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41.
42.
Houyi ZHENG Congqiang LIU Zhongliang WANG 《中国地球化学学报》2006,25(B08):174-174
Bedrock weathering and atmospheric deposition are the two primary sources of base cations (K^+, Na^+, Ca^2+ and Mg^2+) to forest ecosystems. Therefore, the key problem is to understand the relative inputs from these two sources and the cycling in the ecosystem. This study focuses on the effects of acid deposition on cation cycling in a small-forested karstic catchment in Guizhou Province. Sr isotope ratios were used as a tracer for understanding the transport process between the different cation pools: rock, soil, surface water, atmospheric deposition and plant. The samples of wet deposition, total deposition, throughfall, surface and ground waters, vegetation, and soil were monthly collected. The exchangeable Sr^2+ and Ca^2+ in soil samples were extracted by using 1 M ammonium acetate. The leaf-tissue samples were ashed at 550℃, and the residue was digested in ultrapure HClO4 and HNO3. All water samples were filtrated through 0.45 μm aperture filter paper. Base cation concentrations and Sr isotopic composition were analyzed for all the samples. The results show that acid deposition (average pH 4.9) frequently occurred in the studied region. Cation abundance follows an increasing manner from rainwater, throughfall, to surface water or ground water samples, suggesting that acid deposition at first eiuviates Ca^2+ , Mg^2+ and Sr^2+ from leaf, then the exchangeable cations from soil, and at last cations accumulate in surface water or ground water. 相似文献
43.
Karst groundwater protection in the Kupa River catchment area and sustainable development 总被引:1,自引:0,他引:1
One of the most significant water resources in the Republic of Croatia is the catchment area of the Kupa River, located in
the region bordering the Republic of Slovenia. About 88% of the total amount of water in this catchment originates in Croatia
and just 12% from Slovenia; therefore, the largest part of the catchment area (about 1000 km2) is on the Croatian side of the border. It is a typical karst area of the Dinarides with aquifers characterized by a relatively
rapid water exchange, high groundwater flow velocities and aquifers open to human impact from the surface. Consequently, the
aquifers are highly vulnerable and at risk. Due to the availability of large quantities of high-quality spring water (about
6 m3/s), the entire area has a strategic importance within the context of any future development strategy pertaining to the western
part of Croatia. The catchment area on the Croatian side was investigated using a wide range of research methods that included
a classical hydrogeological approach, the detailed hydrologic calculation of water balance to the hydrogeochemical analyses
and modelling. The objective was to determine protection zones and protection measures for the whole area. The difficulties
are increased due to the fact that the karst catchment area is crossed by major traffic corridors, oil pipelines and a railway
and that many settlements and a highly developed wood industry are present. The combination of protecting water resources
with adequate prevention measures and necessary remedial activities that should satisfy the very strict requirements necessary
for the protection of the karst aquifers while still allowing for present and future human activities is difficult – but not
impossible – to achieve. One good example is the present highway with a closed dewatering system and waste water treatment
before the water passes into the karst underground system. 相似文献
44.
Monitoring of Over Cutting Area and Lubrication Distribution in a Large Slurry Pipe Jacking Operation 总被引:1,自引:0,他引:1
Saeid Khazaei Hideki Shimada Takashi Kawai Junichi Yotsumoto Kikuo Matsui 《Geotechnical and Geological Engineering》2006,24(3):735-755
Slurry pipe jacking was firmly established as a special method for the non-disruptive construction of the underground pipelines
of sewage systems. Pipe jacking, in its traditional form, has occasionally been used for short railways, roads, rivers, and
other projects. Basically the system involves the pushing or thrusting of concrete pipes into the ground by a number of jacks.
In slurry pipe jacking, during the pushing process, mud slurry and lubricant are injected into the face and the over cutting
area that is between the concrete pipes and the surrounding soil. Next, the slurry fills voids and the soil stabilizes due
to the created slurry cake around the pipes. Fillings also reduce the jacking force or thrust during operation. When the drivage
and pushing processes are finished, a mortar injection into the over cutting area is carried out in order to maintain permanent
stability of the surrounding soil and the over cutting area. Successful lubrication around the pipes is extremely important
in a large diameter slurry pipe jacking operation.
Control of lubrication and gaps between pipes and soil can prevent hazards such as surface settlement and increases in thrust.
Also, to find voids around the pipes after the jacking process, in order to inject mortar for permanent stabilizing, an investigation
around the pipes is necessary. To meet these aims, this paper is concerned with the utilization of known methods such as the
GPR (Ground Penetrating Radar) system and borehole camera to maintain control of the over cutting area and lubricant distribution
around the pipes during a site investigation. From this point of view, experiments were carried out during a tunnel construction
using one of the largest cases of slurry pipe jacking in Fujisawa city, Japan. The advantages and disadvantages of each system
were clarified during the tests. 相似文献
45.
运用高分辨率层序地层学原理和方法,通过对钻井和地震资料的综合分析,在二连盆地吉尔嘎朗图凹陷下白垩统中识别出1个超长期基准面旋回(二级层序)SSC1和5个长期基准面旋回(三级层序):LSC1,LSC2,LSC3,LSC4,LSC5,分析了各旋回的发育特征。识别出五种类型的沉积体系:滨浅湖近岸水下扇、较深水湖浊积扇、滨浅湖扇三角洲、滨浅湖辫状河三角洲和河流沉积体系,并在等时地层格架内分析了各基准面旋回的沉积体系构成和储层砂体的发育情况。综合分析生、诸、盖条件后认为,在垂向上,LSC3旋回为本区最有利的储集层段,在平面上,本区的油气勘探应主要寻找宝饶构造带辫状河三角洲前缘砂体,主要储层砂体类型为前缘分流水道砂和前缘席状砂。 相似文献
46.
47.
惯性/双星组合导航系统的滤波与仿真 总被引:2,自引:0,他引:2
介绍了惯性导航系统和双星导航系统各自的运行方式和优缺点;详细推导了组合导航系统的误差方程和量测方程;介绍了Kalman滤波的整个过程并最后进行了仿真计算。仿真结果显示,惯性导航系统和双星导航系统的组合弥补了各自的不足,具有较好的精度和可靠性。 相似文献
48.
基于GIS的商业网点选址研究与实现 总被引:2,自引:0,他引:2
利用平面/网络优化模型,综合权衡市区选址的基本费用及商业网点日常经营的成本,引入交通便利因子作为限制条件,并运用直接搜索的Dixon方法,加强了不确定性选址问题的约束条件,降低不确定性问题计算的复杂度,减少在选址问题实现中主观因素对选址结果的影响。最后以某区新建商业网点选址为例,详细分析了直接搜索算法应用的具体过程。 相似文献
49.
50.