摘要:

Groundwater dating is known to be determination of the residence time of groundwater. This residence time is commonly defined as the length of time the water has been isolated from the atmosphere. The paper reviews isotope methods available for dating of old groundwater. Their residence time is supposed to be far outside the range of C-14 dating which is about 50000 years. These dating methods are based on the radioactive decay of long-lived radionuclides produced by interaction of cosmic radiation with gases in the atmosphere (Kr-81, Cl-36, I-129), on the accumulation of noble gases suo-surface produced by nuclear reactions including radioactive decay of U/Th series radionuclides (He-4, He-3), and on the disequilibrium between uranium isotopes due to water-rock interaction and radioactive decay (U-234, U-238). The paper presents the principles of these dating methods, refers to recent case studies and summarizes problem areas for further development and application of these methods.

ISSN:0021-1915    

DOI:10.1080/10256019008622433

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Early assessment of groundwater vulnerability during groundwater exploration is an important precondition for effective protection. Any attempt to assess the “vulnerability” is confronted with the very different factors influencing this property. In this paper we present a new concept to combine different factors on an objective basis. A protection index γ is defined and it is shown that this index can be obtained by the additative combination of a self-cleaning index (γs), a retardation index (γR) and a dilution index (γv). For the estimation of the latter one, isotope techniques are suitable. With lumped-parameter models, easy formulae are derived for the calculation of γvfrom tritium data. The applicability of this approach was tested with data from two field studies. The results obtained show that a reasonable assessment of groundwater vulnerability can be achieved. However, a lot of problems and questions remains to be solved by further investigation.

ISSN:0021-1915    

DOI:10.1080/10256019008622434

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The contineous increase of population in Cairo exceeding 10 millions inhabitants lead to the search for supplementary potable water resources in addition to the Nile River which is the principle drinking water source. Groundwater represents the main supplementary source. Evaluation of the groundwater feeding the so-called El-America Water Treatment Station which is one of the biggest potable water supplies at the northern of Cairo was carried out. Chemical and isotopic techniques were applied to estimate the suitability of this groundwater for drinking purposes. The chemical analysis includes the determination of sodium, potasium, calcium and magnesium concentrations in addition to those of chlorides, sulphates, bicarbonates and silicates, while the isotopic analysis includes oxygen-18 and deuterium. The overall chemical- and isotopic investigations determined the conditions at which the examined groundwater is suitable for drinking purposes.

ISSN:0021-1915    

DOI:10.1080/10256019008622435

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A general view is presented of deuterium and18O measurements of water samples collected at running and standing surface waters in German Democratic Republic. The values confirm earlier observations that the surface waters are influenced by evaporation with respect to the isotopic composition of groundwater. Nevertheless, stronger evaporation effects are restricted to larger lakes. The amount of surface water discharge from GDR to the Baltic Sea and the δD and δ18O values are discussed. The river Oder provides about 90% of the whole surface run-off. The other watercourses to the coast are unimportand. The mean heavy isotope content of surface run-off was calculated to be −8.3‰ for δ18O and −61‰ for δD (vs. SMOW), respectively.

ISSN:0021-1915    

DOI:10.1080/10256019008622436

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Salt efflorescences consisting of gypsum sampled mainly in the Schirmacher Oasis have been analyzed for the isotopic composition of the water of crystallization and of the sulphate-sulphur. For comparison, a few samples from other Antarctic locations (Guettard Range, Prince Charles Mts., Insel Mts.) were included in the study. The isotopic variations of the water of crystallization of secondary gypsum and the calculated isotopic composition of the mother solution reflect the local climatic conditions during the precipitation of the efflorescences. It is therefore possible to obtain qualitative information about the climatic conditions prevailing in the studied region.

ISSN:0021-1915    

DOI:10.1080/10256019008622437

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The existence of relatively stable elements beyond the present Periodic Table is predicted by various theoretical calculations. Considering all experiments of the search for superheavy elements (SHE) in nature and their non definite positive results further search seems to be pessimistic. Nevertheless in this work the scientific necessity to continue the search in nature by a modified manner using industrial enrichment steps is pointed out.

ISSN:0021-1915    

DOI:10.1080/10256019008622438

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Model investigations, carried out as laboratory coalification reactions with humous and sapropelitic sediments of different maturation degree, showed that conclusions can be drawn about the character of the parent rock of a natural gas using data of the chemical and isotopic composition of the organic substance in sediments and its coalification products.

ISSN:0021-1915    

DOI:10.1080/10256019008622439

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Characteristics of seasonal and annual variations of tritium concentration completed with hydrological long-term data from 1976–1989 for the Belgrade alluvial aquifer are presented. The highest tritium concentration in precipitation of an average year appears at the beginning of summer with a maximum in June (9 Bq/l) when the amount of precipitation is also high (102 l/m2). The quantity of tritium precipitating in this area was also the largest in the summer, especially in June (922 Bq/M2). Similar variations of tritium concentration was found in the waters of the Danube and the Sava with maxima 11.3 Bq/l (July) and 9 Bq/l (June) respectively. Tritium concentrations orginated from snowmelt influence to the occurrence of higher values during that period which is more distinct in the Sava. The groundwaters and particularly ones in the Ranney wells follow changes of levels, temperature and tritium content in the alluvial of Sava with a time lag from a few days to a month. During the period of observation tritium content was decreasing in all studied waters. The decrease was faster in precipitation (11.2 to 3.0 Bq/l) and the Sava and Renney wells (10.6 to 3.0 Bq/l) than in the Danube (13.1 to 5.2 Bq/l).

ISSN:0021-1915    

DOI:10.1080/10256019008622440

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An overview of environmental aspects of the tritium method is given. Temporal and local variations of the specific tritium activity of precipitations, particularly the decay of the bomb peak as well as the continential and latitude effects, are used to subdivide the tritium content of precipitations in bomb tritium and technogenic tritium for the example of the measurement series of Freiberg. Technogenic tritium is shown to have prevailed from the beginning of the eighties, whereas the emission of technogenic tritium has strongly decreased in Europe since the middle of the seventies.

ISSN:0021-1915    

DOI:10.1080/10256019008622441

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

From a sector within an extended Tertiary basin 21 groundwater samples as well as 3 rock samples of a Zechslein diapir were analysed for87Sr/86Sr-ralio. As a tendency the isotope ratio of the dissolved strontium is decreasing with increasing depth and strontium content. Furthermore, strontium content and salinity are correlated. With two exceptions the isotope data are in the range between about 0.7080 and 0.7100. Significant differences in the strontium isotope composition were found between the Zechstein salts and the typical groundwaters. This shows, that the Zechstein diapir can not be the source of the higher salinity in parts of the groundwater system. The results are discussed.

ISSN:0021-1915    

DOI:10.1080/10256019008622442

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor