Berlin Environmental Atlas 01.09 Radioactivity in Soils (Cesium-134 and Cesium-137)

Map 01.09.3 Cesium-134 and Cesium-137 on 1 May 1987

Total contamination loads (old and new inputs), calculated for 1 May 1987, show cesium-134 to have an activity of only 75% of its original load levels, due to its rate of decay. Contaminated areas were defined by new inputs from the Chernobyl incident, and old deposits.

Map 01.09.4 Cesium-134 and Cesium-137 on 1 May 1991

The progression of radioactive decay of tested isotopes produced the results of 1 May 1991. Surface activity of cesium-134 is only 20% of original load levels, while cesium-137 concentrations have declined only about 7.5% in comparison to new inputs.

Evaluation of Potential Dangers of Soil Loads

Radioactive substances deposited in soils can reach humans through:

• soil-plant transfer
• washout into ground water
• disturbed soils
• direct radiation.

It is difficult to make a direct evaluation for the dangers posed to humans by soil loads, because the transfer of pollutants such as cesium-137 from topsoil into cultivated plants is determined by many factors; particularly the type of soil, the type and age of plants, the concentration of pollutants in the soil and ground water, and other parameters. Transfer factors are disputed (Litz/Tietz 1987). These factors are used for the estimation of threats arising from soil contamination loads and as measure for the soil-plant transfer. A transfer factor is defined as the concentration of pollutants in the plant, divided by the concentration of pollutants in the soil. The transposition of individual transfer factors, always determined by selected conditions for the respective individual situation, is linked to the observance of these boundary conditions. New investigations show that the concentration of a pollutant in a plant is directly related to the concentration of the pollutant in the waters of the soil, but not to the concentrations in the soil itself (Schüttelkopf/Schmidt 1990).

Despite these limiting statements, some statements can be made about possible health threats posed by existing soil contamination loads in Berlin.

Dosage through direct soil radiation - based on cesium-137 - is negligible. Measuring techniques cannot document it and it disappears in the background radiation.

The inhalation of radioactive cesium through dust can be evaluated by measurements of activity concentrations in the air. It amounts on the average to less than 0.00001 Bq/m² and is negligible, even in comparison to the mean natural levels (such as radon-226 and its resulting products).

Foodstuffs are therefore the only significant factor. They are investigated at both the production and the trade level. The Radiation Measurement Office of the Berlin Department of Urban Development and Environmental Protection publishes measuring results every week in "Weekly Reports" and distributes them to various information media, consumer associations, etc. Certain products continue to be listed among the more highly contaminated foodstuffs. Those are mainly forest fruits, mushrooms and animals that live on undisturbed, humus-rich forest soils.