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1.
The principal relationships between radon (222Rn and 220Rn) exhalation intensities and the morpho-dynamic elements of humid tropical landscapes have been established and analyzed with the objective of elaborating Rn exhalation models, which can be used on the scale of small habitational nuclei. The current radioactive processes of generation, emanation and migration of Rn, in relation to its exhalation rates on a landscape slope of granitic rock having normal U and Th contents, were correlated with the latosol-podzolic soil association developed as a product of supergene processes during geological and pedological times and also with the water regime of an overlying phreatic aquifer. This approach, encompassing pedogeochemical models of radionuclide dispersion linked to soil systems and surface geochemistry, was framed within a tridimensional, interdisciplinary and systemic focus, using concepts of nuclear physics, climate and hydrogeology. The characteristic signatures of elementary landscapes include (1) different landforms, namely eluvial, transeluvial and superaqual, (2) residual soils having varying types, thicknesses and perma-porosities and (3) radioanomalies corresponding to different U and Th concentrations, secondary hosting minerals and also to different pedological ages. Considering these factors and their spatial relationships and on the basis of moisture content of soils, it is postulated that the highest Rn exhalation rates, especially of 222Rn, are confined to superaqual and transeluvial landscapes. In an eluvial landscape, the Rn fluxes are found to be less important even though gamma anomalies exist mainly due to the presence of resistant minerals containing U and Th. In short, the products of supergene alteration organized in a sloping system can exhibit Rn exhaling intensities higher than that measured on unaltered subjacent rock. Hence, the understanding of U, Th, Ra and Rn behavior on a surface environment is fundamental for the formulation of prognostic Rn exhalation models associated with the elementary humid tropical landscapes. Further, the pedogeochemical information provides important clues supplementing the lithostructural data for delineating preferential sites of Rn fluxes especially on scales compatible to small habitational nuclei or unitary dwellings.  相似文献   

2.
The mechanism of222Rn release into fracture fluids by direct alpha-recoil, lattice and grain boundary/micro-crack diffusion is discussed. Experimental measurements of222Rn release into surrounding air and water phases have been made for crystalline rock specimens with well defined surface areas. The222Rn flux from an infinite plane surface and hence the effective diffusion length of222Rn in the rock matrix has been estimated.The222Rn flux from plane crystalline rock surfaces has been used in conjunction with a simple hydrological model of the reservoir to calculate the222Rn content of the return fluids of a geothermal doublet circulation system. For given production rate and piezometric difference between the injection and production wells, the222Rn content of the return fluid is dependent upon the distribution of flow path lengths and fracture apertures in the reservoir. Matching of the calculated and experimental222Rn contents of the return fluids has been used to select appropriate parameters for the reservoir model and hence to estimate the extent of the heat-transfer surface. The model estimates the fracture width of the flow paths, total swept surface area and fracture volume within the reservoir.  相似文献   

3.
A calculation method for determining the amount of Rn isotopes and daughter products at the start of measurement (CRAS) is proposed as a more accurate means of estimating the initial Rn concentration in soil gas. The CRAS utilizes the decay law between 222Rn and 220Rn isotopes and the daughter products 218Po and 216Po, and is applicable to α-scintillation counter measurements. As Rn is both inert and chemically stable, it is useful for fault investigation based on the soil gas geochemistry. However, the total number of α particles emitted by the decay of Rn has generally been considered to be proportional to the initial Rn concentration, without considering the gas condition with respect to radioactive equilibrium. The CRAS method is shown to be effective to derive Rn concentration for soil gases under both nonequilibrium conditions, in which the total number of decays increases with time, and equilibrium conditions, which are typical of normal soil under low gas flux. The CRAS method in conjunction with finite difference method simulation is applied to the analysis of two active fault areas in Japan, and it is demonstrated that this combination could detect the sharp rises in 222Rn concentrations associated with faults. The method also allows the determination of fault geometry near the surface based on the asymmetry variation of the Rn concentration distribution when coupled with a numerical simulation of 222Rn transport. The results for the new method as applied to the two case studies are consistent with the data collected from the geological survey. It implies that the CRAS method is suitable for investigating the fault system and interstitial gas mobility through fractures. The present analyses have also demonstrated that high Rn concentrations require the recent and repeated accumulation of 222Rn parents (230Th and 226Ra) in fault gouges through deep gas release during fault movement.  相似文献   

