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41.
A geochemical evaluation of the Szc-Halimba-Kisld area, Hungary, covering an area of more than 200 km2 is presented using different statistical and geostatistical methods. The study area is a representative example of allochtonous karst bauxite accumulation. The three groups of deposits studied here have been explored and mined since 1950. Several thousand boreholes have been drilled, and bauxite cores were analyzed for the five main chemical components. A total of 80,000 pleces of analytical data were processed, followed by a geological examination of borehole logs and of mining excavations.The quantitative geochemical evaluation of the data set led to both geochemical and practical results: The geochemical behavior of the allochtonous, clastic karst bauxite deposits differs essentially from that of the autochtonous and parautochtonous ones, as well as that of the lateritic bauxite deposits. The deposits of the study area can be split into several subsequent geochemical-sedimentological units, each representing an event of bauxite transport and accumulation. Clear regional patterns can be revealed in the composition of these units. The geostatistically measured chemical variability of the geochemical units is rather different, the lowest units showing the smallest variability. The interrelations of the main chemical components are weaker and more irregular in the studied deposits than in the autochtonous lateritic bauxite deposits. Additional local genetic features, such as transport routes, can be delineated by the methods applied. Within each deposit, local changes of chemical composition and of its variability can be determined more precisely. These results can be used in bauxite prospecting and exploration, because areas of high or low bauxite quality can be predicted. 相似文献
42.
G. Günay 《Environmental Geology》2006,51(2):229-240
The Sakarya River is one of the largest rivers in Turkey and is fed mainly from Sakaryabaşı springs. The Sakaryabaşı springs are located in the Central Anatolia and issue from confined/semi-confined karst having a thermal component and therefore, having quite different hydrogeological characteristics as compared to the Taurus Karst region, a typical example of the Mediterranean type of karst. The karstic carbonate rocks that form the groundwater reservoir are overlain by a thick semi-pervious overburden of mainly clastics of Neogene age. Tectonics is the major factor controlling the occurrence of the karst springs in the area where topography is rather flat. This study aimed at explaining the occurrence and movement of the karst groundwater within the system by use of hydrogeological, chemical, and isotopic tools. Isotopic composition of the waters revealed that all waters in the region are of meteoric origin and the thermal component is due to deep circulation. The catchment area of the hydrogeological system extends to the south and groundwater movement is towards the outlets, which are in a depression along a major fault. The movement of the groundwater, based on analysis of remotely sensed images, is controlled mainly by structural elements. 相似文献
43.
Subsidence due to peat oxidation and impact on drainage infrastructures in a farmland catchment south of the Venice Lagoon 总被引:1,自引:0,他引:1
Large agricultural areas reclaimed in the past century, south of the Venice Lagoon, have experienced significant land subsidence
due to oxidation of peat organic soils. This has exposed the region to flood hazard particularly during severe storms and
has contributed to increase the marginal management cost of the infrastructures (ditches, levees, pumping stations) designed
to operate the drainage system. Direct measurements and indirect evidence from the channel network suggest a land settlement
between 1.5 and 2 m over the past 70 years. This paper provides an overview of the problem with important information on its
most recent evolution. 相似文献
44.
Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (Corg), extractable extracellular carbon (Cext), total soil nitrogen (Nt), alkali-hydrolyzable nitrogen (Nah), total phosphorus (Pt), available phosphorus (Pa) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-Cmic, and by calculation from substrate-incubation respiration, SIR-Cmic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of Cmic/Corg and BR/Cmic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as Corg and Cext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-Cmic, SIR, and SIR-Cmic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation. 相似文献
45.
Federica Marcolini 《Mathematical Geology》2006,38(6):667-678
Fourier analysis was used in this study to help a specific determination of some Mimomys (Arvicolidae, Rodentia, Mammalia)
species. Several Pliocene and Pleistocene Central and Western European Mimomys species first lower molar contours have been
decomposed by Complex Discrete Fourier Transform. Inter- and intra-specific comparisons have been performed on the harmonics
obtained from the decomposition and some problematic specimens have been classified. 相似文献
46.
