Interception and transfer of wet-deposited 134Cs to potato foliage and tubers

Contamination levels on potato foliage and tubers were investigated by repeated sampling after multiple foliar contaminations of wet-deposited 134Cs at five different growth stages in a micro-plot field experiment in three successive years. Application of the radionuclide early in the growing season (deposition date 19-27 June, growth stage II = plant establishment) resulted in low 134Cs activity concentration in potato tubers across sampling occasions (mean 60, 25 and 115 Bq kg−1 dry weight (D.W.) for years 1, 2 and 3, respectively). Following radionuclide deposition in the middle of the growing season (15-24 July, growth stage III = tuber initiation), 134Cs activity concentration in tubers across sampling occasions was found to be highest (mean 150, 850 and 660 Bq kg−1 D.W. for years 1, 2 and 3, respectively). When the radionuclide was sprayed on at later stages (5-7 August, growth stage IV = tuber bulking), 134Cs activity concentrations in tubers across sampling dates decreased (mean 75, 310 and 395 Bq kg−1 D.W. for years 1, 2 and 3, respectively). Deposition in the second half of August (15-28 August, late growth stage IV and beginning of growth stage V = tuber maturation) resulted in yet lower 134Cs activity concentration in tubers. Potato tubers may concentrate as much as up to 2 times more 134Cs than foliage depending on deposition date of radionuclide.