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The only source of drinking water in Vilnius City, Lithuania's capital, is groundwater. It can be supplied from 20 wellfields situated in the City or its environs. About half of them (11) are located in the valley of the Neris River crossing the City. The exploited aquifers were formed by melting continental glaciers and modified by the river. Until 1990 groundwater resources had not been conserved—the per capita consumption for domestic use in Vilnius reached 350 l/day. After 1990, due to the increasing cost of supplying drinking water, its consumption was reduced by a factor of three. As pumping rates of wellfields in Vilnius were increased or decreased, the groundwater quality was changed significantly. It is mainly affected by the surface water and shallow aquifers of the hydrologic system. The unoxidised organic matter that enters the exploitable aquifers from rivers and polluted shallow groundwater consumes scarce oxygen resources, thus creating anoxic conditions favourable for increasing the accumulation of iron, manganese and ammonium. Modelling and monitoring data show that the concentrations of sulphates and chlorides in Vilnius wellfields indicate not only the rise of brackish water from below, but also downward seepage of polluted surface water into the aquifers. 相似文献
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Groundwater abstraction and contamination in Lithuania as geoindicators of environmental change 总被引：1，自引：0，他引：1
Groundwater abstraction not only affects subsurface water, but also causes changes in the hydrosphere, lithosphere, and biosphere. There are certain symptoms of these environmental changes that might be designated as geoindicators. Geoindicators related to groundwater abstraction and contamination in Lithuania have been classified into three groups related to: (1) the decline/rise of groundwater levels, (2) the deterioration of groundwater quality, and (3) the intensification of water-rock interaction. On the basis of hydrogeological and hydrological investigations carried out over many years, different environmental impacts of intensive groundwater use are demonstrated. The most important among them are the formation of depression cones, intensification of groundwater pollution, saltwater encroachment, and the intensification of karst. 相似文献
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T.?Oberc-DziedzicEmail author K.?Klimas R.?Kryza C.?M.?Fanning 《International Journal of Earth Sciences》2003,92(5):701-711
Zircon ages recorded in gneissic rocks have recently been used as criteria to define and correlate various tectonic units and crustal blocks in the central European Variscides. A SHRIMP U–Pb zircon geochronological study of the Strzelin gneiss in the Fore-Sudetic Block (SW Poland) indicates the presence of: (1) inherited zircon cores of Palaeo- to Mesoproterozoic 206Pb-238U ages (between ca. 2,000 and 1,240 Ma), and (2) zoned rims of Neoproterozoic age with two distinct means of 600±7 and 568±7 Ma. The Proterozoic age range of the cores suggests that different Precambrian crustal elements were the source for the protolith of the gneiss. A likely scenario is the erosion of various Proterozoic granites and gneisses, sedimentation (after 1,240 Ma), and partial resistance of the original components to subsequent metamorphic dissolution and/or anatectic resorption (in Neoproterozoic times). The zoned zircon rims of both of the younger Neoproterozoic ages are indistinguishable in the cathodoluminescence images. The data are interpreted in terms of two different thermal events inducing zoned zircon overgrowth at ca. 600 and 568 Ma. In general, the new results confirm earlier assumptions of the Proterozoic age of the gneiss protoliths, and indicate their similarity to orthogneisses in the East Sudetes tectonic domain (e.g. the Velké Vrbno and Desná gneisses). The Neoproterozoic dates are different from the age of 504±3 reported earlier for the Gocicice gneiss from a neighbouring locality in the Strzelin Massif. The new data strongly indicate a Moravo-Silesian (Bruno-Vistulian) affinity for the Strzelin gneiss and support the hypothesis that the Strzelin Massif lies within the tectonic boundary zone between the West- and East Sudetes domains, which represents the northern continuation of the Moldanubian Thrust. 相似文献
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Algirdas Kazlauskas Vladas Vansevičius Audrius Bridžius Ramutis Drazdys Romualdas Kalytis 《Astrophysics and Space Science》2002,280(1-2):57-62
We investigate the effects arising from the filter transmission curve differences across the filter area in the 3G medium-band
photometric system proposed for GAIA. We discuss the accuracy of the transformations to the standard photometric system and
the precision of the determination of physical parameters for various types of stars using the 4-D classification procedure.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Impacts Of Urbanisation And Protection Of Water Resources In The Vilnius District,Lithuania 总被引：1，自引：0，他引：1
A. A. Klimas 《Hydrogeology Journal》1995,3(1):24-35
Vilnius municipality, Lithuanian Republic, is revising the general plan of city development. Different environmental scenarios of the city's growth possibilities have been evaluated. One of the most serious problems limiting the city's growth is water-resources protection. Increasing eutrophication of rivers and lakes is the result of pollution. Untreated sewage, recreation and agriculture are the most important sources of contamination. Therefore, certain limitations on the expansion of the city in the zones of surface-water protection are planned. The necessity of groundwater protection is further limiting the city's growth. The shallow water-table aquifer is vulnerable pollution almost everywhere, so it needs be highly protected where it is utilised for water supply or where it is replenishing deeper exploited aquifers. Eighteen to nineteen groundwater intakes are operated within the limits of the city and its suburbs. The principal artesian aquifer in the central and southwestern parts of the town is fairly vulnerable to pollution. Two groups of territories for controlling city growth are identified, on the basis of surface-water importance for recreation and groundwater for water supply. A method similar to GIS technologies was applied for this purpose. 相似文献
6.
Drinking water supply in Lithuania is entirely based on groundwater. Wellfields of Vilnius develop intermorainic ca. 50 m deep (in average) aquifer which is locally contaminated by chlorinated hydrocarbons— volatile organic compounds (VOCs). Groundwater abstraction activates VOCs migration from an abandoned factory into the pumping wells of one wellfield named “Vingis.” However monitoring data testify that only traces of VOCs were detected on the territory of this factory. Subsequent studies revealed the “secret”: dense VOCs have migrated from the territory of the polluter and have accumulated in lowermost places of pumped aquifer inside the wellfield. An attempt to ensure low concentration of VOCs in pumped water manipulating by pumping rates of more or less contaminated abstraction wells was not effective. Finally, an acceptable concentration of VOCs in supplied drinking water was ensured by permanent pumping out of the most polluted groundwater from some abstraction wells of the wellfield and diverting this water to the Neris River. 相似文献
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A. A. Klimas 《Environmental Geology》1996,27(4):320-328
Cities have a negative impact on the quality of shallow groundwater. Many of Lithuania's urban residents drink water from dug wells. Moreover, polluted shallow groundwater contaminates deeper aquifers of fresh drinking water. Therefore, this situation should be controlled and managed, as far as possible. In order to evaluate the quality of shallow groundwater in an urban area and to create an optimal monitoring system, an original methodology for groundwater mapping has been proposed. It resembles the GIS (geographical information system) technologies. The set of maps, laid one over another, consists of the following: (1) urbanization map, (2) geological-hydrogeological map, (3) groundwater chemistry map, (4) resulting groundwater chemistry factorial analysis map, and (5) pollution and pollutant transport map. The data obtained from studies on dug and geotechnical wells have been used for compilation of the maps. The system for shallow groundwater monitoring in the city with an area of 70 sq km and a population of 140,000 is proposed to consist of about 30 monitoring wells and several dug wells. 相似文献
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