Assessment of tritium uptake by Helianthus annuus culture continuously exposed to HTO at the Semipalatinsk test site

A quantitative assessment of chronic aerial uptake of tritium in the form of HTO by plants under natural conditions of Semipalatinsk test site (former «Degelen» test site) on the example of sunflower culture ( Helianthus Annuus ) is given. During the long-term exposure of Helianthus Annuus , a close positive correlation was established between the values of the specific activity of tissue free water tritium (TFWT) and the volumetric activity of HTO in the air, as well as between the values of the specific activity of organically bound tritium (OBT) and TFWT (the values of Spearman's correlation coefficients were 0.77 and 0.79 respectively). It was found that in chronic tritium air pollution, the values of factor R during the Helianthus Annuus vegetation range from 0.67 to 0.15 with an average value of 0.19. The values of the rate of OBT formation in the leaves of Helianthus Annuus during the exposure were obtained. The rate of formation of tritiated organic matter varied in the range from 0.21 to 0.68 % h-1. The translocation index (TLI) for Helianthus Annuus culture at the end of the exposition was 27.4%. Uneven distribution of TFWT and OBT in the organs of Helianthus Annuus during prolonged aerial absorption of HTO was noted. So, the maximum values of specific activity of TFWT and OBT are established in the above-ground part, especially in leaves. The obtained quantitative parameters and dependences can be used as indicators for biological monitoring of aerial tritium pollution.