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1.
In the Long Valley caldera, where seismicity has continued essentially uninterrupted since mid-1980 and uplift is documented, samples of water from hot, warm, and cold springs have been collected since September, 1982, and their222Rn concentrations analyzed. Concurrently, rocks encompassing the hydrologic systems feeding the springs were analyzed for their radioelement contents, because their uranium is the ultimate source of the222Rn in the water.The222Rn concentration in the springs varies inversely with their temperature and specific conductance. High concentrations (1500 to 2500 picocuries per liter) occur in dilute cold springs on the margins of the caldera, while low contents (12 to 25 pCi/l) occur in hot to boiling springs. Springwater radon concentrations also correlate slightly with the uranium content of the encompassing rocks.A continuous monitoring system was installed in August, 1983, at a spring issuing from basalt, to provide hourly records of radon concentration. A gamma detector is submerged in a natural pool, and we have observed that the radioactivity measured in this manner is due almost entirely to the222Rn concentration of the water. Initial operation shows diurnal and semidiurnal variations in the222Rn concentration of the springwater that are ascribed to earth tides, suggesting that those variations are responding to small changes in stress in the rocks encompassing the hydrologic system.  相似文献   

2.
Radon in the Earth’s crust or soil matrix is free to move only if its atoms find their way into pores or capillaries of the matrix. 222Rn atoms from solid mineral grains get into air, filling pores through emanation process. Then 222Rn enters into the atmosphere from air-filled pores by exhalation process. The estimation of radon flux from soil surface is an important parameter for determining the source term for radon concentration modeling. In the present investigation, radon fluxes and soil-gas radon concentration have been measured along and around the Main Central Thrust (MCT) in Uttarkashi district of Garhwal Himalaya, India, by using Scintillation Radon Monitor (SRM) and RAD7 devices, respectively. The soil radon gas concentration measured by RAD7 with soil probe at the constant depth was found to vary from 12 ± 3 to 2330 ± 48 Bq·m?3 with geometrical mean value of 302 ± 84 Bq·m?3. Th significance of this work is its usefulness from radiation protection point of view.  相似文献   

3.
Observations carried out systematically at Karymsky volcano have shown that the Rn content in the gases from the summit crater fumaroles and from hot springs at the foot of the volcano increased before and during the 1971 activity of the volcano.  相似文献   

4.
In some volcanic systems, thoron and radon activity and CO2 flux, in soil and fumaroles, show a relationship between (220Rn/222Rn) and CO2 efflux. It is theorized that deep, magmatic sources of gas are characterized by high 222Rn activity and high CO2 efflux, whereas shallow sources are indicated by high 220Rn activity and relatively low CO2 efflux. In this paper we evaluate whether the observed inverse relationship is a true geochemical signal, or potentially an analytical artifact of high CO2 concentrations. We report results from a laboratory experiment using the RAD7 radon detector, known 222Rn (radon) and 220Rn (thoron), and a controllable percentage of CO2 in the carrier gas. Our results show that for every percentage of CO2, the 220Rn reading should be multiplied by 1.019, the 222Rn radon should be multiplied by 1.003 and the 220Rn/222Rn ratio should be multiplied by 1.016 to correct for the presence of the CO2.  相似文献   

5.
Yong Hwa Oh  Guebuem Kim 《水文研究》2016,30(14):2525-2532
Activities of radon (222Rn) in groundwater were continuously monitored in a saline aquifer from September 2010 to July 2011. The activities of 222Rn ranged from 200 to 4300 Bq m?3, with a large seasonal variation. Because the activity of 222Rn in seawater is low, 222Rn in saline groundwater must be produced in the aquifer from radium (226Ra) in rocks and sediments. The 222Rn activities were higher in the warm‐dry seasons (September–November 2010 and April–May 2011) when the saline aquifer was stable. In contrast, the lowest 222Rn activities were observed in the cold‐dry season (December 2010 and January–March 2011), because of the effective exchange between groundwater and seawater. In addition, sudden decreases of 222Rn activities coincided with episodic drops in groundwater temperatures. These results reveal that lower seawater temperature in winter may result in density‐driven seawater intrusion. During the wet season (June–July 2011), 222Rn activities were more clearly affected by semi‐monthly and diurnal tidal pumping, showing higher 222Rn activities during low and spring tides. Such a tidal effect was not clearly observed during the warm‐dry and cold‐dry seasons. This result implies that the residence time of SGD in coastal zones is significantly affected by seasonal changes in driving forces such as tidal pumping and seawater intrusion. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

