Radiocesium in soil and plants in a forest in central Sweden

The distribution of 137Cs in the soil profile and in plants was studied in a forest located 35 km northwest of Uppsala. More than 85% of the total 137Cs activity was found in the upper 5 cm of the soil profile, implying that nearly all 137Cs activity is found in the raw humic layer that extends to a depth of about 10 cm in a normal Swedish coniferous forest. The 137Cs activity concentrations in some plants (birch, Scots pine, bilberry, lingonberry, and heather) are presented for the period from 1986 until 1991. Levels of 137Cs activity in bilberry and lingonberry have decreased since 1986, but in the other plants, the level of activity seems to be relatively constant from 1986 to 1991. This means that the normal level of 137Cs activity found in heather is about 12000 Bq/kg (dry wt.)