It is an artificial radionuclide with a half-life of 30 years or so which was released into the stratosphere by the testing of above ground thermonuclear weapons in the late 1950s and early 1960s and deposited as fallout. Some countries had extra input in 1986 after Chernobyl incident. This annual variation has been successfully used to determine sediment accumulation rates in a wide variety of depositional environments including reservoirs, lakes, wetlands, coast areas, and flood plains. Soil redistribution rates estimated are less influenced by extreme events With a single field visit, caesium-137 technique can provide spatially distributed data for parameterising and testing distributed erosion and sediment yield models and interfacing with recent developments in the application of GIS and geostatistics to this field. Subsequent redistribution of the radiocaesium reflects the movement of soil particles since the caesium-137 remains absorbed and moves in associated with the soil particles.
Higher inventory indicates deposition and lower inventory indicates erosion.
Collection of soil core samples from the study field and from undisturbed 'reference' sites in the surrounding area. Cored samples can be sliced to show the depth distribution of caesium-137 activity. A motorised percussion corer may be used. Measurement of total remaining caesium-137 fallout to the location by analysis of soil samples from the 'reference' sites. A gamma spectrometry is indispensable.