Current radioactive fallout contamination along a trans-European gradient assessed using terricolous lichens.

Lichens are considered to be good indicators of contamination of the terrestrial environment. In this study, we investigated the level of Cs and  K accumulated by Cladonia arbuscula and Stereocaulon alpinum along a longitudinal gradient from northern Norway, across Sweden to southern Poland. Additionally, we compared isotope contents between the selected lichen species, and investigated the correlation of the Cs content accumulated by C. arbuscula with Cs fallout after the Chernobyl disaster. The activity of Cs varied from 3.58 Bq kg to 559 Bq kg for S. alpinum, and from 1.18 Bq kg to 130 Bq kg for C. arbuscula. The activity of  K ranged from 114 Bq kg to 341 Bq kg for S. alpinum and from 27.2 Bq kg to 314 Bq kg for C. arbuscula. The Cs content did not differ between C. arbuscula and S. alpinum; however, the difference between species was significant for  K accumulation. The activity of Cs in C. arbuscula was significantly correlated with deposition from 1986. Based on our findings we created a spatial map of Cs activity in lichens measured 30 years after the event that was the primary source of this isotope. We showed that C. arbuscula can be used to assess contamination and create interpolation maps of radionuclide deposition, even if the primary deposition took place many years ago.