4.
In the Gran Sasso fissured carbonate aquifer (central Italy), a long-term (2001–2007) spatio-temporal hydrochemical and 222Rn tracing survey was performed with the goal to investigate groundwater flow and water–rock interaction. Analyses of the physico-chemical parameters, and comparisons of multichemical and characteristic ratios in space and time, and subsequent statistical analyses, permitted a characterisation of the hydrogeology. At the regional scale, groundwater flows from recharge areas to the springs located at the aquifer boundaries, with a gradual increase of mineralisation and temperature along its flowpaths. However, the parameters of each group of springs may significantly deviate from the regional trend owing to fast flows and to the geological setting of the discharge spring areas, as corroborated by statistical data. Along regional flowpaths, the effects of seasonal recharge and lowering of the water table clearly cause changes in ion concentrations over time. This conceptual model was validated by an analysis of the 222Rn content in groundwater. 222Rn content, for which temporal variability depends on seasonal fluctuations of the water table, local lithology and the fracture network at the spring discharge areas, was considered as a tracer of the final stages of groundwater flowpaths.  相似文献   

5.
In arid regions of western China, water resources come from mountain watersheds and disappear in the desert plain. The exchange of surface water and groundwater takes place two or three times in a basin. It is essential to analyze the interaction of groundwater with surface water to use water resources effectively and predict the change in the water environment. The conventional method of analysis, however, measures only the flow of a stream and cannot determine groundwater seepage accurately. As the concentration of Radon-222 (222Rn) in groundwater is much higher than in surface water, the use of 222Rn was examined as an indicator for the analysis of the interaction between surface water and groundwater. Measurement of the 222Rn concentration in surface water was conducted to detect groundwater seepage into a stream in the middle Heihe Basin of northwestern China. Furthermore, the simultaneous groundwater flow into and out of a stream from the aquifers was quantified by solving the 222Rn mass balance equation, in which the losses of gas exchange and radioactive decay of 222Rn are considered. Meanwhile, river runoff was gauged to determine the exchange rates between surface water and groundwater. The result shows that 222Rn isotope can be used as a good environmental tracer with high sensitivity for the interaction between surface water and groundwater, especially in the fractured aquifer system, karst aquifer system and discharge basins.  相似文献   

6.
This study was conducted primarily to measure and map radon activity concentration in soil gas and to understand the effect of geology and lithology and meteorology on radon concentration. Portable radon meter has been used for the measurement of soil gas radon at 30 different locations around Uro and Korn area in eastern Nuba Mountain South Kordofan State. The results indicate that the activity concentrations of 222Rn in soil gas fall within the range of 20–1,359 Bq/m3 with geometric mean of 102.80 Bq/cm3. The obtained data show that samples around Uro have anomaly of 222Rn concentrations than the sample around Korn. The reason could be attributed to differences in the geological structure, lithology and climate parameters. GIS predicative map has shown that the elevated levels of radon concentration were measured in North study area. Upon comparing the results with global data, it was found that the obtained values are far below the reported range of India, Slovenia, Portugal and Syria. However, the range of 222Rn concentrations in the soil observed in this study is significantly high relative to similar data reported from Libya. The regression analysis has shown that no correlation was noted between radon concentrations, climatic parameters and trace element.  相似文献   

7.
Published reports show that 222Rn contents of soil gas can increase under snow-covered or frozen soils. By utilizing these observations and results of field tests described here, it can be stated that U prospecting with 222Rn in frozen terrain is practicable.Rn profiles in frozen and snow-covered soils over U mineralization in the Bancroft area of Ontario outlined known radioactive zones more clearly than did scintillometer profiles.Tests in Gatineau Park, Quebec, in the proximity of a radioactive pegmatite dike showed that lake ice acts as a restrictive barrier to Rn movement from lake waters beneath. Water samples, collected and allowed to freeze in plastic bottles, retained dissolved Rn quite effectively thus permitting sample collection and storage under the most severe winter conditions. Rn sampling of through-ice lake waters is therefore a feasible prospecting tool.Samples of spring run-off (snow-melt) waters and slushy snow collected from within a known weakly radioactive zone near South March, Ontario, were shown to contain less Rn than found in the same stream waters in the summer. No pronounced Rn degassing event of frozen soils was apparent early in the spring thaw in percolating run-off waters draining from the zone. The usefulness of spring thaw hydrogeochemistry using Rn is discussed.  相似文献   

