Centofanti T, Penfield R, Albrecht A, Pellerin S, Flühler H, Frossard E
Plant Nutrition, Institute of Plant Sciences, ETH Zurich, Lindau (ZH), Switzerland.
J Environ Qual. 2005 Oct 12;34(6):1972-9. doi: 10.2134/jeq2004.0412. Print 2005 Nov-Dec.
The radiological impact of radionuclides released to the terrestrial environment is usually predicted with mathematical models in which the transfer of radionuclides from soil to the plant is described with the transfer factor (TF). This paper questions the validity of the protocols proposed by the International Atomic Energy Agency to measure TF in the field and in greenhouses conditions. We grew maize (Zea mays L.) both in the field after a surface application of radionuclides ((54)Mn, (57)Co, (65)Zn, and (134)Cs) and in a greenhouse with the same soil that has received the same fertilization and that had been previously sieved and homogeneously labeled with the same radionuclides before being repacked in pots. The analysis of the displacement of radionuclides in the field soil profile showed a higher concentration of the surface-applied radionuclides in the preferential flow path (PFP) in comparison to the soil matrix indicating that they infiltrated heterogeneously in the soil profile due to the structure-induced non-uniform water flow. A significantly higher recovery of (57)Co and (134)Cs was observed in the plants grown in the field soil, whereas no differences in the recovery of (54)Mn and (65)Zn between the two experiments were detected. These results suggest that (i) under field conditions the soil-to-plant transfer of radionuclides that co-exist as stable elements present at low concentrations in the soil and in the plant is higher than that measured under greenhouse conditions and (ii) the implicit assumption made when calculating the TF (that radionuclides are homogeneously distributed in the soil profile) is not valid, thereby preventing the calculation of an average concentration to obtain the TF parameter.
释放到陆地环境中的放射性核素的辐射影响通常用数学模型来预测,在这些模型中,放射性核素从土壤到植物的转移用转移因子(TF)来描述。本文对国际原子能机构提出的在田间和温室条件下测量TF的方案的有效性提出质疑。我们在放射性核素((54)Mn、(57)Co、(65)Zn和(134)Cs)表面施用后在田间种植玉米(Zea mays L.),并在温室中用相同的土壤种植,该土壤接受了相同的施肥,并且在重新装盆之前预先过筛并用相同的放射性核素均匀标记。对田间土壤剖面中放射性核素位移的分析表明,与土壤基质相比,优先流路径(PFP)中表面施用的放射性核素浓度更高,这表明由于结构诱导的水流不均匀,它们在土壤剖面中不均匀渗透。在田间土壤中生长的植物中观察到(57)Co和(134)Cs的回收率显著更高,而在两个实验之间未检测到(54)Mn和(65)Zn回收率的差异。这些结果表明:(i)在田间条件下,作为土壤和植物中低浓度稳定元素共存的放射性核素从土壤到植物的转移高于在温室条件下测量的转移;(ii)计算TF时所做的隐含假设(即放射性核素在土壤剖面中均匀分布)是无效的,从而无法计算平均浓度以获得TF参数。