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1.
Both radioxenon and radioiodine are possible indicators for a nuclear explosion. Therefore, they will be, together with other relevant radionuclides, globally monitored by the International Monitoring System in order to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty once the treaty has entered into force. This paper studies the temporal development of radioxenon and radioiodine activities with two different assumptions on fractionation during the release from an underground test. In the first case, only the noble gases are released, in the second case, radioiodine is released as well while the precursors remain underground. For the second case, the simulated curves of activity ratios are compared to prompt and delayed atmospheric radioactivity releases from underground nuclear tests at Nevada as a function of the time of atmospheric air sampling for concentration measurements of 135I, 133I and 131I. In addition, the effect of both fractionation cases on the isotopic activity ratios is shown in the four-isotope-plot (with 135Xe, 133mXe, 133Xe and 131mXe) that can be utilized for distinguishing nuclear explosion sources from civilian releases.  相似文献   

2.
A global monitoring system for atmospheric xenon radioactivity is being established as part of the International Monitoring System that will verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) once the treaty has entered into force. This paper studies isotopic activity ratios to support the interpretation of observed atmospheric concentrations of 135Xe, 133mXe, 133Xe and 131mXe. The goal is to distinguish nuclear explosion sources from civilian releases. Simulations of nuclear explosions and reactors, empirical data for both test and reactor releases as well as observations by measurement stations of the International Noble Gas Experiment (INGE) are used to provide a proof of concept for the isotopic ratio based method for source discrimination.  相似文献   

3.
The isotopic composition of neon was measured for seventeen samples of submarine basalt glass from the Mid-Atlantic Ridge between 54° and 73°N. They include the Reykjanes, Kolbeinsey, and Mohns Ridge segments. Neon isotopic anomalies, relative to the atmospheric ratios, exist in both20Ne/22Ne and21Ne/22Ne. A maximum excess20Ne of 7% was measured in two samples from the Reykjanes Ridge. Samples with lower20Ne excesses (six samples with δ20Ne between 2 and 4%) from all three ridge segments, appear to result from mixing of a mantle component with a δ20Ne of 7% and atmospheric neon.21Ne/22Ne ratios are up to 8% above the atmospheric value, with no apparent correlation with the20Ne excesses. The anomalies in20Ne/22Ne are difficult to explain by mass fractionation of an atmospheric reservoir since several of the samples have δ20Ne values greater than could be produced by single-stage fractionation. Most likely, the excess21Ne results from nuclear reactions in the mantle source, although there is no definite correlation between the δ21Ne or the excess21Ne (cm3 STP/g) and the uranium concentration. Large variations in the observed4He/20Ne ratio (40–12,000) remain unexplained at this time.  相似文献   

4.
The Comprehensive Nuclear Test Ban Treaty allows for Multi-Spectral and Infrared Imaging from an aircraft and on the ground to help reduce the search area for an underground nuclear explosion from the initial 1,000 km2. Satellite data, primarily from Landsat, have been used as a surrogate for aircraft data to investigate whether there are any multi-spectral features associated with the nuclear tests in Pakistan, India or North Korea. It is shown that there are multi-spectral observables on the ground that can be associated with the nominal surface ground zero for at least some of these explosions, and that these are likely to be found by measurements allowed by the treaty.  相似文献   

5.
The distribution and isotopic composition of helium has been measured in a suite of well-characterized one-carat diamonds from the Orapa kimberlite, Botswana. Crushing of the diamonds in vacuo indicates that most of the helium is contained by the matrix (generally greater than 90%), rather than by the inclusions. Step-heating experiments, performed on inclusion-free fragments remaining after crushing, indicate that the3He/4He ratio is variablewithin individual diamonds. The fragments, as small as 10 mg, were heated in two timed steps, both at 2000°C. In every case, lower3He/4He ratios are observed in the first graphitization step (0.05–3 × atmospheric), while the last heating step releases helium with systematically higher3He/4He ratio (30–80 × atmospheric). We suggest that this internal isotopic variability is the result of stepwise graphitization: the first heating step initiates graphitization, which nucleates around defects, and the second heating step graphitizes the relatively defect-free regions of the diamond. The3He/4He ratio measured, using the partial graphitization technique, differs by up to a factor of 100 within a single specimen. The inclusion-free fragments release small quantities of helium below 2000°C, which suggests that helium release is obtained only by graphitization. The3He contents of the monocrystalline diamonds are relatively constant (at 3 × 10−13 cm3 STP/gram) and indicate that most of the isotopic variability is due to radiogenic4He. The variations in4He content are either related to zoning of Th and U in the diamonds (i.e., in-situ decay), to zoning of inherited4He, or to implantation of α-particles from a Th and U rich environment (i.e., kimberlite). Because the Orapa diamonds were mined from roughly 40 m depth in the kimberlite, spallation reactions from cosmic ray interactions are not a significant source of3He. However, calculations based on the age of the kimberlite (90 m.y.) and reasonable Th and U abundances suggest that most of the3He in the Orapa diamonds could be produced by6Li(n, α)T in the diamond. Although this may not be true of all diamonds, nuclear reactions in the crust and mantle (including spallation reactions at the surface) can explain many of the high3He/4He ratios previously reported for diamonds.  相似文献   

