Concentration in different plant compartments of radiocaesium and radiostrontium, wet deposited on spring oilseed crop Ph.D. student Stefan B. Bengtsson Department of Soil and Environment, Swedish University of Agricultural Sciences, P.O. Box 7014, SE Uppsala, Sweden © Oliver Dixon, 2011

Background  Uptake of radionuclides depends on development stage of the crop, well-developed stage biggest part taken up by leafs through cracks and defects in the cuticle layer and through stomata.  Uptake by leafs are dependent on temperature, pH, light, the carrier of solution, and plant species.  Transport between organs, diffusion inside cell walls, physiological transports between phloem and xylem. 2

Aim  How deposition of radionuclides influence the concentration in different plant parts edible ones.  How this depends on development stage, weather and length of time period before harvest.  Information available is limited. 3

Material and Method  Spring oilseed rape (Brassíca napus L.) grown on clay soil.  134 Cs and 85 Sr deposited at six different development stages.  Biomass samples: dried (30°C), weighed and radioactivity was measured with High-Purity Germanium (HPGe) detectors.  Concentrations measured in the following plant compartments; stems, leaves, flowers, “siliques excepts seeds” and seeds.  Leaf area index (LAI) measured with a LAI 2000 device. 4

Figure 1. The rain simulator constructed at the Department of Soil and Environment. The target amount of precipitation was 1 mm m -2 per treatment. 5

6 Figure 2. The different plant growing stages when the deposition of contaminated rain occured (Bengtsson et al., 2011 ”in preperation”).

7 Figure 3. Botanical picture of Spring oilseed crop. The different plant compartment; stems, leaves, flowers, ”siliques without seeds” and seeds are shown.

Results Figure 4. Concentration of 134 Cs and 85 Sr in Bq kg -1 in seeds at the senescence growing stage. 6 different deposition events at different growth stages. 8

Figure 5. Concentration of 134 Cs and 85 Sr in Bq kg -1 in “siliques without seeds” at the senescence growing stage. 6 different deposition events at different growth stages. 9

Figure 6. Concentration of 134 Cs and 85 Sr in Bq kg -1 in stems at the senescence growing stage. 6 different deposition events at different growth stages. 10

Figure 7. Percentages of 134 Cs in different plant compartment at the growing stage of senescence for 6 different deposition events for different growth stages 11

Figure 8. Percentages of 85 Sr in different plant compartment at the growing stage of senescence for 6 different deposition events for different growth stages 12

Conclusions  Well-developed stand the majority of radionuclides are intercepted and taken up directly by the leaves.  Concentration in different plant compartments are combined effects of intercepted radionuclides and translocation of these. 13

Ph.D. student Stefan Bengtsson Swedish University of Agricultural Sciences, Department of Soil and Environment, P.O. Box 7014, SE Uppsala, SWEDEN