6.
In earthquake prediction studies, the regional behaviour of accurate 222Rn measurements at a set of sites plays a significant role. Here, measurements are obtained using active and passive radon detector systems in an earthquake-active region of Turkey. Two new methods are proposed to explain the spatial behaviours and the statistical uncertainties in the 222Rn emission measurements along fault lines in relation to earthquake occurrence. The absolute point cumulative semivariogram (APCSV) and perturbation method (PM) help to depict the spatial distribution patterns of 222Rn in addition to the joint effects of the K dr, the radon distribution coefficient, and the perturbation radon distribution coefficient (PRDC). The K dr coefficient assists in identifying the spatial distributional behaviour in 222Rn concentrations and their migration along the Earth’s surface layers. The PRDC considers not only the arithmetic averages but also the variances (or standard deviations) and the correlation coefficients, in addition to the size of the error among the 222Rn measurements. The applications of these methodologies are performed for 13,000 222Rn measurements that are deemed to be sufficient for the characterization of tectonics in the Keban Reservoir along the East Anatolian Fault System (EAFS) in Turkey. The results are evaluated for the ?çme earthquake (M L 5.4, 5.7 km, 23 June 2011), which occurred in the vicinity of the EAFS.  相似文献   

7.
This study aims to evaluate the application of 222Rn in groundwater as a tracer for monitoring CO2 plume migration in a shallow groundwater system, which is important to detect potential CO2 leakage in the carbon capture and storage (CCS) project. For this research, an artificial CO2-infused water injection experiment was performed in a shallow aquifer by monitoring hydrogeochemical parameters, including 222Rn. Radon in groundwater can be a useful tracer because of its sensitivity to sudden changes in subsurface environment. To monitor the CO2 plume migration, the data were analysed based on (a) the influence of mixing processes on the distribution of 222Rn induced by the artificial injection experiment and (b) the influence of a carrier gas role by CO2 on the variation of 222Rn. The spatio-temporal distributions of radon concentrations were successfully explained in association with horizontal and vertical mixing processes by the CO2-infused water injection. Additionally, the mixing ratios of each monitoring well were calculated, quantitatively confirming the influence of these mixing processes on the distribution of radon concentrations. Moreover, one monitoring well showed a high positive relationship between 222Rn and Total dissolved inorganic carbon (TIC) by the carrier gas effect of CO2 through volatilization from the CO2 plume. It indicated the applicability of 222Rn as a sensitive tracer to directly monitor CO2 leakage. When with a little effect of carrier gas, natural 222Rn in groundwater can be used to compute mixing ratio of CO2-infused water indicative of CO2 migration pathways. CO2 carrier gas effect can possibly increase 222Rn concentration in groundwater and, if fully verified with more field tests, will pose a great potential to be used as a natural tracer for CO2.  相似文献   

8.
Discharge in mountain streams may be a mixture of snowmelt, water from surface runoff, and deep return flow through valley bottom alluvia. We used δ18O and δ2H, solute concentrations, and 222Rn to determine water sources of a headwater stream located at the McDonald Creek watershed, Glacier National Park, USA, during summer recession flow period. We analysed minimal water isotope ranges of ?17.6‰ to ?16.5‰ and ?133‰ to ?121‰ for δ18O and δ2H, respectively, potentially due to dominance of snow‐derived water in the stream. Likewise, solute concentrations measured in the stream through the watershed showed minimal variation with little indication of subsurface water input into the stream. However, we observed 222Rn activities in the stream that ranged from 39 to 2646 Bq/m3 with the highest value measured in middle of the watershed associated with channel constriction corresponding to changes in local orientation of underlying rocks. Downstream from this point, 222Rn activity decreased from 581 to 117 Bq/m3 in a series of punctuated steps associated with small rapids and waterfalls that we hypothesized to cause radon degassing with a maximum predicted loss of 427 Bq/m3 along a 400 m distance. Based on mass balance calculations using 222Rn activity values, streamflow, and channel characteristics, we estimated that groundwater contributed between 0.3% and 29% of total flow. Overall, we estimated a 5.9% of groundwater contribution integrated for stream reach measured at McDonald Creek during recession flow period. Finally, a lower mean hyporheic flux of 14 m3/day was estimated compared to the groundwater flux of 70 710 m3/day. These assessments highlight the potential for radon as a conservative tracer that can be used to estimate subsurface water contribution in mountain streams within a complex geologic setting. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

