Depositions in nine localities

Analysing deposition samples provides information on the quantities of radioactive materials in different parts of the country and forms the basis for reports and studies on the migration of radioactive materials in the soil and bodies of water.

Deposition samples are taken on a continuous basis in nine localities. The collection period for deposition samples is typically one month. Deposition samples are collected with a stainless-steel instrument with a collection area of 0.07m2. The instrument is not able to differentiate between wet depositions caused by rainfall and dry depositions, and measures them as a total. To facilitate samples during winter months, the instruments are fitted with heat resistance to keep the samples unfrozen and to ensure that all snow collected in the collection container is included in the sample. The samples are analyzed for Cs-137 and Sr-90 and the rainwater samples of two stations are also analyzed for H-3.

Radioactive materials identified in depositions preceding 1986 originate from the fallout resulting from nuclear weapon testing performed in the atmosphere. Measurements from this type of fallout typically vary between the different seasons of the years. The Cs-137 and Sr-90 detected from post-1986 depositions mainly originate from the explosion at the Chernobyl power plant. The radioactive materials carried by fallout migrate locally, with a small portion of them re-entering the atmosphere. Tritium concentrations of rainfall in 2014 were low, with radioactivity levels ranging between 1–4 Bq/l.




  • Vaaramaa Kaisa
    Head of Laboratory / MIT tel. +358975988521