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
47.
The hydraulic behaviour of the karst aquifer in the Hubelj spring catchment area (SW Slovenia) was studied by using an indirect
research method based on natural tracers. The variations of natural tracers (in precipitation and in groundwater) during the
storm event made possible the separation of the Hubelj spring storm hydrograph by the three-component separation technique.
The results produced information on the aquifer recharge, storage and discharge processes, as well as on the mechanisms that
affected them. They verified the so-called epikarst hypothesis presuming that an important part of a karst aquifer recharge
reaches rapidly and intensively from the epikarst zone. It was demonstrated that epikarst water could occupy up to 50% of
the spring discharge during precipitation events. This phenomenon could have important consequences on protection and management
of the problems of karst aquifers, including engineering problems in karst areas. With this respect the results could give
way to new engineering ideas. 相似文献
48.
Athanasios Maramathas 《Hydrogeology Journal》2006,14(7):1360-1366
A new approach to the method of artificial upraising of the water outlet point, for management and development of brackish karst springs, uses the MODKARST model. Brackish karst springs simulation can be used to estimate the necessary upraising of the spring elevation, so that sea-water intrusion is blocked. The consequent freshwater loss to the sea, due to this upraising, can also be estimated. The method has been applied to the periodically brackish karst Almiros spring at Heraklion of Crete, Greece. The spring simulation showed that the sea-water intrusion could be prevented through an artificial upraising of the water-outlet point, realized by the construction of a dam. The exact upraising has been estimated. Freshwater loss to the sea because of this upraising has also been estimated. The model could also be used as a tool for the management of the spring. For example, it was used to assess management options for the spring during the depletion period of the year 1994. The best scenario for the development of the spring during this period has been estimated. 相似文献
49.
以中国科学院盐亭紫色土农业生态试验站小流域为例,研究不同土壤侵蚀沉积地段(斜坡和沟谷不同部位)的土壤结构特征,以了解侵蚀沉积对土壤结构的影响。结果表明,在植被覆盖较好的坡体顶部,土壤侵蚀较弱,团聚度达到30.1%,MWD变化为3.4mm,土壤结构良好;沟谷底部由于沉积而有较多细土物质并具有适宜的水分条件,有利于土壤团聚体的形成,结构状况亦较好,团聚度达到50.3%,结构保持率为35.4%;而坡腰侵蚀较严重,团聚度仅为13.6%,结构保持率为14.1%,土壤结构状况较差。 相似文献
50.
Daniel H. Doctor E. Calvin Alexander Jr Metka Petrič Janja Kogovšek Janko Urbanc Sonja Lojen Willibald Stichler 《Hydrogeology Journal》2006,14(7):1171-1191
Karst aquifer components that contribute to the discharge of a water supply well in the Classical Karst (Kras) region (Italy/Slovenia) were quantitatively estimated during storm events. Results show that water released from storage within the epikarst may comprise as much as two-thirds of conduit flow in a karst aquifer following rainfall. Principal components analysis (PCA) and end-member mixing analysis (EMMA) were performed using major ion chemistry and the stable isotopes of water (δ18O, δ2H) and of dissolved inorganic carbon (δ13CDIC) to estimate mixing proportions among three sources: (1) allogenic river recharge, (2) autogenic recharge, and (3) an anthropogenic component stored within the epikarst. The sinking river most influences the chemical composition of the water-supply well under low-flow conditions; however, this proportion changes rapidly during recharge events. Autogenic recharge water, released from shallow storage in the epikarst, displaces the river water and is observed at the well within hours after the onset of precipitation. The autogenic recharge end member is the second largest component of the well chemistry, and its contribution increases with higher flow. An anthropogenic component derived from epikarstic storage also impacts the well under conditions of elevated hydraulic head, accounting for the majority of the chemical response at the well during the wettest conditions. 相似文献