Morris R C, Fraley L
Dept. of Radiology and Radiation Biology, Colorado State University, Fort Collins 80523.
Health Phys. 1989 Apr;56(4):431-40. doi: 10.1097/00004032-198904000-00004.
We measured 222Rn fluence rate and several environmental variables on two plots with U mill tailings buried beneath 30 cm of overburden and 20 cm of topsoil. An additional 30 cm of clay covered the tailings on one plot and each plot was subdivided into bare soil and vegetated subplots. We used linear correlation, two-way ANOVA and stepwise multiple regression to analyze the effects of the plot characteristics and the environmental variables on 222Rn fluence rate. The most important effect on 222Rn fluence rates from these plots was the combination of a clay cap and a vegetated surface. The mean annual fluence rate from the plot having both of these characteristics (520 +/- 370 mBq m-2 s-1) was over three times that of the vegetated plot without a clay cap (170 +/- 130 mBq m-2 s-1) and 18 times that of the bare plot with a clay cap (29 +/- 13 mBq m-2 s-1). The interaction effect may have been due to the growth of roots in the moist clay and active transport of dissolved 222Rn to the surface in water. This speculation is supported by the observation that on vegetated plots with a clay cap, moisture in the clay enhanced the fluence rate.
我们在两个地块上测量了222Rn注量率以及几个环境变量，这两个地块的铀矿尾矿埋在30厘米厚的覆盖层和20厘米厚的表土之下。在其中一个地块上，尾矿又覆盖了额外30厘米厚的黏土，每个地块又被细分为裸土子地块和植被覆盖子地块。我们使用线性相关、双向方差分析和逐步多元回归来分析地块特征和环境变量对222Rn注量率的影响。这些地块对222Rn注量率最重要的影响因素是黏土覆盖层和植被覆盖表面的组合。同时具备这两个特征的地块的年平均注量率（520±370毫贝克勒尔·米-2·秒-1）是没有黏土覆盖层的植被覆盖地块（170±130毫贝克勒尔·米-2·秒-1）的三倍多，是有黏土覆盖层的裸地地块（29±13毫贝克勒尔·米-2·秒-1）的18倍。这种相互作用效应可能是由于根系在湿润的黏土中生长以及溶解态的222Rn在水中向表面的主动运输。在有黏土覆盖层的植被覆盖地块上，黏土中的水分提高了注量率，这一观察结果支持了这一推测。
