Lichens are the best terrestrial bioindicators for radioactive fallout and also the most important link in foodchain lichen - reindeer - man. Generally, Fenced permanent sampling plots are used to study the biological half-life of 137Cs in lichen. However, some of the STUKs sampling plots are unfenced which are subjected to grazing by reindeer. Start year: early 60's as a project of the Radiochemistry Department of University in Helsinki. Stuk's participation since 1975. Data are collected from 1961, 1980, 1982 or 1986, continuously every 3-5 years. Data processing/work-up and data archiving/reporting work are conducted from 1961, 1980, 1982. Continous data sets from 1986 to 2010.
The lichen plot samples represent 50 cm x 50 cm area. Humus layer and about 5 cm mineral soil layer underneath are also sampled. By this sampling technigue also Bq/m2 results are obtained in addition to Bq/kg values. Only Bq/kg values are obtained in areas with sparse lichen carpet. The collected samples are separated to different lichen species. Cladonia lichens longer than 3 cm are divided into top, (middle) and lower sections. Lichen samples are died at 105oC, soil layers at room tempetature and homogenized before gammaspectrometric measurement.
Samples collected by STUK since 1975. All of them as dried, homogenized samples in plastic bags and jars stored in metal containers at room temperature in STUKs Regional Laboratory in Northern Finland. Only the few samples analysed radiochemically for 90Sr may be destroyed completely.
Sampling and pretreatment described under other data (above)
Intercomparison IAEA and EPA STUK is accreditated for gammaspectrometric measurements, 90Sr and Pu-isotope analyses (FINAS)
Utsjoki sampling location is owned by a sami reindeer herder family