In vascular plants radiocesium and K-40 are mostly free in acqueous solution. The expression of radiocontamination on dry weight basis does not take into account the fact that different plant species, or different parts of a species, may have very different contents in cellulose or lignine. These may mask the actual concentration of the radionuclides in plant water, a fact that may be a serious source of error when the aim is to compare absorption rates. This paper, on the basis of a case study on 10 species in the Carnic Alps (NE-Italy), shows how the expression of radiocontamination on a water basis (difference between fresh and dry weight) may be much more appropriate in certain fields of radioecological research.
