Several radioactive nuclides were deposited in Sweden after the Chernobyl accident in 1986. The greatest attention was given to 137Cs because of its relative long physical half life of about 30 years. 137Cs will be present in nature for more than 100 years before it has vanished completely. When radiocaesium decays to a stable end product ionizing radiation is emitted, which can cause cancer in humans that has been exposed to a high radiation dose. Radiocaesium behaves like potassium and is easily taken up into biological systems. It is important to know how 137Cs behaves in nature to be able to minimize the risk towards humans.
In this study the content and transfer of 137Cs in agricultural crops were investigated at a number of farms in the counties of Uppsala, Västmanland and Gävleborg in 2005. The study was a follow-up on earlier sampling accomplished in 1986-2003 on the same farms. The
crops sampled and analysed for 137Cs-activity were mainly ley and pasture, only a couple of samples were taken on cereals and leguminous plants.
The results from 2005 showed that the changes in the 137Cs-content in the sampled crops were small compared to the last sampling in 2003. The mean 137Cs-content was merely the same in the samples from ley and pasture and it was very low in the samples from the cereals and the leguminous plants. The results from 1986-2005 showed a remarkable high reduction of both the transfer and the content of 137Cs between 1986 and 2005. The highest reduction was found the first two years after the Chernobyl accident and the level was relatively low and kept on a steady state during the years between 1988 and 2005. The highest 137Cs-content was found on peat soils and coarse mineral soils with a low content of both non-exchangeable and exchangeable potassium and low cultivation rate and a high deposition of 137Cs after the Chernobyl accident.
The study also concluded a case study on a dairy farm in the county of Gävleborg. The aim of the case study was to calculate a stable balance for 137Cs. Samples were taken in the cowshed and on the pasture between July and October in 2005. The samples were analysed for 137Cs. Stable balance calculations were accomplished for the grazing period and the winter period for one cow during a month.
The 137Cs-contents were generally low, which gave a great uncertainty in the stable balance calculations. The results showed that...
