Published online by Cambridge University Press: 16 September 2008
The activity concentration of 137Cs, 131I, 65Zn, 60Co, 58Co, 54Mn, and 40K were determined in samples of brown seaweed (Fucus) and some other marine plants using low background high-resolution gamma-spectrometry. The algae were mainly sampled in the bay just north of the Barsebäck NPP (55.4 N, 12.6 E) in the south of Sweden to study the contamination levels in the nearest shallow waters. One aim of the study was to investigate whether the levels were high enough to expect environmental effects. Some samples were also taken at longer distances up to 130 km from the Barsebäck NPP. Measurable levels of the neutron activation products 65Zn (up to 17 Bq/kg dw), 60Co (100–600 Bq/kg dw), 58Co (1–160 Bq/kg dw) and 54Mn (12–90 Bq/kg dw) were found in the algae samples within a distance of 5 km from the plant. The decrease in activity concentration with distance from the plant could be described by a power function with an exponent ranging from 1.4 to 2.4.This was in fair agreement with the value for a true two-dimensional dispersion model. The present-day concentrations were found to be considerably lower than in earlier studies made in the late 1970s, especially for 65Zn and 58Co. The activity concentration of gamma emitting radionuclides in Fucus vesiculosus from the bay just north of Barsebäck in the period 2002-2003 was dominated by (in order of decreasing concentration): natural 40K, 60Co from the plant, 137Cs mainly from the Chernobyl debris, 54Mn and 58Co from the plant. It is not likely that any effects from the very marginal absorbed dose contribution from the Barsebäck NPP releases can be found even in the nearest environment. The study has also shown that the eelgrass Zostera marina may be a bioindicator to use in further studies of the radiation environment in shallow water, especially for 60Co and 54Mn.