6.
We performed a complete noble gas study on eight different josephinites and one oregonite. The 4He/3He ratios range between 100,000 and 330,000 and are probably due to a combination of a MORB He-component from the Josephinite Peridotite massif, where these nickel-iron specimens are found, and either atmospheric He or radiogenic He from the underlying continental or subcontinental basement. The 40Ar/36Ar ratios of 302 to 381 are slightly higher than the ratio of air-argon. The neon, krypton and xenon isotopic ratios are identical to the corresponding air ratios. We cannot confirm large3He and21Ne excesses published earlier. The observed noble gas isotopic signatures are in agreement with a formation of josephinites near the surface. The data do not favour a deep mantle origin or a formation at the mantle-core boundary as proposed before.  相似文献   

7.
The announced October 2006 nuclear test explosion in the Democratic People’s Republic of Korea (DPRK) has been the first real test regarding the technical capabilities of the verification system built up by the Vienna-based Provisional Technical Secretariat (PTS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) to detect and locate a nuclear test event. This paper enhances the resolution of the DPRK events’ xenon source reconstruction published by Saey et al. (2007, “A long distance measurement of radioxenon in Yellowknife, Canada, in late October 2006”, GRL, Vol. 34, L20802) that was based solely on radio-xenon measurements taken at the remote radionuclide station in Yellowknife, Canada by involving additional measurements taken by a mobile noble gas system deployed quite close to the event location in the Republic of Korea (ROK). Moreover the horizontal resolution of the forward and backward atmospheric transport modelling methods applied for the source scenario reconstruction has been enhanced appropriately to reflect the considerably shorter source-receptor distances examined in comparison to the previously published source reconstruction. It is shown that the 133Xe measurements in Yellowknife could register 133Xe traces from the nuclear explosion during the first 3 days after the event, while the mobile measurements were rather sensitive to releases during days 2–4 after the explosion. According to the analysis, the most likely source scenario would consist of an initial (possibly up to 21 h delayed) venting of 1 × 10?15 Bq 133Xe during the first 24 h, followed by a two orders of magnitude weaker seepage during the following 3 days. Both measurements corroborate the scenario of a rather rapid venting and soil diffusion of the 133Xe yielded during the explosion. While the Swedish mobile measurements were crucial to enhancement of the reconstruction of the source scenario, given the installation status of the IMS xenon network at the time of the event, a sensitivity analysis revealed that the fully developed network would have been able to detect 133Xe traces from the Korean explosion at a number of stations and allowed for an even better constraint on the release function. The station Ussuriysk, Russia, being in operation in 2006, would have registered 133Xe within 1 day and with a three orders of magnitudes stronger signal compared to the detection at Yellowknife.  相似文献   

8.
D/H ratios of fluid inclusion waters extracted from230Th/234U-dated speleothems that were originally deposited under conditions of isotopic equilibrium should provide a direct estimate of the hydrogen isotopic composition of ancient meteoric waters. We present here D/H ratios for 47 fluid inclusion samples from thirteen speleothems deposited over the past 250,000 years at cave sites in Iowa, West Virginia, Kentucky and Missouri. At each site glacial-age waters are depleted in deuterium relative to those of interglacial age. The average interglacial/glacial shift in the hydrogen isotopic composition of meteoric precipitation over ice-free areas of east-central North America is estimated to be ?12‰. This shift is consistent with the present climatic models and can be explained in terms of the prevailing pattern of atmospheric circulation and an increased ocean-continent temperature gradient during glacial times which more than compensated for the increase in deuterium content of the world ocean.  相似文献   