9.
Mapping and characterizing fracturing in a volcanic terrain is facilitated by the analysis of physical and chemical properties of soils. The parameters analyzed include the temperature at shallow depth, the spontaneous potential (SP), and the 4He, 44CO2, and 222Rn contents of soil gases, as measured in situ by mass spectrometry and α counter.This analysis allowed a distinction of deep fissures not accompanied by thermal loss, characterized by a negative SP anomaly and high He levels, and of a hidden fissure with thermal loss, characterized by a positive SP anomaly and high He, Rn, and CO2 levels. This fissure has no visible surface manifestations.This method of analysing the convective thermal transfer is useful when analysing fracturing in volcanic structures to estimate their eruptive potential.  相似文献   

10.
Ground waters from fractured igneous and high-grade sialic metamorphic rocks frequently have elevated activity of dissolved radon (222Rn). A chemically based model is proposed whereby radium (226Ra) from the decay of uranium (238U) diffuses through the primary porosity of the rock to the water-transmitting fracture where it is sorbed on weathering products. Sorption of 226Ra on the fracture surface maintains an activity gradient in the rock matrix, ensuring a continuous supply of 226Ra to fracture surfaces. As a result of the relatively long half-life of 226Ra (1601 years), significant activity can accumulate on fracture surfaces. The proximity of this sorbed 226Ra to the active ground water flow system allows its decay progeny 222Rn to enter directly into the water. Laboratory analyses of primary porosity and diffusion coefficients of the rock matrix, radon emanation, and ion exchange at fracture surfaces are consistent with the requirements of a diffusion/ion-exchange model. A dipole-brine injection/withdrawal experiment conducted between bedrock boreholes in the high-grade metamorphic and granite rocks at the Hubbard Brook Experimental Forest, Grafton County, New Hampshire, United States (42 degrees 56'N, 71 degrees 43'W) shows a large activity of 226Ra exchanged from fracture surfaces by a magnesium brine. The 226Ra activity removed by the exchange process is 34 times greater than that of 238U activity. These observations are consistent with the diffusion/ion-exchange model. Elutriate isotopic ratios of 223Ra/226Ra and 238U/226Ra are also consistent with the proposed chemically based diffusion/ion-exchange model.  相似文献   

11.
A method is presented to evaluate ground water residence time in a zero‐valent iron (ZVI) permeable reactive barrier (PRB) using radon‐222 (222Rn) as a radioactive tracer. Residence time is a useful indicator of PRB hydraulic performance, with application to estimating the volumetric rate of ground water flow through a PRB, identifying flow heterogeneity, and characterizing flow conditions over time as a PRB matures. The tracer method relies on monitoring the decay of naturally occurring aqueous 222Rn as ground water flows through a PRB. Application of the method at a PRB site near Monticello, Utah, shows that after 8 years of operation, residence times in the ZVI range from 80 to 486 h and correlate well with chemical parameters (pH, Ca, SO4, and Fe) that indicate the relative residence time. Residence times in this case study are determined directly from the first‐order decay equation because we show no significant emanation of 222Rn within the PRB and no measurable loss of 222Rn other than by radioactive decay.  相似文献   

12.
Precursory geochemical signatures of radon degassing in the subsurface of the Tenerife Island were observed several months prior to the recent 2004 seismic-volcanic crisis. These premonitory signatures were detected by means of a continuous monitoring of 222Rn and 220Rn activity from a bubbling CO2-rich gas spot located at 2.850 m depth inside a horizontal gallery for groundwater exploitation at Tenerife. Multivariate Regression Analysis (MRA) on time series of the radon activity was applied to eliminate the radon activity fluctuation due to external variables such as barometric pressure, temperature and relative humidity as well as power supply. Material Failure Forecast Method (FFM) was successfully applied to forecast the anomalous seismicity registered in Tenerife Island in 2004. The changes in the 222Rn/220Rn ratio observed after the period of anomalous seismicity might suggest a higher gas flow rate and/or changes in the vertical permeability induced by seismic activity.  相似文献   

13.
Studies on the 222Rn content of groundwater were conducted to obtain knowledge of its distribution in the geosphere just below ground surface and below the depth of 100 m in the Osaka Group (Plio-Pleistocene). Samples analyzed from ten bore holes within 10 m depth below land surface showed that a sandy layer contained groundwater with consistent radon concentrations except for a few locations where the variations in the water level were large due to precipitation and/or the water level was within 2 m of ground surface. The average 222Rn concentration in groundwater within 10 m of land surface was found to be approximately equal to 13 to 35 of the highest concentration found in groundwater from a well penetrating 100–200 m (420 pCi/l?1).  相似文献   

