Field Studies of HT Behaviour in the Environment: 3. Tritium Deposition and Dynamics in Vegetation

Abstract

The role of vegetation in tritium behaviour was investigated following release of 3.54 TBq HT at a Chalk River experimental field. Results indicated HT oxidation to HTO in soil followed by vegetation uptake and foliar atmospheric water vapour exchange. Vegetation HT deposition velocities measured as tissue-free water tritium (TFWT) in 5 species were 2.3 × 10-8 to 6 × 10-7 m s-1 expressed on a leaf area basis. TFWT loss rates were 5.2 to 8.1% h-1 from about 12 to 48 h after release with low activity rain and 0.42 to 0.56% h-1 from about 48 to 335 h. Initial vegetation organically-bound tritium/TFWT ratios were about 0.05 increasing to 16 after 113 days.