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11.
L. Kristensen C. E. Andersen H. E. Jørgensen P. Kirkegaard K. Pilegaard 《Journal of Atmospheric Chemistry》1997,27(3):249-269
We have discussed the behavior of a non-conserved scalar in the stationary, horizontally homogeneous, neutral surface-flux layer and, on the basis of conventional second-order closure, derived analytic expressions for flux and for mean concentration of a gas, subjected to a first-order removal process. The analytic flux solution showed a clear deviation from the constant flux, characterizing a conserved scalar in the surface-flux layer. It decreases with height and is reduced by an order of magnitude of the surface flux at a height equal to about the typical mean distance a molecule can travel before destruction. The predicted mean concentration profile, however, shows only a small deviation from the logarithmic behavior of a conserved scalar. The solution is consistent with assuming a flux-gradient relationship with a turbulent diffusivity corrected by the Damköhler ratio, the ratio of a characteristic turbulent time scale and the scalar mean lifetime. We show that if we use only first-order closure and neglect the effect of the Damköhler ratio on the turbulent diffusivity we obtain another analytic solution for the profiles of the flux and the mean concentration which, from an experimental point of view, is indistinguishable from the first analytic solution. We have discussed two cases where the model should apply, namely NO which, by night, is irreversibly destroyed by interaction with mainly O3 and the radioactive 220Rn. Only in the last case was it possible to find data to shed light on the validity of our predictions. The agreement seemed such that a falsification of our model was impossible. It is shown how the model can be used to predict the surface flux of 220Rn from measured concentration profiles. 相似文献
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大气氡测量影响因素探讨 总被引:1,自引:0,他引:1
杨亚新 《华东地质学院学报》1996,19(3):289-294
本文介绍了地壳中放射性元素的分布规律及大气中氡的来源,并着重讨论了测量大气氡浓度的影响因素,以便更好地进行放射性环境的评价及防止,避免氡对人体的危害。 相似文献
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The incidence of lung cancer in the Gejiu area of Yunnan Province ranks the first in the world.The radon level(indoor,soil) was measured in the Gejiu area by the SSNTD method from 1990 to 1996,The result indicates an extensive high-level of indoor radon in that area though U and Th are lower in local limestones,The indoor radon level of houses located in the geologic fault zone is 6 times high that 2km far from the fault zone.The reason probably is that the radon level of soil in the fault is 6-8 times high that 1 km far from the faults.our data indicate that a lower range of radon levels,0-100Bq.m^-3,exists in healthy families.However,a higher radon level,over 800 Bq.m^-3,is often found corresponding to that of cancer patients‘ homes(the house-owners are suffering from either lung cancer or leukaemia or liver cancer),Obviously,an increase in lung cancer incidence follows an increase in indoor radon level,The risk of cancer induced by indoor radon is no longer an inference,but a fact. 相似文献
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为了探查新疆昭苏盆地砂岩型铀矿的异常信息,选择可控源音频大地电磁测量、高精度磁测和土壤氡气测量三种物探方法,并简要介绍各方法的工作原理。通过分析昭苏盆地的地质特征、物性特征和本区的找矿难点,对昭苏盆地综合物探数据所蕴含的信息进行地质-物探综合解译。实践证明:可控源音频大地电磁测量对低阻和高阻体均有良好的电性响应,可以划分地层、推断断裂构造;高精度磁测可以推断氧化还原界面,辅助解释断裂构造;土壤氡气测量可辅助解释断裂构造,对地下铀矿体有指示作用,三种方法的技术特性相互补充,提高了物探解释的准确性。突破了伊犁盆地以往600 m的找矿深度,并以电性稳定的中阻厚层、磁测异常、氡异常偏高晕和峰-谷状曲线作为预测标志,解决了深埋藏条件下赋矿地质体的圈定难点,在昭苏盆地砂岩型铀矿中、深部找矿工作中取得了良好的效果。 相似文献
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N. Segovia S. de la Cruz-Reyna M. Mena E. Ramos M. Monnin J. L. Seidel 《Natural Hazards》1989,1(4):319-329
A radon anomaly in a nuclear track detector placed on a fault was detected prior to the destructive (Ms = 8.1) Mexican earthquake of 19 September 1985. The fault is a structural feature of the geothermal field Los Azufres, 260 km NE of the epicentral area. Since no other phenomenon can be found as a possible cause for the radon anomaly, it is proposed that preseismic regional stress perturbations may produce changes in the fluid transport patterns at the fault, suggesting that radon measurements in similar conditions could provide a good precursor in high seismic risk areas. 相似文献