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51.
形成岩溶的高阻碳酸盐岩对电磁波的吸收较弱,而且成层沉积的特定环境使碳酸盐岩地区岩石的各向异性现象较明显,由于地空界面的存在及岩溶洞壁两侧介质电性差异明显,界面清晰,又使电磁波出现强烈的反射及散射现象,从理论上对碳酸盐岩地区电磁波传播的特有现象进行了研究和分析,并给出结论。 相似文献
52.
Environmental and legal aspects of karst areas 总被引:3,自引:0,他引:3
Environmental impacts on karst settings are common as they are more sensitive than those of other rock terrains. Regulatory
procedures that are effective in other rock terrains are not necessarily applicable to karst settings. Development and exploitation
by man that affect the karst hydrology regime can trigger catastrophic events and result in numerous legal actions where the
effects of changes go beyond property boundaries. A great variety of regulations and examples of litigation exist for karst
areas.
Received: 25 October 1994 · Accepted: 17 October 1995 相似文献
53.
Acidification of groundwater lags behind acid deposition due to the relatively long water residence time in conjunction with
various buffering processes in the soil zone and deeper aquifer (chemical weathering, cation exchange, sulfate sorption, and
N uptake by the biomass). Extensive field data from eight forested catchments in the Bunter Sandstone of the Black Forest,
including results from water budget studies and hydrochemical analysis of stream and spring waters, were used to simulate
the future evolution of ground-water acidification with the MAGIC model. The present acid deposition exceeds the “critical
load” (here meaning buffering due to chemical weathering and protonation of organic acids) in six of eight catchments. Two
catchments are well buffered because they contain carbonate-bearing layers in the Upper Bunter sandstone. Transient buffering
(i.e., cation exchange, N uptake, the sulfate sorption) thus far prevents worse acidification, but this effect will decline
in the future. For one of the poorly buffered catchments (Seebach), a two-layer simulation was carried out, based on extensive
data from 10 years of measurements. Validation of the long-term simulations by hydrochemical and soil data was hampered by
strong annual variations but generally supported by paleolimnological studies. In the future, reductions in the S deposition
by 20% and the N deposition by 10% up to the year 2030 are assumed as the most probable scenario. N uptake through soil and
vegetation will come to an end as suggested by decreasing C/N ratios of the organic matter. This process is arbitrarily included
in the simulations. In the periglacial soil layer, acidification will decrease until the year 2030 and then approach a steady-state
condition. In the fractured aquifer, acidification will also proceed at a decreasing rate; however, sulfate desorption up
to the year 2130, the end of simulated period, will prevent earlier remediation. Despite a significant reduction in S deposition
since the mid-1980s, further efforts are necessary to reduce the emission of acidifying substances. Liming in the recharge
area is partially effective to ameliorate “shallow” groundwater but largely fails to ameliorate “deeper” groundwater in the
sandstone aquifer.
Received: 30 July 1996/Accepted: 23 January 1997 相似文献
54.
在岩溶地区,地下水的超强度开采与工业“三废”及生活废弃物不合理的排放,造成了地下水较严重的污染。用动态系统方法建立的地下水污染时间序列递推预测模型,在岩溶地下水环境质量预测与管理方面都具有指导意义。 相似文献
55.
The occurrence of land subsidence in the Kingdom Saudi Arabia is either natural or man-made. Natural land subsidence occurs due to the development of subterranean voids by a solution of host rocks in carbonate and evaporite terrains, over many areas of Saudi Arabia. Man-induced land subsidence is either due to the removal of groundwater in the agricultural areas or to wetting of unstable soils. Therefore, earth fissures and a lowering of the ground surface in unconsolidated sediments took place in alluvial plains and volcanic vent terrains. Unstable soils include Sabkha soils and loess sediments. These types of soils occur in coastal plains, desert areas and volcanic terrains. When this soil is wetted either during agricultural activities, waste disposal or even during a rain storm, subsidence takes place due to either the removal of salts from the Sabkha soil or the rearrangement of soil particles in loess sediments. 相似文献
56.
Karst Hazard Assessment of Eastern Saudi Arabia 总被引:1,自引:0,他引:1
Karst phenomena exist in areas in the eastern part of Saudi Arabia, forming solution features such as sinkholes, collapsed dolines and solution caverns, as a result of the chemical leaching of the carbonate and evaporite formations by percolating water. The instability of these karst phenomena could produce land subsidence problems. This paper reviews the geology of documented karstic rock units in Saudi Arabia and proposes a simple engineering classification of the solution features characteristic of limestone. Two case histories in the Dhahran area, eastern Saudi Arabia, will be used as examples for the application of a modified engineering classification. 相似文献
57.
结合水化学的野外观测及室内计算,作者对桂林岩溶试验场、四川黄龙风景区和贵州乌江渡坝区3个岩溶动力系统的碳稳定同位素特征进行了分析,进而对系统的性质、系统中CO_2的来源、碳酸盐沉积过程中的碳同位素动力分馏、水化学和钙华的成因及热水钙华的~(14)C测年等地球化学问题作了探讨。结果表明,桂林岩溶试验场属于表层岩溶作用动力系统,其中的侵蚀动力主要来源于大气降水溶解土壤中的CO_2;四川黄龙风景区属于深部岩溶动力系统,侵蚀动力来自大气降水溶解幔源的CO_2;贵州乌江渡坝区岩溶系统,虽然属于表层岩溶动力系统,但其中一部分的同位素和水化学特征已受到人类活动的重大影响。 相似文献
58.
物探方法在岩溶勘查中的应用综述 总被引:7,自引:0,他引:7
简要介绍了岩溶勘察中常用物探方法的基本原理和技术,并举例说明其在岩溶地区进行水利水电工程地质勘察、岩溶地下水寻找、环境保护和溶洞探测时的有效性。 相似文献
59.
An experimental micrometeorological set-up was established at the CARBOEURO-FLUX site in Tharandt, Germany, to measure all relevant variables for the calculation of the vertical and horizontal advective fluxes of carbon dioxide. The set-up includes two auxiliary towers to measure horizontal and vertical CO2 and H2O gradients through the canopy, and to make ultrasonic wind measurements in the trunk space. In combination with the long-term flux tower an approximately even-sided prism with a typical side-length of 50 m was established. It is shown that under stable (nighttime) conditions the mean advective fluxes have magnitudes on the same order as the daily eddy covariance (EC) flux, which implies that they play a significant, but not yet fully understood, role in the carbon budget equation. The two advective fluxes are opposite and seem to cancel each other at night (at least for these measurements). During the day, vertical advection tends to zero, while horizontal advection is still present implying a flow of CO2 out of the control volume. From our measurements, a mean daily gain of 2.2 gC m–2 d–1 for the horizontal advection and a mean daily loss of 2.5 gC m–2d–1 for the vertical advection is calculated for a period of 20 days. However the large scatter of the advective fluxes has to be further investigated. It is not clear yet whether the large variability is natural or due to measurement errors and conceptual deficiencies of the experiment. Similar results are found in the few comparable studies. 相似文献
60.