture at plot scales generalisable across catchments,climates, and other characteristics? A synthesis of synoptic soil moisture across the Mid-Atlantic     

Charles I. Scaife  Jonathan M. Duncan  Laurence Lin  Christina Tague  Colin D. Bell  Lawrence Band 《水文研究》2021,35(9):e14313

The spatial variation of soil moisture over very small areas (<100 m²) can have nonlinear impacts on cycling and flux rates resulting in bias if it is not considered, but measuring this variation is difficult over extensive temporal and spatial scales. Most studies examining spatial variation of soil moisture were conducted at hillslope (0.01 km²) to multi-catchment spatial scales (1000 km²). They found the greatest variation at mid wetness levels and the smallest variation at wet and dry wetness levels forming a concave down relationship. There is growing evidence that concave down relationships formed between spatial variation of soil moisture and average soil moisture are consistent across spatial scales spanning several orders of magnitude, but more research is needed at very small, plot scales (<100 m²). The goal of this study was to characterise spatial variation in shallow soil moisture at the plot scale by relating the mean of measurements collected in a plot to the standard deviation (SD). We combined data from a previous study with thousands of new soil moisture measurements from 212 plots in eight catchments distributed across the US Mid-Atlantic Region to (1) test for a generalisable mean–SD relationship at plot scales, (2) characterise how landcover, land use, season, and hillslope position contribute to differences in mean–SD relationships, and (3) use these generalised mean–SD relationships to quantify their impacts on catchment scale nitrification and denitrification potential. Our study found that 98% of all measurements formed a generalised mean–SD relationship like those observed at hillslope and catchment spatial scales. The remaining 2% of data comprised a mean–SD relationship with greater spatial variation that originated from two riparian plots reported in a previous study. Incorporating the generalised mean–SD relationship into estimates of nitrification and denitrification potential revealed strong bias that was even greater when incorporating mean–SD observations from the two riparian plots with significantly greater spatial variation.  相似文献   

Wave propagation and strain localization in a fully saturated softening porous medium under the non‐isothermal conditions          下载免费PDF全文

SeonHong Na  WaiChing Sun 《国际地质力学数值与分析法杂志》2016,40(10):1485-1510

The (THM) coupling effects on the dynamic wave propagation and strain localization in a fully saturated softening porous medium are analyzed. The characteristic polynomial corresponding to the governing equations of the THM system is derived, and the stability analysis is conducted to determine the necessary conditions for stability in both non‐isothermal and adiabatic cases. The result from the dispersion analysis based on the Abel–Ruffini theorem reveals that the roots of the characteristic polynomial for the THM problem cannot be expressed algebraically. Meanwhile, the dispersion analysis on the adiabatic case leads to a new analytical expression of the internal length scale. Our limit analysis on the phase velocity for the non‐isothermal case indicates that the internal length scale for the non‐isothermal THM system may vanish at the short wavelength limit. This result leads to the conclusion that the rate‐dependence introduced by multiphysical coupling may not regularize the THM governing equations when softening occurs. Numerical experiments are used to verify the results from the stability and dispersion analyses. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

基于无人机数据的植被指数空间尺度效应研究     

魏高磊  吴太夏  王树东  杨莹莹 《地理空间信息》2021,19(4):4-9,40

利用cm级空间分辨率的无人机高光谱图像研究了NDVI、PRI等14种植被指数随空间尺度升高的变化规律,并分析了不同植被覆盖度(FVC)下植被指数的空间尺度效应,比较了各植被指数空间尺度效应的强弱。得到的结论如下:(1)随着空间尺度升高,不同植被指数的变化趋势和幅度并不一致;(2)cm级的空间分辨率下,由于植被类内光谱差异和冠层阴影的影响,植被指数在植被覆盖度大于等于0.5的中高植被覆盖下受空间尺度效应的影响更大;(3)由相对简单的比值形式构成的植被指数如NDVI、SR等,具有抵抗空间尺度效应的能力,增加计算公式的复杂性会降低这种能力;(4)对色素和冠层水分敏感的窄波段容易受到空间尺度效应的影响,进而使得由这些窄波段构成的植被指数对空间尺度变化更为敏感。  相似文献   

