Charles Murphy reported about correlation between HTO activity distribution in unsaturated soil layer and atmospheric long-term releases of HTO in the vicinity of Savannah River Site. Tritium Working Group of BIOMASS Programme  performed a model-model intercomparison study of HTO transport from atmosphere to unsaturated soil and evaluated HTO activity distribution in the unsaturated soil layer in the vicinity of permanent atmospheric sources. Tritium Working Group has also reported about such a correlation, however the conclusion was that experimental data sets are needed to confirm this conclusion and also to validate appropriate computer models.