9.
Cores and coats of five coated diamonds, one from Botswana and four from Zaire, were separately analyzed for their noble gases. Noble gases in the diamonds are essentially of a trapped origin, including radio- and nucleogenic components such as4He, 40Ar, 21Neexcess and excesses in Xe isotopes (129, 131–136). The fairly precise elemental and isotopic abundances allow us to infer the noble gas state in the ancient mantle. 20Ne/22Ne ratios are fairly constant (11.8 ± 0.4), and very close to that of SEP (solar energetic particle)-Ne, but distinctly different from the atmospheric ratio. 21Ne/22Ne ratios range from 0.028 to 0.06, which is attributed to nucleogenic 21Ne from 18O(α, n)21Ne and 24Mg(n, α)21Ne reactions. The difference in 20Ne/22Ne between atmosphere and mantle can be attributed to the hydrodynamic escape of hydrogen from the primitive atmosphere during the very early stage in the Earth's history. 38Ar/36Ar and Kr isotopic ratios are identical to the atmospheric values within 1%. After correction for 238U- or 244Pu-fission Xe, the 131–136Xe abundance ratios are indistinguishable from atmospheric ratios. Lighter Xe isotopes (124–128Xe) are also likely to be atmospheric, but a final conclusion must wait until better data are obtained.In a 136Xe/130Xe−129Xe/130Xe diagram, diamond data lie on the same line as defined for MORB. The observed identical correlation for both diamonds and MORB's appears to suggest that the progenitor of the excess131–136Xe is 244Pu, but not238U, though the direct Xe isotopic measurements was not precies enough to decide unanimously the progenitor.  相似文献   

10.
We examine in this paper the use of helium isotope ratios for the study of hotspot volcanism along age-progressive island volcanic chains. The Hawaiian Islands are the original “high 3He” hotspot, with 3He/4He ratios as high as 32 × the atmospheric ratio; in the Pacific they stand out against the surrounding sea of MORB (rather uniformly 8 × atmospheric) which fills the entire Pacific with the exception of the Macdonald-Mehetia-Samoa axis in the South Pacific. The recent availability of a variety of alkalic and tholeiitic glasses from the U.S. Geological Survey and our own dredge hauls has prompted us to look first at isotopic variability within a single fresh and new volcano which is probably sitting directly atop a mantle plume. Thus we have looked in some detail at the total helium in glass pillow rims, at He in the enclosed vesicles, and at He in the glass itself, in both tholeiitic and alkalic lavas, and also at helium in associated phenocrysts and xenoliths. The measured 3He/4He ratios range from atmospheric to 30 × atmospheric, but we see clear evidence that the highly vesiculated lavas suffer exchange of He between the thin glass walls of vesicles and ambient seawater, so that we observe a post-eruptive isotopic disequilibrium between glass and gas phases. The primary effect is the very large loss of initial He content during eruptive vesiculation, which results in quite large isotopic effects from small additions of ambient He (of the order of 0.02 μcc He per gram of basalt; corresponding to a “water/rock ratio” of 0.5). Phenocrystic He in olivines verifies that the gas-phase He is not affected by vesicularities up to about 5%. Alkali basalt He appears to be independent of vesicularity up to values as high as 35%; this He is somewhat lower in 3He/4He ratio, but matches precisely the associated xenolithic He. However, from the present data we cannot exclude the possibility that diffusive exchange with seawater has affected the He ratio in alkalic vesicles.On the large scale, along the 10% of the Hawaiian chain available for subaerial sampling, we find high 3He/4He ratios (24 × atmospheric) in 5.5 × 106-year-old lavas on Kauai. Maximum values of the ratio so far observed are in the pre-erosional Kula basalts on Maui, confirming the previous results of Kaneoka and Takaoka. Hawaii, where these high values were first observed is now seen to range from MORB ratios at Mauna Loa to only 15 × RA at Kilauea fumaroles. Most xenolithic He so far measured is MORB He, but Loihi xenoliths have high values and are quite different in this respect. Finally, we discuss also the hydrogen and carbon isotope results on Loihi lavas, and show that these elements resemble MORB and appear not to show a distinctive plume signature.  相似文献   

