⁴⁰K, ¹³⁴Cs and ¹³⁷Cs in pollen, honey and soil surface layer in Croatia

Abstract - Specific activities of ⁴⁰K, ¹³⁴Cs and ¹³⁷Cs in pollen, honey and in the first 25 cm of the surface soil layer were measured by gamma-spectrometry. Specific activity of ⁴⁰K in pollen is about 1 order of magnitude higher than in honey. A ⁴⁰K soil-to-pollen transfer coefficient (TC( ⁴⁰K)) of 0.436 ± 0.054 and a soil-to-honey transfer coefficient TC(⁴⁰K) of 0.052 ± 0.008 were calculated as the mean of their respective values in 26 different segments of soil profile. Both parameters have very stable values over time as well as through different segments of vertical soil profile. ¹³⁴Cs and ¹³⁷Cs specific activities in pollen and honey decrease with time, resulting in a decrease of ¹³⁷Cs soil-to-honey transfer factors (T_f(¹³⁷Cs)) over time. The increase of the soil-to-honey T_f(¹³⁷Cs) with increasing soil depth is a consequence of vertical distribution of ¹³⁷Cs in soil. Soil-to-honey T _f(¹³⁷Cs) values are highest in meadow and mixed honey types and lowest in bush/tree honey. Similar trends are found for both T_f(¹³⁴Cs) and T_f(¹³⁷Cs). The results presented here indicate the importance of the caesium inventory in soil segments where plant root systems are developed.