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91.
92.
Wei-min Ye Zi-yuan Qi Bao Chen Ji Xie Yu Huang Yao-ru Lu Yu-Jun Cui 《Environmental Earth Sciences》2011,64(1):269-276
Karst rocky desertification is a process of land degradation involving serious soil erosion, extensive exposure of basement
rocks. It leads to drastic decrease in soil productivity and formation of a desert-like landscape. In this regard, changes
in climatic conditions are the main origin of the soils degradation. Indeed, soils subjected to successive dry/wet cycling
processes caused by climate change develop swelling and shrinkage deformations which can modify their water retention properties,
thus inducing the degradation of soil–water capacity. The ecological characteristics of cultivation soils in karst areas,
Southwest of China, are extremely easy to be affected by external environmental factors due to its shallow bedding and low
vegetation coverage. Based on the analysis of the climate (precipitation) of this region during the past decades, an experimental
study has been conducted on a cultivated soil obtained from the typical karst area in southwestern China. Firstly, the soil–water
properties have been investigated. The measured soil–water retention curve shows that the air-entry value of the soil is between
50 and 60 kPa, while the residual saturation is about 12%. Based on the experimental results, three identifiable stages of
de-saturation have been defined. Secondly, a special apparatus was developed to investigate the volume change behavior of
the soil with controlled suction cycles. The vapor equilibrium technique was used for the suction control. The obtained results
show that under the effect of dry/wet cycles, (1) the void ratio of the cultivated soil is continuously decreasing, leading
to a gradual soil compaction. (2) The permeability decreases, giving rise to a deterioration of water transfer ability as
well as a deterioration of soil–water retention capacity. It is then obvious that the long-term dry/wet cycling process caused
by the climate change induce a continuously compaction and degradation of the cultivated soil in karst rocky desertification
areas. 相似文献
93.
Microbial community changes in contaminated soils in response to phenanthrene amendment 总被引:4,自引:1,他引:3
S. Y. Zhang Q. F. Wang S. G. Xie Ph.D. 《International Journal of Environmental Science and Technology》2011,8(2):321-330
Leachate and reclaimed wastewater have become the important sources of polycyclic aromatic hydrocarbons in soils. However, the information on bioremediation of leachate and reclaimed wastewater-contaminated soils is still lacking. Identification of changes in microbial structure or of enriched genera related to biodegradation could aid identification of particular organisms or consortia capable of degrading polycyclic aromatic hydrocarbons in these contaminated soils. In this study, terminal restriction fragment length polymorphism, coupled with 16S Ribosomal ribonucleic acid clone library analysis, was applied to investigate the composition of bacterial community in leachate-contaminated soil or grassland soil irrigated reclaimed wastewater and the response to phenanthrene amendment. Results showed that phenanthrene amendment had significant but different impacts on microbial community structure, dependent on soil source. Several greatly enriched terminal restriction fragments with phenanthrene biodegradation were identified. Moreover, genus rhizobacteria, possibly linked to phenanthrene biodegradation, was firstly reported in this study. This work might provide some new insights into bioremediation of polycyclic aromatic hydrocarbons-contaminated soils. 相似文献
94.
裂隙岩体宏观力学参数的二维数值模拟 总被引:1,自引:0,他引:1
岩体通常含许多不同尺度的裂隙,因而力学性质非常复杂。由于现场测试及常规实验室试验常受各种条件的限制,因而其不能准确反映岩体的宏观物理力学性质。本文基于有限元分析软件对二维情况下的完整岩体和含不同倾角的软弱夹层的岩体在单轴和双轴压缩下进行了数值模拟,得到岩体变形的应力-应变曲线。该类曲线能反映裂隙对岩体力学参数的影响,对于指导工程实践有一定的意义,并且为获取岩体力学参数提供了新的途径。 相似文献
95.
96.
