Plant uptake of radiocesium from contaminated soil

Phytoextraction field experiments were conducted on soil contaminated with radiocesium to determine the capacity of autochthonous grasses and weeds to accumulate 137Cs. The aim of the study was to evaluate the potential of spontaneously growing vegetation as a tool for decontamination of non-agricultural contaminated land. As a test field, the closed monitored area of the radioactive wastewater treatment plant of the Nuclear Power Plant in Jaslovské Bohunice, Slovakia was used. Contamination was irregularly distributed from the level of background to spots with maximal activity up to 900 Bq/g soil. Sequential extraction analysis of soil samples showed the following extractability of radiocesium (as percent of the total): water < 0.01%; 1 M MgCl2 = 0.3-1.1%; 1 M CH3COONa = 0.3-0.9%; 0.04 M NH4Cl (in 25% CH3COOH) = 0.9-1.4%; and 30% H2O2 - 0.02 M HNO3 = 4.5-9.0%. Specific radioactivity of the most efficiently bioaccumulating plant species did not exceed 4.0 kBq kg 1 (dry weight biomass). These correspond to the soil-to-plant transfer factor (TF) values up to 44.4 × 10 4 (Bq kg 1 crop, d.w.)/(Bq kg 1 soil, d.w.). Aggregated transfer factor (Tag) of the average sample of the whole crop harvested from defined area was 0.5 × 10 5 (Bq kg 1 d.w. crop)/(Bq m 2 soil). It can be concluded that low mobility of radiocesium in analysed soil type, confirmed by sequential extraction analyses, is the main hindrance for practical application of autochthonous plants as a phytoremediation tool for aged contaminated area of non-cultivated sites. Plant cover can efficiently serve only as a soil surface-stabilising layer, mitigating the migration of radiocesium into the surrounding environment.