11.
Primordial neon,helium, and hydrogen in oceanic basalts   总被引：3，自引：0，他引：3  
A primordial neon component in neon from Kilauea Volcano and deep-sea tholeiite glass has been identified by the presence of excess20Ne; relative to atmospheric neon the20Ne enrichments are 5.4% in Kilauea neon and about 2.5% in the basalts. The20Ne anomalies are associated with high3He/4He ratios; the ratio in Kilauea helium is 15 times the atmospheric ratio, while mid-ocean ridge basalts from the Atlantic, Pacific, and Red Sea have uniform ratios about 10 times atmospheric. Mantle neon and helium are quite different in isotopic composition from crustal gases, which are highly enriched in radiogenic21Ne and4He. The21Ne/4He ratios in crustal gases are consistent with calculated values based on G. Wetherill's18O (α,n) reaction; the lack of20Ne enrichment in these gases shows that the mantle20Ne anomalies are not radiogenic.21Ne enrichments in Kilauea neon and “high-3He” Pacific tholeiites are much less than in crustal neon, about 2 ± 2% vs. present atmospheric neon, as expected from the much lower4He/Ne ratios.Neon concentrations in two Atlantic tholeiites were found to be only 1–2% of the values obtained by Dymond and Hogan; helium concentrations are slightly greater and our He/Ne ratios are greater by a factor of 150. The large Ne excess relative to solar wind and meteoritic gases is thus not confirmed. Pacific and Atlantic basalts appear to be quite different in He/Ne ratios however, and He and Ne may be inversely correlated. He concentration variations due to diffusive loss can be distinguished from variations due to two-phase partitioning or mantle heterogeneity by the effects on3He/4He ratios. The He isotopic and concentration measurements on “low-3He” basalts are consistent with diffusive loss and dilution of the 3/4 ratio by in-situ radiogenic4He, and may provide a method for dating basalt glasses.Deuterium/hydrogen ratios in Atlantic and Pacific tholeiite glasses are 77% lower than the ratio in seawater. The inverse correlation between deuterium and water content observed by Friedman in erupting Kilauea basalts is consistent with a Rayleigh separation process in which magmatic water is separated from an initial melt with the same D/H ratio as observed in deep-sea tholeiites. The consistency of the D/H ratios in tholeiites containing primordial He and Ne components indicates that these ratios are probably characteristic of primordial or juvenile hydrogen in the mantle.  相似文献   

12.
Fifteen submarine glasses from the East Pacific Rise (CYAMEX), the Kyushu-Palau Ridge (DSDP Leg 59) and the Nauru Basin (DSDP Leg 61) were analysed for noble gas contents and isotopic ratios. Both the East Pacific Rise and Kyushu-Palau Ridge samples showed Ne excess relative to Ar and a monotonic decrease from Xe to Ar when compared with air noble gas abundance. This characteristic noble gas abundance pattern (type 2, classified by Ozima and Alexander) is interpreted to be due to a two-stage degassing from a noble gas reservoir with originally atmospheric abundance. In the Kyushu-Palau Ridge sample, noble gases are nearly ten times more abundant than in the East Pacific Rise samples. This may be attributed to an oceanic crust contamination in the former mantle source.There is no correlation between the He content and that of the other noble gas in the CYAMEX samples. This suggests that He was derived from a larger region, independent from the other noble gases.Except where radiogenic isotopes are involved, all other noble gas isotopic ratios were indistinguishable from air noble gas isotopic ratios. The3He/4He in the East Pacific Rise shows a remarkably uniform ratio of (1.21±0.07)×10?5, while the40Ar/36Ar ranges from 700 to 5600.  相似文献   

13.
In order to understand the role of the subducted lithosphere in producing the geochemical characteristics of arc magmas, major- and trace-element along with Sr- and Nd-isotope compositions have been determined for Quaternary volcanic rocks from the Izu-Bonin intra-oceanic arc. 87Sr/86Sr and 143Nd/144Nd ratios decrease away from the volcanic front of this arc and lie on mixing lines between the assumed isotopic compositions of fluid phases mainly derived from the basalt layer of the subducted lithosphere and upper-mantle materials in the sub-arc wedge. This across-arc variation can be explained through a simple sequence of processes involving initial release of fluid phases from the subducted oceanic crust to produce hydrous peridotite at the base of the mantle wedge. This hydrous peridotite is dragged downward with the slab and releases a second-stage metasomatizing fluid beneath the volcanic arc. The higher concentrations of both Sr and Nd in the fluid beneath the volcanic front than those beneath the back-arc side may be a possible cause of the observed across-arc variation in Sr-Nd isotopic ratios. The difference in compositions of fluid phases is attributed to the different hydrous phases which decompose in the hydrous peridotite layer; amphibole beneath the volcanic front and phlogopite beneath the back-arc side of the volcanic arc. The mineralogically controlled fluid addition may also be responsible for the across-arc variation in Rb/K and Rb/Zr ratios, increasing away from the volcanic front.  相似文献   

