Mobility of superficially applied caesium-134 and strontium-85 in apple branches under precipitation-free conditions

Abstract

The recovery of superficially applied ¹³⁴Cs⁺ and ⁸⁵Sr²⁺ in apple branches protected from precipitation decreased with time. Translocation of ¹³⁴Cs to uncontaminated branches declined rapidly with the distance from the contaminated branches. Extensive translocation of ¹³⁴Cs from foliage to fruits occurred within the same branch: after 84 d, 50% of the recovered activity was found in fruits and most of it in the edible part (excluding peel). On the other hand, ⁸⁵Sr was less mobile and in virtually all fruit ⁸⁵Sr was in the peel. Rinsing leaves removed 30% of both radionuclides 1 d after contamination and decreasing fractions later on. Rinsing fruits removed up to 62% of the peel radionuclides. Further rinses and washes (plus detergent) of fruits showed that ¹³⁴Cs had the same distribution in the outer skin as ⁸⁵Sr and that the ratio of the two nuclides was close to the ratio in the contamination solution. This indicates that apple skin is a barrier not only to ⁸⁵Sr, but probably also to ¹³⁴Cs. Unaccounted for disappearance of radioactivity from fruits and leaves could have been a result of field losses of small superficial particles.