8.
The combined use of geophysical and soil gas composition exploration methods allows to rapidly obtain at relative low cost information that might be related to seismic activity conditions. In this study, we carried out geochemical soil gas sampling (222Rn, 220Rn and CO2), electrical resistivity tomography and seismic refraction profiles in two selected zones near the town of Amer in the Spanish Pyrenees, where the presence of recent fractures is evident in the field. Data analysis clearly reveals anomalous values for each gas at specific positions along the electrical imaging transects. Geomorphologic and hydrogeologic data and the integration of geophysical data and soil gas measurements indicate that: (1) endogene gases radon (222Rn) and carbon dioxide (CO2) are released from the meta-sedimentary basement rocks across the main fractured zones with higher permeability values, while lower Cenozoic detrital sedimentary formations act as an impervious boundary; (2) sites with highest radon concentrations (52?kBq?m?3) coincide with the zones in the Amer fault showing more recent geomorphic evidence of activity, and more specifically with those areas covered by thinner surficial formations; (3) the lowest 222Rn values (0.2?C0.4?kBq?m?3) were recorded just on the master active fault plane. This pattern could be explained by a dilution effect resulting from high rates of soil CO2 efflux (267?g?m?2?day?1); (4) soil thoron (220Rn) activity is maximum (143?kBq?m?3) in areas with high surficial fracturing; (5) groundwater pumping may cause important distortions in the natural flow dynamics and in the measured concentrations of gases. The agreement between the different data (geochemical, geophysical, and hydrogeological) and field observations (geology and geomorphology) leads us to propose a preliminary tectonic-gravitational model for the study area.  相似文献   

9.
Soil radon (222Rn) has been monitored during winter months under cool-temperate deciduous stands of different surface geology in Tomakomai and in Sapporo, Hokkaido, Japan. Radon level was lower in Tomakomai of immature soil of porous volcanic ash emitted from an active volcano (Mt. Tarumae), compared with those in Sapporo of alluvial sediments. In Tomakomai, mean value of the 222Rn activity concentration was higher in winter (570 Bq m?3) than in summer (350 Bq m?3) at a depth of 1 m, which is consistent with the results in cold and dry winter reported in the literature. In contrast, soil radon decreasing with decreasing soil temperature from mid-September (5.0 kBq m?3) remained low (2.6 kBq m?3) under persistent snow in Sapporo, which had already been observed in the same location. Measurements of the activity concentrations of 222Rn in snow and in snow air as well as in soil air indicate that the small amount of 222Rn is released from the ground surface to the overlying snowpack with a 222Rn flux density of 0.4 mBq m?2 s?1 under thick snow cover in Sapporo.  相似文献   

10.
Depth-discrete tracing of residual dense non-aqueous phase liquid (DNAPL) sources in the subsurface is of great importance in making decisions related to contaminated groundwater remediation. Temporal variations in the natural tracer 222Rn and contaminant concentrations in groundwater contaminated with multiple chlorinated contaminants, such as trichloroethene, carbon tetrachloride, and chloroform, were examined to trace residual multiple DNAPL contaminants at an industrial complex in Wonju, Korea. The 222Rn activities and multiple DNAPL concentrations in the groundwater fluctuated irregularly according to the groundwater recharge. The natural tracer 222Rn in groundwater present in the soil layer, originating from the underlying crystalline biotite granite, had a wide range from 29,000 to 179,000 Bq/m3, and total concentrations of chlorinated solvents ranged from 0.06 to 17.77 mg/l, indicating the ambiguous results of 222Rn for tracing the residual DNAPL sources. In this paper, a method is presented to locate zones with a high probability of containing depth-discrete residual multiple DNAPL sources using 222Rn and considering relative contaminant concentrations. The results demonstrate that the combination of the 222Rn activities as a natural tracer and the relative contaminant concentrations is able to be used as a useful tool for tracing residual DNAPLs.  相似文献   

