1. Use of mosses for monitoring atmospheric deposition of radionuclides: Possibilities and limitations
Eiliv Steinnes
Department of Chemistry
Norwegian University of Science and Technology
NO-7491 Trondheim
29th Task Force meeting of the UNECE ICP Vegetation, Dubna,

2. As radioactive isotopes of an element do not differ from the stable isotopes of the same element in their chemical properties
- there is no reason why moss samples could not be used to monitor atmospheric deposition of a radionuclide
provided that the moss technique works for the stable element
Thus samples collected within the framework of the European moss survey could be used to monitor deposition of radionuclides as well – episodic or continuous
- provided that a sufficiently large moss sample is available

3. Possible sources of radionuclides in the atmosphere:
Natural processes:
Cosmic rays: 7Be
U and Th decay chains: 210Pb, 210Po, - - -
Anthropogenic processes:
Normal operation of nuclear reactors: 131I, - -
Reactor accidents: 131I, 137Cs, 90Sr, 95Zr-95Nb, 140Ba-140La, - -
Nuclear weapons fallout:
Same as for reactor accidents + 239Pu, 240Pu, 241Am

4. Determination of radionuclides in moss samples: Some examples from the literature.
Svensson, G.K. and Liden, K.: Quantitative accumulation of 95Zr + 95Nb and 140Ba + 140La in carpets of forest moss - a field study. Health Physics 11 (1965) Pioneer paper! Sumerling, T.J.: The use of mosses as indicators of airborne radionuclides near a major nuclear installation. Sci. Total Environ. 35 (1984) 251. Roos, P., Holm, E., Persson, R.B.R, Aarkrog, A., Nielsen, S.P.: Deposition of 210Pb, 137Cs, Pu, 238Pu, and 241Am in the Antarctic Peninsula area. J. Environ. Radioact. 24 (1994) 235.

5. Some additional papers:
Nifontova, M.: Radionuclides in the moss-lichen cover of tundra communities in the Yamal Peninsula. Sci. Total. Environ. 160/161(1995) 749. (137Cs, 90Sr)
Godoy, M. et al.: 137Cs, 226,228Ra, 210Pb and 40K concentrations in Antarctic soil, sediment and selected moss and lichen samples. J. Environ. Radioact. 41 (1998) 33.
Krmar, M., Radnovic, D., Rakic, S., Matavuly, M.: Possible use of terrestrial mosses in detection of atmospheric deposition of 7Be over large areas. J. Environ. Radioact. 95 (2007) 53.

6. Mass yield curve for fission of 235U with thermal neutrons

7. Two very important long-lived fission products: 90Sr and 137Cs
Very few reports in the literature on 90Sr and moss!
No gamma-ray emission: necessary to perform a radiochemical separation and measure the beta activity.
But there are numerous papers on 137Cs in moss!
Can be readily measured by gamma spectrometry –
and a large number of investigators did so.
But did they really know what the results mean?

9. Geographical distribution of 1986 Chernobyl fallout of 137Cs in moss 1990 (right) and in 0-3 cm natural surface soil 1995 (left)

11. E.Gaare and E. Steinnes, unpublished data:

12. 137Cs in moss samples from Belarus collected 2006-2007
Yu. Aleksiayenak et al., J. Environ. Radioact. 117(2013)19

13. The most important fission product radionuclide from human exposure point of view is Iodine -131
131I has a half-life of 8 days, is readily taken up in the body from air and agricultural crops, and concentrates in the thyroid gland
Sampling of 131I in air is normally done by means of air filters (air concentration) or precipitation (deposition)
I am not aware of any report using moss samples to monitor 131I deposition
But there is relevant experience from studies of stable iodine!

14. Halogens in moss in Norway at different distances from the ocean:
Distributions of Cl, Br, and I
along six transects
M.V. Frontasyeva and E. Steinnes:
A. J. Radioanal. Nucl. Chem. 261 (2004) 101
B. Unpublished work

15. Marine transect studies in Norway: Halogens in moss samples (M. V
Marine transect studies in Norway: Halogens in moss samples (M.V. Frontasyeva and E. Steinnes, J. Radioanal. Nucl. Chem. 261 (2004) 101)

16. Marine transect studies in Norway: Halogens in moss samples (M. V
Marine transect studies in Norway: Halogens in moss samples (M.V. Frontasyeva and E. Steinnes, unpublished data)

17. Conclusions:
As stable and radioactive isotopes of an element behave the same way chemically, the use of moss monitoring should be equally applicable to both
There are reports in the literature on successful application of mosses to monitor deposition of naturally occurring as well as artificially produced radionuclides
but sometimes the measured activity did not reflect recent deposition (i.e. 137Cs)
No application reported so far for moss monitoring 131I deposition
Future work should consider existing experience from work on the corresponding stable element