相山火山盆地主体岩石为一套由熔结凝灰岩、流纹英安岩、流纹英安斑岩、碎斑熔岩、粗斑花岗斑岩及似斑状花岗岩组成的酸性火山-侵入杂岩体, 构成了两个完整的喷发-溢流(侵出)-侵入的岩浆活动亚旋回。本文在野外地质调查的基础上, 采用SIMS、LA-ICP-MS技术对主要岩类进行了高精度的锆石U-Pb年代学研究, 并建立了火山-侵入杂岩体的演化序列。结果表明, 打鼓顶组熔结凝灰岩代表了相山火山-侵入活动的最早期产物, 其锆石U-Pb年龄为140.7±2.7 Ma、140.1±1.8 Ma和138.2±1.6 Ma, 第一亚旋回主体流纹英安岩的锆石U-Pb年龄135.0±1.8 Ma。鹅湖岭组熔结凝灰岩代表了火山-侵入活动的第二亚旋回的开始, 其U-Pb年龄为135.6±1.2 Ma, 第二亚旋回主体碎斑熔岩的锆石U-Pb年龄133.6±1.3 Ma, 沙洲单元的粗斑花岗斑岩和似斑状花岗岩属于该亚旋回最晚期的侵入岩, 其锆石U-Pb年龄代表了相山火山-侵入活动的结束时间(分别为133.4±1.2 Ma和133.9±1.1 Ma)。相山早白垩世火山-侵入活动延续时间较短, 整体上呈现一个连续的过程, 初始时间在141 Ma附近, 结束时间在132 Ma左右。概言之, 第一亚旋回(141~135 Ma)以形成熔结凝灰岩、流纹英安岩和流纹英安斑岩为主, 第二亚旋回(135~132 Ma)以熔结凝灰岩、碎斑熔岩、粗斑花岗斑岩和似斑状花岗岩为主。岩石地球化学和野外地质特征也与两个亚旋回火山-侵入岩浆活动相吻合。 相似文献
97.
Acta Geochimica - During the Wenchuan Fault Scientific Drilling Project, we determined the values of total mercury (HgT) and gaseous elemental mercury (GEM) from drilled cores and drilling mud,... 相似文献
98.
99.
内蒙古北山额济纳旗小红山钒钛磁铁矿床SHRIMP锆石U-Pb定年及其意义 总被引:1,自引:0,他引:1
小红山钒钛磁铁矿床是近年内蒙古北山地区新发现的一个中型钒钛磁铁矿床,含矿辉长岩体侵位于蓟县系平头山组,岩体具全岩矿化,工业矿体主要赋存于中粗粒辉长岩中。采用SHRIMP锆石U-Pb定年方法对小红山中粗粒辉长岩体进行了年代学研究,获得该岩体的锆石微区原位SHRIMP U-Pb年龄为424±6Ma,表明小红山钒钛磁铁矿成岩成矿事件发生于中志留世。该时期钒钛磁铁矿床的发现,揭示了北山地区早古生代处于陆缘裂谷环境,这对研究和认识北山地区地质构造演化及开展岩浆矿床找矿具有重要意义。 相似文献
100.
Roof separation is one of the major indications for coal mine roadway roof accidents. Therefore, it is important that efforts be made to detect roadway roof separation. Currently, the instrument used for detecting roadway roof separation is the roof-off-the-strata indicator, but its installation and use is complicated and the need is greater than can be managed. This thesis takes ground penetrating radar (GPR) as a means for roof separation detection and analyzes its feasibility for use in detecting roof separation both theoretically and experimentally. First, numerical simulation experiments on roof separation detection are carried out using GprMax2D software. The results show that it is feasible to detect roof separation by using GPR electromagnetic waves. Next, physical simulation experiment on roof separation detection is carried out using MALA GPR (RAMAC/GPR). Lastly, the traditional image segmentation algorithm of 2D maximum between a cluster variance is improved to interpret the GPR signal. Good results were achieved using the improved algorithm to interpret detection signals of roof separation by GPR in a physical simulation experiment. 相似文献