11.
《Applied Geochemistry》1997,12(2):213-224
In March 1994, soil gases were sampled in the area of Vulcano Porto, on the island of Vulcano, using a grid of about 200 points/km2. Analysed gases were CO2, He and222Rn and, over a smaller area, H2S. Some of the samples were also analysed for the isotope composition of CO2C. Three anomalous CO2 degassing areas were identified: Grotta dei Palizzi, the area near the Telephone Exchange, and the area near the beach fumaroles. The behaviour of He and222Rn is different in these 3 areas. The concentration of He is much lower than that of atmospheric He (down to −3950 ppb) in the isthmus, and only in the area near Grotta dei Palizzi does it have values significantly higher than atmospheric ones (up to 1900 ppb). The activity of222Rn, always significantly positively related to CO2 concentrations, peaked in the 2 fumarole areas (isthmus, Telephone Exchange).  相似文献   

12.
Soil–gas measurements of different gas species were performed in two distinct areas of the Corinth Gulf Rift (Greece): the Aigion-Neos Erineos-Lambiri (ANEL) fault zone and the Rion-Patras fault zone. Both zones lie in one of the most seismically active areas of the Euro-Mediterranean region, where a fast-opening continental rift is located. In particular, the geochemical investigations were focused on fault segments and fracture systems previously inferred by geomorphological, lithological and structural studies.In this work the applicability of soil–gas geochemistry surveys for the exploration of buried/hidden faults was tested by using various statistical methods. Moreover, a comprehensive geostatistical treatment of the collected data provided new insights into the control exerted by active structures on deep-seated gas migration towards the surface. In both investigated areas, the highest 222Rn and CO2 concentration peaks correspond with zones where the interaction among fracture and fault segments was inferred by structural and morphological methods. This indicates a clear correlation between the shape and orientation of the anomalies and the different attitude and kinematic behavior of the faults recognized in the two areas. Furthermore, obtained results show that gases migrate preferentially through zones of brittle deformation by advective processes, as suggested by the relatively high rate of migration needed to obtain anomalies of short-lived 222Rn in the soil pores.  相似文献   

13.
《Applied Geochemistry》2006,21(6):1064-1072
Atmospheric 222Rn concentrations were determined over a 10a period, which included the date of the Kobe, Japan earthquake, on January 17th 1995. It was found that the seismically related 222Rn anomaly was higher than the 99% confidence limits for the residual value of atmospheric 222Rn which had been observed 2 months before. The residual 222Rn concentration, in which residual values of the daily minimum are the difference between each normal 222Rn concentration (calculated from January 1984 to December 1993) and the daily minimum 222Rn concentration (January 1994 to January 1995), was calculated by applying the exponential smoothing method to the residual values for each day. It was found that the fluctuations of the residual values can be fitted very well to a log-periodic oscillation model. The real residual values stopped increasing at 1994.999 (December 31st 1994), which corresponds with the critical point (tc) of best fit model. This anomalous 222Rn variation can be seen as the result of local stresses, not primary stresses which directly lead to the Kobe earthquake. On the other hand, when the critical exponent (z) and the radial frequency (ω) of the model were simultaneously fixed 0.2 ⩽ z ⩽ 0.6 and 6 ⩽ ω ⩽ 12, tc (critical point) was between January 13th 1995 and January 27th 1995. The Kobe earthquake occurrence date (January 17th 1995) is within this range. Therefore this anomalous 222Rn variation can also be seen as the result of primary stresses which possibly led to the Kobe earthquake. There is a distinct possibility that similar statistical oscillations will be detected in other measurements such as microseismicity, tectonic strain, fluctuation in the ground level, or changes in groundwater elevations and composition.  相似文献   

14.
Statistical analysis of the radon-222 potential of rocks in Virginia,U.S.A.   总被引：1，自引：0，他引：1  
More than 3,200 indoor radon-222 (222Rn) measurements were made seasonally in an area of about 1,000 square kilometers of the Coastal Plain and Piedmont physiographic provinces in Virginia, U.S.A. Results of these measurements indicate that some geological units are associated, on the average, with twice as much indoor222Rn as other geological units, and that indoor222Rn varies seasonally. The Kruskal-Wallis test was used to test whether indoor222Rn concentrations for data gathered over the winter and summer seasons differ significantly by rock unit. The tests concluded that indoor222Rn concentrations for different rock units were not equal at the 5-percent significance level. The rocks associated with the highest median indoor222Rn concentration are specific rocks in the Mesozoic Culpeper basin, including shale and siltstone units with Jurassic diabase intrusives, and mica schists in the Piedmont physiographic province. The pre-Triassic Peters Creek Schist has the highest ranking in terms of indoor222Rn concentration. The rocks associated with the lowest indoor222Rn concentrations include coastal plain sediments, the Occoquan Granite, Falls Church Tonalite, Piney Branch Mafic and Ultramafic complex, and unnamed mafic and ultramafic inclusions, respectively. The rocks have been ranked according to observed222Rn concentration by transforming the average rank of indoor222Rn concentrations to z scores.  相似文献   