14.
Hydrothermal waters collected by “Alvin” from the Galapagos Spreading Center are enriched in222Rn by factors of 50–200 over bottom waters. The226Ra in the same samples, however, is enriched by less than a factor of four over bottom waters. Enrichments of222Rn result primarily from α-recoil from rock surfaces while226Ra enrichments are dominantly produced by high-temperature alteration of cooling ridge volcanics. The abundances of both nuclides exhibit positive correlations with temperature. The data extrapolate to bottom water temperatures and compositions, demonstrating the importance of seawater mixing. Different vents, however, have different mixing lines, and vents with high222Rn have low226Ra. We propose these patterns result from variations in the extent of low-temperature crustal interaction with the hydrothermal fluids. Low-temperature crustal waters can maintain high steady state222Rn contents due to the α-recoil additions to the fluids. The226Ra, however, is strongly adsorbed at low-temperatures resulting in low concentrations of this nuclide in low-temperature crustal waters. Thus, physical mixing of a crustal water component with hydrothermal waters or variable crustal path lengths of the hydrothermal fluids can account for the variable mixing lines and222Rn/226Ra values of the hot springs.The222Rn/226Ra value appears to be a sensitive indicator of low-temperature crustal interaction. Values > 100 have experienced extensive crustal interaction and are indicative of diffuse hydrothermal flow. Values between 1 and 10 are indicative of primary hydrothermal fluids which have not experienced significant interaction with the crust. Values of222Rn/226Ra between 103 and 104 are indicative of interaction of the hydrothermal fluids with sediments. Such values are observed in water samples from the Galapagos hydrothermal mounds.  相似文献   

15.
Groundwater discharge flux into rivers (riverine groundwater discharge or RGD) is essential information for the conservation and management of aquatic ecosystems and resources. One way to estimate area-integrated groundwater discharge into surface water bodies is to measure the concentration of a groundwater tracer within the water body. We assessed groundwater discharge using 222Rn, a tracer common in many surface water studies, through field measurements, surface water 222Rn mass balance model, and groundwater flow simulation, for the seldom studied but ubiquitous setting of a flooding river corridor. The investigation was conducted at the dam-regulated Lower Colorado River (LCR) in Austin, Texas, USA. We found that 222Rn in both the river water and groundwater in the river bank changed synchronously over a 12-hour flood cycle. A 222Rn mass balance model allowed for estimation of groundwater discharge into a 500-m long reach of the LCR over the flood. The groundwater discharge ranged between negative values (indicating recharge) to 1570 m3/h; groundwater discharge from groundwater flow simulations corroborated these estimates. However, for the dynamic groundwater discharge estimated by the 222Rn box model, assuming whether the groundwater 222Rn endmember was constant or dynamic led to notably different results. The resultant groundwater discharge estimates are also highly sensitive to river 222Rn values. We thus recommend that when using this approach to accurately characterize dynamic groundwater discharge, the 222Rn in near-stream groundwater should be monitored at the same frequency as river 222Rn. If this is not possible, the 222Rn method can still provide reasonable but approximate groundwater discharge given background information on surface water-groundwater exchange time scales.  相似文献   

16.
The migration mechanisms of endogenous gases in the geosphere are defined in relation to the fluid-rock conditions and analyzed by basic transport equations. Upon examining the geological factors that influence the physical parameters in the equations in porous and fracture media, and considering the widespread high-permeability of deep subsurface rocks, in terms of fracture aperture, (orders of 10−2 to 101 mm at depths of thousands meters, as suggested by recent crustal surveys) advection of carrier gases, in its several forms (gas-phase flow, water displacement by gas, gas slugs and bubbles) seems to represent a major migration process. Accordingly, in contrast with early views, the role of gas diffusion and water advection in the transport of endogenous gas to the Earth surface should be strongly minimized in many contexts. In a wide range of geological settings, carrier gases (CO2, CH4) may assume a dominant role in controlling transport and redistribution toward the Earth’s surface of trace gases (Rn, He). Bubble movement in fissured rocks seems to be an effective way of rapid (gas velocities in the order of 100 to 103 m per day) and long-distance gas migration. The evolution from bubble regimes to continuous phase flow and vice versa, as gas pressure and fracture width change, is the most suitable mechanism towards determining the surface geochemical processes of seismo-tectonic, environmental and geo-exploration relevance. The transport effectiveness of trace gases by a carrier gas has yet to be studied in quantitative terms. It is already clear, however, that further studies on the distribution and behavior of trace gases approaching the Earth’s surface may not be meaningful unless accompanied by carrier gas dynamics analyses.  相似文献   

