Caesium radioactivity in several selected species of honey

In the years following the accident to the nuclear power plant at Chernobyl, investigations on several selected species of honey were done to determine their 134,137Cs contamination. Very low caesium activities were found in flower honeys, especially rape honeys. The transfer factor of caesium from the soil to the rape plant (Brassica napus var. oleifera) was found to be ƒCs = 0.116 ± 0.080 in 1987, but only ƒCs = 0.017 ± 0.017 in 1988, due to the lower availability of the caesium by gradual formation of water-insoluble chemical species. Honeydew honeys show a slightly higher 134,137Cs contamination. Honeydew is often produced by lice settling on spruces. Therefore, needles and twigs of spruces (Picea abies) were investigated and relatively high caesium contamination was found in fresh needles. A transfer factor for caesium from spruce needles to honeydew honey of about 0.1 was estimated. Finally, the caesium contamination in heather honeys and heather plants (Calluna vulgaris) was determined. Surprisingly higher factors between 2 and 40 were obtained for the caesium transfer from soil to Calluna vulgaris. These factors give a good explanation for the relatively high caesium contamination of heather honeys.