The distribution of stable cesium in soils and plants of the eastern Snake River Plain in southern Idaho

Radiocesium has been introduced into ecosystems via nuclear technology activities. The distribution of stable cesium, 133Cs, is a long-term indicator of radiocesium movement in ecosystems. Plant uptake of Cs is expressed by the transfer factor (TF), which is the ratio of plant to soil Cs concentrations. We determined Cs TFs and the factors affecting soil Cs distribution for 330 plant and 28 soil samples collected from 27 sites on the eastern Snake River plain in Idaho. Soil samples were analysed for Cs. A variety of soil properties were determined, and soil Cs was significantly positively correlated to both soil quartz content and soil cation exchange capacity, properties indicative of the supply and retention of Cs, respectively. Titanium (Ti) concentrations were determined for plant samples and used to generate a soil contamination index (CI). Multiple regression analysis explained up to 95.3% of the variation in Cs TF with either plant Cs, plant Ti, or the CI, compared with only 4.9% with soil parameters alone. These results indicated that soil Cs concentration is influenced by the same factors reported for other locations and that much of the plant Cs is caused by soil contamination and not uptake. Lastly, because no Cs TFs approached unity, no plants accumulated Cs.