14.
36Ar, 84Kr, and 132Xe abundances along with Kr and Xe isotopic compositions are reported for two African shales and samples of chert from the Gunflint Formation in Canada. It is observed that these data and similar abundance data from other terrestrial materials show correlations between 36Ar-84Kr and between 84Kr-132Xe. The elemental ratios defined by all the above data differ significantly from and show greater variations than those measured in carbonaceous chondrites, a well-investigated class of extraterrestrial material. Physical absorption and equilibrium solubility acting on the atmosphere are investigated as explanations for the observations. The Kr and Xe isotopic spectra are also consistent with a mass-dependent incorporation process acting on a reservoir of atmospheric composition.  相似文献   

15.
In an attempt to determine the helium and neon isotopic composition of the lower oceanic crust, we report new noble gas measurements on 11 million year old gabbros from Ocean Drilling Program site 735B in the Indian Ocean. The nine whole rock samples analyzed came from 20 to 500 m depth below the seafloor. Helium contents vary from 3.3×10−10 to 2.5×10−7 ccSTP/g by crushing and from 5.4×10−8 to 2.4×10−7 ccSTP/g by melting. 3He/4He ratios vary between 2.2 and 8.6 Ra by crushing and between 2.9 and 8.2 by melting. The highest R/Ra ratios are similar to the mean mid-ocean ridge basalt (MORB) ratio of 8±1. The lower values are attributed to radiogenic helium from in situ α-particle production during uranium and thorium decay. Neon isotopic ratios are similar to atmospheric ratios, reflecting a significant seawater circulation in the upper 500 m of exposed crust at this site. MORB-like neon, with elevated 20Ne/22Ne and 21Ne/22Ne ratios, was found in some high temperature steps of heating experiments, but with very small anomalies compared to air. These first results from the lower oceanic crust indicate that subducted lower oceanic crust has an atmospheric 20Ne/22Ne ratio. Most of this neon must be removed during the subduction process, if the ocean crust is to be recirculated in the upper mantle, otherwise this atmospheric neon will overwhelm the upper mantle neon budget. Similarly, the high (U+Th)/3He ratio of these crustal gabbros will generate very radiogenic 4He/3He ratios on a 100 Ma time scale, so lower oceanic crust cannot be recycled into either MORB or oceanic island basalt without some form of processing.  相似文献   

16.
During on-site inspections to verify the comprehensive nuclear-test-ban treaty (CTBT), soil gas samples may be taken and analysed for their content of the xenon isotopes 131mXe, 133Xe, 133mXe and 135Xe in order to identify a suspected underground nuclear test. These samples might contain natural radioxenon which is present as a trace gas in the ground. This work analyses the different production mechanisms of natural lithospheric radioxenon to assess theoretically the background concentration under different sampling conditions. The results imply that the equilibrium concentrations of the examined xenon isotopes can be measured in certain rock types using actual CTBTO on-site inspection equipment. Radioxenon production is dominated by spontaneous fission of 238U, resulting in a reactor-like xenon isotopic signature rather than an explosion-like signature.  相似文献   

17.
Detonation gases released by an underground nuclear test include trace amounts of 133Xe and 37Ar. In the context of the Comprehensive Nuclear Test Ban Treaty, On Site Inspection Protocol, such gases released from or sampled at the soil surface could be used to indicate the occurrence of an explosion in violation of the treaty. To better estimate the levels of detectability from an underground nuclear test (UNE), we developed mathematical models to evaluate the processes of 133Xe and 37Ar transport in fractured rock. Two models are developed respectively for representing thermal and isothermal transport. When the thermal process becomes minor under the condition of low temperature and low liquid saturation, the subsurface system is described using an isothermal and single-gas-phase transport model and barometric pumping becomes the major driving force to deliver 133Xe and 37Ar to the ground surface. A thermal test is simulated using a nonisothermal and two-phase transport model. In the model, steam production and bubble expansion are the major processes driving noble gas components to ground surface. After the temperature in the chimney drops below boiling, barometric pumping takes over the role as the major transport process.  相似文献   