17.
Given that the concentration of 222Rn in groundwater is much higher than that in surface water and that its radioactive half‐life (3.83 d) is short, 222Rn is an effective tracer of groundwater–surface water interactions. In this study, a new mass balance method is presented, which can be used to estimate specific groundwater–surface water interactions within a river reach. Three possible situations of interaction between groundwater and surface water are considered, and equations based on the mass conservation of 222Rn are formulated for judging specific groundwater–surface water interaction processes and for calculating water flux. A case study was conducted for the Nalenggele River, Northwest China, to demonstrate the usefulness of this method. Samples of river water and groundwater containing 222Rn were collected from the study area to estimate the interactions between groundwater and surface water. The amount of water exchanged during these interactions was estimated and the results show that transformations between groundwater and surface water are frequent along the stream. The 222Rn mass balance method is highly sensitive for studying such interactions, even in areas for which conventional hydrologic data are sparse. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

18.
Radon (222Rn) concentration in geothermal waters and CO2-rich cold springwaters collected weekly in duplicate samples from four stations in northern Taiwan were measured from July 1980 to December 1983. Seven spike-like radon anomalies (increases of 2 to 3 times the standard deviation above the mean) were observed at three stations. Following every anomaly except one, an earthquake ofM L above 4.6 occurred within 4 to 51 days, at an epicentral distance 14 to 45 km, and at a focal depth of less than 10 km. The distribution of the earthquakes preceded by radon anomalies is skewed in certain directions from the radon stations; the radon stations seem to be insensitive to earthquakes occurring in the other directions. At the fourth station, near a volcanic area, much gas (mainly CO2) is discharged from the well, together with hot water. A very high concentration of radon was detected in the discharged gas; therefore trapping of gas in the water can result in anomalously high radon contents. According to limited measurements, the radon concentration in water appears to be undersaturated with respect to that in gas. This suggests that hot water is very susceptible to radon loss, and monitoring of radon in gas is more desirable.  相似文献   

19.
The objective of this study was to investigate whether 222Rn in groundwater can be used as a tracer for light non‐aqueous phase liquid (LNAPL) quantification at a field site treated by dual‐phase LNAPL removal. After the break of a pipeline, 5 ha of soil in the nature reserve Coussouls de Crau in southern France was contaminated by 5100 m3 of crude oil. Part of this oil seeped into the underlying gravel aquifer and formed a floating oil body of about 3.9 ha. The remediation consists of plume management by hydraulic groundwater barriers and LNAPL extraction in the source zone. 222Rn measurements were performed in 21 wells in and outside the source zone during 15 months. In uncontaminated groundwater, the radon activity was relatively constant and remained always >11 Bq/L. The variability of radon activity measurements in wells affected by the pump‐and‐skim system was consistent with the measurements in wells that were not impacted by the system. The mean activities in wells in the source zone were, in general, significantly lower than in wells upgradient of the source zone, owing to partitioning of 222Rn into the oil phase. The lowest activities were found in zones with high non‐aqueous phase liquid (NAPL) recovery. LNAPL saturations around each recovery well were furthermore calculated during a period of high groundwater level, using a laboratory‐determined crude oil–water partitioning coefficient of 38.5 ± 2.9. This yielded an estimated volume of residual crude oil of 309 ± 93 m3 below the capillary fringe. We find that 222Rn is a useful and cheap groundwater tracer for finding zones of good LNAPL recovery in an aquifer treated by dual‐phase LNAPL removal, but that quantification of NAPL saturation using Rn is highly uncertain.  相似文献   

20.
The222Rn content of a subterranean fluid depends on the physico-chemical nature of the media through which the fluid passes and on the time spent by the fluid in the various geological formations encountered. Consequently,222Rn measurement in a geofluid gives a clue to the subsurface transport conditions of this geofluid. Simple models are proposed for various types of buried structures connected with the surface by a geothermal well; they all lead to the222Rn concentration expressed as a function of the flow-rate of the carrier fluid. In real systems, the variations of this concentration with flow-rate would allow the type of structure feading the well to be determined, and, in propitious circumstances, the volume of the possible reservoir to be estimated.  相似文献   

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