丽江-小金河断裂盐源段断裂带规模、断裂带结构及其历史活动性     

龚正  李海兵  唐方头  吴羿锋  王磊 《地质学报》2023,97(7):2111-2125

2008年汶川地震促使人们思考青藏高原东南缘走向和规模与龙门山断裂带相近的丽江- 小金河断裂的活动历史,但受限于地质条件制约断裂尤其是其北段相关研究极其薄弱。基岩断裂带的物质组成与结构特征是断层长期活动的产物,蕴含丰富的历史活动信息。本文以丽江- 小金河断裂盐源段多个天然剖面为研究对象,通过详细的断裂带宏观结构调查、断层岩显微构造及XRD分析发现：① 断层破碎带以一套厚度>20 m的破裂面密集带为特征,优势破裂面走向为NE20°~30°,推测为丽江- 小金河断裂长期活动形成的张剪性破裂;② 断层带核部以断层角砾岩和断层泥为主,灰岩角砾岩黏土矿物含量~2%,以伊利石和伊蒙混层为主,粉砂岩断层泥黏土矿物含量~52%,以坡缕石和绿泥石为主,石英含量36%,缺失长石类矿物。断裂带宏观结构和断层岩微观结构特征均表现为角砾呈棱角状,砾径差异极大且呈零散状分布,符合快速滑动特征,指示断层滑移方式为黏滑。此外,核部断层岩带统计厚5~8 m,这一规模相对于龙门山映秀- 北川断裂带核部180~280 m和安县- 灌县断裂带核部40~50 m显著偏小,表明前者自形成以来的活动性远低于后者,两者的地震行为并不能简单类比。结合断裂在宏观结构特征、断层岩成分与种类以及所反映的滑动方式与隆升剥蚀量的差异,认为丽江- 小金河断裂更可能是鲜水河断裂切断锦屏山- 龙门山构造带之后形成的,晚新生代与龙门山断裂带具有不同的活动历史。  相似文献   

粗粒土大型剪切试验剪切带变形特征分析     

张茜  邓辉  李强  黎志 《工程地质学报》2015,23(1):30-36

采用含有叠环的大型粗粒土直剪试验设备进行试验,叠环作为剪切盒的重要组成部分,可以在剪切时根据粗粒土的结构形成多组剪切面,能够明显地展现出粗粒土的剪切变形特征.为了分析硬质岩粗粒对粗粒土的剪切强度和变形的影响,对粗粒岩性为花岗岩的粗粒土进行大型叠环式直剪试验.通过分析得到试验特征规律,研究粗粒土在剪切过程中的颗粒运动,得出花岗岩粗粒对其组成的粗粒土的剪切强度和变形有很大的影响.硬质岩性的花岗岩颗粒在剪切时不易被剪碎,在剪切过程中主要做错位、翻滚运动.低轴压下,剪切带位移会出现阶梯现象,而在高轴压下,剪切带位移为线性变化,并表现出更加明显的剪胀现象.粗粒土在剪切破坏后依然具有较高的抗剪强度和稳定性,为工程建设中土石体材料的选取提供了一定的借鉴.  相似文献   

矿山遥感编图中的高分辨率遥感数据选择与比例尺计算方法   总被引：2，自引：1，他引：1  

何芳  李林  徐友宁  柯海玲  张江华  乔冈  刘瑞平  陈华清 《地质通报》2015,34(11):2037-2046

通过对青海调查矿区多种高分辨率卫星数据处理后形成的图像进行解译和编图,掌握了合理选择遥感数据信息源、利用制图软件计算遥感影像图比例尺及编制野外调查和成果解译图的技术方法。得出在选择遥感数据时要考虑不同数据的技术参数、性价比及调查区面积;明确了当图像的出图分辨率确定后,其比例尺与图像的空间分辨率、像素大小、文档大小有直接关系,同时建立了计算遥感图像最佳比例尺和最佳出图比例尺的公式和方法;介绍了利用Photoshop和Mapgis软件,编制矿山野外调查用图和遥感解译成果图件的流程及方法。这些工作的完成对青海矿业开发地质环境效应调查起到了积极的指导作用,也充分体现了高分辨率遥感图像在工作条件艰苦地区的优势作用。  相似文献