Temporal and seasonal variations of radiocaesium content in some plants from the western part of Ukrainian Polesye

We present measurements of 137Cs contamination for some of the berry plants and medicinal herbs growing in the western part of Ukrainian Polesye during 1996–2009. Basing on the calculations of the aggregated transfer factors, we classified the medicinal herbs into five groups according to their ability for accumulation of 137Cs: very weak (Tag < 10−3), weak (10−3 < Tag < 10−2), moderate (10−2 < Tag < 5 × 10−2), strong (5 × 10−2 < Tag < 10−1) and very strong (Tag > 10−1). The 137Cs concentrations in the berry plants significantly decreased during the time of our monitoring and the rate of this decrease was much higher than that typical of the corresponding soils. This is because with time the 137Cs in the soil was becoming less accessible for uptake by plant roots due to its fixation on micaceous clay minerals. The seasonal variations of the 137Cs concentrations in the vegetative and generative organs of the plants revealed a good interdependence between the seasonal peculiarities of 137Cs accumulation by the organs and the features of their vegetation period.

► We studied 137Cs contamination of some medical herbs during 1996–2009.
► The plants were classified into groups according to ability for accumulation of 137Cs.
► The 137Cs content in the plants has significantly decreased during the monitoring.
► The rate of this decrease is notably higher than that for the soils.
► Seasonal changes of the 137Cs content in the berry plants were studied.