15.
In this study, natural (222Rn) and fluorescent (uranin) tracers were used to investigate the interactions between surface and subsurface waters in a small hydrographical basin located in the southeast region of Brazil. Levels of 222Rn were measured in 117 water samples with the use of an alpha solid-state detector. After the identification of the probable discharge sections along the stream, a measurement of the natural flows, upstream and downstream of these sections, was done with the use of a fluorimeter and fluorescent tracers. Also, scanning was done to verify a correlation between the natural gamma radiation and the 222Rn in the areas where its activity was higher. The results showed some sections where the 222Rn activity is more significant and contributed to the growth of the flows along the stream. It was possible to confirm a correlation between the discharge sections and the natural gamma radiation, what can be used as a preliminary approach to finding these sections in scenarios similar to the one studied here.  相似文献   

16.
Urban soil research has invoked great interest in recent years.Previous studies were mainly focused on urban soil physics and chemistry,and soil geography to constrain the source,distribution,transport and deposition of pollutants such as heavy metals and health-hazardous organic matter,bu t litte has been done on soil microbiology.In this paper,the authors reported the variation of microbial features in urban soils compared with those from adjacent rual areas.The results show great changes in basal respiration rates microbial biomass and ecophysiological parameters have taken place in urban environment because of the anthropogenic stress, thus activating the microorganisms.As a result,much more energy,carbon is consumed at a low utilization efficiency.So microbial biosensors can be used to indicate urban environmental pollution effectively.  相似文献   

17.
222Rn was used to assess river–groundwater interactions within Castel di Sangro alluvial aquifer (Italy). The effectiveness of results obtained through this indicator was verified by also analyzing δ18O, major ions and temperature in both surface and groundwater, and carrying out piezometric head monitoring and discharge measurements. Hydrogeological investigations suggested that the river infiltrates into the aquifer in the south-eastern aquifer portion, while groundwater discharges into the river in the north-eastern portion. The latter phenomenon is supported by 222Rn data. Nevertheless, flow-through conditions cause the modelled discharge along this river reach, estimated by 222Rn data in a degassing-corrected two-component mixing model, to be greater than the measured discharge. Concerning river infiltration into the aquifer, δ18O, major ions and temperature data show that the river contribution is negligible in terms of aquifer recharge. Thus, the observed increase in 222Rn concentration in that portion of the aquifer is due to the enrichment process caused by infiltration of rainwater (222Rn free) which flows from the local divide area. Hence, in the study site, the use of only 222Rn to predict river–groundwater interactions causes some estimation inaccuracies and it must be coupled with other hydrochemical and hydrogeological parameters to gain a thorough understanding of such interactions.  相似文献   

