Abraham Johannes, Meusburger Katrin, Waldis Judith Kobler, Ketterer Michael E, Zehringer Markus
State-Laboratory Basel-City, Kannenfeldstrasse 2, CH-4056 Basel, Switzerland.
Environmental Geosciences, University of Basel, Bernoullistrasse 30, 4056 Basel, Switzerland.
J Environ Radioact. 2018 Feb;182:85-94. doi: 10.1016/j.jenvrad.2017.11.019. Epub 2017 Dec 1.
An important process in the production of drinking water is the recharge of the withdrawn ground water with river water at protected recharge fields. While it is well known that undisturbed soils are efficiently filtering and adsorbing radionuclides, the goal of this study was to investigate their behaviour in an artificial recharge site that may receive rapid and additional input of radionuclides by river water (particularly when draining a catchment including nuclear power plants (NPP)). Soil profiles of recharge sites were drilled and analysed for radionuclides, specifically radiocesium (Cs), radiostrontium (Sr) and plutonium (Pu). The distribution of the analysed radionuclides were compared with an uncultivated reference soil outside the recharge site. The main activity of Cs was located in the top soil (4.5-7.5 cm) and reached down to a depth of 84 cm and 48 cm for the recharge and the reference site, respectively. The found activities of Pu originate from the global fallout after 1950. Pu appeared to be strongly adsorbed onto soil particles. The shape of the depth profile was similar to Cs, but also similar between the recharge and the reference site. In contrast, Sr showed a uniform distribution over the entire depth of the recharge and reference profiles indicating that Sr already entered the gravel zone and the ground water. Elevated inventories of the radionuclides were observed for the recharge site. The soil of the recharge field exhibited a threefold higher activity of Cs compared to the reference soil. Also for Pu higher inventories where observed for the recharge sites (40%). Sr behaved differently, showing similar inventories between reference and recharge site. We estimate that 75-89% of the total inventory of Cs in the soil at the recharge site (7.000 Bq/m) originated from the fallout of the Chernobyl accident and from emissions of Swiss NPPs. This estimate is based on the actual activity ratio of Cs/Pu of 22 for global fallout. The investigations identified radiostrontium as potential threat to the ground water.
饮用水生产中的一个重要过程是在受保护的回灌区域用河水对抽取的地下水进行回灌。虽然众所周知，未受扰动的土壤能有效过滤和吸附放射性核素，但本研究的目的是调查它们在人工回灌场地中的行为，该场地可能会因河水而快速额外输入放射性核素（特别是在排水流域包括核电站（NPP）的情况下）。对回灌场地的土壤剖面进行钻孔并分析放射性核素，特别是放射性铯（Cs）、放射性锶（Sr）和钚（Pu）。将分析的放射性核素分布与回灌场地外未耕种的参考土壤进行比较。Cs的主要活度位于表层土壤（4.5 - 7.5厘米），在回灌场地和参考场地分别向下延伸至84厘米和48厘米深度。所发现的Pu活度源自1950年后的全球沉降。Pu似乎强烈吸附在土壤颗粒上。深度剖面的形状与Cs相似，但在回灌场地和参考场地之间也相似。相比之下，Sr在回灌和参考剖面的整个深度上分布均匀，表示Sr已经进入砾石层和地下水。在回灌场地观察到放射性核素库存升高。回灌场地的土壤中Cs活度比参考土壤高两倍。对于Pu，回灌场地也观察到更高库存（40%）。Sr表现不同，参考场地和回灌场地之间的库存相似。我们估计，回灌场地土壤中Cs总库存（7000 Bq/m）的75 - 89%源自切尔诺贝利事故沉降和瑞士核电站排放。该估计基于全球沉降中Cs/Pu的实际活度比22。调查确定放射性锶是对地下水的潜在威胁。
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