18.
This paper analyzes the relationship between bank sediment storage and radionuclide content in six alluvial sites located in different geomorphic contexts along the lower Rh?ne River. The 137Cs, 238Pu, 239+240Pu, 241Am and 210Pb profiles show different patterns, which indicates a differential storage of contaminated sediment in the banks. Three sites record historical nuclear releases in the river and give evidence for long-term retention of particle-reactive long-lived radionuclides. Two sites record only atmospheric global fallout. Only one site, connected to the river groundwater, provides some evidence for desorption of particle-bound contaminants, with a low and constant 137Cs activity profile. The history of the releases from the Marcoule spent-fuel reprocessing plant—the main source of artificial radioactivity—provides a reliable chronology of the last 50?years. Sediment grain size and bank topography are important factors in determining where artificial radionuclides are stored, but these two parameters cannot be used alone to determine variations in high concentrations of radionuclides. The chronology of fluvial geomorphic “metamorphosis” during the twentieth Century, especially after 1960, is also a critical factor affecting the spatial variability in sedimentation rates and artificial radionuclide storage; the timing of channel deepening and bank sedimentary accretion interfere with the chronology of major floods and the short period of low discharge during the height of contamination from nuclear liquid effluents. The reach-scale adjustment described in this paper can contribute to determining what the local history may have been. This result has important implications for river management decisions.  相似文献   

19.
A simple model of mass fractionation may explain the isotopic ratios of rare gases in volcanic materials. Single-stage mass fractionation of atmospheric rare gases predicts an upper limit for20Ne/22Ne of 10.3 and a lower limit for40Ar/36Ar of 280. The rare gas data in volcanic materials seem to support this interpretation.Relatively low40Ar/36Ar ratios, as low as 282, have been observed in recent Japanese volcanic rocks. Such a low40Ar/36Ar ratio may be explained by mass fractionation of the atmospheric value if the rare gases represent those which were transported into the magma chamber with other volatile elements.Both the amounts and the fractionated rare gas abundance pattern of lighter elements which are observed in pumices from the recent eruption of Mt. Usu, Southern Hokkaido, Japan, suggest the possibility of air injection into its magma chamber. Thus, the fractionation of rare gases in volcanic materials may be a common occurrence, and it must be considered in models for the origin of isotopic differences between rare gases in volcanic materials and the atmosphere.  相似文献   

20.
Activity concentration data from ambient radioxenon measurements in ground level air, which were carried out in Europe in the framework of the International Noble Gas Experiment (INGE) in support of the development and build-up of a radioxenon monitoring network for the Comprehensive Nuclear-Test-Ban Treaty verification regime are presented and discussed. Six measurement stations provided data from 5 years of measurements performed between 2003 and 2008: Longyearbyen (Spitsbergen, Norway), Stockholm (Sweden), Dubna (Russian Federation), Schauinsland Mountain (Germany), Bruyères-le-Châtel and Marseille (both France). The noble gas systems used within the INGE are designed to continuously measure low concentrations of the four radioxenon isotopes which are most relevant for detection of nuclear explosions: 131mXe, 133mXe, 133Xe and 135Xe with a time resolution less than or equal to 24 h and a minimum detectable concentration of 133Xe less than 1 mBq/m3. This European cluster of six stations is particularly interesting because it is highly influenced by a high density of nuclear power reactors and some radiopharmaceutical production facilities. The activity concentrations at the European INGE stations are studied to characterise the influence of civilian releases, to be able to distinguish them from possible nuclear explosions. It was found that the mean activity concentration of the most frequently detected isotope, 133Xe, was 5–20 mBq/m3 within Central Europe where most nuclear installations are situated (Bruyères-le-Châtel and Schauinsland), 1.4–2.4 mBq/m3 just outside that region (Stockholm, Dubna and Marseille) and 0.2 mBq/m3 in the remote polar station of Spitsbergen. No seasonal trends could be observed from the data. Two interesting events have been examined and their source regions have been identified using atmospheric backtracking methods that deploy Lagrangian particle dispersion modelling and inversion techniques. The results are consistent with known releases of a radiopharmaceutical facility.  相似文献   

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