18.
Heavy metals distribution in agricultural topsoils in urban area   总被引：24，自引：0，他引：24  
Intensive urbanisation of the Croatian capital of Zagreb has led to a situation where very good agricultural soils, developed mostly on Pleistocene eolian sediments and alluvial and proluvian Holocene sediments are entrapped within urban and suburban areas. Therefore the influence of urban and industrialised environments on the accumulation of metals in agricultural topsoils has been investigated. On an area of 860 km2 of the wider Zagreb region, 331 samples were taken according to a regular 1ǵ km square mesh. Samples were dissolved in aqua regia and analysed for Cd, Cu, Fe, Mn, Ni, Pb and Zn with flame atomic aqua regia absorption spectroscopy. The following concentration ranges have been determined: Cd 0.25-3.85 mg kg-1 (average 0.66 mg kg-1), Cu 4.30-183 mg kg-1 (average 20.8 mg kg-1), Fe 5.8-51.8 g kg-1 (average 27 g kg-1), Mn 79.2-1282 mg kg-1 (average 613 mg kg-1), Ni 0.70-282 mg kg-1 (average 49.5 mg kg-1), Pb 1.50-139 mg kg-1 (average 25.9 mg kg-1), and Zn 15.2-277 mg kg-1 (average 77.9 mg kg-1). Visualisation of the spatial data is made by the aid of GIS, and selected maps of the heavy metal concentrations in topsoils are displayed. Statistical multivariate analysis was carried out for quantitative study and data were processed by means of R-mode factor analysis, applying the varimax-raw rotational technique. F1, which grouped Cd, Pb, Cu, Zn and partially Ni, is characterized as a factor with strongly scattered anthropogenic influence. The elements in F2, Fe, Mn and partially Ni are mainly of geogenic, i.e. pedogenic, origin. The variations in concentrations of the investigated elements are thus of both natural and anthropogenic origins. The variations in the main soil constituents, particularly Fe and Mn, are determined primarily by the composition of different regolithic substrates of the fluvial origin in recent pedogenesis. High concentrations of nickel are also related to morphogenetic characteristics of the wider region, primarily basic and ultrabasic magmatic rocks of the surrounding mountain range. It is, however, assumed that the anomalous nickel concentrations in the vicinity of the highway and the airport are of anthropogenic origin, i.e. caused by fuel combustion. Copper is characterized by strongly scattered anthropogenic influence, which is related particularly to uncontrolled solid waste disposals or discharges of liquid waste from households or agricultural enterprises. With Zn, Pb and Cd, there are two possible ways of diffuse pollution. The Sava River, which drains the area and feeds the abundant Quaternary aquifer spreading below the major part of the investigated agricultural areas, has been exposed to intensive pollution by mining, industry and cities in the recent history. The part of the area with the highest determined concentrations of Zn, Pb and Cd was repeatedly flooded as recently as the previous decade; therefore, the recent sedimentation of the river deposits exposed to pollution is a very probable cause of the accumulation of metals in this until recently inundation area. The other way is atmospheric deposition of particles from urban sources (industrial emission, traffic, waste disposals, heating plants, etc.). In addition to agricultural enterprises, several economically important, but ecologically risky, facilities are situated in the vicinity of the water-protection area. The area is intersected by a very busy ring road, while a marshalling yard, the city dump, pharmaceutical and chemical industry, the district-heating plant and the airport are all located in close proximity. The geochemical maps show a clear relationship between human activities and metal concentration gradients.  相似文献   

19.
Controls governing the production of 4He and 222Rn in the solid phase as well as parameters and processes contributing to their transport into the pore fluid are discussed. 222Rn activity is used to quantify the uranium sources for 4He and the result is a simplified pore-fluid age equation which is virtually independent of the porosity, the water/rock ratio, the rock density and the uranium concentration, but does require a Th/U estimate. The crucial parameter is the ratio of the release factors for the two species, /GLRn//GLHe, which is discussed in terms of three possible release mechanisms: (1) recoil; (2) recoil followed by diffusion; and (3) weathering release of accumulated 4He. It was found that /GLRn//GLHe can vary over several orders of magnitude, but can be expressed in terms of the effective grain size r, and the diffusive half-length for 222Rn decay, re.4He measurements are used to “date” gases from known gas fields and the agreement with the assumed source-rock age is good. Application of 4He/ 222Rn measurements to continental freshwater springs indicates that the weathering release of accumulated 4He dominates the input and results in a large overestimate of groundwater age. Measurement in the Lardarello geothermal field indicates that the 4He/222Rn method can indicate relative transport direction. Other possible applications in various geochemical fields are suggested.  相似文献   

20.
Controls governing the production of 4He and 222Rn in the solid phase as well as parameters and processes contributing to their transport into the pore fluid are discussed. 222Rn activity is used to quantify the uranium sources for 4He and the result is a simplified pore-fluid age equation which is virtually independent of the porosity, the water/rock ratio, the rock density and the uranium concentration, but does require a Th/U estimate. The crucial parameter is the ratio of the release factors for the two species, /GLRn//GLHe, which is discussed in terms of three possible release mechanisms: (1) recoil; (2) recoil followed by diffusion; and (3) weathering release of accumulated 4He. It was found that /GLRn//GLHe can vary over several orders of magnitude, but can be expressed in terms of the effective grain size r, and the diffusive half-length for 222Rn decay, re.4He measurements are used to “date” gases from known gas fields and the agreement with the assumed source-rock age is good. Application of 4He/ 222Rn measurements to continental freshwater springs indicates that the weathering release of accumulated 4He dominates the input and results in a large overestimate of groundwater age. Measurement in the Lardarello geothermal field indicates that the 4He/222Rn method can indicate relative transport direction. Other possible applications in various geochemical fields are suggested.  相似文献   

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